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 [email protected] 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.