5 ms·

How can one measure the speed of things through time relative to things in their past or future? Can't we only measure the speed of things through time relative

by tines 3y ago

How can one measure the speed of things through time relative to things in their past or future? Can't we only measure the speed of things through time relative to other things that coexist at the same time? I read the article but couldn't make sense of it.

foota 3y ago
I think they're looking at parts of the universe that are very old, and so they can watch it move more slowly.
yathaid 3y ago
> Lewis explained that the brightening and fading of quasar light, known as their variability is like the stock mark, unpredictable on the surface but with statistical properties that allow it to be modelled over time. This variability can be used like the ticking of a cosmic clock. It was this understanding and the complex quasar firework display from 190 of these feeding supermassive black holes that allowed the team to spot time dilation when the universe was just 1.5 billion years old, less than 10% of its current age.
- mattashii 3y ago
  > when the universe was just 1.5 billion years old, less than 10% of its current age. Which universe are they talking about? Most sources I know of cite 13.78 billion years for our universe, and the quoted 1.5 billion years is definitely over 10% of that.
colechristensen 3y ago
Think of looking at someone running across the street and then looking through a telescope at someone running far away. The person far away would be in the past because of whatever amount of distance light had to travel. The person far away would seem to be running in slow motion. Instead of whatever tiny fraction of a second your telescope would enable you to look into the past, the telescopes looking at whole-ass galaxies in the early universe that appear to be "running slower".
rstuart4133 3y ago
> Can't we only measure the speed of things through time relative to other things that coexist at the same time? They weren't using speed. They were watching how fast a clock ticked back then, the clock being a quasar. The article was light on the details, but the difficulty seemed to be that quasar's aren't reliable clocks, so they needed to develop a statistical model to measure the ticking accurately. Developing the model was actual science being reported on. It happened to agree with Einstein's predictions. But even if they were using speed, gravity doesn't slow down light. It redshift's it. So there is something you could compare your speed to back then. Finally, we are comparing how fast time ticks for us now versus how fast a quasar ticked back then. I don't know if the quasar it still around, but if it is it's probably a very different beast now. In any case we are comparing two things that don't exist at the same time. In fact, my guess is it's downright difficult compare yourself to something that exists at the same time, because the speed of light is finite. That means by the time you receive the measurement, whatever you've measured has moved on.
scandum 3y ago
My main take away from the article was that we, apparently, need a time traveler to confirm/disprove Einstein's theory.
ww520 3y ago
Based on the article and my guesses, here's how they measured time on the past. When we look at things far away from us, we're seeing their state in the past. Quasars that are 10 billion light years away took 10 billion years for their light to reach us, so right now we are seeing their images 10 billion years ago. Quasar is bright light powered by gas spiraling at a high velocity into a black hole. When things revolving around a black hole, the light given out varies. The light of the gas spinning behind the black hole is blocked and the light is shown again when the gas spinning on the side of the black hole facing us. When we're looking at it, it kind of blinks periodically in constant rate. The blinking rate can serve as clock ticks. The people of the paper figure out a way to compute the blinking rate of the quasars statistically. They look at hundreds of quasars at 12 billion light years away, i.e. looking at their state 12 billion years ago. Compute their blinking rate from twenty years of telescope observation. Compare that to the quasars close to us. They found that the far away quasars blink 5 times slower, i.e. they're blinking 5 times slower 12 billion years ago. The universe is about 13.7 billion years old, so the conclusion is that time ran slower at the early age. It actually fits the prediction from Einstein's general relativity.
pdonis 3y ago
What they are measuring is the apparent "speed" of processes back then. But that apparent speed is an effect of the redshift. It does not mean that clocks were actually running slower back then. The article's description is seriously misleading.

by tines 3y ago

foota 3y ago

I think they're looking at parts of the universe that are very old, and so they can watch it move more slowly.

yathaid 3y ago

> Lewis explained that the brightening and fading of quasar light, known as their variability is like the stock mark, unpredictable on the surface but with statistical properties that allow it to be modelled over time. This variability can be used like the ticking of a cosmic clock. It was this understanding and the complex quasar firework display from 190 of these feeding supermassive black holes that allowed the team to spot time dilation when the universe was just 1.5 billion years old, less than 10% of its current age.

mattashii 3y ago
> when the universe was just 1.5 billion years old, less than 10% of its current age. Which universe are they talking about? Most sources I know of cite 13.78 billion years for our universe, and the quoted 1.5 billion years is definitely over 10% of that.

colechristensen 3y ago

Think of looking at someone running across the street and then looking through a telescope at someone running far away. The person far away would be in the past because of whatever amount of distance light had to travel. The person far away would seem to be running in slow motion. Instead of whatever tiny fraction of a second your telescope would enable you to look into the past, the telescopes looking at whole-ass galaxies in the early universe that appear to be "running slower".

rstuart4133 3y ago

> Can't we only measure the speed of things through time relative to other things that coexist at the same time? They weren't using speed. They were watching how fast a clock ticked back then, the clock being a quasar. The article was light on the details, but the difficulty seemed to be that quasar's aren't reliable clocks, so they needed to develop a statistical model to measure the ticking accurately. Developing the model was actual science being reported on. It happened to agree with Einstein's predictions. But even if they were using speed, gravity doesn't slow down light. It redshift's it. So there is something you could compare your speed to back then. Finally, we are comparing how fast time ticks for us now versus how fast a quasar ticked back then. I don't know if the quasar it still around, but if it is it's probably a very different beast now. In any case we are comparing two things that don't exist at the same time. In fact, my guess is it's downright difficult compare yourself to something that exists at the same time, because the speed of light is finite. That means by the time you receive the measurement, whatever you've measured has moved on.

scandum 3y ago

My main take away from the article was that we, apparently, need a time traveler to confirm/disprove Einstein's theory.

ww520 3y ago

Based on the article and my guesses, here's how they measured time on the past. When we look at things far away from us, we're seeing their state in the past. Quasars that are 10 billion light years away took 10 billion years for their light to reach us, so right now we are seeing their images 10 billion years ago. Quasar is bright light powered by gas spiraling at a high velocity into a black hole. When things revolving around a black hole, the light given out varies. The light of the gas spinning behind the black hole is blocked and the light is shown again when the gas spinning on the side of the black hole facing us. When we're looking at it, it kind of blinks periodically in constant rate. The blinking rate can serve as clock ticks. The people of the paper figure out a way to compute the blinking rate of the quasars statistically. They look at hundreds of quasars at 12 billion light years away, i.e. looking at their state 12 billion years ago. Compute their blinking rate from twenty years of telescope observation. Compare that to the quasars close to us. They found that the far away quasars blink 5 times slower, i.e. they're blinking 5 times slower 12 billion years ago. The universe is about 13.7 billion years old, so the conclusion is that time ran slower at the early age. It actually fits the prediction from Einstein's general relativity.

pdonis 3y ago

What they are measuring is the apparent "speed" of processes back then. But that apparent speed is an effect of the redshift. It does not mean that clocks were actually running slower back then. The article's description is seriously misleading.