# What happens if you sail through gravity waves?

1. Jul 28, 2016

### Nerophysics

Hi

I am currently writing a sci fi book for children, and I wonder what happens with a spacecraft if it sails through powerful gravity waves? Does it have any consequences for the ship/crew at all? How abundant are gravity waves in space if you are sailing between stars or galaxies?

Thank you!

2. Jul 28, 2016

### Orodruin

Staff Emeritus
Basically nothing unless you are very close to the source. If you are, you will likely have other things to worry about.

3. Jul 28, 2016

### Nerophysics

Hi

And thank you for the answer. So basically nothing would happen? But, in theory, if you where very close to the source, would anything happen? What "other things" do they have to worry about? Obviously, two colliding black holes would cause some problems, but do you have anything else on your mind? Also, I seem to remeber that gravity waves where ripples in space. If gravity wells can make our earth orbit the sun, why shouldnt ripples of gravity be able to effect a spaceship? How would these ripples - dangerous or not - interact with the spaceship, I mean? Would ut be like being on the sea in a ship - swells of water making the ship moving up and down?

4. Jul 28, 2016

### Orodruin

Staff Emeritus
This sounds overly popular scientific. They are disturbances in the space-time geometry. If you want to call this "ripples", go ahead, but it is not the scientific term.

Basically not at all. Gravity is very weak and detecting gravitational waves was an astonishing experimental feat that involved measuring relative path length changes of $10^{-21}$.

5. Jul 28, 2016

### Ibix

Gravity waves are a type of surface waves on water. You mean gravitational waves.

Gravitational waves cause stresses in things like ships - if the gravitational wave is travelling in the x direction, say, then the ship is slightly stretched then slightly squished in the y direction and vice versa in the z direction. By "very slightly", I mean that a 10km long ship will stretch less than a millionth of the diameter of an atom. As Orodruin notes, our very best and most sensitive detectors can only just detect them as they pass.

If you are closer to the source, the waves will be stronger. But since the source is likely to be a couple of black holes or neutron stars spiralling into each other, you are probably going to be fried by the radiation emitted by their accretion discs long before you notice the gravitational waves.

We don't really know how many gravitational waves there are floating around. We've detected two in a few months. But we're well aware that our detectors are extremely primitive and we don't expect that they're spotting all the waves out there.

Gravitational waves are no hazard to navigation, in short, if that's what you are asking.

6. Jul 28, 2016

### Nerophysics

In order for children to understand, or visualize what you are writing about, you need to paint pictures. That’s why famous people like Stephen Hawking or Neil deGrasse Tyson paint pictures when they explain.

And - to be fair - I am not too happy about the word "disturbances". Even words like oscillations or waves are better when it comes to gravitational waves. The oscillations that propagate through space are called "waves" instead of oscillations.

And, if you want to use the correct word that physicists use when it comes to "disturbances" - the correct word is polarization. For instance, an elliptically polarized gravity wave looks like a rotating helix, but it is still called a "wave".

7. Jul 28, 2016

### Janus

Staff Emeritus
Put another way, if you are close enough to a strong gravitational wave source for them to be a nuisance, they are going to be the least of your problems.

8. Jul 28, 2016

### Nerophysics

This is the kind of intelligent, scientific and wonderful answer I was searching for. Thank you very much!

Now, I shall study accretion discs! Hopefully, the spaceships deflection shields will be powerful enough for a little bit of neutron star exploration.

I have also posted a question about black holes - whether there is superheated plasma in them or not.

I hope someone like you will give me an answer. But in any case -

Thank you!

9. Jul 28, 2016

### Nerophysics

Also, I will save your answer and use it as a scientific guideline in my writing.

10. Jul 28, 2016

### Orodruin

Staff Emeritus
They are not explaining, they are popularising. Please separate these two. Explaining is describing how gravitational waves actually work using mathematics, the language in which is used to describe them. Popularising is painting a picture in terms of similarities and regular spoken language and will never be as precise as the actual explanation.

Do you know the actual description of gravitational waves in terms of mathematics then? Otherwise, how do you pretend to construct a better likeness?

No it is not. You clearly have not understood the underlying mathematics.

11. Jul 28, 2016

### Ibix

Worth noting: Orodruin has forgotten more about gravitational waves than I know. Take his comments seriously.