The Big Rescaling

[tetrahedron]

Hi folks. Here's a question- why is it that in both the popular imagination as well as in a lot (most, all?) professional writing people keep referring to the initial event(s) of the universe as a 'bang', when all it really is is a relative rescaling of matter and energy versus space and time? I'm not the first to be a bit upset by this. The implied imagery, I feel, puts a damper on the ability to utilize other mental models.

 

Similarly, when considering Hubble expansion, everyone I know takes the position that matter is unchanging, but the universe is growing bigger. Well there's no way to support this notion when taking relative frames of reference into account. Matter could be shrinking just as easily, and with all the metrics save light frequency/wavelength going along for the ride, how could we ever tell the difference.

 

Anyway, I've ranted my rant. Now for the responses, should any brave souls care to reply.

 

Jess Tauber

[JMJones0424]

The term "Big Bang" was originally meant to be a derogatory term used by Fred Hoyle, a steady state proponent. It is unfortunate that it has stuck, as it is incorrect to envision an explosion, but the term stuck.

 

As far as matter shrinking rather than the metric expansion of the universe, the two are not interchangeable. If matter were shrinking, density of stars would be increasing, but the size of galaxies, and therefore distance between galaxies, would remain the same. Stellar physics wouldn't be the same, and redshift would not be observed.

Edited March 9, 2012 by JMJones0424

[tetrahedron]

Stars would contain the same number of shrinking atoms. Their relative density shouldn't change if one measures this with shrinking devices. But as the atoms shrink relative to the larger spatial frame, the apparent distances between separated bodies should increase, unless they are being attracted by and falling into each other in step with the shrinkage. Use the balloon analogy- inflate the balloon and space increases, but we need still to account for the failure of all matter to expand with spacetime- any dots on the surface of the balloon should spread out- whether galaxies, planets, atoms, unless somehow smaller bodies are immune, and what is the explanation for that? Or we can hold the balloon constant in size, and the density of the dots increases as they fall into each other. Or we can have any combination of the two opposites. All forces have to participate in balancing things out. Point particles of course can't expand or contract (unless you want to include higher/hidden dimensions) in space, but perhaps they can in TIME?

 

Jess Tauber

 

 

The term "Big Bang" was originally meant to be a derogatory term used by Fred Hoyle, a steady state proponent. It is unfortunate that it has stuck, as it is incorrect to envision an explosion, but the term stuck.

 

As far as matter shrinking rather than the metric expansion of the universe, the two are not interchangeable. If matter were shrinking, density of stars would be increasing, but the size of galaxies, and therefore distance between galaxies, would remain the same. Stellar physics wouldn't be the same, and redshift would not be observed.

[JMJones0424]

Stars would contain the same number of shrinking atoms. Their relative density shouldn't change if one measures this with shrinking devices. But as the atoms shrink relative to the larger spatial frame, the apparent distances between separated bodies should increase, unless they are being attracted by and falling into each other in step with the shrinkage.

Right. Using today's ruler, a star one billion years from now would be smaller, but its center of gravity would be the same distance relative to the center of gravity of the galaxy. Though the individual stars are shrinking, the galaxy would not. Shrinking matter does not explain redshift.

 

Use the balloon analogy- inflate the balloon and space increases, but we need still to account for the failure of all matter to expand with spacetime- any dots on the surface of the balloon should spread out- whether galaxies, planets, atoms, unless somehow smaller bodies are immune, and what is the explanation for that?

Matter is neither expanding nor shrinking. Space is expanding.

 

 

Or we can hold the balloon constant in size, and the density of the dots increases as they fall into each other. Or we can have any combination of the two opposites. All forces have to participate in balancing things out. Point particles of course can't expand or contract (unless you want to include higher/hidden dimensions) in space, but perhaps they can in TIME?

 

You're starting to lose me now.

[JMJones0424]

I think I was too dismissive and didn't appropriately answer one of your questions previously.

 

Use the balloon analogy- inflate the balloon and space increases, but we need still to account for the failure of all matter to expand with spacetime- any dots on the surface of the balloon should spread out- whether galaxies, planets, atoms, unless somehow smaller bodies are immune, and what is the explanation for that?

 

You previously noted how the term "Big Bang" is misleading. I would place the balloon analogy in that category as well. The balloon analogy is meant to illustrate that every observer can see himself as the center of expansion in the universe. The usual conceptual problem with the balloon analogy is that the balloon exists in three dimensions, while the analogy considers only the two-dimensional surface of the balloon. You have identified another weakness, that the dots drawn on the balloon representing galaxies stretch as the balloon inflates.

 

The expansion of the universe is significant on scales much larger than the size of a galaxy, but on smaller scales, it is insufficient to overcome gravitational attraction. Bodies that are bound to each other gravitationally in solar systems, galaxies, and even galaxy clusters, do not display an increase of distance between each other because the expansion is negligible compared to the gravitational attraction.

 

One of the best resources available on the internet for answering cosmology questions like these is Ned Wright's Cosmology Tutorial. From his Cosmology FAQ:

 

 

Why doesn't the Solar System expand if the whole Universe is expanding?

 

This question is best answered in the coordinate system where the galaxies change their positions. The galaxies are receding from us because they started out receding from us, and the force of gravity just causes an acceleration that causes them to slow down, or speed up in the case of an accelerating expansion. Planets are going around the Sun in fixed size orbits because they are bound to the Sun. Everything is just moving under the influence of Newton's laws (with very slight modifications due to relativity). For the technically minded, Cooperstock et al. computes that the influence of the cosmological expansion on the Earth's orbit around the Sun amounts to a growth by only one part in a septillion over the age of the Solar System. This effect is caused by the cosmological background density within the Solar System going down as the Universe expands, which may or may not happen depending on the nature of the dark matter. The mass loss of the Sun due to its luminosity and the Solar wind leads to a much larger [but still tiny] growth of the Earth's orbit which has nothing to do with the expansion of the Universe. Even on the much larger (million light year) scale of clusters of galaxies, the effect of the expansion of the Universe is 10 million times smaller than the gravitational binding of the cluster.

 

Edited March 9, 2012 by JMJones0424

[tetrahedron]

But what if there is motion of bodies towards each other compensating for expansion of space? Perhaps not uniform but scale-dependent? Remember there are alternative theories of gravity that take this point of view. We might not be able to perceive it on the local set of scales (and only can for large scales because of the cumulative time displacement summing).

 

Whether space expands or matter shrinks we still have to end up with the observations we've already made about the universe, so any story we tell has to be consistent with the latter state of affairs. I remember reading and hearing about the idea that because of relativity we can't assume everyone has the same reference frame throughout spacetime. Other regions may be in some absolute sense radically different from ours, assuming one could observe them in real time simultaneously (which of course we can't). But the laws of physics have to re-equilibrate to maintain consistency regardless, as one goes from one region to any other- the 'fundamentals' are anything but. Higher level interactions are conserved. Very common in physics.

 

Jess Tauber

[JMJones0424]

But what if there is motion of bodies towards each other compensating for expansion of space?

What about it? There are galaxies that are not redshifted. They are moving towards us. I do not see how this favors a matter shrinking explanation over a space expanding explanation.

 

Remember there are alternative theories of gravity that take this point of view.

What are they?

 

Whether space expands or matter shrinks we still have to end up with the observations we've already made about the universe, so any story we tell has to be consistent with the latter state of affairs.

Agreed. As I have noted, shrinking matter does not explain redshift. Therefore there is no reason to assume that matter is shrinking because we observe redshift.

 

I remember reading and hearing about the idea that because of relativity we can't assume everyone has the same reference frame throughout spacetime. Other regions may be in some absolute sense radically different from ours, assuming one could observe them in real time simultaneously (which of course we can't).

I am not sure, but I can guess at what you are referring to. One of the fundamental assumptions of physics, one that predates general and special relativity, is that physical laws are applicable in any inertial reference frame. This is referred to as Galilean relativity and is illustrated by the fact that when you are traveling in a car at 50 miles per hour and drop a cup of coffee, you expect that cup to react, relative to you, the same as if you were outside the car standing stationary on the sidewalk and dropped the cup of coffee. Though I may be wrong, I think you are confused as to what an inertial reference frame is. I can sympathize. It isn't a particularly easy concept to understand, and there are many threads here where people seem to be talking past each other trying to explain the concept. Simply put, as long as you are not accelerating, the laws of physics are the same for you as they are for me, regardless of the difference in our velocity relative to each other. This means that there is no unique goalpost by which we can measure speed. There is no universal reference frame.

[tetrahedron]

I can't answer you about the reference frames- this was something discussed on a recent science show as a 'new' position, not exactly the most professional of venues, but by someone supposedly in the field. On the other hand, as for the redshift, that would be because of blueshifting of frequencies produced by shrinking matter. So relative to old light, which in a noninflating univese would NOT be shifting, newer light would have its frequency increased, because of decreasing distance between quantum levels.

 

Some time ago I was interested in converted Hubble expansion rates down to Planck and atomic scales, just to see what they would look like, but never got around to it. How much shrinkage/expansion is there, relative to such units?

 

Jess Tauber