Supernova Slowdowns Confirm Einstein's Predictions of Time Dilation (scientificamerican.com) 39
Jonathan O'Callaghan reports via Scientific American: Despite more than a century of efforts to show otherwise, it seems Albert Einstein can still do no wrong. Or at least that's the case for his special theory of relativity, which predicts that time ticks slower for objects moving at extremely high speeds. Called time dilation, this effect grows in intensity the closer to the speed of light that something travels, but it is strangely subjective: a passenger on an accelerating starship would experience time passing normally, but external observers would see the starship moving ever slower as its speed approached that of light. As counterintuitive as this effect may be, it has been checked and confirmed in the motions of everything from Earth-orbiting satellites far-distant galaxies. Now a group of scientists have taken such tests one step further by observing more than 1,500 supernovae across the universe to reveal time dilation's effects on a staggering cosmic scale. The researchers' findings, once again, reach an all-too-familiar conclusion. "Einstein is right one more time," says Geraint Lewis of the University of Sydney, a co-author of the study.
In the paper, posted earlier this month on the preprint server arXiv.org, Ryan White of the University of Queensland in Australia and his colleagues used data from the Dark Energy Survey (DES) to investigate time dilation. For the past decade, researchers involved with DES had used the Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile to study particular exploding stars called Type 1a supernovae across billions of years of cosmic history. [...] Type 1a supernovae are keystone cosmic explosions caused when a white dwarf -- the slowly cooling corpse of a midsized star -- siphons so much material from a companion that it ignites a thermonuclear reaction and explodes. This explosion occurs once the growing white dwarf reaches about 1.44 times the mass of our sun, a threshold known as the Chandrasekhar limit. This physical baseline imbues all Type 1a supernovae with a fairly consistent brightness, making them useful cosmic beacons for gauging intergalactic distances. "They should all be essentially the same kind of event no matter where you look in the universe," White says. "They all come from exploding white dwarf stars, which happens at almost exactly the same mass no matter where they are."
The steadfastness of these supernovae across the entire observable universe is what makes them potent probes of time dilation -- nothing else, in principle, should so radically and precisely slow their apparent progression in lockstep with ever-greater distances. Using the dataset of 1,504 supernovae from DES, White's paper shows with astonishing accuracy that this correlation holds true out to a redshift of 1.2, a time when the universe was about five billion years old. "This is the most precise measurement" of cosmological time dilation yet, White says, up to seven times more precise than previous measurements of cosmological time dilation that used fewer supernovae. [...] This particular supernova-focused facet of the Dark Energy Survey has concluded, so until a new dataset is taken, White's measurement of cosmological time dilation is unlikely to be beaten. "It's a pretty definitive measurement," says [Tamara Davis of the University of Queensland, a co-author of the paper]. "You don't really need to do any better." Jonathan O'Callaghan is an award-winning freelance journalist covering astronomy, astrophysics, commercial spaceflight and space exploration.
In the paper, posted earlier this month on the preprint server arXiv.org, Ryan White of the University of Queensland in Australia and his colleagues used data from the Dark Energy Survey (DES) to investigate time dilation. For the past decade, researchers involved with DES had used the Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile to study particular exploding stars called Type 1a supernovae across billions of years of cosmic history. [...] Type 1a supernovae are keystone cosmic explosions caused when a white dwarf -- the slowly cooling corpse of a midsized star -- siphons so much material from a companion that it ignites a thermonuclear reaction and explodes. This explosion occurs once the growing white dwarf reaches about 1.44 times the mass of our sun, a threshold known as the Chandrasekhar limit. This physical baseline imbues all Type 1a supernovae with a fairly consistent brightness, making them useful cosmic beacons for gauging intergalactic distances. "They should all be essentially the same kind of event no matter where you look in the universe," White says. "They all come from exploding white dwarf stars, which happens at almost exactly the same mass no matter where they are."
The steadfastness of these supernovae across the entire observable universe is what makes them potent probes of time dilation -- nothing else, in principle, should so radically and precisely slow their apparent progression in lockstep with ever-greater distances. Using the dataset of 1,504 supernovae from DES, White's paper shows with astonishing accuracy that this correlation holds true out to a redshift of 1.2, a time when the universe was about five billion years old. "This is the most precise measurement" of cosmological time dilation yet, White says, up to seven times more precise than previous measurements of cosmological time dilation that used fewer supernovae. [...] This particular supernova-focused facet of the Dark Energy Survey has concluded, so until a new dataset is taken, White's measurement of cosmological time dilation is unlikely to be beaten. "It's a pretty definitive measurement," says [Tamara Davis of the University of Queensland, a co-author of the paper]. "You don't really need to do any better." Jonathan O'Callaghan is an award-winning freelance journalist covering astronomy, astrophysics, commercial spaceflight and space exploration.
Is he right one more time? (Score:4, Interesting)
Or is the same theory proven to still hold.
Re: Is he right one more time? (Score:2)
Just another day in the Universe, as if there would be something odd in its behavior.
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IIUC, it's the same prediction being tested on another kind of object. I.e., no surprise, but nice confirmation.
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Kinda thinking at this point we dont *really* need to "prove" einstein anymore. Its a done deal. The old boy was right.
Still , its always useful to examine how the theory translates into reality, its always the subtlties that turn up the new theories.
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You'd think that wouldn't you. But we keep being endless repeats and variations of the EM dive which violates relativity, not to mention everything else. On the other hand I don't think the perennially hopeful would be dissuaded by relativity being right yet again.
Bad wording in article (Score:5, Informative)
No: external observers see the starship moving ever faster as its speed approached the speed of light (got faster). What the author meant to say was: if external observers could see inside the ship, they'd see the crew moving ever slower.
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What the author meant to say was...
It seems more likely that he said what he meant, he just doesn't understand the subject. Especially when this is being phrased as a confirmation of Special Relativity, which has already been confirmed numerous times. So many times that if they found a different result it would point to an error in their experiment! Experiment? Well, analysis.
Cosmological time dilation [Re:Bad wording ini...] (Score:2)
It seems more likely that he said what he meant, he just doesn't understand the subject. Especially when this is being phrased as a confirmation of Special Relativity
In fact, this is a confirmation of cosmological time dilation, which is an effect of special relativity only if you interpret cosmological redshift as velocity (and, to be fair, this is right there in the title of the actual paper: "The Dark Energy Survey Supernova Program: Slow supernovae show cosmological time dilation out to z ~ 1".)
Since cosmological redshift is simply a measurement of the vibration period of light waves being slowed, it's not really possible for the period of supernova light decay to n
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In case 1) the external observer measures a slowdown in the roundtrip time of the reflected light signals. But the proper time in the spaceship is ticking more slowly, so the crew receives the periodic light signals at an ever faster rate. The reflected light from
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No, no, no. if a spaceship is accelerating and approaching the speed of light; and if, on that ship, Albert Einstein, Isaac Newton, Stephen Hawking, and Commander Data are playing poker at a steady pace - from whose Earth-based bank account are the withdrawals getting less and less frequent?
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Note that the spaceship is accelerating, it is not an inertial reference frame.
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What the author meant to say was: if external observers could see inside the ship, they'd see the crew moving ever slower.
If only the crew got slower, the ship would arrive before the crew, which seems like a big problem for everyone involved.
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"Our ships are so fast they can get you and your whole family to the next star before the ship even gets there! [1]
[1] mop not included in base ticket price, please talk to our sakes department about the mop and bucket upgrade option"
Re:Bad wording in article (Score:5, Informative)
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Yeah - I read it as one of those "edited to death" situations. I do this all the time - I write something, then read it, find I had too many passives, or too many negatives, go rewrite it a bit, it *reads* well...but now it is factually wrong because I left something out or left something in. (There are FB comments I've written that I've got like 12 edit history entries on because I keep seeing yet another mistake in the rewrite.)
Still, 'rush to publish' is still a thing and editors just aren't what they us
Article Completely Misses the Point (Score:5, Interesting)
What the author meant to say was:
Who knows what the author meant to say because they clearly have absolutely no idea about the physics they are describing. Apart from the glaring error you pointed out, the poinf of the SN survey is that it measures the rate of expansion of the universe and continues to show that the rate of expansion is accelerating. This result looks like it is a cross-check on that by measuring the expansion rate of the SN as a way to check that it matches the redshift because the accelerating expansion is such a surprising result given that we need Dark Energy to drive it - something related to the cosmological constant that, ironically, Einstein included initially and then referred to as his biggest blunder since it was initially thought to be zero but, as we now know, is needed.
Instead of going on about a test of time dilation the article should be talking about the evidence of accelerating expansion and Dark Energy. Indeed, this is a pretty poor test of time dilation since it is comparing the dilation of the explosion to the redshift which itself is partly due to time dilation. So really it is confirming that redshift and time dilation occur together in a manner consistent with relativity since you have no way to directly measure the velocity of these distant SN relative to us independently of the time dilation effect you are supposedly testing.
For an article this bad to appear in a magazine ostensibly aimed at science is appalling. I don't know what this guy won his award for but if it was for science reporting they need to take it back.
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No, no, no. The cosmological constant was originally thought to be 1 (one). And it's a multiplying term, so if it were 0 (zero) it would have an extreme effect.
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This is strange. The Lambda *is* as you describe, but I (partially) remember an equation where the cosmological constant was denoted "C" (upper case) and was a multiplier. This must have been during the late 1960's or really early 1970's, but I don't think it was a recent publication at the time. (I think it dated back to Hubble.) Perhaps there''s more than one formulation.
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It's been so long I have to say "maybe". IIRC the equation was about 7 symbols long, including the equal sign. (But it's been 5-6 decades, and I was an undergrad...or possibly even in high school.) It was just a multiplicative constant slipped into a previously existing equation for the (??curvature of space??) to allow the universe to expand. I understood it to be "The Cosmological Constant".
OTOH, I sure can't validate my memories with a web search...it just doesn't seem to be there. So maybe your gue
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First, the special case of the special theory of relativity is that acceleration = 0. Acceleration is the realm of general relativity. Observers in free fall will be unable to distinguish from inertial observers, they see time passing normally. Observers in a non-gravitationally accelerated spaceship will be unable to distinguish from being "stationary" on the surface of a planet, they will see time moving slower proportional to the g force. If a ship is dropped into a black hole, ie accelerating toward the
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Special relativity works just fine in accelerated frames. This is a common misconception because most people never get past the "unaccelerated frames are equivalent... weird" part.
General relativity is about gravity, not acceleration.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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Yes, gravitational freefall is equivalent to an inertial frame of reference, as proven in general relativity. Freefall means gravity.
You can't distinguish between standing on a planet and being accelerated by a spaceship engine with a local experiment. You can't distinguish freefall from an inertial frame of reference.
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You can, pretty trivially, using something as simple as a pendulum. As I said in my other post, you're the victim of overzealous interpretation of the equivalence principle, i.e. fibbing to the layman rather than explaining what a limit is.
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As a bonus, the DES supernovae data offered scientists a new chance to study cosmological time dilation—that is, time dilation caused by the universe’s expansion.
The article is talking about the general theory of relativity.
And no, you can't use a pendulum to violate the principle of relativity.
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You can tell the difference between acceleration by an engine and sitting on a planet using a pendulum. It has nothing to do with relativity.
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Congratulations on your imminent Nobel Prize. Be sure to publish your result so it can be peer reviewed.
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Ah, you're not the first Slashdot physicist to nominate me for a Nobel. Unfortunately the actual Nobel committee consults with actual physicists, who invariably point out that both Galileo and Einstein beat me to it.
Seriously, you sound like you at least have some interest in general relativity. If so it's worth learning a bit more than the pop science sound bites.
This article, for instance, gives the (incorrect) pop sci version, then discusses how it's wrong and what the equivalence principle actually impl
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Ah, found it:
Ohanian and Ruffini, "Gravitation and Spacetime":
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Yes, that's why I said you could distinguish it if it was a non-local experiment.
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Cough. Anyway, now that you know that "local" actually means "does not exist in reality" we seem to agree.
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Sorry if it's terminology you're unfamiliar with, but it's the same stuff you quoted. Local as in, in one location only.
"Realizing that what matters are the size of the region, and the duration of our observations, we are led to a formulation in which the equivalence principle is not just a useful approximation, but exactly true: Within an infinitely small ("infinitesimal") spacetime region, one can always find a reference frame - an infinitely small elevator cabin, observed over an infinitely brief period
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Your second half is also a common misconception due to overzealous interpretation of the equivalence principle. It's pretty trivial to distinguish acceleration of something like a spaceship from acceleration in any actual gravitational field.
The equivalence principle is the assumption that inertial and gravitational mass are the same (i.e. equivalent) and is much older than Einstein. If you also assume Lorentz invariance from special relativity, that implies that acceleration by a gravitational field and ot
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Weird place to look for gaps in relativity. (Score:2)
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pfft.. wake me up when they prove negative mass... (Score:3)
We have proven time dilation, some time ago. Apollo era wristwatches went to the moon and back. Guess what? The time was different on the watch that went to the moon.