1 – Little Friends
Particle Physics; Our Little Friends
Our Little Friends; The particle physics, in general, and what we’re trying to do in particle physics in terms of the big picture of how these things fit together. So I’m going to take you on some journeys into particle physics. Now we don’t have long enough to go through the whole spectrum. And neither I am going to try. So I’ll skip over some bits. But I am going to try and give you an idea of what is the Event Horizon of Knowledge of Little Friends.
And what it’s all about understanding the fundamental constituents of matter. What is the physical universe made of? When you get right down to it? If you break things into smaller and smaller pieces, do you end up with a common list of the same pieces? Everything is made of? And what are the forces between those things? And the answer at the moment of event horizon is, yes you do. You end up with a finite number of infinitely small, what we call, fundamental objects that everything else is made of.
First Little Friend; Electrons
The first of those objects was discovered by JJ Thompson at Cambridge with his experiment sitting on his desktop. And what he was doing was studying a phenomenon, then was called cathode rays. There’s a gas in there, fluorescing as mysterious rays pass through it. And one can create them by heating up an electrode and applying an electromagnetic field. Which was all very cutting edge stuff at the time.
And he did various experiments balancing electric and magnetic forces and showed that these things were actually had the same master charge ratio. And then they devise ways to measure the mass. And in the end it convinced everyone that these were not waves, they were particles, they were electrons, in fact. And that, the electron than was established as the first subatomic particle and the first fundamental particle. Despite 100 years of trying, it’s still a fundamental particle. We have not managed to break one of them yet. As far as we can see, there’s nothing inside an electron. It is infinitely small. And it is our sort of gateway to this map.
So we as humans on edge of horizon on a little boat or space ship coming in. As we go further, we get smaller and smaller and we go to higher and higher energy. But the electron is our port of access to this subatomic world. And the first place one kind of go from there is atomic physics. The electron is a subatomic particle.
There are electrons in every atom. And one very quickly able to work out that an atom is not– although an atom of say, sodium, is the smallest piece of sodium you can possibly get. It’s not the smallest piece of matter. You can break a sodium atom up. You can break it into electrons and a nucleus. And it won’t be sodium any more. But there are still smaller things inside the atom, in Sodium. And the same for all atoms.
Electrons of Periodic Table
So one start looking around on the periodic table of Little Friends. And find that life is a little different in this. We’ve travelled to something that isn’t actually looking quite like everyday life. And the first manifestation of that is that when you have electrons bound to these nuclei, you find that they’re not allowed to have just any old energy.
They’re bound in fixed orbits. Now orbits in the solar system, which is the kind of model that Bohr had for the atom. Orbits in the solar system, once you fix the distance of a planet from the sun, than its velocity, is period of orbit, is fixed. So there is a certain lack of flexibility already there, for a stable orbit.
But with the atoms it’s even worse. There’s only certain orbits that are allowed. In principle, the earth could have– it could be anywhere on a continuum from the sun. It could be very hot or it could be very cold. It can be anywhere in between. But that’s not true for an electron going around the nucleus. There’s only certain energies of orbit that it can have.
It turns out that the orbit model is not a good model in the end. It’s not a good picture of what’s going on. The best feature that’s going on is actually you have to take this fundamental particle and you have to introduce wavelike properties to it. Because the best analogy that we think of here is you can imagine where in nature are the discontinuous things where you can’t have a contimum of energies.
And that happens with waves, it happens on the guitar strings. A guitar string will support a fundamental note. It will support a harmonic one octave up. It will support the next harmonic. But that’s all it will support. You can’t have notes in between unless you start pressing threats down and changing the length of the strings. And that’s the analogy that Bohr initially used. And that’s the analogy that leads to quantum mechanics, in fact, for how the electrons are bound around an atom.
So it turns out; the electrons our Little Friends can only have these particular orbits because that certain number of wavelengths of the electron fit into that particular orbit. There are certain barren states that have particular resonant frequencies. And they’re the only ones that are allowed.
And if you want to change Little Friends, you have to change the electric charge of the nucleus which is like changing the length of the string. So that means that when the electrons jump between orbits, they will emit energy at certain frequencies, at certain energy levels.
And that is, in fact, how we know what anything that we can’t touch or smell is actually made of. So it constitutes is a spectrum, electromagnetic spectrum, of a fluorescent bulb. One can see as one excite the electrons, they’re jumping between particular levels and they give off particular wavelengths of light corresponding to those energy levels. If one see emission spectrum of the sun. And you see there are dark lines in it.
And each one of these dark lines is where elements in the sun’s atmosphere are absorbing particular energies because those energies, the electrons, can jump between levels. And these characterise the elements there in the sun. So the only reason that we know what the stars and the planets that are not our own planet are made of, is by observing these kind of emission spectra.
Nature of Little Friends
In fact, the element helium our Little Friends was just called helium from Heliox, the sun god. It was discovered on the sun before we discovered it on the earth by looking at emission lines. So that introduces, although the electron Little Friends started off as a fundamental particle, it’s now suddenly got wavelike properties because it’s like a note on a guitar string. And that’s the kind of, the insight in quantum mechanics.
Actually these fundamental particles are not particles. Neither are the ruby waves. They’re a new kind of object called a quantum excitation, if you like. But because of those wavelike properties, there’s then the very clear connection between the energy and the size. So, as we go further, we’re going– looking at smaller and smaller things, deeper into the heart of matter. But we’re also going up in energy. This is super high tech.
Once we have high energy machines, one want to see small stuff. If we want to see small stuff, one need short wavelengths. So that means high frequency, which means high energy. So that’s why particle physics is also high energy physics. That’s why we need huge colliders and things to try and see the very small stuff, because of this connection between wavelength, frequency and resolution.
If one think about it, if our eyes are sensitive to radar, then we wouldn’t be able to see you now because radar has wavelengths of metres and you’d be smaller than that. But our eyes are actually sensitive to hundreds of nanometers, which is pretty good for seeing small stuff. But if you wanted to see smaller, you’d go up in energy, which means x-rays, or electron microscopes. So you can think of the big particle colliders like the Large Hadron Collider, is just the biggest, most powerful, highest resolution microscopes we can build. So I’ve already mentioned the Large Hadron Collider, that’s one of the stars of the show.