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-   -   big bang, schmig bang: everything's just shrinking (http://www.physicsforums.com/showthread.php?t=16515)

Namloh2000 Mar18-04 03:11 PM

big bang, schmig bang: everything's just shrinking
 
okay sure, the redshifts in light measured from distant stars would imply that the space between us and it is getting farther and farther apart.

wouldn't this also be true if all matter was shrinking?

take two inflated balloons spaced a meter apart. if the balloons represented stars and they were both constantly deflating, the space between them both would grow, and this would account for the redshifts we measure... wouldn't they?

Severian596 Mar18-04 03:23 PM

...

This would imply that each star is on its own balloon. What's in between the balloons? It can't be space, because space is what's ON the balloons...

Namloh2000 Mar18-04 03:29 PM

you're looking at the problem wrong, i think. each ballon is a star. the balloon srinks (the star shrinks) - the space between the stars is greater.

this WOULD still prove a redshift

also i've heard that we have observed blueshifted stars before... if anyone wants to fill me in on that.

Severian596 Mar18-04 03:38 PM

The redshift experienced by shrinking stars...would be minimal if not zero. I would investigate the phenomena of "shrinking stars" a bit more.

The type of red**** that cosmologists observe affects every star/galaxy outside our own...every one. Imagine that. Every star that's not in our own galaxy is moving away from us, yet we're not in the center.

Do some more research friend. It's all interesting.

russ_watters Mar18-04 03:46 PM

Quote:

Originally posted by Namloh2000
you're looking at the problem wrong, i think. each ballon is a star. the balloon srinks (the star shrinks) - the space between the stars is greater.

this WOULD still prove a redshift

That would still provide a redshift: for 5 minutes or so until the star disappeared....

The observed redshift is big. For galaxies billions of light years away, the recession velocity exceeds the speed of light. That can only be explained by expanding space.

Your idea would also not explain why redshift varies with distance.
Quote:

also i've heard that we have observed blueshifted stars before... if anyone wants to fill me in on that.
When discussing redshift and expansion of the universe, its galaxies, not stars that you are talking about. Stars in our own galaxy (and a handful of the galaxies closest to us) are so close to us that their proper motion overrides cosmological expansion.

Namloh2000 Mar18-04 03:46 PM

referring the guy with the eldar avatar:

not only shrinking stars... shrinking everything

lets say all matter was shrinking at an alarming rate - that its volume constantly decreased.

also i know the whole history of the big bang theory and i KNOW that we generally understand that everything is moving away from us. THIS IS WHY the only reasonable explanation is that the universe is expanding.

BUT i suggest that this redshift we see from all stars and galaxies that are around us could also be true if everything was shrinking - making it so that the distance (or space) between any two peices of matter is constantsy increasing - accounting for this redshift.

Nereid Mar18-04 03:50 PM

Re: big bang, schmig bang: everything's just shrinking
 
Quote:

Originally posted by Namloh2000
okay sure, the redshifts in light measured from distant stars would imply that the space between us and it is getting farther and farther apart.

wouldn't this also be true if all matter was shrinking?

take two inflated balloons spaced a meter apart. if the balloons represented stars and they were both constantly deflating, the space between them both would grow, and this would account for the redshifts we measure... wouldn't they?

Good question.

Here's a suggestion for how to test the idea: how much 'shrinking' would need to be going on to account for the observed redshifts? For simplicity, start with the Hubble relationship: objects appear (on average*) to be receding from 'us' (this need to be qualified, but let's keep it simple for now) at ~70 km/s/Mpc. "Mpc" is a megaparsec, or 1 million parsecs; a parsec is unit of distance used by astronomers, it's ~3x1013 km.

And yes, there are plenty of blueshifted objects, particularly stars in the Milky Way. There are also a small number of galaxies in the Local Group which show a blueshift.

*plenty of observed deviations from average, a fascinating field of study. For a start, look up Great Attractor - there's a good thread here in GA&C on that.

Namloh2000 Mar18-04 03:51 PM

Quote:

Your idea would also not explain why redshift varies with distance.
yeah i realized this... unless some matter was shrinking faster.

Nereid Mar18-04 07:12 PM

Quote:

Originally posted by Namloh2000
yeah i realized this... unless some matter was shrinking faster.
Please take the time to do the math (OOM is OK) and tell us how much faster. You can pick a few values of z, e.g. 0.05, 0.2, 0.5, 1.3, 3.5, 10

DrMatrix Mar25-04 02:03 AM

Universe expanding and matter shrinking are two ways of looking at the same thing. Consider that our unit of distance is a matter of definition. We define the meter based upon how far light travels in a certain fraction of a second. By this definition of distance. The universe is expanding and (idealized) rigid rods have a fixed length. We could define distance in such a way that space is not expanding, but rigid rods (and the meter) are shrinking.

Units of distance and time are matters of definition.

russ_watters Mar25-04 06:43 AM

DrMatrix, did you read the entire thread?

Severian596 Mar25-04 08:22 AM

Quote:

Originally posted by Severian596
The type of red**** that cosmologists observe...
I just realized I said red**** instead of redshift...oh **** I did it again.

[:D]

Severian596 Mar25-04 08:27 AM

Quote:

Originally posted by Nereid
Please take the time to do the math (OOM is OK) and tell us how much faster. You can pick a few values of z, e.g. 0.05, 0.2, 0.5, 1.3, 3.5, 10
This is pretty overwhelming. I like the idea of looking at things from a new perspective, kinda like at the end of Men in Black when some strange kids are playing marbles and the marbles have galaxies in them. It is dizzying to think of how MUCH matter must be shrinking, though, and then what would the consequences be of density? Would our density change? Or to the atoms themselves get smaller too, so the "space betwee" atoms doesn't effectively decrease.

Kudos to the new perspective though.

DrMatrix Mar25-04 09:05 AM

Quote:

Originally posted by russ_watters
DrMatrix, did you read the entire thread?
Yeah. Are you refering to your assertion that shrinking matter "not explain why redshift varies with distance"? I think it must:

Since expanding space and shrinking matter are two equivelent ways of describing the same thing (the only difference being the definition of our unit of distance), if you have red shift in one, you must have red shift in the other.

Is there something else I missed?

Nereid Mar25-04 09:43 AM

Quote:

Originally posted by DrMatrix
Yeah. Are you refering to your assertion that shrinking matter "not explain why redshift varies with distance"? I think it must:

Since expanding space and shrinking matter are two equivelent ways of describing the same thing (the only difference being the definition of our unit of distance), if you have red shift in one, you must have red shift in the other.

Is there something else I missed?

If they are, indeed, 'equivalent', is there any way - through experiment or observation - to tell the two apart?

If not, then it's surely just a question of personal taste which you prefer to use to do your physics.

If it is possible to tell them apart, please give us some suggestions on how.

russ_watters Mar25-04 09:48 AM

Quote:

Originally posted by DrMatrix
Is there something else I missed?
Several things (essentially every point made above still applies):

First off, there is only a finite amount of shrinkage that can occur (otherwise an object could disappear). The rate must slow hyperbolically as the object gets smaller and smaller, whereas expansion can proceed linearly, hyperbolically, parabolically, etc.

Second, if our meter sticks (the units) were changing, we would indeed observe exactly the same thing as we do now: but that includes redshift and still includes expansion! Whether or not our meter-sticks are changing, the distance between objects would still need to be expanding according to that shrinking meter stick.

Third, speed of light. Observing objects apparently moving faster than the speed of light requires expansion of space. The surface of an object can't recede faster than the speed of light.

Fourth, the type of effect you describe would not be observable from within the universe (necessary result of point 2) and as a result, even if it exists it can be ignored by everyone except God.

I think you may be mixing up two different concepts: observable shrinkage and unobservable shrinkage.

If our meter sticks were shrinking, it would be just like applying a conversion factor to our numbers (SI to English). There would be no observable change in the structure of the universe as a result of such shrinkage and as such, it wouldn't affect any of our laws of physics.

Namloh was suggesting shrinkage as a cause of observed red-shift. For that to even show up in our measurements, objects must be shrinking while our metersticks would not.

DrMatrix Mar25-04 02:05 PM

Quote:

If our meter sticks were shrinking, it would be just like applying a conversion factor to our numbers (SI to English). There would be no observable change in the structure of the universe as a result of such shrinkage and as such, it wouldn't affect any of our laws of physics.
That is exactly my point. There is no way to decide which model (expanding space or shrinking matter) is correct. Both are matters of definition. Our current definition of a unit of length is preferred, not because it is more correct, but because it is more useful -- our(idealized) rigid rods do not change length.
Quote:

Namloh was suggesting shrinkage as a cause of observed red-shift. For that to even show up in our measurements, objects must be shrinking while our metersticks would not.
Well, if expanding space explains redshift and shrinking matter is just applying a conversion factor to our unit of length. Shrinking matter must give the same results. It's just another way of expressing the same thing.

To answer Nereid's questions: Since the difference is a matter of definition, there is no way to tell them apart. The difference is descriptive.

russ_watters Mar25-04 03:22 PM

Quote:

Originally posted by DrMatrix
That is exactly my point. There is no way to decide which model (expanding space or shrinking matter) is correct.
No. Since there is no evidence of either, neither are assumed. Again, you're mixing up two different concepts: If an effect produces no observable phenomenon in the universe, how does it explain an observable phenomenon in the universe?
Quote:

Well, if expanding space explains redshift and shrinking matter is just applying a conversion factor to our unit of length. Shrinking matter must give the same results. It's just another way of expressing the same thing.
No, it isn't. With one, everthing including the meter stick expands/contracts at the same rate and as a result, no expansion or contraction (ie, no redshift) is observed. With the other, the universe expands/contracts(expands) and the meter stick does not, resulting in an observed blueshift/redshift(redshift).

There have been several threads in the past asking the question "If I woke up tomorrow and everything in the universe had doubled in size, how would I know?" The answer is, you wouldn't - there would be no evidence of it. But cosmological redshift is a piece of evidence for something. But for what...?


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