<p>Since we know reasonably well that "normal" (stellar sized) black holes do not contribute significantly to dark matter and that the source of energy for gravitational waves is the mass/energy of those black holes <em>when they are in binary systems</em>,  then it's hard to how such gravitational waves can contribute to dark matter, especially as they are only emitted significantly in the last moments of a black hole merger.</p>

<p>The assertion that black holes radiate gravitational waves when they accelerate isn't quite right. It is a necessary condition, but there needs to be an accelerating quadrupole mass moment, and an isolated black hole cannot emit gravitational waves.</p>

CC BY-SA 4.0
2019-09-29T09:40:00.787Z
2019-09-29T09:40:00.787Z
ProfRob
<p>Can accelerating black holes radiate their mass as an gravitational wave?If that is true maybe dark matter is not something but it is just gravitational waves from an exhausted  dense object.</p>

CC BY-SA 4.0
2019-09-28T23:49:28.813Z
It's a wild leap from your first sentence to your second one.  Doing science requires a step-by-step approach, and not wild guesses.  You'll learn more doing the step-by-step approach.  It's faster in the long run.
StephenG - Help Ukraine
CC BY-SA 4.0
2019-09-28T23:50:00.107Z
@StephenG since we cant isolate dark matter , then guesses are acceptable and specially guesses which are based on the laws of physics.
Bright Future
CC BY-SA 4.0
2019-09-29T00:39:18.977Z
Physics is not a guessing game.  If you had read more about the reasons dark matter has been postulated to exist you would understand that no guessing is involved.  It's about experiment and developing (methodically) a mathematical model to match results.
StephenG - Help Ukraine
CC BY-SA 4.0
2019-09-29T02:13:45.410Z
Since dark matter interacts with normal matter through gravity we cant measure or test anything . What are you talking about?
Bright Future
CC BY-SA 4.0
2019-09-29T02:15:14.230Z
How would that even work? Why are your black holes accelerating for billions of years, and how do they manage to stay roughly in the same place for so long, despite that acceleration? Why do they even need to accelerate? What's the relevance of gravitational waves to dark matter?
PM 2Ring
CC BY-SA 4.0
2019-09-29T02:20:40.000Z
They would not stay in the same place! The gravitational waves created through the acceleration travelled vast distances while bending space-time.They could come from another galaxy....
Bright Future
CC BY-SA 4.0
2019-09-29T02:22:18.027Z
How can we understand if the shape of space-time in one region is caused by an object or a gravitational wave?We can't .
Bright Future
CC BY-SA 4.0
2019-09-29T02:22:32.193Z
Same effect , different source.
Bright Future
CC BY-SA 4.0
2019-09-29T02:31:51.077Z
Gravitational waves travel at the speed of light, transmitting *changes* in the spacetime curvature. So how do you explain relatively static dark matter halos via waves moving at lightspeed?
PM 2Ring
CC BY-SA 4.0
2019-09-29T02:41:34.907Z
dark matter is just the peaks of a gravitational wave
Bright Future
CC BY-SA 4.0
2019-09-29T02:48:26.880Z
Sorry, that doesn't make sense. Gravitational waves just don't work like that.
PM 2Ring
CC BY-SA 4.0
2019-09-29T02:53:55.057Z
If you read about dark matter you would understand how we make measurements that show it seems to be required to explain what we measure.  You do not even seem to have read Wikipedia's page on the subject (pretty much the minimum we expect posters to do prior to asking questions on science related SEs) which has a lot about observational evidence.
StephenG - Help Ukraine
CC BY-SA 4.0
2019-09-29T02:55:07.017Z
Ok idk how to explain it.If i were next to you i would draw you my idea.
Bright Future
CC BY-SA 4.0
2019-09-29T02:59:57.167Z
GW are just classical waves.Ok ?Every wave has peaks and roughs.
Bright Future
CC BY-SA 4.0
2019-09-29T03:00:22.437Z
GW are just like EM waves!
Bright Future
CC BY-SA 4.0
2019-09-29T03:01:05.857Z
@PM2Ring sure since i dont say anything exactly how the book says it , i have to say it wrong.
Bright Future
CC BY-SA 4.0
2019-09-29T08:16:34.610Z
Note that the first sentence actually does contain a good question with a nontrivial answer, but the stuff about the dark matter made me downvote it.
Anders Sandberg
<black-hole>
Black holes exhaustion
Bright Future
# Black holes exhaustion

(Asked by: username_0 on 2019-09-28)

Can accelerating black holes radiate their mass as an gravitational wave?If that is true maybe dark matter is not something but it is just gravitational waves from an exhausted dense object.

**Tags:** black-hole

> **Comments:**
> **username_1**: It's a wild leap from your first sentence to your second one.  Doing science requires a step-by-step approach, and not wild guesses.  You'll learn more doing the step-by-step approach.  It's faster in the long run.  
> **username_0**: @StephenG since we cant isolate dark matter , then guesses are acceptable and specially guesses which are based on the laws of physics.  
> **username_1**: Physics is not a guessing game.  If you had read more about the reasons dark matter has been postulated to exist you would understand that no guessing is involved.  It's about experiment and developing (methodically) a mathematical model to match results.  
> **username_0**: Since dark matter interacts with normal matter through gravity we cant measure or test anything . What are you talking about?  
> **username_2**: How would that even work? Why are your black holes accelerating for billions of years, and how do they manage to stay roughly in the same place for so long, despite that acceleration? Why do they even need to accelerate? What's the relevance of gravitational waves to dark matter?  
> **username_0**: They would not stay in the same place! The gravitational waves created through the acceleration travelled vast distances while bending space-time.They could come from another galaxy....  
> **username_0**: How can we understand if the shape of space-time in one region is caused by an object or a gravitational wave?We can't .  
> **username_0**: Same effect , different source.  
> **username_2**: Gravitational waves travel at the speed of light, transmitting *changes* in the spacetime curvature. So how do you explain relatively static dark matter halos via waves moving at lightspeed?  
> **username_0**: dark matter is just the peaks of a gravitational wave  
> **username_2**: Sorry, that doesn't make sense. Gravitational waves just don't work like that.  
> **username_1**: If you read about dark matter you would understand how we make measurements that show it seems to be required to explain what we measure.  You do not even seem to have read Wikipedia's page on the subject (pretty much the minimum we expect posters to do prior to asking questions on science related SEs) which has a lot about observational evidence.  
> **username_0**: Ok idk how to explain it.If i were next to you i would draw you my idea.  
> **username_0**: GW are just classical waves.Ok ?Every wave has peaks and roughs.  
> **username_0**: GW are just like EM waves!  
> **username_0**: @PM2Ring sure since i dont say anything exactly how the book says it , i have to say it wrong.  
> **username_3**: Note that the first sentence actually does contain a good question with a nontrivial answer, but the stuff about the dark matter made me downvote it.  

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## 1 answers

### Answer by username_4 on 2019-09-29. Score: 4 | Accepted answer

Since we know reasonably well that "normal" (stellar sized) black holes do not contribute significantly to dark matter and that the source of energy for gravitational waves is the mass/energy of those black holes *when they are in binary systems*, then it's hard to how such gravitational waves can contribute to dark matter, especially as they are only emitted significantly in the last moments of a black hole merger.

The assertion that black holes radiate gravitational waves when they accelerate isn't quite right. It is a necessary condition, but there needs to be an accelerating quadrupole mass moment, and an isolated black hole cannot emit gravitational waves.


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