After hearing a chance snippet of something on the radio last week, I’ve been thinking about what is known in Mathematics/Physics/Astronomy as the ‘three body problem.’ It remains one of the great questions in Mathematics as to whether it will ever be solved, or if indeed it actually can be.

The essence of the problem is simple: take three heavy masses (planets/moons/astral bodies) and give them an initial position and velocity. Can we calculate what the subsequent motion of these three bodies will be?

The mathematics is perfectly well understood – the laws of gravitational attraction are easy to write down, and for just two bodies the calculations are simple. But add a third body, another other, and the calculations become not only fiendishly complex but, according to some great minds, actually insoluable. Some special cases are open to analysis, but no general solution appears within reach: the motion of the three bodies cannot be predicted and will not be captured by our infinitessimal calculus. In practice? The motion of the sun and earth and moon can only be estimated. The tide cannot be predicted perfectly.

As a Mathematician and amateur theologian, coming across problems like this makes me reflect synthetically. I am the earth, you the moon and God the sun, each of us with our gravity, each our own graces, our own orbits. Despite all the power of the machines and algorithms we have around us, no one can predict the future trajectory of our interactions, whether we will spin into chaos, collapse and collide or find some periodic stability.

And this is both the problem and beauty of our engagement with the other, and the Other: not only is the subsequent motion complex, it may well be incalcuable. The rational, material, scientific mind has to admit defeat. As in the heavenly bodies, so on earth: we can only estimate where the forces of attraction may take us.

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## 3 responses to “The Three Body Problem | Incalcuability”

So…how does this apply with Mars coming next to the Moon on August 27th? Or does it? Just wondering what happens to the tides of Earth and how does this effect our weather on our planet. Does Mar’s closeness effect gravitational pull on our planet or the moon’s? Basically, what the heck is going to happen when it comes this close to us? Earthquakes? Tsunamis? Volcanic Eruptions? or just pretty to see?

Thanks,

Deb ;)~

Yes, it will have an effect. The three body problem is simply a version of the ‘n-body’ problem, which is obviously even more incalcuable, though models will suggest some basic effects that may be likely.

I doubt it would stretch to earthquakes and volcanic activity though!

If I make the Sun to be all which is unknown, your analogy works for me. I did not know about this “Three Body Problem” — thank you.