What would happen if I flew through a gravitational wave?

09 August 2016

Question

Hi, Im a huge fan of your show. I have a question. If two blackholes collide and there is a ripple of time in space, what would happen if you flew through it? And what other situations can change time itself?

Answer

We put this to astronomer Matt Middleton from the University of Cambridge...

Chris - Now this happens on Star Trek a lot, so I'm really interested to hear the answer to this.

Matt - What?

Chris - People flying through a.

Matt - ...gravitational wave?

Chris - Well, an anomaly in the space-time continuum?

Matt - OK.

Chris - It happens a lot and Jean-Luc Picard's hand went all funny in a fruit dish once and I always wondered how one would argue that from a physics point of view.

Kat - I think we've identified the Trekkies in the room!

Mat - Singular, singular! OK, so obviously a very pertinent question given that LIGO has directly detected gravitational waves...

Chris - LIGO?

Matt - LIGO is the Laser Interferometer Gravitational Wave Observatory, and they detected gravitational waves for the first time, and these are formed when black holes merge. They can be formed in other ways too but that's what's been discovered from LIGO. So these waves, they propagate outwards and they're crashing through us all the time. Right now, gravitational waves are going through us. We don't feel them because the...

Chris - I don't know, I went to the curry house last night and I've had gravitational waves afterwards!

Matt - Oh that's beautiful - what a lovely image! The strength of gravitational waves falls away inversely with distance and, because these things are astrophysical in origin, the gravitational that cross us are infact very very weak. And in fact, LIGO had to detect the Sun moving by the width of human hair. That's how accurately they had to do their measurements. That's absolutely phenomenal!

What essentially happened though is that if you add two particles together and a gravitational wave goes through them, they'd be pulled apart and compressed at the frequency of that wave. It would be like a tidal force when the moon goes round the earth, so pulls and pushes, stuff like that. So in terms of time though, the effect is extremely minimal.

Chris - But does it actually do anything different to your body? Does that mean, literally, parts of your body are experiencing time slightly differently as the wave goes through you?

Matt - Time... probably not. The time dilation effects are going to be extremely minimal but in a physical way you would feel a tug. It would be like a tidal force so as if you were.

Chris - But a very small one?

Matt - Very, very small for us. If you got very close to the black hole, then there would be a huge tidal force but then your days about to get much, much worse! I don't know if that was on Star Trek? And then you are in a seriously different realm of time dilation effects.

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