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Author Topic: The universe is geometrically flat?  (Read 5190 times)

IainB

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The universe is geometrically flat?
« on: June 04, 2012, 03:35:01 AM »
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
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:
NASA - theoretical universe timeline (607x440).jpg

For the generations that grew up with TV before the age of cable, the box in our living room was a time machine, capable of taking us back to just a few hundred thousand years after the birth of the Universe. We just didn't realize it. Nor did the scientists that discovered this, at least at first. But luck seemed to play a large role in one of the biggest discoveries of our lifetime.

That may not have been the intended message of the discussion called "Dispatches from the Birth of the Universe," hosted by the World Science Festival on Friday. The panel provided a good picture of our current state of knowledge on the birth of the Universe, and a glimpse at what we'll likely find out next. But the history of the field turned out to be ripe with examples of things that were both hiding in plain sight (but required a bit of luck to spot), and others we've been lucky to see at all (well beyond the luck of being the right age to have seen the TV static).

Lawrence Krauss, who moderated the panel, introduced it by turning on an old TV set on stage. When turned to an empty channel, the TV displayed a familiar wall of static. About one percent of that noise, Krauss said, comes from the Universe itself, a remnant of an event that took place roughly 13.7 billion years ago. That's when, 375,000 years after the Big Bang, the Universe finally cooled enough that protons could hang on to electrons, forming hydrogen atoms and emitting photons in the process. These photons, stretched out and cooled by the expansion of the Universe, have been with us ever since. And, with just a regular old TV set, you can capture some of them.

But, even after the birth of television, nobody realized what it was. It was only fully recognized when two researchers at Bell Labs, Arno Penzias and Robert Woodrow Wilson, tried to get rid of it. As a video narrated by Wilson described it, they were attempting to detect faint microwave signals, and needed to get rid of all sources of background noise. They kept failing, though it wasn't for lack of trying. They checked whether it was the result of atomic testing (it didn't decay), whether it might be coming from New York City (which was visible from the site of the instrument), and even cleaned years of pigeon guano out of the hardware. They simply couldn't get their instrument to read a zero value.

Eventually, someone introduced them to Princeton's Robert Dicke, who had been predicting the existence of this microwave noise, and was gearing up to look for it. Dicke interpreted Penzias and Wilson's data for them, leading to their eventual Nobel Prize.

But the background they detected from Earth was smooth, while we know the Universe is lumpy, filled with complex structures. With time, theorists began predicting several different ways that these structures might have come into existence, several of which would leave their marks on the Cosmic Microwave Background (CMB) found by Penzias and Wilson. (Although Krauss admitted he was betting, on theoretical grounds, we wouldn't see anything).

John Mather, another panelist, made it his graduate project to find out whether these variations could be seen. Unfortunately, the balloon-based instrument he helped make failed in flight, and he struggled just to finish his degree. His next job was at NASA's Goddard Institute for Space Sciences and, while he was there, NASA put out a call for proposals for a science satellite to be sent into space. "My experiment failed, but it should have been done in outer space anyway," Mather said. "Our paper [describing our proposed satellite] said 'we're really smart, and we can figure this out.'"

NASA liked the idea, but it took them 15 years to actually build and launch the result, the Cosmic Background Explorer, since building the Hubble was sucking up lots of NASA's funding at the time. This turned out to really lucky for Mather, since the detector technology doubled its sensitivity during the delay. If it weren't for these improvements, COBE might not have seen anything. Instead, it revealed tiny fluctuations—one part in 100,000—that were the remains of quantum fluctuations that took place as the Universe entered its inflationary stage. Most of the structure in our Universe dates back to these tiny differences.

Princeton's David Spergel, had been working on a competing explanation, admitted "to be honest, I was a little depressed for a while" following the COBE results. His approach "Was a beautiful idea, mathematically elegant, got a few papers on it. Turned out not to be how Nature worked." But luck played a role again. Spergel helped organize a workshop to discuss the COBE results and, at it, someone boldly proclaimed that they indicated the Universe had a specific geometry (it was flat).

This bugged Spergel, since he didn't think there was any way to tell that from COBE's data. But the comment got him thinking—what would you need to do to demonstrate the Universe was flat? The end result was Spergel becoming a member of the team behind the WMAP probe, COBE's follow-up, which demonstrated that the Universe was flat (along with a number of other things).

Although the tiny fluctuations in the CMB are consistent with a Universe shaped by inflation, they're not a direct signature of inflation itself. That may be hiding in the polarization of the CMB's photons, which would bear the signature of the gravity waves unleashed by inflation. Amber Miller is prepping a telescope to be launched by balloon from Antarctica that should detect this polarization, if it exists. And she's already had a bit of luck.

Her team at Columbia is responsible for putting together the mirrors and support hardware; the camera is being built at the University of Minnesota, while NASA will be responsible for its flight from Antarctica. Assembly at a NASA facility in Texas was supposed to start just days earlier, over Memorial Day weekend. Except the camera didn't show up. It didn't show up on the day after the holiday, either. The team eventually tracked down the driver of the shipment, and found that the trailer had gone missing. After a few days of panic, they located it. Some items—Miller mentioned bicycles and a step-stool—were missing, but the camera had been left behind by the thieves.

If all goes well, the next chapter in CMB exploration will be lofted above the atmosphere in December.

And Mather? He's still benefitting from Hubble-related luck. When Hubble was designed, everyone thought galaxies only formed late in the Universe's history. As it turned out, the Hubble spotted many young ones, but couldn't image the wavelengths that captured the era in which they formed. Mather is now leading the team building the James Webb space telescope, designed to image the formation of the first structures in the Universe, the progeny of the CMB's fluctuations.


SeraphimLabs

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Re: The universe is geometrically flat?
« Reply #1 on: June 04, 2012, 04:23:57 PM »
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

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Re: The universe is geometrically flat?
« Reply #2 on: June 04, 2012, 06:07:09 PM »
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), ...
Quote
...which demonstrated that the Universe was flat (along with a number of other things).

This has certainly got me puzzling at any rate!

cmpm

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Re: The universe is geometrically flat?
« Reply #3 on: June 04, 2012, 06:26:58 PM »
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

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Re: The universe is geometrically flat?
« Reply #4 on: June 05, 2012, 12:47:48 AM »
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.
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IainB

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Re: The universe is geometrically flat?
« Reply #5 on: June 05, 2012, 04:03:10 AM »
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

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Re: The universe is geometrically flat?
« Reply #6 on: June 05, 2012, 04:17:05 AM »
Maybe I don't understand the meaning of "geometrically flat" but I thought it was a known fact that the universe was flat. :huh:

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

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Re: The universe is geometrically flat?
« Reply #7 on: June 05, 2012, 04:29:55 AM »
Quote
as if they know the universe......

This,

Paul Keith

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Re: The universe is geometrically flat?
« Reply #8 on: June 05, 2012, 05:01:28 AM »
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

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Re: The universe is geometrically flat?
« Reply #9 on: June 05, 2012, 05:12:35 AM »
Maybe I don't understand the meaning of "geometrically flat" but I thought it was a known fact that the universe was flat. :huh:

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.)
Tom

Renegade

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Re: The universe is geometrically flat?
« Reply #10 on: June 05, 2012, 07:03:16 AM »
I was right.

http://en.wikipedia....iverse#Flat_universe

And the punch line:

Quote
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.
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IainB

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Re: The universe is geometrically flat?
« Reply #11 on: June 05, 2012, 07:11:10 AM »
Here you go  - it's described in NASA's: Universe 101
Time to change paradigms...

daddydave

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Re: The universe is geometrically flat?
« Reply #12 on: June 05, 2012, 07:43:49 AM »
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.
If bad things happen to other people, it's karma. If bad things happen to me, it's kismat!

Paul Keith

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Re: The universe is geometrically flat?
« Reply #13 on: June 05, 2012, 07:54:21 AM »
Maybe I don't understand the meaning of "geometrically flat" but I thought it was a known fact that the universe was flat. :huh:

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?
« Last Edit: June 05, 2012, 07:59:24 AM by Paul Keith »

Renegade

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Re: The universe is geometrically flat?
« Reply #14 on: June 05, 2012, 08:03:40 AM »
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.
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IainB

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Re: The universe is geometrically flat?
« Reply #15 on: June 05, 2012, 05:08:44 PM »
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.
« Last Edit: June 05, 2012, 05:16:26 PM by IainB »