Yes. I am sure the paper makes adjustments, error corrections. They're good scientists. But I'm a layperson. So, I guess the problems are headlines. Because the headline didn't say confirm, but it states positively Time ran slowly
Outside of a dog, a cigar is a mans best friend. Inside of a dog, it's too dark to see.
Inside of a slowly running time period, a second is still a second, surely? So I ask myself how inside the universe, we can make assertions about the relative speed a second "is" but remain inside the same system. The implications some other attribute of observed reality can remain unchanged, and confirm the "duration" of a second was different then, to now, based on observations made solely within this universe.. I'm struggling.
but redshift here would be the key to making this determination.. I don't have access to the paper and it would probably be beyond me, but presumably you can make observations in redshifted light from quasars of different ages (or distances from the centre of the universe) and because we're fairly sure the properties of light haven't changed since the universe started, we use these subtle differences in redshifts like a sort of "cosmological GPS" and figure out that time must've been slower in the past
So I don't think this is an answer, certainly not THE answer, but I worry that aspects of the early universe like the local density of matter or electric fields were radically different to what we have now. If you imagine a beacon of light which is a signal from time "back then" which has to pass through both the early states of the universe with different densities of things between then and now, and us and them, AND has to be observed, I can think of ways both matter and energy could interfere with that signal differently across time. Consequently, the amount of red shift we see in modern times for more modern (ie closer) things reflects more modern states of the universe. As a correction factor, we'd be applying what we know, to what we infer, about the density in those times.
This is why I express skepticism: It's very hard to believe there are no confounding factors in the states of being then, compared to now, which might lie inside the error/noise thresholds of their calculations.
"it had to be time was different then" feels like "because I want it to" against all the sources of noise and conjecture, between then and now.
I hasten to add I am not an astrophysicist. So, I can be put firmly back in my box and told to accept good science says otherwise.
I would say perhaps the key difference here is we're talking about cosmological scale observations. Yes, a few quasars might've had to pass through some gas clouds or an asteroid belt or space dust etc. but at the scale we're talking about, that's probably not going to skew the numbers too much. There's 190 quasars being measured here. Presumably more observations can be made over time and with other quasars involved but I don't think these scientists need more data to be confident in what they're seeing.
If you think about a pebble getting in the way of old faithful, it's not going to make much difference if you're measuring how much water sprays out over a hundred years. Now you have 190 old faithfuls and they're all spraying out water in pretty much the same way, you don't really need to account for that pebble too much.
The general theory of relativity predicts that time would run slower, and if that was the case these ancient quasars would demonstrate certain properties when looked at by our telescopes. We then looked at ancient quasars, and the readings we got matched the predictions, with some amount of error.
This can then be used as another piece of experimental data supporting the general theory of relativity, even though you are right that these readings could be achieved through some other bizarre set of circumstances.
Someone usually posts up a preprint in discussions where the original link is a summary put out by one of the authors' institutions' public relations department and published unchanged or made even worse by some aggregator site's editing.
You can also install the Unpaywall extension which gives you a one-click button to (usually preprints of) a large proportion of freshly published papers (it works on more than half of astrophysics-related papers). http://unpaywall.org/ is one of the best things on the Internet.
> it would probably be beyond me
That's OK, it's also clearly totally beyond the author of the article reproduced at "advancedsciencenews".
You are correct to be puzzled about the lack of "redshift" appearing in the article; "high-redshift" is literally the eighth word in the title at Nature, and "redshift-dependent time dilation" appears in the first sentence of the abstract.
The first sentence of the Introduction (in preprint) reads, "A fundamental consequence of the relativistic picture of expanding space is cosmological time dilation, where events in the distant universe appear to move slowly compared to those in the local cosmos." Emphasis mine.
That's correct and totally conventional.
The first sentence of the "advancedsciencenews" article reads, "Scientists have confirmed that just 1.5 billion years after the Big Bang, time ran five times slower than it does today, 13.8 billion years later". I count several errors there, and struggle to see how a mere broken-telephone effect arrived at that wording.
1.5 billion years after the big bang, atomic electron transitions (like the n = 2 orbital to n = 1 ground state transition in atomic hydrogen) happened at the same ~nanosecond speed as 13.8 billion years after the big bang, emitting the same frequency photon (2.47 PHz) at both times. That transition speed and photon-frequency-at-emission each forms a sort of a local clock (or really frequency standard) which has travelled along from well before 1.5 billion years, through that 1.5 billion year mark, to the current age of the universe. We can test them tomorrow. We can test them next week. We can test them on the Moon or in more distant spacecraft. The ~nanoseconds transition and more precisely the emitted-photon frequency are always and everywhere the same when measuring locally, i.e. very near the emission and not moving quickly with respect to it.
General relativity tells us that, when there is significant gravitation or expansion of space, when we look at distant clocks (or really frequency standards) they appear to tick at different rates than clocks local to us. In particular, clocks in the distant past of an expanding universe appear to tick slower than clocks in the less distant past (and those tick slower than clocks here-and-now).
(Special relativity tells us that when we look at clocks that are in motion relative to a clock we have locally, the "moving" clock appears to tick slower.)
Consequently, the photon of an n=2 -> n=1 atomic hydrogen electron transition in the early universe will in the present universe have a frequency lower than 2.47 PHz. If we get to watch a transition happen (we can't, they're too small to see at great distances, but we can see the speed reflected in the bulk behaviour of atomic hydrogen gas lit by bright sources like ... quasars!) we'd see it happening slower. And from this we have the first line of the actual paper.
Additionally, hopefully shedding further light, we could drop in someone who is half way between 1.5 billion years and the present age of the universe, and locally they'd measure the same local ~nanosecond transition and the same 2.47 PHz photon frequency. Looking at the same 1.5 billion year universe source, the intermediate observer will also see a redshifted photon-frequency and a slower transition, but not as slow as we see even more billions of years later. In general, observers of the same source who are ever closer in time to that source will see a photon frequency and atomic electron transition speed ever closer to what they measure locally; whereas later observers will see an ever-greater difference (the later the observer the redder (slower transition, lower frequency) the ultimate observation).
The "appear" in the Nature article's first sentence deserves my italicization. It's important. And it seems to have not been noticed by the author of the advancedsciencenews summary. And it's clearly confused many people here. Hopefully with this comment I can unconfuse at least one person, at least a little.
Finally, the paper is about showing that variable quasars have an intrinsic set of luminosity-variation statistics, and intrinsic means that those statistics are local to the quasar. We should then see those statistics change when redshift changes. And that's what the authors show: the "intrinsic brightness-change-rate statistics" appear to generate slower brighness-variations for quasars that are at higher redshifts (measured by other means including the redshifting of absorption and emission spectral lines caused by the quasar's light passing through atomic hydrogen for example, and including the apparent area on the sky and brightness of the quasar's host galaxy).
Also in terms of a second being a second, yes, presumably if you took a pocket watch back to the beginning of the universe, it would not operate observably slower.
Imagine you had an inter-dimensional being that could traverse spacetime at will. They have 2 stopwatches, one is in their left hand at the center of the universe 12bn years ago, the other is in their right hand at the edge of the universe today.
If they started both stopwatches at the same time, the one in their left hand would take longer to reach 5 seconds than the one in their right hand.
Outside of a dog, a cigar is a mans best friend. Inside of a dog, it's too dark to see.
Inside of a slowly running time period, a second is still a second, surely? So I ask myself how inside the universe, we can make assertions about the relative speed a second "is" but remain inside the same system. The implications some other attribute of observed reality can remain unchanged, and confirm the "duration" of a second was different then, to now, based on observations made solely within this universe.. I'm struggling.