Space and time

[RichIsnang]

Space has always been expanding as long as the universe has been around, also time has always moved forwards as long as the universe has been around.

 

Einstein linked space and time in his view of space-time, maybe the universe expanding and time moving forwards are linked?

 

Gravity causes objects to accelerate, get faster with time, as space-time gets warped.

 

Thoughts?

[IM Egdall]

Space has always been expanding as long as the universe has been around, also time has always moved forwards as long as the universe has been around.

 

Einstein linked space and time in his view of space-time, maybe the universe expanding and time moving forwards are linked?

 

Gravity causes objects to accelerate, get faster with time, as space-time gets warped.

 

Thoughts?

 

Gravity is the warping of space-time. They are one and the same.

Edited March 30, 2012 by IM Egdall

[questionposter]

Gravity is the warping of space-time. They are one and the same.

 

I think the fabric of space-time harbors both space and time, but I don't think the math actually shows the gravity actually = time. If I travel at 20 kilometers per hour, what's my gravity?

[the asinine cretin]

Uneducated layman here.

 

I know that motion (i.e., velocity) is related to mass and the rate of time by special relativity (e.g., the Lorentz factor, relativistic mass, time dilation, and all that.) I don't know how that could be automatically connected with the expanding universe and the arrow of time.

 

My understanding is that universal expansion does not impart momentum to anything, and thus special relativity is not applicable (at least not applicable in terms of relativistic effects or whatever). Distant galaxies may appear to us as receding at relativistic and even superluminal speeds, but that is not related to their velocity in an inertial reference frame. The space itself between things is - if I may use a metaphor - stretching, and it's only relevant on cosmological scales. This is why light from those distant galaxies red shifts. It is not because the galaxies are moving so fast in an opposing direction analogous to the sonic Doppler effect of a passing train, but rather that the fabric of space itself expands and as it travels those vast distances the light is, as it were, stretched into the red spectrum and beyond.

 

Anyway, my point is just that I don't know how special relativity connects the metric expansion of space and the arrow of time. It would be pretty neat if it did. I suppose what you're implying would merge general relativity and special relativity somehow. I look forward to comments from trained physicists.

 

Again, I'm not even remotely a physicist and I may delete this post if it ends up being deemed idiotic.

Edited March 31, 2012 by the asinine cretin

[IM Egdall]

I think the fabric of space-time harbors both space and time, but I don't think the math actually shows the gravity actually = time. If I travel at 20 kilometers per hour, what's my gravity?

 

I did not say gravity = time. I said gravity is the warping of space-time. Per general relativity, both space and time are warped in the presence of mass/energy. The mass and energy of the Earth, for example, warps space and time in its vicinity. (Clocks run slower and radial distances are stretched.)

 

This warping of time and space causes objects to fall to the Earth, holds me in my seat as I type this, holds the Moon in it orbit around the Earth, etc. In short, all phenomena we attribute to "gravity" are the result of the warping of space and time (spacetime curvature). This is what the mathematics of general relativity shows.