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.
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.
And yet you said that a metre bar would be larger yet measure the same. If all the aspects of the universe are expanding in lockstep such that any distance appears constant, then redshift caused by expansion is impossible.
If the increasing distance between atoms is unmeasurable, then so too must be the increasing distance between galaxies be undetectable.
LIGO can detect changes of distance on the order of 10⁻²¹, and it should be increasing in effective length by 2×10⁻¹²m/s, yet I don’t see any mention of any large interferometer measuring anything but gravitational waves, and I don’t see any large time-dependent components of LIGOs systemic error data.
We also can measure the increasing distance of galaxies via redshift, so unless you can explain how light from galaxies is different from the light in a large interferometer, I must conclude that the interferometers aren’t expanding at the same rate as the observed expansion of the universe.
We aren’t expanding like the universe is expanding.
We can still measure the red/blue shift to find the star, but if you don’t correct for it, it will be wrong.
Also I don’t know enough about gravitational waves wo know how it would be effected by the expansion of the universe.
But remember when LIGO measures, it’s not measuring absolute values that we would see drift in. It’s all relative measurements from a short time period prior. It would follow in lockstep with the expansion.
Also gravitational waves arent particles. They’re disturbances in the fabric of the universe. So they don’t behave like standard waves do. They have their own wave mechanics that I haven’t studied.
And light is having its wavelength stretched. Speed of is not proportional to frequency in a vacuum only the permittivity and permeability of free space. So it’s wavelength is getting expanded without
But again. Space isn’t expanding. Distance is.
Also that’s not how informeters work.
They compare distance across two lines. They can only detect the differences between those lines. Because expansion is universal in all directions, it’s not detectable on informeters.
Actually that’s a good point about interferometers, the only detectable change whould be in the difference between each arm’s length.
Gravitational waves do behave like EM waves, we’ve seen a neutron star merger simultaneously in gravity and light. If there was a difference, one observation would lag behind.
How exactly would we measure an absolute value of distance? The whole thing about general relativity is than everything is relative. If everything was scaled up such that the fine structure constant stayed the same, we wouldn’t be able to measure a difference.
Which brings us back to the question I have with your model: How can a changing distance be measured by light to be the same (metre bar) but also different (redshift)? If light is scaling with the rest of the universe, it shouldn’t get shifted. This in the crux of my confusion.
The answer is there’s no such thing as absolute distance. Because there’s no such thing as absolute position. Quantum garuntees inaccuracies in position.
And your right. We can’t actually measure the expansion of the universe directly. It’s actually because of the red shift we do.
The reason we can see the red shift is because the universe holds the speed of light in a vacuum constant.
So if the universe is expanding, and the speed of light is expanding with it, in-order for the speed of light to stay the same, it has to travel more distance in a time. Meaning it’s stretching it’s wavelength as it moves. Just like something moving away from us does. IIRC it’s because of observations that everything is constantly moving further from us, the further out you go, the faster it’s moving away.
But everything is moving from everything, including itself.
I do apologize if I’m a little muddy, I did my physics degree about a decade ago.
Edit as for why gravitational waves travel at the same as E&M waves is because “information” is what travels at the speed of light. For an electro magnetic wave that’s disturbances in E&M. For gravity that’s ripples in the fabric of space-time. For quantum there’s experiments showing that entangled particles will collapse together, if sperated by distance, the lag time is also the speed of light.
EDIT 2:
The only thing faster than the speed of light, is actually the expansion of the universe beyond a certain distance. Don’t remember what it is. But because distance istself is expanding, that’s proportional to distance. So the expansion rate is actually faster than the speed of light far enough out. But no SINGLE point is expanding faster than the speed of light.
If there’s no such thing as absolute distance, then how can you say that a metre bar (and the metre) is larger than it used to be?
If distance is relative, and matter isn’t expanding relative to anything else, then matter isn’t expanding.
We ultimately define distance in terms of c, and the fundamental forces agree with this. We do not observe atoms expanding, but we do observe the space between galaxies expanding. Presumably the space we occupy is also expanding, but it’s such a small effect as to be irrelevant.
Back to my original question, is the boundary between irrelevantly small and detectable above or below the galactic scale?
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.
And yet you said that a metre bar would be larger yet measure the same. If all the aspects of the universe are expanding in lockstep such that any distance appears constant, then redshift caused by expansion is impossible.
If the increasing distance between atoms is unmeasurable, then so too must be the increasing distance between galaxies be undetectable.
LIGO can detect changes of distance on the order of 10⁻²¹, and it should be increasing in effective length by 2×10⁻¹²m/s, yet I don’t see any mention of any large interferometer measuring anything but gravitational waves, and I don’t see any large time-dependent components of LIGOs systemic error data.
We also can measure the increasing distance of galaxies via redshift, so unless you can explain how light from galaxies is different from the light in a large interferometer, I must conclude that the interferometers aren’t expanding at the same rate as the observed expansion of the universe.
We aren’t expanding like the universe is expanding.
We can still measure the red/blue shift to find the star, but if you don’t correct for it, it will be wrong.
Also I don’t know enough about gravitational waves wo know how it would be effected by the expansion of the universe.
But remember when LIGO measures, it’s not measuring absolute values that we would see drift in. It’s all relative measurements from a short time period prior. It would follow in lockstep with the expansion.
Also gravitational waves arent particles. They’re disturbances in the fabric of the universe. So they don’t behave like standard waves do. They have their own wave mechanics that I haven’t studied.
And light is having its wavelength stretched. Speed of is not proportional to frequency in a vacuum only the permittivity and permeability of free space. So it’s wavelength is getting expanded without
But again. Space isn’t expanding. Distance is.
Also that’s not how informeters work.
They compare distance across two lines. They can only detect the differences between those lines. Because expansion is universal in all directions, it’s not detectable on informeters.
Actually that’s a good point about interferometers, the only detectable change whould be in the difference between each arm’s length.
Gravitational waves do behave like EM waves, we’ve seen a neutron star merger simultaneously in gravity and light. If there was a difference, one observation would lag behind.
How exactly would we measure an absolute value of distance? The whole thing about general relativity is than everything is relative. If everything was scaled up such that the fine structure constant stayed the same, we wouldn’t be able to measure a difference.
Which brings us back to the question I have with your model: How can a changing distance be measured by light to be the same (metre bar) but also different (redshift)? If light is scaling with the rest of the universe, it shouldn’t get shifted. This in the crux of my confusion.
The answer is there’s no such thing as absolute distance. Because there’s no such thing as absolute position. Quantum garuntees inaccuracies in position.
And your right. We can’t actually measure the expansion of the universe directly. It’s actually because of the red shift we do.
The reason we can see the red shift is because the universe holds the speed of light in a vacuum constant.
So if the universe is expanding, and the speed of light is expanding with it, in-order for the speed of light to stay the same, it has to travel more distance in a time. Meaning it’s stretching it’s wavelength as it moves. Just like something moving away from us does. IIRC it’s because of observations that everything is constantly moving further from us, the further out you go, the faster it’s moving away.
But everything is moving from everything, including itself.
I do apologize if I’m a little muddy, I did my physics degree about a decade ago.
Edit as for why gravitational waves travel at the same as E&M waves is because “information” is what travels at the speed of light. For an electro magnetic wave that’s disturbances in E&M. For gravity that’s ripples in the fabric of space-time. For quantum there’s experiments showing that entangled particles will collapse together, if sperated by distance, the lag time is also the speed of light.
EDIT 2:
The only thing faster than the speed of light, is actually the expansion of the universe beyond a certain distance. Don’t remember what it is. But because distance istself is expanding, that’s proportional to distance. So the expansion rate is actually faster than the speed of light far enough out. But no SINGLE point is expanding faster than the speed of light.
If there’s no such thing as absolute distance, then how can you say that a metre bar (and the metre) is larger than it used to be?
If distance is relative, and matter isn’t expanding relative to anything else, then matter isn’t expanding.
We ultimately define distance in terms of c, and the fundamental forces agree with this. We do not observe atoms expanding, but we do observe the space between galaxies expanding. Presumably the space we occupy is also expanding, but it’s such a small effect as to be irrelevant.
Back to my original question, is the boundary between irrelevantly small and detectable above or below the galactic scale?