The universe is geometrically flat?

[IainB]

This post in arstechnica put my head into a spin: Scientific Method/Science & Exploration - Dispatches from the birth of the Universe: sometimes science gets lucky
I had long ago thought it was confirmed - and I could even prove it for myself, with a bit of work - that the earth was round and that it orbits the sun in a sort of dance as the sun spins on its way through space in the Milky Way galaxy as it also moves through space, and the universe is expanding (QED redshift).
But apparently the universe is "geometrically flat"? Argh.
Here's the post copied, minus any links:

Spoiler (click to show/hide)

Dispatches from the birth of the Universe: sometimes science gets lucky
Scientific breakthroughs can come in unexpected ways.
by John Timmer - Jun 3, 2012 6:00 pm UTC
Timeline of the Universe—the expansion of the universe over most of its history has been relatively gradual. The notion that a rapid period "inflation" preceded the Big Bang expansion was first put forth 25 years ago.
NASA picture:
[attach]

[SeraphimLabs]

They said the earth was flat too.

Sure found out the hard way that it wasn't.

Even our best instruments flat out cannot see beyond a certain distance, and even if we could the speed of light dictates that it would take x number of billion years, it's also entirely possible that the universe is in fact larger than we can even detect.

[IainB]

They said the earth was flat too...

Yes, that's what ran through my head as well. But "they" were the religious police of the RC Church.
However, in this case, it is astronomers (of the Galileo Galilei persuasion) who are saying this, and apparently it is substantiated by the readings from the WMAP probe (COBE's follow-up), ...

...which demonstrated that the Universe was flat (along with a number of other things).

This has certainly got me puzzling at any rate!

[cmpm]

as if they know the universe......

my take on the universe
is that it is a reflection of who we are
still exploring that as well

but that's a different look
and not trying to write down an ending conclusion

[Renegade]

I kind of skimmed rather quickly, but don't they mean something along the lines of the geometry of the universe being flat as opposed to being something like a saddle, torus, rippled, or other non-euclidean-space?

e.g. It's perfectly possible that if you go in a straight line, you end up where you started. You're just on a torus or some other shape that would let you do that. e.g. A sphere.

[IainB]

Yes, that's what I thought it might mean, but my knowledge of astronomy is elementary.
I had always thought of the universe as being a sort of expanding ball, with the bits of material in the ball moving away from each other at a great (increasing) rate of knots, making the interstitial spaces greater, over time. (Hence, I gather, at some distant point in the future, from any observation point in the universe, the stars will appear to go out and the night sky will appear to be empty.)
But this doesn't seem to tie in with "geometrically flat", unless the matter is lying all around the circumference of the universe-ball, with a real void in the middle.

DON'T PANIC.

[Deozaan]

Maybe I don't understand the meaning of "geometrically flat" but I thought it was a known fact that the universe was flat.

I remember explaining to a friend about the flatness of the universe back in 2006. She, too, was having trouble comprehending it. I thought I was doing a bad job explaining it, but maybe it is the concept itself that is difficult for some people to understand?

[mahesh2k]

as if they know the universe......

This,

[Paul Keith]

Even if one were to know the universe, I doubt it can be depicted by geometry. (How would you measure a black hole with any form of math besides probability?)

Still...interesting article. Thanks.

[tomos]

Maybe I don't understand the meaning of "geometrically flat" but I thought it was a known fact that the universe was flat.

I remember explaining to a friend about the flatness of the universe back in 2006. She, too, was having trouble comprehending it. I thought I was doing a bad job explaining it, but maybe it is the concept itself that is difficult for some people to understand?

I dont understand it - but I dont know anything about it.
Does it mean there is no third dimension? (I know there are probably other dimensions, but that's hard to grasp too.)

[Renegade]

I was right.

http://en.wikipedia.org/wiki/Shape_of_the_Universe#Flat_universe

And the punch line:

A flat universe can have zero total energy. Thus, physicists suggest a flat universe could come from nothing.

For some illustrations of non-flat geometry, see http://en.wikipedia.org/wiki/Torus.

There are many more.

[IainB]

Here you go  - it's described in NASA's: Universe 101
Time to change paradigms...

[daddydave]

Here you go  - it's described in NASA's: Universe 101
Time to change paradigms...

Is it saying the third dimension exists but it is so disproportionately small, it may as well be flat?

My non-scientific mind finds this consistent with the universe having been pressed into a shape by a giant cookie cutter, handy if you are creating several.

[Paul Keith]

Maybe I don't understand the meaning of "geometrically flat" but I thought it was a known fact that the universe was flat.

I remember explaining to a friend about the flatness of the universe back in 2006. She, too, was having trouble comprehending it. I thought I was doing a bad job explaining it, but maybe it is the concept itself that is difficult for some people to understand?

I dont understand it - but I dont know anything about it.
Does it mean there is no third dimension? (I know there are probably other dimensions, but that's hard to grasp too.)

There will always be a third dimension as you are able to witness a third dimension all around you.

I don't trust WMAPs honestly. All these measurements rely on some faith that what is currently being measured is the same across the entire span of the universe. It'd like trying to measure the entire human body as a tick who judges the universe based on the layers of skin it can penetrate. It might not even know whether it's on a dog or a human so how can it take that into account?

I think another flaw about the flat universe is this thought that something which does not need energy would then introduce concepts within it that does need energy. It's on the same level as saying you're measuring "the magical output" behind an infinite scroll that writes itself and using the current space that the infinite scroll occupies as a measuring stick, you determine the characteristic of the magic that occupies that scroll and then make the mistake of measuring it through that. Such a method won't even get you near the architect of the scroll maker or replicate the magical output in the same manner. i.e. You still wouldn't be able to produce another flat universe until you figure out what replaces that zero total energy and if you do, it might not be considered energy, but it still would be utilized like an energy/engine for another infinite flat universe in order to establish the original theory but like a duplicate copy of an infinite scroll, it doesn't necessarily guarantee that both infinite scrolls are created through identical methods.

To shorten: Even if someone knows about the universe, all they can do is measure it based on their assumed parameters which is based on the surrounding environment they are able to measure in. How then can anyone in that situation even know what the "basic" parameter is not just for a different planet but for the entire universe?

[Renegade]

Here you go  - it's described in NASA's: Universe 101
Time to change paradigms...

Is it saying the third dimension exists but it is so disproportionately small, it may as well be flat?

My non-scientific mind finds this consistent with the universe having been pressed into a shape by a giant cookie cutter, handy if you are creating several.

I don't think it's saying that at all. It's talking about the topology of the universe, and that it is flat, i.e. Euclidean, and not topologically similar to an n-sphere or torus something like that.

Remember, the number of dimensions has almost nothing to do with the topology, e.g. a 1-sphere is a circle, a 2-sphere is what you would normally call a sphere, but you also have 3-spheres and n-spheres. All of those are topologically spheres, but they exists in n+1 dimensions. You get the exact same thing with other topologies like an n-torus.

[IainB]

Oolon Colluphid (the author of the trilogy of philosophical blockbusters Where God Went Wrong, Some More of God's Greatest Mistakes and Who is this God Person Anyway?) later used the Babel Fish argument as a basis for a fourth book, entitled Well, That About Wraps It Up For God.
I think he may need to write an update or addendum to the latter, to incorporate the now rather old discovery/theory that the universe apparently has zero energy and was created from zero energy, or something. That looks like a dead giveaway.