5 ms·

it only has physical significance from our perspective.

lisper 8y ago
Well, yeah, but our perspective is the only one that can possibly matter for us. There may be unicorns and leprechauns out beyond our light cone for all we know, but what possible reason would there be to care?
- empath75 8y ago
  What happens on the far side of the moon doesn't matter for us, either, but we still looked.
  - lisper 8y ago
    > What happens on the far side of the moon doesn't matter for us, either, How do you know? Maybe the far side of the moon is chock-full of exploitable resources. You can't know until you look. > but we still looked. Sure, because we could. We cannot look beyond our light cone.
    - Retric 8y ago
      For now we can just by waiting. With every second we see just a little further. Tomorrow we might look out at the stars and see the tips of giant teeth. But, probably not.
      - lisper 8y ago
        You don't quite understand the concept of a light cone. Yes, we get new data all the time, and the extent of our horizon is growing. But it is always finite. You cannot look backwards past the big bang singularity, and you cannot look forwards beyond "now" for any value of "now".
        ieo838jdkd 8y ago
        We can’t But 200 years ago we “didn’t need” relativity and then we did Asking questions and wondering about the things we don’t know is how we now know about many valuable things that, in the past, didn’t appear to be valuable
        nbulka 8y ago
        You may want to temper your claims with "based on the currently accepted Standard Model" or "with high probability." Because paradigm shifts occur.
        lisper 8y ago
        See my OP: https://news.ycombinator.com/item?id=18094991 https://news.ycombinator.com/item?id=18094991 "Barring some major unforeseen revolution in our understanding of physics..."
        Retric 8y ago
        No, you fail to understand a light cones end at finite points. If I travel 1 light year, then I observe a different light cone and it takes 1 year for somone that stayed behind to receive information from me. This effectively means you can see something before the light cone at your current location would observe it. If you consider a light cone as all points out to infinity then that’s the entire universe. Instead at each point in time you have a different light cone that extends to the age of the universe. In theory we can never see past a second limit based on the expansion of the universe, but that’s yet to be observed speculation without any consistent theory of what’s going on.
- snackman7 8y ago
  Is the only reason to investigate the universe to look for ways to exploit it?
  - wallace_f 8y ago
    The argument is it's beyond our observable universe. It's not possible to be investigated as we can receive no information.
analog31 8y ago
Ah, but if someone on a distant planet were to record their perspective, e.g., data about their visible universe, and transmit it to us, it would be consistent with our perspective by the time it reaches us. For instance, stars that they can see but we can't, would become visible to us as their message reached us.
- tabtab 8y ago
  They couldn't transmit such a message; the part beyond "the wall" is moving away faster than light: the data would never reach us. From our perspective, their earlier era is "frozen" in time: red-shifted to zero. We cannot receive any "new" signal from them. Therefore, the seeming "faster than light" violation is not really the case. Relativity "fixes" it by mucking around with time. From a practical perspective, the red-shift horizon is a pretty solid "wall". The Orange Dude would love it. There could be a million Darth Vaders or run-away planet-eating nanobots on the other side, and they can never touch us. Maybe that's a good thing. The Egyption Empire lasted an extra long time largely because it was so hard to invade. It might even be the Anthropic Principle "protecting" us from really dangerous things.
  - jobigoud 8y ago
    > the part beyond "the wall" is moving away faster than light: the data would never reach us To nitpick, the wall itself is moving away at about one light-year per year. The photons that are not moving from our perspective because they are receding away from us at the speed of light will soon find themselves in a space where they are again moving towards us. "we routinely observe galaxies that have, and always have had, superluminal recession velocities" -- Davis & Lineweaver.
    - tabtab 8y ago
      Are you sure about that? While there may be a "neutral zone" where that's the case, it's only a small percent of the stuff that's beyond our senses.
- roywiggins 8y ago

Well, yeah, but our perspective is the only one that can possibly matter for us. There may be unicorns and leprechauns out beyond our light cone for all we know, but what possible reason would there be to care?

empath75 8y ago
What happens on the far side of the moon doesn't matter for us, either, but we still looked.
- lisper 8y ago
  > What happens on the far side of the moon doesn't matter for us, either, How do you know? Maybe the far side of the moon is chock-full of exploitable resources. You can't know until you look. > but we still looked. Sure, because we could. We cannot look beyond our light cone.
  - Retric 8y ago
    For now we can just by waiting. With every second we see just a little further. Tomorrow we might look out at the stars and see the tips of giant teeth. But, probably not.
    - lisper 8y ago
      You don't quite understand the concept of a light cone. Yes, we get new data all the time, and the extent of our horizon is growing. But it is always finite. You cannot look backwards past the big bang singularity, and you cannot look forwards beyond "now" for any value of "now".
      - ieo838jdkd 8y ago
        We can’t But 200 years ago we “didn’t need” relativity and then we did Asking questions and wondering about the things we don’t know is how we now know about many valuable things that, in the past, didn’t appear to be valuable
      - nbulka 8y ago
        You may want to temper your claims with "based on the currently accepted Standard Model" or "with high probability." Because paradigm shifts occur.
        lisper 8y ago
        See my OP: https://news.ycombinator.com/item?id=18094991 https://news.ycombinator.com/item?id=18094991 "Barring some major unforeseen revolution in our understanding of physics..."
      - Retric 8y ago
        No, you fail to understand a light cones end at finite points. If I travel 1 light year, then I observe a different light cone and it takes 1 year for somone that stayed behind to receive information from me. This effectively means you can see something before the light cone at your current location would observe it. If you consider a light cone as all points out to infinity then that’s the entire universe. Instead at each point in time you have a different light cone that extends to the age of the universe. In theory we can never see past a second limit based on the expansion of the universe, but that’s yet to be observed speculation without any consistent theory of what’s going on.
snackman7 8y ago
Is the only reason to investigate the universe to look for ways to exploit it?
- wallace_f 8y ago
  The argument is it's beyond our observable universe. It's not possible to be investigated as we can receive no information.

analog31 8y ago

Ah, but if someone on a distant planet were to record their perspective, e.g., data about their visible universe, and transmit it to us, it would be consistent with our perspective by the time it reaches us. For instance, stars that they can see but we can't, would become visible to us as their message reached us.

tabtab 8y ago
They couldn't transmit such a message; the part beyond "the wall" is moving away faster than light: the data would never reach us. From our perspective, their earlier era is "frozen" in time: red-shifted to zero. We cannot receive any "new" signal from them. Therefore, the seeming "faster than light" violation is not really the case. Relativity "fixes" it by mucking around with time. From a practical perspective, the red-shift horizon is a pretty solid "wall". The Orange Dude would love it. There could be a million Darth Vaders or run-away planet-eating nanobots on the other side, and they can never touch us. Maybe that's a good thing. The Egyption Empire lasted an extra long time largely because it was so hard to invade. It might even be the Anthropic Principle "protecting" us from really dangerous things.
- jobigoud 8y ago
  > the part beyond "the wall" is moving away faster than light: the data would never reach us To nitpick, the wall itself is moving away at about one light-year per year. The photons that are not moving from our perspective because they are receding away from us at the speed of light will soon find themselves in a space where they are again moving towards us. "we routinely observe galaxies that have, and always have had, superluminal recession velocities" -- Davis & Lineweaver.
  - tabtab 8y ago
    Are you sure about that? While there may be a "neutral zone" where that's the case, it's only a small percent of the stuff that's beyond our senses.
roywiggins 8y ago