6 ms·

As a layman it always amazes me when reading such news that what we see now actually _happened there_ n years ago (in this case: 3.5 billions years ago). Not th

As a layman it always amazes me when reading such news that what we see now actually _happened there_ n years ago (in this case: 3.5 billions years ago). Not that it matters, but it is mind boggling nevertheless.

lanna 3y ago
We are always seeing the past. If you are talking to someone a foot away from you, you are seeing how they were a nanosecond ago.
- seanw444 3y ago
  Yes, but that is beyond human perception. A nanosecond is pretty much now. Several billion years is a whole time machine.
  - go_elmo 3y ago
    But still - it unveils the "present" to just as well be an illusion of human categorical thinking, an abstract concept, not more. It is super useful to have none the less, just interesting to know its fragility.
    - somenameforme 3y ago
      Should we ultimately be able to develop relativistic rockets, and it seems there is no inherent reason why we shouldn't, then everything is just going to be so unbelievably weird. Traveling on a rocket to friendly distant planet, except the planet you land on may be millions of years in the future from when it was first settled. Or imagine living on said planets and occasionally seeing relics thousands, millions, or even further back in history approaching for landing. Time, life, death, technology, and everything will be just so unimaginably alien. It will be basically impossible to have a normal linear view of time when it's violated constantly, even though your body itself will yet still almost certainly be insistent on linear time - and steadily marching towards its expiration date. Even evolution itself will be weird. Humans over millions of years will probably scarcely resemble ourselves today, yet you'll regularly have 'old' species humans regularly reintegrating with 'new' ones? Such a bizarre reality we live in, unless perhaps somehow the views we have today end up being as quaint as those of times past.
      - edgyquant 3y ago
        Such a species won’t be Homo sapiens anymore so this likely won’t be weird to them.
      - theideaofcoffee 3y ago
        Maybe it will be a quaint, and ultimately solved, problem in that time but if the present is any indication, I can’t imagine how old and new might interact. We already have enough problems with conflicts arising between people born in either side of an imaginary line. How will that work with humans born in different eons?
      - denton-scratch 3y ago
        > Should we ultimately be able to develop relativistic rockets Aren't all rockets relativistic? In the sense that "there's no inherent reason", I take it to mean "near to c", for some value of "near". that is, it's a "relative" term.
        somenameforme 3y ago
        Contrary to what many people think, the speed of light isn't like a speed limit. Imagine you're on a ship with near infinite fuel. And there's a button that each time you press will generate enough thrust to gain 1km/s of velocity. It's not like the 300,001st time you press that button (with the speed of light being around 300k km/s), it just won't work anymore somehow, nor will it require any more thrust than the 50th press required. No you'll keep accelerating, to no limit. What relativity does is change things in a way relative to who's observing. From your perspective distances would begin to physically contract, time everywhere else would begin to accelerate, and things would probably start looking a bit odd. But you could keep hitting that button to your heart's content, and continue going faster and faster. By contrast for a relatively at rest observer, looking at you, they would see your relativistic mass start to approach infinity as you approached the speed of light. And so they would see you slowing down (as accelerating an infinite mass object would be impossible), and the movement of time for you (relative to them) would begin to slow dramatically, hence why time for them (relative to you) seems to accelerate dramatically. The calculations for relativistic rockets are quite remarkable [1], because it's an exponential system. For instance, here are some times it'd take you to travel to various points in a typical relativistic rocket that continues to accelerate at 1g (you go half way to a target at 1g, and then half way in reverse): - Proxima Centauri - 4.3 light years away - 3.6 "real" years of travel - Vega - 27 light years away - 6.6 "real" years of travel - Center of our galaxy - 30,000 light years away - 20 "real" years of travel - Andromeda Galaxy - 2,000,000 light years away - 28 "real" years of travel With a relativistic rocket, if you wanted to see what the end of the universe looked like in a single human lifetime, you could. It's really really weird. So basically a relativistic rocket is more about creating a rocket that can just keep accelerating for years at a time, rather than reaching any specific speed. They're certainly similar in effect, but framing it in terms of years of acceleration makes it a pretty well defined problem. [1] - https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/...
  - lanna 3y ago
    We see the Moon as it was a second ago. We see the Sun 8 minutes ago.
- flandish 3y ago
  The only thing that travels faster than light is gossip.
isaacg 3y ago
This article is about two galaxies which we are seeing as they appeared 300-400 million years after the big bang (over 13 billion years ago). Those galaxies are magnified to the point where they are visible by another, much closer galaxy cluster, which is only 3.5 billion light years away.
- dfee 3y ago
  Two amazing things: 1. these photos have been traveling for 13.5 billion years, just to meet their fate smashing into the JWST. 2. how many photons must have been emitted, that a sphere 13.5 billion light years in radius can still resolve the image.
  - capitainenemo 3y ago
    Well, due to the massive gravitational lensing from the intermediate galaxy a few billion years away, I guess it's not actually a perfect 13½ billion light year sphere right... It's a fair chunk of the photons in the 10 billion light year sphere swept up and focused over a vast area and pointed in our direction. Still amazing to think about though.
  - floxy 3y ago
    The radius of the universe is closer to 46 billion light-years: https://en.wikipedia.org/wiki/Observable_universe https://en.wikipedia.org/wiki/Observable_universe
    - qup 3y ago
      The photons have emanated in a sphere from point of origin with a radius of 13.5 billion light years. The radius of the universe is irrelevant.
      - capitainenemo 3y ago
        Well, it's a good point no? If the universe is expanding as the photons propagate they are spread out into that larger sphere. So for the purposes of light gathering, a galaxy 13 billion years in the past has its photons spread over that much larger sphere into even greater invisibility. Although I guess in this case they were spread out into the larger sphere at the point of the expansion of the universe of a few billion years ago before being focused towards us - so. Some value significantly smaller than 46 but a lot larger than 10. Which makes it even more amazing to think about.
matt-attack 3y ago
But if information can only travel at the speed of light shouldn’t we consider the events being observed way out there as “now”? For all intents and purposes information couldn’t have gotten here any sooner so it might as well be “now”.
- edgyquant 3y ago
  No that doesn’t make sense
- cwillu 3y ago
  Yes, “surface of simultaneity”, but you have to keep in mind that it's inherently relative: your “now” at best only approximately corresponds to anyone elses, and is a weird cross-section of history and future for _most_ reference frames.

lanna 3y ago

We are always seeing the past. If you are talking to someone a foot away from you, you are seeing how they were a nanosecond ago.

seanw444 3y ago
Yes, but that is beyond human perception. A nanosecond is pretty much now. Several billion years is a whole time machine.
- go_elmo 3y ago
  But still - it unveils the "present" to just as well be an illusion of human categorical thinking, an abstract concept, not more. It is super useful to have none the less, just interesting to know its fragility.
  - somenameforme 3y ago
    Should we ultimately be able to develop relativistic rockets, and it seems there is no inherent reason why we shouldn't, then everything is just going to be so unbelievably weird. Traveling on a rocket to friendly distant planet, except the planet you land on may be millions of years in the future from when it was first settled. Or imagine living on said planets and occasionally seeing relics thousands, millions, or even further back in history approaching for landing. Time, life, death, technology, and everything will be just so unimaginably alien. It will be basically impossible to have a normal linear view of time when it's violated constantly, even though your body itself will yet still almost certainly be insistent on linear time - and steadily marching towards its expiration date. Even evolution itself will be weird. Humans over millions of years will probably scarcely resemble ourselves today, yet you'll regularly have 'old' species humans regularly reintegrating with 'new' ones? Such a bizarre reality we live in, unless perhaps somehow the views we have today end up being as quaint as those of times past.
    - edgyquant 3y ago
      Such a species won’t be Homo sapiens anymore so this likely won’t be weird to them.
    - theideaofcoffee 3y ago
      Maybe it will be a quaint, and ultimately solved, problem in that time but if the present is any indication, I can’t imagine how old and new might interact. We already have enough problems with conflicts arising between people born in either side of an imaginary line. How will that work with humans born in different eons?
    - denton-scratch 3y ago
      > Should we ultimately be able to develop relativistic rockets Aren't all rockets relativistic? In the sense that "there's no inherent reason", I take it to mean "near to c", for some value of "near". that is, it's a "relative" term.
      - somenameforme 3y ago
        Contrary to what many people think, the speed of light isn't like a speed limit. Imagine you're on a ship with near infinite fuel. And there's a button that each time you press will generate enough thrust to gain 1km/s of velocity. It's not like the 300,001st time you press that button (with the speed of light being around 300k km/s), it just won't work anymore somehow, nor will it require any more thrust than the 50th press required. No you'll keep accelerating, to no limit. What relativity does is change things in a way relative to who's observing. From your perspective distances would begin to physically contract, time everywhere else would begin to accelerate, and things would probably start looking a bit odd. But you could keep hitting that button to your heart's content, and continue going faster and faster. By contrast for a relatively at rest observer, looking at you, they would see your relativistic mass start to approach infinity as you approached the speed of light. And so they would see you slowing down (as accelerating an infinite mass object would be impossible), and the movement of time for you (relative to them) would begin to slow dramatically, hence why time for them (relative to you) seems to accelerate dramatically. The calculations for relativistic rockets are quite remarkable [1], because it's an exponential system. For instance, here are some times it'd take you to travel to various points in a typical relativistic rocket that continues to accelerate at 1g (you go half way to a target at 1g, and then half way in reverse): - Proxima Centauri - 4.3 light years away - 3.6 "real" years of travel - Vega - 27 light years away - 6.6 "real" years of travel - Center of our galaxy - 30,000 light years away - 20 "real" years of travel - Andromeda Galaxy - 2,000,000 light years away - 28 "real" years of travel With a relativistic rocket, if you wanted to see what the end of the universe looked like in a single human lifetime, you could. It's really really weird. So basically a relativistic rocket is more about creating a rocket that can just keep accelerating for years at a time, rather than reaching any specific speed. They're certainly similar in effect, but framing it in terms of years of acceleration makes it a pretty well defined problem. [1] - https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/...
- lanna 3y ago
  We see the Moon as it was a second ago. We see the Sun 8 minutes ago.
flandish 3y ago
The only thing that travels faster than light is gossip.

isaacg 3y ago

This article is about two galaxies which we are seeing as they appeared 300-400 million years after the big bang (over 13 billion years ago). Those galaxies are magnified to the point where they are visible by another, much closer galaxy cluster, which is only 3.5 billion light years away.

dfee 3y ago
Two amazing things: 1. these photos have been traveling for 13.5 billion years, just to meet their fate smashing into the JWST. 2. how many photons must have been emitted, that a sphere 13.5 billion light years in radius can still resolve the image.
- capitainenemo 3y ago
  Well, due to the massive gravitational lensing from the intermediate galaxy a few billion years away, I guess it's not actually a perfect 13½ billion light year sphere right... It's a fair chunk of the photons in the 10 billion light year sphere swept up and focused over a vast area and pointed in our direction. Still amazing to think about though.
- floxy 3y ago
  The radius of the universe is closer to 46 billion light-years: https://en.wikipedia.org/wiki/Observable_universe https://en.wikipedia.org/wiki/Observable_universe
  - qup 3y ago
    The photons have emanated in a sphere from point of origin with a radius of 13.5 billion light years. The radius of the universe is irrelevant.
    - capitainenemo 3y ago
      Well, it's a good point no? If the universe is expanding as the photons propagate they are spread out into that larger sphere. So for the purposes of light gathering, a galaxy 13 billion years in the past has its photons spread over that much larger sphere into even greater invisibility. Although I guess in this case they were spread out into the larger sphere at the point of the expansion of the universe of a few billion years ago before being focused towards us - so. Some value significantly smaller than 46 but a lot larger than 10. Which makes it even more amazing to think about.

matt-attack 3y ago

But if information can only travel at the speed of light shouldn’t we consider the events being observed way out there as “now”? For all intents and purposes information couldn’t have gotten here any sooner so it might as well be “now”.

edgyquant 3y ago
No that doesn’t make sense
cwillu 3y ago
Yes, “surface of simultaneity”, but you have to keep in mind that it's inherently relative: your “now” at best only approximately corresponds to anyone elses, and is a weird cross-section of history and future for _most_ reference frames.