Billions of years in the future, Earth and Mars could smash into oneanother. How and why could this colossal cosmic collision occur? And what does an extremely erratic pendulum have to do with the fate of the Earth?

Video chapters

00:00 Hello, Mars!
00:28 Simulating the Solar System
01:36 Two pendula are better than one
03:10 Chaos in the Solar System
06:08 Keep an eye on Mars…

Sources and further reading

This video is based on the results of this 2009 paper, enticingly entitled ‘Existence of collisional trajectories of Mercury, Mars and Venus with the Earth’: https://www.nature.com/articles/natur...

This is a great popscience summary: https://science.howstuffworks.com/ear...

And this fantastic nerdybutreadable essay by one of the authors of that paper goes into a lot more detail: https://arxiv.org/abs/1209.5996

The reason these longrun simulations of the Solar System are actually useful (reassuring though it is to doublecheck the Earth isn’t going to be destroyed in the next few million years) is because they allow us to estimate the Earth’s orbit into the geological past, and understand our past climate. This more recent paper actually does the reverse: ‘we recover precise and accurate values for the [orbits] of the inner planets from 223 to 199millionyearold tropical lake sediments’. Amazing! https://www.pnas.org/content/116/22/1...

Errata

At 1:17, I say that there are ‘thousands’ of minor bodies, like moons, comets and asteroids…but I was swiftly corrected on Twitter! NASA says there are between 1.1 million and 1.9 million asteroids larger than 1 km in the asteroid belt alone https://solarsystem.nasa.gov/asteroid... and this amazing animation by @scottmanley charts our discovery of asteroids since 1970…in 8K    • Asteroid Discovery  19702015  8K r...  

At 3:58, the text that appears next to Mercury says ‘Radius: 4880 km’. This should of course say ‘Diameter: 4880 km’, or it would be nearly as large as Earth! I say ‘Mercury is 4880 km across’, which is correct…

Credits

Many, many thanks to Tran Nguyen for filming this, particularly the opening and closing shots which were shot in the dead of night, in freezing temperatures!

Many thanks also to Tom Fuller for the beautifully subtle sound design. He also made the music for Invisible London, which you might enjoy:    • The weird, invisible world of infrared   Listen to some of his music at   / editar  

And finally, extra thanks to my dad for making the wooden stand for the CHAOS PENDULUM and posting it to us during Lockdown 2!

Orbital integration code from https://github.com/hannorein/rebound

Thumbnail image adapted from https://commons.wikimedia.org/wiki/Fi... by Maggie (Margaret) Thompson, NASA’s Blue Marble https://visibleearth.nasa.gov/images/... and Mars by ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA, CC BYSA IGO 3.0 http://www.esa.int/ESA_Multimedia/Ima...

And finally…

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