eli5 I read that no particles in the universe can be created or be destroyed but changes form. Is this true?
In: Physics
How are you defining “particle”? Energy cannot be created or destroyed, just changed from one form to another.
However, we can “break” particles, ranging from bigger ones like molecules very easily (through burning, chemical reactions, enzymatic processes etc.), and we can break atoms through nuclear fission – it turns them into lighter elements, neutrons, and releases energy too. This means that if you gathered the neutrons and lighter elements up, they’d weigh less than the original atom because energy was lost, and e=mc^2. In one sense, the particle has been destroyed, but in another you’ve converted it into other atoms and free neutrons with the loss of some energy.
In this second reaction, you’ve converted nuclear potential energy into heat and light, for instance.
It’s not true the way the question is phrased.
Particles can absolutely be created out of nothing but energy and annihilate into radiation. That’s how matter and antimatter work.
But it’s not true even for more common processes, like nuclear decay. There’s no electron hiding inside a neutron before it decays, it’s created.
But there are certain specific quantities, such as charges and “quantum numbers”, which seem to be preserved through all changes (decays, collisions), and they dictate what is “allowed” to appear and what combination of particles cannot be a result of a transformation.
So for example, in the aforementioned neutron decay, the neutron lacks an essence of “electroness”. That’s a quantity called “lepton number”. It’s 0 for the neutron. For an electron, it’s 1. Those are not the same number. To make this work, there’s another particle emitted, an electron antineutrino. It has a lepton number -1. 1 + (-1) = 0. Now this all works out.
Depends on the level of particles. If you’re talking atoms, yes, they break/”are destroyed” into their subcomponents, mainly protons/neutrons, and recombine.
If you’re talking protons and neutrons, they can also break down themselves in neutron stars, or when neutron stars collide in a kilonova (quarks soup), that’s when they recombine to form heavier atoms. Also happens in particles accelerators.
Breaking quarks though, I’m not sure.
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Matter and energy cannot be created. The same amount of matter+energy that existed in the beginning of the universe is what exist now.
Matter can transform into energy and energy can transform into matter.
People get confused because matter can transform to a different matter and thus “new” matter is created. But the total mass remains the same.
Hydrogen atom fuses with another hidrógen atom and forms Helium. Helium would be a “new” element. But it’s ever so slightly “lighter “ (has less mass) than the 2 hydrogen atoms. That mass that was “lost” turned into energy. And basically that’s how a fusion reactor, or star like our sun, works.
A neutron can “create” an electron” under certain circumstances but it doesn’t actually create anything from zero it just transforms
High school level: Particles like electrons, neutrons, and protons stay around and just change arrangements……
College: …..but you can annihilate particles with their anti-partner to release energy, and the particles can change as long as you conserve charge. You can also generate particle pairs with high energy events.
Grad school: Except at the biggest scales you don’t even have to conserve energy. For more details here’s something about Noether and a big big textbook. Have fun.
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