3 ms·
What's still not clear is how I know the other point on the surface of the ballon is moving away from me? I measure it as 9 tick marks away. After inflation i
by JackFr 7y ago
What's still not clear is how I know the other point on the surface of the ballon is moving away from me? I measure it as 9 tick marks away. After inflation it's still nine tick marks.
That is to say, what is my ruler that is untethered to the surface of the balloon?
- Tenemo 7y agoYour ruler is absolute distances, like the speed of light. You can inflate or deflate the balloon and the number of marks on its surface won't change. But the time required for the light to travel between them will.
- zaroth 7y agoStupid question - How do you know for certain it isn’t just that light is slowing down? Relativity probably doesn’t work this way at all, but if light did actually slow down, would it be perceived by us as light moving at the same speed across a greater distance?
- deleted 7y ago[deleted]
- mdturnerphys 7y agoI asked Ann Nelson (look her up) this when I audited her cosmology class in grad school, thinking I'd come up with a great new idea. She said yes, it's equivalent to the speed of light changing, and then moved on.
- simonh 7y agoBear in mind that time is not universal. For the speed of light to change over time, it would change at different rates for observers in different reference frames, and this difference would be measurable. As to the previous question about relative size. If the universe doubled in size, the objects within it such as atoms don’t also double in size. Gravity and the atomic forces don’t change, so eg the size of stable electron orbits or planetary orbits don’t double in size.
- pedrosorio 7y agohttps://en.m.wikipedia.org/wiki/Variable_speed_of_light https://en.m.wikipedia.org/wiki/Variable_speed_of_light
- bananabreakfast 7y agoNot exactly. Remember, we're not timing the light's transit. We're observing a redshift of it's frequency which could not be caused by c simply decreasing over time.
- allovernow 7y agoI think physical forces (electromagnetism, gravity, strong/weak nuclear) probably become weaker even though your metric (9 ticks) stays the same. I'm just guessing here, that's the only consequence I can think of.
- bananabreakfast 7y agoIt's incorrect to think with this analogy. There is no ruler reaching across the universe, growing with it. It is not the meter that is growing, that's impossible. Instead you must see it as it is, which is that there are more meters continuously appearing in all of space.