I am aware of what redshift is. What I don’t understand is how you think a metre bar can expand and the speed of light increase in lockstep with it such than we can’t measure the change.
Let’s say we have a metre bar that’s currently one unit long, and we measure it to be one metre long. There’s also a galaxy a billion light years away.
Let’s say the universe doubles in size after a billion years. The metre bar is two units long, but we still measure it to be one metre long, because the speed of light has doubled (presumably). We measure the light as the same length. The light from the galaxy has now reached us, and is twice as long, but is also moving twice as fast, so the wavelength stays the same. We measure the light as the same length.
Do you see my issue with this situation? How can the measured length of light change (redshift) while the measured length of light also stay the same (metre bar)?
Either redshift isn’t caused by expansion, the fundamental forces and constants are changing as we expand, or space is expanding but matter isn’t. We have good corroborating evidence that redshift is caused primarily by expansion. We also have evidence that the laws of physics haven’t changed significantly in at least the last 2 billion years or across the universe. And lastly, we can measure the acceleration of expansion by several corroborating methods, including redshift.
I’d love to be proven wrong here, the implications of gluons being streched by expansion is fascinating.
So you assume the speed of light is the same between references frames. There not. It’s always the same. The definition of a second changes such that the speed of light is always the same.
That’s relativity.
Yes, relatively means that light appears to move at c in every inertial reference frame. That doesn’t change how we measure distance in a single reference frame.
How can a metre bar be measured as a metre when it’s one unit and two units long? We’re measuring the bar in it’s own reference frame each time, so relatively causes no change. Either c increased, or time slowed down to match the expansion of space. Either way, light doesn’t get redshifted by expansion.
Help me understand, how does light appear to change speed over time in the same reference frame? How do we see a change of distance affect light between galaxies, but not between atoms?
The reason the speed of light doesn change is because rthe universe bends the rules of time to make it the same. So as the universe expands, the speed of light stays the same because the definition of time changes.
Like I said. The expansion of the universe isn’t space expanding, it’s the definition of distance that’s expanding. Yes time is being fucked with as part of the expansion. But the universe doesn’t hold distance or time as constant frames to compare to. As speed is only calculated with a frame of reference. Where distance is a little more fundamental to the universe.
Because the scale is so so much less. Like 73 km/s/Mpc.
So the rate of something to the scale of 10^-9m, would be somewhere in the order of 10^-25m/s. Which is much much smaller than anything with the attoms itself.
But the distance is always the same. A meter is still a meter in all points of time. But it’s still bigger.
