On hadron colliders, dark matter and black holes

[torstan]

So, there is a job thread somewhere in here (looks like it got dropped off the bottom of the page) where I foolishly admitted to being a theoretical particle physicist working on predicting what might be seen at the new collider being built under CERN. If this has no interest to you, feel free to skip to other threads, this one will be unashamedly physicsy. I also promised to post here if there was any major news on the collider.

Well, the short version is this - there is a collider being built under the Swiss-French border. Here's a picture of where it sits and how big it is:
cern-lhc.jpg

The big white circle shows the path of the tunnel the collider sits in - it's 100m or so beneath the ground and the tunnel has a length of 27km. Note Geneva airport on the right for scale.

The plan is that protons - the nucleus of a hydrogen atom - will be accelerated around the ring to very close to the speed of light in two beams going in opposite directions. Once they are up to speed these beams will then be crossed (with less dramatic consequences than in Ghostbusters - but this is actually what those beams where based on). The beams will collide at two points on either side of the ring and enormous (6 storey tall) detectors will catch the subatomic debris that comes out.

[torstan]

So, some facts and figures.

The LHC - Large Hadron Collider
(hadrons are composite particles - of which protons and neutrons are two examples. Always be careful when typing hadron not to get the d and r mixed by accident. Easy typo, completely different machine....)

26 659 m in circumference - the largest machine ever built
>10 years to build, and due to start this summer (first collisions predicted in August)
The magnets are kept at 1.9 degrees above absolute zero so they are colder than outer space. This is so they are superconducting.
This requires the world's largest fridge - >10,000 tonnes of liquid nitrogen.
This, combined with the detectors, will produce more than 800,000 GB of data every year and requires a whole new class of supercomputer to be designed to be able to handle it.

This of course is if it works as planned. We'll find that out later this summer.

[torstan]

Okay, all very impressive, but didn't someone mention a black hole?

Well yes, one possible result is that the LHC will produce microscopic black holes the size of atoms. This, contrary to popular speculation, would be great. In fact, some theories predict that we should produce them. However, rather than sucking in the world, these would decay in the detector - exploding in a spectacular shower of subatomic particle that would light up the detector like a Christmas tree. I've seen experimental plots of an event like this. People take it very seriously and would be very excitied if it happened.

But, I hear you shout, what if it doesn't decay? What if the black hole sits there, getting larger and larger until it ate the world?

Well, this has been carefully studied. Though we have never created collisions at this energy in a laboratory on earth before, these type of interactions do occur when cosmic rays hit the earth from outer space. So if this was going to happen, it would have done so already. Okay, so maybe we're just lucky that this hasn't happened to us yet? No. It hasn't happened to us, or to Mars, or to Jupiter, or the sun, or any other object we can see. This was addressed in a recent paper (out this week). I think the abstract (or at least the last line of the abstract) is worth a read:

http://arxiv.org/abs/0806.3381

So no, we will not be destroyed by black holes produced at the LHC. The same arguments (that such interactions have taken place in the earth's atmosphere for its entire lifetime and so any bad thing that can happen should have happened already) is a pretty solid argument against all 'LHC will destroy the earth/universe' theories.

On the other hand, humans are a pessimistic bunch and everyone likes to think the scientists will get it wrong, so I believe that there are a number of End of the World parties being organised for early August....

[RPMiller]

Wouldn't there also be a difference in that the naturally occurring ones do not occur inside of a container that could restrain the event? Does the article say anything about that?

For the record I absolutely do not believe anything bad will happen other than it maybe not working. I am curious about the conspiracy theories though. They always make great roleplaying fodder.

[torstan]

Oops, cross-post. Sorry RP.

There are lots of things we hope to learn from this.

1. We expect to understand the origin of mass by finding a particle called the Higgs boson.
2. I personally want to know what dark matter is. There's 5 times more dark matter in the universe than atoms, molecules and all the other stuff we've been studying ever since we started asking questions. We foun out it was there only a few decades ago and there are good reasons to believe that the LHC will be able to produce it from scratch. That would be the first time ever that dark matter was created in the lab on earth. Incidentally, dark matter was the basis for 'dust' in the Dark Materials trilogy (though there's really no basis for thinking it is conscious )
3. The LHC will test theories that differ on the number of dimensions we live in - the four we know about (3 space dimensions and one time or N/S, E/W and your heightmap for cartographers) or whether there are another 6 or even seven, and whether they are small or large.
4. It may start to shed light on how the universe began and how it may end, and also whether there are other universes.

These are ordered in degrees of speculation. The first we should definitely answer. The last is highly unlikely to be any more than a hint, if we get that much.

But of course, this doesn't answer your question. Neither of those things is likely to immediately lead to any new technologies that will improve your life. Technologies tend to come when we put research into a field where the theory is already known. Fusion has been understood theoretically for about 60 years, but we'll only get our first working fusion plant in 15 years or so. However the theoretical understanding of fusion came from particle physics experiments - and no-one knew when they started those experiments that fusion might come out the other end. The purpose of these experiments is to find out how the universe works. When we peel back another layer, sometimes we find something that can be turned to our own use, sometimes we don't. The point is that in particle physics, unlike many other sciences, we don't know the underlying theory until we look, so we can't say what use the discoveries may have until they have been made.

That said, the field has a pretty good track record. The straightforward results of the work are things like lasers, tvs, radiotherapy and so on. None of these would exist if we had not researched atomic and subatomic physics.

However more important perhaps are the spin off technologies. The LHC has funneled a huge amount of money into brand new research into superconductors, electronics, seismology, solid state physics and (of course) IT. All of the developments that have been made for the collider will be applied in the rest of the world. Without the collider, much of this research could not be done because it would be way too risky for a company to invest that amount of its own capital into R&D that may not work.

Past examples of spin offs are everywhere, but the most obvious is the Web. That was put in place so that the data from the previous collider at CERN could be shared between the international collaboration of scientists working on this. The LHC has a similar challenge - there will be more data produced than ever before and a computer infrastructure needs to be set up to deal with it, and to handle the processing tasks on this data sample. That requires a supercomputer and we've built something called the Grid (yes, we're no good at names) - a supercomputer that spans the globe that consists of networked computers in universities in countries on every continent. You can submit a job to the Grid and it will use the processing power of computers right across the Grid to do the job. It's the largest distributed computer resource in the world and will eventually be made available to everyone, just like the internet.

Hope that answers that question! Wow, that got a little longer than intended....

[NeonKnight]

Oooooooo Noooooooooz! Torstan is going to be responsible for creating The Mist in Geneva!

Ooooooo Noooooz!

[torstan]

@jfrazierjr - This won't give us any energy. Rather we pump energy in to get the particles up to speed and then study the results after they collide. It's like pumping a load of petrol into two trucks, watching the fireball when they collide and then measuring how far the bumper went.

@RP - the protons will collide in a vacuum - the center of the pipe is as empty as the engineers can get it to reduce the chance of them accidentally hitting something other than the proton that is coming the other way. Therefore the collision itself is almost identical to a collision in outer space. In fact, at the atomic scale, even gas is mostly empty, so it's functionally the same as collisions in the atmosphere too, which is where the cosmic ray interactions happen. What happens to the debris afterwards - when it flies off and hits the solid bit, the detectors, is essentially just garbage collection. We pick up the bits and see what happened. So the detector doesn't influence the collision itself. In this way, the collision should be as identical to a collision that occurs outside a detector as possible. Otherwise all we'd be studying was how physics works inside a detector - which wouldn't really help us to understand the wider world

[torstan]

Anyone read Angels and Demons? I'll support any conspiracy theory that says CERN should have a space plane. That would be cool.

(yes - they have antimatter, no - they could never use it to blow up the Vatican)

@Neon -The Mist? How did you hear about that. That's strictly..... definitely not something I've heard about....

[RPMiller]

@jfrazierjr - This won't give us any energy. Rather we pump energy in to get the particles up to speed and then study the results after they collide. It's like pumping a load of petrol into two trucks, watching the fireball when they collide and then measuring how far the bumper went.

@RP - the protons will collide in a vacuum - the center of the pipe is as empty as the engineers can get it to reduce the chance of them accidentally hitting something other than the proton that is coming the other way. Therefore the collision itself is almost identical to a collision in outer space. In fact, at the atomic scale, even gas is mostly empty, so it's functionally the same as collisions in the atmosphere too, which is where the cosmic ray interactions happen. What happens to the debris afterwards - when it flies off and hits the solid bit, the detectors, is essentially just garbage collection. We pick up the bits and see what happened. So the detector doesn't influence the collision itself. In this way, the collision should be as identical to a collision that occurs outside a detector as possible. Otherwise all we'd be studying was how physics works inside a detector - which wouldn't really help us to understand the wider world

Interesting. I'll be very intrigued to hear about the data collection and the results there of.

Have they given any percentages on chance of success for the whole experiment?

[jfrazierjr]

That requires a supercomputer and we've built something called the Grid (yes, we're no good at names) - a supercomputer that spans the globe that consists of networked computers in universities in countries on every continent. You can submit a job to the Grid and it will use the processing power of computers right across the Grid to do the job. It's the largest distributed computer resource in the world and will eventually be made available to everyone, just like the internet.

AHHH... soooo even if you don't directly blow stuff up in a hugh explosion that rips the fabric of space/time, you will be responsible for building a skynet like entity that will eventually destroy humankind....

Like I said, Torstan destroys the world...

Joe