“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.”
Ah, but using the cosmic microwave background we actually can determine a universal coordinate system to fix a point in space.
But only related to the cosmic microwave background, which, while more universal than most other reference frames, is ultimately still arbitrary
North is arbitrary as well, that doesn’t mean you can’t use it for spatial referencing.
It can be as arbitrary as it wants it still allows you to use relative positioning to determine a fixed point.
Why cosmic microwave background radiation? Is that any less arbitrary than e.g. the sun?
i mean if we were to communicate with aliens in another galaxy it would be the “least arbitrary” one
Well, it’s the only thing we know of that can be used in the whole universe.
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.
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.
That’s absolutely right; there’s no special origin point in space where the Big Bang began. However, there is a specific reference frame that the Big Bang occured in, which we can measure by looking at the redshift of the cosmic microwave background left over from it. The solar system is currently moving at around 600km/s relative to that.
Interestingly, this is actually an expanding reference frame due to the universe’s expansion, so two observers locally at rest relative to it will each see the other moving away.
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.
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.
Like one of those pills you put in water and it turns into a sponge TRex!
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.
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.
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?
Think of a balloon expanding. All the dots on the surface are moving away from one another. No dot is the centre.
If they are all moving away from each other, that means if you reverse time they will all converge at a single point, which would be the center.
I’m just going to jump on the bandwagon and helpfully say; think of the universe as a large expanding paper bag.
Initially it was flat, but then the bagger expanded it in the third dimension and put bananas in it. Imagine now that you are one of those bananas, but oh no, here comes the 2L Pepsi bottle ready to crush us. Thankfully the bagger takes us out of the bag first, puts the cola bottle in, and then puts us back in on top.
And that’s why I believe in God
The big bang created the universe within space. Space is literally, just space, an endless empty (as far as we know) vacuum.
The big bang created the universe within space.
This is not the accepted model, it wouldn’t work with our current observations. There was no “outside” space before space started expanding. When the universe was smaller, it was also infinite but an infinitely dense medium with nothing outside of it. The whole universe was infinitely dense energy, there was no “outside” or “inside” to speak of, even the geometry of spacetime was infinitely distorted, so there was no “before” or “after” states for literally anything.
Time and space didn’t begin until the expansion event. At that point, if it were possible to be an observer, it would seem like suddenly everything stretched away in all directions from all points, and this allowed interactions and events to start occuring, which we mark as the passage of time.
No the big bang also created space time. The bang is the bang of space going from a point to infinite 3d space + time.
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.
I studied general relativity last year and ACKCHYUALLY…
Pfft! I read about it on a box of cereal 5 minutes ago and think I’ve come to some novel conclusions.
The earth is rotating, which is a non-inertial reference frame. Fido simply uses its own reference frame, which following the command is now inertial. The result is that Fido is no longer affected by gravity, and slowly floats away just as in the comic
This makes me sad.
Also, it’s a little inaccurate as the dog would be moving at hundreds of thousands of kilometers per hour, either burning up in the Earth’s atmosphere or plowing through its surface. Also, I don’t think dogs have the ability to do this, so there’s that.
We have never truly tested the limits of dogs. Only the limits of what THEY think we want.
Good boy. Maybe too good.
because fixed points in space (stationary reference frames) fall inwards into gravity wells as time progresses, Fido, would need to burrow into the center of the earth. Fido should shoot into space like that if told to stay at a fixed point relative to the cosmic microwave background
