# Scholarly work on the gravitational disruption of a rocky planet by a close pass with another planet?

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note: While the apparently abandoned question Effects of a rogue planet passing between the Earth and the Moon? (inspired by Thundarr the Barbarian) asks for speculation and was answered with it, this question asks for something different. Solar system evolution will likely involve both accumulation of matter into planets and destruction of formed planets by various mechanisms.

I'm interested in finding out if there is scholarly work on the *gravitational disruption of rocky, Earth-like planets due to close passes by, but not collisions with other planets.

An earth-sized rogue planet passing at high speed on a hyperbolic orbit around the sun will generally not have a huge effect on the solar system as a whole. But if it did happen to pass close to earth (say ~1 million miles), it could seriously disrupt the Earth's orbit around the Sun and the Moon's orbit around the Earth. Most perturbations would lead to much more elliptical orbits. These would likely lead to an increase in seasonal extremes and perhaps to larger ocean tides. These changes would then be relatively permanent. There are also questions about the transient effects during the 'near miss'. Would tidal forces from the passing rogue planet induce seismic events on the Earth?

This maybe isn't quite the right forum, but have there been any scientific studies along these lines? It also sounds like a good topic for a science-based novel. Presumably mankind would have years or decades of warning for such an event and would be able to make reasonable predictions about how the environment on Earth will change. The long-term survival of mankind or life in general in the new environment would be a whole other question.

I do see this similar question and that answer does discuss some important points.

 But I was hoping that someone might have investigated this scenario in more detail, perhaps with a specific example. I'm wondering if one can do a back-of-the-envelope calculation of how much delta-V the Earth would get from an Earth-size intruder whizzing past at a distance of, say, 1 million km at a speed of 100 km/s. That might allow the range of perturbed orbits and range of insolation and temperatures, etc. to be calculated.

Scenario: This looks specifically at a near-miss scenario with an Earth-like intruder passing by at a distance of 1,000,000 km at a speed of 100 km/s. This is about three times the distance to the Moon and at about three times Earth's orbital velocity. The 100 km/s seems a reasonable number given the relative velocities of our stellar neighbors, the solar infall/escape velocity, and the likely difference in directions of the Earth and intruder velocities.

First Sighting: It's a pure guess, but maybe the intruder will be first recognized when it's brightness (apparent magnitude) becomes similar to that of Pluto. The difference in absolute magnitude between the Earth and Pluto is (-3.99)-(-0.70) = -3.29. This corresponds to a difference in brightness of 100^(3.29/5) = 20.7. At that distance from the Earth/Sun, the brightness will go as the 4th power of distance, so we should first spot the intruder when it is 20.7^(1/4) = 2.13 times further away than Pluto or about 12.6 billion km. Just approximating with a constant 100 km/s, this means we will get about 4 years of advance warning.

Night Sky: Assuming the intruder approaches from roughly the opposite direction of the Sun, it will be visible in the night sky with a magnitude -3.99+(1/5)log100(1/s^2/(1+s)^2 where s is the distance from Earth in AU. At 0.6 AU (90,000,000 km) it will be roughly as bright as Venus and clearly visible in the night sky. This will occur about 10 days before closest approach. At its closest approach (1 million km), the intruder will appear about 40% larger diameter than the Moon and will be about 7 times brighter, both because of the larger apparent area (0.73/0.52)^2 and higher albedo (0.43/0.12). The intruder will take 5.6 hours to travel the 2 million kilometers across 90 degrees of the night sky while its apparent area goes from 50% to 100% and back to 50% of maximum. A sight worth watching!

Orbital Disturbance (Earth): Assuming the deflections of the Earth and the intruder are small, the delta_V can be calculated as (1/2)GMe/d^2 x (2d/v), where Me is the mass of the Earth or the intruder, d is the distance of closest approach and v is the velocity. The first factor corresponds to the maximum acceleration of the Earth and the second factor to the effective time during which the acceleration is applied. The first factor is 0.000199 m/s^2 and the second factor is 20,000 seconds giving a delta_V of 3.98 m/s. This is 0.00013 of the Earth's orbital speed of 30 km/s. Generally this would change the ellipticity of the orbit slightly and could also change the mean radius if the delta-V were mainly along the direction of the orbit. The orbital energy could change by +/-0.00026 and the mean radius would change the same fraction. Corresponding to a change in the Earth's mean orbital radius, the insolation would change by double that fraction or +/-0.00052. The temperature based on black body radiation would change by the fourth root of the insolation, i.e. +/-0.00013 or +/-0.013% or +/-0.04 degrees C. These changes seem quite minor.

Orbital Disturbance (Moon): The Moon would be more severely affected because its mass is small compared to the intruder, so the acceleration would be roughly twice as large. Also the Moon could be on the 'wrong' side where it would be closer to the intruder by a factor of 2/3. So the acceleration and the delta_V could be higher by a factor of 2/(2/3)^2 = 4.5. The resulting delta_V of 18 m/s on the Moon's orbital velocity of about 1000 m/s is more significant. This could result in a 3.6% change in orbital energy and in radius and a change of 5.4% in period, changing the 28 day period by more than a day. Since tidal effects go as the cube of distance, presumably the lunar tidal ranges would increase (or decrease) by about 11%.

Transient tidal effect: Tidal forces are proportional to mass/distance^3. Ignoring the constant factor, the peak tidal force from the Moon : Sun : Intruder are in the ratio 7.35E22/(3.84E5)^3 : 1.989E30/(1.48E8)^3 : 5.97E24/(1E6)^3 or 1.30 : 0.61 : 5.97. So the maximum tidal force as the intruder swings by will be about three times more that the combined lunar and solar tidal force. Presumably, during the several hours of closest approach, this will raise ocean tides about three times larger than the familiar large spring tides. Coastal areas would experiences tides tens of feet higher than normal much as in a storm surge or tsunami. I suppose it is also possible that some latent earthquakes could also be released by such large tidal forces

(The last time I did a back-of-the-envelope calculation like this, I was wrong by a factor of 10^6. But it certainly elicited some pretty quick responses!)

## Phaeton (hypothetical planet)

Phaeton (alternatively Phaethon or Phaëton) ( / ˈ f eɪ . ə θ ən / Ancient Greek: Φαέθων , romanized: Phaéthōn, pronounced [pʰa.é.tʰɔːn] ) was the hypothetical planet hypothesized by the Titius–Bode law to have existed between the orbits of Mars and Jupiter, the destruction of which supposedly led to the formation of the asteroid belt (including the dwarf planet Ceres). The hypothetical planet was named for Phaethon, the son of the sun god Helios in Greek mythology, who attempted to drive his father's solar chariot for a day with disastrous results and was ultimately destroyed by Zeus. [1] However, his name was used historically for Jupiter itself as well. [2]

## Understanding time

What is time? While most people think of time as a constant, physicist Albert Einstein showed that time is an illusion it is relative — it can vary for different observers depending on your speed through space. To Einstein, time is the "fourth dimension." Space is described as a three-dimensional arena, which provides a traveler with coordinates — such as length, width and height —showing location. Time provides another coordinate — direction — although conventionally, it only moves forward. (Conversely, a new theory asserts that time is "real.")

Einstein's theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Approaching the speed of light, a person inside a spaceship would age much slower than his twin at home. Also, under Einstein's theory of general relativity, gravity can bend time.

Picture a four-dimensional fabric called space-time. When anything that has mass sits on that piece of fabric, it causes a dimple or a bending of space-time. The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity.

Both the general and special relativity theories have been proven with GPS satellite technology that has very accurate timepieces on board. The effects of gravity, as well as the satellites' increased speed above the Earth relative to observers on the ground, make the unadjusted clocks gain 38 microseconds a day. (Engineers make calibrations to account for the difference.)

In a sense, this effect, called time dilation, means astronauts are time travelers, as they return to Earth very, very slightly younger than their identical twins that remain on the planet.

The code used for the thermal analyses is available from the corresponding author upon reasonable request. The PKDGRAV code with granular physics is not yet ready for public release—its details and validation have been presented in many previous studies and are available from the corresponding author upon reasonable request.

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## Comets Are More Dangerous Than We Thought

Y ou know what the plot of a show called CSI: Chicxulub would be? Finding out what killed the dinosaurs, of course. There’s now no question that the scene of the “crime” was the Yucatan Peninsula, in Mexico, where researchers found a massive crater. But what was the murder weapon—an asteroid, or a comet? A trivial difference, you might think, like whether that chocolate on the sidewalk is a smashed-up Snickers or Kit Kat bar. But knowing what sort of thing struck the Earth near the modern town of Chicxulub, clearing the way for mammals to rise up, affects how astronomers evaluate cosmic dangers to our planet.

Now comets, as you may know, come from far away, and spend little time in the inner solar system. Scientists, based on decades of work, consider it to be a minor risk for one to collide with Earth. A new study, however, hints that comets pose a much greater threat than previously thought. 1 Specifically, it’s the long-period, rather than the short-period ones, we have to look out for.

Long-period comets are the least likely to hit our planet because they visit the inner solar system rarely (often just once) and zip by so quickly that the Earth is a tiny target. They originate in the Oort cloud, which extends several light-years from the sun (out to 200,000 times the Earth-sun distance) to the edge of the solar system. Most objects from the Oort cloud will never pass close to the sun, but the few that do can light up our skies. As they warm up and their ices vaporize, they create bright comae and tails. Comet Hale-Bopp was a dazzling sight when it passed through the inner solar system in 1997.

HAILING FROM THE EDGE: Comet Hale-Bopp, as photographed by Philipp Salzgeber, soaring above Pazin, in Croatia, during Easter 1997. Philipp Salzgeber / Wikimedia Commons

These comets are barely gravitationally bound to our star. Galactic forces, such as the combined gravity of unevenly distributed dust and gas clouds, nudge them toward the inner solar system. Short-period (or Jupiter-family) comets, on the other hand, originate in the Kuiper belt, leftover icy material past Neptune’s orbit. On their way into the inner solar system, Neptune’s gravity slingshots them, kicking them outward. As they come back for another pass, they eventually move inward toward Uranus, which, with Saturn, repeats this process, handing objects off to Jupiter, the dominant mass of the solar system (apart from the sun of course). Once a comet is in Jupiter’s clutches, the clock is ticking until it passes too close to Jupiter and is launched out of the solar system. There is a time window in which a comet can collide with Earth, but it is narrow, and impact rates are low.

In the new study, published in Scientific Reports, Harvard astrophysicists Amir Siraj and Avi Loeb (yes, the backer of that controversial hypothesis about aliens) add a wrinkle to this story. They calculate that about 20 percent of long-period comets that pass within Earth’s orbit pass so close to the sun that they are torn apart by tidal forces. This process creates long strands of comet fragments that vastly increase the odds of collision with the Earth.

It’s likely quite common for comets passing close to the sun to be tidally disrupted. Scientists know several groups of comets that are likely tidal fragments. For example, the Kreutz group contains thousands of comets stretched along similar orbits around the sun that are thought to be the remnants of a single giant comet that disrupted a thousand or more years ago.

LOOK AT ME, I’M SHATTERED: This graphic represents the main idea presented in Siraj’s and Loeb’s paper. Sean Raymond / planetplanet.net

From the Chicxulub crater, scientists can tell that the impactor had a diameter of about 12 kilometers. Sediments found beneath the crater contained material usually associated with asteroids. This wouldn’t be surprising. Astronomically speaking, most of the stuff that bashes Earth comes from close by, in the inner part of the asteroid belt, the closest source of loose objects. Indeed, rocks that have been spectrally associated with asteroids dominate our meteorite collections.

These meteorites are so commonplace that we call them “ordinary” chondrites, or stony meteorites. The light reflected from most meteorites looks just like the light we see when we point our telescopes at the inner parts of the asteroid belt. Unstable orbital resonances crisscross this belt, and when an asteroid enters one of these resonances, the planets (usually Jupiter) strongly perturb its orbit, progressively stretching it out until it becomes more and more elliptical, or “eccentric.” This propels asteroids from the inner part of the belt into the realm of the rocky planets, whereas outer-belt asteroids usually end up too close to Jupiter and are thrown out of the solar system entirely. Many close-in asteroids collide with the sun, and a fraction hit the Earth.

It’s now “indisputable” that an asteroid killed the dinosaurs.

A 2007 study proposed that an asteroid associated with the Baptistina family from the inner belt, created by the breakup of a larger object (probably from a collision between asteroids) about 160 million years ago, was the dinosaur killer. 2 A member of that asteroid family supposedly entered an unstable resonance with Jupiter and was kicked into the inner solar system, eventually colliding with Earth 65 million years ago. Yet the sediments left behind after the collision suggest what struck our planet was unlike ordinary chondrite meteorites, and more similar to carbonaceous chondrites, associated with a different class of asteroids (that more often come from the outer belt).

It was thought that the Baptistina family was similar in composition to carbonaceous chondrites, but later work showed that these asteroids were more likely similar to ordinary chondrites. The timing of the Baptistina breakup was also moved much sooner, about 80 million years ago, leaving only a narrow time window for impact. So the Baptistina asteroid theory is no longer a great match to the dinosaur killer. Of course, this doesn’t discount asteroids entirely. Another carbonaceous asteroid could plausibly have done the job.

And that’s precisely what a recent study, published in Science Advances, suggests. 3 Joanna Morgan, a coauthor of the paper, told The Times that it’s now “indisputable” that an asteroid, about 12 kilometers in diameter, killed the dinosaurs. 4 One of the sediment cores recovered from the impact site “contains an extremely well-preserved record of the immediate aftermath of the Chicxulub impact event within the crater that can be disentangled using various geochemical tracers,” the researchers wrote. “By applying these tracers, the effects of asteroid impacts on the biosphere and global environment in the first months to millennia of the Cenozoic Era as well as the fate of the Chicxulub impactor are unraveled in unprecedented detail.”

#### The Inside of a Neutron Star Looks Spookily Familiar

Hot fluids of neutrons that flow without friction, superconductors made of protons, and a solid crust built of exotic atoms—features like these make neutron stars some of the strangest objects we’ve found in the cosmos. READ MORE

Asteroids large enough to kill the dinosaurs have been shown to hit Earth about once every 350 million years. Without accounting for tidal disruption, long-period comets have such low impact probabilities that only one dinosaur killer would have struck Earth since its formation. However, after taking disruption into account, Siraj and Loeb find that the rate of such impacts is about the same as for asteroids. The same process would not boost the impact rate of asteroids, however, because asteroids are too dense to easily disrupt.

Siraj and Loeb’s alternative comet-breakup model requires an incoming comet that has a diameter of at least 40 to 60 kilometers. That’s a monster, about the size of New York City, from the southern tip of Staten Island to the northernmost point of the Bronx (an hour-long drive in the best-case scenario), but not unprecedented, actually about the same size as comet Hale-Bopp. It’s not easy to estimate the sizes of the fragments that a comet that size would produce after it disrupts, but Siraj and Loeb calculate that they will be about 7 kilometers in diameter—the right size for the dinosaur killer.

While provocative, the new model involves considerable uncertainty. All signs point to asteroids being responsible for most impacts in the inner solar system—at least, for the ones we can see. Distributions of crater sizes on Mercury, the moon, and Mars all reflect the size distribution of near-Earth asteroids, suggesting that those are the objects that have crashed down on the planets (including on Earth, where most craters have been buried by geological activity or covered up by erosion).

The comet model also requires that a huge number of fragments be created every time a monster comet disrupts from passing close to the sun. Simulations find that a disrupted body is tidally stretched out into long strands that re-agglomerate into about 10 to 20 objects. 5 These simulations match the natural demonstration of comet Shoemaker-Levy 9’s disruption into about 20 pieces after passing too close to Jupiter, in 1992. It is worth noting that the thousands of comets in the Kreutz family are thought to have been produced through a series of disruption events, rather than a single one. In contrast, the new model needs hundreds to thousands of fragments to be produced in order to increase the collision probability of comets enough to be on the same level as that from asteroids.

BREAKING THE ICE: This train of 21 icy fragments (not all pictured), belonging to comet Shoemaker-Levy 9, stretched across 710,000 miles, three times the distance between Earth and the moon. Wikipedia

Then there’s the element iridium. Extensive geological digs around the world show that, in the aftermath of the impact, a striking layer of iridium-rich material was deposited. Since iridium is so rare on Earth—it’s “highly-siderophile” (iron-loving), so almost all of Earth’s iridium is in the planet’s core—scientists think the stuff came from space. The dinosaur killer must have contained enough to leave a global iridium-rich layer across the whole Earth.

Would a comet contain enough? It depends on what the comet was made of. There aren’t a lot of pieces of comets to test, but the samples returned from Comet Wild-2, courtesy of NASA’s Stardust mission, found that they were very similar to carbonaceous chondrite meteorites, which are known to contain iridium (although somewhat less than ordinary chondrites). Presumably the iridium level of a cometary object wouldn’t be that far off, but it remains to be seen.

This leaves us with a foot in no-man’s land. While the Baptistina source has dried up, carbonaceous asteroids are abundant enough to represent a plausible asteroid impactor, and would match all of the data. That doesn’t completely rule out Siraj and Loeb’s cometary idea, because as tidal disruption increases the number of comets (by producing fragments) it also increases the odds of them crashing into the planets—a twist future calculations on impact probabilities must take into account.

What’s evident, even if one didn’t “off” the dinosaurs, is that it’s safe to assume that comets, shattered into shards by the sun’s gravity, pose what was an underappreciated threat.

Sean Raymond is an American astrophysicist working at the Bordeaux Astrophysical Laboratory in France. He also writes a blog at the interface of science and fiction, and recently published a book of astronomy poems.

1. Siraj, A. & Loeb, A. Breakup of a long-period comet as the origin of the dinosaur extinction. Scientific Reports 11, 3803 (2021).

2. Staff writers. The Baptistina breakup. Astrobiology Magazine (2007).

3. Goderis, S., et al. Globally distributed iridium layer preserved within the Chicxulub impact structure. Science Advances 7, eabe3647 (2021).

4. Blakely, R. Asteroid dust linked to Chicxulub crater confirms dinosaur extinction theory. The Times (2021).

## Gravitational Wave Search Finds Tantalizing New Clue

This illustration shows the NANOGrav project observing cosmic objects called pulsars in an effort detect gravitational waves – ripples in the fabric of space. The project is seeking a low-level gravitational wave background signal that is thought to be present throughout the universe.

An international team of scientists may be close to detecting faint ripples in space-time that fill the universe.

Pairs of black holes billions of times more massive than the Sun may be circling one another, generating ripples in space itself. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has spent more than a decade using ground-based radio telescopes to look for evidence of these space-time ripples created by behemoth black holes. This week, the project announced the detection of a signal that may be attributable to gravitational waves, though members aren't quite ready to claim success.

Gravitational waves were first theorized by Albert Einstein in 1916, but they weren't directly detected until nearly a century later. Einstein showed that rather than being a rigid backdrop for the universe, space is a flexible fabric that is warped and curved by massive objects and inextricably linked with time. In 2015, a collaboration between the U.S.-based Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer in Europe announced the first direct detection of gravitational waves: They were emanating from two black holes - each with a mass about 30 times greater than the Sun - circling one another and merging.

In a new paper published in the January 2021 issue of the Astrophysical Journal Supplements, the NANOGrav project reports the detection of unexplained fluctuations, consistent with the effects of gravitational waves, in the timing of 45 pulsars spread across the sky and measured over a span of 12 1/2 years.

Pulsars are dense nuggets of material left over after a star explodes as a supernova. As seen from Earth, pulsars appear to blink on and off. In reality, the light comes from two steady beams emanating from opposite sides of the pulsar as it spins, like a lighthouse. If gravitational waves pass between a pulsar and Earth, the subtle stretching and squeezing of space-time would appear to introduce a small deviation in the pulsar's otherwise regular timing. But this effect is subtle, and more than a dozen other factors are known to influence pulsar timing as well. A major part of the work done by NANOGrav is to subtract those factors from the timing data for each pulsar before looking for signs of gravitational waves.

LIGO and Virgo detect gravitational waves from individual pairs of black holes (or other dense objects called neutron stars). By contrast, NANOGrav is looking for a persistent gravitational wave "background," or the noiselike combination of waves created over billions of years by countless pairs of supermassive black holes orbiting one another across the universe. These objects produce gravitational waves with much longer wave lengths than those detected by LIGO and Virgo - so long that it might take years for a single wave to pass by a stationary detector. So while LIGO and Virgo can detect thousands of waves per second, NANOGrav's quest requires years of data.

As tantalizing as the latest finding is, the NANOGrav team isn't ready to claim they've found evidence of a gravitational wave background. Why the hesitation? In order to confirm direct detection of a signature from gravitational waves, NANOGrav's researchers will have to find a distinctive pattern in the signals between individual pulsars. According to Einstein's theory of general relativity, the effect of the gravitational wave background should influence the timing of the pulsars slightly differently based on their positions relative to one another.

At this point, the signal is too weak for such a pattern to be distinguishable. Boosting the signal will require NANOGrav to expand its dataset to include more pulsars studied for even longer lengths of time, which will increase the array's sensitivity. NANOGrav is also pooling its data with those from other pulsar timing array experiments in a joint effort by the International Pulsar Timing Array, a collaboration of researchers using the world's largest radio telescopes.

"Trying to detect gravitational waves with a pulsar timing array requires patience," said Scott Ransom with the National Radio Astronomy Observatory and the current chairperson of NANOGrav. "We're currently analyzing over a dozen years of data, but a definitive detection will likely take a couple more. It's great that these new results are exactly what we would expect to see as we creep closer to a detection."

## What Makes A Planet? Lessons Learned 14 Years After Pluto’s Demotion

Although we now believe we understand how the Sun and our solar system formed, this early view is an . [+] illustration only. When it comes to what we see today, all we have left are the survivors. What was around in the early stages was far more plentiful than what survives today.

JOHNS HOPKINS UNIVERSITY APPLIED PHYSICS LABORATORY/SOUTHWEST RESEARCH INSTITUTE (JHUAPL/SWRI)

In 2006, the last planet in our Solar System suffered an unforgettable insult, as Pluto — known for generations as our ninth planet — was demoted to the status of dwarf planet. A series of discoveries from ground-based and space-based telescopes had revealed much of what was out there beyond Neptune, and Pluto fit in much better as a standard member of these Kuiper belt objects than it did with any of the other eight planets. As a result, the International Astronomical Union’s new definition demoted Pluto to the status of “dwarf planet,” even as the New Horizons mission was already on its way.

In the 14 years since, however, we’ve made an amazing slew of discoveries. We’ve continued to find, identify, and characterize objects in the Kuiper belt. New Horizons visited Pluto and revealed this outer world as never before. Additionally, missions like NASA’s Kepler and TESS have found thousands of new exoplanets, while independent observations have discovered an interstellar population of long-suspected rogue planets: planets without parent stars. It’s still a controversial subject today, but here’s what we know about planets in our Universe.

Star-forming regions, like this one in the Carina Nebula, can form a huge variety of stellar masses . [+] if they can collapse quickly enough. Inside the 'caterpillar' is a proto-star, but it is in the final stages of formation, as external radiation evaporates the gas away more quickly than the newly-forming star can accrue it. There should also be many young protoplanets inside.

NASA, ESA, N. Smith, University of California, Berkeley, and The Hubble Heritage Team. STScI/AURA

The first thing we all need to understand is where planets comes from. Whenever you have a large cloud of molecular gas in space, it has the potential to become a veritable factory for forming new planets. The way we’ve most often conceived of it is the way we think it happened for our Solar System long ago:

• a cool cloud of gas collapses under its own gravity,
• which fragments into various clumps,
• the largest, densest, highest-mass clumps lead to stars,
• which ignite nuclear fusion, form a circumstellar disk, and that disk gets its own gravitational imperfections in it, which lead to planets and, sometimes, multi-star systems.

### Mars, Venus And A ‘Super Solstice Strawberry Moon’ Sparkle In Twilight: What You Can See In The Night Sky This Week

Over the past few years, telescopes that specialize in long-wavelength observations, such as infrared or microwave/radio bands, have revealed these planet forming “gaps” in these protoplanetary disks for the first time. Owing to these groundbreaking astronomical observations, we can actually watch the process of planets forming in action.

20 new protoplanetary disks, as imaged by the Disk Substructures at High Angular Resolution Project . [+] (DSHARP) collaboration, showcasing what newly-forming planetary systems look like. The gaps in the disk are likely the locations of newly-forming planets, with the largest gaps likely corresponding to the most massive proto-planets.

S. M. Andrews et al. and the DSHARP collaboration, arXiv:1812.04040

At a later stage, we can observe the mature planetary systems that wind up forming around these stars. The three major methods by which we observe these exoplanetary systems are:

1. the transit method, where planets pass periodically between a distant star and our telescopes,
2. the stellar wobble method, where a planet’s gravitational pull on its star causes a periodic redshift/blueshift to the star’s light,
3. and direct imaging, which can reveal bright planets that are well-separated from their parent star.

What we’ve learned is absolutely fascinating. Planets come in a wide variety of sizes, from smaller than Mars and Mercury to larger than the size of Jupiter, and orbit at a wide variety of distances. Giant and rocky planets can coexist within the same solar system at any distance they like. Our Solar System, with inner, rocky planets and outer, gas giant planets, is not even the most common option.

Today, as shown in figure 10, we know of over 3,500 confirmed exoplanets, with more than 2,500 of . [+] those found in the Kepler data. These planets range in size from larger than Jupiter to smaller than Earth, with most of them in between the size of Earth and Neptune.

NASA/Ames Research Center/Jessie Dotson and Wendy Stenzel

We’ve learned that the most common mass/size combination for a planet is intermediate between Venus/Earth and Uranus/Neptune: a class of worlds that was given the name “super-Earth” early on. For years in the early 2010s, one question that astronomers wondered about was, “why don’t we have a super-Earth in our Solar System?”

But it turned out that was the wrong question, as better data revealed. NASA’s Kepler mission was able to reveal the radius and orbital parameters of thousands of new exoplanets, but follow-up observations (mostly using the stellar wobble method) were required to learn the masses of those exoplanets. When we plotted them all out, we learned something fascinating.

Instead of the artificial class of “super-Earth” that we had invented, there were only three classes of planet:

1. terrestrial planets, which were rocky and had only thin atmospheres,
2. Neptune-like giants, which had substantial hydrogen/helium envelopes,
3. and Jupiter-like giants, which were gas dominated but also exhibited gravitational self-compression.

When we map out the planets that we've observed and measured both their physical mass and their . [+] physical radius, we find that they fall into only three categories: terrestrial-like, Neptunian, or Jovian. Anything that is heavier than a Jovian world ignites fusion in its core and becomes a star. There is some uncertainty as to the borders of these categories.

That’s it, at least for planets that orbit around stars. But do you have to be orbiting around a star to be considered a planet?

Not necessarily. In theory, there are two ways to have what we call a “rogue planet,” or a planet without a parent star. You can either:

• form a planet as part of a solar system, and then have gravitational interactions eject it,
• or fail to gather enough mass to form a star in a portion of a gas cloud, forming a planet that never had a parent star.

We suspect that, for every solar system like ours that forms, one Uranus-sized world and five-to-ten terrestrial worlds are formed and ejected, sent out into interstellar space by gravitational interactions. Over the 14 years since Pluto’s demotion, we’ve actually found some of these rogue planets: through either microlensing (where they pass between the line-of-sight to a star, temporarily brightening it) or, when we get the luckiest, by direct infrared observations.

The candidate rogue planet CFBDSIR2149, as imaged in the infrared, is a gas giant world that emits . [+] infrared light but has no star or other gravitational mass that it orbits. It is unknown whether this is an ejected planet from a previous solar system, or whether this is a planet that was formed without a parent star at all.

However, the science of microlensing is still in its infancy, but is about to get tremendously better with the next generation of telescopes, and the Vera Rubin Observatory in particular. The rogue planets that are out there are beyond the reach of direct imaging, but should be floating throughout the galaxy. When they pass through the line-of-sight that connects our telescopes to a star, they should cause a characteristic, brief brightening, which should allow us to begin estimating how many of them (and what masses they have) are out there.

In theory, the ejected rogue planets are the vast minority the overwhelming majority of them should come from the “failed star formation” scenario. According to a 2012 study, for every star that formed in our galaxy, we should have somewhere between 100 and 100,000 of these rogue planets that form as well. They are forever destined to wander, parentless, through interstellar space.

When a massive objects passes between our line-of-sight and a distant, luminous source, there's a . [+] brightening and dimming that will occur based only on the geometry and the mass of the intervening (lensing) object. Through this mechanism, we've been able to estimate the population of masses in our galaxy, and find no evidence for a mass gap, but rather see a number of interesting candidates in that mass range. We do not know the nature or origin of these objects, just their masses.

NASA'S EXOPLANET SCIENCE INSTITUTE / JPL-CALTECH / IPAC

At the same time, our visit to Pluto with the New Horizons spacecraft has revealed to us exactly what this distant dwarf planet is like. The world is geologically fascinating, with its own atmosphere complete with hazes, ice mountains and plains that float atop a thick liquid ocean, snowy weather patterns, and a complex and varied surface that evolves over time. In many ways, it’s more complex and has more potential for interesting chemical reactions — possibly even including biological activity — than bona fide planets such as Mercury.

Its lunar system, we can now conclude, was likely formed as the result of a giant impact, with large Charon and the four smaller, outer moons orbiting in resonance with one another. It is the largest object in the Kuiper belt now that Eris has been confirmed to be 1% smaller and Triton, the former largest body, has been captured by Neptune. In terms of size, Pluto truly is the current king of the Kuiper belt.

Pluto and its moon Charon image composite stitched together from many New Horizons images. New . [+] Horizons has been the most successful mission ever sent into the Kuiper belt, and will travel beyond it entirely at some point in the next decade or two.

NASA / New Horizons / LORRI

Nevertheless, it’s quite clear that Pluto is very different in terms of physical properties, formation history, and location than all of the other planets. It has the same composition as other Kuiper belt objects, with a low density and an atmosphere that’s created by volatiles interacting with solar radiation. It does not dominate its orbit, but rather is extremely low in mass and small in size. It has far more in common with Eris, Makemake, Haumea, and the other large trans-Neptunian objects than any of the planets.

In fact, it only meets two of the three criteria that the International Astronomical Union set forth in their definition of a planet (in our Solar System). They said that a planet must:

1. have enough gravity to pull itself into hydrostatic equilibrium: spherical if you’re not spinning, spheroidal if you are,
2. orbit the Sun and no other body (i.e., not be a moon),
3. and must clear its orbit of other massive bodies on the timescale of the lifetime of the Sun.

Pluto doesn’t come close to meeting the third criteria, and so only those who go by geophysical definitions — where location and formation history are ignored — still consider Pluto a planet in any way.

When you rank all the moons, small planets, and dwarf planets in our Solar System, you can see that . [+] many of the largest non-planetary objects are moons, with a few being Kuiper belt objects. Pluto is clearly different than the planetary worlds in terms of mass, size, density, and composition, as well as location.

MONTAGE BY EMILY LAKDAWALLA. DATA FROM NASA / JPL, JHUAPL/SWRI, SSI, AND UCLA / MPS / DLR / IDA, PROCESSED BY GORDAN UGARKOVIC, TED STRYK, BJORN JONSSON, ROMAN TKACHENKO, AND EMILY LAKDAWALLA

With the recent explosion in our knowledge of exoplanetary systems, astronomers began to wonder whether there was a way to extend our definition of “planet” to other solar systems. It isn’t possible to measure the shape of a planet that orbits another star, as they only appear point-like from our perspective. It also isn’t possible to determine whether a potential planet has cleared its orbit or not, as the smaller bodies that might orbit a distant star cannot be observed.

Fortunately, astronomer Jean-Luc Margot came up with a very clever method that relied only on measuring an exoplanet’s mass and orbital properties to determine whether it met the IAU’s criteria or not. Gravity works the same way everywhere in the Universe and in the galaxy, so for any particular distance, there’s a minimum mass that will clear its orbit on the timescale of a star’s lifetime. The 8 planets of the Solar System are all in Pluto is clearly out. Interestingly enough, if the Earth-Moon system were replaced with our Moon alone, it would be right on the border of what constitutes (or doesn’t constitute) a planet.

If you demand that an exoplanet meet the same planetary criteria that the International Astronomical . [+] Union defined for our solar system, you can determine what those relations are by measuring the exoplanet's mass and orbital distance alone. The lines represent what is (above) and isn't (below) a planet, by these criteria.

Margot (2015), via http://arxiv.org/abs/1507.06300

When we put all of this information together, a fascinating perspective emerges. Pluto, from a purely geophysical perspective, is a fascinating world in its own right. There are likely

10 or so Pluto-like objects in every solar system like our own out there, but none of them will meet the criteria for planethood that we’ve set out, as none of them will dominate their orbits sufficiently. Planets themselves only come in three varieties: terrestrial worlds, Neptune-like giants, and Jupiter-like giants that exhibit self-compression. Within a solar system, nothing else meets the standards we’ve set forth.

But outside of a solar system, trillions upon trillions of rogue planets — which themselves do not meet the definition of planet — wander through interstellar space. We don’t know how many there are, what their mass distributions look like, or just what fraction of them were once “true planets” as part of a solar system versus the ones that were born without a parent star at all.

Pluto, from the perspective of an astronomer, was never a planet at all. But the Universe, no matter how you classify the objects within it, is all the richer on account of the rocky and icy bodies present within it.

## Real Tatooines? Evidence Found of Rocky Planet Formation Around Double Star

Astronomers have found evidence of shattered asteroids orbiting a pair of stars, a strong new sign that rocky worlds with twin suns like Luke Skywalker's fictional home world Tatooine are possible.

This finding also suggests that rocky planets may be able to survive the deaths of their stars, the new study's researchers said.

Although Earth orbits a single star, nearly half of sun-like stars are in binary systems, which are made up of a pair of stars orbiting each other. In fact, there are many three-star systems, and even some that are home to up to seven stars. [Tatooine Found? &ndash Planet with Twin Suns Discovered (Video)]

Worlds that orbit binary stars, like Tatooine from the "Star Wars" universe, are known as circumbinary planets. In 2011, researchers discovered the first real-life alien world around two stars, Kepler-16b: a gas giant orbiting the star Kepler-16 about 200 light-years from Earth.

So far, all known circumbinary planets are gas giants, similar to Jupiter. Scientists have debated whether rocky circumbinary planets like Tatooine are possible.

"Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets," Jay Farihi, the study's lead author and an astrophysicist at University College London, said in a statement.The research team discovered the remains of shattered asteroids orbiting a binary system, which suggests that rocky planets might exist there, Farihi said. Moreover, these findings suggest that circumbinary planetary systems with rocky worlds can even "survive the death of one of the stars," said study co-author Boris Gänsicke, an astrophysicist at the University of Warwick in England.

The astronomers examined a system called SDSS 1557 located about 1,000 light-years from Earth. They initially thought it contained only a white dwarf, which is the dim burnt-out remnant of a star. The sun and more than 90 percent of all stars in the Milky Way will end up as white dwarfs, which have masses 40 to 90 percent that of the sun but only about the same diameter as Earth.

Using the Gemini Observatory South telescope and the European Southern Observatory Very Large Telescope, both located in Chile, the researchers analyzed the spectrum of light from SDSS 1557. The wavelength of light seen from a star can yield insights on its chemistry and surroundings.

The researchers detected excessive infrared light, suggesting that SDSS 1557 possessed a disk of planetary debris loaded with silicon and magnesium about 1.3 million miles (2.1 million kilometers) from the white dwarf. Moreover, they calculated that about 110 billion tons (100 billion metric tons) of dust has rained onto the white dwarf since its discovery in 2010, equal to the remains of an asteroid-size chunk of rock, or planetesimal, at least 2.5 miles (4 km) in diameter.

"Fairly recently, a rocky planetesimal got too close to the white dwarf, torn apart by its enormous gravity, and formed the debris ring we see," Gänsicke told Space.com.

But then, study co-author Steven Parsons at the University of Sheffield in England noticed that the white dwarf was regularly wobbling back and forth. "This immediately implied that we were not looking at a single white dwarf, but a white dwarf with a companion star," Gänsicke said.

The white dwarf moved at speeds of about 89,500 mph (144,000 km/h). The strength of the gravitational pull causing this wobbling was too much for the companion to be a planet, but too little for it to be a proper star, Gänsicke said.

Instead, the researchers suggest the white dwarf's companion is a brown dwarf equal in mass to about 65 Jupiters. "Brown dwarfs are halfway between stars and giant gas planets," Gänsicke said. "They are too small to start hydrogen burning, the process that powers the sun and most other stars. However, they do manage to burn deuterium, another flavor of hydrogen, and so differ from planets that do not produce any energy by themselves." [Brown Dwarfs: Strange Failed Stars of the Universe Explained (Infographic)]

In the solar system, the asteroid belt holds leftover building blocks from the formation of Earth and the other rocky planets. "With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are made in double star systems," Farihi said in the statement.

"We weren't even remotely thinking about the possibility that we could find a circumbinary planetary system," Gänsicke said. "Now that we found the first one, we will have a closer look at other white dwarfs in close binaries to see if this is a one-off, or if these systems are more common."

The researchers suggest this binary system had a turbulent past. They calculated that the two members of the binary system were once significantly farther from each other than they are today. However, when the progenitor of the white dwarf finished burning its hydrogen fuel, it swelled to become a red giant star, "engulfing the brown dwarf and drawing it closer towards it because of the friction in its gas envelope," Gänsicke said.

Now the two members of the binary system "are about 300,000 miles [482,000 km] apart," Gänsicke said. "That's not much more than the distance between the Earth and the moon."That rocky debris orbits this binary system is a hint that rocky planets might as well, and that such planetary systems may have survived the death of at least one member of a binary system: "SDSS 1557 adds another dimension to the possible architectures in which planetary systems can exist," Gänsicke said.

Although these new findings suggest that rocky planets are forming or have formed around SDSS 1557, "detecting planets that are likely orbiting this binary further out is going to be very, very difficult," Gänsicke said. One common method used to find planets &mdash looking for tugs on the star by a planet's gravitational pull &mdash "is not really possible here because the white dwarf is so faint," he explained. "The other method, looking for periodic dimming as a planet crosses the star, might in principle work, but only if the orbit of such a planet is finely aligned with our line-of-sight towards the system, which is unlikely, and even then, it might take years or decades of data."

"However, there is still a lot we can learn about the planetary system at SDSS1557," Gänsicke added. The researchers plan to use the Hubble Space Telescope to analyze ultraviolet light from the white dwarf, "from which we will be able to measure very accurately the chemical composition of the planetesimal that got shredded," he said. "That will tell us if it was similar to asteroids in the solar system, maybe if it had some water left, or maybe if it had a much more exotic chemical setup. And once the James Webb Space Telescope is launched, we can study the composition and size of the dust grains."

"Besides that, there is a lot of theoretical work to be done &mdash all the models for evolved planetary systems around white dwarfs were so far developed for single white dwarfs," Gänsicke said. "Now we need to ask, 'How does a planetesimal get flung near the white dwarf within the binary? How did the disruption occur? How did the dust we see now get to its location?'"

The scientists detailed their findings online yesterday (Feb. 27) in the journal Nature Astronomy.

## Contents

December 2012 marked the conclusion of a bʼakʼtun—a time period in the Mesoamerican Long Count calendar, used in Central America prior to the arrival of Europeans. Although the Long Count was most likely invented by the Olmec, [14] it has become closely associated with the Maya civilization, whose classic period lasted from 250 to 900 AD. [15] The writing system of the classic Maya has been substantially deciphered, [16] meaning that a corpus of their written and inscribed material has survived from before the European conquest.

Unlike the 260-day tzolkʼin still used today among the Maya, the Long Count was linear rather than cyclical, and kept time roughly in units of 20: 20 days made a uinal, 18 uinals (360 days) made a tun, 20 tuns made a kʼatun, and 20 kʼatuns (144,000 days or roughly 394 years) made up a bʼakʼtun. Thus, the Maya date of 8.3.2.10.15 represents 8 bʼakʼtuns, 3 kʼatuns, 2 tuns, 10 uinals and 15 days. [17] [18]

### Apocalypse Edit

There is a strong tradition of "world ages" in Maya literature, but the record has been distorted, leaving several possibilities open to interpretation. [19] According to the Popol Vuh, a compilation of the creation accounts of the Kʼicheʼ Maya of the Colonial-era highlands, we are living in the fourth world. [20] The Popol Vuh describes the gods first creating three failed worlds, followed by a successful fourth world in which humanity was placed. In the Maya Long Count, the previous world ended after 13 bʼakʼtuns, or roughly 5,125 years. [21] [Note a] The Long Count's "zero date" [Note b] [Note c] was set at a point in the past marking the end of the third world and the beginning of the current one, which corresponds to 11 August 3114 BC in the proleptic Gregorian calendar. [22] [2] This means that the fourth world reached the end of its 13th bʼakʼtun, or Maya date 13.0.0.0.0, on 21 December 2012. In 1957, Mayanist and astronomer Maud Worcester Makemson wrote that "the completion of a Great Period of 13 bʼakʼtuns would have been of the utmost significance to the Maya." [23] In 1966, Michael D. Coe wrote in The Maya that "there is a suggestion . that Armageddon would overtake the degenerate peoples of the world and all creation on the final day of the 13th [bʼakʼtun]. Thus . our present universe [would] be annihilated . when the Great Cycle of the Long Count reaches completion." [24] [Note e]

### Objections Edit

Coe's interpretation was repeated by other scholars through the early 1990s. [25] In contrast, later researchers said that, while the end of the 13th bʼakʼtun would perhaps be a cause for celebration, [8] it did not mark the end of the calendar. [26] "There is nothing in the Maya or Aztec or ancient Mesoamerican prophecy to suggest that they prophesied a sudden or major change of any sort in 2012," said Mayanist scholar Mark Van Stone. "The notion of a 'Great Cycle' coming to an end is completely a modern invention." [27] In 1990, Mayanist scholars Linda Schele and David Freidel argued that the Maya "did not conceive this to be the end of creation, as many have suggested". [28] Susan Milbrath, curator of Latin American Art and Archaeology at the Florida Museum of Natural History, stated that, "We have no record or knowledge that [the Maya] would think the world would come to an end" in 2012. [8] Sandra Noble, executive director of the Foundation for the Advancement of Mesoamerican Studies, said, "For the ancient Maya, it was a huge celebration to make it to the end of a whole cycle," and, "The 2012 phenomenon is a complete fabrication and a chance for a lot of people to cash in." [8] "There will be another cycle," said E. Wyllys Andrews V, director of the Tulane University Middle American Research Institute. "We know the Maya thought there was one before this, and that implies they were comfortable with the idea of another one after this." [29] Commenting on the new calendar found at Xultún, one archaeologist said "The ancient Maya predicted the world would continue—that 7,000 years from now, things would be exactly like this. We keep looking for endings. The Maya were looking for a guarantee that nothing would change. It's an entirely different mindset." [30]

Several prominent individuals representing Maya of Guatemala decried the suggestion that the world would end with the 13th bʼakʼtun. Ricardo Cajas, president of the Colectivo de Organizaciones Indígenas de Guatemala, said the date did not represent an end of humanity but that the new cycle "supposes changes in human consciousness". Martín Sacalxot, of the office of Guatemala's Human Rights Ombudsman (Procurador de los Derechos Humanos), said that the end of the calendar has nothing to do with the end of the world or the year 2012. [31]

### Prior associations Edit

The European association of the Maya with eschatology dates back to the time of Christopher Columbus, who was compiling a work called Libro de las profecías during the voyage in 1502 when he first heard about the "Maia" on Guanaja, an island off the north coast of Honduras. [32] Influenced by the writings of Bishop Pierre d'Ailly, Columbus believed that his discovery of "most distant" lands (and, by extension, the Maya themselves) was prophesied and would bring about the Apocalypse. End-times fears were widespread during the early years of the Spanish Conquest as the result of popular astrological predictions in Europe of a second Great Flood for the year 1524. [32]

In the 1900s, German scholar Ernst Förstemann interpreted the last page of the Dresden Codex as a representation of the end of the world in a cataclysmic flood. He made reference to the destruction of the world and an apocalypse, though he made no reference to the 13th bʼakʼtun or 2012 and it was not clear that he was referring to a future event. [33] His ideas were repeated by archaeologist Sylvanus Morley, [34] who directly paraphrased Förstemann and added his own embellishments, writing, "Finally, on the last page of the manuscript, is depicted the Destruction of the World . Here, indeed, is portrayed with a graphic touch the final all-engulfing cataclysm" in the form of a great flood. These comments were later repeated in Morley's book, The Ancient Maya, the first edition of which was published in 1946. [32]

It is not certain what significance the classic Maya gave to the 13th bʼakʼtun. [35] Most classic Maya inscriptions are strictly historical and do not make any prophetic declarations. [35] Two items in the Maya classical corpus, however, do mention the end of the 13th bʼakʼtun: Tortuguero Monument 6 and La Corona Hieroglyphic Stairway 12.

### Tortuguero Edit

The Tortuguero site, which lies in southernmost Tabasco, Mexico, dates from the 7th century AD and consists of a series of inscriptions mostly in honor of the contemporary ruler Bahlam Ahau. One inscription, known as Tortuguero Monument 6, is the only inscription known to refer to bʼakʼtun 13 in any detail. It has been partially defaced Sven Gronemeyer and Barbara MacLeod have given this translation:

tzuhtzjo꞉m uy-u꞉xlaju꞉n pik
chan ajaw u꞉x uni꞉w
uhto꞉m il[?]
yeʼni/ye꞉n bolon yokte'
ta chak joyaj

It will be completed the 13th bʼakʼtun.
It is 4 Ajaw 3 Kʼankʼin
and it will happen a 'seeingʼ[?].
It is the display of Bʼolon-Yokte'
in a great "investiture". [36]

Very little is known about the god Bʼolon Yokteʼ. According to an article by Mayanists Markus Eberl and Christian Prager in British Anthropological Reports, his name is composed of the elements "nine", ʼOK-teʼ (the meaning of which is unknown), and "god". Confusion in classical period inscriptions suggests that the name was already ancient and unfamiliar to contemporary scribes. [37] He also appears in inscriptions from Palenque, Usumacinta, and La Mar as a god of war, conflict, and the underworld. In one stele he is portrayed with a rope tied around his neck, and in another with an incense bag, together signifying a sacrifice to end a cycle of years. [38]

Based on observations of modern Maya rituals, Gronemeyer and MacLeod claim that the stela refers to a celebration in which a person portraying Bolon Yokteʼ Kʼuh was wrapped in ceremonial garments and paraded around the site. [39] [40] They note that the association of Bolon Yokteʼ Kʼuh with bʼakʼtun 13 appears to be so important on this inscription that it supersedes more typical celebrations such as "erection of stelae, scattering of incense" and so forth. Furthermore, they assert that this event was indeed planned for 2012 and not the 7th century. [41] Mayanist scholar Stephen Houston contests this view by arguing that future dates on Maya inscriptions were simply meant to draw parallels with contemporary events, and that the words on the stela describe a contemporary rather than a future scene. [42]

### La Corona Edit

In April–May 2012, a team of archaeologists unearthed a previously unknown inscription on a stairway at the La Corona site in Guatemala. The inscription, on what is known as Hieroglyphic Stairway 12, describes the establishment of a royal court in Calakmul in 635 AD, and compares the then-recent completion of 13 kʼatuns with the future completion of the 13th bʼakʼtun. It contains no speculation or prophecy as to what the scribes believed would happen at that time. [43]

### Dates beyond bʼakʼtun 13 Edit

Maya inscriptions occasionally mention predicted future events or commemorations that would occur on dates far beyond the completion of the 13th bʼakʼtun. Most of these are in the form of "distance dates" Long Count dates together with an additional number, known as a Distance Number, which when added to them makes a future date. On the west panel at the Temple of Inscriptions in Palenque, a section of text projects forward to the 80th 52-year Calendar Round from the coronation of the ruler Kʼinich Janaabʼ Pakal. Pakal's accession occurred on 9.9.2.4.8, equivalent to 27 July 615 AD in the proleptic Gregorian calendar. The inscription begins with Pakal's birthdate of 9.8.9.13.0 (24 March, 603 AD Gregorian ) and then adds the Distance Number 10.11.10.5.8 to it, [44] arriving at a date of 21 October 4772 AD, more than 4,000 years after Pakal's time. [27] [44] [45]

Another example is Stela 1 at Coba which marks the date of creation as 13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.0.0.0.0 , or nineteen units above the bʼakʼtun. According to Linda Schele, these 13s represent "the starting point of a huge odometer of time", with each acting as a zero and resetting to 1 as the numbers increase. [28] [Note c] Thus this inscription anticipates the current universe lasting at least 20 21 ×13×360 days, [46] or roughly 2.687×10 28 years a time span equal to 2 quintillion times the age of the universe as determined by cosmologists. Others have suggested, however, that this date marks creation as having occurred after that time span. [46] [47]

In 2012, researchers announced the discovery of a series of Maya astronomical tables in Xultún, Guatemala which plot the movements of the Moon and other astronomical bodies over the course of 17 bʼakʼtuns. [30] [48] [49]

Many assertions about the year 2012 form part of Mayanism, a non-codified collection of New Age beliefs about ancient Maya wisdom and spirituality. [50] The term is distinct from "Mayanist," used to refer to an academic scholar of the Maya. [51] [52] Archaeoastronomer Anthony Aveni says that while the idea of "balancing the cosmos" was prominent in ancient Maya literature, the 2012 phenomenon did not draw from those traditions. Instead, it was bound up with American concepts such as the New Age movement, 2012 millenarianism, and the belief in secret knowledge from distant times and places. [53] Themes found in 2012 literature included "suspicion towards mainstream Western culture", the idea of spiritual evolution, and the possibility of leading the world into the New Age by individual example or by a group's joined consciousness. The general intent of this literature was not to warn of impending doom but "to foster counter-cultural sympathies and eventually socio-political and 'spiritual' activism". [54] Aveni, who has studied New Age and search for extraterrestrial intelligence (SETI) communities, describes 2012 narratives as the product of a "disconnected" society: "Unable to find spiritual answers to life's big questions within ourselves, we turn outward to imagined entities that lie far off in space or time—entities that just might be in possession of superior knowledge." [55]

### Origins Edit

In 1975, the ending of bʼakʼtun 13 became the subject of speculation by several New Age authors, who asserted it would correspond with a global "transformation of consciousness". In Mexico Mystique: The Coming Sixth Age of Consciousness, Frank Waters tied Coe's original date of 24 December 2011 [Note e] to astrology and the prophecies of the Hopi, [56] while both José Argüelles (in The Transformative Vision) [57] and Terence McKenna (in The Invisible Landscape) [58] [59] discussed the significance of the year 2012 without mentioning a specific day. Some research [60] suggests that both Argüelles and McKenna were heavily influenced in this regard by the Mayanism of American author William S. Burroughs, who first portrayed the end of the Mayan Long Count as an apocalyptic shift of human consciousness in 1960's The Exterminator. [61]

In 1983, with the publication of Robert J. Sharer's revised table of date correlations in the 4th edition of Morley's The Ancient Maya, [Note e] each became convinced that 21 December 2012 had significant meaning. By 1987, the year in which he organized the Harmonic Convergence event, Argüelles was using the date 21 December 2012 in The Mayan Factor: Path Beyond Technology. [62] [63] He claimed that on 13 August 3113 BC the Earth began a passage through a "galactic synchronization beam" that emanated from the center of our galaxy, that it would pass through this beam during a period of 5200 tuns (Maya cycles of 360 days each), and that this beam would result in "total synchronization" and "galactic entrainment" of individuals "plugged into the Earth's electromagnetic battery" by 13.0.0.0.0 (21 December 2012). He believed that the Maya aligned their calendar to correspond to this phenomenon. [64] Anthony Aveni has dismissed all of these ideas. [65]

In 2001, Robert Bast wrote the first online articles regarding the possibility of a doomsday in 2012. [66] In 2006, author Daniel Pinchbeck popularized New Age concepts about this date in his book 2012: The Return of Quetzalcoatl, linking bʼakʼtun 13 to beliefs in crop circles, alien abduction, and personal revelations based on the use of hallucinogenic drugs and mediumship. [67] [68] Pinchbeck claims to discern a "growing realization that materialism and the rational, empirical worldview that comes with it has reached its expiration date . [w]e're on the verge of transitioning to a dispensation of consciousness that's more intuitive, mystical and shamanic". [6]

### Galactic alignment Edit

There is no significant astronomical event tied to the Long Count's start date. [69] However, its supposed end date was tied to astronomical phenomena by esoteric, fringe, and New Age literature that placed great significance on astrology, especially astrological interpretations associated with the phenomenon of axial precession. [70] [71] Chief among these ideas is the astrological concept of a "galactic alignment".

#### Precession Edit

In the Solar System, the planets and the Sun lie roughly within the same flat plane, known as the plane of the ecliptic. From our perspective on Earth, the ecliptic is the path taken by the Sun across the sky over the course of the year. The twelve constellations that line the ecliptic are known as the zodiacal constellations, and, annually, the Sun passes through all of them in turn. Additionally, over time, the Sun's annual cycle appears to recede very slowly backward by one degree every 72 years, or by one constellation approximately every 2,160 years. This backward movement, called "precession", is due to a slight wobble in the Earth's axis as it spins, and can be compared to the way a spinning top wobbles as it slows down. [72] Over the course of 25,800 years, a period often called a Great Year, the Sun's path completes a full, 360-degree backward rotation through the zodiac. [72] In Western astrological traditions, precession is measured from the March equinox, one of the two annual points at which the Sun is exactly halfway between its lowest and highest points in the sky. At the end of the 20th century and beginning of the 21st, the Sun's March equinox position was in the constellation Pisces moving back into Aquarius. This signaled the end of one astrological age (the Age of Pisces) and the beginning of another (the Age of Aquarius). [73]

Similarly, the Sun's December solstice position (in the northern hemisphere, the lowest point on its annual path in the southern hemisphere, the highest) was in the constellation of Sagittarius, one of two constellations in which the zodiac intersects with the Milky Way. [74] Every year, on the December solstice, the Sun and the Milky Way, appear (from the surface of the Earth) to come into alignment, and every year precession caused a slight shift in the Sun's position in the Milky Way. Given that the Milky Way is between 10° and 20° wide, it takes between 700 and 1,400 years for the Sun's December solstice position to precess through it. [75] In 2012 it was about halfway through the Milky Way, crossing the galactic equator. [76] In 2012, the Sun's December solstice fell on 21 December. [77]

#### Mysticism Edit

Mystical speculations about the precession of the equinoxes and the Sun's proximity to the center of the Milky Way appeared in Hamlet's Mill (1969) by Giorgio de Santillana and Hertha von Deschend. These were quoted and expanded upon by Terence and Dennis McKenna in The Invisible Landscape (1975).

Adherents to the idea, following a theory first proposed by Munro Edmonson, [78] alleged that the Maya based their calendar on observations of the Great Rift or Dark Rift, a band of dark dust clouds in the Milky Way, which, according to some scholars, the Maya called the Xibalba be or "Black Road". [79] John Major Jenkins claims that the Maya were aware of where the ecliptic intersected the Black Road and gave this position in the sky a special significance in their cosmology. [80] Jenkins said that precession would align the Sun precisely with the galactic equator at the 2012 winter solstice. [80] Jenkins claimed that the classical Maya anticipated this conjunction and celebrated it as the harbinger of a profound spiritual transition for mankind. [81] New Age proponents of the galactic alignment hypothesis argued that, just as astrology uses the positions of stars and planets to make claims of future events, the Maya plotted their calendars with the objective of preparing for significant world events. [82] Jenkins attributed the insights of ancient Maya shamans about the galactic center to their use of psilocybin mushrooms, psychoactive toads, and other psychedelics. [83] Jenkins also associated the Xibalba be with a "world tree", drawing on studies of contemporary (not ancient) Maya cosmology. [84]

#### Criticism Edit

Astronomers such as David Morrison argue that the galactic equator is an entirely arbitrary line and can never be precisely drawn, because it is impossible to determine the Milky Way's exact boundaries, which vary depending on clarity of view. Jenkins claimed he drew his conclusions about the location of the galactic equator from observations taken at above 11,000 feet (3,400 m), an altitude that gives a clearer image of the Milky Way than the Maya had access to. [64] Furthermore, since the Sun is half a degree wide, its solstice position takes 36 years to precess its full width. Jenkins himself noted that even given his determined location for the line of the galactic equator, its most precise convergence with the center of the Sun already occurred in 1998, and so asserts that, rather than 2012, the galactic alignment instead focuses on a multi-year period centered in 1998. [85] [86] [87]

There is no clear evidence that the classic Maya were aware of precession. Some Maya scholars, such as Barbara MacLeod, [40] Michael Grofe, [88] Eva Hunt, Gordon Brotherston, and Anthony Aveni, [89] have suggested that some Mayan holy dates were timed to precessional cycles, but scholarly opinion on the subject remains divided. [27] There is also little evidence, archaeological or historical, that the Maya placed any importance on solstices or equinoxes. [27] [90] It is possible that only the earliest among Mesoamericans observed solstices, [91] but this is also a disputed issue among Mayanists. [27] [90] There is also no evidence that the classic Maya attached any importance to the Milky Way there is no glyph in their writing system to represent it, and no astronomical or chronological table tied to it. [92]

### Timewave zero and the I Ching Edit

"Timewave zero" is a numerological formula that purports to calculate the ebb and flow of "novelty", defined as increase over time in the universe's interconnectedness, or organized complexity. [93] Terence McKenna claimed that the universe has a teleological attractor at the end of time that increases interconnectedness. He believed this which would eventually reach a singularity of infinite complexity in 2012, at which point anything and everything imaginable would occur simultaneously. He conceived this idea over several years in the early to mid-1970s whilst using psilocybin mushrooms and DMT. [93] [94] The scientific community considers novelty theory to be pseudoscience. [95] [96]

McKenna expressed "novelty" in a computer program which produces a waveform known as "timewave zero" or the "timewave". Based on McKenna's interpretation of the King Wen sequence of the I Ching, an ancient Chinese book on divination, [58] the graph purports to show great periods of novelty corresponding with major shifts in humanity's biological and sociocultural evolution. He believed that the events of any given time are resonantly related to the events of other times, and chose the atomic bombing of Hiroshima as the basis for calculating his end date of November 2012. [97] When he later discovered this date's proximity to the end of the 13th bʼakʼtun of the Maya calendar, he revised his hypothesis so that the two dates matched. [54]

The 1975 first edition of The Invisible Landscape referred to 2012 (but no specific day during the year) only twice. In the 1993 second edition, McKenna employed Sharer's date [Note e] of 21 December 2012 throughout. [54] [94]

Novelty theory has been criticized for "rejecting countless ideas presumed as factual by the scientific community", depending "solely on numerous controversial deductions that contradict empirical logic", and encompassing "no suitable indication of truth", with the conclusion that novelty theory is a pseudoscience. [98]

The idea that the year 2012 presaged a world cataclysm, the end of the world, or the end of human civilization, became a subject of popular media speculation as the date of 21 December 2012 approached. This idea was promulgated by many pages on the Internet, particularly on YouTube. [99] The Discovery Channel was criticized for its "quasi-documentaries" about the subject that "sacrifice[d] accuracy for entertainment". [100]

### Other alignments Edit

Some people interpreted the galactic alignment apocalyptically, claiming that its occurrence would somehow create a combined gravitational effect between the Sun and the supermassive black hole at the center of our galaxy (known as Sagittarius A*), creating havoc on Earth. [101] Apart from the "galactic alignment" already having happened in 1998, the Sun's apparent path through the zodiac as seen from Earth did not take it near the true galactic center, but rather several degrees above it. [76] Even were this not the case, Sagittarius A* is 30,000 light years from Earth it would have to have been more than 6 million times closer to cause any gravitational disruption to Earth's Solar System. [102] [103] This reading of the alignment was included on the History Channel documentary Decoding the Past. John Major Jenkins complained that a science fiction writer co-authored the documentary, and he went on to characterize it as "45 minutes of unabashed doomsday hype and the worst kind of inane sensationalism". [104]

Some believers in a 2012 doomsday used the term "galactic alignment" to describe a different phenomenon proposed by some scientists to explain a pattern in mass extinctions supposedly observed in the fossil record. [105] According to the Shiva Hypothesis, mass extinctions are not random, but recur every 26 million years. To account for this, it was suggested that vertical oscillations made by the Sun on its 250-million-year orbit of the galactic center cause it to regularly pass through the galactic plane. When the Sun's orbit takes it outside the galactic plane which bisects the galactic disc, the influence of the galactic tide is weaker. However, when re-entering the galactic disc—as it does every 20–25 million years—it comes under the influence of the far stronger "disc tides", which, according to mathematical models, increase the flux of Oort cloud comets into the inner Solar System by a factor of 4, thus leading to a massive increase in the likelihood of a devastating comet impact. [106] However, this "alignment" takes place over tens of millions of years, and could never be timed to an exact date. [107] Evidence shows that the Sun passed through the plane bisecting the galactic disc three million years ago and in 2012 was moving farther above it. [108]

A third suggested alignment was some sort of planetary conjunction occurring on 21 December 2012 however, there was no conjunction on that date. [12] Multi-planet alignments did occur in both 2000 and 2010, each with no ill result for the Earth. [109] Jupiter is the largest planet in the Solar System larger than all other planets combined. When Jupiter is near opposition, the difference in gravitational force that the Earth experiences is less than 1% of the force that the Earth feels daily from the Moon. [110]

### Geomagnetic reversal Edit

Another idea tied to 2012 involved a geomagnetic reversal (often referred to as a pole shift by proponents), possibly triggered by a massive solar flare, that would release an energy equal to 100 billion atomic bombs. [111] This belief was supposedly supported by observations that the Earth's magnetic field was weakening, [112] which could precede a reversal of the north and south magnetic poles, and the arrival of the next solar maximum, which was expected sometime around 2012. [113]

Most scientific estimates, however, say that geomagnetic reversals take between 1,000 and 10,000 years to complete, [114] and do not start on any particular date. [115] Furthermore, the U.S. National Oceanic and Atmospheric Administration predicted that the solar maximum would peak in late 2013 or 2014, and that it would be fairly weak, with a below-average number of sunspots. [116] In any case, there was no scientific evidence linking a solar maximum to a geomagnetic reversal, which is driven by forces entirely within the Earth. [117] Instead, a solar maximum would be mostly notable for its effects on satellite and cellular phone communications. [118] David Morrison attributed the rise of the solar storm idea to physicist and science popularizer Michio Kaku, who claimed in an interview with Fox News that a solar peak in 2012 could be disastrous for orbiting satellites, and to NASA's headlining a 2006 webpage as "Solar Storm Warning", a term later repeated on several doomsday pages. [99]

On 23 July 2012, a massive, potentially damaging, solar storm came within nine days of striking Earth. [119] [120]

### Planet X/Nibiru Edit

Some believers in a 2012 doomsday claimed that a planet called Planet X, or Nibiru, would collide with or pass by the Earth. This idea, which appeared in various forms since 1995, initially predicted Doomsday in May 2003, but proponents abandoned that date after it passed without incident. [121] The idea originated from claims of channeling alien beings and is widely ridiculed. [121] [122] Astronomers calculated that such an object so close to Earth would be visible to anyone looking up at the night sky. [121]

### Other catastrophes Edit

Author Graham Hancock, in his book Fingerprints of the Gods, interpreted Coe's remarks in Breaking the Maya Code [123] as evidence for the prophecy of a global cataclysm. [124] Filmmaker Roland Emmerich later credited the book with inspiring his 2009 disaster film 2012. [125]

Other speculations regarding doomsday in 2012 included predictions by the Web Bot project, a computer program that purports to predict the future by analyzing Internet chatter. However, commentators have rejected claims that the bot is able to predict natural disasters, as opposed to human-caused disasters like stock market crashes. [126]

The 2012 date was also loosely tied to the long-running concept of the Photon Belt, which predicted a form of interaction between Earth and Alcyone, the largest star of the Pleiades cluster. [127] Critics argued that photons cannot form belts, that the Pleiades, located more than 400 light years away, could have no effect on Earth, and that the Solar System, rather than getting closer to the Pleiades, was in fact moving farther away from it. [128]

Some media outlets tied the fact that the red supergiant star Betelgeuse would undergo a supernova at some point in the future to the 2012 phenomenon. [129] However, while Betelgeuse was certainly in the final stages of its life, and would die as a supernova, there was no way to predict the timing of the event to within 100,000 years. [130] To be a threat to Earth, a supernova would need to be no further than 25 light years from the Solar System. Betelgeuse is roughly 600 light years away, and so its supernova would not affect Earth. [131] In December 2011, NASA's Francis Reddy issued a press release debunking the possibility of a supernova occurring in 2012. [132]

Another claim involved alien invasion. In December 2010, an article, first published in examiner.com and later referenced in the English-language edition of Pravda [133] claimed, citing a Second Digitized Sky Survey photograph as evidence, that SETI had detected three large spacecraft due to arrive at Earth in 2012. [134] Astronomer and debunker Phil Plait noted that by using the small-angle formula, one could determine that if the object in the photo were as large as claimed, it would have had to be closer to Earth than the Moon, which would mean it would already have arrived. [134] In January 2011, Seth Shostak, chief astronomer of SETI, issued a press release debunking the claims. [133]

The phenomenon spread widely after coming to public notice, particularly on the Internet. Hundreds of thousands of websites were posted on the subject. [99] "Ask an Astrobiologist", a NASA public outreach website, received over 5,000 questions from the public on the subject from 2007, [127] some asking whether they should kill themselves, their children or their pets. [99] In May 2012, an Ipsos poll of 16,000 adults in 21 countries found that 8 percent had experienced fear or anxiety over the possibility of the world ending in December 2012, while an average of 10 percent agreed with the statement "the Mayan calendar, which some say 'ends' in 2012, marks the end of the world", with responses as high as 20 percent in China, 13 percent in Russia, Turkey, Japan and Korea, and 12 percent in the United States. [135] At least one suicide was directly linked to fear of a 2012 apocalypse, [136] with others anecdotally reported. [137] Jared Lee Loughner, the perpetrator of the 2011 Tucson shooting, followed 2012-related predictions. [138] A panel of scientists questioned on the topic at a plenary session at the Astronomical Society of the Pacific contended that the Internet played a substantial role in allowing this doomsday date to gain more traction than previous similar panics. [137]

### Europe Edit

Beginning in 2000, the small French village of Bugarach, population 189, began receiving visits from "esoterics"—mystic believers who had concluded that the local mountain, Pic de Bugarach, was the ideal location to weather the transformative events of 2012. In 2011, the local mayor, Jean-Pierre Delord, began voicing fears to the international press that the small town would be overwhelmed by an influx of thousands of visitors in 2012, even suggesting he might call in the army. [139] [140] "We've seen a huge rise in visitors", Delord told The Independent in March 2012. "Already this year more than 20,000 people have climbed right to the top, and last year we had 10,000 hikers, which was a significant rise on the previous 12 months. They think Pic de Bugarach is 'un garage à ovnis' [a garage for UFOs]. The villagers are exasperated: the exaggerated importance of something which they see as completely removed from reality is bewildering. After 21 December, this will surely return to normal." [141] In December 2012, the French government placed 100 police and firefighters around both Bugarach and Pic de Bugarach, limiting access to potential visitors. [142] Ultimately, only about 1,000 visitors appeared at the height of the "event". Two raves were foiled, 12 people had to be turned away from the peak, and 5 people were arrested for carrying weapons. [143] Jean-Pierre Delord was criticised by members of the community for failing to take advantage of the media attention and promote the region. [144]

The Turkish village of Şirince, near Ephesus, expected to receive over 60,000 visitors on 21 December 2012, as New Age mystics believed its "positive energy" would aid in weathering the catastrophe. [145] Only a fraction of that number actually arrived, with a substantial component being police and journalists, and the expected windfall failed to materialise. [146]

Similarly, the pyramid-like mountain of Rtanj, in the Serbian Carpathians, attracted attention, due to rumors that it would emit a powerful force shield on the day, protecting those in the vicinity. Hotels around the base were full. [147]

In Russia, inmates of a women's prison experienced "a collective mass psychosis" in the weeks leading up to the supposed doomsday, while residents of a factory town near Moscow reportedly emptied a supermarket of matches, candles, food and other supplies. The Minister of Emergency Situations declared in response that according to "methods of monitoring what is occurring on the planet Earth", there would be no apocalypse in December. [148] When asked when the world would end in a press conference, Russian President Vladimir Putin said, "In about 4.5 billion years." [149]

In December 2012, Vatican astronomer Rev. José Funes wrote in the Vatican newspaper L'Osservatore Romano that apocalyptic theories around 2012 were "not even worth discussing". [150]

### Asia and Australia Edit

In China, up to one thousand members of the Christian cult Almighty God were arrested after claiming that the end of bʼakʼtun 13 marked the end of the world, and that it was time to overthrow Communism. [151] [152] Shoppers were reported to be hoarding supplies of candles in anticipation of coming darkness, while online retailer Taobao sold tickets to board Noah's Ark to customers. [153] Bookings for wedding ceremonies on 21 December 2012 were saturated in several cities. [153] On 14 December 2012, a man in Henan province attacked and wounded twenty-three children with a knife. Authorities suspected the man had been "influenced" by the prediction of the upcoming apocalypse. [154] Academics in China attributed the widespread belief in the 2012 doomsday in their country to a lack of scientific literacy and a mistrust of the government-controlled media. [154]

On 6 December 2012, Australian Prime Minister Julia Gillard delivered a hoax speech for the radio station triple J in which she declared "My dear remaining fellow Australians the end of the world is coming. Whether the final blow comes from flesh-eating zombies, demonic hell-beasts or from the total triumph of K-Pop, if you know one thing about me it is this—I will always fight for you to the very end." [155] Radio announcer Neil Mitchell described the hoax as "immature" and pondered whether it demeaned her office. [156]

### Mexico and Central America Edit

Those Mesoamerican countries that once formed part of the Maya civilization—Mexico, Guatemala, Honduras, and El Salvador—all organized festivities to commemorate the end of bʼakʼtun 13 at the largest Maya sites. On 21 December 2011, the Maya town of Tapachula in Chiapas activated an eight-foot digital clock counting down the days until the end of bʼakʼtun 13. [157] On 21 December 2012, major events took place at Chichén Itzá in Mexico and Tikal in Guatemala. [3] [4] [5] In El Salvador, the largest event was held at Tazumal, and in Honduras, at Copán. In all of these archaeological sites, Maya rituals were held at dawn led by shamans and Maya priests. [158] [159] [160]

On the final day of bʼakʼtun 13, residents of Yucatán and other regions formerly dominated by the ancient Maya celebrated what they saw as the dawn of a new, better era. [161] According to official figures from Mexico's National Institute of Anthropology and History (INAH), about 50,000 people visited Mexican archaeological sites on 21 December 2012. Of those, 10,000 visited Chichén Itzá in Yucatán, 9,900 visited Tulum in Quintana Roo, and 8,000 visited Palenque in Chiapas. An additional 10,000 people visited Teotihuacan near Mexico City, which is not a Maya site. [162] The main ceremony in Chichén Itzá was held at dawn in the plaza of the Temple of Kukulkán, one of the principal symbols of Maya culture. The archaeological site was opened two hours early to receive thousands of tourists, mostly foreigners who came to participate in events scheduled for the end of bʼakʼtun 13. [3] [162]

The fire ceremony at Tikal was held at dawn in the main plaza of the Temple of the Great Jaguar. The ceremony was led by Guatemalan and foreign priests. The President of Guatemala, Otto Pérez, and of Costa Rica, Laura Chinchilla, participated in the event as special guests. During the ceremony the priests asked for unity, peace and the end of discrimination and racism, with the hope that the start of a new cycle will be a "new dawn". About 3,000 people participated in the event. [158] [163]

Most of these events were organized by agencies of the Mexican and Central American governments, and their respective tourism industries expected to attract thousands of visitors. [4] [158] Mexico is visited by about 22 million foreigners in a typical year. However, in 2012, the national tourism agency expected to attract 52 million visitors just to the regions of Chiapas, Yucatán, Quintana Roo, Tabasco and Campeche. [157] A Maya activist group in Guatemala, Oxlaljuj Ajpop, objected to the commercialization of the date. A spokesman from the Conference of Maya Ministers commented that for them the Tikal ceremony is not a show for tourists but something spiritual and personal. The secretary of the Great Council of Ancestral Authorities commented that living Maya felt they were excluded from the activities in Tikal. This group held a parallel ceremony, and complained that the date has been used for commercial gain. In addition, before the main Tikal ceremony, about 200 Maya protested the celebration because they felt excluded. Most modern Maya were indifferent to the ceremonies, and the small number of people still practising ancient rites held solemn, more private ceremonies. [4] [158]

Osvaldo Gomez, a technical advisor to the Tikal site, complained that many visitors during the celebration had illegally climbed the stairs of the Temple of the Masks, causing "irreparable" damage. [164]

### South America Edit

In Brazil, Décio Colla, the Mayor of the City of São Francisco de Paula, Rio Grande do Sul, mobilized the population to prepare for the end of the world by stocking up on food and supplies. [165] [166] In the city of Corguinho, in the Mato Grosso do Sul, a colony was built for survivors of the expected tragedy. [167] In Alto Paraíso de Goiás, the hotels also made specific reservations for prophetic dates. [168]

In Bolivia, President Evo Morales participated in Quechua and Aymara rituals, organized with government support, to commemorate the Southern solstice that took place in Isla del Sol, in the southern part of Lake Titicaca. During the event, Morales proclaimed the beginning of "Pachakuti", meaning the world's wake up to a culture of life and the beginning of the end to world capitalism, and he proposed to dismantle the International Monetary Fund and the World Bank. [5] [158] [169]

On 21 December 2012, the Uritorco in Córdoba, Argentina was closed, as a mass suicide there had been proposed on Facebook. [170]

### North America Edit

In the United States, sales of private underground blast shelters increased noticeably after 2009, with many construction companies' advertisements calling attention to the 2012 apocalypse. [171] In Michigan, schools were closed for the Christmas holidays two days early, in part because rumours of the 2012 apocalypse were raising fears of repeat shootings similar to that at Sandy Hook. [172] American reality TV stars Heidi Montag and Spencer Pratt revealed that they had spent most of their $10 million of accumulated earnings by 2010 because they believed the world would end in 2012. [173] Authors such as Graham Hancock continue to refer to supposed Maya prophecies about 2012 in Magicians of the Gods (2015). For example, he writes, “. the Maya were not speaking of the end of the world, as such, but rather the end of an age—‘a time of great transformation and world rebirth’—that would be followed by the beginning of a new great cycle or world age”. [174] The 2012 phenomenon was discussed or referenced in several media. Several TV documentaries, as well as some contemporary fictional references to the year 2012, referred to 21 December as the day of a cataclysmic event. The UFO conspiracy TV series The X-Files cited 22 December 2012 as the date for an alien colonization of the Earth and mentioned the Mayan calendar "stopping" on this date. [54] The History Channel aired a handful of special series on doomsday that included analysis of 2012 theories, such as Decoding the Past (2005–2007), 2012, End of Days (2006), Last Days on Earth (2006), Seven Signs of the Apocalypse (2009), and Nostradamus 2012 (2008). [175] The Discovery Channel also aired 2012 Apocalypse in 2009, suggesting that massive solar storms, magnetic pole reversal, earthquakes, supervolcanoes, and other drastic natural events could occur in 2012. [176] In 2012, the National Geographic Channel launched a show called Doomsday Preppers, a documentary series about survivalists preparing for various cataclysms, including the 2012 doomsday. [177] Hundreds of books were published on the topic. [99] The bestselling book of 2009, [178] Dan Brown's The Lost Symbol, featured a coded mock email number (2456282.5) that decoded to the Julian date for 21 December 2012. [179] In cinema, the 2009 disaster film 2012 was inspired by the phenomenon, and advance promotion prior to its release included a stealth marketing campaign in which TV spots and websites from the fictional "Institute for Human Continuity" called on people to prepare for the end of the world. As these promotions did not mention the film itself, many viewers believed them to be real and contacted astronomers in panic. [180] [181] Although the campaign was heavily criticized, [99] the film became one of the most successful of its year, grossing nearly$770 million worldwide. [182] An article in The Daily Telegraph attributed the widespread fear of the 2012 phenomenon in China to the film, which was a smash hit in that country because it depicted the Chinese building "survival arks". [183] Lars von Trier's 2011 film Melancholia featured a plot in which a planet emerges from behind the Sun on a collision course with Earth. [184]

The phenomenon also inspired several rock and pop music hits. As early as 1997, "A Certain Shade of Green" by Incubus referred to the mystical belief that a shift in perception would arrive in 2012 ("Are you gonna stand around till 2012 A.D.? / What are you waiting for, a certain shade of green?"). More recent hits include "2012 (It Ain't the End)" (2010) performed by Jay Sean and "Till the World Ends" (2011) performed by Britney Spears. Towards mid-December 2012, an internet hoax related to South Korean singer Psy being one of the Four Horsemen of the Apocalypse was widely circulated around social media platforms. The hoax purported that once Psy's "Gangnam Style" YouTube video amassed a billion views, the world would end. [185] Indian composer A. R. Rahman, known for Slumdog Millionaire, released his single "Infinite Love" to "instill faith and optimism in people" prior to the predicted doomsday. [186] The artwork for All Time Low's 2012 album "Don't Panic" satirizes various cataclysmic events associated with the world ending on 21 December 2012.

A number of brands ran commercials tied to the 2012 apocalypse in the months and days leading to the date. In February 2012, American automotive company General Motors aired an advertisement during the annual Super Bowl football game in which a group of friends drove Chevrolet Silverados through the ruins of human civilization following the 2012 apocalypse, while on 17 December 2012, Jell-O ran an ad saying that offering Jell-O to the Mayan gods would appease them into sparing the world. John Verret, Professor of Advertising at Boston University, questioned the utility of tying large sums of money to such a unique and short-term event. [187]

## Carbon Dioxide

Carbon dioxide (CO2) is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. The first graph shows atmospheric CO2 levels measured at Mauna Loa Observatory, Hawaii, in recent years, with average seasonal cycle removed. The second graph shows CO2 levels during the last three glacial cycles, as reconstructed from ice cores.

Over the past 171 years, human activities have raised atmospheric concentrations of CO2 by 48% above pre-industrial levels found in 1850. This is more than what had happened naturally over a 20,000 year period (from the Last Glacial Maximum to 1850, from 185 ppm to 280 ppm).

The time series below shows global distribution and variation of the concentration of mid-tropospheric carbon dioxide in parts per million (ppm). The overall color of the map shifts toward the red with advancing time due to the annual increase of CO2.