What effect do gravitational waves have on your body?

The biggest news in physics this year was the discovery of gravitational waves a couple months ago. Waves in time-and-space are cool, but they are very weak, the detectors measured a distortion in space of one part in 1021 (or 1 in 1,000,000,000,000,000,000,000). That’s a small effect. On the one hand this is bad, as it made them very very hard to detect; the scientists on the LIGO collaboration must be experimental science ninjas and it still took them decades.

But it also has its advantages, the risk of being killed by a gravitational wave has to be a very very small number. You have to figure you are lot more likely to succumb to a meteorite from outer space than to gravitational waves. The LIGO scientists faced many challenges but filling out health & safety forms on the risks of the gravitational waves, was not one of them.

Having said that I am not sure that gravitational waves have absolutely zero effect on our bodies. The distortion is not observable of course, even a tall 2.0 m person is only stretched to 2.000000000000000000002 m by the wave. Not a major problem.

The wave will also distort the molecules in our body, but again by tiny tiny fractions. Consider a pair of molecules just about to react, in one of the chemical reactions that power and run our bodies. Naively for two molecules close enough to react, the gravitational wave will change the probability of a reaction by about 10-21 – a tiny amount.

So for an individual reaction, the effect is negligible, but my body has maybe 1025 DNA bases, amino acids etc, some of which are reacting every second. So, although the change in reaction rate is completely negligible, presumably, due to being hit by a gravitational wave, some reactions occur that would not have done so without the wave, and similarly others would be stopped.

The number could be handful, could be a thousand, either way a completely negligible fraction of the total, but not zero. Somewhere in your body there maybe a small sugar molecule that only exists due to a gravitational wave hit the enzyme at just the right time.

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