Inflation problem

[Andeh]

One more:

 

If I were to be traveling at high speed, I wouldnt be able to observe my own time dilation. My watch, or any other device that measures time by counting interection that happen at a constant rate, wouldnt appear to run slower because it's motions are also being dilated. Only to an outside observer would it appear that time is running slower for me.

 

The same could be said for space. If measured two points with a ruler to be four inches appart, then somehow expanded space, the points would still appear to be four inches apart internally. Even though, to an outside observer, the distance between them grew, so did the internal observer's measuring device.

 

here's where I'm going with this:

We say the universe is expanding because we can see things moving away from each other. That expansion has been described as space itslef expanding. But considering what I said above, even if space were expanding, we shouldnt be able to observe it. So why, then, can we observe the universe to be expanding, which it almost certainly is?

 

explainations?

[DrRocket]

One more:

 

If I were to be traveling at high speed, I wouldnt be able to observe my own time dilation. My watch, or any other device that measures time by counting interection that happen at a constant rate, wouldnt appear to run slower because it's motions are also being dilated. Only to an outside observer would it appear that time is running slower for me.

 

In any fixed inertial reference frame things are always pretty "normal". Time dilation and length contraction are merely relations between two distinct reference frames in relative motion.

 

But the reason that you don't perceive time dilation in your own reference frame is NOT because the mechanism of your watch "is also being dilated". That would only make sense if there were such a thing as absolute motion, but there is not. Your watch appears to work normally because your watch is indeed working normally. There is no reason that it should not work normally -- it is at rest in your reference frame.

 

The same could be said for space. If measured two points with a ruler to be four inches appart, then somehow expanded space, the points would still appear to be four inches apart internally. Even though, to an outside observer, the distance between them grew, so did the internal observer's measuring device.

 

Yes, the same can be said for space. But you didn't say it.

 

There is no such thing as an outside or internal observer. There are only observers tied to specirfic reference frames.

 

You are mixing special and general relativity. The cosmological expansion of space is a phenomena described in models based on general relativity and has nothing to do with relative motion or special relativity.

 

If space were to expand points would appear to move apart to any and all observers. The expansion of space is based on measurements tied to the intrinsic, and invariant, Lorentzian metric of spacetime. It has nothing to do with relative motion or varying reference frames.

 

 

 

 

 

 

 

 

 

 

here's where I'm going with this:

We say the universe is expanding because we can see things moving away from each other. That expansion has been described as space itslef expanding. But considering what I said above, even if space were expanding, we shouldnt be able to observe it. So why, then, can we observe the universe to be expanding, which it almost certainly is?

 

explainations?

 

You took a wrong turn.

 

See above.

 

This is actually a very subtle topic. Even to describe, in general relativity, what is meant by "space" and "expansion of space" is non-trivial and takes significant background in the differential geometry that is the basis of general relativity.

 

If you really want to study this in detail you will need to undertake a serious study of general relativity, on par with the text Gravitation by Misner, Thorne and Wheeler. Though, you might want to start with this thread: http://www.scienceforums.net/topic/33180-cosmo-basics/

[MigL]

By all means take DrR's advice, He'll seldom , if ever, steer you wrong, but...

 

The expansion of the universe can simply be explaned as a global phenomena whereas locally, the expansion can be mitigated or even reversed ( attraction ) by other forces. So even though we can observe universal expansion, the Andromeda galaxy is moving towards our galaxy because gravitational force overcomes the expansion locally. We also don't get larger and our molecules and atoms don't move farther apart because the electomagnetic force overcomes the expansion. And the constituents of the atoms themselves don't expand because the strong force keeps nucleons from expanding.

 

In effect what you were stating about yardsticks ( even if a little confused as mentioned by DrR ) doesn't apply here. Our 'yardsticks' are not expanding so we CAN measure universal expansion.

Edited January 14, 2012 by MigL

[Andeh]

Thanks for the explaination.