Shape of the Universe Determined To Be Really, Really Flat 235
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.
Kansas isn't even remotely flat (Score:4, Funny)
Not sure what OP is on about.
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On average, this orange is actually a singularity!
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You're thinking of Missouri.
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The Earth is not flat therefore Kansas is not flat.
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Native Kansan here so I don't get to say this often... you wrong.
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Native Kansan here, too.
The state's only flat if you discount the Eastern third.
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Native Kansan here, too.
The state's only flat if you discount the Eastern third.
Well, yeah; but a pancake scaled up to the size of Kansas is even rougher around the edges, by several orders of magnitude.
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In the same vein, if you made a perfect scale model of the Earth the size of a billiard ball, it would almost meet manufacturing standards for a billiard ball.
Re:Kansas isn't even remotely flat (Score:5, Insightful)
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As a Coloradan, eastern Colorado is more featureless and boring to drive through than western Kansas. Eastern Kansas looks like Missouri and is actually quite pretty.
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What you maroons[] are missing is that there was a study on the flatness of states that was on the nerd news sites recently, and Kansas was not even close to winning. States like Florida are much, much flatter. Kansas is actually rolling hills, even in the part of the State people like to claim as being flat. Just find a topo map.
https://www.google.com/maps/pl... [google.com]
Anywhere you zoom in, rolling hills. Flat areas are just small patches between hills. The hills are mostly the same height, so it looks pretty flat
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In non-Euclidean, elliptical geometry the surface of a sphere is by definition flat.
Re:Kansas isn't even remotely flat (Score:5, Insightful)
Kansas by all accounts defies spherical topology to achieve the Platonic Ideal of flat. The universe is just a shadow of Kansas seen on a cave wall.
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But the real question is: How flat is that cave wall?
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Just figure out the source of the shadows, right?
Re:Kansas isn't even remotely flat (Score:5, Funny)
Little known fact, the first part of The Wizard of Oz was also in color, it's just that Kansas is actually sepia tone.
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complete logic fail. http://en.wikipedia.org/wiki/Fallacy_of_the_undistributed_middle
you argue every area on the surface of a sphere has constant curvature
kansas is on the surface of a sphere
therefore kansas has constant curvature, and
therefore kansas is not flat.
here are the three ways this fails
(1) you did not demonstrate that the earth is a sphere, therefore it could have flat spots, and
(2) you assumed the euclidian definition of "flat"; there are other geometries
(3) setting aside (2) you do not demons
Re:Kansas isn't even remotely flat (Score:5, Informative)
Actually I would argue that when we say that part of the Earth (like the ocean) is flat, we mean that it follows the shape of the WGS84 oblate spheroid [wikipedia.org], whereas an area the size of Kansas which was geometrically flat would look to us like a bowl, with its centre lower in gravitational terms than its perimeter.
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I've driven clear across Kansas on US-50. The Western part of Kansas is ridiculously flat. In fact, that observation was the most memorable part of that portion of my trip. I kept wondering what geologic processes could produce such an even change in elevation. It's basically a huge geometric plane (also once a plain, obviously) at a few degrees slope, starting from just about the Colorado border and continuing for much of the state. The political border with Colorado, though it appears quite arbitrary on a
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I kept wondering what geologic processes could produce such an even change in elevation.
It (along with eastern Colorado and much of the other great plains states/provinces) is an old sea bed, the floor of the central inland waterway in the mid/late Cretaceous. Flat from millions of years of sediments, tilted slightly from being pushed up as the continent drifts westward. (Dramatically so at the Rockies). The foothills of the Colorado Rockies do not "end just short of the border" at least not anywhere
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A Dutch universe ! (Score:2, Funny)
Will wormholes work FTL in this flat universe? (Score:2, Interesting)
If its surface is flat, what good a wormhole will do?
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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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3) How not to destroy all life in the universe when magically altering the shape of the universe on cosmological scales.
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The cosmologists are using a different definition of flat than your common usage. A piece of paper is flat even when you fold it.
Take a look here http://en.wikipedia.org/wiki/G... [wikipedia.org]
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The universe appears flat at large scales. It isn't flat on small scales, as evidenced by gravitational lensing by massive objects. Wormholes probably don't exist, but if they do then they just affect the small scale structure of the universe, not the large scale.
Body of Christ! (Score:2, Funny)
The universe is a communion wafer.
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Nope. It's a Discworld on the back of a turtle.
Multiverse, somebody has it (Score:4, Funny)
So, who are the lucky bastards who get the Dolly Parton universe?
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So, who are the lucky bastards who get the Dolly Parton universe?
Presumably, those are the alternative slasdotters that are married to the opposite sex and don't live in the basement either.
- or we are just very small? (Score:5, Interesting)
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.
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Also, if space isn't curved then where are we getting all that background heat from? There's a vast amount of it, 3K just about everywhere needs a bit of warming up, and if it's not being bounced back at us then where is it coming from?
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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?
The Big Bang didn't happen at a single point.
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The Big Bang didn't happen at a single point.
Well, actually we don't know that. That's an extrapolation based on math which breaks down if you get too close to the moment of the big bang. (If 'moment' is even the right word.)
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The Big Bang didn't happen at a single point.
Well, actually we don't know that. That's an extrapolation based on math which breaks down if you get too close to the moment of the big bang. (If 'moment' is even the right word.)
No, we do know that, from the Cosmic Microwave Background. The early universe has been directly observed to be extremely homogeneous.
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No, we do know that, from the Cosmic Microwave Background. The early universe has been directly observed to be extremely homogeneous.
No, we really don't know that. The CMB is exactly the proof you're looking for. If all of its photons were emitted when space itself was very, very small, and space is now very, very big, it would indeed appear very homogeneous, and very very redshifted. The only real argument against it happening at a single point is that QED says that just doesn't work for them- but then again, they've always hated singularities, and I somewhat agree with them. But they're not arguing that it didn't happen at nearly a sin
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We do know that. The CMBR demonstrates thatvery fact.
The Big Bang was not an explosion. It had no epicenter. The entire universe; including space itself, expanded.
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No cosmologist thinks the universe was just a single point in size. This is an error in how the big bang is explained to the public. Also, it is error-prone to try to compare the rate of expansion of the universe to the speed of light. These things are not comparable. The expansion of the universe is a scaling of the universe. For example, in one second, 1 meter becomes 2 meters. Then 1 parsec becomes 2 parsecs. You can't compare this to a speed. 1 meter going to 2 meters in one second is a lot slower than
A flat universe is not conclusion of the article (Score:5, Informative)
Re:A flat universe is not conclusion of the articl (Score:5, Insightful)
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.
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We can see almost all the observable universe, from now until just a few hundred million years after the big bang. In other words, we can see most of the universe that there will ever be to see.
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It's called inductive reasoning. And it's the basis of all science.
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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.
An explanation: The universe is a hologram (Score:3)
And Then ? (Score:2)
Examining explosions in a vacuum (Score:2)
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What we know about explosions at any scale tells us nothing about the Big Bang, which was not an explosion.
O'Rlyeh? (Score:2)
http://i.imgur.com/1nSMqI4.png [imgur.com]
It was further determined... (Score:2)
Flatter than Kansas? (Score:5, Funny)
Which means it's probably even flatter than Kansas.
The band or the state?
Curved in what? (Score:2)
Seriously I don't get it, are they saying there are more dimensions?
The article shows images of 2d things being wrapped around 3d things. So are they not saying by extension that our 3d universe is potentially wrapped in more dimensions, otherwise how could it be anything other than 3d.
And a 2d universe can't bend because it is a f**king 2d universe otherwise it wouldn't be a ruddy 2d universe it'd be a 3d universe.
This sh*t doesn't make any sense.
Re:And probably infinite (Score:5, Interesting)
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.
Re:And probably infinite (Score:5, Insightful)
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.
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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.
The observable universe has to be sufficiently big for a planet like us to form, so that puts a lower bound on it.
But if the size of the whole universe really is random, then it seems likely that it's far larger than the observable, no?
Or are there any theoretical upper bounds I'm not familiar with?
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My experience with predominately three dimensional entities tells me that when they say that the universe is infinite in size, they are referring to the length, breath, and width of the "normal" dimensions they are used to dealing with. It is quite possible to have a multidimensional universe that is infinite in a few of the dimensions without being infinite in all of them.
You have to look at the big picture (so to speak).
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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.
Inflation already answers that question (assuming it turns out to be true). Even a very non-flat universe becomes apparently flat if you massively inflate it (in much the same way as the Earth appears flat to people on it because it's incredibly large compared to our perception of it).
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While there have been inflation models tuned to exactly that, all that does is move the "fine tuning", it's not really any more satisfactory. However, if any such theory works out to exactly explain dark energy I'll be impressed! There's lot of work going on there, but nothing impressive yet.
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Inflation doesn't require tuning, all it requires is that the amount of inflation is large enough to explain the observed flatness (as well as CMB thermal equilibrium and lack of magnetic monopoles, which again just means it has to be greater than a given amount). The fact it doesn't require tuning (as far as we know) is a large part of the appeal of inflation as a theory in the first place.
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There's plenty of criticism of the amount of tuning required for inflationary models. When you're tuning the model so that the bubbles grow just fast enough, and stop at just the right time, to give us the universe we see, you're just moving the problem. But I'm not an expert on this stuff, all I know is that many experts are dissatisfied.
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This argument suggests that if the universe is finite, it is very, very much bigger than our observable universe.
Flat does not imply infinite. (Score:4, Interesting)
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.
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There are apparently a large number of flat closed* topologies for 3D space, each of which would show a different sort of repeating pattern in the CMBR - some quite subtle. I think in the 90s and early 2000s there was a group of cosmologists cataloging hundreds of possible universe topologies, open and closed, and what each would look like in the CMBR. As the detailed CMBR data came in, none of that was found. Poor cosmologists - the work is valuable in showing they were wrong, but you don't build a grea
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oops: *universe topologies, flat and curved
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The problem with a torus is that it is not isotropic. So we probably don't live in one.
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If we assume that the universe is spatially isotropic (which implies homogeneous), it really cuts down on the possible shapes. If we assume it is also orientable (which only matters if our universe is finite), then there really are only a few options. As far as I know, these are: infinite flat Euclidean space, positively curved finite 3-sphere (3d analog of a normal sphere which is just the surface of a ball), and negatively curved infinite hyperbolic space.
I think the universe must be orientable because th
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I think the universe must be orientable because there is experimental evidence of CP symmetry breaking. Which means if the universe is nonorientable, it must flip charge, parity, and time or disagree with experiment. Hard to see how time can become flipped by making a trip around the universe, with homogeneity and the second law of thermodynamics being held everywhere.
Can you explain this more? By a "trip around the universe" do you mean in the sense of a trip around a Mobius strip? As the universe is seeming growing too fast to allow that, I'm not sure you can argue from that. Or are you thinking of some experiment that some high-tech culture could actually perform?
We consistently find that our extrapolations about the universe from experiments we can perform don't turn out to agree with new data when we get to it (and thank goodness, or science would be "done" and
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The universe does appear to be infinite, but it will take infinite evidence to establish that as a fact
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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.
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The most meaningful discussion this post generated was one regarding the flatness of the state of Kansas.
With all due respect to Ms Knightly, her lack of buxomness while exercising is about the least interesting thing to discuss at this point.
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How is this fitting with Big Bang? Should not a round universe be shaped?
If you spill a drop of coffee on a piece of paper, the stain will expand to form a circle. The paper is still flat or otherwise an elliptic or otherwise non-circular stain would have formed.
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Are all the turtles flat, or just the first one?
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Read more about it on my blog, Starts with a Bump on the Head, which, as you may have guessed from the title, is written in atrophic dactylic tetrameter, like all good cosmological monographs and comic books.
i couldn't understand the jargon, but love the pictures
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You've made a mistake, I combined those things and got a wind-up alarm clock plus one universe. Hence my superior theory of Intelligent Winder Design, and a better way to jerk off in this universe.
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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 infin
Re:Let's just humour them (Score:5, Informative)
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.
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Considering how uninformed journalists are, it's not surprising that the nuance of 'know' versus 'reasonably confident based on evidence to date' is lost on them.
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Considering how uninformed journalists are, it's not surprising that the nuance of 'know' versus 'reasonably confident based on evidence to date' is lost on them.
Have you folks ever noticed on some of the whackier science shows, that when they get to parts that you know something about, how often they are just plain wrong?
It's a pity when we have alot of the public thinking that "Ancient Aliens" is a science show.
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And don't forget the BC vs. BCE confusion.
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Hum, I believe the problem is that most of the world is not christian, but they would still like to be able to refer to the year according to the Gregorian calendar, since it is almost universally used.
AD is kinda heavy for non-christians; it means in full "Anno Domini Nostri Iesu Christi", or in english "In the Year of Our Lord Jesus Christ", so if you are very pedantic writing 2015 AD is actually a lie for them.
What do you suggest the Chinese and Japanese to do, for example?
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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?
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Humm, both did get royally fucked by christian powers. Still wasn't enough to get them to use AD, though ;p
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therefore around 4004 b.c.e.
In my limited experience with the acronyms "BCE" and "CE", they're mostly used by atheist intellectuals that arrogantly mock religious types.
Yup, your experience is pretty limited. The problem with Before/Christ, and AD (Anno Domini) is threefold, not th eleast that you have a before and after something, yet th before, is BC and the afterwards is AD, so there is a marked inconsistency. If we use BC, one might think either AC, or BD might be an appropriate reference.
Another is that christians do not own the world. There are many people of many religions - or none at all - who are scientists, and it's quite a conceit for christians to demand t
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all seem to understand and propagate this concept that scientists treat Science as a religion. It's like some sort of projection thing.
I think its the old adage of when your tool is a hammer, everything lookd like a nail. It's an inability to accept that everyone does not think in the same manner as they do. They cannot imagine not having a religion, so they likewise cannot imagine anyone imagining elsewise.
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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.
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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 m
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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.
Why would any scientist do that? They would merely point right here, just like any scientist anywhere else would. There is no center of the big bang, we are the center along with every other point.
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.
No, I don't think we have any clue what really happened during it, or even for a significant amount of time after it. But we have pretty solid evidence that it happened. The metric expansion of space is happening, and the CMB is there just like it should have been. It comes from all directions in space, just like
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You are talking about the observable universe. The actual universe is either infinite or looping, by definition. As for the origin of the big bang, it is only a single point in the observable universe. In the actual universe, the big bang happened everywhere.
When scientists talk about the universe, they usually mean the observable universe because as you said, there is no way to know what's beyond it.
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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.
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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 u
That was gravitational waves from inflation (Score:3)
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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?
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!NASA, ESA.