How long before we get sucked into the central black hole?

Factual Questions
1

The Milky Way galaxy is essentially an accretion disk for the gigantic black holes in the centre of the galaxy, right? So, how long will it be before the Earth gets sucked in?

OK, this is going to be billions of years, but I’ve just been watching Dr Who.

2

Near as I can figure it sometime after the Andromeda Galaxy and our Milky Way Galaxy collide so unfortunately you can’t take a decrease of the night’s stars as a guide.

3

If I were you, I’d stockpile canned tuna and ammunition. This is gonna make Y2K look like a big nothing.

4

It’s going to make everything a big nothing.

5

Nah. The accretion disk for the central black hole is much, much smaller, and even that hasn’t been very active these past few æons. Most of the matter in the Milky Way Galaxy is in perfectly stable orbits, and isn’t going to fall in, ever.

6

Oh. So you mean I do have to finish that report that’s due next Thursday? Damn.

7

Actually, IIRC all orbiting objects give off gravity waves, in analogy to synchrotron radiation, and all orbits slowly lose energy and decay. Verrrry, verrrry slowly. So, if you were willing to wait many billions of billions of years, everything would fall in.

8

I had a hunch that someone would bring up orbital decay by gravitational radiation. Yes, in principle, absent all other effects, gravitational radiation would eventually cause any “stable”, closed orbit to decay. But the real Universe isn’t absent all other effects, and there are a heck of a lot of them that work much more quickly than gravitational radiation, on the scale of a galaxy. Any given object in the Milky Way is overwhelmingly more likely to be ejected by n-body interactions than it is to infall into the central hole by gravitational radiation.

9

I think proton decay might become a problem first. Or, maybe not.

Tris

10

Sol leaving the main sequence and swelling up into a red giant will happen a lot sooner. We’ve got 4-5 billion years to pack.

11

Yes dear. it looks just fine and your bum doesn’t look big in that, now can we get the bags into the car, you’ve taken simnply forever to sort out your wardrobe.