You should check with an advisor on how your specific loans work. For many college loans for US students, payments do not have to start until the student is out of school, and this includes graduate school. Furthermore, for subsidized loans, where the government covers the interest while the student remains in school, that subsidy may continue during graduate school. In that case, until you leave graduate school, your college loan won't start accruing interest that you eventually need to pay.

The short answer is that dreams of future earnings aren't a great reason to start a PhD. If you don't enjoy the research itself, it will be hard if not impossible to keep yourself motivated through the long haul of a PhD program.

In the US, a Master's degree is not a prerequisite for most physics PhD programs. Most students go directly from a Bachelor's degree to a PhD program. Many earn a Master's degree during the first year or two, after they complete the coursework portion of the PhD.

Many other countries have a different system, which splits up the coursework and research portions of our PhD degree. Students first do graduate coursework and earn a Master's degree. Then they enroll for a PhD, which involves solely research and is often a fixed-time degree of 3 or 4 years.

The median time for a physics PhD in the US is about 6.5 years. That assumes the student has not gotten a Master's degree prior to enrolling in the PhD program.

You learn specialized technical skills, but more importantly you learn how to break apart and solve a very large problem. The ability to jump in and make progress on something complicated is why employers value physics PhDs. You can expect that your jobs after graduate school will be interesting; for rote jobs, employers hire BS degree holders instead. Most people also get a huge confidence boost from completing a PhD, and potential employers match that with their respect for the achievement.

As with much of life, grad school is what you make it. You will be surrounded by smart, dedicated people who share your interest in physics. Compared to college, you have much more freedom in choosing exactly how to spend your time. There are more courses offered than you'll be able to take. There are even far more one-off research talks than you can possibly attend, often more than half a dozen per week in the physics department with more in related departments like math, chemistry, materials science, computer science, and planetary science. Many grad students also socialize with each other through intramural sports teams, movie nights, and parties.

The other big transition for many students is getting used to research. You'll work on something where no one knows the answer, or how long it will take to find, or maybe even whether it can be found. Some students love the sense of possibility, while others find it disconcerting.

Most people find it very time-consuming, although if you love what you're doing it can also be exhilarating. For example, in the first year the coursework often takes about 40 hours per week -- sometimes more, since many grad students are perfectionist about their problem sets. On top of that, students often have 10-20 hours per week of teaching responsibilities, and they may be trying to start a trial research project. After the first year, the coursework dwindles while the research ramps up. If you choose an advisor who can pay you for doing your research, you can also cut back or eliminate the time spent on teaching; this will make juggling your responsibilities much easier.

No, this is a long-standing urban legend. Physics departments put a lot of work and money into training and financially supporting graduate students in their first couple of years. Faculty don't want to throw away that investment just before the students will start contributing to the research effort!

It's fine! Grad programs want you to be as sure as possible that grad school is right for you. Taking some time to explore options is often a good idea. The main problem is that if you take more than a year or two off, you may have to retake a few upper-level undergraduate physics courses to get yourself back up to speed. Many grad programs will allow this.

If you plan only one year off, you should think about applying to grad school during your senior year of college, then deferring your start date. Most grad programs allow this, and it means you won't have to worry about applications during your gap year.

Talk to the people writing letters of recommendation for you. They can help you judge where you have a good chance of acceptance, based on what they've seen with previous students. If you've already decided what subfield of physics to pursue, your recommenders may also have suggestions of schools strong in that area. On the other hand, if you aren't yet sure what research direction you'll take, you may want to look for schools with many options. Just as in making your final decision after you've been accepted, non-physics factors like weather, local nightlife, and proximity to family are also valid considerations.

No. Many schools ask about this, and students who do undergraduate research often have a good idea of what they like, at least whether they prefer experiment, computation, or analytical theory. However, in most physics graduate programs you aren't locked in to what you say on your application. (At Davis, about 25% of the Physics and Astronomy grad students wind up in a different area than they had expected when they applied.) A few schools do ask students to commit to a research advisor at the time they apply. If you haven't settled on a subfield, avoid applying to those places.

Most programs can make exceptions, so don't give up. If your grades have been improving over time and are above 3.0 for the past two years, some schools won't worry about earlier low grades. To save on application fees, ask the departments before you apply whether there could be an exception. Your application should show good evidence of persistence and research promise; otherwise, all things being equal, departments will take students with higher grades.

Another option is to wait a couple of years before applying to a PhD program. You could instead apply to a Masters program, many of which don't have a GPA cutoff. (Be careful regarding funding. Some Masters programs give tuition waivers and a stipend, much like PhD programs, but others do not.) PhD programs will then care more about your grades from the Masters degree than from college. Alternatively, if your GPA is only slightly below 3.0, you could spend a couple of years doing (paid) research at a national lab or with a university mentor. Getting a strong research letter could be enough to make your application stand out despite the lower grades.

First of all, many schools are not currently requiring or even accepting Physics GRE (P-GRE) scores. Some departments have misgivings about how well the exam predicts performance in graduate school. Others have temporarily eliminated the exam because COVID-19 may make it difficult for some applicants to take the test. Even in normal times, schools that claim to require the P-GRE may in fact allow exceptions. Similarly, schools that officially have a P-GRE cutoff score may not be entirely rigid about it for an otherwise very strong application. For American students, the P-GRE is one of several ways to check background physics knowledge. It's most important for those who had some low grades or attended small colleges. Even there, a score of 60th percentile is usually adequate.

Some schools are also currently waiving the general GRE exam, but that is less likely to last. For the quantitative section (Q-GRE), a high score won't help much but a low score can hurt your application. 70th percentile is often taken as a satisfactory score, but as always, an excellent research background can make up for a lower Q-GRE score. Some schools look positively on high verbal section scores, so it's worth paying attention to that portion too. The analytic writing section is not helpful though; at Davis we ignore those scores entirely in admissions.

You usually need three letters. A PhD is a research degree, so the most relevant letters will comment on your research experience and/or potential. If you've done research as an undergrad, ask your research advisor for a letter, even if the work wasn't in physics. (If you have at least two physics/astronomy research letters, you don't also need a letter from your advisor in a non-physics subject.) The letters don't need to be from your university; if you do an REU or an internship at a national lab, get a letter from that. If you have no research experience, talk to professors who know you well. Those who taught classes with open-ended assignments, such as independent studies or lab courses, may have a sense of how you'll approach a research question. Aim for instructors from upper-level courses if possible, with at most one letter from someone who knew you only from classes during your first two years of college.

If you've done research, describe the point of the work and your role in it. You should also get a recommendation from your research mentor, who will say more about what you did. Admissions committees would like to know how intellectually involved you were: did you have a sense of the big picture, or did you focus entirely on the day-to-day jobs you were assigned? Also comment on what you most liked (or disliked) about the research and how that influenced your plans for a research area in grad school.

Track the application to make sure all the pieces arrive, including your transcript and recommendations. Usually you can do this through the application web site. Remind your letter writers if the recommendations aren't there as the deadline draws near. Admissions committees may interpret an incomplete application as showing a lack of interest on your part.

Visit if you can. Many schools will pay your way. Talk to grad students as well as faculty. Are the students happy? Are there several professors you could see yourself working with? The next question explains how to compare the financial offers.

Beyond the schools themselves, what do you think of their locations? If you'll be there for six years or more, do you prefer an urban or more rural environment? If it's important to you, do you have family or friends nearby? Does the weather matter? That last may seem like a trivial consideration, but remember that if you like multiple schools and are having a lot of trouble deciding, there's a good chance that there is no wrong answer and you'll do fine at any of them.

Financial offers are often more similar than they appear at first glance. Start by confirming that your offer includes a waiver for all or nearly all of the tuition. Private schools may say their waiver has a value of $50,000 per year, while at public schools it can be much less. At UC Davis it's roughly $14,000 for California residents and $29,000 for out-of-state students. As far as your finances go, these numbers don't matter. It's money that the university charges and pays to itself. Ignore this portion when figuring out what your real financial offer is.

Next check how health insurance works. Some schools cover it as part of the tuition. Others pay for it but list the cost explicitly in the offer letter. Still others expect you to pay it from your stipend. It is a significant expense, about $5000 per year, so you need to know how it factors in before comparing stipends. If you need health insurance for dependents, ask the university whether you can add them and what that will cost you.

Now look at what you'll be paid, from teaching or research jobs and/or through fellowships. Subtract any tuition or health insurance costs that you're expected to pay yourself. Check whether this number will be your income for a full 12-month year or just for the 9-month academic year. If it's for 9 months, can you expect a teaching or research position over the summer too? (If the letter doesn't say, ask!) The offer letter usually outlines the finances for the first year of grad school. You should also check what will change after the first year. Usually in subsequent years you'll have teaching and research appointments that pay the same amount, but there is often a supplementary fellowship of $5000 or $10,000 in the first year, which may be a one-time occurrence.

At this point you should have a good idea of how your actual income will compare at different universities. You may next want to look at cost of living, especially typical rents, in areas near the schools. This can change the effective value of your stipend dramatically.

There is a good chance that once you finish this exercise, you'll find that the bottom line isn't all that different from one school to the next. In this case, as long as all the offers make grad school affordable, you should probably make your decision based on other factors.

Most programs will allow admitted students to defer for one year. Starting outside of fall term may not be possible, since the series of classes at the beginning of the graduate program starts in fall. This may depend on the grad program and on your specific circumstances, so definitely ask what your options are once you've been admitted.