observantTrapezium

I'm pretty sure I'm in my fourth pair now.

How about no fucking spoilers in the title and thumbnail?

That may be relativists (they would actually measure anything in units of mass, with everything else defined through G = c = 1). Astrophysicists commonly measure mass in solar masses, long distances in parsec (or kiloparsec, megaparsec), short distances in solar radii or AU, and time in whatever is relevant to their problem (could be seconds or gigayears)

It's a map of the AƧU

The balrog was already awake, but maybe wasn't paying attention 😜

They are quite similar to electromagnetic waves, but also quite different. They are produced by masses accelerating (just like EM waves are produced by charges accelerating), and indeed cause orbital decay. But this orbital decay is only important in relativistic systems (so the Earth, which is orbiting the sun at 0.0001 the speed of light, is not going to fall into the sun because of gravitational waves).

See my response below to Captain Aggravated about how dilute those large stars are.

It's an interesting question whether anybody would actually feel spaghettification 😁 I actually don't know. You can use physics to calculate the proper time derivative of the tidal forces, but you need biology to define the start (and end...) of the process. My intuition says that it probably happens too fast, so once the tidal forces are strong enough to be perceptible, they grow strong enough to rip you apart before you realize (again, just a hunch).

Yes, but red supergiants differ from the sun in that their photospheres are extremely dilute and don't have a sharp transition to the corona. I don't know the details of this particular star but take Betelgeuse as an example (it's probably not particularly large for this catrgory), it's radius is ~640 the sun's per Wikipedia, which gives a volume of ~260 million that of the sun. But it is only x15 times as massive as the sun, so on average ~20 million times less dense.

Yep, you got it right. The accretion disk is actually really flat. Those images are produced in simulations that take into account the curved (and very complex) paths light takes in the vicinity of a black hole. These images really depend on the angle between the line of sight and the disk.

In the case you are unlucky enough to encounter the black hole "heads on" and fall into it radially, the proper time timescale to spaghettification is the size of the event horizon divided by the speed of light. The most supermassive black holes will have a horizon of around one light day, so that's what we're working with, a matter of days. If you come in on the most tangential orbit possible though, I guess you're buying some time but I've never heard that it's supposed to take many years of proper time (I doubt that claim a little bit, but haven't calculated myself).

Astrophysicist here. Yes, space is crazy, but interesting things to keep in mind:

1. The size of a star is determined by something called the photosphere. With those extremely massive stars, you can be hundreds of millions of kilometres "inside" and not yet know it.
2. Similar story with supermassive black holes, from the perspective of an astronaut falling in, they wouldn't really be able to tell when they cross the horizon because the tidal forces there are very small (they will inevitably fall towards the centre and get spaghettified at some point)

QWERTY on a cheap Dell keyboard I've had for 12 years.

I'm sure some of the alternatives are objectively superior, but with all due respect to enthusiasts, I'm simply not passionate about it and have yet to be convinced that the time and pain spent on getting used to a new layout would actually be worth it in the long run.