26 Aug 14
Originally posted by twhiteheadOkay, that is better.
There is no outer part, and no, matter is not accelerated by the expansion of space. As soon as you stop thinking of it as an explosion, you will realise your error.
If we look at galaxies around us, apart from the very closest ones that are gravitationally bound to our own, they all appear to be moving away from us. However, they are not moving through space away from us, instead, the space between us and them is expanding.
What is causing the space to expand between us?
26 Aug 14
Originally posted by Metal BrainAccording to Einstein matter bends space-time and that discrepancy in time causes the force of gravity.
According to Einstein matter bends space-time and that discrepancy in time causes the force of gravity. Time on the surface of the Earth measured by an atomic clock is slightly different than an atomic clock measuring time in Earth's orbit in a satellite, right?
No.
Time on the surface of the Earth measured by an atomic clock is slightly different than an atomic clock measuring time in Earth's orbit in a satellite, right?
Yes.
26 Aug 14
Originally posted by KazetNagorrahttp://www.dummies.com/how-to/content/einsteins-general-relativity-theory-gravity-as-geo.html
[b]According to Einstein matter bends space-time and that discrepancy in time causes the force of gravity.
No.
Time on the surface of the Earth measured by an atomic clock is slightly different than an atomic clock measuring time in Earth's orbit in a satellite, right?
Yes.[/b]
26 Aug 14
Originally posted by Metal BrainI don't know. I believe cosmologists thing it has to do with space having non-zero energy, also known as dark energy, but to be honest it is not something I really understand. It could be that dark energy only accounts for the acceleration in the expansion and there are other reasons for the initial expansion itself.
What is causing the space to expand between us?
However, the evidence that space in the universe is expanding, is pretty solid.
26 Aug 14
3 edits
Originally posted by Metal BrainAn atomic clock would tick slightly slower on a satellite orbiting relatively close to the Earth than one stationary on the surface of the Earth but would tick slightly faster on a satellite orbiting in a geostationary orbit than one stationary on the surface of the Earth.
Would an atomic clock measure time slower on Earth than on the satellite? I think that is the way I remember it. I could be wrong though.
This is because how fast a clock ticks depends not only on how far in it is into a gravity well (actually, it is a bit more complicated than that ) but also its relative velocity and those two things can have apposing time dilation effects + it is effected by acceleration whether that acceleration is caused by gravity or something else.
26 Aug 14
1 edit
Originally posted by Metal BrainAs time passes space expands. Let's look at one spacial dimension plus time. Imagine the one space dimension as a circle which is expanding. Now let's look at the space time as a whole. It would look like a the surface of a cone, or, if the acceleration is accelerating, like a trumpet. So space expands with increasing time. It's difficult to fit the notion of "expanding time" into this picture. You are right in your later post that the rate clocks tick depends on position, but that is not normally interpreted in terms of time expanding, since the "arrow of time" can't be reversed we can have space expanding with increasing time in a well defined way. But there is no irreversible "arrow of space" - we can always turn round and face the other way which is not possible with time - so time increasing with space isn't a clearly defined concept.
Here is my theory:
Space and time are unequivocally linked. Space cannot expand unless time expands with it. Space expanding explains why the universe is expanding. Time expanding explains why the universe is accelerating.
Now, tell me. What is wrong with my theory?
27 Aug 14
1 edit
How would we measure expanding time? What would it mean for time to expand?
I realize that time is relative and runs at different speeds in different places, but for time to expand as a whole, one would expect the past and future to be expanding too. This would mean the past is not fixed, but is changing over time. Surely I just introduced a paradox - or possibly just an incoherency?
27 Aug 14
Originally posted by twhiteheadTime could be expanding but I don't think we would know it. It would take every atom, every clock, every biological system with it so we would never know if indeed the flow of time changed. I wonder if the accelerated expansion could be attributed to a change in the flow of time?
How would we measure expanding time? What would it mean for time to expand?
I realize that time is relative and runs at different speeds in different places, but for time to expand as a whole, one would expect the past and future to be expanding too. This would mean the past is not fixed, but is changing over time. Surely I just introduced a paradox - or possibly just an incoherency?
What effects could we check for that?
27 Aug 14
Originally posted by sonhouseThis doesn't answer the question but, if it is supposed to by physically real but you cannot measure/detect nor deduce it, it is not part of science.
Time could be expanding but I don't think we would know it. It would take every atom, every clock, every biological system with it so we would never know if indeed the flow of time changed. I wonder if the accelerated expansion could be attributed to a change in the flow of time?
What effects could we check for that?
29 Aug 14
Originally posted by humyThere any such effect would languish till a newer generation of scientists come up with ways to actually detect such changes, maybe anayzing the CMB or some such.
This doesn't answer the question but, if it is supposed to by physically real but you cannot measure/detect nor deduce it, it is not part of science.
I'm not taking the position time is changing, just hypothesizing.
31 Aug 14
Originally posted by Metal BrainInteresting idea. This could explain how a gravitational force is able to pull rather than push, and it would mean gravitational wells are created by differences in time... time being the variable factor in the fabric of space-time. Time dilation (caused by mass) naturally causes mass to be drawn toward mass. Is this what you mean by time dilation causing gravity?
You do realize that time dilation causes gravity, right?
I haven't found a link for this yet, but an experiment was done several years ago in Russia where an object was suspended in a vacuum and the temp was dropped to just above absolute zero. The object became lighter as the internal activity of the object slowed down. Some of that motion was transferred into a spin of the object itself, but it was the object becoming lighter that I thought was interesting... it suggested gravity could be a function of activity at the atomic level.
Mass displacing space as being the cause of gravity never made much sense to me, because empty space can't be displaced... space can be occupied, but (by definition) it's not displaced.