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Shape of the Universe Determined To Be Really, Really Flat
StartsWithABang writes: You might imagine all sorts of possibilities for how the Universe could have been shaped: positively curved like a higher-dimensional sphere, negatively curved like a higher-dimensional saddle, folded back on itself like a donut/torus, or spatially flat on the largest scales, like a giant Cartesian grid. Yet only one of these possibilities matches up with our observations, something we can probe simply by using our knowledge of how light travels in both flat and curved space, and measuring the CMB, the source of the most distant light in the Universe. The result? A Universe that's so incredibly flat, it's indistinguishable from perfection. Which means it's probably even flatter than Kansas.
Not sure what OP is on about.
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The universe is a communion wafer.
So, who are the lucky bastards who get the Dolly Parton universe?
Table-ized A.I.
The assumption of GR is that space/time can be described as a smooth manifold - a manifold being intuitively something like a beach ball, donut or similar. Smooth means that when you look at a piece of the manifold at a sufficiently small scale, it looks more and more flat; it really is that simple, what makes it hard is when you introduce the technical tools you need to make precise calculations. So, since we don't actually know the size of the universe, perhaps what we can measure is that we are looking at a much smaller scale than we imagined.
But, some will say, how about the speed of light? The age of the universe is known, so if it started out in the big bang as a single point, it can only be a limited number of lightyears across, right? There are several things to say, that might rock that particular boat a little. Firstly, we don't know that the universe was just a single point in size - in fact, the way QM is interpreted, it seems reasonable to think it wasn't. Secondly, if inflation happened, the universe went through a phase when it expanded a lot faster than the speed of light. And thirdly, of course, the speed of light is only known to be the limit within what we know as vacuum in the space-time we observe now, it only limits how much of the universe we can see now; we have every reason to assume that there is a lot more of it than that.
it seems likely that the universe is infinite.
That's a bit of an overly-strong claim.
* If the universe were smaller than the observable universe, we'd see the recurring patterns in the CMBR (or we'd see the Edge) and we don't, so we know that's not it.
* If the universe were just a bit larger than the observable universe, that would be once heck of a coincidence, so that's probably not it.
* But to distinguish between an infinite universe and one much larger than the observable universe? No way to tell.
Many theories assume the universe to be infinite as that makes the math easier, but all the theories about where the big bang came from are guesswork, and we shouldn't read too much into that.
The real mystery though is how the universe could be very nearly flat (without being exactly flat). Such "fine tuning" is clear evidence we're missing something quite fundamental. But then, dark energy already tells us that.
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That's what I thought too. And the conclusion of the article is 'We don't know the shape of the universe because we can't see far enough.' So the title of this is wrong too.
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The universe is all of space and time. We have not observed/measured/etc. most of the universe yet to determine its shape. The parts of the universe we have observed are flat. Until we observe more of the universe, we will not know if the universe is flat or not.
Choosing the lesser of two evils is a choice for evil.
Here's an explanation: The universe is a hologram
The real mystery though is how the universe could be very nearly flat (without being exactly flat). Such "fine tuning" is clear evidence we're missing something quite fundamental. But then, dark energy already tells us that.
I agree. An observably flat universe is a huge coincidence if there is some force that composes half the mass-energy in the universe that is trying to rip the entire thing apart. Either that is an illusion, or some mechanism forces it to be perfectly balanced out by the other half of the mass-energy of the universe which we think exists but haven't been able to observe. Or, we just happen to be living in the one moment in time where dominance is switching from one to the other, but that seems like quite a coincidence as well.
The universe is all of space and time. We have not observed/measured/etc. most of the universe yet to determine its shape. The parts of the universe we have observed are flat. Until we observe more of the universe, we will not know if the universe is flat or not.
Unless they say otherwise, if you hear physicists talking about the "Universe" they're probably talking about the observable universe.
You fail to understand what scientists know versus what they speculate about.
Making the assumption that they are even somewhat accurate about the big bang (unlikely), the math used to get there breaks down and doesn't work as the size approaches infinitely small. Everything is just speculation from unimaginative scientists who think they know what happened 14 billion years ago at some random spot that they can't even point their finger in the general direction of.
That does not mean that space was not infinitely large while at the same time infinitely small, its all a matter of perspective. Outside looking in, its infinitely small, inside looking out its infinitely large.
Note: We can't get an accurate police report 20 minutes after the event with 20 eye witnesses, but many are dead set that we KNOW what happened during the big bang. When you think about things like this, use your head and think about the police report.
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Everything is just speculation from unimaginative scientists who think they know what happened 14 billion years ago at some random spot that they can't even point their finger in the general direction of.
Good grief, no. Where does this idea of science ultra orthodoxy come from? I haven't worked directly with any cosmologists, but every one says "This is what we think happened. "Know" is a completely different thing, and the only people who "know" how the universe was created use a reference book from the middle east, therefore around 4004 b.c.e.
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
That article and many others missed the point. What they thought they'd seen was evidence for gravitational waves during inflation. There are lots of other reasons to believe inflation happened.
As for the origin of the big bang, it is only a single point in the observable universe.
No, no, no. The Big Bang was not an explosion emanating from a point. The Big Bang happened everywhere at once. It had no center.
Flat does not imply "infinite". I see no reason that it is "likely" the universe is "infinite". "Infinite" in actualized physical terms is meaningless,....
'Infinite' in mathematics is not a meaningless concept, hence the possibilities of applying that maths to the physical universe remain. You probably mean that in your model of things there is no place for this concept.
The problem is, that as far as can be determined, what we have observed, is all that mankind will ever reasonably be able to observe on this matter. So unlike the glass of water above, its like observing 99% of the lake and finding no lochness monster, then concluding there is no lochness monster.
What we have observed is what we can observe, and it may be all that we can ever observe. It does not mean that there is nothing else that can affect us. A better example is of someone stuck in a little cove, observing the ocean from that viewpoint, hence seeing only a fraction of it. As far as that person is concerned there need be nothing else anywhere.
I'd be very interested in reading your paper where you include the math where working through the conceptualization of 'outside looking in'.
I'd certainly be open to other interpretations but they need to be a bit more rigorous than: I fundamentally don't understand the math of modern cosmology so I came up with some new model that's about as complicated as visualizing an inflated balloon.
BTW, your analogy really ought to be 20 cameras not 20 eye witnesses. That's a closer approximation.
I've always wondered...
How is a 3-D project of a 2-D universe different from an intrinsically 3-D universe? How would you tell the difference? And would you care?
What we know about explosions at any scale tells us nothing about the Big Bang, which was not an explosion.
Which means it's probably even flatter than Kansas.
The band or the state?
It must have been something you assimilated. . . .
A mathematical note: Tori can be flat.
If the universe (and here we are talking about the large spacetime structure, not any of the weird tiny compactified extra string dimension stuff) is globally flat, it can still have the structure of a torus.
The torus when viewed as a 2 dimensional space in 3 dimensions, is not flat-- it has some positively curved parts (think the outer edge of the donut) and some negatively curved portions (think the saddle like regions on the inner ring of the torus.) However, the total curvature (when I sum up all contributing curvatures) on the torus is zero. This is related to a mathematical fact that the total curvature of any surface is given by a topological quantity called the genus. In simpler terms, no matter how I deform the torus, the sum of the curvature will be zero. This is very different from the sphere, whose total curvature is always 2\pi.
So, a flat universe would imply that we cannot live on a 4 sphere, because such objects must always have at least some positive curvature. However, there are examples of tori that have no curvature.
In the 2 dimensional case, it is best to see this from the ``Pac-Man'' perspective. The pacman game is played on a flat surface, and whenever you head off the top of the screen, you arrive at the bottom, and whenever you go off the left side of the screen you wind up on the right hand side. This describes a possible shape for the universe, and this shape is the torus! To see this, imagine that you took the playing field, and glue the top and bottom sides together. That would give you a cylinder. Taking the left and right sides and gluing them together would give you a torus. Now that we believe the pacman game is played on a torus, notice that the original interpretation was a flat surface. So , there is a flat representation of the torus.
To avoid some confusion and people trying to draw flat tori in 3 dimensional space, it can't be done. Every surface viewed in 3 dimensional space will necessarily have some positive curvature around its maximal value. Sorry folks!
In fact, of all the 2 dimensional (compact) surfaces, the only one that has a flat representation is the torus. So, if the universe is compact (and 2 dimensional, which seems unlikely,) there is hope for a Pacman world.
You fail to understand what scientists know versus what they speculate about.
Not really. They're very clear about that. It's a requirement of science that you enumerate all of your assumptions, and quantify uncertainties whenever possible.
Making the assumption that they are even somewhat accurate about the big bang (unlikely)
For example, that's not an assumption. The general idea behind the big bang, that the universe was once infinitely small and it expanded, can be used to make certain predictions regarding what you expect to see when you look out in all directions, what you expect to see in the CMB, etc. You can precisely measure how accurate those predictions match up with experiments, and it's really, REALLY accurate.. Check out the text that goes with that graph: "Graph of cosmic microwave background spectrum measured by the FIRAS instrument on the COBE, the most precisely measured black body spectrum in nature. The error bars are too small to be seen even in an enlarged image, and it is impossible to distinguish the observed data from the theoretical curve."
What that boils down to is that your statement about how unlikely it is that scientific theories are "even somewhat accurate about the big bang" is provably an incorrect statement, based on our best available measurements. If you want to make an argument for your case, you need to bring something more to the table than, "I personally feel like scientists are speculating and can't possibly have a high likelyhood of stumbling upon what actually happened." The people you're criticizing have data. You have a feeling. You need to bring in some data, at which point I and everybody else will be glad to accept that our previous theories were wrong. The Lumineferous Ether was accepted theory, but when Michelson and Morley couldn't detect it using their inteferometer, and Einstein showed up with special relativity as an alternative with supporting data gathered from the 1919 solar eclipse, the Ether theory was destroyed. Scientists do not fear being proven wrong. However, you do have to bring evidence with you.
Everything is just speculation from unimaginative scientists who think they know what happened 14 billion years ago at some random spot that they can't even point their finger in the general direction of.
See? You're criticizing a theory that you don't even understand. Scientists can point to you the spot the Big Bang happened, exactly. So can I. It happened where I'm standing right now. At the exact spot that I'm standing. It also happened at the exact same spot you're standing. And at the exact center of the Andromeda galaxy. And exactly at whatever spot you pick at the edges of the milky way. Or any spot at all in the universe: Every spot in the universe is the center of the universe. The Big Bang isn't matter spreading into existing space. The space in which matter exists is expanding. Check out that video, it explains it really well.
That does not mean that space was not infinitely large while at the same time infinitely small, its all a matter of perspective. Outside looking in, its infinitely small, inside looking out its infinitely large.
This right there is the difference between speculation and scientific hypothesis. "Something that looks small from one perspective can look big from another perspective, so whose to say what's infinitely small or infinitely large" is hand-waving. Scientists don't do that. They tell you what they mean by small, and when. At roughly 10^-43 s after the Big Bang, the universe was 10^-35 m. That's the end of the Planck Epock. During the Inflationary Epoch, the universe grew to about 10 cm by 10^-32 s. These numbers are, admittedly by eve
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Let's not think about the very moment the observable universe came to life. t=0 is a mathematical singularity and it messes things up.
Instead we should go back in time and get closer and closer to t=0. If we consider the observable universe as a bubble inside the real, infinite universe, as we go back in time the bubble shrinks, like the rest of the universe. But shrinking something infinite doesn't make it less infinite, so in the end the observable universe will become smaller and smaller while the real universe will stay infinite. As we approach t=0, the observable universe will start to resemble a single point, but this point is still the entire observable universe, not a point inside it.
What do you suggest the Chinese and Japanese to do, for example?
Bow before their christian overlords.
Maybe this can be an adjunct ot Fox News' Ware on Christmas meme.
Athiests war on the God given Dating system
They don't seem to know that the earliest use of Common Era was by Johannes Kepler in 1615.
Anyone care to claim that Kepler was an arrogant atheist?
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.