Gravitational Waves: Mass Interaction Questions Answered

In summary, gravitational waves behave similarly to light waves, with their intensity decreasing as they escape from a gravity well. It is not possible for a wave to be completely absorbed, but it can be converted into heat and eventually re-emitted. However, in the case of a black hole, the wave would be converted into Hawking radiation instead.
  • #1
NotASmurf
150
2
Hey all. Since gravitational waves travel at the speed of light, when they are "escaping" from mass, doe's their intensity lower? If so what mass would be needed to completely absorb a gravitational wave given the wave's properties? Any help appreciated.
 
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  • #2
NotASmurf said:
Since gravitational waves travel at the speed of light, when they are "escaping" from mass, doe's their intensity lower?

In other words, do they behave like light waves and "redshift" as they climb out of a gravity well? I believe the answer is yes, but I have not seen any detailed treatments of this.

NotASmurf said:
what mass would be needed to completely absorb a gravitational wave

A wave can't really be "completely absorbed". Consider the analogy with electromagnetism: an object absorbs EM waves if it can take their energy and turn it into heat--i.e., into vibrations of its atoms (or molecules). But that heat will gradually get transferred, and at least part of it will go into EM radiation again--for example, objects at room temperature emit (mainly) infrared radiation, i.e., EM waves. So the original EM waves didn't get "completely absorbed"; they just got converted into other EM waves.

Similarly, a mass might convert the energy of incoming gravitational waves into heat, but that heat will get radiated away again, and some of it (at least in principle) will be radiated as gravitational waves again. So the gravitational waves won't get "completely absorbed".
 
  • #3
So even if a gravitational wave from an external source hits a black hole, it will be partially absorbed, but will still be re-emitted? or would it all be converted to hawking radiation?
 
  • #4
NotASmurf said:
even if a gravitational wave from an external source hits a black hole, it will be partially absorbed, but will still be re-emitted?

Black holes are not ordinary objects, so no, not the way you mean.

NotASmurf said:
or would it all be converted to hawking radiation?

Yes. Technically that counts as "re-emitted", but you distinguished it from other possible ways of being re-emitted, none of which are possible for a black hole.
 

1. What are gravitational waves?

Gravitational waves are ripples in the fabric of spacetime that are created when massive objects, such as black holes or neutron stars, accelerate. They were predicted by Albert Einstein's theory of general relativity and were first observed in 2015.

2. How are gravitational waves detected?

Gravitational waves are detected using extremely sensitive equipment called interferometers. These devices use lasers to measure tiny changes in the distance between two test masses caused by passing gravitational waves.

3. What is the significance of detecting gravitational waves?

Detecting gravitational waves confirms the existence of these ripples in spacetime, which were predicted by Einstein over a century ago. This discovery opens up a new window for studying the universe and allows us to observe events, such as the collision of black holes, that were previously undetectable.

4. Can gravitational waves travel faster than light?

No, according to Einstein's theory of relativity, nothing can travel faster than the speed of light. Gravitational waves travel at the speed of light, just like all other forms of electromagnetic radiation.

5. How can we use gravitational waves to learn more about the universe?

Gravitational waves can provide us with information about the objects that create them, such as their mass, size, and velocity. By studying the properties of these objects, we can gain a better understanding of the universe, including its origins and evolution.

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