The video discusses the use of computer simulations to study astrophysical phenomena, from galaxy formation to planet and star formation. The simulations are performed using N-body methods and smoothed-particle hydrodynamics, among other approaches. The simulations are limited by computational power but are becoming increasingly powerful and sophisticated. However, the simulations do not provide a complete picture of the universe, as a full quantum description would require unimaginably more information. The video ends with a shoutout to Wren, a website where users can calculate and offset their carbon footprint.
1. In around four and a half billion years, the Andromeda galaxy and our own Milky Way will finish their long mutual plummet.
2. On a first grazing pass, the delicate spiral arms will be yanked almost out of their sockets.
3. In a series of whirling collisions, all spiral structure will be obliterated, gas will be compacted to produce waves of supernovae, and the giant Milkdromeda galaxy will have been born.
4. We know this because we have calculated the chaotic gravitational and hydrodynamic interactions of countless stars and gas and dark matter particles over billions of future years.
5. We routinely simulate the universe on all of its scales, from planets to large fractions of the cosmos.
6. In 1941, the Swedish astronomer Erik Holmberg conducted what was probably the first simulation of the universe.
7. Since the time of Isaac Newton, it has been possible to write down equations describing the trajectories of a pair of massive bodies moving in each other’s gravitational fields.
8. This only works for 2 objects.
9. For 3 or more bodies, there is no simple set of equations describing their future evolution under gravity.
10. Holmberg did what we call a numerical calculation, in which an impossibly complex computation is broken down into a series of much simpler steps.
11. In an N-Body simulation, Newton’s laws of motion and gravity are applied over a series of time steps.
12. The predictions of these N-body simulations can be as accurate as you like, as long as you make the time steps small enough.
13. Astrophysicists have come up with some ingenious tricks to deal with the challenge of dealing with a large range in scale.
14. Perhaps the most important is to avoid having to consider every single particle pair.
15. None of these simulations contain the full information of an actual universe - or even a tiny part of it.
16. A full quantum description of the world contains unthinkably more information than is contained in a typical simulation, which just tracks particle positions and velocities.
17. No conceivable technology could fully simulate a quantum universe, except perhaps a cosmically-sized quantum computer.