# Trajectory: What would happen if the sun disappeared one day?

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So, let's just assume, to no aspect explainable to humans, the sun just magically popped out of existence on January 1st next year (2022), that'll never happen, this is just a scenario to explain my question. If the sun disappeared, regardless of life on Earth, where would the Earth float off to? If it would come close to a gas giant, then a gravity assist would affect the Earth's path through space. Where would it go?

In an answer, I want a feasibly explained way to calculate where Earth would go, not giving much thought to Gravity assists, since I got their calculations from this question, the first answer, and the answer in the link embedded in it.

Also, in the comments section, I've seen comments claiming that my question is a possible duplicate of others. One other addresses what would happen here on Earth, while the other one is about how long it would take for us to stop orbiting the sun after its sudden disappearance. In contrast, I'm wondering about where the Earth would float off to, and where it would go.

Now, this question can seemingly be applied to any celestial object, whether the sun is there or not, I want to figure out trajectory in space. I want to know about trajectory, and how it affects the motion of celestial bodies.

Assuming this can be answered theoretically by the use of equations and mathematics, thanks in advance!

On the first of January, the direction of the sun from Earth is towards Sagittarius, with an ecliptic longitude of 280. The velocity of the Earth around the sun is perpendicular that that, and towards Virgo, in particular, it is close to the direction of Gamma Virginis (Porrima), with an ecliptic longitude of 280-90 = 190. The Earth will move in a straight line in that direction. (Conveniently Jan 1st is very close to perihelion, so elliptic corrections are needed even less than normal)

It won't actually get near to Gamma Virginis because that star is 38 light years away and at the Earth's speed of 30km/s it would take 400,000 years to get close and by then the star will have moved away from its current location.

It wouldn't come close to a gas giant (none are in a position in which they would come anywhere near the trajectory of the Earth, even without checking, they are all on the "wrong" side of the sun)

It would be very unlikely for the Earth to come close to a gas giant. If it did then the gravity of the giant planet would change the direction of the Earth, it could go in almost any direction.

For another date, the equation is simple enough: find the ecliptic longitude of the sun on that date and subtract 90. That gives the ecliptic longitude of the Earth's velocity.

You can now use a star map to find the direction that the Earth will travel in. On January 1st the Earth will travel in a direction toward an ecliptic longitude of 190, but remain in the plane of the ecliptic. On the map below, the ecliptic is the line through the middle of the map and you can find where 190 is by looking at the numbers at the top and bottom.

Because in the absence of the sun, there would be nothing to cause the Earth to orbit, it would travel in a straight line towards that point.

## Dear Parker Solar Probe: How 'touching the sun' caps off a lifetime in science

Eugene Parker, the NASA mission's namesake, reflects on six decades of studying our home star.

I think there's a point that’s not widely appreciated, but it's fundamental: The sun is an ordinary star of middling mass and middling brightness, but it’s a model for almost all stars—and the only one we’re going to see up close enough to do a whole lot of measurements. There are stars that are oddballs, the ones that interest the astrophysics types. But the fact that the sun supports life on one of its planets is already a unique designation.

I’m in love with the sun for that reason. Somehow, in many circles, solar physics is looked upon as old, dusty, dried-up problems that don’t really have new solutions. On the contrary, it’s the one star where we know what we’re talking about!

Like the sun, you also have a unique designation: You're named after me. I was sitting in the office in 2017 when Tom Zurbuchen, NASA's associate administrator, called one day and said, “NASA’s talking about putting your name on the Solar Probe. Can you think of any reason why we shouldn't name it after you?” I was sort of stunned it took a little while to get it straight in my mind. I guess it makes me more conceited than ever.

After all, the people who built you were in a position to make a heck of a spacecraft. You're making many, many trips past the sun, each time getting a little closer because you've hooked around Venus. You plunge in, you get some data, and your trajectory takes you out again. Then on the next swoop in, you come a bit closer than the last time, monitoring the gas and magnetic fields streaming by and eagerly looking for new effects. On the way, the sun must appear mighty large in the sky.

It takes my breath away when I think about it, how far we’ve come. When I think back to 1955, we had a lot of concepts about how space worked, but most of them were wrong, or at least so vague that you couldn’t argue whether they were right or wrong. When John Simpson at the University of Chicago offered me a position at one of the first space science laboratories, I didn't have any experience in the field, really. This was in the days before we went into space and sent up spacecraft like you whatever we did, we stood at the surface of the earth and looked up at the sky and wondered what was going on.

In those days, one of the outstanding questions was whether the space between planets should be considered absolutely empty, or full of loose electrons, magnetic fields, and stuff from the sun. So John had a brilliant idea. He built neutron monitors—sensitive cosmic-ray detectors—and distributed them from Peru to Colorado. By watching how the cosmic-ray intensity varied at each latitude, we could deduce variations in what's going on in space.

I was hired to interpret the data. Once I saw the sun was expelling particles and magnetic fields, I could see that this “solar wind” of freely moving particles was simply a problem in fluid mechanics. Its easily solved equation of motion showed that the wind starts from the sun with a very small velocity, but because of its million-degree temperature, it expands to supersonic speeds at large distances. The wind becomes more tenuous as it goes farther out, and as the sun rotates, the magnetic fields are stretched out by the wind and form a spiral in interplanetary space.

### Fast Facts: Parker Solar Probe

Launch Date: August 12, 2018

Launch Vehicle: United Launch Alliance Delta IV Heavy

Launch Wet Mass: 1,510 pounds (685 kg)

Power Source: 16.7 square feet of solar panels

Heat Shield: 4.5-inch-thick carbon composite

Closest Planned Distance to Sun: 3.83 million miles

Fastet Planned Orbital Velocity: 430,000 miles an hour

At that time, most people had a simpler picture, so the response to my paper on the subject was bitterly negative, except for a few acquaintances. I tended to shrug my shoulders: I had done the math correctly, I had a job and a salary, and I really didn’t give a damn what they thought.

Observations in space in 1962 verified the existence of the solar wind, and missions in later years blocked out the details of its varying structure, a record to which you will be adding fresh data. Everywhere around the sun—over the poles, over the equator—there's an outflow of particles at a few hundred kilometers a second, and it's going so fast because its observed temperature is on the order of a million degrees. The question now is, why so hot? It's not heated by magic.

In the 1980s, I published a theory on coronal heating that you're now putting to the test. You, Solar Probe, are the first serious effort to go into this mess and get some numbers, so we can have something explicit to argue about. My hope is you'll get in close enough to the sun to pick up the waves and turbulent magnetic fields whose dissipation is responsible for heating the corona. But if it's something else, it's just that much more exotic, and that much more fun.

Thirty years ago, I would never have dreamed of a successful mission like you, but you are well-armed with instruments to do the task. I've always felt that the people who don’t get the right credit are the teams that designed and built you. You don’t see their names anywhere, but you and many other spacecraft are remarkable technological achievements. Nicola Fox, who was your project scientist until recently, is quite an impressive person. She and the team really are outstanding people.

I was fortunate enough to be invited to your launch. We were back at some distance from the launchpad. We saw the rocket rising up and going faster and faster, and as we watched, you simply got fainter and fainter.

In seven years, you'll be abandoned, you know, and forever orbit the sun. We will never see you again. We can talk to you on the radio, but we’ll never see you. To see you leaving, I almost feel that you're an old friend, and I hate to throw you to the dogs this way.

## 9 Powerful Lessons We Can Learn From The Sun

As you rise out of bed every day, the sun also rises, and when the earth turns on its axis to give sunlight to the other side of the globe, you also retire from the day’s work and go to bed.

Your very biorhythms jive and sync at the whim of the sun, and the clouds beneath it transmit to you, in subconscious signals, the scope and purpose of your days.

How we spend our days is how we spend our lives.

So, it’s only fitting that we learn broader metaphorical lessons from the sun that we can weave into our daily routines to live more empowered lives.

Yes, we may be a solar company, but we believe not just in solar powered homes, but also in living a better life. Buying solar arrays is just a part of what we believe to be that better life.

If we can learn to be as steady and giving as the sun, we will have lived lives not just worth remembering, but lives worth living, too.

So, without further ado, here are 10 powerful life lessons we can learn from the sun. Enjoy!

#### 1. Accomplished Great Tasks, and Quickly.

Did you know it only takes eight and a half minutes for sunlight to reach our planet?

That’s a pretty quick timeframe to deliver something that allows over 7.4 billion people to live, breathe, and enjoy the miracle of Earth itself. Especially when the delivery distance is 92.5 million miles.

So, not only does the sun carry the weight of the world on its helium-esque shoulders, it puts humankind to shame for even using the commonly quipped phrase “I have the weight of the world on my shoulders,” or “I am carrying the weight of the world on my back.”

Next time you feel like you have the weight of the world on your shoulders, study-up on the sun’s convection patterns, dynamo process, and magnetic fields which convert the hydrogen and helium its comprised of into energy that literally keeps our earth not just in orbit, but also capable of carbon-based life.

And, the next time someone asks something great of you, try as quickly as you can to do it in eight and a half minutes!

#### 2. Rise Above It All.

The sun makes up 98 percent of the mass in our solar system, so it’s only fitting that we study the way it conducts itself, especially as it pertains to how the sun always seems to rise above it all in a manner more consistent than any other example in nature can provide us.

Burning hydrogen and helium in a blaze of glory, the sun is undaunted by anything that stands in its way, and is governed by a set of physical laws that ensures we benefit from it every day, even if we do not necessarily see it.

How much could you accomplish if you rose above every obstacle in your path to achieve your goals? The sun can’t be distracted. It follows its order and provides to those who need it without folder.

If you can be as consistent as the sun in fulfilling your obligations, you will likely become the most effective person you know.

On one quick note for the astronomy buffs out there, yes, we know the sun technically doesn’t “rise.” The Earth merely spins, but it appears to us as if the sun does rise.

And in the event our universe was designed, perhaps the way the sun appears to us serves as a teleological indicator of how we should govern ourselves in our daily routines.

More simply put, if the display of how the sun and earth interoperate in the heavens doesn’t give us a visual depiction of how we should live our lives, the way we experience the sun from Earth surely does.

Are you as dependable to others as the sun is to you?

Sometimes it’s hard to be dependable for other people when we feel like our heads are already under water.

However, T.S. Eliot said it best when he pointed out that we’ll never know how tall we are if our heads are never under water.

And learning how to be dependable for others is a great starting point for opening ourselves up to the discomfort needed to grow into dependable people.

The sun provides the photosynthesis that plants (and therefore vegetables and fruit, which we depend on for great health), need to grow into consumable energy. It gives us warmth, and it gives us efficient ways to power our homes with solar panels.

The sun is also so dependable that we can count on it to power our homes, and for lower long-term costs than utility companies can ever provide on their own.

If you can be as dependable for others as the sun is for you, you will be a person everyone wants to keep in their lives.

#### 3. Do What’s Expected of You, and Without Thanks.

Sometimes something can be so dependable that we take it for granted. Much in the same manner, when we count on others to do things for us, it becomes easy to forget to thank them because their greatness demonstrates no deviation from the norm.

And once we become used to the norm, we oft forget to remember the significance of others’ actions.

However, doing great things shouldn’t be about recognition—it should be about the utility we provide for other people, and the sun serves as an exemplary case of this truism.

#### 4. Rise Early and Surely.

Sometimes we have days where we just want to stay in bed. Our lives feel as overcast and dreary as ever, and we know there’s a job waiting for us to be completed, somewhere, somehow.

That’s when the temptation to stay in bed and blow off the entire day comes in to play.

Could you imagine what would happen if the sun decided, as if it had any volition of its own, to take a day off?

If the sun disappeared for a day, we would float out of its orbit, and be without its warmth and rays of light for eternity. One day without it means eons without it. The seas would freeze over, the All earth-dwelling lifeforms would be die, and the

#### 5. If You’re Out of Sight, Make Sure People Know You’re Still There for Them.

Although the sun sometimes goes out of sight, we can still count on it for us to be there in the morning when we wake up.

If you’re too busy to tend to everything needed of you in a single day, and aren’t getting the face time you need with loved ones due to personal objectives and goals in your own life, then just make sure those who depend on you know you will eventually get back to them and that you will keep them in mind, no matter what.

#### 6. Know When It’s Time to Bow Out.

Sometimes something other than ourselves needs to take center stage and bask in the limelight. The sun never pushes the moon out of the way right in the middle of an eclipse.

Not only would that be impolite on the part of the sun, it would deprive everyone of one of the most marvelous astronomical spectacles known to humankind.

A marvel of modern existence, getting solar eclipse glasses can help us see humility as an act of not just the nature of the heavens, but also as an opportunity to reflect upon how often we give the stage to others when they deserve it.

#### 7. Adapt to Your Place in the Order of the Universe.

I can almost hear what you’re thinking at this point: So, if I should learn my place in the universe from the sun, that means I should act as if I’m the center of the universe, right?

Because the sun isn’t the center of the universe. It is merely the centerpiece of our galaxy. In fact, there are numerous celestial bodies in the universe far bigger than the sun, such as Betelgeuse, Antares, and VY Canis Majoris.

The sun is the biggest thing in our galaxy, but it is 9.3 billion times smaller than VY Canis Majoris.

Yes, that’s correct. You can fit 9.3 billion of our suns inside of VY Canis Majoris, the largest known hyper red giant and star in the known universe.

This life lesson is geared especially toward the millennial generation reading this post. Before you hate on this life lesson too much, know that a millennial is writing this post (I was born in 1990).

Yes, you’re a special snowflake, but knowing your place in the order of the universe and, more specifically, the world, can help you understand that you are part of a system much greater than yourself.

The sooner you can find a way to start contributing to this larger-than-self system, the better off you’ll be in the long run.

Although you may be everything to someone, you’re not everything to everyone.

Just as you may be everything to your wife or your husband, your girlfriend or your boyfriend, your brother or your sister, you are not everything to everyone else in the universe. But you can and should be something to someone.

#### 8. Don’t Put Shade on the Accomplishments of Others.

Does the sun discriminate against others when selecting to whom it should give its light?

No. It may provide light to us at a different time each day depending on where we’re located, but it shares and distributes its light in a remarkably even and fair fashion.

The sun gives us the light we need to see the miracles of others’ work, not just to see the miracles we may work ourselves.

When someone else does something significant, it’s worth giving them the light he or she deserves. No matter what the circumstances surrounding his or her track record. Light heals, and we should allow others to receive it whenever possible.

Although many cultures around the world champion individual accomplishment and dominance above all else, ask yourself where you’d be today if nobody gave you an opportunity to shine on the stage of your life.

Would you be singing the same tune or dancing the same dance?

#### 9. Know When to Put the Heat on Others, and How to Receive It Gracefully.

There will be seemingly innumerable times in our lives where we’ll have to play the scalding hot sun, and the person we’re upset with will have to play yard worker without sunscreen. These roles will also be reversed throughout the course of a lifetime, no matter who you are.

There are specific ways each of these solar scenarios should be handled.

Sunlight is a gift, but sometimes it also gets a little too hot for comfort. When we’re on the receiving end of the heat, we should remember why we’re thankful for it to get through the myriad discomforts we feel while laboring beneath it. After all, without the sunlight, we wouldn’t be able to grow and progress as individuals.

Laboring in the sun for a few hours can build integrity. The more discomfort we can endure, the stronger we’ll become and the more we’ll grow.

When it comes to putting the heat on others, we need to remember to assert ourselves without coming off as too pushy.

Whether at work, home, or school, very few of us enjoys physical confrontation. However, sometimes it’s necessary to be assertive and galvanize others into action when we need to see results.

Just as the sun has a way of laying the heat on us while we’re laboring, we need to develop our own way of laying the heat on others in a way that permits their growth, understanding, and development.

After all, if we never ask for something that we want from somebody, the odds of getting what we want are drastically reduced.

#### Bringing It All Together.

Looking to the heavens at what powers our planet can give us a better perspective on how we can bring heaven to Earth and become more like the very forces that help us operate in the world.

Green business has always been a part of Scott’s life. At the age of 11, Scott Cramer started Cramerco – a curbside recycling business. After graduating from university, Scott started Simple Solutions, an energy consulting firm designed to save business owners money and help the environment. Scott has immersed himself in solar since 2009 when he first saw the effect it could have on the lives of others. For the past six years, Scott has been President of the Go Solar Group.

## If The Sun Went Out, How Long Would Life On Earth Survive?

If you put a steamy cup of coffee in the refrigerator, it wouldn’t immediately turn cold. Likewise, if the sun simply “turned off” (which is actually physically impossible), the Earth would stay warm—at least compared with the space surrounding it—for a few million years. But we surface dwellers would feel the chill much sooner than that.

Within a week, the average global surface temperature would drop below 0°F. In a year, it would dip to –100°. The top layers of the oceans would freeze over, but in an apocalyptic irony, that ice would insulate the deep water below and prevent the oceans from freezing solid for hundreds of thousands of years. Millions of years after that, our planet would reach a stable –400°, the temperature at which the heat radiating from the planet’s core would equal the heat that the Earth radiates into space, explains David Stevenson, a professor of planetary science at the California Institute of Technology.

Although some microorganisms living in the Earth’s crust would survive, the majority of life would enjoy only a brief post-sun existence. Photosynthesis would halt immediately, and most plants would die in a few weeks. Large trees, however, could survive for several decades, thanks to slow metabolism and substantial sugar stores. With the food chain’s bottom tier knocked out, most animals would die off quickly, but scavengers picking over the dead remains could last until the cold killed them.

Humans could live in submarines in the deepest and warmest parts of the ocean, but a more attractive option might be nuclear- or geothermal-powered habitats. One good place to camp out: Iceland. The island nation already heats 87 percent of its homes using geothermal energy, and, says astronomy professor Eric Blackman of the University of Rochester, people could continue harnessing volcanic heat for hundreds of years.

Of course, the sun doesn’t merely heat the Earth it also keeps the planet in orbit. If its mass suddenly disappeared (this is equally impossible, by the way), the planet would fly off, like a ball swung on a string and suddenly let go.

## Do you like seasons?

The Earth's axis is tilted, and that tilt can change with time. No biggie, all the planets do it it's fun. But what'snot fun is when the tilt changes rapidly. What would happen if Antarctica pointed straight at the sun for 24 hours a day, plunging North America and Europe into permanent darkness? And then a few hundred thousand years later it flipped over? We take the long-term regularity of our seasons for granted, and we might have the moon to thank for it.

Those kinds of crazy wild swings in the axial tilt are due to resonances, or unlucky interactions with distant objects in the solar system. For instance, letꞌs say that one day in its orbit the Earth's axis just happens to point away from the sun, and Jupiter is hanging out in that direction at the same time. And let's say that happens again … and again … and again. Every time Earth's axis and Jupiter line up, it gets a super-tiny gravitational pull. At first it's nothing. But over millions of years it can add up. Before you know it, the accumulation of tugs has flipped the Earth over like a pancake.

What might stabilize this is the moon: it's really, really big (at least compared with the Earth), and orbits us pretty fast. All that angular momentum (rotational energy) prevents the other planets from playing any axial shenanigans.

Or not. The moon may actually be hurting us in the long term, since it's slowing us down, which makes us more susceptible to the intrigues of the outer planets. But that's a billion-year problem anyway, and if the moon disappeared tomorrow, our seasons would still be seasonal for a really long time.

So, besides the tides, would we notice a disappeared moon? Well, yes, because it's really big and bright, and there'd be nothing to howl at anymore. But would it affect us? Not really. So as for the moon … I'm over it!

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter is also host of the podcasts Ask a Spaceman and RealSpace, and the YouTube series Space In Your Face.

## Trajectory: What would happen if the sun disappeared one day? - Astronomy

I've been thinking about gravity and would like to ask if we actually recorded the speed in which it moves.

In the theory of relativity, the speed of gravity should be equal to the speed of light, since the theoretical "particles" that carry gravity (sometimes called gravitons) are massless particles, just like photons (the particles that carry light). The light from the Sun takes 8 minutes to reach the Earth, so that if the Sun suddenly disappeared it would take 8 minutes before it got dark. Similarly the Earth would also feel the effects of the Sun's gravity for 8 minutes after it magically vanished.

In September 2002, two US scientists made some very accurate measurements of the position of a quasar as it passed behind Jupiter. They argued that the exact amount of apparent motion of the quasar (as the path of the radio waves from it was bent in Jupiter's gravitational field) depended on both the speed of light AND the speed of gravity. The measurements they took then proved that the speed of gravity is the same as that of light, ruling out some of the more bizarre modifications to the laws of gravity which have been proposed, and further backing General Relativity (BBC news article on the experiment).

More recently, LIGO's first detection of gravitational waves coming from a binary neutron star set an much more accurate limit for the difference between the speed of light and the speed of gravity: the difference is just 10 -16 times the speed of light. This bound set by LIGO's detection makes us feel confident that the speed of gravity is, for almost all practical purposes, equal to the speed of light.

#### Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

The first thing we must understand is that from a purely kinematic point of view, the heliocentric and geocentric models are both equally correct within the accuracy limits of astronomical instruments available before the, say, 16th century. There was no way for an astronomer who lived before Tycho Brahe to bring serious arguments in favor of one or the other. (That's why Galileo Galilei had such trouble with the astronomical establishment of the day -- he simply did not have any good arguments to bring in favor of his pet theory.)

The problem is that from a dynamic point of view, for a geocentric model to be correct it is necessary to abolish the law of universal gravitation: and this means, of course, that the universe in which a geocentric model is correct from a physical point of view has vastly different physics from ours. Whether "a world similar to Earth would exist" in an universe with vastly different physics than ours is not something that anybody but you can answer.

We don't know. The law of universal gravity doesn't work in your world, so we have no idea how wind works, how the water cycle works, the lot. By the way, how does fire work in a world where the law of universal gravity does not operate?

Length of day, month, or year:

Those are purely kinematic phenomena, and from a purely kinematic point of view the heliocentric and geocentric models are both equally correct within the accuracy limits of astronomical instruments available before the Renaissance.

The sun will rise and the sun will set. We have no idea how the atmosphere works, or how thick it is, because the law of universal gravitation doesn't work in that world. So we don't know if, for example, the sun will appear red at sunset.

Our kind of gravity doesn't work in an universe where the geocentric model is correct. It must be some different force which is called gravity. How it works nobody but you, the author, can say.

No effect whatsoever. The funny thing is that up to this day celestial navigation, as an application of practical astronomy, is done assuming a geocentric model. See celestial sphere for how this works.

Of course, satellite-based navigation systems won't work, because the law of universal gravitation doesn't work.

Any huge effect I don't have enough science to anticipate:

The main huge effect is that only the author can say how that world works, because it most definitely it doesn't work like ours. What keeps water in the ocean, what keeps people on the ground? Does hot air rise? Why? Are there tides? Why?

Note that you do not have to make Sun any smaller or bigger -- whether we adopt a heliocentric or geocentric system has no impact on the distance between the Earth and the Sun.

Everything also applies for the Moon. A Moon may or may not exist if it exists, it is not universal gravitation which makes it orbit. What is it that keeps the Moon in orbit only the author can decide.

It would be perfectly possible for an extremely advanced civilization, perhaps humans of the future, to create a geocentric solar system.

They could take a rogue Earth-sized planet in interstellar space and create a giant sun satellite orbiting the planet with gigantic fusion power generators generating power for thousands of giant lamps aimed at the planet to heat it and warm it.

If they want the sidereal day of the Earth-sized planet to be similar to that of Earth (23 hours, 56 minutes, 4.0905 seconds) they will have to select an Earth-sized planet in interstellar space that rotates with a similar period and/or slow down or spreed up the rotation of the planet. If they do that the stars at night will seem to circle with the same speed as on Earth.

The giant artificial sun satellite will have to orbit at such a distance that the solar day (the time between two successive noons or midnights at the same location) will equal 24 hours. So that means that the time it takes for the giant artificial sun satellite to make one orbit combined with the time it takes for the planet to rotate once (the sidereal day) will equal 24 hours, a solar day on Earth. I'm certain there are some users at this site who can easily calculate the distance for you.

Of course there is the problem that the "moon" should orbit the Earth-sized planet at the same distance that the Moon orbits the Earth in order to have a month of the same length and similar tides.

In Aristotle's (384–322 BC) description of the universe, the Moon marked the boundary between the spheres of the mutable elements (earth, water, air and fire), and the imperishable stars of aether, an influential philosophy that would dominate for centuries.[183] However, in the 2nd century BC, Seleucus of Seleucia correctly theorized that tides were due to the attraction of the Moon, and that their height depends on the Moon's position relative to the Sun.[184] In the same century, Aristarchus computed the size and distance of the Moon from Earth, obtaining a value of about twenty times the radius of Earth for the distance. These figures were greatly improved by Ptolemy (90–168 AD): his values of a mean distance of 59 times Earth's radius and a diameter of 0.292 Earth diameters were close to the correct values of about 60 and 0.273 respectively.[185] Archimedes (287–212 BC) designed a planetarium that could calculate the motions of the Moon and other objects in the Solar System.[186]

So the size and distance of the Moon was measured reasonably accurately about 2,000 years ago. And a fake moon orbiting a fake earth in an artificial geocentric solar system would have to orbit the fake earth at a similar distance to that of the real Moon.

Which could be a farther distance than than the proper distance for the giant artificial sun satellite to orbit. Which would be bad because on Earth eclipses are caused by the nearer Moon passing in front of the farther Sun.

There are many other things to consider when designing a possible artificial geocentric solar system. But presumably some users on this board can do it for you.

A possibly simpler way to create an artificial geocentric solar system would be to find an Earth-sized rogue planet in interstellar space and build a gigantic artificial geodesic spherical structure around it and fit the inner surface of that spherical structure with countless gazillions of lamps. The lamps would be programmed to turn on and off in patterns to simulate the movements of the Sun, the Moon, the visible planets in the Solar System, and the stars.

So if it is scientifically possible for an advanced civilization to create an artificial geocentric solar system, a possibly artificial or natural geocentric solar system might exist in a science fiction story set in some parallel universe where the laws of science are different. And of course a natural geocentric solar system might exist in a fantasy story filled with magic.

## Scientists Successfully Predicted the Shape of the Solar Corona

By: Emily Sandford August 31, 2018 1

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Scientists predicted the shape of the solar corona as it would be seen during the August 21, 2017, total solar eclipse. Observations confirmed that they got the broad strokes right.

The Sun is about as easy to study as any astronomical object could be. It’s bright, so there’s no shortage of light to examine it’s nearby, so even small details on its surface are clear and for about twelve hours per day, it faces almost no competition for astronomical attention.

But for all its nearness and brightness, the Sun remains mysterious. Ironically, its outermost layer — the corona, an intricate crown of super-heated, diffuse plasma — is the least understood. The corona expresses the hidden magnetic angst of the Sun. Because plasma is made of charged particles, which respond to magnetic influence, the Sun’s magnetic field can twist the corona into loops and bands and prongs.

When the magnetic field, continually pulled and stressed by the Sun’s rotation, erupts, it launches coronal plasma into interplanetary space. This type of space weather threatens satellites, electrical grids, and telecommunications networks, so it’s in our best interest to understand it. Now, solar physicists have shown August 27th in Nature Astronomy that they can accurately predict the appearance of the corona one week in advance — an important milestone on the path to predicting the oncoming solar wind.

Predictive Science Inc. developed a numerical model that simulated what the corona would look like during the August 21, 2017, total solar eclipse. This animation compares a composite image generated from photographs taken on the day of the total eclipse (Aug. 21, 2017) to the model’s predictions.
Predictive Science Inc. / Miloslav Druckmüller, Peter Aniol, Shadia Habbal / NASA Goddard, Joy Ng

### The Once and Future Corona

Zoran Mikić (Predictive Science, Inc.) and collaborators offer a new model of the Sun’s outer layers that’s up to date with the latest theoretical work on how the interior of the Sun heats and magnetically innervates the corona. Mikić and colleagues put this model to the test last year, when they took observations of the Sun on July 16 and August 11, 2017, and let a NASA supercomputer calculate, according to their model, what the solar corona would look like ten days later, during the August 21st total solar eclipse. They then compared these visualizations to actual images taken by ground-based photographers.

Left: Alson Wong captured this composite image of the solar corona during the August 21, 2017, eclipse from Jackson, Wyoming. It was rotated to match the perspective seen in the simulations. (See the Nature Astronomy paper for more images.) Center: This simulated image of the solar corona shows a visualization of the 3D magnetic field, intended to highlight the complexity of the Sun's magnetic field and its intimate connection to visible emission from the corona. Right: The simulation also traced the magnetic field lines emanating from the Sun. (See text below for an explanation of the blue box and red arrows.)
Left: Alson Wong / S&T Online Photo Gallery, Center, Right: Predictive Science, Inc.

It’s worth pausing here to emphasize how unusual a study like this is — generally, astronomers study slowly evolving, faraway objects. It’s rare to be able to run a simulation and test its results immediately. The results of the computer run were encouraging: The simulated corona has the same broad shape as its real-life counterpart, with a few bold, bright “streamers” of plasma flowing out into space, as well as intervening loops with small-scale structure similar to those of the real Sun.

While the simulated Sun isn’t perfect, its decent correspondence to the real Sun gives solar astronomers confidence that they’re on the right track to understanding the physics of the Sun’s outer layers. In the sandbox of their simulation, Mikić and collaborators are even able to put solar physics to the test — they noticed, for example, coronal rays extending to the left of the solar disk (highlighted in the blue box in the figure above), which are visually similar to the plumes that burst forth from the Sun’s north and south poles (red arrows). At the poles, this is known to happen because the magnetic field lines extend straight out into space, like the lines that point straight outward from the ends of a bar magnet. To verify that the left-pointing rays had the same physical origin, Mikić and collaborators reached into their simulation, turned off the pole-like parts of the corona, and watched the rays disappear.

Together with new and improved measurements of the Sun’s magnetic field, models like this one could soon “track the continuous evolution of the Sun, similar to what is done in terrestrial weather models,” the authors conclude. With such data coming soon from missions like NASA’s Parker Solar Probe, we’re on track to never being surprised by a solar storm again!

## What Would Happen If The Moon Crashed Into Earth?

It’s the first and only place beyond Earth where humans have set foot. The Moon’s gravitational pull causes tides on Earth. Tides that might have been the encouragement for life in our oceans to move on land. This pull also keeps Earth from wobbling on its axis, making our climate relatively stable.

In short, the Moon makes Earth a more livable place. What if it suddenly sped up, and started driving in Earth’s direction? The Moon’s plan to destroy Earth by bumping into it would break into pieces the moment it reaches the Roche limit.

The Moon itself would shatter, never making it to Earth’s surface. And that’s going to look very impressive! But wait, what is this Roche limit? In celestial mechanics, it is the point at which the gravity holding a satellite together is weaker than the tidal forces trying to pull it apart.

In other words, the Moon can only get as close as 18,470 km (11,470 miles) away from our planet, before – BOOM! The tidal forces would tear it apart. All the footprints and flags we’ve left on the Moon, all of its craters and valleys would scatter to form a breathtaking ring of debris above Earth’s equator, 37,000-kilometers in diameter (23,000-miles).

## Einstein's eclipse

Public Domain via Live Science

While the ancients viewed eclipses as signs of great acts of God, physicists viewed the 1919 solar eclipse (shown here) as a triumph of science. During 1919&rsquos epic eclipse, in which the sun vanished for 6 minutes and 51 seconds, scientists measured the bending of light from the stars as they passed near the sun. The findings confirmed Einstein&rsquos theory of general relativity, which describes gravity as a warping of space-time.