In modern physics, antimatter is defined as matter composed of the antiparticles (or “partners”) of the corresponding particles in “ordinary” matter, and can be thought of as matter with reversed charge, parity, and time, known as CPT reversal. Antimatter occurs in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. Minuscule numbers of antiparticles can be generated at particle accelerators; however, total artificial production has been only a few nanograms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling.

In theory, a particle and its antiparticle (for example, a proton and an antiproton) have the same mass, but opposite electric charge, and other differences in quantum numbers.

A collision between any particle and its anti-particle partner leads to their mutual annihilation, giving rise to various proportions of intense photons (gamma rays), neutrinos, and sometimes less-massive particle–antiparticle pairs. The majority of the total energy of annihilation emerges in the form of ionizing radiation. If surrounding matter is present, the energy content of this radiation will be absorbed and converted into other forms of energy, such as heat or light. The amount of energy released is usually proportional to the total mass of the collided matter and antimatter, in accordance with the notable mass–energy equivalence equation, E=mc2.

Antiparticles bind with each other to form antimatter, just as ordinary particles bind to form normal matter. For example, a positron (the antiparticle of the electron) and an antiproton (the antiparticle of the proton) can form an antihydrogen atom. The nuclei of antihelium have been artificially produced, albeit with difficulty, and are the most complex anti-nuclei so far observed. Physical principles indicate that complex antimatter atomic nuclei are possible, as well as anti-atoms corresponding to the known chemical elements.

There is strong evidence that the observable universe is composed almost entirely of ordinary matter, as opposed to an equal mixture of matter and antimatter. This asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics. The process by which this inequality between matter and antimatter particles developed is called baryogenesis.

Antimatter particles carry the same charge as matter particles, but of opposite sign. That is, an antiproton is negatively charged and an antielectron (positron) is positively charged. Neutrons do not carry a net charge, but their constituent quarks do. Protons and neutrons have a baryon number of +1, while antiprotons and antineutrons have a baryon number of –1. Similarly, electrons have a lepton number of +1, while that of positrons is –1. When a particle and its corresponding antiparticle collide, they are both converted into energy.

Megathreads and spaces to hang out:

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  • VHS [he/him]@hexbear.netEnglish
    0·
    2 years ago

    the number of people who write off all “old movies” (roughly before 1985) is concerning. the 70s was an amazing decade for film, and netflix has almost nothing pre-1980

    i heard that netflix even lacks 1980s horror films. the 80s were a huge decade for horror

    • HoChiMaxh [he/him]@hexbear.netEnglish
      0·
      2 years ago

      the number of people who write off all “old movies” (roughly before 1985) is concerning.

      Is this even a thing among adults

        • HoChiMaxh [he/him]@hexbear.netEnglish
          1·
          2 years ago

          Yeah ok. I’d say in general most people don’t watch that many movies made more than 20 years before they were born. I watch a lot of movies, old and new foreign and domestic but realistically I don’t watch more than maybe one a year made in that time frame as applied to me.

          IDK right or wrong I think it’s pretty important to contextualize these numbers rather than going the “kids these days” route.

          Also Netflix sucks. If you have a library card you probably have free access to stream films on Kanopy which has a ton of great older films.