wave length, relativity and doppler.

[gauchecritic]

Thankyou, thankyou, thankyou. That explained it to me, although...

Does a body at rest not exert gravity?

 

[dr_mabeuse]

He loses me completely when he talks about gravity affecting time. As if time is a thing, like potting soil or cornflakes.

My head hurts again.

Your problem comes from thinking of time as an unvarying absolute. It's not. Time can only be measured by things moving in space: the motion of a pendulum, the vibrations of cesium atoms, the number of wavelengths of a certain frequency of light. It has no meaning otherwise. But the pendulum can speed up or slow down, the speed of the vibrations of the Cs atoms can change depending on the gravitational field, and the the number of wavelengths of a certain frequency depends on the speed and vantage of the viewer. So there is no such thing as absolute time.


So as gravity affects matter, it affects time. If we were sucked into a black hole with our cassio on our wrist, time would seem normal to us. But to some observer out in space away from the gravitational field, our time would seem to be massively slowed.

In the basic equation velocity = distance/time, all three terms are malleable according to relativity. The only absolute is the speed of light. To maintain this absolute, both distance (length, usually) and time (the famous slowing of time near relativistic speeds) are modified to preserve the sanctity of light speed.

If you have a rocket zooming past you at light speed with someone walking forward in it, his speed would obviously exceed the speed of light from your perspective, so that's not allowed. What you see is his whole frame of reference slowed down. His space ship is still going light speed, but he's frozen within it. The very atoms in his body slow down. Time has stopped for him. To him, things seem normal, but looking back at you, he sees you moving away from him at the speed of light, so you seem to moving incredibly slowly.

 

[3113]

Your problem comes from thinking of time as an unvarying absolute. It's not. Time can only be measured by things moving in space....It has no meaning otherwise.

Oh yeah? What about these darn wrinkles and gray hairs I'm getting?

 

[DrHappy]

Does a body at rest not exert gravity?

Certainly. The gravity of a body at rest will also cause a redshift on the light that is escaping from it.

 

[midwestyankee]

Oh yeah? What about these darn wrinkles and gray hairs I'm getting?

Certainly. The gravity of a body at rest will also cause a redshift on the light that is escaping from it.

I wonder if this helps explain why so many women of a certain age seem to have reddish hair.

 

[CharleyH]

Oh yeah? What about these darn wrinkles and gray hairs I'm getting?

They will go away when you die. In the meantime, (sorry for your genetic luck) live with them. lol

 

[3113]

Certainly. The gravity of a body at rest will also cause a redshift on the light that is escaping from it.

But a body is never at rest is it? Every object in the universe is moving, if only because it's on some other object that's moving. We're on continents which are moving, on planet Earth which is circling the sun, which is, itself, moving through space, and in a galaxy that's moving as well.

Is anything ever at rest?

 

[shereads]

But a body is never at rest is it? Every object in the universe is moving, if only because it's on some other object that's moving. We're on continents which are moving, on planet Earth which is circling the sun, which is, itself, moving through space, and in a galaxy that's moving as well.

Is anything ever at rest?

Basset Hounds.

 

[gauchecritic]

Is anything ever at rest?

I'm just getting through chapter four quantum and the big bang and no. It seems that absolutely everything in the universe is moving. Not only moving but moving away from everything else. (galaxies at least)

 

[DrHappy]

But a body is never at rest is it? Every object in the universe is moving, if only because it's on some other object that's moving. We're on continents which are moving, on planet Earth which is circling the sun, which is, itself, moving through space, and in a galaxy that's moving as well.

Is anything ever at rest?

It can be at rest relative to another object. In my previous post, I was discussing an observer seeing light that was red shifted as it was emitted from another massive object that was stationary relative to the observer.