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.'"

Re:What?

[Wandering Wombat]

Basically, no.

Re:What?

[The Ancients]

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.

Re:What?

[fbjon]

They're affected by curved space due to gravity.

Re:Here's a question: what if it's not there?

[SnoopJeDi]

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.

Re:What?

[Anonymous Coward]

That description is gravity as described by Newton's universal gravitation. Under general relativity, gravity is a warping of space-time, not a force. In the various incarnations of quantum field theory, gravity is mediated by a (hypothetical) elementary particle called the graviton. It works, put simply, much like the electromagnetic field, which is mediated by virtual photons, but in this case it would be virtual gravitons.

Large Hadron Collider

[Anonymous Coward]

You really can't mention porn and then expect people to read Large Hadron Collider as anything but Large Hardon Collider.

Re:What?

[kebes]

As the other poster mentioned, photons are affected by gravity in as much as they travel through a space-time that is curved by massive objects. So the path of a photon (e.g. light) can be deflected by a gravitational field.

To those who would then say "Aha! So clearly photons do interact with gravity!", it's important to note that photons may be affected by the curvature of spactime, but they don't have mass and thus don't interact gravitationally. For instance, photons cannot attract each other gravitationally (whereas matter does), and a photon won't attract matter gravitationally.

Re:What?

[fbjon]

Space isn't even a particle and doesn't have mass, so why should it curve? I wonder, does gravity affect space or merely everything in that space? Could we tell the difference?

Yes we can detect the difference: light curves in a gravity well. Also you seem to be confused about curving space. Mass causes space to curve, lots of mass, lots of curvature. The effect of this curving is what we call gravity.

Midichlorians don't explain the force

[Bryansix]

The force was so much more in ep 4,5,6. Why did they have to screw it up with Midichlorians? It's more like an invisible link between all living and intert objects just like the summary says. How do you think Yoda lifted that rock?

Re:What?

[MightyMartian]

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.

It's much weirder than Star Wars

[DancesWithBlowTorch]

So basically, gravity?

No. The Higgs Boson is a particle that's needed in the Standard Model to explain why certain Bosons (the W and Z) are massive, while others (the Photon) are not, although they all unite to a common field (the Electroweak interaction) at high energies. Some people call the Higgs the "mass giver". I personally never liked that name because it suggests that this Boson somehow carries mass from one place to another, which it does not. It's simply one Eigenstate of the Model after symmetry-breaking that really has to be out there if Electroweak Unification (and thus the Standard Model) are to make sense. If there were no Higgs, all the Bosonic modes of the Electroweak field would have to be massless (so-called "Goldstone Modes"). If this was the case, the Weak Force (which is mediated by the Ws and Zs) would have infinite range, just like the Electromagnetic Field (which is mediated by the remaining mode, the Photon), and that would really mess this Universe up.

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.

Re:Obligatory

[fbjon]

I wonder how many papers/emails/reports/whatever have been written where a d/r reversal typo has made its way to the final draft.

At least a few [google.com], it would seem.

Space doesn't curve

[Xelios]

Curved spacetime is a mathematical model we use to describe the motion of matter in a gravitational field, it doesn't mean space is physically curved. "Spacetime" doesn't really exist, it's an abstract mathematical concept that combines physical space with the fourth time dimension and that is what physicists use to model gravitational effects.

That's why physicists are so keen on finding a so called "God Particle", because gravity still can't be explained. We can model its effects, but since space doesn't curve some other mechanism must be at work to transfer gravitational force between objects.

IANAP, so if there are any real physicists out there correct me if I'm wrong.

Re:such a thing as "overpopularising" science

[Guy Harris]

but you'd hope that National Geographic would retain some sense of integrity.

They did, as far as I can tell; I couldn't find any sign of references to "The Force" in their article [nationalgeographic.com]. That crap is from the Gizmodo article [gizmodo.com].

Re:Space doesn't curve

[Guy Harris]

My thinking was that since the Higgs boson is supposed to explain mass it may also help explain gravitation, since the two are obviously linked in some way.

Actually, in general relativity, gravitation is linked to energy and momentum, not just (rest) mass (well, to the stress-energy tensor [wikipedia.org], 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 [wikipedia.org] and affect other particles through gravity [wikipedia.org].

Tibet is in Berkeley now?

[dwater]

Written nicely in an entertaining way for the layman such as myself.

I couldn't help noticing this statement though :

"He has long, gray hair and a long, white beard and, with all due respect, looks as if he belongs on a mountaintop in Tibet."

Those physical features are notably absent from the stereotypical mountain top Tibetan dweller - ie the Tibetan monk. Ah, using Google images shows a couple of people with long beards, but not typical, judging from the results.

My guess is that he's talking about the Unix lab named "Tibet" at Berkeley University where you'll undoubtedly find many such specimens.

Yes, I made that up - I've no idea if there's a Unix lab named "Tibet" at Berkeley.

Higgs boson like mud...

[Roger W Moore]

I've never understood something about the Higgs boson. It is supposed to give the massive bosons their mass, right? And yet, at the same time, it is itself supposed to be a massive boson, right?

Yes that is correct, the Higgs boson gives itself mass. If you use John Ellis' example of the Higgs field being like mud and the more the mud sticks to an object the heavier, and harder, to move it becomes. Well imagine you try to move a lump of mud. Mud sticks to mud so even just moving a lump of mud will be hard. This is what the Higgs boson is, metaphorically speaking.

Re:Question for the Polite Physics Guy

[l2718]

Just to show I'm not always cranky, here's a sedate reply. Warning: it's long. The short answer is that you can't be pulled without pulling.

Photons are affected by gravity (they follow the curvature of space caused by massive objects). But, they don't "cause" gravity, because they do not attract other objects. My understanding is that gravity is relational, which is to say, objects exert a "pull" on each other proportional to their mass. So... how can photons be pulled without also pulling? (I'm going on the assumption their pull is exactly zero, and not just infitessimally small.)

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 [oregonstate.edu] is a "fact". The double helix [wikipedia.org] 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 [wikipedia.org]?) 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

Re:Here's a question: what if it's not there?

[ceoyoyo]

In his book Lederman estimates that a third of the world's GNP is somehow related to quantum mechanics. Seems a pretty good return on investment so far.