How To Become an Astrophysicist + Challenge Question (Patreon)

Want to become an astrophysicist? Hopefully this video will seal the deal - either that you definitely should or DEFINITELY should not.

Today’s episode is a bit different. I’m going to tell you how to become an astrophysicist. I have a slightly unique perspective on this not because I did it myself, but because I spent the past several years sitting on and tåhen running the physics PhD admissions committee for one of the largest universities in the US. I have an idea of what it takes, so I thought I’d share some of the stuff I’ve learned. Maybe some of this will be useful to anyone thinking of chasing this silly path – but also to those of you just curious about the process. You might come out of this even happier that you didn’t go down this rather unforgiving rabbit hole. I’m going to end with some astrophysics that we can all try - a challenge question for our recent episodes on the eternally inflating multiverse.

Let me start by telling you about my own path. It was typical enough. I started out with a deep fascination in physics – in understanding the nuts and bolts of how the universe works. I knew I had to study physics at university but honestly had no expectation of it becoming a career – I just needed to know. But I caught the bug and decided to try my luck at the most fun field in physics - astrophysics, of course. I sent out applications to grad school – all outside of Australia because I had a major itch to travel. I got some rejections and got some offers – ultimately deciding to head to NASA’s Space Telescope Science Institute in Baltimore. Which is a great town, by the way. Even in undergrad I was no longer the smartest person in the room – but in grad school I sometimes wondered if I was the dumbest. Serious ego check, serious imposter syndrome, which I still experience regularly. You’ll get used to that. But I tell myself if I’m always the smartest person in the room then I’m probably in the wrong room.

Grad school had massive ups and downs and I thought of quitting plenty of times. But it was amazing - I was using the Hubble Space Telescope to help unravel the connection between quasars and galaxies. As many others also found, the two evolve hand in hand, each influencing the other. It was so cool to work on an unknown problem like that.

Finally I scratched together a thesis and the university gave me a balloon. I had to rent the hat and robe. I was a newly minted astrophysicist and through connections I made in grad school scored a nice job working with the Gemini Observatories. This was a postdoctoral position – a postdoc – which means a short-term job – typically 2-4 years. Most astrophysicists do a couple of postdocs before looking for permanent jobs. 

As that first postdoc was winding down I had more thoughts of quitting astrophysics. I was just feeling burned out. I needed change. I applied for more astro postdocs, but also other jobs. I ended up having two offers – one was still in Melbourne, but in bioinformatics – the information science of genetics – turns out many, many other fields – science and otherwise – want the analytical skills of all brands of physicist. The other offer was an astrophysics postdoc at Columbia University in New York. So, do I switch careers or switch cities? That was a very tough decision – but I’d always wanted to live in New York, so I set sail once again. 

The real career hurdle was still ahead – getting that permanent job. This is where the numbers are against us. There are way more astro postdocs than permanent positions, whether at universities, observatories, NASA, or private foundations. In my case I got lucky – I scored a professorship at the City University of New York and that was the first point in my entire career where I thought I might be able to stick with this gig. Oh, and then I started making YouTube videos because god forbid I take it easy for a bit.

If you’re thinking about pursuing physics or astrophysics, in fact many of the hard sciences – then your path might look similar to mine.  I’m going to focus on the first part of the process – getting into a PhD program. Getting a PhD is pretty much non-negotiable. There are jobs for those with just undergraduate or masters degrees, but prospects are relatively scarce.  Let me also say right now that it’s never too late to start. I know people who started in their 30s, 40s, 50s, even 60s. Most are much more sure of their goals than a fresh college graduate, and so often have much more focus and determination and they can do very well. 

Starting out, your focus is convincing some folk on an admissions committee to actually pay you to come do a PhD at their university. The first step is to take a ton of mathematics and physics at an undergraduate. Most astro PhD programs require a good foundation in the fundamentals of modern physics – doesn’t really matter what you major in, but by the time you’ve taken all that physics you probably qualify for a physics major anyway.

And while you’re at it, get good grades. I’m afraid this also isn’t negotiable. Graduate admissions committees are looking for As and Bs. A couple of lower grades won’t kill you, but don’t make a habit of it. You’ll also want to put serious effort into whatever standardized test your country has – the GRE in the US. Me saying “get good grades” might sound glib, but it’s important to emphasize. For one thing admissions committee folk have to sift through  up to hundreds of applications each year. Most will filter by your grades before they read your nice personal essay. But also, working your ass off as an undergraduate will help you learn whether a life in science is really for you. You may end up finding that your talents lie elsewhere – and that’s fine. At least you’ll know you gave it your best shot.

The other thing to do as an undergrad it to try to do some sort of research. Convince a prof at your university to give you a small project. That looks good on your application, should get you a letter of recommendation from the prof, and most importantly will help you figure out if you actually like research. You should also look at various REU programs. These “research experience for undergraduate” programs may actually pay you to do research between semesters. One absolutely critical thing to do as an undergraduate is to find a mentor. This could be the prof who you’re going research with, or just some faculty member or even postdoc who you can talk to. Don’t proceed blindly. Get as much advice as you can.

OK, so it’s time to apply to grad school. Research different graduate programs – are they doing stuff you’re interested in at that university? Would you be cool moving to that city or country? Don’t just apply to top-tier schools – there are many truly excellent grad programs that don’t have Ivy growing on the walls. Visit campuses and talk to profs and students there if you can. There are a lot of resources online for how to craft a good application. Use them.

Send out a bunch of applications – hopefully you’ll get some bites. If not, don’t despair. You can bolster your application for next year – do some more undergrad research, retake the GRE exam or equivalent. Look into bridge and masters programs – these can help to prep you for grad school. However I would NOT recommend paying lots of money out of pocket to do a masters just to improve your chance at getting into a PhD program. At any point keep your mind open about other career paths. There are so many cool things to do out there, especially if you have a good science undergrad degree. 

Once you’re in a PhD program then you’ll have access to many new mentors who can give you as good advice as I can, or better. Find those mentors. It’s going to be a challenging time – but it will forge you into a scientist. One piece of advice regarding grad school– find the straightest path to patching together a thesis. Writing this tome may seem daunting, but you have much, much cooler work ahead of you – just get it done. Because once you have that PhD your options open up massively, both in the field and out of it.

OK, this gets me to the big question: should YOU pursue a PhD? The reasons to do it: you want to spend your life trying to answer the biggest questions there are, you want to gaze upon the wonders of the universe and bring this incredible perspective to enrich humanity, because you just have to know how it all works. All good reasons to spend a decade in school for pretty average pay.

The reasons NOT to do a PhD are many: don’t do it because you’re ok at math and can’t think of anything else to do besides staying in school. Don’t do it if you want to earn the big bucks. Don’t do it if you don’t want to have to move city or country every few years until you get permanent job. Don’t do it if you want to maintain the illusion that you’re the smartest in the room. Don’t do it because you like the idea of yourself as a scientist more than you like doing science. 

The fact is, with the job situation as it is, the odds are stacked against getting that permanent position. So you better love the journey and all the awesome science you get to do along the way. The job includes as much or more frustration and boring stuff as it does unlocking the mysteries of the universe. You gotta love the latter enough to get through the former. Don’t do a PhD because you want to be an astrophysicist, do it because you want to do astrophysics. At least for a while.

OK, enough rambling. Myself and other poor suckers on this path will answer specific questions in the comments. For now, let’s get on with it and do some actual 

astrophysics. I have a challenge question based on our recent episodes on cosmic inflation. You’ll definitely need to have watched those to get this. In those episodes we saw how an inflating universe can produce bubbles in which inflation stops, each a newly-born universe. In eternal inflation, this process goes on forever. But inflation also had a beginning – so how many bubble universes exist today? That’s not something we can easily calculate – but there’s something we can at least estimate. 

Let’s assume that every second, there’s a set chance of a new universe forming in any given volume of space. So every second, many bubble universes are forming across the greater eternally inflating spacetime, and more universes form than in the previous second because there’s more volume. My question is this – compared to the number of universes that form this second, how many more universes form in the following second? Twice as many, 1000 times as many? Less? More? To answer this you’ll need to assume a rate for inflation – let’s assume the minimum rate needed to explain the horizon and flatness problems - all distances increase by a factor of 10^26 every 10^-32 seconds. 

And an extra credit question: at that rate, how close to our universe would a new bubble universe need to form in order for the two bubbles to collide before inflation throws them too far apart?

Write up your answer neatly, show all your work and draw nice diagrams if you can. Submit answers within 2 weeks of release of this episode to pbsspacetime@gmail.com with the subject line eternal inflation challenge. Check your spelling because we filter by subject line. We’ll select 6 correct answers to win your pick of space time merch from the merch store as well as conference of the degree Doctor of Spacetime. Which won’t get you any professorships, but your parents will be very proud. Or if you hate homework you can just buy that merch – link in the description. We’ll announce the winners in an upcoming episode, where we’ll also learn some of the crazier consequences of an eternally inflating spacetime.