LHC goes live!

[asterroc]

The Large Hadron Collidor goes online today! This is as exciting as the day Hubble opened its shutters May 20 1990.

Even a lot of sciencey people I know have been asking about what the LHC is, and why the doomsayers are wrong, so here's a little summary of it. Particle accelerators (as is the LHC) are devices that smash things together to find out what's inside them. It's somewhat like if we wanted to learn how cars work, so we did head-on crash tests. While the analogy isn't perfect (no analogy ever is), there are some similarities. For example, while head-on crashes in real life are dangerous, crash tests are completely controlled and are entirely safe. Particle accelerators let us learn about what's going on inside small particles. Older lower energy ones smashed together "normal" particles like electrons and protons and helped us to learn that those are made of quarks. The LHC is a high energy one and we'll be smashing together another type of particle called a hadron, and it will help us learn how the entire universe works, for example gravity and dark matter.

The woo-hoos (aka tinfoil hat wearers) have been saying doom and gloom about the LHC, claiming that the high energy levels will either rip a hole in the entire universe, or else create a black hole that will swallow the Earth. Well, there's really no reason to worry at all. First off, we only call the LHC "high energy" by comparison - it's higher energy than anything people have been able to do before now. However, much higher energy collisions take place every second as cosmic rays hit the Earth's atmosphere. The main difference is that in the LHC these collisions are controlled. As I said to a biologist in another community, being afraid of that is kinda like if people were afraid of scientists culturing e.coli - it happens in the wild, after all, and that's not scary at all.

Comments

[meleah.livejournal.com]

Ended up trying to talk to students about this and realizing I'm useless at knowing much about this or translating it into student-speak. So.. if you don't mind me picking your brain:

What exactly is a Hadron?

How is the collision controlled?

Why is it buried so deep underground?

What are the possible applications of this knowledge? (I mumbled something about testing the Big Bang theory and quantum stuff, but obv. I'd like a real answer :) )

[zandperl.livejournal.com]

Particle physics is NOT my specialty - in fact I've never taken a class that ever mentioned anything smaller than quarks. However, I'm certainly willing to tell you what I can glean from other sources.

1) Hadrons are certain subatomic particles made out of quarks, but not all of them. Protons, electrons, and neutrons are all made of quarks, but only protons and neutrons are hadrons. Hadrons include the subcategories of baryons/fermions (matter, things with mass) and mesons/bosons (things that carry forces or fields, like photons I think).

The answer you should give your students is that protons, neutrons, and electrons are not really the smallest particles - they're made of quarks, which are even smaller, and there's other stuff that's also made of quarks, and some of those are hadrons. I would use an analogy like plastic - we have lots of things that are made out of plastic (quarks), but only some of them are bottles (hadrons, maybe protons are Pepsi bottles and neutrons are Nalgene bottles, alliteration not intentional believe it or not) while some are pens or bags or whatever (non-hadrons, maybe electrons are Bic pens).

2) The actual type of hadron they're using mostly is protons (I don't know why they don't just call it the Large Proton Collider). Protons have a positive charge. Anything with a charge is affected by electric fields, and the way the beam is created in the first place likely uses the same technology as a cathode ray tube (like in older CRT monitors and TVs) just scaled up to a much larger size. (In short, CRTs create a electric potential difference between two pieces of metal, and the difference is so great that the protons leap off the metal.)

Once the protons are moving, anything with a charge that is moving is affected by magnetic fields. This is the same principle that runs maglev trains, and everything with electromagnets such as stereo speakers and engines/generators. With a bunch of magnetic fields that the operator can control, the LHC keeps the protons in a skinny beam, and purposefully makes them lumped into groups instead of being a smooth beam. They're also sped up and made to miss each other until they get up to 0.999c (c = speed of light), and then they're made to collide.

3) Each individual collision is high energy, though not such a high energy that it doesn't happen in nature, it's just slightly more rare. However if you point the beam wrong and it goes out a side tunnel, there will be *lots* of accidental collisions from the many many protons, and add them together and you'll eat through concrete, as in today's PHD comic. But it's also practical I believe, not just safety - it's hard to get that much space above ground, you want as little vibration as possible, you don't want nutjobs able to sabotage it easily, etc.

Q4 will be answered in next comment.

[zandperl.livejournal.com]

4) Nothing practical immediately other than learning more about building computers and massive underground engineering projects - maybe if we'd done this before the Big Dig it would've gone more swiftly! As I understand it, gravity and dark matter are two huge goals (and as an astronomer rather than a cosmologist I understand those better). Basically for some reason entirely unknown to us, gravity is much weaker than the other three fundamental forces (gravity, electromagnetism, strong force, weak force). The high energy collisions will help us to understand why gravity is so weak. There's also a hypothesis that we'll discover that every normal particle (like electrons) have a high-mass "twin" that only interacts via gravity - which would mean that these "twins" are dark matter. I believe we've also never detected gravitons, the particles that carry gravity the way that photons carry electromagnetism, so we'll be looking for them. And I think that this will also help us to finally start testing String Theory, which is how cosmologists are trying to unify gravity with the other forces (once called the Grand Unified Theory, GUT).

These things will help us to understand how the universe works today and in the past, how galaxies formed, why the Big Bang happened, what existed before the Big Bang, what the future of our universe is, if time travel is possible, or faster-than-light travel, or gravity/anti-gravity machines. None of this will be directly *useful*, at least not for hundreds of years IMO, but it's exciting to *know*.

[l0stmyrel1g10n.livejournal.com]

gravitons? seriously? i thought Star Trek was just making that shit up. next you'll be telling me that an interferometric pulse through a chroniton buildup causes a warp field bubble which destabilizes the deflector array.

...Firefox's spellchecker is complaining about chronitons, but not interferometric...now i'm worried.

[zandperl.livejournal.com]

Interferometry is how we get multiple radio telescopes to work together, like the VLA. Basically we take the signal from one telescope and compare it to every other telescope (much like you can use beats to tune a guitar) and that gets us a much more detailed image than if we'd just used one telescope. Or for another example, get some writing and move away from it until it's just barely readable. Now close one eye, and chances are you won't be able to read it. But when you put your two eyes together you *can* read it - same thing with interferometry, we can see things better with more telescopes than just one.

The rest of that jargon is rubbish, but antimatter does exist (the Sun creates positrons [aka anti-electrons] all the time, and they annihilate with normal electrons to cause part of the light the Sun emits), and we use strong magnetic fields to contain it when we create it in the lab.

There are books and webpages out there on the physics of Star Trek. Most of what they have is mumbo-jumbo, but some parts are references to sound science.