Planck length and space expansion.

[Sorcerer]

Since space expands and everything is moving away from everything else. Why is planck's constant, constant? And more specifically why doesn't planck length expand too?

Edited December 24, 2011 by Sorcerer

[mathematic]

Expansion of the universe is effectively anti-gravity and is seen by galaxies moving apart. At a microscopic level the other three forces define what is going on.

[shawnhcorey]

If Planck length expanded too, everything would be expanding at the same rate and it would be impossible to determine if there was any expansion at all. In order for us to see the universe expand, we need something that doesn't expand to compare it to. If everything expanded at the same rate, all comparisons would indicate there there was no change, and hence, no expansion.

 

Of course, the other way to look at it is that the universe is of fixed size and Planck length is shrinking.

[Sorcerer]

Really? I thought cosmologists compared relative brightness of stars (redshift) to conclude the expansion of the universe.

 

I'm not sure but I think perhaps the answer I was looking for was plancks constant is constant because it is coefficient relating the proportionaity of other measurements (E= hc/ wavelength).

 

I'm still having trouble with planck length, trying to pair it with space expansion and also gravity's stretching of space.

 

This just confused me more http://en.wikipedia.org/wiki/Doubly_special_relativity

Edited December 31, 2011 by Sorcerer

[shawnhcorey]

From Wikipedia: The Planck length can be defined from three fundamental physical constants: the speed of light in a vacuum, Planck's constant, and the gravitational constant.

 

The red shift shows that the distance from distance galaxies is increasing as compared to the fundamental physical constants. If Planck length changes, the at least one of the above must change. If it changes in proportion to the expansion of the universe, then the physical constants would change and there would be no detectable change in distance. Everything would balance out. Hence, there would be no red shift.

[michel123456]

From Wikipedia: The Planck length can be defined from three fundamental physical constants: the speed of light in a vacuum, Planck's constant, and the gravitational constant.

 

The red shift shows that the distance from distance galaxies is increasing as compared to the fundamental physical constants. If Planck length changes, the at least one of the above must change. If it changes in proportion to the expansion of the universe, then the physical constants would change and there would be no detectable change in distance. Everything would balance out. Hence, there would be no red shift.

 

Everything would balance out but change appears over time (sounds like tautology). One can observe the change under the condition to be able to look in the past. And we do.