Expanding Universe and the Red Shift

[PixyMisa]

I hate to point this out, but the "Tired Light" hypothesis is actually a subset of the "Expanding Space" hypothesis.

I hate to point this out, but no it isn't.

Tired light is an explanation for cosmological red shift in a static Universe. (Clearly it's not needed in an expanding Universe.) It claims that red shift is produced by distance rather than relative motion. This is both impossible and wrong.

 

[ynot]

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Well, I'll try my best to answer some of these later.

Here is a question for you though: Why would it be so hard to imagine an edge to the universe? Why is an infinite universe any easier?

(The universe doesn't have an edge as far as we know. I'm only asking because it is important to remember that unbelievable does not mean untrue.)

Oh Dear - No my head really hurts! -

A thing is expanding but it doesn't have any edge to define its size? You seem to be able to consturct clear explainations so I await with interest.

It is easier for me to accept the concept of infinity rather than an edge that has something that is nothing beyond it (hope that makes some form of sense).

 

[Melendwyr]

I hate to point this out, but no it isn't.

Wrong.

Tired light is an explanation for cosmological red shift in a static Universe. (Clearly it's not needed in an expanding Universe.) It claims that red shift is produced by distance rather than relative motion. This is both impossible and wrong.

There is no "relative motion" in the expanding universe hypothesis. However, as light travels, extra space keeps popping up in between one crest and another. The net result is that the longer light travels, the greater its wavelength and the less energy it contains.

Whether you claim that light vibrates more slowly in itself, or that the expansion of space stretches out the vibration, the effect is the same.

 

[Art Vandelay]

Which just struck me as a really good argument against the "the Universe is a simulation" idea. If the Universe was a simulation, we'd see all these glitches and discontinuities as patches were rolled out. Like Mercury would suddenly start following Newtonian mechanics instead of Relativity, and then would jump in its orbit when they fixed it.

Don't be silly. Every time there's an upgrade, all memories of events before the upgrade are also modified.

Yeah, it's complicated by several factors, but for the vast majority of the Universe's history the expansion has been decelerating, hence the Hubble constant being pretty, well, constant at ~70km/s/Mpc (ie the further away something is the faster it's going and the further back in time it's light was emitted).

Seems to me that the dimension of the Hubble Constant is frequency. 70 km/s/Mpc works out to be about 2*10^-18 hertz, right? For light, that corresponds to a wavelength of about 6*10^26 meters. So galaxies further than that would be traveling faster than light?

How constant is the Hubble Constant across time? Across space?

I think that that the popular presentation of Hubble Expansion is a bit misleading, since it has to be more complicated than just stuff moving away from each other like in the balloon analogy. Because of relativity, each point must see a different "balloon".

KingMerv00

Here is a question for you though: Why would it be so hard to imagine an edge to the universe? Why is an infinite universe any easier?

How would it have an edge? What would the edge be made out of? What happens if you hit it?

 

[Melendwyr]

No, no galaxies ever travel faster than light. Extra space is popping up between them and us faster than their light can reach us... so we never see it.

 

[PixyMisa]

Wrong.

Wrong.

There is no "relative motion" in the expanding universe hypothesis.

Sure there is. Distant galaxies really are moving away from us. The source of that movement is the expansion of the Universe, but the movement is real.

The problem with "tired light" is that it (a) it contravenes the First Law of Thermodynamics (it is impossible) and Quantum Mechanics (it is impossible) and it makes predictions which are not borne out by evidence (it is wrong). See the link I provided you for a fuller explanation.

It's not a restatement of the Doppler Effect, it's just plain wrong.

 

[PixyMisa]

Anyway, my point was not the fine distinction between relative motion and an expanding universe.

My point was that the tired light conjecture does not produce the same predictions as expansion-induced red shift.

 

[PixyMisa]

What's more, distant objects act in other ways as though they were moving relative to us. For example, supernova explosions in distant galaxies exhibit time dilation exactly as you would expect if the red shift were due to relative motion.

Mathematically, yes, they are moving relative to us. If they are far enough away, they are moving, relative to us, faster than the speed of light. But it's only possible for them to be moving away faster than the speed of light, so no signal can ever reach us, so they are causally disconnected from us - not part of the observable Universe.

Just as a note, I've seen estimates of the size of the actual, as opposed to observable Universe as 156 billion light years across. Here, for example. But I don't fully understand how they get this number.

 

[LordoftheLeftHand]

I simply don’t have time to respond to all the replies but thanks for them all (very helpful). The “penny has dropped” (like it when that happens) regarding exactly what the red shift is so can now better understand the error of my ways. The dead horse can now be buried.

I still have some Big Bang itches to scratch though - If the universe is constantly expanding what area is it expanding in to? Is it occupying a space that was formally nothing? If so, what is nothing. It would have to be absolute nothing, not relative nothing. It is difficult for me to accept the concept that the universe has an outer edge let alone that it is expanding in to a space that was formerly absolute nothing. How can absolute nothing exists?

I'll take a stab at... People forgive me if I make any mistakes...

The red shift is an integral part of the Big Bang theory. Hubble noticed that the distance of remote objects was related to their red shift (the velocity they are receding from us). Objects that are farther away are moving away faster than objects that are closer. Furthermore there seemed to be a direct relationship between these two number. If you divide the distance of object 1 by the speed (red shift) of object 1 you get a result called Hubble's Constant. If you divide the distance of object 2 with the speed of object 2 you get the same result! (Hubble's Constant). This can be explained by two different scenario that I can think of:


1: The universe started with its matter clumped into small location. The rest of the universe was just infinite empty space. Some type of rapid expansion took place (explosion) and pushed the matter out into the empty space.

Imagine a car bomb. The car explodes and throws pieces in every direction. Some pieces fly far away and some not so far. Let’s say it throws tire #1 15 feet and tire #2 30 feet. Imagine we took a picture during the explosion. The tires would be flying through the air towards their final destinations. If you measured the distance (during the explosion)from the drivers seat to the tires you would find that tire #2 would be farther away from the car than tire #1, in fact it would likely have traveled twice the distance (because it would likely be moving twice as fast). If you divide the distance between tire #1 and the drivers seat by the speed it was flying you would get a number we will call the Tire Constant. If you did the same with tire #2 you would get the same answer. If you repeat these measurements from a different location (say across the street instead of the drivers seat) you would get a different answer for each tire (there would be no Tire Constant). So in this model the only location where the Tire Constant would hold true would be from the drivers seat. This means that for this scenario to be true the Earth would have to be in the “center” of the universe (drivers seat). In this model empty space is infinite and there is no edge of the universe.


2: The universe started with its matter clumped into small location. This small location is the entire universe. There is no empty space “outside” of it. Somehow “empty space” was “injected” into this small location.

Imagine 3 ants standing on an collapsed balloon. Ant #1 and #2 are standing right next to each other and ant #3 is standing a little farther away. Then someone starts to pump air into the balloon, inflating it. The skin of the balloon stretches and the distance between all of the ants starts to increase. Ant #1 notices that ant #2 is still closer than ant #3 but that both of them appear to be running away from him! He measures the distance to ant #2 and divides it by the speed that ant #2 is moving away. He calls this number the Ant Constant. Then he measures the distance to ant #3 and divides it by the speed that ant #3 is moving away and gets the same answer! In fact all the ants perform this calculation and they all come to the conclusion that everyone is running away from them at a ratio described by the Ant Constant! Each ant thinks he is at the center of his universe and everyone else is running away. In a way each ant would be correct, he is at the “center” of his universe. In this model the universe would have a finite area (the surface area of the balloon) that is increasing. There is no simple edge of the universe (as the balloon has no real edge).

LLH

 

[Rockin' Rick]

All of the tools used, radio astronomy, visible light telescopes, and background microwave radiation all suggest that the universe expanding. What's more is it's rate of expansion is increasing. The rate measurements were made by monitoring specific types of super novi. These short-lived cosmic events (short on a cosmic scale) have been monitored to try to predict the rate at which objects in the universe are moving apart. The red-shift, which is akin to the Doppler effect has been in practice for a long time. A huge number of objects have examined over this time.

I highly recommend a PBS Nova miniseries titled "Origins". Last I noticed it was available at Netflix.

 

[Art Vandelay]

Mathematically, yes, they are moving relative to us. If they are far enough away, they are moving, relative to us, faster than the speed of light. But it's only possible for them to be moving away faster than the speed of light, so no signal can ever reach us, so they are causally disconnected from us - not part of the observable Universe.

There's two problems that I have with that. First of all, the "out of sight, out of mind" idea doesn't satisfy me. Secondly, if a galaxy is moving faster than c in one frame of reference, then it must be moving faster than c in every frame of reference. Which means that its will be moving faster than c with respect even to galaxies right next to it.

If you repeat these measurements from a different location (say across the street instead of the drivers seat) you would get a different answer for each tire (there would be no Tire Constant).

Only if you assume that this different location is in the same frame of reference as the driver's seat.

He measures the distance to ant #2 and divides it by the speed that ant #2 is moving away. He calls this number the Ant Constant. Then he measures the distance to ant #3 and divides it by the speed that ant #3 is moving away and gets the same answer! In fact all the ants perform this calculation and they all come to the conclusion that everyone is running away from them at a ratio described by the Ant Constant!

Except that that doesn't work with relativity, because velocities are not additive. Suppose that ant one is halfway between ants two and three. All three ants agree that the distance from one to two is the same as the distance from one to three. Ant one should see that the velocities of two and three are of equal magnitude, but opposite direction. And two is going to see that the distance to ant three is twice the distance to ant one. If the velocity of ant one, according to ant two, is v, then the velocity of of ant three, according to ant two, is not 2v, but 2v/(1+v^2).

Rockin' Rick: the plural of "nova" is "novae".

 

[PixyMisa]

There's two problems that I have with that. First of all, the "out of sight, out of mind" idea doesn't satisfy me. Secondly, if a galaxy is moving faster than c in one frame of reference, then it must be moving faster than c in every frame of reference. Which means that its will be moving faster than c with respect even to galaxies right next to it.

Yeahbut - There is no frame of reference in which any two galaxies are moving faster than the speed of light relative to one another. That such a state exists is a straightforward inference from the expansion of the universe, but you can't use it to construct a frame of reference. Anything moving away from you faster than the speed of light is not in your frame of reference, pretty much by definition.

If we take this definition from Wikipedia:

A frame of reference is the perspective from which a system is observed. In physics, it provides a set of axes relative to which an observer can measure the position and motion of all points in a system, as well as the orientation of objects in it.

Then logically, since you cannot observe or measure anything moving away from you faster than the speed of light, even if you can infer the existence of such things they do not form part of your frame of reference.

Look, I'm not married to this particular way of describing cosmological red shift. If you argue that it is unclear, then I might well agree, but I don't think it is actually wrong. If you take the motion as real, all the calculations work just fine, causality is preserved.

 

[ynot]

I'll take a stab at... People forgive me if I make any mistakes...

The red shift is an integral part of the Big Bang theory. Hubble noticed that the distance of remote objects was related to their red shift (the velocity they are receding from us). Objects that are farther away are moving away faster than objects that are closer. Furthermore there seemed to be a direct relationship between these two number. If you divide the distance of object 1 by the speed (red shift) of object 1 you get a result called Hubble's Constant. If you divide the distance of object 2 with the speed of object 2 you get the same result! (Hubble's Constant). This can be explained by two different scenario that I can think of:


1: The universe started with its matter clumped into small location. The rest of the universe was just infinite empty space. Some type of rapid expansion took place (explosion) and pushed the matter out into the empty space.

Imagine a car bomb. The car explodes and throws pieces in every direction. Some pieces fly far away and some not so far. Let’s say it throws tire #1 15 feet and tire #2 30 feet. Imagine we took a picture during the explosion. The tires would be flying through the air towards their final destinations. If you measured the distance (during the explosion)from the drivers seat to the tires you would find that tire #2 would be farther away from the car than tire #1, in fact it would likely have traveled twice the distance (because it would likely be moving twice as fast). If you divide the distance between tire #1 and the drivers seat by the speed it was flying you would get a number we will call the Tire Constant. If you did the same with tire #2 you would get the same answer. If you repeat these measurements from a different location (say across the street instead of the drivers seat) you would get a different answer for each tire (there would be no Tire Constant). So in this model the only location where the Tire Constant would hold true would be from the drivers seat. This means that for this scenario to be true the Earth would have to be in the “center” of the universe (drivers seat). In this model empty space is infinite and there is no edge of the universe.


2: The universe started with its matter clumped into small location. This small location is the entire universe. There is no empty space “outside” of it. Somehow “empty space” was “injected” into this small location.

Imagine 3 ants standing on an collapsed balloon. Ant #1 and #2 are standing right next to each other and ant #3 is standing a little farther away. Then someone starts to pump air into the balloon, inflating it. The skin of the balloon stretches and the distance between all of the ants starts to increase. Ant #1 notices that ant #2 is still closer than ant #3 but that both of them appear to be running away from him! He measures the distance to ant #2 and divides it by the speed that ant #2 is moving away. He calls this number the Ant Constant. Then he measures the distance to ant #3 and divides it by the speed that ant #3 is moving away and gets the same answer! In fact all the ants perform this calculation and they all come to the conclusion that everyone is running away from them at a ratio described by the Ant Constant! Each ant thinks he is at the center of his universe and everyone else is running away. In a way each ant would be correct, he is at the “center” of his universe. In this model the universe would have a finite area (the surface area of the balloon) that is increasing. There is no simple edge of the universe (as the balloon has no real edge).

LLH

Thanks LeftHand - Do you know what the right hand is doing? (sorry, that must have been asked 100 times)

Thanks for the reply. Think I understand the mechanics/physics of a constant, uniform 3D expansion. I appreciate that it’s often hard to express ideas in words, so I hope I’m not being too pedantic here. The singularity (clump) is often described as being infinitely small and infinitely dense but surely it would defy description as being all of existence there would nothing else to draw a comparison with. Perhaps one could say that the matter component of the universe was more compact than it is now. Unless of course it is infinitely small compared to the little finger of God. Perhaps we are all trapped in the lungs of God and at present things are expanding because he is breathing in. The collapse will be when he breaths out. Hope the bugger doesn’t sneeze. Can you give an example of “empty space” (absolute nothing)? What we call space within the universe is not empty. As the theists say “well how do you explain the unexplainable”.

The balloon analogy works for me if you use it to explain the expansion but not the lack of an edge. The natural direction of motion is linea. The circumference of a balloon is circular. A line has ends (edges) a circle doesn’t. Also the balloon has an edge in that it has a surface. The universe does not have a surface. The idea (that some people have) that, if you travel through the universe in a straight line you will eventually end up where you began, is the stuff of theists as far as I’m concerned.

Just had an idea from something I said above (probably been done before and discarded as tripe). Maybe all the matter of the universe was the singularity and everything else of existence that is not matter (maybe even anti-matter) was external to the singularity. Matter is now expanding in to the infinite space that this other “non-matter stuff” occupies. Maybe as the matter is expanding, the “non-matter stuff” is contraction at the same rate to preserve a balance.

 

[PixyMisa]

The singularity (clump) is often described as being infinitely small and infinitely dense but surely it would defy description as being all of existence there would nothing else to draw a comparison with.

Right. That's why we call it a "singularity"; it's the point at which the laws of physics break down. We have no way to describe what it was like. But it's a pretty straightforward prediction: If the Universe is expanding, just track that expansion backwards, and at the point that time began, all the matter was in one place. Infinitely small and dense.

Perhaps one could say that the matter component of the universe was more compact than it is now.

No, not just the matter component; space itself was compressed to a point.

As the theists say “well how do you explain the unexplainable”.

We don't. In science, we say "At at time zero, the universe was infinitely dense and infinitely small, and we cannot say anything else about it."

The balloon analogy works for me if you use it to explain the expansion but not the lack of an edge. The natural direction of motion is linea. The circumference of a balloon is circular.

Start drawing a line along the balloon. Soon enough, you'll go right round the balloon and back to the starting point. On the surface of a balloon, straight lines are curved in the third dimension.

A line has ends (edges) a circle doesn’t.

A line only has ends if it's finite in length.

Also the balloon has an edge in that it has a surface. The universe does not have a surface.

A balloon is a two-dimensional sheet that is curved closed in the third dimension. The Universe is (we think) similarly curved closed in a higher dimension.

The idea (that some people have) that, if you travel through the universe in a straight line you will eventually end up where you began, is the stuff of theists as far as I’m concerned.

Well, that's exactly what would happen for an ant circumnavigating the balloon, and it's what would happen to you if the Universe were finite, closed, and static. But since the Universe is expanding outwards, you can't ever do this.

Just had an idea from something I said above (probably been done before and discarded as tripe). Maybe all the matter of the universe was the singularity and everything else of existence that is not matter (maybe even anti-matter)

Anti-matter is just matter. Really.

was external to the singularity. Matter is now expanding in to the infinite space that this other “non-matter stuff” occupies.

Nope. If that was true we wouldn't see the Cosmic Microwave Background, and we do.

 

[69dodge]

Secondly, if a galaxy is moving faster than c in one frame of reference, then it must be moving faster than c in every frame of reference. Which means that its will be moving faster than c with respect even to galaxies right next to it.

I think you're thinking about special relativity.

What's a "frame of reference" in general relativity? No such thing, really, except locally.

 

[LordoftheLeftHand]

Unless of course it is infinitely small compared to the little finger of God. Perhaps we are all trapped in the lungs of God and at present things are expanding because he is breathing in. The collapse will be when he breaths out. Hope the bugger doesn’t sneeze.

Unless of course it is infinitely small compared to a wing feather of the Giant Yellow Mutant Space Chicken. Perhaps we are all trapped in the gizzard of the Giant Yellow Mutant Space Chicken and at present things are expanding because he is eating. The collapse will begin when he stops.

LLH

 

[Melendwyr]

Wrong.

Wrong.

Sure there is. Distant galaxies really are moving away from us. The source of that movement is the expansion of the Universe, but the movement is real.

No. Those galaxies aren't moving, they're just getting farther away. Moving requires passage through space.

The problem with "tired light" is that it (a) it contravenes the First Law of Thermodynamics (it is impossible) and Quantum Mechanics (it is impossible) and it makes predictions which are not borne out by evidence (it is wrong).

(a) No, and (b) no.

In the expanding universe hypothesis, light does vibrate more slowly the farther it travels.

It's not a restatement of the Doppler Effect, it's just plain wrong.

Who's said it's the Doppler Effect? Doppler shifting is due to relative motion. There IS no relative motion between us and distant parts of the universe (not on a universal scale, at least - other galaxies are of course moving all around). Universal expansion is not movement.

 

[SpaceFluffer]

Melendwyr, please go read up on this stuff before spewing your lack of knowledge onto hapless, unsuspecting individuals who are just trying to learn. Your questions have been well answered by PixyMisa, now go read a book on General Relativity.

You may also like to read: http://sciencenow.sciencemag.org/cgi/content/full/2001/628/1. If you still insist on this hypothesis, you'd better have some damn good reasons why it failed these tests.

As yet further reading, may I suggest that you read your own sig line? FYI, I have some rope and can probably get hold of some oil.

 

[CurtC]

super novi

"Supernovas," please.

 

[Melendwyr]

Melendwyr, please go read up on this stuff before spewing your lack of knowledge onto hapless, unsuspecting individuals who are just trying to learn. Your questions have been well answered by PixyMisa, now go read a book on General Relativity.

Oh, really? If expansion leads to actual movement through space, how can you reconcile galaxies that are moving away faster than light with Relativity? That's what the expansion implies, after all.