I just finished my finalist interview for the Hertz Fellowship, and I feel a bit of an obligation to share my experience with anyone who is interested in hearing about it. When I was applying it was incredibly difficult to find any information on Physics or Astronomy related applicants. I applied for the fellowship under the field concentration of Astrophysics. Applying, I already knew I had the odds stacked against me simply looking at the history of previous recipients of the fellowship. The last person to receive the fellowship for Astronomy was in 2007 (16 years ago) as of 2023. The Hertz Foundation mantra is advancing the world with real tangible breakthroughs that will have large positive impacts. That's a hard sell when you tell them you study galaxies and space stuff outside of the solar system.
Anyway, I applied mainly because I figured why the heck not. I was shocked when I found out that I made it to the first interview in November and even more so for the finalist interview. I had my first interview via Zoom in early December and my finalist interview in-person in San Francisco in mid-February. I had a pleasant experience with my interviewers in both rounds although I will admit the first round, I had to play a bit more defensive than I anticipated. I’m not sure if they’ve always done this, but every interview now is conducted by 2 established Hertz Fellows, and they notify you of who your interviewers are going to be before the interview (~2-4 Weeks before) so you can do your research. They won't expect you to know everything about your interviewers’ fields of study, but they do implicitly expect you to look for connections between your work and theirs and be able to have conversations around those topics. The interviews were a little different so I will outline my experiences for each of them below.
(Update: I ended up winning the fellowship! I hope reading this helps if you plan to apply.)
My interviews for this round were a Geography Professor at UC Berkeley (Interviewer A) studying hydrology and an ex-director of the Department of Energy (Interviewer B) who is also an expert in fluid dynamics, nuclear fusion, and national defense. The theme here is that the interview is field matched. This means they find interviewers who are experts in what you study. As an Astrophysicist, the closest thing they had in their arsenal for me were essentially physicists with emphasis on fluid dynamics (space is basically just a whole bunch of gas which is roughly a fluid). I think it is important to also mention here that I study astrophysical magnetohydrodynamics and cosmology using higher-order statistics algorithms and numerical simulations. Basically, I like magnetic fields interacting with gasses in space, and I like studying the evolution of the universe. So, to be fair, this was basically right up my alley.
I was TERRIFIED of the Hertz interview, everything I read about it online made me think they could ask me literally anything in the universe and I was just supposed to know it. That’s not true, in fact it's far from the truth. The whole point of the interview is to put a personality to an application and see how you think. They don’t necessarily care that you get the exact right answers, but they want to know if you retained problem solving skills for real world problems. I HIGHLY HIGHLY recommend taking an Order of Magnitude physics course at your university if it is offered, I would say it is literally the perfect studying for the interview. If that’s not available, try this book which might help. Questions the interviewers are thinking about are: okay so you don’t know the answer right away, how would you stumble/hobble your way to one? What goes through your head when you’re faced with a challenging problem? There is a bit of an art to “showing your work” in an oral exam, verbally stating what is going on in your head is crucial to showing them you know what you’re talking about. If you just sit there in silence, you’ll probably fail. If you just give up and say “I don’t know” you’ll probably fail. If you at least try, failure is not guaranteed.
Okay, now let’s break down this interview step by step. Below is a condensed/paraphrased dialogue summarizing my experience:
*Greetings and a few opening remarks from interviewers establishing the process, introductions, and so on
Interviewers: Tell us about yourself, and your pathway here? How did you get here, what do you want to do in graduate school?
Me: I explain my background, my experiences, and why the Astrophysics PhD program is a fit for me. (I always try to plant seeds for discussion to come back to later and emphasize my personality through quick charming stories rather than giving them a CV reading) This took ~10% of the interview.
Interviewers: Let’s talk about creativity, tell us a time when you were creative in your work? Feel free to talk about 1-2 of your projects. (This is the queue to talk about your research, they are not looking for other extracurricular activities here)
Me: I began discussing my work. I highlight my first-author work, namely I discuss the python package I made for measuring higher-order statistics and my contribution to this work. Having led the project, I was comfortable discussing this at both a high and low level. I like to start off simple and offer to expand in places that could get more complicated if they would like to hear about it. You want them to get the general idea of your work first if they are unfamiliar with it (being an Astrophysicist, this was a requisite for me). I try to have a pre-made speech about my work at various rigor levels, but always try to convey the exciting part of my work as the “punchline” so that they feel inspired by it. I got them very excited about my work because it can extend well beyond astrophysical applications and my creativity came from my clever algorithm development and python programming abilities with the help of my research mentor. This will be different for everyone but just do your best to get them interested in your work if you can, and appeal to their fields if possible. I also jumped into my second first-author project here discussing cosmology at a surface level with them and I also got them very engaged in this as well. I love teaching, so this comes naturally for me, but if you don’t feel comfortable teaching, I recommend having some pre-thought-out speeches on your work. (This worked very well for me because we spent about 60% of my interview talking about my research… this means the ball was in my court 60% of the interview )
Interviewers: Interviewer B hit me with a real hard question: Why is Astronomy a science? Of course, it's a science in the sense you can make and validate a hypothesis and all, but what real world applications does any of this have? You talk about these galaxies and the cosmic web with statistics but how does that impact the real world in any way?
Me: I wasn’t expecting this question, but luckily, I teach an introductory astronomy course at my university, so I was well equipped to answer this question. I did my research on Interviewer B and knew that he was a practical guy that cares about national defense and more specifically nuclear fusion. My reply to this was that astronomy may seem far-fetched and inapplicable, but you can thank a lot of the modern world for astronomy. For example, Nuclear Fusion as a concept was introduced by an astronomer (Arthur Eddington in the 1930s) to explain how stars have enough fuel to glow so bright and hot for billions of years! Then I mentioned the idea of using the WKB approximation for a particle with enough kinetic energy that could overcome the Coulombic Potential Barrier to lead to fusion. I also mentioned how X-ray machines and metal detectors in airports were created thanks to Astronomers building X-ray telescopes to study high-energy phenomena in space. I basically said, we are light scientists. Light and quantum mechanics basically govern modern technology and astronomy is exploring those frontiers. He was impressed by this and mentioned to me how he gets annoyed when astronomers always answer that question with “GPS is a real-world application of Einstein’s theory of General Relativity” because of a technicality or something I can’t quite remember. I started arguing with him on this comment and I guess I came off a little aggressive because he said “I don’t want to argue with you” …. I thought I just blew this entire interview right then and there.
This took ~10% of the interview.
Note: We are now ~ 80% of the interview and the ball has been in my court this whole time
Interviewers: Okay, we need to move on to the technical part of the interview. We often look for technical skills in our fellows and that is what we’ll do now. Interviewer A asked me this question:
Q: From a hydrodynamical perspective, can you explain upwelling off the Californian coast?
Me: As an astronomer who studies stars and stuff, I was like… Um what’s upwelling? I asked if Interviewer A could perhaps define what that is, so I knew what we were talking about. This was completely out of my field, and I had absolutely no idea what upwelling was referring to.
Interviewers: Interviewer A states “Sure, sorry about that. It’s referring to a motion cycle of fluids in the ocean near coast lines where water from the seafloor rises to the surface.”
Me: In my mind, I had no idea. But I wasn’t about to say I have no idea because that would show I cave easily. In a way, being asked about something so far out of my comfort zone kind of worked in my favor because they were aware of this and hence took it a bit easier on me. I stumble around with ideas, perhaps heat coming from the Californian fault line adding additional heat to the seafloor allowing for convection?
Interviewers: Interviewer A states “Good idea, but I’m going to let you know right now that this idea is incorrect, perhaps try again from a new perspective?”
Me: (Internal thoughts are “Oh god, this is over I’m screwed”) but I keep going, I start really spit balling here. I thought well, hmm we’re going to have some winds blowing along the top of the water, and I know that when we have two shear moving fluids of different densities we can observe the Kelvin-Helmholtz Instability which would serve to mix the top layer of water with lower layers.
Interviewers: Interviewer A states “Good, I like this idea of wind. What direction is the wind flowing?”
Me: I’m not too sure, I don’t really have any pre-existing knowledge of global wind currents or wind streams. (Thinking, “if I don’t have any more info, they’ll think I don’t know anything, let’s keep spit balling”). One thing I do know about oceans though is that the Coriolis force from the Earth’s rotation has the most substantial effect on ocean currents and waves relative to other phenomena. I also mention that this can be seen when doing an Order of Magnitude estimate of the momentum equation for fluids. (I knew this from a problem in an Order of Magnitude physics homework problem I came across when studying for the interview).
Interviewers: Ah great. It’s okay you don’t know that one, so I’ll just tell you. Let’s say the wind was pointing down the Californian coast towards the equator. What direction does this Coriolis force point in our diagram?
Me: I do a little right-hand rule on screen, so they see me thinking about it. I state the direction correctly. As I’m continuing to think about other ways to create this effect my interviewer cuts me off.
Interviewers: Okay it looks like we’re out of time. Interviewer A explains the answer to me which I was walking towards but likely wouldn’t have gotten on my own without serious help or googling a bit. They ask if I have any questions.
Me: I knew this question says a lot about who I am, so I wanted to ask a good question. I thought about this a lot prior to the interview. The question I asked was “The Hertz has a strong focus on interdisciplinary collaboration, in what ways has that affected your career? Has it altered the way you do research/work?” I thought this was pretty good and so did they.
All this technical questioning was about ~20% of the interview spanning only 1 Question!
Interview Breakdown: • 10% Personal Background • 60% Research Discussion • 10% Breadth Discussion/Defense of Astronomy • 20% Technical Questions
Once you make it past the first interview, they have you upload a short bio statement and a high-resolution professional headshot. They look at these before you even start your second interview. My year there were 42 finalists that made it through to this round.
My interviews for this round were a Mechanical Engineering Professor at Georgia Tech (Interviewer A) studying thermal energy conversion technologies and a biotech entrepreneur (Interviewer B) who has made several incredibly successful biotech startups. The theme here is that the interview is non-field matched. This means they find interviewers who are not experts in what you study. This one also had me incredibly nervous because I couldn’t find much information on finalist interviews, especially for Astro or Physics. I didn’t even know that this was non-field matched until the Hertz foundation emailed me. I made sure to study a little bit about everything for this interview. I reviewed all my Order of Magnitude physics concepts covering basically all the physics fields. I made sure to also study a field or two outside of my own. I had heard from one of my mentors that they like to ask you to pick fields outside of your own and discuss them. For me those were climatology and life, biomedical imaging, and critical point phase transition biochemistry. I made sure I had 3 fields/problems I wanted to explore outside of my field to make sure that any breadth questions they asked me, I could answer them. I didn’t really expect them to ask me much about fluid dynamics or astrophysics…. but they did. I also made sure to study a lot of thermodynamics considering one of my interviewers specializes in it.
I walk into the hotel and make my way upstairs to a common area where the director of the acceptance/application committee is waiting for me along with several other finalists. He was incredibly nice and warm, making some nice small talk to help us all ease our anxiety. After a few minutes passed, our interviewers came out to greet us. Both my interviewers asked me how I was doing, and I made a joke about being slightly nervous which they laughed at. My interviewers asked if I would like any water, tea, or coffee. They were very warm, smiley, and nice. I was afraid my interviewers would be mean or something but all of that was immediately removed when I entered the conference room. They started off by saying that they loved my tie, loved my bio, and thought my teaching work was incredible. One of them said they were really excited for this interview because they love astronomy but know close to nothing about it and were hoping I could teach them some stuff about astronomy. They also said the way this works is that we are basically like your lawyers for the committee, this interview is a tool for us to gather as much information about you to bring to the committee so we can fight for you as best as we can. This immediately changed my perspective of the whole thing; I was like wait… they’re here to help me?
This interview is structured starting with introductions, bringing your personality to the table and your experiences. They also ask about your research. Then they look for the extent of your knowledge, where it extends to and how deep they can ask you about your research topics, they call this depth. Then they probe your knowledge of frontiers of science outside of your research field. This breadth discussion is called frontiers. Then they probe a bit more in depth by asking technical questions. They wrap up the interview with questions you have for them. Below I outline a similar abbreviated/paraphrased dialogue of my interview:
*Greetings and a few opening remarks from interviewers establishing the process, introductions, and so on
Interviewers: Tell us about yourself, and your pathway here? How did you get here, what do you want to do in graduate school?
Me: I explain my background, my experiences, and why the Astrophysics PhD program is a fit for me. (I always try to plant seeds for discussion to come back to later and emphasize my personality through quick charming stories rather than giving them a CV reading) This took ~20% of the interview.
Interviewers: Let’s talk about creativity, tell us a time when you were creative in your work? Feel free to talk about 1-2 of your projects. (This is the queue to talk about your research, they are not looking for other extracurricular activities here)
Me: I gave a similar speech about my python package, discussing my creative contributions to the project and what not. I didn’t get to discuss my second large project like I did last time, I think they were aware of how my first interview went so they knew to stop me there, so they’d have time for everything else. These are more senior interviewers for the foundation, so they know how to really keep the interview on the rails without detours. This took ~20% of the interview.
Interviewers: Great, fantastic. Okay so now let’s explore your depth. We can do these one of two ways, start somewhere far out and real it back in until we find the boundaries of what you know. Or we can start close in and wander farther away until we reach the boundary, what would you prefer?
Me: I said I’d prefer to start close in and move outward.
Interviewers: Okay, so you mentioned in your application and previously that you are interested in studying turbulence and that you have plans to study it further in graduate school. Are you familiar with boundary layer eddy turbulence?
Me: Um, not exactly but I think I can follow along with you.
Interviewers: Alright no worries, he proceeds to explain what he was referring to. I said “oh ya sure, okay I follow now.” They then start asking me where I think the frontier of the study of turbulence is.
Me: I start discussing where I know it in my research. I talk about MHD and higher-order stats.
Interviewers: Ah so you’re talking about MHD?
Me: Yes, more specifically in the ideal case, not accounting for non-ideal effects.
Interviewers: Okay, let’s backtrack. Let’s remove the charges and magnetic fields and discuss simple fluid flows. Are you familiar with Bernoulli’s equation?
Me: Yes, but I don’t remember the equation off the top of my head. I do know it’s very useful for streamline fluid dynamics and steady states.
Interviewers: No worries, it's basically conservation of energy and ya you’re right. Okay so, I like this discussion of streams. This matters a lot for pipe flows, what happens as fluids flow along a surface boundary layer?
Me: I got what he was referring to immediately, I studied this in my fluid dynamics course. I told them that a parcel of water at the bottom of the flow rubs against the boundary slowing down basically like friction, which in turn rubs against a parcel above that slows subsequent layers down gradually. This effect follows like the diffusion equation where we see a scaling of shear velocity proportional to the square root of height.
Interviewers: Wow, I didn’t expect you to know that. Good stuff, okay so now what happens when you introduce mass from the boundary layer in the form of a jet?
Me: I said, hmm well I’ve never studied that, but I’d imagine it adds turbulence and convection which makes it hard to model analytically so you’d need a simulation or something.
Interviewers: Ya this is basically an open-ended research question currently and is unknown. By the way, you go to school in the Bay Area, right? Let’s take this to the outdoors. Now imagine transpiration occurs from the water in the Bay up into the atmosphere, we have a strong wind coming in from the ocean front and this injected mass begins mixing with the incoming horizontal wind currents. This basically mimics what we just discussed; how would you model the climate in this case?
Me: I wasn’t quite sure what they were getting at here, so I just took it as a time to dump relevant knowledge. I said that I don’t know if it’s possible to model the full 2D or 3D case accurately by hand without a trusted simulation code on a Euclidean/Cartesian mesh with adaptive mesh refinement or something, but I do know how to do a simplified 1D atmospheric model accounting for radiative heat transfer, convection, latent heat transfer, and atmospheric absorption if you’d like? I do also know that Lorentz did attempt to model atmospheric currents and flows in 3D using coupled differential equations which is where the famous and pretty Lorentz attractors plots come from. This took ~20% of the interview.
Interviewers: Oh great, nice. I didn’t expect to go that far either. Interviewer A looks over to Interviewer B and says, “should we move to the frontiers?” Interviewer B says yes and hence we start the next part of the interview.
Q: What problem/frontier outside of your field are you most eager to explore?
Me: I had a feeling they’d ask me something similar based on what I read online so I had my 3 potential answers ready to go. I paused and said that I really think we’re on the cusp of discovering life on another planet. Not advanced life but microbial life, and I discussed the new James Webb Telescope and how literally within a month or so we had just detected the first evidence of photochemistry occurring on a planet outside of our solar system, a huge breakthrough and we’re just getting started. I mentioned how we are going to soon look at a high likelihood candidate for habitable worlds that could harbor life and NASA has missions to explore methane lakes inside of our solar system on other moons. I made sure to seed in that I think my research could play a role in this because the statistics I use had their start in a chemistry lab to study chirality in chemical compounds. My statistics detect odd-parity or handedness, this could be used to look for biochemical molecules that have chirality (I knew the biotech interviewer would love this). I threw out some possible ideas as to how, but I said I don’t know how to do this yet for sure, but it would be an interesting route to explore.
Interviewers: Cool, can you name another frontier?
Me: I talked about critical point physics studies in biochemistry and biophysics to study the brain. I found this cool video by Quanta Magazine discussing it (Click Here). I noticed they study phase transitions through correlation, aka a simpler version of the statistics I use in my research. I connected it to my work. I would like to explore this with the Ising Model and see if there is interesting information to be gained in the Ising Model in 3D and 2D with my research. One of my interviewers poked a whole in my train of thought and showed how I contradicted myself, but he said… “I’m not sure either though, so maybe you’re right or I don’t understand it enough yet.” I made sure to state that it is far out of my wheelhouse, but I find it interesting and a possible entry way into biophysics.
But… I did make sure to not end this thought on a down beat. I then said, “although I don’t know much about this one, I do think getting the Hertz fellowship would really allow me to break outside of the standard astrophysical path and I could work with researchers at institutes like the Flatiron Institute which encompasses Astro as well as other computational fields with experts in this topic that I could work with. They seemed to really like this statement; they wrote it down.
Interviewers: Okay, can you name one more?
Me: I mentioned biomedical imaging with convolutional neural networks to detect tumors quickly and reliably. Making a nod to my extracurricular work helping kids through and beyond a parent’s cancer as a part of the national organization Kesem. They liked this too. This section took ~20% of the interview.
Interviewers: Nice, let’s go back to depth quick, we have some pens and paper here for you. We’d like to see how you answer this question.
Q: If you were to double the distance from the Sun to the Earth, how would the temperature of Earth’s surface change?
Me: I gasped, I thought to myself (HELL YES, AN ASTRO QUESTION). This is a standard astrophysics question, so I was thankful to get this one. Walking them through the Stephan-Boltzmann Luminosity Law, then Flux distance law, then doing some blackbody/thermal emitter conservation of energy we get a factor of root 2 less, aka killing us all. I also mentioned that if we wanted, I could include an atmospheric model to complicate things, but they said that’s plenty. This took ~20% of the interview.
Interviewers: Great, any questions for us now?
Me: Asked the same question as last time, then asked if they had any advice for me who is just starting their career towards academia, and lastly asked if I could share this experience with others and post it online. They gave great answers and encouraged me to share my experience.
Interview Breakdown: • 20% Personal Background • 20% Research Discussion • 20% Depth Discussion • 20% Frontiers Discussion • 20% Technical Questions