[Spliff]

Until now. Cosmologists scrutinizing patterns in the microwave radiation 'afterglow' of the big bang have taken a big chunk out of that uncertainty. They calculate that the universe cannot possibly be smaller than a hefty 78 billion light years across.

Source: http://www.nature.com/nsu/040517/040517-3.html

The universe is supposed to be around 14 billion years old, give or take a billion years. According to the Special Theory of Relativity, nothing can exceed the speed of light. It's the cosmic speed limit. So how can the universe be at least 78 billions years across if it's only 14 billion years old. At the most, it should be 14 billions light years across because it wouldn't be able to expand faster than the speed of light.

Has there been some revision to the Special Theory of Relativity? Because obviously the universe has been expanding faster than the speed of light at some point in its history. I haven't kept up on my physics since high school, but something has obviously been revised because it would appear that c is no longer the cosmic speed limit.

[starman]

Thinking about the size of the universe makes my head hurt. Please stop.

Mike

[euchomai]

It's because God created a mature universe.

[Cipher13]

Originally posted by Spliff:
Source: http://www.nature.com/nsu/040517/040517-3.html

The universe is supposed to be around 14 billion years old, give or take a billion years. According to the Special Theory of Relativity, nothing can exceed the speed of light. It's the cosmic speed limit. So how can the universe be at least 78 billions years across if it's only 14 billion years old. At the most, it should be 14 billions light years across because it wouldn't be able to expand faster than the speed of light.

Has there been some revision to the Special Theory of Relativity? Because obviously the universe has been expanding faster than the speed of light at some point in its history. I haven't kept up on my physics since high school, but something has obviously been revised because it would appear that c is no longer the cosmic speed limit.

Actually, if the universe is ~14bn years old, then the universe should be a maximum of 30bn light years across; expansion is three dimensional (at least, don't get me arguing about that...), and 'length' is a plane, so expansion in any two polar directions would be 14bn light years each direction from the center point, therefore 30bn light years.

I'd just like to throw a spanner into the works, and let the arguments ensue though: topic: gravity is faster than light.

EDIT: Typo.

[Cipher13]

Additionally, the speed of light is not constant through all mediums; therefore, conditions at different periods may have altered the theoretical "speed limit" of c, which I'm not even convinced is such.

[Spliff]

Originally posted by Cipher13:
Actually, if the universe is ~14bn years old, then the universe should be a maximum of 30bn light years across; expansion is three dimensional (at least, don't get me arguing about that...), and 'length' is a plane, so expansion in any two polar directions would be 14bn light years each direction from the center point, therefore 13bn light years.

D'oh! You're right. I forgot about that. However, that's still not enough to match the 78 billion year minimum these physicists are claiming.

[11011001]

Originally posted by Cipher13:
Additionally, the speed of light is not constant through all mediums; therefore, conditions at different periods may have altered the theoretical "speed limit" of c, which I'm not even convinced is such.

c is the speed of light in a vacuum.. light mainly travels in a vacuum through space, the difference that interstellar gas contributes should be minimal.

But, perhaps as lots of scientists have suggested, the laws of physics aren't exactly the same everywhere, so c might not be the constant that it is here in our region.

And there are lots of theories that the universe isn't spherical.. it's other shapes. Perhaps that's how we get this 78 billion lights years thing...

and here is another idea, perhaps this also includes the expansion of space itself, so we don't have to worry about the speed of light on matter.. but how fast can space expand? Wasn't it shown that the "speed" of gravity is c?

[cszar2001]

Originally posted by Spliff:
Source: http://www.nature.com/nsu/040517/040517-3.html

The universe is supposed to be around 14 billion years old, give or take a billion years. According to the Special Theory of Relativity, nothing can exceed the speed of light. It's the cosmic speed limit. So how can the universe be at least 78 billions years across if it's only 14 billion years old. At the most, it should be 14 billions light years across because it wouldn't be able to expand faster than the speed of light.

Has there been some revision to the Special Theory of Relativity? Because obviously the universe has been expanding faster than the speed of light at some point in its history. I haven't kept up on my physics since high school, but something has obviously been revised because it would appear that c is no longer the cosmic speed limit.

The conditions at the beginning of the universe were very different from what we see today. Special relativity only applies to the current state of affairs.

[f1000]

Originally posted by Spliff:
So how can the universe be at least 78 billions years across if it's only 14 billion years old. At the most, it should be 14 billions light years across because it wouldn't be able to expand faster than the speed of light.

You�re assuming that the visible universe encompasses the entire universe. This is only true if the entire universe began from a single point, which is an idea that this study apparently refutes.

If you read the study carefully, you'll see that the 78 billion light-years is a lower bound on the size of the universe. The universe may in fact be infinite.

[Gee4orce]

Just after the big bang the universe 'inflated' - space itself expanded to fill the non-space of whatever is outside the edge of the universe. The inflation was faster than the speed of light, but I don't know how large it got. It's possible that this accounts for the discrepancy.

I sometimes get the feeling that astrophysicists just make this stuff up. In reality they lead lives of leisure, relaxing by the pool, and every six months or so one of them says "hey, shouldn't we make a press release to give the impression we are working", so they dream up something that nobody else can get their heads around.

[f1000]

http://www.astro.ucla.edu/~wright/infpoint.gif
[Inline images MUST be no more than 480 pixels wide. Please read and obey the image posting rules. -- tooki

The box on the left represents the 78 billion light-year universe at the start of the Big Bang. The green circle within the box indicates the singularity from which the visible universe sprang. The black dots represent galaxies (which do not expand). As you can see, the visible universe does not equal the entire universe.

http://www.astro.ucla.edu/~wright/cosmo_01.htm

[Sherwin]

Originally posted by f1000:
If you read the study carefully, you'll see that the 78 billion light-years is a lower bound on the size of the universe. The universe may in fact be infinite.

Hmmm... Short of it wrapping around on itself, I can't see it not being infinite. The definition of universe means everything, right? So how can anything be outside it? How can there be an "edge"?

It either wraps on itself or is infinite. No other real logical options.

[Agasthya]

Originally posted by Gee4orce:
Just after the big bang the universe 'inflated' - space itself expanded to fill the non-space of whatever is outside the edge of the universe. The inflation was faster than the speed of light, but I don't know how large it got. It's possible that this accounts for the discrepancy.

I sometimes get the feeling that astrophysicists just make this stuff up. In reality they lead lives of leisure, relaxing by the pool, and every six months or so one of them says "hey, shouldn't we make a press release to give the impression we are working", so they dream up something that nobody else can get their heads around.

The theoretical calculations show that between 10^-35 and 10^-32 seconds after the Big Bang, the universe increased in size from about 10^-25 to 10^25 meters (about 10^57 m/s). This is commonly referred to as the inflation era.

Relatively restricts matter and energy to speeds smaller than the speed of light, but it imposes no such restrictions on the universe as a whole.

(Stupid Astronomy class finally being useful for something )

[MacGorilla]

Yes, the Universe itself can expand much faster than the speed of light so the Universe can be 78 billion light years across while the visible universe is only 14 billion.

[Wiskedjak]

Originally posted by Spliff:
Has there been some revision to the Special Theory of Relativity?

Could be that the STR is wrong.

[djohnson]

Originally posted by MacGorilla:
Yes, the Universe itself can expand much faster than the speed of light so the Universe can be 78 billion light years across while the visible universe is only 14 billion.

Any proof?

There are formula's that physic's people use to show that the energy required to hit the speed of light is infinite, however, if you increase the speed past c, the energy levels go down! I say this is a case of not quote knowing exactly what they are dealing with.

[theolein]

I was going to post some trollbait about religion vs. science in here, but decided against it.

This same topic was once discussed to death in the mega long religion and science thread. In fact it was discussed beyond the point of death thereby proving that even if the afterlife for human souls is debatable, the afterlife for human threads is not.

[BlackGriffen]

The speed of light is the limit at which energy (and thus forces, mass, and information) can travel through space itself. The ability of space to expand need not be limited by the rate that energy can travel through it.

It's good that your skeptical, though, it keeps people on their toes.

BlackGriffen

[ghost_flash]

Originally posted by MacGorilla:
Yes, the Universe itself can expand much faster than the speed of light so the Universe can be 78 billion light years across while the visible universe is only 14 billion.

That statement demands a leap of faith....

[voodoo]

FTL

[theolein]

IBL

[ghost_flash]

PTL

[ghost_flash]

Could this possibly be an explanation? At least as far as the "Big Bang" is concerned.

http://www.newscientist.com/news/news.jsp?id=ns99992796
http://www.wsws.org/public_html/prio...b9-9/light.htm

[f1000]

Look guys, read this little tutorial by Professor Wright at UCLA,

http://www.astro.ucla.edu/~wright/infpoint.html

[Will McGoonigle]

Dumbass Qs and As.

Light hasn't even been around since the universe began. Even a decently intelligent five year old knows that. What, some people still believe the big bang was all fire, light, sound and Hollywood effects?

The age of the expansion of time-space is separate from the age of the first light.

[benb]

Originally posted by Will McGoonigle:
Dumbass Qs and As.

Light hasn't even been around since the universe an. Even a decently intelligent five year old knows that. What, some people still believe the big bang was all fire, light, sound and Hollywood effects?

The age of the expansion of time-space is separate from the age of the first light.

Hahahahahahahahaha.

Haha.

Thanks for the laugh.

[wdlove]

I'm really impressed by this intellectual discussion!

[hyteckit]

Sorry, but the speed of light has been slowing down ever since the big bang.

[amsalpemkcus]

and what are we amidst such expanse...it is depressing..we are all but speck of dust that went through a beam of light to even be noticed...

[Will McGoonigle]

Originally posted by hyteckit:
Sorry, but the speed of light has been slowing down ever since the big bang.

Which makes no sense because there was no light at the time.

[Will McGoonigle]

Originally posted by benb:
Hahahahahahahahaha.

Haha.

Thanks for the laugh.

Dunno if you're being funny or stupid. Light is emitted by stars and reflected by matter, both of which didn't exist for eons after the big bang. Before the formation of them and even the first elements it was all background radiation beyond the spectrum of light as we know it.

Not a photon in 'sight'.

[Chris O'Brien]

Originally posted by BlackGriffen:
The speed of light is the limit at which energy (and thus forces, mass, and information) can travel through space itself. The ability of space to expand need not be limited by the rate that energy can travel through it.

Yup - something similar to this can be seen everyday by the fact that the phase velocity of an electromagnetic wave through a waveguide is greater than the speed of light. The group velocity (the energy propegation) is less than c, however.

[djohnson]

Unless we find a negative constant, we will need some negative energy to "warp" through space. The equations have already been proven...

[RAzaRazor]

Found an recent article on CNN about this very topic. Take a look.

http://www.cnn.com/2004/TECH/space/0...ide/index.html

[Jaey]

Originally posted by hyteckit:
Sorry, but the speed of light has been slowing down ever since the big bang.

Yes, I actually read an article about that theory. It says that at the moment of the big bang, the speed of light was faster than it is now. They compared it to kinetic molecular theory which states that when heat (energy) is added to something, that something's particles become "excited" and begin to move faster. In the case of the big bang, the light was "hot" for some reason or another, but is now "cooling".

[talisker]

Here's your answer, from wikipedia:

Big Bang

The relevant paragraph is this bit:

The Big Bang was not an explosion of matter moving outward to fill an empty universe; it is space itself that is expanding. So, bizarre as it may seem, the distance between any two fixed points in our universe is increasing. Intuitively this seems impossible: if the distance between two things increases then it seems that by definition one or both must be moving. But this is not so, as becomes clear if you consider the simplistic but logically equivalent model of a universe of constant size (whether finite or infinite), in which everything is shrinking. The people who live in this universe are shrinking too, as are all their scientific instruments. When these people measure the distance between two points that are sufficiently far apart, the distance will seem to be increasing, because the yardsticks they use to measure with are shrinking along with everything else. The fundamental assumption in this idea is that spacetime on the largest scales is unaffected by locality; objects that are bound together do not expand with spacetime's expansion because local forces keep them together. The expansion of the universe on local scales is so small that the difference of any local forces is unmeasurable by current techniques.

Because it is space itself that is expanding, and not a case of objects flying apart through space, the distance (in the sense of comoving distance) between far removed galaxies can increase faster than the speed of light without violating the laws of special relativity.

(Help my brain has melted)

[Jaey]

So wait, is the matter expanding with the universe or something?

[f1000]

Originally posted by Sherwin:
Hmmm... Short of it wrapping around on itself, I can't see it not being infinite. The definition of universe means everything, right? So how can anything be outside it? How can there be an "edge"?

It either wraps on itself or is infinite. No other real logical options.

The spatial extent of the universe is different from its geometry. A negatively curved (open) universe can be either infinite or compact.

One can represent a closed universe, for example, as the �infinite� surface of a sphere. What cosmologists wonder is whether the surface area of the sphere (its spatial extent) may also be infinitely large.


From Prof. Spergel, a theoretical astrophysicist at Princeton:

Cosmologists generally consider three possible geometries for the universe: a positively curved universe, a flat universe, and a negatively curved universe. In standard parlance, closed, critical and open universes. This later nomenclature is misleading: negatively curved universes can be either infinite in spatial extent or compact. Both models have the same dynamics and expand forever: dynamics is determined by geometry. The three-sphere is a space of constant positive curvature, and the pseudosphere is a hyperbolic space with constant negative curvature.

[f1000]

Originally posted by Will McGoonigle:
Light hasn't even been around since the universe began.

Light is emitted by stars and reflected by matter, both of which didn't exist for eons after the big bang. Before the formation of them and even the first elements it was all background radiation beyond the spectrum of light as we know it.

Not a photon in 'sight'.

Both matter and photons existed 10^-33 seconds after the Big Bang. Hydrogen began condensing about 1 second after the Big Bang.

What you meant to say was that the universe was opaque for about 300,000 years.

http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang

[ambush]

Originally posted by wdlove:
I'm really impressed by this intellectual discussion!

But between you and me, this is all false.

God did it. There is no big bang.

[Will McGoonigle]

Originally posted by f1000:
Both matter and photons existed 10^-33 seconds after the Big Bang. Hydrogen began condensing about 1 second after the Big Bang.

What you meant to say was that the universe was opaque for about 300,000 years.

http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang

That's the one! And it still took a long time after that for the first light to shine considering how long it takes for a star to form.

[tie]

Originally posted by talisker:
The Big Bang was not an explosion of matter moving outward to fill an empty universe; it is space itself that is expanding. So, bizarre as it may seem, the distance between any two fixed points in our universe is increasing.

There are two ways in which the universe can be said to be expanding:

1. The geometry is expanding, space itself is stretching out. (Think of the universe as the surface of a balloon as it is blown up. Fixed points on the surface get farther away from each other without moving on the surface. To make this analogy more accurate, remove the ambient space, so the balloon's surface is everything.)

2. The extent of the visible universe -- light-cone into the past -- is increasing, one light-year further every year.

These are completely different kinds of "expansion," but they are often confused in popular literature.

An easy conceptual view of the universe is as an infinite, nearly homogeneous surface which is slowly stretching (type 1 expansion). We are a little dot on this surface, and the visible universe is an expanding disk centered on that dot (type 2 expansion).

(Of course we only know about the part of the universe within the visible disk and for all we know it could be completely different, or not even "exist," outside this disk -- but this is a convenient story.)

[wataru]

Originally posted by Will McGoonigle:
That's the one! And it still took a long time after that for the first light to shine considering how long it takes for a star to form.

You're either trolling or just seriously misinformed. Stars are not the only sources of photons, not by a long shot.

[hyteckit]

Originally posted by Will McGoonigle:
That's the one! And it still took a long time after that for the first light to shine considering how long it takes for a star to form.

Can't light come the energy explosive of the Big Bang creating photons and extremely heated particles? Who said light have to come from stars? There is light before stars are formed.

[Ozmodiar]

Any time an electron goes from an excited state to non-excited state it releases a photon. Everything releases photons. You are emitting light right now. Stars are just big things releasing lots of photons.

[hyteckit]

Yes, it takes energy to release those damn photons. The stars are like a nuclear reactor that release lots of photons.

[benb]

Originally posted by Ozmodiar:
Any time an electron goes from an excited state to non-excited state it releases a photon. Everything releases photons. You are emitting light right now. Stars are just big things releasing lots of photons.

Thank you. Electrons that undergo acceleration emit photons too.

[f1000]

Originally posted by benb:
Thank you. Electrons that undergo acceleration emit photons too.

Protons that undergo acceleration emit photons, as well.

[Ozmodiar]

Originally posted by f1000:
Protons that undergo acceleration emit photons, as well.

Protons or positrons? Or both?

[ghost_flash]

As long as there are no negetrons! I hate them things. Their soooooo..... negative.