AQA A-Level Physics/Particles and Anti-particles
The idea of mass and energy
As you may know already, the famous equation that einstein came up with was , but not that many people would be able to tell you what that meant off the bat unless they had been reading up on physics or the equation itself. To understand what this means, you have to understand what mass and energy were thought as in olden times.
Before einstein came up with that, the idea of things were all based off newton's laws of physics (which is in module 2), which were used to explain where energy was built up from, how it's used and where it comes from when things with mass move along. Now, newton was a very nice fellow, whom everyone listened to and looked up to, particularly because he had a lot of ideas which were pretty groundbreaking at the time, and allowed people building houses and things to calculate things with exact measurements, rather than just guessing.
So, to sum it all up, newton said that things only had energy when they were given it -- when someone throws a ball, energy is transferred to make it move, then when it's stopped moving, it has no energy left. Sounds pretty true, and it is .. when things are stood still, you'd think they had no energy, so they aren't moving. Well, Einstein sort of wiggled his hand up and said "Ooh, ooh, but that's not right!".
What einstein said was basically that things which have mass also have energy which is associated with that mass, and that it had that energy associated with it even when it was still, or at rest. Now, to imagine this principle, you have to think something which has mass, then imagine that that mass is actually the same thing as their mass has an energy equivalent. This is the concept of mass energy equivalence, and it's exactly what means!. If you still can't get the concept, don't worry. Here's a few ideas.
The playdough idea
Imagine that something like a car, is made of playdough. Now, when you have playdough you can rip bits off and make other things out of it. Now, imagine that when the playdough is made into something, it goes hard and you have a solid object, but when it's soft, it's easy to model into other things. That's kind of like how energy works when you're talking about particles.
Basically, energy and mass are interchangeable, and anything that has mass has an energy amount, which is larger, associated with that mass. This broke free of the newtonian ideas, as he said objects at rest have no energy associated with them.
Particles
Now, you may be thinking about why particles are so important. Who cares if something super-small exists and does x, y and z ? Well, lots of people -- and you too will find it important because it describes something which is interesting because it's happening millions of times around you in a split second!
Now, if you remember the original things were the proton, the neutron and the electron, which are what the majority of all atoms (except antihydrogen) are made out of. Now, you think of these being the only particles there are, but, unfortunately, there's lots of other kinds of particles which are smaller and do all kinds of crazy things! In this bit, we've got a lot to go into, but it's all very easy stuff, and if you remember one key rule, you'll be fine.
- These concepts were created by humans, and are understood by them.
Anti particles
These lovely things sound like they're straight out of star trek, but they're nowhere near as complicated when you think about it. They're basically the reverse image of the normal particle, and have similar properties and have a similar structure, but they're the mirror image.
Have you ever head in maths where if you do +1 and add it with -1? Well, that's how it happens with particles and antiparticles. Now.. are you ready to get into the nitty-gritty of the particles? It's not hard, i promise you.