**Ask a monkey a physics question thread**

[MadMojoMonkey]

No. Does not compute. Either the milky way is on its way into that black hole, or it isn't.

Black holes don't "suck things up" any differently than any other massive body. I blame Hollywood for this one.

If something is in orbit, it will remain in orbit unless / until an outside influence affects that relation.
The pull exerted by gravity doesn't necessarily pull things into collision courses.

A galaxy isn't a rigid object. It's more like a gas, if we think of the stars as particles.

In order for something which is in orbit about the black hole to alter its course, it must change its energy.
Conservation of energy states that in order to change its energy, it must cause an equal and opposite change in energy to something else (the system around it).
If it is not interacting with anything nearby (the prevalent case for most stars not near the galactic nucleus), then it cannot change its energy, and the black hole can't "suck it in."
In order for something to be "sucked in" it has to deliver some of its energy to another body or bodies in the system.
So in order for something to be sent on a "sucked up" collision course, something else had to be sent the other direction.

So your question is incorrect. It assumes that ALL of the Milky Way will be consumed by the black hole or NONE of it. The actual answer is in between. Some of the Milky way will end up as Sagittarius A*, some of it will be flung into intergalactic space.

Assuming that it is, at some point, going to be consumed by the black hole, then wouldn't that make the black hole bigger, denser, and with a stronger gravitational pull? In other words, it will be able to consume things from further away. And so on, and so on.

As black holes consume matter, they grow in size and the gravitational effect on spacetime increases.

Yes, but this rate of expansion is slow, because most of space does not contain anything to consume... hence the name, I suppose.

So what's stopping these black holes from eventually consuming the entire universe?

Some of the stuff in the universe is moving away from the black holes at a rate faster than their escape velocity. The growing gravitational influence of the black holes is not fast enough to counter this.

When we look at the longest time scales and play the guessing game about what will happen, there is an extreme time scale at which all the stars have burned out, all the stellar remnants have burned out, and the only things left are black holes and a smattering of hydrogen atoms in the diffuse "vacuum" of space.

Eventually, even the black holes evaporate and the universe is left a diffuse gas of particles, each separated by their closest neighbor by distances too vast to overcome their relative velocities to ever stop them and pull them back into a bound state.

[BananaStand]

None of that sounds right.

Some of the stuff in the universe is moving away from the black holes .....

OR...they're moving toward other black holes that you don't know about.

I think it's pretty obvious that everything in the universe is getting pulled into black holes, and eventually they will start to converge, and coalesce until the entire universe is compressed into a singularity.

Then the big bang will happen again.

Just need to reconcile that with this whole "expanding universe" narrative. Maybe our observation point (earth) is being moved away from stuff so it just looks like the universe is expanding. I wonder if that has anything to do with the massive black hole sucking us in right now.

[MadMojoMonkey]

None of that sounds right.

Irrelevant.

QM sounds like loony talk. GR sounds like loony talk.
This is not relevant so long as these models produce accurate predictions of observable phenomena.

OR...they're moving toward other black holes that you don't know about.

Which either means
A) we already discussed that in the prior discussion and that object is NOT unbound, as it merely swapped its binding state from one SMBH to another.
or
B) the other black hole it's moving toward is receding away from it fast enough that they will never be bound to each other

I think it's pretty obvious that everything in the universe is getting pulled into black holes, and eventually they will start to converge, and coalesce until the entire universe is compressed into a singularity.

I'd love to see the evidence which makes this so obvious to you.
I can't wait to read your publication which clearly shows that decades of data have been misinterpreted.

Then the big bang will happen again.

Our current data suggests that the dark energy acceleration is prevalent over gravitational acceleration over the longest length scales.

Just need to reconcile that with this whole "expanding universe" narrative. Maybe our observation point (earth) is being moved away from stuff so it just looks like the universe is expanding. I wonder if that has anything to do with the massive black hole sucking us in right now.

The problem with your assertions is that there is a wealth of evidence which indicates that those hypotheses do not form or fit into a consistent model which makes accurate predictions about observable phenomena.

[BananaStand]

The problem with your assertions is that there is a wealth of evidence which indicates that those hypotheses do not form or fit into a consistent model which makes accurate predictions about observable phenomena.

So what you're saying is, I've made an unprecedented discovery.

If you don't watch your attitude, I might not mention you in my nobel prize acceptance speech.

[MadMojoMonkey]

So what you're saying is, I've made an unprecedented discovery.

What I'm saying is, what you're saying is literally the opposite of both unprecedented and discovery.

Your position on this has its appeal. There is a consistency to it. It also makes predictions. That's a hallmark of good science.
... as many have pointed out before you
However, plenty of those predictions don't hold up to observations, e.g. the existence of dark energy (whatever it may turn out to be).
Which has been discovered by other people, but apparently not you, yet.

I respect that you hold out for when the data shows your assertion doesn't hold up to observations before you yield your position.
It's silly that the data is well and truly in, and you clearly haven't internalized it, yet you persist that your assertions are still correct.

If you don't watch your attitude, I might not mention you in my nobel prize acceptance speech.

I find it great that you are openly skeptical of what I'm dishing out, here.
I find it mostly amusing that you come here to tell me I'm wrong about physics.
Admittedly, I find it mildly irritating that you put forth such brazen confidence in assertions that are demonstrably false.

It would be hubris to assume I hold no misconceptions.
This thread invites challengers to poke holes in what I understand and can explain (as simply and clearly as possible).
You might be amused by my reaction when they made me chase down the rabbit hole of virtual particles. Turns out it's a lot of hand waving and talk about these things which cannot be observed by definition.

If a virtual particle is observed, it is NOT a virtual particle, by definition.
THIS IS NOT WHAT I SIGNED UP FOR!!!