- Wanna become an astrophysicist?

Hopefully, this video will seal the deal.

Either that you definitely should, or definitely should not.

(upbeat music) Today's episode is a bit different.

I'm gonna 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 then running, the physics PhD admission's 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 gonna end with some astrophysics that we can all try.

A challenge question for our recent episodes on the eternally inflating universe.

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 that I had to study physics at university, but honestly, I had no expectation of it becoming a career.

I just need to know.

But I caught the bug, and decided to try my luck at the most fun field in physics, astrophysics.

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 told myself that if I'm always the smartest person in the room, then I'm probably in the wrong room.

Grad school has 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, I scored a nice job working with the Gemini Observatories.

This was a postdoctoral position, a postdoc, which means a short-term job, typically two to four 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 for other jobs.

I ended up having two good 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 physicists.

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 question, but I'd always wanted to live in New York, and so I set sail 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 gonna focus on the first part of the process, getting into a PhD program.

Getting a PhD is pretty much nonnegotiable.

There are jobs for those with just undergraduate or master's degrees, but the 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 30's, 40's, 50's, even 60's.

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 to a PhD at their university.

The first step is to take a ton of mathematics and physics as and 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 of that physics, you probably qualify for a physics major anyway.

And while you're at it, get good grades.

I'm afraid this one isn't negotiable either.

Graduate admissions committees are looking for A's and B's, a few lower grades won't kill you, but don't make a habit of it.

You also wanna put serious effort into whatever standardized test your country has, the GRE in the US.

Now, me saying get good grades might sound glib, but it's important to emphasize.

For one thing, admissions committee's folk have to sift through up to hundreds of applications each year.

Most of them will filter by your grades before they read your nice personal essay.

Also, working your butt off as an undergraduate will help you learn whether a life in science is really for you.

You may end up finding out that your talents lie elsewhere, and that's fine, but at least you'll know that gave it your best shot.

The other thing to do as an undergrad is try to do some research.

Convince a prof at your university to give you a small project.

That looks good on your application, it should get you a letter of recommendation from that prof, but most importantly, it'll you figure out if you actually like research.

You should also apply for various REU programs.

These are research experience for undergraduate programs, and they may actually pay you to do research between semesters.

One absolutely critical thing to do as an undergraduate is find a mentor.

This could be the prof you're doing research with, or just another faculty member, or even a postdoc you can talk to.

Don't proceed blindly, get as much advice as you can.

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 even 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, talk to profs and students there if you can.

There are a lot of resources online for how to craft a good application, use 'em.

Send out a bunch of applications.

Hopefully you'll get some bites.

In not, don't despair, you can bolst your application for the next year, do some more undergraduate research, retake the GRE exam or equivalent.

Look into bridge, or master programs.

These could help prep you for grad school.

However, I would not recommend paying lots of money out of pocket to do a master's program 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 gonna 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.

Okay, this gets me to the big question, should you pursue a PhD?

The reasons to do it: You wanna spend your life trying to answer the biggest questions there are.

You wanna gaze upon the wonders of the universe and bring this incredible perspective to enrich humanity.

Or 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 think you're okay at math and can't think of anything else to do besides stay in school.

Don't do it if you wan to earn the big bucks.

Don't do it if you don't wanna have move city or country every few years until you get that permanent job.

Don't do it if you want to maintain the illusion that you're the smartest person in the room.

And 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.

Okay, 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 has a beginning, so how may bubble universes exist today?

Well, that's not something we can easily calculate, but there is 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 every second more universes form than in the previous second because there's more volume.

My question is this, compared to the number of universes that formed this second, how many more universes form in the following second?

Twice as many?

A thousand 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.

That is, all distances increase by a factor of 10 to the power of 26 every 10 to the power of negative 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 answers neatly, show all of your work, and draw some nice diagrams if you can.

Submit answers within two weeks of release of this episode to pbsspacetime@gmail.com with the subject line "Eternal Inflation Challenge," and check your spelling because we filter by subject line.

We'll select six correct answers to win your pick of "SPACE TIME" merch from the merch store, as well as the conference of the degree of Doctor of Spacetime, which won't get you any professorships, but your parents will be so proud.

Or if you hate homework, you can just by 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 any eternally inflating spacetime.

(ambient music)