What’s the Use In Physics?


[epistemic status: this is mostly vague impressions I’ve accumulated]

I’m an undergraduate physicist interested in effective altruism, and have noticed in several places (here, here) that physics is offhandedly mentioned as a promising research area and/or skill to possess. However, so far, I haven’t seen any specifics; no indexing of research topics in physics with DALY numbers and instructions, or organisations that hire physicists, or anything like that.

I can’t write that article either, though to get something in this space (hey, it's highly neglected!) I’m going to describe some uses of physics and EA areas where I’ve seen physics be done.

Not Doing Physics

The EA recommendation I tend to see for physicists is to not do physics. I mean, nobody's said that explicitly, but physics has been passed over in recommendations for other fields for potentially good reasons.

Physics is, instead, useful because it gives you good quantitative skills, and a physics qualification is useful because it gives you a reliable signal of quantitative skills. Instead, consider a more useful field to employ the power of mathematics, like AI safety (via computer science) or global priorities research (via economics).

This is somewhat uninspiring to those excited by physics, though not as much as at first glance: AI safety is still about discovering universal truths, and global priorities research is still about using mathematics to predict experimental outcomes.

Still, there are some things that can be done even within the purview of the physics department, which is what the rest of this post is about.

Studying the Large-Scale Structure of the Universe

Most of the value that a civilisation will produce lies in the far future, and that means that the shape of the far future dictates how civilisation will behave and how much value it will capture. The long-term evolution of the universe is dictated by cosmology. Whatever conclusions are drawn have big implications in what behaviour we should expect to see from other civilisations, if any, and potentially in what our civilisation should do.

Some work I’ve seen in this area is Bostrom’s Astronomical waste paper which follows from knowledge about the size of the universe and the rate of loss of usable mass-energy. Knowing more about this would give better bounds on the tradeoff between existential risk and hastening technological development (also relevant here: the scale of s-risks).

The behaviour of other civilisations helps put bounds on the Fermi paradox, which might give us some insight into existential risk for our civilisation via determining the existence, size and location of the Great Filter(s). In this area we have Sandberg’s Spamming the Universe paper (summary: it is relatively easy to colonise the entire universe), and the Aestivation hypothesis paper (summary: the best use of mass-energy might be to wait until the universe is very cold before doing anything).

Also in this field is the idea of Boltzmann brains. If these will exist, they would make up most experience in the cosmos, which means that research to find out what the deal with them is might be valuable.

Philosophy and Foundational Research

Physics, as the science about how the world works at its most fundamental level, has a thing or two to say about how the world works at its most fundamental level. Counterintuitive discoveries from physics might lead to ethical insights that we wouldn’t have developed otherwise.

Using special relativity, Beckstead argues in On the Overwhelming Importance of Shaping the Long Term Future that there should not be an ethical asymmetry between space and time: if two civilisations exist simultaneously and outside each other’s light cones, then there is a reference frame where one civilisation lives entirely before the other. There's no classical analogue to this.

The many-worlds interpretation of quantum mechanics suggests that there exists a multiverse, which might have some implications for what one should do: there are decision-theoretic arguments for why certain actions we take might affect other universes, for example. Other potential sources of multiverses in physics include the possibility of eternal inflation, or the mathematical multiverse hypothesis. More physics research could give insight into the distribution of worlds, and avoid confusion among non-physicist foundational researchers about what a multiverse actually entails.

There’s also Brian Tomasik’s post on suffering in fundamental physics that you've read. Knowing what fundamental physics says about the world seems like it would be essential for this question; even with a complete understanding of consciousness it wold be important to know what processes are implemented by physics to say anything at all about any experiences, if any, that might be had.

Climate Science

Tail-end risks from climate change do have a chance of reducing the value of the long-term future (through, say, wiping out human civilisation), and like everything that affects the long-term future that makes them very important. Research into modelling the Earth’s climate would give us a better idea of where these risks lie and how best to mitigate them. This could be both directly (via geoengineering) and to better inform policy decisions (such as by predicting which populated areas will face the most heating to forecast geopolitical problems).

This is also, as of the time of writing, the topic of the only physics-related thesis on Effective Thesis.

Molecular Nanotechnology

Molecular nanotechnology seems in principle possible, and also seems like it would lead to massive economic growth if done properly. Many of the problems in molecular nanotechnology are physics problems, since it involves handling objects like individual atoms on small scales.

A crucial consideration in nanotechnology is its effect on x-risk: in the worst case, there’s a grey goo scenario (do some physics to evaluate the risk of this happening!), but even in ordinary cases nanotechnology might lead to weapons becoming much cheaper and computers becoming much cheaper (making the hardware overhang much worse if AI safety isn’t solved yet). Nanotechnology x-risks seem to be very neglected; better knowledge of the feasibility of molecular nanotechnology might help with this.

General Economic Growth Acceleration via Science

The standard use of physics is to make discoveries, which are eventually converted into actual applications that do something to improve someone’s life later down the line. This doesn't seem like it would be very neglected, because physicists have a direct incentive to do this (an easier time applying for funding), though historically it does seem to be the source of most of the good from physics. Since everything is a power-law, exceptional physicists might still be best placed here; I think Einstein doing physics was one of the best things that he could have done, simply for being so damn good at physics.

Other Things

And now I turn to you, Most Esteemed Reader. There are, undoubtedly, things that I've missed, and probably other material on this topic that's been published elsewhere. What else could potentially be done with physics in order to do the most good? Is there anything in physics that seems much more promising than other areas?