It is a theory, like everything else in physics, including the workings of gravity.
It's a bit of a shame that in elementary school and high school, people are taught about "facts" such as Newtonian physics without exploring also some of the weirdness of quantum physics that challenges classic physics. I.e. I had no idea about all the controversy around how gravity "actually" works until I read a book on string theory - I went 25 years just assuming "yup gravity is a thing and we understand 100% how it works."
Sorry, I don't have a book to recommend, just babbling away.
EDIT: Maybe the string theory book I read would be a good place, actually? I can't remember if it delves much into anti matter - The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory (Paperback) https://www.goodreads.com/book/show/8049273-the-elegant-univ...
>"I had no idea about all the controversy around how gravity "actually" works until I read a book on string theory"
FYI, there seems to be quite a bit of controversy regarding whether string theory is even science:
>'Many of today’s theorists — chief among them the proponents of string theory and the multiverse hypothesis — appear convinced of their ideas on the grounds that they are beautiful or logically compelling, despite the impossibility of testing them. Ellis and Silk accused these theorists of “moving the goalposts” of science and blurring the line between physics and pseudoscience. “The imprimatur of science should be awarded only to a theory that is testable,” Ellis and Silk wrote, thereby disqualifying most of the leading theories of the past 40 years. “Only then can we defend science from attack.”'
I think it's not correct to hold this kind of physics to the standard of science that other disciplines use.
The standard, scientific method version of science is 'guess a model of how the world works, then run an experiment to see if it's true'. This packages (hides, even) a bunch of principles of rational thought inside of it - for instance, that a stance about how the world works had to be able to be wrong, and that you should be picking your opinions about how the world works based on what you can (repeatedly) demonstrate.
But there are other paths to knowledge- and revelation- gaining that are performed by scientists all the time, yet don't fit this model. It's perfectly legitimate to get a grant to run an experiment to just look at something closely, such as a star or a blank patch of sky, or a material, or an organism. 'I want to collect data on X' is perfectly legitimate as a way to learn about the world. After all you need observations about something in order to build the initial model that you use to generate hypotheses in the Scientific Method (tm) anyway. Another example: sometimes experiments are done just to find more accurate readings of numerical constants.
Anyway, mathematicians and the more theoretical physicists aren't really looking to run experiments to test hypotheses. Instead their 'experiments' are finding new models for looking at things and their 'results' are finding new mathematical statements, or finding ways to prove things that were previously hard to prove, or just finding new ways of looking at things that make thinking about them easier. This is 'output', and a net gain in human knowledge, without being a testable hypothesis, and I think that's fine. It's still subject to the underlying rationalism behind science. But validation is entirely theoretical: a good theory makes things make sense, and doesn't make things not make sense in ways that disagree with physical experiments, and makes things simpler and better. And it's fine that these criteria are abstract and to an extent subjective.
Of course it's still necessary to have a way to say if theorists are failing, or wasting their time, or producing too little or too quality output, and I don't know how that's done or it ought to be done. But it doesn't bother me that they don't produce physically testable results.
I think it is important to keep in mind that theories can sometimes only become testable after sometimes unforeseen advances in technology. Consider the Higgs field, theorized in 1964 [1]. This field was only detected, via the Higgs boson, in 2012 [2]. The Large Hadron Collider (LHC) [3] and its computing grid, which detected the Higgs boson, generated 25 PB of data per year, had 150 PB storage, and 200,000 processing cores [4] (which I assume were at least 1 GHz on average). In the 1960s, the Cray CDC 7600 supercomputer had a computing speed of 36.4 MHz and 65 kword memory [5], and IBM produced the 1311 HDD with about 12 MB storage [6]. Thus, the LHC required advances in fiber optic cables, a 5-million-times increase in computing over existing state-of-the-art processors, an 89-million-times increase in computer storage (from 12 MB to assuming 1 TB per HDD), and integrated-circuit RAM. More directly, the 1971 ISR hadron collider had energies of 31.5 GeV [7] compared to the LHC's 6.5 TeV [8], 200x increase.
What other theories might become testable if we could reach 130 TeV, analyzed by a computing grid with 1 trillion processors and 1 yottabyte of storage?
Antimatter is old news. When CERN discovered the higgs boson a few years back, we did so by looking for the higgs decay products (the higgs is really unstable), a significant fraction of which are antimatter.
For example: One of the most important higgs signals was the Higgs -> 2 Z boson -> 2 electron + 2 anti-electron decay chain. Or in particle physics jargon H -> ZZ, Z -> e+e-. The important thing is that e+ is an anti-particle, one of the few that was discovered early enough to get its own name (the "positron" was discovered in 1932 [1]).
Since the positron discovery we've discovered so many anti-particles that we stopped giving them special names. We just call them e+, mu+, tau+, p-, etc, to say nothing of the composite particles that are composed of both matter and antimatter.
Not only that, but a PET scan (a common medical imaging technique, tangentially similar to an MRI or CT scan) relies on antimatter. The name stands for Positron Emission Tomography, in fact.
The general idea: You get injected with a tracer containing a β+ emitter. This produces positrons (antimatter) through radioactive decay. When the antimatter collides with regular matter inside your body, it annihilates, producing a pair of gamma rays moving in opposite directions. Those gamma rays can be detected and used to triangulate where the annihilation occured, generating a 3D image of where the tracer has accumulated in your body.
Typically, the tracer will be something that looks like glucose to the body, so it's accumulated in areas of high metabolic activity. This allows us to see what parts of your body are active. (For example, seeing which neurons in your brain are firing.)
According to the Wikipedia articles on the topic, antimatter (specifically, positrons) were first suggested as possible in 1928 (a consequence of the Dirac equation), and the first observation of a positron was 1929, and the linkage between the theory and experiment was done in 1932.
Antimatter, then, predates the discovery of quarks.
Right. Science uses the word "theory" in the same sense as music theory. A scientific theory is a collection of related ideas that form a robustly cohesive whole, with the power to explain some set of phenomena.
