(Jul 9, 2024 03:25 PM)Zinjanthropos Wrote: I couldn't run the video, so did time run slower in the past because objects were much closed to one another (gravity related)?
Again, I can't find any recent paper connected to the "University of Queensland" that Sabine is referring to, but with respect to the one from last year (that seems similar)...
It primarily stems from the expansion of the universe (over time) subjecting light or EM-frequency based information to stretching. Somewhat contrary to the in-depth the Big Think account of it below, most of the news accounts actually seemed to state that our observations of the early universe would merely appear to be slower from our perspective, but not to the contents themselves back then. Just as that kind of relationship applies to
time dilation in general.
https://www.eurekalert.org/news-releases/994149
“If you were there, in this infant universe, one second would seem like one second – but from our position, more than 12 billion years into the future, that early time appears to drag.”
“This expansion of space means that our observations of the early universe should appear to be much slower than time flows today.
“In this paper, we have established that back to about a billion years after the Big Bang.”
Previously, astronomers have confirmed this slow-motion universe back to about half the age of the universe using supernovae – massive exploding stars – as ‘standard clocks’. But while supernovae are exceedingly bright, they are difficult to observe at the immense distances needed to peer into the early universe.
By observing quasars, this time horizon has been rolled back to just a tenth the age of the universe, confirming that the universe appears to speed up as it ages.
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Did time run slower in the early Universe?
https://bigthink.com/starts-with-a-bang/...-universe/
EXCERPTS: while everyone experiences the same laws of physics for themselves, they may see lengths as “contracted” or time as “dilated” for other observers, dependent on the curvature and evolution of spacetime and the relative motions of the observer and the observed.
[...] Whereas the source that emitted that light would have seen, say, 600,000,000,000,000 (six hundred trillion) wavelengths of that light pass them by with each second that passed (for light of a wavelength of 500 nanometers), the person observing that light will now only see half that number (three hundred trillion) wavelengths pass them by with each second that passes. Yes, the light now has a longer wavelength (of 1000 nanometers), but it also takes two seconds for the same information that was emitted over the timespan of one second to arrive at the observer.
In other words, the expanding Universe doesn’t just cause a cosmological redshift and a “stretching” of the emitted signal in terms of wavelengths, but it also causes a cosmological time dilation: a “stretching” of the emitted signal in time. This means, when we’re looking at objects that are very far away, we’re not observing them in “real-time” according to how they experienced it, but rather in slow-motion owing to this cosmological time dilation. The formula is very simple: the same “factor” that your signals get redshifted by is the “factor” by which your signals appear slowed-down when you view them.
It’s not that clocks were running slower in the early Universe; that’s not true at all. What’s true, instead, is that the expanding Universe makes the signal that we observe appear “stretched out” in time, and that applies to all of the signals we see from the distant Universe.
Unfortunately, a lot of people reading the stories written about this study have taken away entirely the wrong message: they now (erroneously) believe that time ran slower than it does today in the early Universe. No such thing is true! What happens is that time runs (and ran) at the same rate at all epochs throughout the Universe’s history, but that as the Universe expands, any signal that gets created gets “stretched out.” That “stretching out” occurs not only in terms of wavelength and (kinetic) energy, but also in time as well.
Time dilation has now been shown to apply in three separate instances. That’s it; it’s time dilation that’s stretching out the signals from distant quasars, nothing more. But time itself always passes at the same rate for an observer anywhere in the Universe: then, now, and forever more.
[...] Since we’ve confirmed that our Universe is expanding, that means that light gets redshifted, or shifted to longer wavelengths and lower energies, as the Universe expands. Furthermore, the greater the amount the Universe has cumulatively expanded over the interval where that light has been propagating through the Universe from the emitter to the observer, the greater the magnitude of the redshift observed.
This doesn’t merely apply to light, either. A gravitational wave that’s emitted by any source, from merging black holes to planets orbiting stars to any masses that move in the vicinity of space that’s curved by another mass, will also be redshifted and stretched to longer wavelengths as the Universe expands.
Massive particles, as well, whether charged or neutral, will lose kinetic energy as the Universe expands. You can recover identical predictions for how much energy they use either by treating the expansion as affecting the particle’s relative velocity or by considering the dual wave/particle nature of the particle in motion and noting that its wavelength, too, gets redshifted by the expanding Universe.
Regardless of how you look at it, the wavelength of any wave that propagates through the expanding Universe gets stretched as the fabric of space also stretches, and the more the Universe expands while these waves propagate, the greater the magnitude of this effect.