Strange

Yes. The only difference, really, is that you can get closer to the source of the gravity with a black hole. This means that as you approach the lack hole, there will be greater gravity than the surface gravity of the sun (because closer to the mass). In GR there are extra effects like time dilation and frame dragging but (as far as I know) these will be the same at the old radius of the Sun (or further out).

While that is true, the curvature of space-time (at any given distance) will be unaffected by the size of the mass at the centre; it just depends on the mass. After all, the curvature of spacetime is what creates gravity and we know that is only dependent on mass and distance (not size). I don't think there are any extra, subtle effects in GR that change this.

I'm trying to get my head round your mental model here. If you move something (your teacup) from position A to position B, you didn't have to move empty space from B to A. Space is just the set of dimensions/measurements where the cup exists - moving the cup, changes where we measure it to be, but doesn't change the measurements of space around it. (Ignoring the minute gravitational effect!) Similarly, if your teacup shrank it would change the measurements of the cup but not the space it is in.

Or Advocaat?

I assumed it must have been softened or shelled already to get in the bottle?

That seems to assume that "volume" is a thing, like water or something. Changing the size of something doesn't change the space it is in. Water expands when it freezes (enough to burst pipes) but it doesn't "push space away".

Heat the bottle. Use chalk and hydrochloric acid. Use one of those gas bottle openers that pumps CO2 into the bottle through the cork. Put Mentos and coke in the bottle. Put Champagne n the bottle and shake it. Or that.

Why? As I and others have said, it is because the air molecules collide with one another (and with the Earth and everything else around). AEBanner hasn't explained why this isn't explanation isn't acceptable (even though it also seems to be the explanation he is providing - go figure). The collisions transfer the weight of the air.

You could, and it would be the same. Or, at least, I can't see why it wouldn't be. I'm not sure why the time difference (which is probably quite small - we can calculate it if necessary) would make a difference to the volume. Say we use the orbit of Neptune (also start of the Kuiper belt) as the radius. It averages 30 AU (about 4.5 million km). So you can work out the volume of that sphere. It won't change if the sun becomes a black hole, because the orbit of Neptune won't change.

Then why does the pressure change with altitude? The collision of molecules That pressure is caused by weight (alone).

Well, I would take it to mean the volume of a sphere with a radius corresponding to [whatever we consider the edge to be]. I think the edge of the solar system is sometimes defined by where the solar wind stops (the heliopause), but that would no longer apply in this case. But whatever (slightly arbitrary) boundary you choose, I don't see why it would change.

This is the same sort of hopeless naivety that doomed similar ideas like Rousseau's Social Contract: https://en.wikipedia.org/wiki/The_Social_Contract I think it would be more effective to look for practical solutions.

It would get rather chilly, though. No. It would just be as if the Sun had got smaller. It would have no significant effect on the rest of the solar system. The loss of the solar wind would probably have a detectable effect on some things (tails of comets, atmospheres of planets, etc)

It would have a radius of about 3km (assuming no change in mass). Gravity follows an inverse square law and so it has limits on distance. The size of the source has no effect, either. The planets would continue to orbit the black hole as if nothing had changed. Yes, the mass is directly proportional to the radius. Set the mass to "1 solar mass" in this calculator and see the results: http://xaonon.dyndns.org/hawking/ (Note you need to change the units first and then the number)

Perhaps you should find a forum in your native language.

Maybe try a DIY forum?

Exactly. The fact that molecules in a gas bounce off each other has exactly the same effect as the balls in your (or my) example constantly pushing one another. The collisions are a "push"; just a way of transferring the force from one to another. So it is the weight that determines how much pressure there is, but it is the collisions that allow the pressure to be transferred as a force.

Then why would the balls press down if not because of their weight and the weight of those above? Obviously, if the balls /molecules did not push against / collide with each other then there would be no pressure.

Imagine a fluid made of (frictionless) spheres. The weight pushing down would also push back up on the other side of the plane. And this is what happens with water or air. The fact that the collisions between the molecules in these fluids cause them to have less density is not really relevant.

There two other possible causes: the Doppler effect (relative motion) or gravitational redshift. (The Pound-Rebka experiment neatly combines those two: https://en.wikipedia.org/wiki/Pound–Rebka_experiment)

And how are you going to do this?

i2 = -1 is not an impossibility. How are you going to do that?

Although, thinking about it, the shortest distance between two points on the surface of the Earth is a great circle, but I suspect that is not what you are thinking of. So the shortest distance between London and Paris is an imaginary circle?

So the shortest distance between London and Paris is a circle? That doesn't make much sense.

! Moderator Note Please take a bit more care with your formatting. Your giant white on blue text was unreadable. I have fixed that for you but please don't do it again.