For the universities that I am most familiar with (mostly in the U.S.) there is no undergraduate theoretical physics major or undergraduate experimental physics major. Nor should there be. There is only a physics major. It should give balanced exposure to both mathematical and laboratory work, resulting in a well-rounded bachelor’s degree instead of narrowly specialized training.

(And anybody who isn’t working at least on a master’s degree yet claims that they’re “studying theoretical physics” is really just a physics student trying to sound more advanced than they are.)

In the junior and senior undergraduate years, there is some flexibility to take a few electives that might be more mathematical or more experimental in their focus. But elective choice is not as significant as it first appears. A career in physics means continuing on to graduate school - To be accepted to work with a good advisor in a strong graduate program, what matters most is how well you do in a quality, highly-ranked undergraduate program, what recommendations you earn from faculty you work with, and how high you score on the GRE. Details of which electives you picked won’t matter a lot.

One exception is that a few schools offer a physics major and an applied physics major. At the undergraduate level, that’s a more meaningful distinction than theoretical vs. experimental.

For employment after earning a Ph.D., there simply aren’t enough academic jobs. A lot of Ph.D. physicists will need to find employment in industry or government even if their goal was a university research position. Tenure-track professorships in physics are extremely competitive, and a lot of excellent people don’t get them. The odds might be a little better for an experimental scientist able to bring in a lot of grant money. Odds are also a little higher if you have sophisticated computer coding skills on top of your mathematical and physics knowledge. But for the effort required, you should pick what you’re best at and are most interested in, as choosing a Ph.D. just for the best job odds is a path to burnout.

All preoccupations of physicists are channeled towards the investigation and study of the physical properties of the universe; the interactions and interrelations of matter and energy at different scales - from atomic scale (Quantum Physics), human scale (Classical Physics) and cosmic scale (Cosmology & Astrophysics).

Theoretical Physicists spend their time, energy and resources to conceive and develop models (*usually conceptual, philosophical and thoroughly mathematical) in order to describe observable or non-observable physical phenomena and also the laws governing the interactions and interrelations of matter and energy at all scales.

Experimental Physicists on the other hand spend their time, energy and equipment (resources) performing tests and experimentation on models and theories. Experimental Physicists could be very practical in the sense that they are more inclined to become Engineers using physical principles, laws and models to invent technologies - of the present and of the future.

Both Theoretical and Experimental Physics seem like imperatives for investigating the universe or studying physics. They are the Yin and Yang of the discipline.

As regards physics as a profession, the job responsibilities separates both imperatives. The professional responsibility of a Theoretical Physicist include:

• Building conceptual models of the physical properties of the complex universe (through Thought Experiments mostly)
• Making mathematical analyses and predictions about these ‘concepts’ relating to the complex phenomena we experience and observe.
• Writing papers and debating about right or wrong theories like Bohr–Einstein debates (This is so cool, it made me fall in love with Theoretical Physics)

The professional responsibility of an Experimental Physicist include:

• Testing the models and theories made by Theoretical Physicist (* just like those guys who tested Einstein’s hypothesis about the quantum world — quantum entanglement, spooky actions, and the ‘to be or not to be’ scenario)
• Developing ways to use the properties of matter and energy in industry applications (very cool)
• The models created by Theoretical Physicists needs data - lots of them - hence, Experimental Physicists observe, record and analyze data for the efficiency and utility of the models.

I wish I was a real Physicist

Footnotes:

1. Difference Between Theoretical & Experimental Physicist
2. Bohr–Einstein debates - Wikipedia

What gets you excited more? The idea of working with exciting ideas, concepts, and equations, or working with exciting gadgets and machines? Of course there will be overlap of the two, but you should have idea of which one really gets you going. I'm assuming that you care more about doing exciting work than making money. Every physicist I ever met is entirely driven by passion for the subject rather than anything else.

To elaborate a bit more on the differences- A theoretical physicists goal is to consider all of the data and other observations which experimental physicists have provided along with all of the inconsistencies in current theory and try to build new models or come up with new mechanisms to explain these. They also will spend lots of time drawing current theories to their logical conclusions and working out all of the implications for caveats of our current models which haven't been explored.

Experimental folks will spend lots of time performing experiments, taking measurement and doing TONS of statistical analysis to determine what exactly they measured, how confident they are that it was an actual measurement and not a random fluctuation, whether these results are what we expect, etc. they think about what factors might be causing inaccuracies and how to deal with these. They are often to ones to say we have strong reason to believe that a current physics theory must be wrong due to experimental results not matching up with what the theorists have predicted even after all of the interfering factors have been accounted for.

I tend to sympathize wkth the theorists. Nothing makes me happier than a whiteboard and lots of free time to think :)

An experimentalist will devise experiments and perform them. They will make measurements, annotate them into their notebooks.

They will search in the literature which is the best model to describe the observations and fit them to it, extracting the parameters.

These parameters have meanings implicit in the model, which was devised by a theoretical physicist.

For example, let's consider a Raman spectroscopy experiment, where we measure the interaction between light and a molecule in solution.

The interaction between light and the molecule would occur far from their absorption lines.

Figure 1 – Jablonski diagram showing the transition of energy for Rayleigh and Raman scattering.

The virtual states are there just to represent the non-resonant interaction. They are in the gap (energies below the absorption line).

There you can see the Stokes, anti-Stokes, and Rayleigh Raman scattering.,

The Stokes line will have the energy of the laser (excitation) minus one vibrational quantum. The anti-Stokes line will be at laser plus one vibrational quantum. Since that line depends upon the vibrational population on the lower electronic state, it will be sensitive to temperature.

The Rayleigh line is just elastic scattering.

Also shown in the figure are actual absorption and fluorescence lines. Absorption is followed by radiationless transitions to the bottom of the excited state manifold. Only then fluorescence occurs.

This means that the inelastic light scattering would be the result of the interaction of the light with the susceptibility associated with the molecule.

Since that susceptibility (polarizability) depends upon exactly where all the atoms are located relative to each other, the interaction will contain information about vibrational frequencies.

The peaks are related to molecular vibrations.

The interpretation (the extraction of molecular bonds, couplings to the surroundings) is done using the theoretical framework worked out by theoreticians.

You try to put your hands on both. I've been trying to write my theses and to do internships in between on both sides, about both cosmology and particle physics. At the end, I think I might end up doing my PhD somewhere in the middle, phenomenological. So, the point is you never know what you're really into and you're really good at unless you try. You shall realize, I guess, only one side can give you the chill to your bones when you're working on it, only one side can offer you enough of comfort to get you through your long PhD days and only one side you can give it your all. Of course, I'm not talking about people like Enrico Fermi, who worked and achieved tremendous successes on both sides.

You will need a good grounding in mathematics, if you are not prepared to take that on you will be limited in your understanding of the theory. Some of the problems can only be understood through the mathematics. I thought that I had a reasonable grounding at sixth form level but found the University level much more difficult and didn't devote my time fully to understand it. You might think that of the two,

experimental physics might be the better bet if your maths wasn't up to it, but in the end you do need a good understanding of the maths. If you read most of the answers on the physics problems either on the net or via Quora you will understand what I mean. This is particularly true when you are faced with Quantum Theory. It takes a Richard Feynman to explain the higher physics and even he said no one understands Quantum Theory!

I’ll provide an anecdote to stir the pot some.

One of my professors was experimentally determining the wave function of electrons in diatomic molecules, measuring scatter off of photons (?maybe electrons it was in the mid 70’s) off of single molecules in an extreme vacuum setup. A theoretician proved that his plots couldn’t possibly be valid, that uncertainty precluded getting the precision and repeatability that he demonstrated.

It is quite possible that both had errors in their work, but the experimentalist produced data useful for chemical engineering. For many of us utility is a major criterion in determining the validity of a theory.

I am not a physicist. I think you have good responses here from qualified professionals. However, I will point out to you that which others will not do. Experimental physics gives us the empirical evidence that we need to understand the universe. However, theoretical physics does this only partly. Theoretical physics is a mathematical playground in which guesses are allowed. Popular guesses even become established parts of physics equations. Probably the worst scientific choice made was that the nature of the universe could be analyzed from a mechanical perspective. This universe produced us. We are the means by which it now comprehends itself. It communicates to us through empirical evidence. The evidence is all around us. Between what physicists know and what the rest of us observe; this universe is an orderly, unified, example of how intelligent life comes to be. Theoretical physics is nether unified nor does it predict or explain the existence of life or intelligence.

Experimentalists perform experiments to test the theories of theorists. Sometimes experimentalists perform experiments that test out their own theories too. Theoretical physics is the deriving of the theories of the how the world works and experimental physics is the performing the experiments to test how the world works.

There is also computational physics, which is usually mixed in with theorerical physics, but it is really a bit different. After one has a theory, one may have a very complicated equation that predicts the way the world works. However, some one needs to be able to figure out how to perform the computation to get real values that are predicted by the equation. Computational physics could be thought of as numerical analysis applied specifically to physics.

I’m reaching the end of a double master’s degree in engineering physics and theoretical physics so I hope I can give you a good answer…

The main difference is basically the kind of questions you ask yourself, so if you don’t know which way to go, you have to think about what turns you on the most…

1. If you love understanding how devices work, and based on what principles, and how they are used in order to get what you want, then applied physics is probably the best way to go.
2. If you love asking questions about how our physical theories are founded, how is it legitimate to use a certain assumption about reality and how the mathematical translation is correct, then maybe theoretical physics suits you better.

For example, when you are taking a shower, what would you most probably spontaneously ask yourself :

1. At what speed would the water flow out of a punctured bottle ? What is the furthest I can see a candle in complete darkness ?
2. Can a photon really only interact with itself ? Do physical properties of a system exist prior to a measurement ?

Though both applied and theoretical physics require you to have a passion for solving problems, I have met very smart people who really don’t see the point in asking philosophical questions, and also smart people who really get bored when the topic is too specific to a certain application or device.

I believe they attract different kinds of problem solvers :

1. Applied physics attract problem solvers who are amazed by how useful and efficient something can be, and how to build up complex things from simple fundamental rules.
2. Theoretical physics appeals problem solvers who, in my opinion, are addicted to the beauty of finding, expressing and understanding general rules that govern the whole universe that take a pristinely simple form in the mathematical language.

In my case, I was a bit of both, though in my undergrad the main subject was pure mathematics.

I did want to enjoy doing things that had an immediate practical use.

Applied physics really asks the real questions, the models are often complex and you need numerical methods to solve your equations.

Theoretical physics asks the tough questions, the models are less complex but more sophisticated.

After two years of engineering physics, I really missed studying concepts that would encompass more situations. Like “consider a spacetime in which…” rather than “consider a lens of focal length…”.

Oh, and of course, you will have different kind of maths in theoretical physics (variational calculus, group theory, complex analysis, tensor calculus, differential geometry) than in applied physics (more statistics, regression optimization, 3D geometry), even though some of the maths used in both topics do overlap.

But maybe more than the mathematical concepts, it’s the way of doing maths that will not be the same. In theoretical physics, you need to understand what you do, not as deeply as the mathematician, but certainly in a less “utilitarian” way than for the applied physicist.

As for the jobs…obviously, there are more industrial applications for an applied physicist who knows how to deal with the purification of a laser beam, than for a theoretical physicist who knows that all future pointing timelike worldlines or null geodesics converge to the singularity once the event horizon is crossed.

Anyway, both are incredibly rich and demanding, in their own ways. But perhaps as far as your career prospects are concerned, applied physics would be less restrictive than theoretical physics.

Yes.

Either one would be catastrophically weakened by the absence of the other, but what it comes down to is this: without experiment/observation, there is no science. Without experimentalists, theorists would have pretty much nothing to go on. That makes a pretty big difference, e.g., the difference between Aristotle and Newton. Guess whose theories work better?

Experimentalists also make tremendous use of theoretical results. Most of physics post 1900 or so would be a complete shambles without theorists, and an awful lot of modern technology wouldn’t exist. But, they’d still know something. Technology-wise, we’d still have modern bridges, and skyscrapers, and cars — they just wouldn’t work as well, and progress would be slower.

To put it another way: if you already have a bunch of theorists, but no/few experimentalists, you would desperately want more experimentalists. If you already have a bunch of experimentalists, but no/few theorists, you would desperately want more theorists. But if, for some bizarre reason, all physicists had to be in the same category, you’d want them to be experimentalists.

Within a physics department, if you are a theorist, and your primary daily tool is a whiteboard or your head, and your papers are mostly equations, then you are a “mathematical theorist/physicist”. You get your salary paid from either teaching classes, or by writing grant proposals that pay your university salary for you so you don’t have to teach as often. If your tools are primarily computers, perhaps with some pencil and paper equations and other “analog” work, you would be a “numerical theorist”. In that case you write grants and permission requests to use supercomputers at other locations, or purchase clusters of workstations for your group or supercomputers for your department. If you have a considerable mix of computer work, “analog” work, etc, like someone who works on density functional theory, you would definitely be a “theorist”, but people would not consider you a “mathematical theorist”. You might write a mixture of grant proposals to pay for your time and possibly supercomputer time/workstation hardware.

Typical mathematical physicists are: String Theorists like Joe Polchinski or John Schwartz, Field Theorists like Steve Giddings or David Gross, Theoretical Cosmologists/Astrophysicists that study spacetime geometry like Kip Thorne or Steven Hawking. Typical numerical physicists are: Theoretical Astrophysicists that study galaxies and star formation or compact objects like Omer Blaes. Typical other mixed theorists might be other types of materials scientists like Walter Kohn or Leon Balents.

As an aside, other forms of physicists:

If you mostly use telescopes or equipment that someone else made, like writing grant proposals and permission requests from the government to getting time on the Hubble Space Telescope, then you would be an “observationalist”. If you specialize in building a new Hubble Space Telescope, (and being the first to use it and write papers from it since you wrote the grant proposal, led a team that designed it from scratch, and are the PI for it, likely agreeing to allow others to use it after your initial time period where you get exclusive rights), then you would be an “instrumentalist”. If you mostly work in your lab and tinker with custom setups and novel materials that you write individual smaller grants for, you would be an “experimentalist”. Note an experimentalist may consider any of the theorist classes above as being “pure theorists” with less distinction between them. People in this experimentalist group would be considered “pure experimentalists” by people in the theory class, with less distinction.

In high school, I profoundly disliked the (minimal) lab components of my physics and chemistry classes. Given the option between plugging numbers into a simple formula, or struggling to keep a recalcitrant lab partner on task long enough to slide a toy car down an inclined track on a lab bench, the preference towards theory was obvious.

During my freshman year of college, the lab classes were less rudimentary and my lab partners were infinitely more capable. We started to incorporate ‘real’ equipment, such as Geiger counters and interferometers into the labs, which actually clarified classroom concepts. Starting my sophomore year, I started to do research with an experimental condensed matter physicist. This, coupled with the content of my classes becoming more sophisticated, created a situation where my ‘practical’ experience gave me intuition to understand classroom concepts, rather than the other way around. When we learned scattering theory in quantum mechanics, I had already been doing that same thing with neutrons for a year. When we derived paramagnetic susceptibility in statistical mechanics class, I had already seen this using a SQuID magnetometer many times.

I did not even consider being a theorist after my freshman year of college because of my positive experiences working in an experimental research lab, the positive feedback loop between my research, courses, and lab courses, and the relatively uninspiring experience I had in my college math classes. The path I chose turned out to be most lucrative from the standpoint of finding research opportunities as an undergraduate and finding a faculty position 10 years later (see: Inna Vishik's answer to Which fields of physics have a demand for more experimental physicists?), but this pragmatism never entered into my initial decision making process.

I built model airplanes as a kid (not the plastic kind; I’d go buy a couple sheets of balsa wood and sculpt them into my own designs, meant to fly well) so I had originally planned to become an aeronautical engineer. Then I read a few hundred science fiction books and decided physics was for me. (This was in the era when space operas and weird science dominated the genre.) Then there were a couple other reimaginings (poet, philosopher…) and I found myself going to grad school to get a PhD in Physics in order to gain credibility as a SF writer. At Berkeley I found out I was not smart or disciplined enough to be a theorist, and in any case they don’t get to build stuff — so there was no real choice after that; but I also got lucky with a thesis topic that (a) was like a SF story and (b) was just at the taking-off point as a new research tool. I got my degree in 1972 and am still trying to kick-start my SF career….

I bet that’s no help at all. :-)

Theoretical physicists tend to have higher math IQs, and experimental physicists tend to be far more creative in crafting ways to get nature to answer the questions of the theorists.

Ernest Rutherford was amazing at putting together experiments and should have received at least two Nobel Prizes for his work, but he struggled to do the math that eventually showed that his scattering experiment indicated the existence of a small dense nucleus in atoms.

There are many stories of famous theorists who were forced into some degree of experimental work as graduate students and almost didn't make it because of their poor skills with equipment.

The world of physics needs both types, and there is even a third classification known as machine builders.

My 13 page hardcopy composition is an empirical confirmation of the 11 Dimensional String Theory derived by Professor Michio Kaku. It is available to those of you interested by mailing me $20 so I can pay for USA postage and handling to the return mailing address that you provide me at :

James Nassir

P. O. Box 3243

Cypress, CA 90630

My Empirical Confirmation of the 11 Dimensional String Theory of Professor Michio Kaku, and My Case for the Existence of 5 Dimensional Atmospheric Entities (AE) is copyrighted and does solve the 70 year mystery of UFO, now named UAP.

It documents the following: (1) My Dec 1977 Discovery of the 5th Force which provides evidence of Supersymmetry of StringTheory, (2) My Perilous Flight on a Boeing Jet Airliner which gives evidence of String Field Theory of Professor Michio Kaku, (3) My two encounters with 5 Dimensional Atmospheric Entities, one of which in the presence of my brilliant PhD Brother-In-Law who exclaimed I cannot explain what I just saw!, (4) my voluminous credentials describing my engineering work leading to 4 patents.

Sincerely, James Edward Nassir, April 1, 2023

“Since the mathematicians have invaded the theory of relativity I do not understand it myself any more.” — Albert Einstein (1949)

I think Einstein was being a bit facetious in this quote, but it illustrates a difference in theoretical physics and mathematical physics. Einstein was clearly a theoretical physicist. There were numerous mathematicians, such as Elie Cartan and Hermann Weyl who applied mathematical methods, the theory of moving frames, in the case of Cartan, and the vierbein by Weyl, to the theory. Perhaps that is, in part, what Einstein was referring to in the quote above. The contributions of Cartan and Weyl could be considered mathematical physics, in other words, mathematical methods applied to physics.

Another illustration of the difference of the two fields would include the discoverers of quantum mechanics, Schrodinger and Heisenberg, and those, John von Neumann in particular who’s work provided a rigorous treatment of the subject in the arena of Hilbert space theory. The former were theoretical physicists, and the latter a mathematician contributing to the understanding of quantum mechanics.

It is not unusual for theoretical physicists to introduce mathematical concepts based on intuition or need, examples are the Dirac delta function and the Feynman path integral, and for these ideas to catch the attention of mathematicians who become interested in making those ideas mathematically rigorous. That has been part of the interplay between physics and mathematics since at least the time of Isaac Newton.

So, my characterization of the difference in the two fields is that theoretical physics endeavors to produce mathematical models to explain physical phenomena. By contrast, mathematical physics is concerned with mathematical methods used in physics to solve problems or formulate theories.

Mathematical physics - Wikipedia

I did a bit of both as a student. During college, I worked with an experimental group on radiation physics research with astrophysical implications. In graduate school, I did theoretical condensed matter physics and then theoretical particle physics. In the end, I just fell in love with the mathematical underpinnings of theoretical particle physics and stayed in that field.

It would have been more practical to stay in condensed matter research, I supposed, since there are options to work in industry or move toward applied physics to some extent. But I just really liked what I was studying in particle physics and decided to follow that pathway.

An experimental physicist is an electrician/plumber on the side, while a theoretical physicist is a mathematician/computer scientist on the side.

Most of the domain specific knowledge for experimental physics comes from working in a research lab, not by taking a class about it. Yes, there are sometimes classes (or lab courses) about a specific experimental technique, but it is not a good use of one's time (unless it's required) if you never use that experimental technique. There are also many physics, math, and CS classes that are helpful for physicists, but this is not specific to experimental physics. It should be noted that the background knowledge you need will depend very much on the subfield in which you want to specialize, which is all the more reason to get your feet wet with real research as early as possible if you want to be a physicist when you grow up.

A boy born in Newington Butts(now part of London borough of Southwark).His family was not well off and he was third of four children. He had the most basic school education (i.e. He was able to distinguish between alphabets and read them)
When he was fourteen, he became the apprentice to George Riebau, a local bookbinder and book seller in Blandford street. During his apprenticeship he read many books like Isaac Watts' The Improvement of Mind etc. And he developed interest in SCIENCE, especially in electricity.
At age of twenty, he ended apprenticeship and attended lectures of Humphry Davy who was member of Royal Institution and Royal society. So the boy sent Davy a three-hundred page book based on notes that he had taken during these lectures. Davy was impressed and employed him as an assistant which ignited the love for science in him.
His work in both chemistry and physics was remarkable.
FOR CHEMISTRY:
(I) He gave the Laws of electrolysis;
(II)terminologies like Anode, cathode, electrode and Ion;
(III) optical properties of gold colloids; (IV)He invented early form of Bunsen Burner ;
(V) He discovered Benzene (which he called 'Bicarburet of Hydrogen');
(VI)Liquefying gases(chlorine);
(VII)First synthesis of compound of carbon and chlorine( C2Cl6, C2Cl4);
(VIII) He also continued metallic nanoparticles.
FOR PHYSICS:
According to me he is the best experimental physicist
(I) Electricity And Magnetism;(II)Diamagnetism;
(III) Static electricity;
(IV) Induction.
And many more

He just had love for science. And that love made helped him to reach pinnacle.
He died at the age of 75 in the year 1867.
-MICHAEL FARADAY(1791-1867)
Now, coming to your question
Yes, you should go for it.
You will enjoy physics.

There are a lot of peculiarities regarding specific fields, but the most importance difference I can recognize universally is that Theory is bottom-up, Experiment is top-down.

There are two parts to an experiment: the performing and the analysis. The performing varies greatly from field to field, but the common thing is that once performed the experiment, the result is full of everything, is (if you did things properly) the truth.
Then, you have to analyse the total truth to strip down the content into meaning, going from sheer number(s) to the thing you are experimenting about and you want to demonstrate. This process is like peeling an onion: you remove obvious and omni-present background sources, you remove less obvious and specific background you can think of, you search in a specific scale what you want to find, navigating gauging yourself on other things you know...etc...
You have to undress the truth to reach its core.

With theories you have your field-dependent technicality, but the core result is that you have your ideal naked world and you have to dress it (fill it with fields, interactions, particles, ideas...etc...) to find out the thing you want. You start from blank slate, and populate your world with the less components you can imagine that give the effect you want to see.

To prepare to be an experimentalist really depends on your field. Could be that you need on-the-field expertise, or statistical (never a bad idea in these days in any case), electronics or optics...etc...

If you ask from the day to day depends a lot on your field. There are fields where the experimentalist analyse data for years, thus making the work very solitary, math and computationally driven, except for the few weeks of shifts needed for the next bunch of data. There are theories which require a very coral effort and frequent meetings and maybe not so many hours on the computer.

Generally speaking tough, theory is a more solitary work, more sedentary, more filled with quirkiness. When I was doing experiments there was lot more drinking and fooling around involved... or maybe I was just younger... ;)

If you want to become a theoretical physicist, then pursue a PhD in mathematics. Getting your PhD in theoretical physics will require a lot of math. Unfortunately, the modern theoretical physicist is too much of a generalist. Theoretical physics needs specialists who are able to connect the dots of established physics, not invent or reinforce speculations while ignoring the more intimate details of physics.

IMO, the degree in mathematics is the way to go for theoretical physics simply because you won’t be so foolish as to think you already understand without bothering to look it up and research it in depth. That is the big problem I see with people getting degrees in physics. They think they know it all, but really they know what they work on and the popular versions of other things.

They then fail to look up and dig deep into the details. They end up reinforcing speculative thinking that diverges from established physics. In a sense, their understanding of physics becomes an enhanced form of the average person’s Google search. I’m sorry, but particle physics has many areas of expertise, and each PhD in high energy physics has its own specialization. That is what you understand best. The rest you need to accept as things you don’t actually understand so well. Listen to those experts just like a gynecologist will listen to a heart surgeon or neurosurgeon.

I see a lot of pretending to understand without any actual depth of comprehension. Depth of comprehension requires decades of hands-on research. Even then, you know only what you’ve done. Don’t make more of it. Quit pretending you understand neutrinos when your knowledge of them shows you don’t even comprehend Gauge theory to see neutrinos are perturbations. Quit pretending you understand CMB when you clearly show no comprehension of the d’Alembertian, spherical wavefronts, or monopolar behaviors such that non-propagating heat is a static local volume (background temperature).

I have a lot of bones to pick with theoretical physicists. Theoretical physicists should be focused on one of three things:

1. Writing good science fiction that inspires people to study science.
2. Finding ways to make complex physics concepts accessible to students and the public.
3. Coordinating observed facts into working algorithms that make testable predictions (what theory actually is).

If all you do is lip service to speculations like Big Bang, you are not contributing to physics at all. You are contributing to a speculation. Never put the theory first. Always follow the scientific method. If you can’t reproduce it here on Earth, you can’t test it. You can’t prove or disprove it. It is speculation. Speculation is not evidence. Speculation agreeing with other speculation is also not evidence. Doing these things undermines the integrity of ALL of science. If you aren’t going to do it right, please do something else.

Where you get your degrees only matters if you need a very specific line of guidance. Generally speaking, an education is what you put into it. You will take the same classes everywhere. Some places will have better contacts for getting into particular aspects of the field. That alone is often a good reason to choose one place over another. If you are simply following the scientific method to understand how the universe works, then find a school that will enable you to do that. And most likely that would look like a PhD in applied mathematics if you are serious about contributing to theoretical physics.

I have known and worked with a number of condensed matter experimentalists who were theorists in a past life, so lack of experimental experience by itself is not a deal breaker. In fact, expertise in theory or modeling is a positive asset that will make you extremely valuable in an experimental group.
That being said, you might face difficulty because your experience is in a very different field from condensed matter experiment (and different from many traditional physics disciplines). It might take extra work to convince people, but I think it can be done because you do have a physics degree. Here is my general advice.

• Learn basic solid state physics (Kittel level is fine)
• If you haven't applied for grad school yet, apply to programs which admit people to the department as a whole, rather than admit them to work for a specific professor. Most programs in the US are like that. You might want to select a department which has strong research in non-linear dynamics, which is the physics discipline closest to your experience (some subfields of biophysics and some niches in astrophysics also study related topics). Sell yourself as a specialist in a given topic, and show your true colors when you are admitted (many people do this). But make sure the university has people in your chosen field too.
• When you do get admitted, try to find a PhD advisor who does both experiments and numerical simulations. If one cannot be found, you can still sell your numerical expertise as an asset (which it absolutely is).
• Read about current research in your chosen field. If you don't have journal subscriptions through a university, read arXiv mesoscale and Nanoscale Physics. This will show prospective advisers that you understand the field, and it will also help you ascertain if you really want to go into this field.