But to actually come up with the theories and to derive the laws of nature seems far more rewarding then the one who counts the electrons on a screen.
That's not how things work, but I'm not sure whether you care how things really work.

I have a doctorate in theoretical astrophysics, and frankly you don't have any clue what you are talking about here.
Being able to say that line alone must make the Ph.D worth it, even without the cushy Wall Street job.

G01
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To really answer the question we have to briefly examine what science is. Science consists of two main parts. 1. We observe the world around us. 2. We try to explain those observations and make predictions based off of those explanations. These predictions are then verified by more observations. And so on and so forth. Experiment covers the first part, theory the second. Then we loop back to experiment and the process starts over.

The main point in all of this is that science is, in the end, an inductive form of logic. We start with an assumption (meaning a statement that is not proven true using only the rules of logic). Our assumption is that the initial trend or pattern we observe in nature is true. From that assumption, we then build a model or theory and make predictions.

An example is probably a good idea about now. Let's call out scientist "Newton" :

1. Assumption: Newton's observes that F=MA (This is an assumption because we cannot mathematically prove that F=MA. It is an observation.)

2. Theory: Newton then devises a theory explaining the motion of objects including planets around the sun, balls on inclines, etc. He predicts the periods of planetary orbits.

3. These predictions are backed up by observations of the planetary orbits, giving evidence that our initial assumption is true, and not just something we make up.

In short, ideally, science is an inductive system of logic. The initial inductive statement is supported by the scientific method.

The is different than pure mathematics, which is a deductive system of logic. There is no initial statement in the argument that is assumed to be true. All mathematical proofs start only by assuming the fundamental rules of logic agreed upon by all.

So, in science, theory and experiment are equally important! It is not science unless both are happening. With only one or the other, a crucial step is left out of the argument. Without experiment, theory has no way to verify the initial inductive statement, and thus the argument fails entirely. Without theory, we are not able to link together observations in a coherent manner.

I have to get back to work now, but more on what actual experimental and theoretical physicists do in my next post.

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Erebus_Oneiros
G01
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So, now to answer what real theorists and experimentalists are like:

Just to give you some background on where this answer comes from: I am a Ph.D. student in physics, about to finish my Masters in Physics. I spend all day, every day surrounded by physicists, experiment and theory, so I think I can at least give an overview of what each discipline is like. Personally, I am an experimentalist.

Any real physicists, in either discipline, needs to have an understanding of the other. The Theorists in the high energy group in my department spend a lot of their time talking about what we will see in the LHC. In order to do this they need to know how particles are detected at the LHC. They don't need to be able to put together the ATLAS detector from memory, but they have to be familiar with the experimental methods, otherwise, they can't really give any productive insight into what new discoveries will look like.

On the opposite side of the coin, a good experimentalist must have an understanding of theory. A high energy experimentalist has to be well versed in Quantum Field Theory. If they don't understand how elementary particles will scatter, how will they ever be able to design good detectors? Thus, to imply that experimentalists are essentially monkeys with wrenches "counting electrons on a screen" is just plain wrong, not to mention insulting.

Now what skills will one develop when they become a theorist:

Obviously, being good at math is important, but there is much more to real theoretical work. You will most likely not be working with the fundamental equations of the universe! You'll have to learn approximation methods, which is arguably not the most interesting thing one learns in theory! You'll have to be able to use perturbation methods is all fields. In condensed matter theory, you'll spend time learning approximation methods like Hartree-Fock, density functional theory, etc. etc.

You will have to learn numerical and computational methods to help you produce results. Few non practicing theorists realize how important computers are to modern science. Whether you are doing simulations of protein folding or Lattice QCD, computers are essential to modern day theoretical work. Expect to spend a lot of time learning computational methods as a theorist.

It's not all cups of tea and blackboards!

What skills do experimentalists need?

Experiments that involve a person physically counting dots on a screen do not exist is modern day physics. Anyone who says that that is what goes on in a real physics lab might as well be saying that experimentalists spend their days rolling carts down ramps and measuring g over and over again!

Many experiments involve lots of automation. Expect to learn how to interface devices (oscilloscopes, lock in amplifiers, motion controllers, laser oscillators) with computers. You will also get very good at programming in experiment!

Chances are you will need to build many of the components for your experiment yourself! No one has done that experiment before, why should anyone sell the stuff you need? It's quite possible that you'll need to take a machine shop class along with that quantum field theory course next semester!

You've worked through all the theory from QED and understand how stimulated and spontaneous emission arise from the quantization of the electromagnetic field? (You will do this in a graduate quantum course, regardless of discipline.) That's great, but can you build a laser cavity and tweak the mirrors such that you get your oscillator to mode lock so you can get the femtosecond pulses you need? You will need to be able to understand how real lasers work. Trust me, it goes way beyond stimulated and spontaneous emission!

Also, I won't lie, expect to do some grunt work! Can you replace piping or a water pump when a cooling system breaks down? Effectively transfer liquid helium? How about soldering? Designing circuits?

Experimentalists learn WAY more than just Quantum Mechanics and E&M in grad school! Some of the experimentalists I have met are they most mathematically able people I know, and they are also some of the most well rounded, capable people I've ever met!

The moral is that both experiment and theory require much more than physics lectures imply! It's hard work, but very rewarding if you enjoy it!

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Erebus_Oneiros
Thanks for the very detailed answer G01. I was wondering about the differences myself.

G01
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Career Options

The general rule of thumb is that there is more money available for experimental or applied work. This is just the way the world is. In an ideal world, both theory and experiment would have as much money as they needed, but the world is just not perfect.

Usually this means it is a bit easier for experimental students to get funded RA's. The theory students I know have spent more time teaching in grad school to make up for this.

Also, you can argue that experimentalists usually have more job options since they have experience that companies outside of academia seek. (Not to say that theorists don't, but knowing how to design circuits and service lasers won't hurt your chances of getting a job in industry.)

That said, you should do what you enjoy the most! Neither experiment or theory will make you rich.

Conclusion

I hope this has helped clarify what experimental and theoretical physicists do. It's not a complete answer, and the only way to truly figure it out is to study physics and get an internship in a research group. I encourage any physics undergrad to get some research experience before you graduate. It can really help you determine your future career prospects.

I know at times it may have sounded like an apologetic for experimentalists. Forgive me, but I had to defend my discipline just a bit given the things said about experimentalists in this thread. Speaking of which:

One final note to Philosopher_k

In my experience, there is one unspoken rule in the culture of physics: "If you don't know what your talking about, don't say anything! Instead, listen and learn." Physicists really respect people who know how much they don't know. Physicists have very little patience for those who pretend to know things they don't. And in this field, it is easy to tell apart those who know their stuff, and those who don't. So, you are going to need to change your attitude/approach if you really intend to become a physicist.

Please don't make assumptions about what experimentalists or theorists do. You don't know. You are neither, and I doubt you know many at this stage of your life. No actual theorist worth their salt would ever claim that experimentalists don't understand physics theory and need it "dumbed down" for them. That is an absurd statement! You're a high school student! How can you possibly know what either type of physicist studies in their second year of undergraduate work, let alone in grad school?!

Theorists respect their experimental colleagues, and vice versa. If you really want to be a physicist, you'll need to grow up and change your attitude.

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Erebus_Oneiros
Despite what anyone claims i believe theorists are by far more important that experimentalists. Theory lets you UNDERSTAND the deepest ideas in the universe. Experiment is only important in that it tests out theories and allows us to whittle them down. For the true beauty of physics you should become a theorist.

You need quite a lot of talent to become a theoretical physicist. Experimental physics is for those less talented. I am not a theorist yet, but i believe i have a spark of the talent required for it.

Just make sure you go into theoretical physics, if you can, everything else is stamp collecting.
Why are you giving this advice when you're still in high school?

As far as i am concerned mathematics far outshines any form of physics. Be it theoretical or experimental.

Being able to say that line alone must make the Ph.D worth it, even without the cushy Wall Street job.
Well, personally I think that argument from authority is non-sense. I may have a Ph.D. in astrophysics theory, but I'm totally clueless about certain things, and even on the things I know something about, I'm often wrong.

This is why it's really important to be humble about what you know and what you don't.

As far as i am concerned mathematics far outshines any form of physics. Be it theoretical or experimental.
You might try to figure out *why* you think this. One place to start is figuring this out is to look at your parents and the people close to you to see what they believe. Once you get there, you can figure out why they believe what they believe, and then go into a historical detective story to figure out where all that came from. I'm pretty sure you'll find yourself in Plato's Republic.

Plato expounded a theory of politics and philosophy that has been highly influential over the last two thousand years. In the Republic, he outlines a society with philosopher-kings and elevates math to the highest truth with everything derived from that. As far as I'm concerned its total non-sense, but Plato is required reading because you can figure out where the non-sense came from. Also Aristotle is required reading since I think that Aristotle got things closer to the right answer.

As far as why it's non-sense. Hierarchical social systems are wonderful if you are at top or you think you are going be at the top. They totally suck once you figure out that you aren't going to make it.

Well, personally I think that argument from authority is non-sense. I may have a Ph.D. in astrophysics theory, but I'm totally clueless about certain things, and even on the things I know something about, I'm often wrong.

This is why it's really important to be humble about what you know and what you don't.
Yeah, but doesn't it feel good to occasionally throw that out when others are trying the "appeal to authority?"

Wouldn't an experimental physicist need to have an extremely thorough understanding of the theoretical concepts in their field, as they are the ones applying the scientific method to said theories, and in an extremely strict manner?

That is a definite question, not statement. I may have a completely wrong view of this...

G01
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Wouldn't an experimental physicist need to have an extremely thorough understanding of the theoretical concepts in their field, as they are the ones applying the scientific method to said theories, and in an extremely strict manner?

That is a definite question, not statement. I may have a completely wrong view of this...
I'd agree, a good experimentalist has a thorough understanding of the theory. And conversely, a good theorist needs to have an solid understanding of experiment to keep their work grounded in reality.

Guys, physics is physics.

I'm assuming Philosopher_K's account was disabled, what a shame.

I'd agree, a good experimentalist has a thorough understanding of the theory. And conversely, a good theorist needs to have an solid understanding of experiment to keep their work grounded in reality.
The other thing is that good experimentalists have to be masters of the physics of the experiment. For example if you want to build a gamma ray detector you have to know a huge amount about how gamma rays interact with matter. Since it turns out that you have to launch the detector into space, that means being familiar with the physics of spacecraft.

Is there really such a sharp divide in physics between experiment and theory? It seems to me it would be most reward to be able to look at both aspects of something you are researching and be able to contribute at both ends. Is there a lot of these hybrid types or is it simple too much work to try to do both?

Is there really such a sharp divide in physics between experiment and theory? It seems to me it would be most reward to be able to look at both aspects of something you are researching and be able to contribute at both ends. Is there a lot of these hybrid types or is it simple too much work to try to do both?
What tends to happen is that physicist become specialists on one particular topic, and that particular topic usually falls into theory or experiment. It's both rewarding and necessary to look at a problem from different angles, but that usually works by having several different people bouncing ideas off each other.

I do know of people that have one foot in the theory world and one foot in the experimental world, ,and if you are heading some sort of topic based group, this is rather essential. One note about theory, at least in astrophysics the number of people that are "pencil and paper" theorists is rather small, and most astrophysicists do theory on some sort of computer. For that matter, experimentalists don't look directly into the telescope and most experimental work involves lots of work on computers.

I'm just going to ramble off some observations and thoughts of mine relevant to the question.

First of all, I want to point out that most classes are essentially theoretical (i.e., most classes aren't labs.) These classes are taught by both experimentalists and theorists. So the apparent academic "status quo perspective" is that theorists and experimentalists should both be able to teach the same (theoretical) material. The punchline is that experimentalists still need to know a lot of theory.

Similarly, theorists typically need to know a lot about experiments. That's a big part of what makes it a physics game rather than a math game. The idea is that the distinction between theorists/experimentalist is somewhat blurry.

The theorist spends more time on math/computation, and the experimentalist spends more time on the lab, or actually working on stuff. I think the day-to-day life for a grad student or something is largely divided by this sort of difference. Find the experimentalist randomly at some time during the week and they're probably down in the basement working on the experiment. In contrast the theorist is almost certainly in their office, on their computer, or in a meeting -- but not at a machine.

Simulation is now closely intertwined with theoretical work in modern physics and engineering. This means that as a theorist one often is concerned with "numerical experiments", which are certainly analogous to regular experiments in some way. So the modern theorist is much more like an experimentalist than the theorist of the 40's or 50's, who was really restricted to pencil and paper.

In my opinion, I feel the main personal difference between theorists/experimentalists is the way they really care about the math. Theorists more frequently have a double-major in math or a large interest in abstract as well as practical mathematics. Furthermore, the theoreticians are more people who can really relish the nitty-gritty detail, as oppose to simply tolerate it.

Really, the question is difficult, and I'm sure that sociologists or some such profession could try to write many books about it. I would tend to say the distinction is often subtle and more a practical question (where you spend your time, see above) than anything else.

There appears to be a lot of garbage on here (trolling I imagine), so I stopped reading but will give my opinion.

My point of view is from an "experimentalist", however I haven't been in the lab in about a year and have been doing pure theory in the meantime.

Whether you should be a "theorist" or an "experimentalist" simply depends on what you enjoy doing more. If you like getting your hands dirty, working in a lab, developing experiments then a experimental physics path is up your ally. For some people it is far more rewarding to "do" something hands on than to stare at a piece of paper or computer screen all day. That said, lots of experimentalists also do their own theory, so it is a pretty fuzzy line here. In an ideal world I have a theory, I develop an experiment to test it and try to figure out all the implications of my theory, experiment either matches theory (which is a bit boring) or it doesn't and you have to figure out why, alter your theory and do new tests.

Theorists do more fundamental modeling, often on things that can't yet be tested. They like to play around with the math and theories and try to discover new effects. One of the worst things (from a experimentalists point of view) is most jump ship when they think all the new interesting effects have been discovered, leaving us to finish up will all the nitty gritty details to make the theory actually predict experiments. A theorist tends to stay on the forefront of physics, which can be exciting, but many will have to live with the fact that their ideas may not be proven true in their lifetime (and also may not be true). While theorists have lots of fanciful ideas, until they are experimentally verified they not "true". That said, lots of experimentalists love looking through new theory and trying to bridge the gap to theory (and get out Nature or Science papers).

Either way, both are really useful and you can generally tell after 2nd or 3rd year which you enjoy more.

Cheers

Erebus_Oneiros