8 ms·

distant means younger means different composition (less heavy elements), dunno if that's the deal here though

by disconcision 4y ago

mrits 4y ago
Unless we are the center of the universe I don't see how distant could mean younger
- Cthulhu_ 4y ago
  That's an interesting one to think about; every galaxy moves away from every one, so (if I got this right) from every other galaxy's point of view, all the other galaxies are younger... or older, either / or I don't know anymore.
  - ianai 4y ago
    Light and thus causality and information travel at a constant speed of "c." As far as we know, nothing can travel faster than "c" - other than the universe itself as in during the inflationary epoch. So the further out any observer would look the longer that light would have had to travel relative to that observer. Seeing something 3 billion light years away would mean the light took 3 billion years to arrive at the observer.
    - Maursault 4y ago
      > As far as we know, nothing can travel faster than "c" What Relativity forbids is anything traveling as fast as c, as the increase in mass as c is approached would require infinite energy to reach. Relativity says absolutely nothing about faster than c, i.e. it does not forbid things such as the theoretical tachyon.
  - cmehdy 4y ago
    It's more like every point of view looks at the past. Which is also true if you look at your screen right now, it's just that you're looking at your screen some nanoseconds ago.
- ncallaway 4y ago
  The further away it is, the more time light has spent traveling to us. So, more distant means we are viewing events that happened further in the past. We are (almost certainly) not at the center of the universe, but we are, by definition, at the center of our observable universe.
- Jenk 4y ago
  The light took far longer to reach us, thus what we are _observing_ is from a much younger (than it really, currently, is) star.
- Archelaos 4y ago
  You are the oldest thing in the universe you can observe. Even the person next to you, as you observe her or him, is younger, because the speed of light is finite. In this respect, you are the centre of your universe. But objectively speaking, there is no centre.
  - p1esk 4y ago
    This doesn’t make any sense
    - deleted 4y ago
      [deleted]
    - deleted 4y ago
      [deleted]
    - tromp 4y ago
      When you see someone standing 3m away from you, the light took 10 nanoseconds to reach your eye, so you see them as they were a very short time ago. Of course, they're only younger when measuring their age not from their birth but from the big bang.
    - jpollock 4y ago
      I find it useful to think of photons as vector clocks: https://en.wikipedia.org/wiki/Vector_clock https://en.wikipedia.org/wiki/Vector_clock Take a photon starting from your chest and give it t1. * Assume that the speed of light is symmetrical. * When the photon hits the next person's eyes, it is t1 + distance/speed of light. Meaning, the photon is "from the past". Since all photons arriving are from the past, the photons travelling the shortest distance are the newest (representing the largest timestamp). So, the thing with the largest observable timestamp is yourself.
      - p1esk 4y ago
        We are not talking about the age of photons. We are talking about the age of the thing that emits/reflects photons. The confusion arose because the OP said "you are the oldest thing in the universe you can observe". They should have said "you are the most recent thing in the universe you can observe".
- BurningFrog 4y ago
  The universe has no center. All places are equally old. So a galaxy a billion light years away is as old as ours. But we see it as it was 1 billion years ago.
  - samstave 4y ago
    I’ve always had trouble understanding this; if everything is the same age, how did they get billions of light years away from the Big Bang? How do we know where the Big Bang occurred? Unles it means that our galaxy is on the spherical plane(?) directly projected out in all directions from the bang, and it’s the diameter of this sphere that is billions across?
    - x3n0ph3n3 4y ago
      The big bang occurred _everywhere_.
      - JumpCrisscross 4y ago
        To add to this: we are used to seeing explosions propagating across space and time. The Big Bang was an explosion of spacetime.
        hdjjhhvvhga 4y ago
        Why did it happen?
        sdmike1 4y ago
        Good question, my understanding is that we frankly just don't know, it may be one of those things that we can't know, but that is getting awfully close to the realm of philosophy
        JumpCrisscross 4y ago
        > it may be one of those things that we can't know This is true for anything we don’t know. For the Big Bang, we know the intermediate problem: black holes. Gravity and quantum mechanics interacting at the same scale. The singularities there are accessible in a way the singularity of the Big Bang is not.

distant means younger means different composition (less heavy elements), dunno if that's the deal here though

mrits 4y ago

Unless we are the center of the universe I don't see how distant could mean younger

Cthulhu_ 4y ago
That's an interesting one to think about; every galaxy moves away from every one, so (if I got this right) from every other galaxy's point of view, all the other galaxies are younger... or older, either / or I don't know anymore.
- ianai 4y ago
  Light and thus causality and information travel at a constant speed of "c." As far as we know, nothing can travel faster than "c" - other than the universe itself as in during the inflationary epoch. So the further out any observer would look the longer that light would have had to travel relative to that observer. Seeing something 3 billion light years away would mean the light took 3 billion years to arrive at the observer.
  - Maursault 4y ago
    > As far as we know, nothing can travel faster than "c" What Relativity forbids is anything traveling as fast as c, as the increase in mass as c is approached would require infinite energy to reach. Relativity says absolutely nothing about faster than c, i.e. it does not forbid things such as the theoretical tachyon.
- cmehdy 4y ago
  It's more like every point of view looks at the past. Which is also true if you look at your screen right now, it's just that you're looking at your screen some nanoseconds ago.
ncallaway 4y ago
The further away it is, the more time light has spent traveling to us. So, more distant means we are viewing events that happened further in the past. We are (almost certainly) not at the center of the universe, but we are, by definition, at the center of our observable universe.
Jenk 4y ago
The light took far longer to reach us, thus what we are _observing_ is from a much younger (than it really, currently, is) star.
Archelaos 4y ago
You are the oldest thing in the universe you can observe. Even the person next to you, as you observe her or him, is younger, because the speed of light is finite. In this respect, you are the centre of your universe. But objectively speaking, there is no centre.
- p1esk 4y ago
  This doesn’t make any sense
  - deleted 4y ago
    [deleted]
  - deleted 4y ago
    [deleted]
  - tromp 4y ago
    When you see someone standing 3m away from you, the light took 10 nanoseconds to reach your eye, so you see them as they were a very short time ago. Of course, they're only younger when measuring their age not from their birth but from the big bang.
  - jpollock 4y ago
    I find it useful to think of photons as vector clocks: https://en.wikipedia.org/wiki/Vector_clock https://en.wikipedia.org/wiki/Vector_clock Take a photon starting from your chest and give it t1. * Assume that the speed of light is symmetrical. * When the photon hits the next person's eyes, it is t1 + distance/speed of light. Meaning, the photon is "from the past". Since all photons arriving are from the past, the photons travelling the shortest distance are the newest (representing the largest timestamp). So, the thing with the largest observable timestamp is yourself.
    - p1esk 4y ago
      We are not talking about the age of photons. We are talking about the age of the thing that emits/reflects photons. The confusion arose because the OP said "you are the oldest thing in the universe you can observe". They should have said "you are the most recent thing in the universe you can observe".
BurningFrog 4y ago
The universe has no center. All places are equally old. So a galaxy a billion light years away is as old as ours. But we see it as it was 1 billion years ago.
- samstave 4y ago
  I’ve always had trouble understanding this; if everything is the same age, how did they get billions of light years away from the Big Bang? How do we know where the Big Bang occurred? Unles it means that our galaxy is on the spherical plane(?) directly projected out in all directions from the bang, and it’s the diameter of this sphere that is billions across?
  - x3n0ph3n3 4y ago
    The big bang occurred _everywhere_.
    - JumpCrisscross 4y ago
      To add to this: we are used to seeing explosions propagating across space and time. The Big Bang was an explosion of spacetime.
      - hdjjhhvvhga 4y ago
        Why did it happen?
        sdmike1 4y ago
        Good question, my understanding is that we frankly just don't know, it may be one of those things that we can't know, but that is getting awfully close to the realm of philosophy
        JumpCrisscross 4y ago
        > it may be one of those things that we can't know This is true for anything we don’t know. For the Big Bang, we know the intermediate problem: black holes. Gravity and quantum mechanics interacting at the same scale. The singularities there are accessible in a way the singularity of the Big Bang is not.