# Why do scientists assume they can measure the shape of the universe if it is also widely believed to be infinite?

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The shape of the universe is the question of whether the universe is flat, has a positive curvature or a negative one. More recently astronomers have compared radiation coming from extremely distant points of the observable universe and have concluded that it is flat with a 0.4% margin of error, Based on articles I've read elsewhere this seems to have created the consensus that the universe is indeed flat. But isn't the universe also believed to be infinite in size? If it is really infinite then shouldn't such measurements be inconsequential as an infinite curved universe would still appear perfectly flat to a local observer?

Yes, the universe is believed to be infinite in size. That's what you get if the curvature is zero or negative, assuming a simple topology. The curvature has to be positive for a finite universe, once again, assuming a simple topology, and no weird stuff like edges.

Now it's possible that the universe has a very small positive curvature, so that it's finite, but it's so large that it looks flat to us.

However, it's reasonable to assume that the observable universe is representative of the whole thing, and not just coincidentally a region of anomalous curvature. Of course, that's impossible to verify, but if the curvature were significantly greater outside our observable patch we'd expect the curvature to be a bit higher near the edges than it is in the middle of the patch, and we don't see that in the data.

But if the global curvature equals the maximum positive curvature consistent with the 0.4% margin of error of the WMAP, BOOMERanG, and Planck data, then the radius of curvature of the whole universe is (currently) around 150 times larger than the radius of the observable universe. And of course, in the future it will continue to expand.

That figure comes from How Big is the Entire Universe? by astrophysicist Ethan Siegel. That article has a great explanation of curvature, with lots of helpful diagrams.

If it is really infinite then shouldn't such measurements be inconsequential as an infinite curved universe would still appear perfectly flat to a local observer?

No, it wouldn't necessarily. It could, but it's not mandatory.

Imagine an infinite line that just takes a sharp turn at some point. It would definitely be "curvy" at that point, even though it's infinite.

Take a parabola. It is infinite, but has a definite curvature in every point.

Same goes for our 3D universe.

Why do scientists assume they can measure the shape of the universe if it is also widely believed to be infinite?

Because not everybody thinks it's infinite. Take a look at the timeline of the Big Bang written by Luke Mastin in 2009. He said “The linear dimensions of the early universe increases during this period of a tiny fraction of a second by a factor of at least 10$$^{26}$$ to around 10 centimetres (about the size of a grapefruit)”. You can find John Gribbin talking about a universe the size of a grapefruit in his 2008 book The Universe: A Biography. You can find Marcus Chown talking about a universe the size of a grapefruit in his review of Alan Guth's 1997 book The Inflationary Universe. You can also find Jeremiah Ostriker and Paul Steinhardt talking about a universe the size of a grapefruit in The Quintessential Universe in SciAm in 2002. They weren't talking about the observable universe. They were talking about the whole universe. And if it was the size of a grapefruit 13.8 billion years ago, it can't be infinite now.

The shape of the universe is the question of whether the universe is flat, has a positive curvature or a negative one. More recently astronomers have compared radiation coming from extremely distant points of the observable universe and have concluded that it is flat with a 0.4% margin of error.

That's right. Two out of three options were always going to be wrong. IMHO if you've read the Einstein digital papers it's obvious that the universe was going to be flat. Yes, Einstein came up the idea of a closed curved universe, see his 2nd February postcard to Willem de Sitter. But by 1932 he and de Sitter had dropped the idea in favour of flat space in their Einstein-de Sitter universe. See John Baez and Emory Bunn's preliminaries article dating from 2006: “Similarly, in general relativity gravity is not really a 'force', but just a manifestation of the curvature of spacetime. Note: not the curvature of space, but of spacetime. The distinction is crucial”. Curved space is not the same thing as curved spacetime. Unfortunately some people confuse the two.

Based on articles I've read elsewhere this seems to have created the consensus that the universe is indeed flat.

I think that consensus is correct.

But isn't the universe also believed to be infinite in size?

A lot of people claim that a flat universe must be an infinite universe. But it's a non-sequitur. Going back to Einstein again, he thought of space as a thing. That's why in his 1929 essay on the history of field theory, he described a field as a state of space. In his Nottingham lecture in 1930 he said space “remains the sole medium of reality”. So I think it's reasonable to envisage the universe as a sphere of space, with no space beyond it. Maybe light rays would undergo something akin to total internal reflection.

If it is really infinite then shouldn't such measurements be inconsequential as an infinite curved universe would still appear perfectly flat to a local observer?

That's what some people say. But they also say things like "the universe was infinite at the time of the Big Bang and it's even more infinite now". I'm not fond of that because it doesn't seem to fit in with Big Bang cosmology, and I just don't see how an infinite universe can expand.

## How Old is the Universe?

Age may only be a number, but when it comes to the age of the universe, it's a pretty important one. According to research, the universe is approximately 13.8 billion years old. How did scientists determine how many candles to put on the universe's birthday cake? They can determine the age of the universe using two different methods: by studying the oldest objects within the universe and measuring how fast it is expanding.

## New Quantum Paradox Reveals Contradiction Between Widely Held Beliefs – “Something’s Gotta Give”

Probing the reality of observations made by an artificial quantum intelligence. Credit: Artwork by Anthony Dunnigan.

Quantum physicists at Griffith University have unveiled a new paradox that says, when it comes to certain long-held beliefs about nature, “something’s gotta give.”

Quantum theory is practically perfect at predicting the behavior we observe when we perform experiments on tiny objects like atoms. But applying quantum theory at scales much larger than atoms, in particular to observers who make the measurements, raises difficult conceptual issues.

In a paper published in Nature Physics, an international team led from Griffith University in Australia has sharpened those issues into a new paradox.

“The paradox means that if quantum theory works to describe observers, scientists would have to give up one of three cherished assumptions about the world,” said Associate Professor Eric Cavalcanti, a senior theory author on the paper.

“The first assumption is that when a measurement is made, the observed outcome is a real, single event in the world. This assumption rules out, for example, the idea that the universe can split, with different outcomes being observed in different parallel universes.”

“The second assumption is that experimental settings can be freely chosen, allowing us to perform randomized trials. And the third assumption is that once such a free choice is made, its influence cannot spread out into the universe faster than light,” he said.

“Each of these fundamental assumptions seems entirely reasonable, and is widely believed. However, it is also widely believed that quantum experiments can be scaled up to larger systems, even to the level of observers. But we show that one of these widely held beliefs must be wrong! Giving up any one of them has far-reaching consequences for our understanding of the world.”

The team has established the paradox by analyzing a scenario with well-separated entangled quantum particles combined with a quantum ‘observer’ – a quantum system that can be manipulated and measured from the outside, but which can itself make measurements on a quantum particle.

“Based on the three fundamental assumptions, we have mathematically determined limits on what experimental results are possible in this scenario. But quantum theory, when applied to observers, predicts results that violate these limits. In fact, we have already performed a proof-of-principle experiment using entangled photons (particles of light),” said Dr. Nora Tischler, a senior experimental author. “And we found a violation just as quantum theory predicted.”

“But our ‘observer’ had a very small ‘brain’, so to speak. It has just two memory states, which are realized as two different paths for a photon. That’s why we call it a proof-of-principle experiment, not a conclusive demonstration that one of the three fundamental assumptions in our paradox must be wrong,” she said.

“For a more definitive implementation of the paradox, our dream experiment is one where the quantum observer is a human-level artificial intelligence program running on a massive quantum computer,” said Professor Howard Wiseman, the leader of the project and Director of Griffith’s Centre for Quantum Dynamics, where the theoretical and experimental teams are based.

“That would be a pretty convincing test of whether quantum theory fails for observers, or whether one of the three fundamental assumptions is false. But that’s probably decades away.”

Experimental apparatus for a test of the paradox with particles of light. Credit: Kok-Wei Bong.

The Centre for Quantum Dynamics laboratory in which the experiment was performed is also part of the Centre for Quantum Computation and Communication Technology, an Australian Research Council Centre of Excellence.

“It has long been recognized that quantum computers will revolutionize our ability to solve hard computational problems,” Professor Wiseman said.

“What we didn’t realize until we started this research is that they may also help answer hard philosophical problems – the nature of the physical world, the mental world, and their relationship.”

Reference: “A strong no-go theorem on the Wigner’s friend paradox” by Kok-Wei Bong, Aníbal Utreras-Alarcón, Farzad Ghafari, Yeong-Cherng Liang, Nora Tischler, Eric G. Cavalcanti, Geoff J. Pryde and Howard M. Wiseman, 17 August 2020, Nature Physics.
DOI: 10.1038/s41567-020-0990-x

## Why do scientists assume they can measure the shape of the universe if it is also widely believed to be infinite? - Astronomy

While Copernicus rightly observed that the planets revolve around the Sun, it was Kepler who correctly defined their orbits. At the age of 27, Kepler became the assistant of a wealthy astronomer, Tycho Brahe, who asked him to define the orbit of Mars. Brahe had collected a lifetime of astronomical observations, which, on his death, passed into Kepler&rsquos hands. (Brahe, who had his own Earth-centered model of the Universe, withheld the bulk of his observations from Kepler at least in part because he did not want Kepler to use them to prove Copernican theory correct.) Using these observations, Kepler found that the orbits of the planets followed three laws.

Like many philosophers of his era, Kepler had a mystical belief that the circle was the Universe&rsquos perfect shape, and that as a manifestation of Divine order, the planets&rsquo orbits must be circular. For many years, he struggled to make Brahe&rsquos observations of the motions of Mars match up with a circular orbit.

Eventually, however, Kepler noticed that an imaginary line drawn from a planet to the Sun swept out an equal area of space in equal times, regardless of where the planet was in its orbit. If you draw a triangle out from the Sun to a planet&rsquos position at one point in time and its position at a fixed time later&mdashsay, 5 hours, or 2 days&mdashthe area of that triangle is always the same, anywhere in the orbit. For all these triangles to have the same area, the planet must move more quickly when it is near the Sun, but more slowly when it is farthest from the Sun.

This discovery (which became Kepler&rsquos second law of orbital motion) led to the realization of what became Kepler&rsquos first law: that the planets move in an ellipse (a squashed circle) with the Sun at one focus point, offset from the center.

Kepler&rsquos third law shows that there is a precise mathematical relationship between a planet&rsquos distance from the Sun and the amount of time it takes revolve around the Sun. It was this law that inspired Newton, who came up with three laws of his own to explain why the planets move as they do.

### Newton&rsquos Laws of Motion

If Kepler&rsquos laws define the motion of the planets, Newton&rsquos laws define motion. Thinking on Kepler&rsquos laws, Newton realized that all motion, whether it was the orbit of the Moon around the Earth or an apple falling from a tree, followed the same basic principles. &ldquoTo the same natural effects,&rdquo he wrote, &ldquowe must, as far as possible, assign the same causes.&rdquo Previous Aristotelian thinking, physicist Stephen Hawking has written, assigned different causes to different types of motion. By unifying all motion, Newton shifted the scientific perspective to a search for large, unifying patterns in nature. Newton outlined his laws in Philosophiae Naturalis Principia Mathematica (&ldquoMathematical Principles of Natural Philosophy,&rdquo) published in 1687.

Law I. Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed theron.

In essence, a moving object won&rsquot change speed or direction, nor will a still object start moving, unless some outside force acts on it. The law is regularly summed up in one word: inertia.

Law II. The alteration of motion is ever proportional to the motive force impressed and is made in the direction of the right line in which that force is impressed.

Newton&rsquos second law is most recognizable in its mathematical form, the iconic equation: F=ma. The strength of the force (F) is defined by how much it changes the motion (acceleration, a) of an object with some mass (m).

Law III. To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.

As Newton himself described: &ldquoIf you press a stone with your finger, the finger is also pressed by the stone.&rdquo

### Gravity

Within the pages of Principia, Newton also presented his law of universal gravitation as a case study of his laws of motion. All matter exerts a force, which he called gravity, that pulls all other matter towards its center. The strength of the force depends on the mass of the object: the Sun has more gravity than Earth, which in turn has more gravity than an apple. Also, the force weakens with distance. Objects far from the Sun won&rsquot be influenced by its gravity.

Newton&rsquos laws of motion and gravity explained Earth&rsquos annual journey around the Sun. Earth would move straight forward through the universe, but the Sun exerts a constant pull on our planet. This force bends Earth&rsquos path toward the Sun, pulling the planet into an elliptical (almost circular) orbit. His theories also made it possible to explain and predict the tides. The rise and fall of ocean water levels are created by the gravitational pull of the Moon as it orbits Earth.

### Einstein and Relativity

The ideas outlined in Newton&rsquos laws of motion and universal gravitation stood unchallenged for nearly 220 years until Albert Einstein presented his theory of special relativity in 1905. Newton&rsquos theory depended on the assumption that mass, time, and distance are constant regardless of where you measure them.

The theory of relativity treats time, space, and mass as fluid things, defined by an observer&rsquos frame of reference. All of us moving through the universe on the Earth are in a single frame of reference, but an astronaut in a fast-moving spaceship would be in a different reference frame.

Within a single frame of reference, the laws of classical physics, including Newton&rsquos laws, hold true. But Newton&rsquos laws can&rsquot explain the differences in motion, mass, distance, and time that result when objects are observed from two very different frames of reference. To describe motion in these situations, scientists must rely on Einstein&rsquos theory of relativity.

At slow speeds and at large scales, however, the differences in time, length, and mass predicted by relativity are small enough that they appear to be constant, and Newton&rsquos laws still work. In general, few things are moving at speeds fast enough for us to notice relativity. For large, slow-moving satellites, Newton&rsquos laws still define orbits. We can still use them to launch Earth-observing satellites and predict their motion. We can use them to reach the Moon, Mars, and other places beyond Earth. For this reason, many scientists see Einstein&rsquos laws of general and special relativity not as a replacement of Newton&rsquos laws of motion and universal gravitation, but as the full culmination of his idea.

## A universe of 10 dimensions

Superstring theory posits that the universe exists in 10 dimensions at once. Credit: National Institute of Technology Tiruchirappalli.

When someone mentions "different dimensions," we tend to think of things like parallel universes – alternate realities that exist parallel to our own, but where things work or happened differently. However, the reality of dimensions and how they play a role in the ordering of our Universe is really quite different from this popular characterization.

To break it down, dimensions are simply the different facets of what we perceive to be reality. We are immediately aware of the three dimensions that surround us on a daily basis – those that define the length, width, and depth of all objects in our universes (the x, y, and z axes, respectively).

Beyond these three visible dimensions, scientists believe that there may be many more. In fact, the theoretical framework of Superstring Theory posits that the universe exists in ten different dimensions. These different aspects are what govern the universe, the fundamental forces of nature, and all the elementary particles contained within.

The first dimension, as already noted, is that which gives it length (aka. the x-axis). A good description of a one-dimensional object is a straight line, which exists only in terms of length and has no other discernible qualities. Add to it a second dimension, the y-axis (or height), and you get an object that becomes a 2-dimensional shape (like a square).

The third dimension involves depth (the z-axis), and gives all objects a sense of area and a cross-section. The perfect example of this is a cube, which exists in three dimensions and has a length, width, depth, and hence volume. Beyond these three lie the seven dimensions which are not immediately apparent to us, but which can be still be perceived as having a direct effect on the universe and reality as we know it.

Scientists believe that the fourth dimension is time, which governs the properties of all known matter at any given point. Along with the three other dimensions, knowing an objects position in time is essential to plotting its position in the universe. The other dimensions are where the deeper possibilities come into play, and explaining their interaction with the others is where things get particularly tricky for physicists.

The timeline of the universe, beginning with the Big Bang. According to String Theory, this is just one of many possible worlds. Credit: NASA

According to Superstring Theory, the fifth and sixth dimensions are where the notion of possible worlds arises. If we could see on through to the fifth dimension, we would see a world slightly different from our own that would give us a means of measuring the similarity and differences between our world and other possible ones.

In the sixth, we would see a plane of possible worlds, where we could compare and position all the possible universes that start with the same initial conditions as this one (i.e. the Big Bang). In theory, if you could master the fifth and sixth dimension, you could travel back in time or go to different futures.

In the seventh dimension, you have access to the possible worlds that start with different initial conditions. Whereas in the fifth and sixth, the initial conditions were the same and subsequent actions were different, here, everything is different from the very beginning of time. The eighth dimension again gives us a plane of such possible universe histories, each of which begins with different initial conditions and branches out infinitely (hence why they are called infinities).

In the ninth dimension, we can compare all the possible universe histories, starting with all the different possible laws of physics and initial conditions. In the tenth and final dimension, we arrive at the point in which everything possible and imaginable is covered. Beyond this, nothing can be imagined by us lowly mortals, which makes it the natural limitation of what we can conceive in terms of dimensions.

The existence of these additional six dimensions which we cannot perceive is necessary for String Theory in order for there to be consistency in nature. The fact that we can perceive only four dimensions of space can be explained by one of two mechanisms: either the extra dimensions are compactified on a very small scale, or else our world may live on a 3-dimensional submanifold corresponding to a brane, on which all known particles besides gravity would be restricted (aka. brane theory).

he existence of extra dimensions is explained using the Calabi-Yau manifold, in which all the intrinsic properties of elementary particles are hidden. Credit: A Hanson

If the extra dimensions are compactified, then the extra six dimensions must be in the form of a Calabi–Yau manifold (shown above). While imperceptible as far as our senses are concerned, they would have governed the formation of the universe from the very beginning. Hence why scientists believe that peering back through time, using telescopes to spot light from the early universe (i.e. billions of years ago), they might be able to see how the existence of these additional dimensions could have influenced the evolution of the cosmos.

Much like other candidates for a grand unifying theory – aka the Theory of Everything (TOE) – the belief that the universe is made up of ten dimensions (or more, depending on which model of string theory you use) is an attempt to reconcile the standard model of particle physics with the existence of gravity. In short, it is an attempt to explain how all known forces within our universe interact, and how other possible universes themselves might work.

For additional information, here's an article on Universe Today about parallel universes, and another on a parallel universe scientists thought they found that doesn't actually exist.

There are also some other great resources online. There is a great video that explains the ten dimensions in detail. You can also look at the PBS web site for the TV show Elegant universe. It has a great page on the ten dimensions.

You can also listen to Astronomy Cast. You might find episode 137 The Large Scale Structure of the Universe pretty interesting.

## New Study Shows How Teens Can Be Taught to Act More Rationally

The trouble with teenagers is well-known to many parents: they are hormone-driven, thrill-seeking bundles of eros with a shocking inability to think through the consequences of their actions. Adolescents don’t just procrastinate and spend too much time playing video games. They endanger themselves by driving too fast and too recklessly, sometimes while under the influence of alcohol. They take drugs that threaten their health and well-being. And they engage in unprotected sex at alarming (if now somewhat lower) rates, resulting in teenage pregnancies and sexually transmitted infections (STIs). David Dobbs summarized the science of teenage risk-taking a few years ago in National Geographic:

We court risk more avidly as teens than at any other time. This shows reliably in the lab, where teens take more chances in controlled experiments involving everything from card games to simulated driving. And it shows in real life, where the period from roughly 15 to 25 brings peaks in all sorts of risky ventures and ugly outcomes. This age group dies of accidents of almost every sort (other than work accidents) at high rates. Most long-term drug or alcohol abuse starts during adolescence, and even people who later drink responsibly often drink too much as teens. Especially in cultures where teenage driving is common, this takes a gory toll: In the U.S., one in three teen deaths is from car crashes, many involving alcohol.

This is why car rental agency are so reluctant to rent to drivers under the age of 25 and demand a steep premium when they do. It’s why insurance rates are higher for younger drivers, especially young men. One might conclude that the brains of teens are wired poorly, leading them to act on instinct without appreciating the risks of their behavior. That assumption is as widely held as it is deeply and curiously mistaken.

It’s not that teens lack the capacity for rationality or think of themselves as immune to mortality. Laurence Steinberg, a developmental psychologist quoted by Dobbs, says teens are just as capable of judiciously contemplating benefits and risks as adults they “actually overestimate risk,” he says. Teens do understand the risks they take. They just ignore those risks too often, sometimes with tragic results.

In a new study investigating alternative interventions to nudge adolescents toward safer behavior, psychologists Valerie Reyna of Cornell and Britain Mills of the University of Texas argue that teaching students the “gist” of how to act in a given situation is significantly more effective than just giving them the tools to weigh risks using their own powers of rationality. Reyna and Mills’ experiment exposed 734 teens from Arizona, Texas and New York to one of three different curricula to determine which is the most successful at promoting safer sex. One-third of the 14-19 year olds were assigned to a sexual education program model known as Reducing the Risk (RTR), one third to an enhanced model, RTR+, and the final third to a control curriculum with no sexual education content.

Both the RTR and RTR+ classes emphasized the risks of sexual behavior and, in particular, the risks of pregnancy and infection from unprotected sex. Here, for example, is how the educators drove home the idea that sex will eventually lead to pregnancy:

Given the probability of becoming pregnant for one act of unprotected sex, and assuming one such act per month, participants in the class drew cards from a hat representing whether they became pregnant. Participants who “become pregnant” stand, and the activity continues for one simulated year (12 draws), at which point the entire class is typically standing. In other words, the activity was structured so that by the end of the simulated year, virtually all of the participants became pregnant (or had gotten someone pregnant). The activity was accompanied by an interactive class discussion about when exactly they became pregnant in the exercise, when they would have the baby, and what the pregnancy would mean to the participant. For example, participants discuss how the pregnancy and baby would affect their own plans for the future (such as going to college) and how it would affect their life in the short term (such as involvement in extracurricular activities). Comparable discussions and activities were presented for STI infections.

That’s pretty powerful stuff, and it did have an impact on the teenagers’ sex practices over the ensuing months compared to those receiving no sex education at all. But this approach was not as effective as that used in RTR+ classrooms, where the exercise was summed up at the end with a “gist” statement, what the authors also call “the pragmatic bottom line”:

“Even low risks add up to 100% if you keep doing it.”

“Pregnancy might occur the 1st month, at 6 months, or at 13 months,” Reyna and Mills write, “but the gist is that it ‘would happen’ in about a year.” Such a “categorical contrast between an event occurring and not occurring (all-or-none),” coupled with repeated attention to the adolescents’ own values, resulted in impressive results over mere recitation, or demonstration, of the risk. The authors’ bottom line — yes, the gist of their article — is found in this graph. Follow the solid black line:

Simply walking teenagers through the risks of unprotected sex (the dashed line) helps to lower the degree to which they take risks with sexual partners—it does improve their “Hazard” profile over a curriculum with no sexual education (the dotted line). But drilling the moral of the story into their heads after walking them through the risks (the solid black line) is even more effective. What holds for sex ed should hold for drinking, driving, drugs and more: adolescents need to hear the bottom line, and hear it loud and clear. Being suggestive isn’t enough.

## The danger of hyper-specialization

The explosive expansion of knowledge that started in the mid 1800s led to hyper-specialization inside and outside academia. Even within a single discipline, say philosophy or physics, professionals often don't understand one another. As I wrote here before, "This fragmentation of knowledge inside and outside of academia is the hallmark of our times, an amplification of the clash of the Two Cultures that physicist and novelist C.P. Snow admonished his Cambridge colleagues in 1959." The loss is palpable, intellectually and socially. Knowledge is not adept to reductionism. Sure, a specialist will make progress in her chosen field, but the tunnel vision of hyper-specialization creates a loss of context: you do the work not knowing how it fits into the bigger picture or, more alarmingly, how it may impact society.

Many of the existential risks we face today — AI and its impact on the workforce, the dangerous loss of privacy due to data mining and sharing, the threat of cyberwarfare, the threat of biowarfare, the threat of global warming, the threat of nuclear terrorism, the threat to our humanity by the development of genetic engineering — are consequences of the growing ease of access to cutting-edge technologies and the irreversible dependence we all have on our gadgets. Technological innovation is seductive: we want to have the latest "smart" phone, 5k TV, and VR goggles because they are objects of desire and social placement.

## 10 Most Famous Scientific Theories That Were Later Debunked

The most genuine merit of science is probably its readiness to admit its mistakes (usually!). The theories in science are always being reconsidered and scrutinized. Modern research often rejects old ideas, hoaxes and myths.

Today’s post on our Science Blog will discuss ten of the most popular and influential scientific discoveries that were based on dubious data, and were consequently proven wrong, debunked and replaced with more reliable and logical modern theories.

### 1- Fleischmann–Pons’s Nuclear Fusion

Cold fusion is a supposed kind of nuclear reaction that would occur at relatively low temperatures compared with hot fusion. As a new type of nuclear reaction, it gained much popularity after reports in 1989 by famous electrochemists Stanley Pons and Martin Fleischmann. The craze about cold fusion became weaker as other scientists, after trying to repeat the experiment, failed to get similar results.

### 1a – One of Modern Science’s Greatest Misconceptions

The misconception that mass is destroyed in nuclear reactions.

### 2- Phrenology

Now widely considered as a pseudoscience, phrenology was the study of the shape of skull as indicative of the strengths of different faculties. Modern scientific research wiped it out by proving that personality traits could not be traced to specific portions of the brain.

### 3- The Blank Slate

The Blank Slate theory (or Tabula rasa), widely popularized by John Locke in 1689, proposed that individuals are born without built-in mental content and that their knowledge comes from experience and perception. Modern research suggests that genes and other family traits inherited from birth, along with innate instincts of course, also play a very important role.

### 4- Luminiferous Aether

The aether (or ether) was a mysterious substance that was thought to transmit light through the universe. The idea of a luminiferous aether was debunked as experiments in the diffraction and refraction of light, and later Einstein’s special theory of relativity, came along and entirely revolutionized physics.

### 5- Einstein’s Static (or Stationary) Universe

A static universe, also called a “stationary” or “Einstein” universe, was a model proposed by Albert Einstein in 1917. It was problematic from the beginning. Edwin Hubble’s discovery of the relationship between red shift obliterated it by completely demonstrating that the universe is constantly expanding.

### 6- Martian Canals

The Martian canals were a network of gullies and ravines that some 19th century scientists erroneously thought to exist on Mars. First detected in 1877 by Italian astronomer Giovanni Schiaparelli, modern telescopes and imaging technology completely debunked the myth. The “canals” were actually found to be a mere optical illusion.

### 7- Phlogiston Theory

First postulated in 1667 by German physician Johann Joachim Becher, Phlogiston Theory is an obsolete scientific theory regarding the existence of “phlogiston”, a fire-like element, which was contained within combustible bodies and released during combustion. The theory tried to explain burning processes such as combustion and the rusting of metals, which are now jointly termed as “oxidation”.

### 8- The Expanding or Growing Earth

The Expanding Earth or Growing Earth is a hypothesis suggesting that the position and relative movement of continents is dependent on the volume of the Earth increasing. Modern science has turned down any expansion or contraction of the Earth.

### 9- Discovery of the Planet Vulcan

A small planet that was supposed to exist in an orbit between Mercury and the Sun, French mathematician Urbain Jean Joseph Le Verrier coined the name “Vulcan” while trying to explain the nature of Mercury’s orbit. No such planet was ever discovered, while the orbit of Mercury was explained in detail by Albert Einstein’s theory of general relativity.

### 10- Spontaneous (or Equivocal) Generation

Spontaneous generation or equivocal generation is an obsolete principle concerning the origin of life from inanimate matter. The hypothesis was brought out by Aristotle who advocated the work of earlier natural philosophers. It was proven wrong in the 19th century by the experiments of Louis Pasteur, drawing influence from Francesco Redi who was an early proponent of germ theory and cell theory.

### Comments

RITAHEAD, the bible is a BOOK. I could write a book that says the Earth is flat and the Moon is made of green cheese and would that make it true? Of course not! The Bible is wrong about many things. Including the value of the pi constant. Deal with it.

Scientists use Hubble Telescope to comment the entire universe would be expanding.

How could Hubble Telescope work in reality? It simply works by collecting light from the sky through the use of primary mirror in this Telescope and then to reflect it upon a secondary mirror for analysis. However, the reflection of light by means of primary mirrors could result in obscure image in secondary mirror. The reason is simply lights could reflect in any directions and angles from any parts of primary mirror. As a result, overlapping of lights on secondary mirrors as a result of reflection from primary mirrors could be possible to the ultimate formation of obscure images. These collective obscure images could lead to false information that the entire universe could be expanding.

Hubble Space Telescope uses the same technique as Hubble Telescope to collect lights from the sky for analysis. Thus, false images could be gathered too.

Thus, fake images from the collection of lights from the sky through the reflective mirrors would cause information that would be gathered from Hubble Space or Hubble Telescope might not to be reliable.

I hope we can soon add the cholesterol theory of heart disease. It’s been debunked, but getting it to die is proving difficult.

I wished they would have mentioned the carbon dating and radioactive dating. One thing I did learn in science is that to prove your theory, you have to have a control. How can they prove that bones are millions of years old? My bible tells me the earth is not that old.

In genetics the definition of the “GENE” has changed over and over since it was coined by Johansson in 1909.

Gene as unit of function
Gene as unit of recombination
Gene as unit of mutation
One gene one enzyme concept
The central Dogma DNA->RNA->protein

All these views have been revised by newer concepts.
An overview of all outmoded definitions and the problematic attempts to offer a current defention that is valid now, was published in
http://genome.cshlp.org/content/17/6/669

neo-darwinism is largely debunked as explanation for increasing biological complexity. This theory, largely composed of population genetic concepts to understand how selection could bring change is still valid to explain variability within species.

The major explanation for increase of organismal complexity, i.e. from prokaryotes to eukaryotes, from single cell to multicellular organisms, from primitive to complex species is not explained by neodarwinism.

Horizontal gene transfer, Genome duplication (polyploidization and subsequent genome fragmentation) are largely singular events caused by drift rather than mutation and selection.

It is hardly understood by lay people how the current genomic revolution is reshaping evolutionary concepts.

And I have not even mentioned the revival of Lamarckism.

I think this contemporary example is a much nicer example that outmoded phlogiston theories from times before modern sciences had its current rigour

Some of these are dubious at best. For example, the luminiferous aether wasn’t debunked it was not needed in the new theories, and so it dropped out of physics, but that’s a very different matter. Locke’s objection to innate ideas, principles, knowledge, etc., not only wasn’t a scientific theory, but isn’t touched by genetic theory, or by any scientific theory. Moreover, he was happy to accept that we have innate capacities and abilities, which is all that science has attempted to explain in terms of genetics, etc. No-one, to the best of my knowledge, claimed to have discovered Vulcan, nor was its existence a theory, it was part of a hypothesis designed 9as you point out) to explain the ways in which Mercury’s orbit failed to accord with Newtonian physics.

A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of knowledge that has been repeatedly confirmed through observation and experiment.[1][2] Scientists create scientific theories from hypotheses that have been corroborated through the scientific method, then gather evidence to test their accuracy. As with all forms of scientific knowledge, scientific theories are inductive in nature and do not make apodictic propositions instead, they aim for predictive and explanatory force.[3][4]

1 National Academy of Sciences, 1999
2 AAAS Evolution Resources
3 Schafersman, Steven D. “An Introduction to Science”.
4 American Association for the Advancement of Science, Project 2061

Interesting piece. The only I have to point out it that the majorities of these were never widely held theories. Instead most of them were either hypothesis or were only believed to be true by a small percent of the scientific community. There is a big difference between hypothesis and scientific theory.

This is very wonderful. Science in its nature of existence is a circulating event in which its theories can be formulated and debunked. Thanks for the hard job done.

## The Expanding Universe

Every model of the universe must include the expansion we observe. Another key element of the models is that the cosmological principle (which we discussed in The Evolution and Distribution of Galaxies) is valid: on the large scale, the universe at any given time is the same everywhere (homogeneous and isotropic). As a result, the expansion rate must be the same everywhere during any epoch of cosmic time. If so, we don’t need to think about the entire universe when we think about the expansion, we can just look at any sufficiently large portion of it. (Some models for dark energy would allow the expansion rate to be different in different directions, and scientists are designing experiments to test this idea. However, until such evidence is found, we will assume that the cosmological principle applies throughout the universe.)

In Galaxies, we hinted that when we think of the expansion of the universe, it is more correct to think of space itself stretching rather than of galaxies moving through static space. Nevertheless, we have since been discussing the redshifts of galaxies as if they resulted from the motion of the galaxies themselves.

Now, however, it is time to finally put such simplistic notions behind us and take a more sophisticated look at the cosmic expansion. Recall from our discussion of Einstein’s theory of general relativity (in the chapter on Black Holes and Curved Spacetime) that space—or, more precisely, spacetime—is not a mere backdrop to the action of the universe, as Newton thought. Rather, it is an active participant—affected by and in turn affecting the matter and energy in the universe.

Since the expansion of the universe is the stretching of all spacetime, all points in the universe are stretching together. Thus, the expansion began everywhere at once. Unfortunately for tourist agencies of the future, there is no location you can visit where the stretching of space began or where we can say that the Big Bang happened.

To describe just how space stretches, we say the cosmic expansion causes the universe to undergo a uniform change in scale over time. By scale we mean, for example, the distance between two clusters of galaxies. It is customary to represent the scale by the factor R if R doubles, then the distance between the clusters has doubled. Since the universe is expanding at the same rate everywhere, the change in R tells us how much it has expanded (or contracted) at any given time. For a static universe, R would be constant as time passes. In an expanding universe, R increases with time.

Figure 1. Expansion and Redshift: As an elastic surface expands, a wave on its surface stretches. For light waves, the increase in wavelength would be seen as a redshift.

If it is space that is stretching rather than galaxies moving through space, then why do the galaxies show redshifts in their spectra? When you were young and naïve—a few chapters ago—it was fine to discuss the redshifts of distant galaxies as if they resulted from their motion away from us. But now that you are an older and wiser student of cosmology, this view will simply not do.

A more accurate view of the redshifts of galaxies is that the light waves are stretched by the stretching of the space they travel through. Think about the light from a remote galaxy. As it moves away from its source, the light has to travel through space. If space is stretching during all the time the light is traveling, the light waves will be stretched as well. A redshift is a stretching of waves—the wavelength of each wave increases (Figure 1). Light from more distant galaxies travels for more time than light from closer ones. This means that the light has stretched more than light from closer ones and thus shows a greater redshift.

Thus, what the measured redshift of light from an object is telling us is how much the universe has expanded since the light left the object. If the universe has expanded by a factor of 2, then the wavelength of the light (and all electromagnetic waves from the same source) will have doubled.

## The expanding universe

In 1929, an American astronomer working at the Mt. Wilson Observatory in southern California made an important contribution to the discussion of the nature of the universe. Edwin Hubble had been at Mt. Wilson for 10 years, measuring the distances to galaxies, among other things. In the 1920s, he was working with Milton Humason, a high school dropout and assistant at the observatory. Hubble and Humason plotted the distances they had calculated for 46 different galaxies against Slipher's recession velocity and found a linear relationship (see Figure 6) (Hubble, 1929).

Figure 6: The original Hubble diagram. The relative velocity of galaxies (in km/sec) is plotted against distance to that galaxy (in parsecs a parsec is 3.26 light years). The slope of the line drawn through the points gives the rate of expansion of the universe (the Hubble Constant). (Originally Figure 1, from "A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae," Proceedings of the National Academy of Sciences, Volume 15, Issue 3, 1929: p. 172. © Huntington Library, San Marino, CA.) image © The Huntington Library

In other words, their graph showed that more distant galaxies were receding faster than closer ones, confirming the idea that the universe was indeed expanding. This relationship, now referred to as Hubble's Law, allowed them to calculate the rate of expansion as a function of distance from the slope of the line in the graph. This rate term is now referred to as the Hubble constant. Hubble's initial value for the expansion rate was 500 km/sec/Megaparsec, or about 160 km/sec per million-light-years.

Knowing the rate at which the universe is expanding, one can calculate the age of the universe by in essence "tracing back" the most distant objects in the universe to their point of origin. Using his initial value for the expansion rate and the measured distance of the galaxies, Hubble and Humason calculated the age of the universe to be approximately 2 billion years. Unfortunately, the calculation was inconsistent with lines of evidence from other investigations. By the time Hubble made his discovery, geologists had used radioactive dating techniques to calculate the age of Earth at about 3 billion years (Rutherford, 1929) – or older than the universe itself! Hubble had followed the process of science, so what was the problem?

Even laws and constants are subject to revision in science. It soon became clear that there was a problem in the way that Hubble had calculated his constant. In the 1940s, a German astronomer named Walter Baade took advantage of the blackouts that were ordered in response to potential attacks during World War II and used the Mt. Wilson Observatory in Arizona to look at several objects that Hubble had interpreted as single stars. With darker surrounding skies, Baade realized that these objects were, in fact, groups of stars, and each was fainter, and thus more distant, than Hubble had calculated. Baade doubled the distance to these objects, and in turn halved the Hubble constant and doubled the age of the universe. In 1953, the American astronomer Allan Sandage, who had studied under Baade, looked in more detail at the brightness of stars and how that varied with distance. Sandage further revised the constant, and his estimate of 75 km/sec/Megaparsec is close to our modern day estimate of the Hubble constant of 72 km/sec/Megaparsec, which places the age of the universe at 12 to 14 billion years old.

The new estimates developed by Baade and Sandage did not negate what Hubble had done (it is still called the Hubble constant, after all), but they revised it based on new knowledge. The lasting knowledge of science is rarely the work of an individual, as building on the work of others is a critical component of the process of science. Hubble's findings would have been limited to some interesting data on the distance to various stars had it not also built on, and incorporated, the work of Slipher. Similarly, Baade and Sandage's contribution were no less significant because they "simply" refined Hubble's earlier work.

Since the 1950s, other means of calculating the age of the universe have been developed. For example, there are now methods for dating the age of the stars, and the oldest stars date to approximately 13.2 billion years ago (Frebel et al., 2007). The Wilkinson Microwave Anisotropy Probe is collecting data on cosmic microwave background radiation (Figure 7). Using these data in conjunction with Einstein's theory of general relativity, scientists have calculated the age of the universe at 13.7 ± 0.2 billion years old (Spergel et al., 2003). The convergence of multiple lines of evidence on a single explanation is what creates the solid foundation of scientific knowledge.

Figure 7: Visual representation of the cosmic microwave background radiation, and the temperature differences indicated by that radiation, as collected by the Wilkinson Microwave Anisotropy Probe. image © NASA/WMAP Science Team

Major ideas in science are rarely the work of

## Question Edgeless universe?

You will probably get a lot of variety in replies.
I don't think you will meet yourself coming back.

I will kick off with one idea I had long ago. If you got to the edge of the Universe (whatever that may mean) there is nothing beyond. If you set off away from the Universe you would become the edge of the Universe. In other words you need a frame of reference. The 'edge' of the Universe must be defined by something. A star ? ? ? whatever. When you set off beyond, you become the new defining point.

You will get more sophisticated replies (maybe including one from me) but I thought I would kick off with a simple one.

Enjoy your visits here. Look through the topics.

#### David-J-Franks

FYI folks. How Big Is the Universe? The answer provided in this report "We can only see a tiny, little bubble of [the universe]. And what's outside of that? We don't really know," Kinney said. But by calculating the size of that little bubble, scientists can estimate what's outside of it. Scientists know that the universe is 13.8 billion years old, give or take a few hundred million years. That means that an object whose light has taken 13.8 billion years to reach us should be the very farthest object we can see. You might be tempted to think that gives us an easy answer for the size of the universe: 13.8 billion light-years. But keep in mind that the universe is also continuously expanding at an increasing rate. In the amount of time that light has taken to reach us, the edge of the bubble has moved. Luckily, scientists know just how far it's moved: 46.5 billion light-years away, based on calculations of universe’s expansion since the big bang."

My observation. The 46.5 billion LY distance comes from the comoving radial distance since the BB using z=1000 or more for the redshift of the CMBR. COSMOLOGY CALCULATORS However, David, Cat, et al. My telescopes cannot see anything that far away ---Rod

#### David-J-Franks

First of all, I would like to suggest that the dictionary definition of the universe, ie "it is everything there is", is out of date, I suggest it was thought of well before the big bang model. This definition doesn't allow for multiple or infinite other universes or multiverse theories etc. So, I would like to add to this thread with some of my own personal ideas.

Our universe started with a finite size, it has a finite rate of expansion and a finite age, so it must now have a finite size. I now treat the universe as an object. Objects exist in a space, they don't create all of space. I think the space our universe is in must be infinite, I call this space 'The Infinite'. So, I now see 'The Infinite' as 'everything there is'.

I also believe nature does not allow one-off processes, if it's possible once then it's always possible. The big bang was a natural process, so, given an infinite space as in 'The Infinite', there must be an infinite number of universes.

So, my answer to your question is that the universe is expanding into the space of 'The Infinite'. Space is a tangible 'something' such as quantum field/foam/fluctuations, vacuum energy, dark energy etc, it's not a void. So as well as expanding into space, space also came out of the big bang along with its matter and energy

#### Catastrophe

##### Approaching asteroid? Is this THE one?

I shouted "Thank rod for that".
My wife thought I shouted "Thank god for that"
I said "Not much difference",

He frightens away the nasties.

#### Catastrophe

##### Approaching asteroid? Is this THE one?

"If it has a finite size there must be a beyond"

A perfect example of anthropomorphic delusion.

You can take a horse to water but you cannot make it drink.
(Old proverb).

#### David-J-Franks

I shouted "Thank rod for that".
My wife thought I shouted "Thank god for that"
I said "Not much difference",

He frightens away the nasties.

Last night you appear to have called me ignorant and stupid. You or a moderator has since removed it. Here is a copy of the wording from that post for all to see. It's obvious that post was directed at me because I was the only one posting at that time and it came very soon after my posts.

"There is a word for playing around with something to please one's own ignorance..

I seem to have forgotten what it is."

Also, looks like you are calling me nasty, again obviously directed at me for the same reasons as above.

If you don't agree with my ideas please say why, or direct me to better information, or suggest your own ideas, even make fun of it, as you have done with Kabones question, but please don't call me stupid, ignorant and nasty.

It would also help others by saying why you think my ideas are wrong, rather than calling me stupid in the form of a riddle.

I stayed up extra late to write my posts, so I saw your posts last thing, and so went to bed hurt and disappointed.

I got up this morning with my mind churning around thinking how to reply, only to find the post removed. Whoever removed it, shows it was out of order.

#### David-J-Franks

"If it has a finite size there must be a beyond"

A perfect example of anthropomorphic delusion.

You can take a horse to water but you cannot make it drink.
(Old proverb).

To add insult to injury, you're now suggesting I'm deluded. Again, it would help everyone if you say why my ideas are a delusion, rather than calling me deluded.

In my opinion, it is a perfect example of arrogance to ridicule peoples ideas (again with riddles) without giving a reason.

#### Wolfshadw

The post was removed by the person who wrote the post.

I will caution all parties to remain respectful in your responses.

#### David-J-Franks

"The point is that the Universe is complete. By definition there is nothing beyond."

Now take that on board please

One of the most mainstream ideas at the moment is the 'Eternal Inflation' model of the big bang. This has it that bubble universes are continuously popping into existence out of an eternal inflation field. OUR universe is one such bubble of an infinite number of other bubble universes.

There are many other theories which postulate multiple or infinite other universes.

According to this theory and others, and to continue in the tone of your post

OUR universe is NOT complete it is NOT 'everything there is', so accordingly there IS a beyond.

The word now to describe 'everything there is' becomes 'The Multiverse' not 'The Universe'

Now take that on board, please

#### David-J-Franks

The post was removed by the person who wrote the post.

I will caution all parties to remain respectful in your responses.

Thank you for that information, I wrote my reply to Catastrophe in the most respectful way my English would allow, for example using words such as 'appears to' and 'looks like', just in case I had misinterpreted his riddles. But I hope everyone can understand that I had to reply. For that reason thankyou for not deleting my post.

I've had great respect for Catastrophe, we've had many great conversions.

My latest reply to Catastrophe was a little acidic as I hit the reply button before I saw your post.

Anyway, back to normal now.

#### David-J-Franks

Without researching I' under the impression that the maths has several possibilities space can be flat, or with positive or negative curvature or with enough curvature to form a closed space, which I guess you are alluding to. If you believe in this closed space, then yes you will always come back to your starting point, or see the same galaxy whichever way you go round.

To the best of my knowledge, I think the best measurements so far of the universe point to it being flat with a good degree of accuracy. The error in these readings also suggest minimum size of the Whole Universe to be 250 times the size of the Observable Universe. For if it were smaller than this then our instruments would be sensitive enough to detect an unevenness with space.

#### David-J-Franks

QUOTE
If I start out in the opposite direction eventually I will also get to the galaxy.
QUOTE

To put it politely. this is "blowing in the wind".

The Universe is a large place. You don't have a compass. You don't have a spacesuit. You don't have FLT. You are not immortal.

Your premise is leaking badly.

#### David-J-Franks

Great, yes the universe is a sphere, but we live inside it, a 3D space. We are not flatlanders walking around the surface of it. Therefore, isn't there an inside and outside to it?

I'm guessing here that Kabone means the edge of the universe is the surface of this sphere?

#### David-J-Franks

Good. I can be my nice friendly self

Sorry, but I still have the same problem. An edgeless Universe is directly analogous to the seamless surface on a sphere. As you say, if you accept this analogy, you start at a point, say Quito which is virtually on the Equator. Set off in a straight line, which is actually the curved Equator, and you get back to Quito. A "straight" line from Quito can now be to the Moon, but this would be an extra dimension for the flatlander confined to the surface of the sphere. Do not be confused by my analogy of the Earth. I assume we can agree all that?
Now if the Universe is the sphere in the analogy, as the Universe expands the surface of the sphere expands. We, as flatlanders, cannot get off the surface of the sphere = Universe. The distance between us increases but we are still on the "surface".
The problem is we are trying to relate mere humans to the whole Universe, about which we know next to nothing. What the Universe is expanding into, is a non-question. The big problem I have with the Expanding Universe" is that we (objects) are not expanding with it. If ALL were expanding we would not know it, since our rulers would be expanding too. That, I believe, is a flaw in the Expansion theory. By analogy, the surface of the sphere = galaxy and the "into" bit relates to the expansion of the surface. No, you will say, it is expanding "outwards". You are correct, but that is a different dimension unknown to the flatlander. That dimension is unknown to us and it is not the "into" in your question: "Into what is the Universe expanding. Your answer is: "The Universe, as a surface, is expanding. Expansion perpendicular to that surface is in a dimension we cannot detect. It is not in a space dimension familiar to us. Any attempt o make it so is anthropomorphic.

I hope that helps. I am very happy to continue the discussion

This seems like a good description of closed space such as Kabone is enquiring about, except instead of Quito he's using galaxies. So I'm puzzled why there's a misunderstanding between you both?

Where not flatlanders, so wouldn't a more useful analogy be that we live inside the 3D space of your sphere? then we can move around inside and outside of the sphere, and the surface of the sphere becomes the edge of the universe. So as the universe expands the sphere gets bigger and things inside still move apart. Whatsmore it now gives meaning to what the universe is expanding into. Any good?

#### David-J-Franks

David-J-Franks, Catastrophe, et al. I see references to eternal inflation and the multiverse. Here is a 14-May report some may find interesting. The Founder of Cosmic Inflation Theory on Cosmology's Next Big Ideas, "Physicist Alan Guth, the father of cosmic inflation theory, describes emerging ideas about where our universe comes from, what else is out there, and what caused it to exist in the first place."

The brief report has some interesting graphs. This *origin model* uses repulsive gravity force *in the beginning* and space expanding > 1E+20 c. There are those in science who live for theory, I enjoy the practical side of the scientific method. What we can observe and verify like Galileo could show others the tiny lights moving around Jupiter when debating the geocentric astronomy teachers. Quantum mechanics has verifiable observations based upon experiments conducted in laboratories, so does the heliocentric solar system astronomy. I do not consider that inflation, multiverse, and eternal inflation theories or string theory is on the same scientific level of verification (95+% confidence level for example) as particle experiments in QM or heliocentric solar system astronomy or for example, exoplanet studies.---Rod

#### David-J-Franks

"If it has a finite size there must be a beyond"

A perfect example of anthropomorphic delusion.

You can take a horse to water but you cannot make it drink.
(Old proverb).

#### Catastrophe

##### Approaching asteroid? Is this THE one?

You should know that I am a peaceable person. I am very sorry that things went awry round about posts 30-35 and I will say publicly that I regret anything that made you upset.
If this: "Have we found the edge of the Universe? All About Space May 2020 pp 40-46 had appeared sooner, I would have pointed you to it and probably retired from the thread.
Sadly, we both got involved in IMHO silly squabbles about the meaning of inside and outside and up down and around (figuratively speaking) and completely "lost the plot".
Not wishing to spoil the tone of this post, I would ask you politely to please re-read the Quito analogy section.
I, for one, would be very happy if we can continue this thread in a positive manner, without words of war and exaggerated misunderstandings,
Wishing you health and happiness in these difficult times

#### Catastrophe

##### Approaching asteroid? Is this THE one?

"So why don't you think there is a boundary (edge) and a beyond for the universe?"

I will now do my best to answer your question in a polite and constructive manner. By that, I am conveying that it will be polite, and I will try to answer it in an understandable way.

As you will see, there are many views in the article quoted. All about Space, Issue 104. There are unknowable things in the Universe and this may be one of them. My personal view is that there are problems of semantics. Our vocabularies (I include all humanity's) are incapable of describing certain issues. This may be one of them and, I believe this was the root of our communication difficulties. I would point you here to the science of General Semantics as introduced in Science and Sanity by Alfred Korzybski.

You mention straight lines and meeting yourself etcetera. I will not go back to my view that if you propose impossible starting conditions, such as being at the edge of the Universe (Who knows where that is, etc,) you will not get productive answers,. Take that off the table.

Let us assume you are at Quito. Your 'straight line' is around the Equator, governed by gravity. If you take the flatlander analogy, this means that you do return to your starting position - Quito. If you apply that to the Universe (or our universe, if you prefer - that is irrelevant in this example), and if the Universe is circular then you will return to the same place Not mentioning that there is no way whatsoever to know where that place is / was. Meeting yourself in Quito is not actually possible, but you could have left a marker saying "I was here". So your argument stands, there. Going around 'our universe' there is no way to identify that location.

Let me go back to the Quito analogy. If we were flatlanders, and all this stuff is widely discussed and available, we would behave and return exactly as you described.

Now, to the flatlander, there is no 3rd space dimension. He (or she, hereinafter assumed) has no appreciation of what we call our 3rd space dimension. There is no edge to his universe.

Whilst not engaging in the flatlander assumption, I quote from the article referenced above:

QUOTE
There is no current reason to suspect that the Universe ends with our cosmic horizon, just as we know that the Earth doesn’t end just because the rest of the planet is hidden from view by its curvature.
QUOTE

If we return to our flatlander analogy, we can say that the flatlander will know of the existence of the surface of the sphere, which will be the whole discoverable universe to him (granted it continues in a 3rd time dimension).

We know that the flatlander has no spatial sense to discover a non-existant (to him) 3rd space dimension. He may face the same dilemma that we face, namely that if his universe is expanding (as ours may be) then distances on the surface will increase, measured by his local measuring sticks.

INTERPOLATION begins
We do not know why this happens. If everything were to expand, including our rulers, then our measurements of the Universe would show no expansion. If we measure a table in our living room and it measures 4 feet and it expands x 2, our rulers tell us 8 feet. If the ruler itself also expanded x 2, then the table would measure 4 new (or x 2 expanded) feet.
INTERPOLATION ends

Now, don’t forget that the flatlander cannot perceive a dimension perpendicular to his sphere or, more correctly, to the surface of his sphere. He cannot perceive inside or outside that surface. (Leaving aside his time dimension). If we are super beings with that extra perception , we can say that his universe is expanding - the radius of his universe is increasing as well as the area of his universe. His universe has no edge. He is totally unware of expansion perpendicular to his surface.
His universe is limited to the surface of a sphere which has no edge.

If you, as a superbeing, can postulate that his universe as seen by us has an edge which is the two-dimensional surface of his world. I would not consider this assertion to be safe – others might. Please see Korzybski below.

Coming back to the flatlander, whilst we can postulate ‘an outside’ which allows expansion along the radius as well as expansion of the area (being his entire universe) he does not have the sensory equipment or understanding to operatementally.

If you now postulate that we are living in a closed universe, we have directly analogous limitations. There may be expansion of the Universe in some postulated dimension that we do not have the sensory equipment to understand, and some super being with extra senses may say that there is ‘an outside’ into which our Universe is impinging but these observations are not open to us and we cannot perceive an edge or an outside. It is meaningless to contrive some combination of words which endeavours to circumvent this.

It is a shame that General Semantics is not a compulsory subject in schools. Its catch phrase is The map not the territory. In this case it would be immediately visible to the GS student that to use words to describe an imaginary event is futile. The map (the words, the verbal description) IS not the territory (the reality). You cannot create a reality just by wrapping words around a verbal assertion.

QUESTION
"So why don't you think there is a boundary (edge) and a beyond for the universe?"

RESPONSE
Such a thing is unknowable to any being with the limitations imposed upon us by our physical makeup.
Any such enquiry is exacerbated by introducing assumptions of conditions unattainable in reality e.g., reaching an assumed edge of the Universe and possibly returning to it.

Mr. Franks.
I hope you will agree that I have taken a lot of time writing the above, and that it contains no criticism (explicit or implicit) of your good self. My motivation has been to explain and reply to your final stated question. I hope that I have succeeded in this and that you may have benefited from my efforts. Nevertheless, if I have not achieved that result, then I am sorry for my failure and I am willing to do my best to answer any further points you may wish to raise. The offer is of course open to any other members who may wish to join in.