Thanks to light traveling at a fixed speed, we can compare points across time in the past with today as a reference. We just look at objects at the distance we want to observe.
We observed pulsars 12B light years away. They pulsed at a frequency significantly less than what we see from equivalent pulsars today. Implication is that time passed more slowly at that time in the universe.
The frequency of a pulsar's rotation depends on factors that existed before the pulsar formed. Is it so far fetched to imagine that the universe was indeed a very different place in the distant past, and thus affected celestial bodies differently than we observe today?
Instead of assuming that "everything must always be the same", would it not be easier to assume that sometimes things are just wildly different, even when they are of the same type?
Someone correct me if I'm mistaken but I don't think the implication is that time passed more slowly in some kind of absolute sense but that due to time-dilation effects we observe these rapidly receding quasars in slower time. And that if they in turn looked back at us, they would also see our portion of the universe in slower time. Of course whenever you look at anything you are looking at its past, so the effect is that the distant past everywhere appears to be moving slower.
But imagine the following: That 12 billion years ago some scientist built a briefcase-sized machine with a laser array with trillions of mirrors in a complex pattern. The laser is inside the machine and fires a regular one-second pattern into the bank of mirrors. From there the light just bounces around and around in the machine until it emerges out of an aperture. Because there are so many mirrors constructed in a complex pathway, it ends up taking 12 billion years for the light to emerge from the device. We come across the briefcase sitting in one of the craters on the Moon's south pole just as the pattern of light is emerging for the first time. (Let's pretend that whoever built the device included tech that would prevent the signal from attenuating.)
The question is, would the pattern still be at a one-second interval, or will it be slowed down? If I'm understanding this news item correctly, the pattern would be still at the original speed because it will not have experienced time-dilation effects relative to us on Earth like we see in distant quasars.
Implication is that time passed more slowly at that time in the universe.
Or that light travelled more slowly at that time in the universe. I don't think we have conclusively proven c to be a constant, right? Or is this a case of "c and t are so inextricably linked, it doesn't matter in practice which one changes, the result is effectively the same"?
> I don't think we have conclusively proven c to be a constant, right?
We obviously can't directly test what the speed of light was 1.5 billion years after the Big Bang. But we can test for changes in the fine structure constant back then, which would have to have been different back then if the speed of light were different. No such changes have been found.
I’m going to assume the credentialed astrophysicists who came to this conclusion probably have a good reason why they didn’t go with that interpretation of things.
Those are quasars (supermassive black holes), not pulsars (neutron stars).
They are not pulsing, they have variations.
Anyway, meter and second are defined as fraction of c, which ruins any discussion about variability of time or distance, because we are talking about c instead.
However, when we are talking about variable time, we need to talk about variable size too. If distant quasar was 5x slower, then it must be 5x larger.
