Time ran slower in the past, physicists / astronmers find (Sabine Hossenfelder)

#1
C C Offline
Video released today, but can't find anything similar but this press release from last year. But the paper is by researchers from the University of Sydney, rather than the University of Queensland.
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https://youtu.be/RuSbqFL6VcY

VIDEO EXCERPTS: Physicists from the University of Queensland in Australia have found evidence that time ran slower in the past. This may sound like they climbed into the attic and excavated a dial-up modem, but it’s actually to do with supernovae. Let’s have a look.

[...] But what does it mean that time ran slower in the past? If someone was alive back then, would they have noticed any difference?

No, they wouldn’t, because everything happened slower back then. So they wouldn’t have been able to tell. It’s just in comparison to today that we see a difference.

[...] There are two ways to look at this result. One is, Einstein was right again, how boring. The other is that this is  the reason why Einstein’s theory is so difficult to improve on. Because it has so much evidence speaking for it. Unless, of course, you believe the earth is flat. In which case I guess time dilation is just a hoax that physicists have invented to sound smart which really explains a lot doesn’t it...

Time ran slower in the past, physicists find

https://www.youtube-nocookie.com/embed/RuSbqFL6VcY
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#2
confused2 Offline
Hm. Time ran slower in the past?
This looks to me like something of a half a twin paradox thing .. did time actually run slower for the travelling twin?
Maybe a case of interpretation (or misinterpretation) .. anyone want to play paradoxical twins (again)?
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#3
Zinjanthropos Online
I couldn't run the video, so did time run slower in the past because objects were much closed to one another (gravity related)?
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#4
geordief Offline
(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)?

I think it is because the universe expanded and this causes light to be red shifted.

She says the intervals between the crests (or dips) in the light waves can be treated as the "ticks of a clock"

So ,that means there were  less ticks in the past.(meaning time ran slower compared to now-but the same for anyone actually living through it then.One second per second as it is often described)

This was apparently verified by looking at supernovae  events  and their aftermaths in the past 

Not that I fully understand it  but no,not to do with massive objects being closer together.

When videos don't work for me I search for them.on youtube directly and they are often there.
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#5
C C Offline
(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.
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