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.
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.
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.
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.
I’ve been struggling to not see it as explosion/outward expansion. This really helped!