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[–] 222 points 1 year ago (64 children)

"but Stephen, there are no fixed points in space. Space is relative, meaning you can only define positions relative to other things. You demand the fundamentally physically impossible of me, Stephen."

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  • [–] 50 points 1 year ago (22 children)

    Ah, but using the cosmic microwave background we actually can determine a universal coordinate system to fix a point in space.

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  • [–] 43 points 1 year ago (5 children)

    But only related to the cosmic microwave background, which, while more universal than most other reference frames, is ultimately still arbitrary

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  • [–] 9 points 1 year ago (10 children)

    Why cosmic microwave background radiation? Is that any less arbitrary than e.g. the sun?

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  • [+] 4 points 1 year ago* (last edited 1 year ago) (2 children)
  • [–] 18 points 1 year ago (35 children)

    Is it tho? Assuming there was a big bang, isnt it fair to call that origin point 0 0 0 in 3D space? Subjective space is relative, but that doesnt mean space itself is relative.

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  • [–] 54 points 1 year ago* (4 children)

    that's not how the big bang works, the whole thing about the big bang is that it was a singularity containing all of space in a single point.
    The standard analog is to take a small balloon with dots painted on it, then inflating it. The surface of the balloon is spacetime, and as it shows there is no origin, everything just gets more distant from everything else.

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  • [–] 3 points 1 year ago (2 children)

    Doesn't the balloon have a centre of mass that we can adjust coordinates to.... all the time.... at millions of km per second.

    Okay, I see your point.

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  • [–] 21 points 1 year ago (1 child)

    They are only talking about the surface of the balloon. For the purpose of the metaphor only the surface exists. Imagine infinite space. Now imagine we divide infinite space into a grid of 1 meter cubes. Now imagine we double the size of every cube. That's more or less how expansion works, it is an expansion of space everywhere, not outwards like an explosion.

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  • [–] 42 points 1 year ago (9 children)

    the big bang wasn't an explosion from a point, it was an explosion of a point in space. That one point is still expanding to this day. Everything is moving away from everything else, which wouldn't be the case in an "ordinary" explosion. We are all still in that one point, it's just that that point has expanded. The center of the universe is, in the literal sense of the word "literally", everywhere.

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  • [–] 8 points 1 year ago (2 children)

    Im kinda trollin at this point, but in an ordinary explosion, in a vacuum without external gravity, everything would indeed have a different initial velocity and direction, so everything would be moving away from everything else.

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  • [–] 21 points 1 year ago* (1 child)

    imagine standing at the side of the explosion looking towards it. some debris will be blown way from you, but some will be coming towards you. You are something, and not everything is moving away from you, some debris hits you in the face. That's an explosion in space.

    An explosion of space is defferent. Everything will be moving away from you, regardless of where you are or which side you're facing.

    Something wasn't in space and it exploded. Space itself exploded. your argument only holds if you are exactly in the explosion source.

    In space, we're still inside the explosion

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  • [–] 9 points 1 year ago (4 children)

    So from wherever you look, the universe is expanding away from you (I.e., other things in it move away from you).

    Therefore, you can see that the universe doesn't have a centre. From this and some other a bit more complicated things, one can see that the Big Bang never had a single point but rather expanded everywhere at once when it happend. Although often called expansion from one point that is wrong.

    Also technically you would need to give a time dimension as we live in 4D space.

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  • [–] 4 points 1 year ago (2 children)

    So from wherever you look, the universe is expanding away from you (I.e., other things in it move away from you).

    Wouldn't that be the case even with a center?

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  • [–] 7 points 1 year ago

    the 0 0 0 0 (spacetime) orientation system would be possible if the universe was a minkowski space and thus flat, but spacetime is curvy due to relativistic effects, which prevents any sort of flat orientation like that

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  • [–] 2 points 1 year ago (2 children)

    Think of a balloon expanding. All the dots on the surface are moving away from one another. No dot is the centre.

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  • [–] 2 points 1 year ago (1 child)

    Out of my depth here, but it seems that objective timespace coordinates can be determined while still meshing with relativity.

    I'll just leave this here so someone else can explain why I'm wrong:

    https://en.m.wikipedia.org/wiki/Proper_time

    I know 4D spacetime can be non-euclidean, but I believe those are localized to areas experiencing relativistic extrema.

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  • [–] 2 points 1 year ago

    Proper time is only defined along a timelike world line, e.g. the timeline of a specific reference point / object. It's "objective" in the sense that is true for the reference point, but other reference points may (for example) perceive distant events in a different order

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