Slashdot Mirror
CERN Scientists Looking for the Force
An anonymous reader writes "National Geographic has a fascinating article on the God Particle, which can help explain the Standard Model and get us closer to explain the Grand Unified Theory. The obligatory Star Wars-angle summary is even better: 'CERN's scientists, the fine people who brought us the W and Z particles, anti-hydrogen atoms and hyperlinked porn web pages, are now hard at work building the Large Hadron Collider to discover something even cooler: the Force. Yes, that Force. Or like physicists call it, the Higgs boson, a particle that carries a field which interacts with every living or inert matter.'"
No. According to Newton's Law of Gravitation the force of gravitation allows two particles with mass to attract one another.
This doesn't cover all particles.
The Mothership
They're affected by curved space due to gravity.
True confidence comes not from realising you are as good as your peers, but that your peers are as bad as you are.
Parent pretty much sums up particle physics, and why people don't get it.
If they don't find a Higgs boson, they're still stepping into a massive new range of collision energy. I think the LHC will produce collisions with a total energy of 14TeV (I haven't read about this for a while).
This step up allows all sorts of other interesting experiments to be run too.
Not to mention, GP smells a little under-the-bridge. But so does every post related to religion on slashdot.
Unfortunately folks are mixing Newtonian and Einsteinian explanations of gravity. In Newtonian physics, the particles exert attraction on one another, in Einsteinian physics spacial geometry is curved around gravity wells (whether that's an atom, a human or a black hole), and it is that curvature that causes bodies to attract.
Cue the bowling ball on the mattress with the marble moving towards it. That's a reasonable analogy of what goes on.
Then cue quantum mechanics, which takes such a delightful model and tosses it on its head.
The world's burning. Moped Jesus spotted on I50. Details at 11.
But this all has nothing to do with Gravity in the sense of "things attracting each other due to their mass", or rather "mass curving space-time". The Standard Model does not incorporate Gravity in the picture (that's why it's called the Standard Model of Particle Physics, not Physics as a whole). The theory for this force is (still!) called "General Relativity". Despite a lot of really intelligent people (no self-compliments here, I have stopped working in the field as I felt way too stupid for it) trying really hard, we still don't have a generally accepted theory for how Gravity and the other, (quantum) theories can be combined in a principled manner. CERN might help a lot with this but, ultimately, we might have to wait till the big crunch, if it ever comes, to see how all those fields really unite.
But really people, why do we need Star Wars to make this sound cool? This is an amazing universe of ours. It doesn't need George Lucas to make Light and Magic.
True confidence comes not from realising you are as good as your peers, but that your peers are as bad as you are.
Actually, in general relativity, gravitation is linked to energy and momentum, not just (rest) mass (well, to the stress-energy tensor, which includes not just energy and momentum per unit of space - energy and momentum density - but the flux of energy and momentum), which is why, for example, photons, with no rest mass, are still affected by gravity and affect other particles through gravity.
Let's start with your followup question: the curvature of space is no more a "mental model" than other objects more modern science, such as photons, DNA, or other galaxies. It is a fact in the following sense: the world around us behaves (to a great accuracy) as if it is "really" curved, there "really are" electrons and photons, "there is" a big molecule called DNA with a double-helix structure etc. If you want, a pattern of dots on a photographic plate is a "fact". The double helix is a mental model that explains this fact. But the distinction is not useful when you're doing physics. If you accept that the goal of physics is to predict the behaviour of the world to a given accuracy, you should also accept that it is not useful to make the distinction between what the world "really is" and what it "appears to be" (for our purposes here -- not as a metaphysical question).
Next, you are confused because you are trying to use two different mental pictures of gravity at the same time, and probably don't have a good mental picture of photons. So I will analyze the situation from the points of view of both Newtonian mechanics+Special relativity and General Relativity. In Newtonian gravity, particles are affected by gravity which is an interaction between all pairs of particles. If A attracts B then B attracts A, in fact with the same magnitude of force. The interaction is proportional to the mass, so an object of "zero mass" won't interact with anything, but such an object doesn't make sense anyway (what happens to F=ma in this case?).
Now what about electromagnetic radiation? You can treat it either as a electric and magnetic fields filling space, or as composed of photons. In either case, it has momentum (do you know about light sails?) and also energy (you can be heated by sunlight!). Special relativity says (E=mc^2) that if you have energy you also have mass. You can now make a naive model in which the elecromagnetic field generates gravity according to its energy density (every small piece of space contains some elecromagentic field, this has energy and hence mass; it is a source of gravity), or you can make a model in which each photon generates gravity according to its mass. In the second case you can even calculate the effect of other masses on the photon -- the deflection you will see for a photon passing near the sum is about half what is observed in practice.
The picture above is not self-consistent. The reason is that Newtonian mechanics allows for action-at-a-distance (gravitational fields propagate at infinite speeds) which cotnradicts relativity. A better picture is that of General Relativity: the space itself is now allowed to change with time. Now there are two separate effects: first, bodies moves along the analogue of "straight lines" in a curved space; second, the curvature of space changes with time -- both under its own effect (gravitational radiation, if you want) and under the effect of the "contents" of space. The "contents" including everything in space. That includes elecromagnetic radiation -- it has mass, momentum, and can act as a source for gravity, by changing the curvature of spacetime.
Part o