The Paradox of the Big Bang

[Denny Crane]

Scientists tell us the universe (as we now know it) started as an infinitely small singularity that exploded, sending matter and energy expanding throughout the universe.

They determine this by seeing a red (of light) shift when looking at objects in the heavens, and that leads to the conclusion the universe is expanding; everything is moving away from everything else. Well, I don't think this is exactly true, as in a few billion years we're supposed to see a collision between andromeda and the milky way; obviously the two aren't moving apart. Run time backward and everything condenses at a singularity.

That's not the paradox, though. Scientists say they are looking further back in time when they look further away from us. This makes sense, as light originating from a source 1M light years away mathematically has to have originated 1M years ago (speed of light, light years).

The paradox is this. The universe is about 13.5B years old by scientists' estimates. The Hubble Telescope is able to see almost 13.5B light years away, hence they're seeing back in time almost all the way to the point of the big bang. The light from those far off objects originated 13.5B years ago, or so they say. YET... 13.5B years ago, weren't we very close to those objects because the big bang had just happened, not much time passed to let things get 13.5B light years away.

Explain it, if you can.

 

[TheBeef]

The speed at which light travels is a theory....like many scientific theories, it is presented as fact....it may be correct, but its not provable....you are correct though that when judging distances and time, and one has to take into consideration the theory that we were closer at one point....another factor is that looking through the hubble, you arent seeing light that reached here, you are seeing light that reached the outer limits of hubbles ability to see....

 

[Denny Crane]

Well, we know light doesn't always go the speed of light, we just know it never goes any faster. It goes slower near black holes, or zero inside them.

There's some theoretical subatomic particles that might go faster than the speed of light, but I don't see how those would relate to light.

Something to consider is that space is seen as a container of sorts. Like a balloon. It is expanding like that balloon being blown up. The container that is space is physically larger than the speed of light allows. They say the universe is something like 60B light years across, yet the diameter of a big bang type explosion can only be 13.5 + 13.5 = 27B light years across.

 

[TheBeef]

theoretically light never goes faster....once again, it cant be proven....computer models could prove it if the data was certain, but the data is subject to that which man has gathered....many accepted scientific theories have been debunked years after they were thought to be fact....the issue is this: We cant know what we dont know, all we can do is keep gathering data and trying to disprove theories....

 

[Lavalamp]

<div class='quotetop'>QUOTE </div><div class='quotemain'>* 13.7 billion light-years. The age of the universe is about 13.7 billion years. While it is commonly understood that nothing travels faster than light, it is a common misconception that the radius of the observable universe must therefore amount to only 13.7 billion light-years. This reasoning only makes sense if the universe is the flat spacetime of special relativity; in the real universe, spacetime is highly curved on cosmological scales, which means that 3-space (which is roughly flat) is expanding, as evidenced by Hubble's law. Distances obtained as the speed of light multiplied by a cosmological time interval have no direct physical significance. [5]</div>
From wiki.

There!

 

[Denny Crane]

That explains why the universe is bigger than 2x 13.7B light years across, not how light can start right next to us 13.5B years ago and not reach our eyes until now.

Plus, I think I explained what you posted in my previous post, almost exactly the same.

 

[CelticKing]

<div class='quotetop'>QUOTE (Denny Crane @ Aug 1 2008, 08:38 PM) <{POST_SNAPBACK}></div><div class='quotemain'>That explains why the universe is bigger than 2x 13.7B light years across, not how light can start right next to us 13.5B years ago and not reach our eyes until now.

Plus, I think I explained what you posted in my previous post, almost exactly the same.</div>

Thats a great point Denny, never thought of it that way. So you're saying how is it possible that when everything started we were all together, then the explosion, and all of the sudden we're light years apart, and just now the light is reach us.

I actually don't believe that much in the big bang theory, I don't believe that everything came out from nothing, IMO things need to exist to be born, you need support to exist basically.

 

[Thoth]

<div class='quotetop'>QUOTE (CelticKing)</div><div class='quotemain'>I actually don't believe that much in the big bang theory, I don't believe that everything came out from nothing, IMO things need to exist to be born, you need support to exist basically.</div>

CK is on to something. It reminded me of the 1st law of thermodynamics

<div class='quotetop'>QUOTE </div><div class='quotemain'>More simply, the First Law states that energy cannot be created or destroyed</div>

 

[lukewarmplay]

Okay, I'll take a closer look later, but one thing to keep in mind- because you'll get there, if you're not actually asking it above - is that the universe can and theoretically has expanded at faster than light speeds- kind of. I don't know the exact numbers, but over the course of a tiny (10^-34?) fraction of a second, it expanded (10^64?) times. That explains, at the least, why the cosmic microwave background radiation looks pretty much the same at opposite ends of the universe even though it's 28 billion light years away and otherwise would never have been close enough to share information.

I'm not exactly sure what you're asking- are you assuming we couldn't see the supernovae back then and only can now?

 

[Denny Crane]

No.

I'm saying that light that left something right next to us shortly after the big bang had to have passed us by long ago. Therefore, we can't be looking back in time to near the big bang.

Everything started as a singularity 13.7B years ago. Assuming one particle goes off at 0 degrees at the speed of light and another goes off at 180 degrees at the speed of light, the two particles should be 13.7B x 2 light years apart. Hence the universe should be 27.4B across, max. The expansion of space, as you say, works like those two particles were on the surface of a balloon; inflate the balloon and the distances are even greater. For argument's sake, let's say with the expansion included, the universe is 54B light years across (2x what it would be without).

If light doesn't move faster with the expansion of the universe, how can it catch up to us at all? You pointed out the universe is expanding faster than the speed of light! The answer seems to be that it does move faster with the expansion, and the earth doesn't move at the speed of light, so it trivially catches up to us.

Read this carefully:

At the point of the big bang, we were 0 (pick a measurement) distance away from the origin of the light we're seeing that started towards us at that time. Move ahead .2B years and we were something bigger than 0 distance but far less than 13.5B light years away from the origin of the light we're seeing now. That distance can be calculated, no doubt, but let's make it easy and pick a distance of say 1B light years. Times 2 for expansion of the universe would mean the light that left the origin 13.5B years ago would have passed us by 11.5B years ago. How can we possibly be seeing it now?

Regarding a couple of related points...

The universe is not only expanding, the rate of expansion is accelerating. See http://berkeley.edu/news/media/releases/20...6/22_shaw.shtml

The microwaves we see as aftereffect of the big bang are actually light waves; they've been stretched by the expansion of the universe to the point we can't see them anymore and can only detect them as microwaves

The wikipedia article talks about the radius of the universe being a misconception at 13.7B light years. I'm using the diameter in my arguments, which is 2x the radius (of a sphere or disk).

 

[lukewarmplay]

I think I see what you're getting at. I'll start by saying I didn't mean to imply the universe is currently expanding at faster-than-light speeds, only that it possibly did once (for a tiny amount of time) and nothing in the physics seems to impede it from doing so. So let's leave that type of expansion aside for a moment, and look at it in a more simple manner- as two objects moving away from each other. So early on, these objects are 1 billion light years apart (or 10, or whatever) and are moving apart at speeds of .1 times the speed light (or .3 or .6 , but .99 starts to get a little harder, maybe). The light leaving object 1 (a star, to keep it simple) at that instant travels 1 billion years and obviously doesn't hit us, because we've moved away from where we were - if you view the star as stationary, we've moved 100 million light years away. Of course, the light travels 100 million light years and we're 10 million light years ahead of it still, etc. Eventually, it does hit us. At that point, you measure the red-shift of the light to determine the distance, which I can attempt to explain if you want, and you learn that the light is 1.11111 billion years old, so you're seeing the star as it was 1.1111 billion years ago (I'm sorry if my math is off, which is more than likely). So that's how you're seeing "back in time", because you know the current state of the star is different. I think the whole "looking back in time" characterization might be a little misleading, even though it's technically true.
The other important bit is to realize that there was light from that star hitting us the whole time, before the light whose redshift we measured, and afterwards also. We saw the birth of the star (albeit after it happened, as the light took time to reach us) and we'll see the death of the star (if we're around, which will involve some good luck, maybe). Hope this helps clear anything up.

I did a presentation on the cosmic microwave background a few months ago, it's pretty fantastic and (for me, at least) a little confusing.

 

[Denny Crane]

I don't see how the universe expansion could have sped up instantly (at big bang +0), then slowed down, then sped up to what we measure today.

I understand red shift. It's why the microwaves aren't light anymore. I also understand waveforms ...

The key characteristics of the paradox is that looking back in time 13.5B years is looking back nearly to the big bang itself, to the beginning of time itself. The paradox doesn't jump out at you if you look at a star or galaxy 5 light years away. At 13.5B years ago, light didn't have to travel very far to reach us. That's the light we're supposedly seeing today; it supposedly took 13.5B years to reach our eye. Yet 13.5B years ago, it didn't have to travel very far to reach us. (I know I repeated myself).

There's no way the earth is moving at the speed of light, so light has to catch up to us. We're not moving even close to it.

 

[lukewarmplay]

<div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 01:14 AM) <{POST_SNAPBACK}></div><div class='quotemain'>a)I don't see how the universe expansion could have sped up instantly (at big bang +0), then slowed down, then sped up to what we measure today.

I understand red shift. It's why the microwaves aren't light anymore. I also understand waveforms ...

b)The key characteristics of the paradox is that looking back in time 13.5B years is looking back nearly to the big bang itself, to the beginning of time itself. The paradox doesn't jump out at you if you look at a star or galaxy 5 light years away. At 13.5B years ago, light didn't have to travel very far to reach us. That's the light we're supposedly seeing today; it supposedly took 13.5B years to reach our eye. Yet 13.5B years ago, it didn't have to travel very far to reach us. (I know I repeated myself).

c)There's no way the earth is moving at the speed of light, so light has to catch up to us. We're not moving even close to it.</div>

a) Join the club. No one understands the mechanism behind inflation. And right now, it's mostly a theoretical construct. The existence of gravity waves (or something...) in the next set of data from the CMB satellites would offer evidence in favor of it having happened.

b) see c)

c) relative to what? there are objects that we're moving at .99 the speed of light away from, and, as you said, objects we're locally moving towards, which could be considered negative velocity. or you could use my personal favorite, and think of us as standing still, and everything else is moving away/towards/revolving around us (actually, around me- i remain perfectly still at all times).

b) so given that there are objects we're moving that fast away from, does it make more sense that there could be objects whose light takes that long to reach us? i understand your objection, but let's say you're right, there's still an oldest time that we would be able to see, and that time would be determined by relative speed. stars light up about 400 million (thousand?- okay, fine, i'm going to dig around for that presentation - okay, 100's of millions of years) but at that point, what will become us is already moving at different speeds away from everything else. you're not going to be able to see into the distant past for most things, but a few things, yes.

 

[lukewarmplay]

and, hey, i do apologize if i'm being pedantic. these are difficult and interesting conceptual issues you're bringing up - even though this is material i've supposedly learned several times (which probably says something about me...)

 

[Lavalamp]

<div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 01:14 AM) <{POST_SNAPBACK}></div><div class='quotemain'>I don't see how the universe expansion could have sped up instantly (at big bang +0), then slowed down, then sped up to what we measure today.</div>
I have no idea to be honest. I read something like there was massive energy, which caused the bang and it became photons, photons became quarks, quarks formed electrons, neutrons, protons, etc, and as more energy became matter the expansion slowed, and gravity had a stronger affect with more matter. Now on the accelerating expansion I have no idea what's up with that.

<div class='quotetop'>QUOTE </div><div class='quotemain'>The key characteristics of the paradox is that looking back in time 13.5B years is looking back nearly to the big bang itself, to the beginning of time itself. The paradox doesn't jump out at you if you look at a star or galaxy 5 light years away. At 13.5B years ago, light didn't have to travel very far to reach us. That's the light we're supposedly seeing today; it supposedly took 13.5B years to reach our eye. Yet 13.5B years ago, it didn't have to travel very far to reach us. (I know I repeated myself).

There's no way the earth is moving at the speed of light, so light has to catch up to us. We're not moving even close to it.</div>
I don't know. If most of the expansion was done in the first 0.2 billion years then I would understand us being able to see light from 13.5 billion years ago, otherwise not as much.

 

[Denny Crane]

<div class='quotetop'>QUOTE (Lavalamp @ Aug 1 2008, 11:20 PM) <{POST_SNAPBACK}></div><div class='quotemain'><div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 01:14 AM) <{POST_SNAPBACK}></div><div class='quotemain'>I don't see how the universe expansion could have sped up instantly (at big bang +0), then slowed down, then sped up to what we measure today.</div>
I have no idea to be honest. I read something like there was massive energy, which caused the bang and it became photons, photons became quarks, quarks formed electrons, neutrons, protons, etc, and as more energy became matter the expansion slowed, and gravity had a stronger affect with more matter. Now on the accelerating expansion I have no idea what's up with that.

<div class='quotetop'>QUOTE </div><div class='quotemain'>The key characteristics of the paradox is that looking back in time 13.5B years is looking back nearly to the big bang itself, to the beginning of time itself. The paradox doesn't jump out at you if you look at a star or galaxy 5 light years away. At 13.5B years ago, light didn't have to travel very far to reach us. That's the light we're supposedly seeing today; it supposedly took 13.5B years to reach our eye. Yet 13.5B years ago, it didn't have to travel very far to reach us. (I know I repeated myself).

There's no way the earth is moving at the speed of light, so light has to catch up to us. We're not moving even close to it.</div>
I don't know. If most of the expansion was done in the first 0.2 billion years then I would understand us being able to see light from 13.5 billion years ago, otherwise not as much.
</div>

It sure seems like they're making things up to fit what they currently see, if they're suggesting things sped up, slowed down, then sped up again. What violated Newton's law of motion to slow things down? What kind of 2nd big bang type event made them speed up again? I've never heard any astrophysicist suggest such a thing. I've heard a steady state theory, an expanding universe theory, and a big crunch theory...

I pointed you to a page about Saul Perlmutter, who won the nobel prize for his work that determined that not only is the universe expanding, it's expanding at an ever increasing rate. If the space we occupy ever moved faster than the speed of light so light could not catch up to us for nearly as long as time itself has existed, it should be falling further and further behind in its quest to catch up to us. This all makes sense if you consider dark matter and Einstein's view that gravity is a repulsive force and not an attractive one. (We're stuck to the earth because the universe is pushing us to it).

Then we can consider the speed of the earth and sun and light. The Earth orbits the sun at ~15 miles/second... The sun orbits the galactic center at ~15 miles/second. The galaxy is moving through space at 600 Km/sec. The measured speed of light is 186,000 miles/second or 300,000 Km/sec. There's no way the Earth is outrunning light, or could have outrun it from 1B light years to 13B light years in distance

The negative velocity argument doesn't hold up, to the best of my knowledge. If you and I are on different trains approaching each other at 100 MPH, from our perspectives, it sure looks like we're approaching each other at 200 MPH, right? But if we're on beams of light approaching each other, Einstein tells us we don't see ourselves approaching each other at 2x the speed of light. If you can't add the speed of light together like this, you can't subtract from it either.

The nature of the light is an interesting question, as well. If there was a big bang, you'd expect there to be a huge flash of light that would travel 13.7B light years to our eyes today; the night sky should be completely brightly lit up. As I said, that light is shifted to the point it's microwaves, and the night sky actually is brightly lit up. Yet light .2B years younger appears as light.

We also know that light can go slower than the speed of light. It goes slower through water, for example. This is the only answer I can see that makes sense. If light at 1 light years' distance back then took 13.5B years to reach us, then the light had to move at 1/13.5 the speed of light at that time. (That's your fixed state argument). Add in the expansion of the universe as a factor to both the 1 light years' distance and the speed of light, and it still hits our eye in 13.5B years.

 

[lukewarmplay]

<div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 10:13 AM) <{POST_SNAPBACK}></div><div class='quotemain'><div class='quotetop'>QUOTE (Lavalamp @ Aug 1 2008, 11:20 PM) <{POST_SNAPBACK}></div><div class='quotemain'><div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 01:14 AM) <{POST_SNAPBACK}></div><div class='quotemain'>I don't see how the universe expansion could have sped up instantly (at big bang +0), then slowed down, then sped up to what we measure today.</div>
I have no idea to be honest. I read something like there was massive energy, which caused the bang and it became photons, photons became quarks, quarks formed electrons, neutrons, protons, etc, and as more energy became matter the expansion slowed, and gravity had a stronger affect with more matter. Now on the accelerating expansion I have no idea what's up with that.

<div class='quotetop'>QUOTE </div><div class='quotemain'>The key characteristics of the paradox is that looking back in time 13.5B years is looking back nearly to the big bang itself, to the beginning of time itself. The paradox doesn't jump out at you if you look at a star or galaxy 5 light years away. At 13.5B years ago, light didn't have to travel very far to reach us. That's the light we're supposedly seeing today; it supposedly took 13.5B years to reach our eye. Yet 13.5B years ago, it didn't have to travel very far to reach us. (I know I repeated myself).

There's no way the earth is moving at the speed of light, so light has to catch up to us. We're not moving even close to it.</div>
I don't know. If most of the expansion was done in the first 0.2 billion years then I would understand us being able to see light from 13.5 billion years ago, otherwise not as much.
</div>

It sure seems like they're making things up to fit what they currently see, if they're suggesting things sped up, slowed down, then sped up again. What violated Newton's law of motion to slow things down? What kind of 2nd big bang type event made them speed up again? I've never heard any astrophysicist suggest such a thing. I've heard a steady state theory, an expanding universe theory, and a big crunch theory...</div>

The idea behind inflation (and also for the expansion of the universe) isn't that things are actually moving, but that space in between things is getting created. The mechanism behind this is totally unknown and is referred to as dark energy, but doesn't violate Newton, and has no theoretical connection to the Big Bang, which as far as I know is unexplained. To me the distinction between "amount of space increasing" and "things moving apart" has always been a fine one, and I think the need for that kind of nuance means something deeper is/was happening.
As for making things up to fit the state of the universe, absolutely that's done, but the theory makes predictions that are then borne out by observation. Like I said, a good test for the theory is coming up in the next set of microwave background data.

<div class='quotetop'>QUOTE </div><div class='quotemain'>I pointed you to a page about Saul Perlmutter, who won the nobel prize for his work that determined that not only is the universe expanding, it's expanding at an ever increasing rate. If the space we occupy ever moved faster than the speed of light so light could not catch up to us for nearly as long as time itself has existed, it should be falling further and further behind in its quest to catch up to us. This all makes sense if you consider dark matter and Einstein's view that gravity is a repulsive force and not an attractive one. (We're stuck to the earth because the universe is pushing us to it).</div>

Again, I get the feeling you're thinking about individual parcels of light, which is fine, but remember that light is emitted continuously by an emitter. So that if we "accelerated" to light speed, what we would actually see is the last bit of light reaching us ever more redshifted. This is something else I've been curious about, I'll take a look at that page over the weekend. I assume than if we accelerated to faster than light speed, we could catch up to old tv shows and watch them in reverse, eliminating the need for Tivo.

<div class='quotetop'>QUOTE </div><div class='quotemain'>Then we can consider the speed of the earth and sun and light. The Earth orbits the sun at ~15 miles/second... The sun orbits the galactic center at ~15 miles/second. The galaxy is moving through space at 600 Km/sec. The measured speed of light is 186,000 miles/second or 300,000 Km/sec. There's no way the Earth is outrunning light, or could have outrun it from 1B light years to 13B light years in distance</div>

Again, all these velocities are relative. The Earth doesn't move unless you compare it to something else. That was the big deal about Einstein proving there was no aether, and that the speed of light is constant. So the earth does move at .99 times the speed of light away from something it's moving .99 times the speed of light from.

<div class='quotetop'>QUOTE </div><div class='quotemain'>The negative velocity argument doesn't hold up, to the best of my knowledge. If you and I are on different trains approaching each other at 100 MPH, from our perspectives, it sure looks like we're approaching each other at 200 MPH, right? But if we're on beams of light approaching each other, Einstein tells us we don't see ourselves approaching each other at 2x the speed of light. If you can't add the speed of light together like this, you can't subtract from it either.</div>

The negative I threw in to the velocity was just in terms of direction. It wasn't important, but I was just saying if you measure positive velocity as moving away from something, negative velocity would be moving towards something. Which is a stupid way to measure velocity.

<div class='quotetop'>QUOTE </div><div class='quotemain'>The nature of the light is an interesting question, as well. If there was a big bang, you'd expect there to be a huge flash of light that would travel 13.7B light years to our eyes today; the night sky should be completely brightly lit up. As I said, that light is shifted to the point it's microwaves, and the night sky actually is brightly lit up. Yet light .2B years younger appears as light.

We also know that light can go slower than the speed of light. It goes slower through water, for example. This is the only answer I can see that makes sense. If light at 1 light years' distance back then took 13.5B years to reach us, then the light had to move at 1/13.5 the speed of light at that time. (That's your fixed state argument). Add in the expansion of the universe as a factor to both the 1 light years' distance and the speed of light, and it still hits our eye in 13.5B years.</div>


The big bang wasn't necessarily a flash of light. The cosmic microwave is actually light from the moment where the universe became permeable to light, well after the big bang (like, at least a fraction of a second after).

I hope you see now why that last bit is wrong (in addition to the fact that the vacuum has nothing in it to slow down light), but I hope you also realize we're not having an argument. You asked a question in an area in which I have a little knowledge, and so I'm just trying to answer it to the best of my ability (which, granted, isn't that far from meager).


The last bit there also raises an interesting point for me, which is that if light is both considered a particle and a wave, and it passes through a medium into a vacuum so that it once again continues on at the speed of light, how come it's partly-particle nature doesn't mean it consumes all the energy in the universe in accelerating to the speed of light?

 

[Denny Crane]

I don't think we're arguing either. We're discussing our understanding

The big bang did occur with a giant flash of light.

http://flux.aps.org/meetings/YR03/APR03/baps/abs/S3890.html

<div class='quotetop'>QUOTE </div><div class='quotemain'>Cosmic Microwave Background
Ari Brynjolfsson (Appl. Rad. Ind.)

Large plasma redshifts of photons in hot, sparse plasma are given by \ln \left( 1+z \right)=3.326\cdot 10^-25\cdot \int_0^R N_e\cdot dx., provided the wavelength \lambda \le \lambda_0.5 =3.185\cdot 10^-6\cdot \left( 1+1.296\cdot 10^5\cdot B^2/N_e \right)\cdot \sqrt N_e/T cm, where N_e is the electron density in cm^-3, T the temperature in K, R the distance in cm to the emitter, and B the magnetic field in Gauss. The cut-off at \lambda _0.5 means that the redshift is 50% of its full value. The theory is based on an overlooked interaction of photons with hot sparse electron plasma. It has been overlooked, because the necessary conditions (high temperature and low densities over extended dimensions) cannot be created in the laboratory. The plasma redshifts help explain: the heating of the transition to the corona, the coronal heating, solar redshifts (which invalidate the equivalence principle), galactic redshifts, the heating of galactic corona, the redshifts of white dwarfs and quasars, the cosmological redshifts, and the recently discovered dimming of distant super nova. This presentation will show how plasma redshift also helps explain the cosmic microwave background.</div>

My understanding is that in the big flash of light generated by the big bang, the light was red shifted so severely it became microwaves.

Where I think your explanation doesn't satisfy my curiosity is this: you talk about the Earth (or the space it occupies to be precise) moves or moved at .99 the speed of light, yet the speed is closer to 1/10,000th the speed of light. That the universe had to mysteriously expand rapidly, then slow down, and now it's growing at an accelerating pace flies in the face of logic.

The constant emission of light from the source doesn't satisfy the question, either, since light being emitted today actually would take 13.5B years to reach our eye. Give or take how far we move away from the source at 1/10,000th the speed of light in that time.

How is it possible for something going 10,000 times faster than us relative to everything or (any point) in the universe not pass us by a long time ago if we started at roughly the same point in space (certainly far far far less than 13.5B light years apart)? Hubble sees visible light; the light from .2B years after the big bang isn't red shifted to the point of being microwaves or otherwise not visible...

Regarding the particular nature of light, I am satisfied with your own explanation that this is observed in many ways, and all experiments show that it is both a particle and a wave. Moving through liquid and slowing down is an example of one experiment and observation that supports it.

A side point about the WikiPedia page is they say you can't use traditional distance = speed x time formula, and then it proceeds to use that formula all over the place

 

[Lavalamp]

<div class='quotetop'>QUOTE (lukewarmplay @ Aug 6 2008, 04:46 AM) <{POST_SNAPBACK}></div><div class='quotemain'><div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 10:13 AM) <{POST_SNAPBACK}></div><div class='quotemain'><div class='quotetop'>QUOTE (Lavalamp @ Aug 1 2008, 11:20 PM) <{POST_SNAPBACK}></div><div class='quotemain'><div class='quotetop'>QUOTE (Denny Crane @ Aug 2 2008, 01:14 AM) <{POST_SNAPBACK}></div><div class='quotemain'>I don't see how the universe expansion could have sped up instantly (at big bang +0), then slowed down, then sped up to what we measure today.</div>
I have no idea to be honest. I read something like there was massive energy, which caused the bang and it became photons, photons became quarks, quarks formed electrons, neutrons, protons, etc, and as more energy became matter the expansion slowed, and gravity had a stronger affect with more matter. Now on the accelerating expansion I have no idea what's up with that.

<div class='quotetop'>QUOTE </div><div class='quotemain'>The key characteristics of the paradox is that looking back in time 13.5B years is looking back nearly to the big bang itself, to the beginning of time itself. The paradox doesn't jump out at you if you look at a star or galaxy 5 light years away. At 13.5B years ago, light didn't have to travel very far to reach us. That's the light we're supposedly seeing today; it supposedly took 13.5B years to reach our eye. Yet 13.5B years ago, it didn't have to travel very far to reach us. (I know I repeated myself).

There's no way the earth is moving at the speed of light, so light has to catch up to us. We're not moving even close to it.</div>
I don't know. If most of the expansion was done in the first 0.2 billion years then I would understand us being able to see light from 13.5 billion years ago, otherwise not as much.
</div>

It sure seems like they're making things up to fit what they currently see, if they're suggesting things sped up, slowed down, then sped up again. What violated Newton's law of motion to slow things down? What kind of 2nd big bang type event made them speed up again? I've never heard any astrophysicist suggest such a thing. I've heard a steady state theory, an expanding universe theory, and a big crunch theory...</div>

The idea behind inflation (and also for the expansion of the universe) isn't that things are actually moving, but that space in between things is getting created. The mechanism behind this is totally unknown and is referred to as dark energy, but doesn't violate Newton, and has no theoretical connection to the Big Bang, which as far as I know is unexplained. To me the distinction between "amount of space increasing" and "things moving apart" has always been a fine one, and I think the need for that kind of nuance means something deeper is/was happening.
As for making things up to fit the state of the universe, absolutely that's done, but the theory makes predictions that are then borne out by observation. Like I said, a good test for the theory is coming up in the next set of microwave background data. </div>
Well that is what I've read before too.

So basically:

Initial Big Bang energy = velocity to expand.
Gravity = decelerating force and is slightly more powerful due to the relative closeness of the matter within the galaxy, which slows it down.
Dark Energy (or whatever one calls it) = accelerating force which spreads the galaxy apart but seems to be more powerful as the galaxy is larger in terms of volume it occupies. Whereas gravity is the inverse.

But yea thinking about it, it does seem weird anything could slow the Big Bang down, especially with the tremendous energy, and I think whatever it was would have travelled at speeds greater than the speed of light at the very beginning or else Strong Nuclear Force wouldn't have been able to be overcome.

 

[Denny Crane]

Another weird thing to think about is this.

They say the Universe is about 60B light years in diameter (quibble with the number if you like). That would be a 30B light year radius from the big bang. What's at 61B light years from the center?

 

[Kid Chocolate]

I just looked real quick and thought this said "The Paradox of the Bang Bus"

 

[lukewarmplay]

<div class='quotetop'>QUOTE (Denny Crane @ Aug 6 2008, 09:33 AM) <{POST_SNAPBACK}></div><div class='quotemain'>I don't think we're arguing either. We're discussing our understanding

The big bang did occur with a giant flash of light.

http://flux.aps.org/meetings/YR03/APR03/baps/abs/S3890.html

<div class='quotetop'>QUOTE </div><div class='quotemain'>Cosmic Microwave Background
Ari Brynjolfsson (Appl. Rad. Ind.)

Large plasma redshifts of photons in hot, sparse plasma are given by \ln \left( 1+z \right)=3.326\cdot 10^-25\cdot \int_0^R N_e\cdot dx., provided the wavelength \lambda \le \lambda_0.5 =3.185\cdot 10^-6\cdot \left( 1+1.296\cdot 10^5\cdot B^2/N_e \right)\cdot \sqrt N_e/T cm, where N_e is the electron density in cm^-3, T the temperature in K, R the distance in cm to the emitter, and B the magnetic field in Gauss. The cut-off at \lambda _0.5 means that the redshift is 50% of its full value. The theory is based on an overlooked interaction of photons with hot sparse electron plasma. It has been overlooked, because the necessary conditions (high temperature and low densities over extended dimensions) cannot be created in the laboratory. The plasma redshifts help explain: the heating of the transition to the corona, the coronal heating, solar redshifts (which invalidate the equivalence principle), galactic redshifts, the heating of galactic corona, the redshifts of white dwarfs and quasars, the cosmological redshifts, and the recently discovered dimming of distant super nova. This presentation will show how plasma redshift also helps explain the cosmic microwave background.</div>

My understanding is that in the big flash of light generated by the big bang, the light was red shifted so severely it became microwaves.</div>

I'll buy that there was light created in the big bang, which makes sense. The CMB, however, is a map of how the universe looked at the epoch of last scattering- which is when light and matter stopped being in equilibrium. Before this, any light floating around the universe was instantly absorbed and reemitted by hydrogen. As the universe cooled and spread, all of a sudden the mass of particles becomes transparent to light, the the universe is "filled" with light. At that time, I'm pretty sure the light was in the visible spectrum (at least that's what my professor said)- but space expanding is what redshifts it.

<div class='quotetop'>QUOTE </div><div class='quotemain'>Where I think your explanation doesn't satisfy my curiosity is this: you talk about the Earth (or the space it occupies to be precise) moves or moved at .99 the speed of light, yet the speed is closer to 1/10,000th the speed of light. That the universe had to mysteriously expand rapidly, then slow down, and now it's growing at an accelerating pace flies in the face of logic.</div>

I'll try to explain this in a bottom-up way, because you seem stuck at thinking the Earth moves at a fixed speed. Think of an empty universe, except for the Earth. Our speed here is impossible to measure. Try it and it will quickly become obvious. Then add a second object, pluto. All of a sudden we can be moving away from Pluto, towards Pluto, at a measurable speed. Or they could be still relative to each other- let's say this is the case, that they're in the same frame of reference, but then we add a third object, a pebble, and it's zooming off in a different direction. Then you notice that although Earth and Pluto seemed to be completely still before, in fact they are moving away from the pebble. Let's add a sun. The earth moves kind of slowly towards that sun. So it could be moving with 0 velocity relative to pluto, or with great velocity when measured against the pebble, or slowly when measured against the sun. There is no one speed for the Earth, or for any object in a universe with more than 2 frames of reference.

That the universe was created, then expanded rapidly, then slowed, then continued to expand at an ever accelerating pace does fly in the face of logic. Dark energy is thought to be a positive feedback mechanism, wherein each parcel of space engenders the creation of more space within itself. So when you have things kind of close by, this isn't that noticeable, but when you have a lot of space between things, all of a sudden there's a lot of space being created which creates even more space and then things are just whizzing apart. This kind of answers one of your last question, about what beyond the universe - which is technically unanswerable - but if there is just space, which to me seems possible, there's more and more space being created all the time, if this is something that actually takes place. (Dark energy is what you were talking about when you said gravity can be a repulsive force, right?)
As for how this happened during inflation, I don't know (maybe no one does?), but there was a lot of weird stuff going on in the early universe. Density was being determined by quantum fluctuations, all the forces were unified (except gravity?), there was the plasma state going on, as well as the largest concentration of dark matter that would ever happen.

 

[Denny Crane]

I'm not stuck thinking the Earth moves at a fixed speed.

It moves at 1/10,000th the speed of light AND relative to the expansion of the fabric of space (which is larger than 13.7B light year radius). The photons in the light have to move relative to the expansion of space, too, otherwise it'd never reach our eye.

It's just mathematically impossible (illogical) that light emitted from very close by, in relative terms since the universe was much smaller 13.5B years ago, would take 13.5B years to reach our eye.

There's three explanations that I can come up with that do make sense:

1) Light moved slower when the universe was smaller. If it moved at a speed that it'd take 13.5B years to reach our eye tho the distance traveled was obviously far less than 13.5B light years, then it makes perfect sense. The speed of light would have gradually sped up to what we measure it today, as the universe expanded. No matter what the size of the universe, the light would always take 13.5B years to reach our eye.

2) Time does not move at a constant pace. A minute was not a minute 13.5B years ago. Speed is measured in distance / time. Similar to #1 above, time measured would have to change with the size of the universe.

3) What we're seeing isn't 13.5B light years away, but 27B light years away. The light took 13.5B years to reach us. The 27B number comes from roughly adjusting the 13.5B light years distance by the expansion of the universe.