The typical way that I've seen Einstein's gravity expressed is by taking some spherical object, placing it into some sort of low-resistance space (like a very relaxed trampoline), and noting how it creates a funnel-like shape. Then, one proceeds to take an additional ball and spin it around the central object, thus explaining the concept of a planet's orbit.

In the trampoline example, the central object cannot completely collapse through the material. In space, however, I'm not sure that there would be any reason that the sun shouldn't continually "fall." There's nothing holding it up.

I'm sure that there is a scientific explanation for it (perhaps the black hole at the center of our galaxy is creating a funnel in space that the Sun is riding), but since I'm uneducated, I do not know it.

So, is the Sun continually falling or is it static? What processes explain it?

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    $\begingroup$ I think you are taking the analogy too literally. But since I'm not expert myself, I wont attempt to explain it. There are some existing questions that may help you: physics.stackexchange.com/q/90592 $\endgroup$ – corcholatacolormarengo Jun 29 '20 at 23:37
  • $\begingroup$ @corcholatacolormarengo Perhaps I am, but that's sort of inevitable with someone uneducated on physics, which I am. And I'll take a look at that. Thank you. $\endgroup$ – Beliod Jun 29 '20 at 23:41
  • $\begingroup$ What does "falling" mean here? $\endgroup$ – WillO Jun 29 '20 at 23:54
  • $\begingroup$ @WillO No idea how to approach that question. I've repeated that I'm scientifically illiterate. $\endgroup$ – Beliod Jun 30 '20 at 0:06

The rubber sheet analogy works only as an analogy of what happens. Remember that the universe is 3-dimensional while the trampoline has only 2 dimensions. The dimple stretches the trampoline into the 3rd dimension. In the real 3D universe, the dimple would be in the 4th dimension. Also, you may recall that the earth also makes a small dimple in the sheet. Importantly, so does everything else in the universe.

With that proviso, in answer to your question, yes, the sun is continuously "falling" - in this case around the centre of the galaxy. This is happening for the same reason that the earth orbits around the sun, or the moon and artificial satellites around the earth.

In all cases the "fall" is controlled by Newton's laws.

When the speed of a satellite is high enough, it will travel completely around the earth. During that travel it is constantly falling towards the centre of the earth, but moving sideways fast enough (7.3 km/s for low-earth orbit) to continuously "miss" the earth.

The sun orbits the galactic centre in the same way. It travels not only around the black hole at the galaxy's centre, but it's orbit is also influenced by all the other stars (and dark matter) in the galaxy - all of those create their own dimples in the "galactic trampoline".

While the moon orbits the earth in just over 27.3 days (relative to the stars, or 29.5 days relative to the sun), the sun takes around 250,000,000 years to make one orbit around the centre of the galaxy.

  • $\begingroup$ Precisely what I wanted to know! This was an excellent answer, and I appreciate it. I'll give it the checkmark when the time-limit permits me. $\endgroup$ – Beliod Jun 30 '20 at 0:08

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