The Higgs field is responsible for mass, but I don’t think it’s quite right to say the Higgs boson is responsible. The mass comes from the particles interacting with the “vacuum expectation value” of the field – basically this means the field has some non-zero contribution even in the absence of Higgs bosons, which as Cecil describes are excitations of the field.
At any rate, the mass of a particle comes from that single particle interacting with the field. But I think there’d also be a force from two particles exchanging a Higgs boson. What I’m wondering is how come no one ever mentions this when listing the fundamental forces (or maybe they do and I just don’t know about it).
I haven’t read Smolin’s book, so I don’t know what all of his arguments are. I’m aware of the issue of the 10[sup]500[/sup] possible vacua, but I’ve heard at least some string theorists express the hope that it will turn out that the number in which we can reproduce the standard model will be far fewer. Right now, we don’t know any solution that exactly reproduces the standard model (other than just its gross features) so even finding one such case would be progress.
It’s worth noting that a major area of Smolin’s research is Loop Quantum Gravity, which is the next most popular proposed theory of quantum gravity after string theory. So it’s not as if he doesn’t have a dog in this fight. Of course, that doesn’t mean he’s wrong, although his opinion is in the minority among researchers on quantum gravity. Smolin, however, would probably argue that the greater prevalence of string theory is more due to sociological reasons (at least, I think he makes that sort of argument in his book).
I’m not sure if the occam’s razor critique is valid. This isn’t like, say, the luminiferous aether of the early 20th century, which post-Einstein turned out to be totally unnecessary to explain the observed physical phenomena. In this case we have a theory of particle physics and a theory of gravity which we know are incompatible, so we need something new to explain how they fit together. Whether this something new turns out to be string theory, who knows, but it’s not like it’s postulating new entities for no reason.
I don’t know, to me it’s exactly the same. Basically the maths doesn’t work without the existence of the extra dimensions of space, so therefore they must exist right? Oh, but hang on, if there were extra space dimensions they would be detectable, but we can’t detect them, therefore they must be curled up so small as to be undetectable. It’s all a lot of hand waving nonsense. There’s no evidence to back it up, only a mathematical construct that can demonstrate some similarities with other theories and it doesn’t make a single testable prediction.
Where I come from accepting the existence of something (or things) on faith alone with no evidence is called religion, not science. String theory is religion for physicists. Don’t get me wrong if it does prove to be correct I will accept it, but at present it will take a lot to prove it. I’m not sure loop quantum gravity has the answers either, but for the first time in a few years there is another game in town. Funding AFAICT has been very limited for those not involved in stringy aspects of quantum gravity.
While I accept your point they didn’t do it for no reason, the fact remains that they did postulate the exitence of the extra dimensions with no evidence other than “elegant” mathematics to back them up. I was quite interested in string theory when I first heard of it (mainly due to Prof Kaku), but when I tried reading some papers on the subject completely failed to se the elegance of the mathematics (it was way over my head, I’m more an experimentalist).
We do need a theory of quantum gravity, bt I just think we’re looking in the wrong place, what the right place is I have no idea.
Funding is very limited for all forms of theoretical fundamental physics, including both Loop Quantum Gravity and the String Model. Fortunately theoretical fundamental physics doesn’t need very much funding: As the old joke goes, all we need is pencils and erasers (in practice, most of the money ends up going to pay salaries of faculty, post-docs, and grad students, and maybe for the odd computer or travel to a conference, but experimentalists have all that plus lots of big expensive equipment). There probably is more funding going to the String Model than to Loop Quantum Gravity, but then, there are more people applying for funding for strings, too.
If they give up on finding a way to test it with experiment, then sure. Otherwise, I think it’s more fair to say that as a scientific theory it’s a “work in progress”. String theory critics like Lee Smolin or Peter Woit would argue it’s too much work for not enough progress, but of course the people working on it don’t agree.
I don’t really have the slightest clue if string theory is right or wrong, but in its defense it’s not like it’s unique in being a presently untestable theory of quantum gravity. So far, no one has found a way to do a definitive test of any theory of quantum gravity. So it’s not like Loop Quantum Gravity or the other alternatives are any better off there.
I agree, sorry if I sounded off a bit, string theory is a bit of a soapbox subject for me.
Lots of theories have not made definitive predictions, but these tend to get weeded out quite early and don’t receive much funding, string theory seems to be a new phenomenon in so far as it is, within the small amount of funding available, getting the lions share of the funding without providing any testable predictions. Alternatively theories that do make predictions can also be weeded out as they are proven incorrect.
Getting back to our original topic of fermions and bosons, the Higgs is to date just a theoretical particle, but the reason that the theory behind this is better than string theory is that with the current generation of particle accelerators (LHC and the one at Fermilab) we can actually look for it and prove or possible disprove its existence.
The same is true for experimentalists, not all Universities or areas of research get good levels of funding, I work at a UK University and we run our experiments on not much more than a shoestring budget, without some innovative work by technicians and students alike we would struggle to keep our equipment going.
There’s a bit of a chicken and egg thing there, though. I mean, is string theory getting more funding than alternative theories of quantum gravity (none of which are presently testable) because more high-energy theorists are choosing to work on string theory and then applying for grants? Or are more high-energy theorists choosing to work on string theory because they think that’s their best bet to get funding? A bit of both, perhaps.
Certainly you’re correct that the Higgs mechanism is in much better shape than string theory (or any theory of quantum gravity) in terms of actually being testable in the immediate future.
Almost certainly a bit of both I would suggest, although with my cynical hat on I would say it probably swings towards the latter, although I must say this is purely my opinion and I have no data to back my assertion except Smolin’s book, which as you pointed out has a certain bias.
I have never heard of anyone having more difficulty getting funding for loop quantum gravity research than for string model research. So far as I can tell, the primary reason that the string model gets more attention is that (if it works) it’s more powerful: It offers a mechanism not just for quantizing gravity, but also for unifying it with the other three forces.
And the Higgs mechanism is not only testable in the immediate future, but to some extent already has been tested. An early version of the Higgs mechanism successfully predicted the masses of the W and Z bosons, which are responsible for mediating the weak force.
I suppose this is all a hijack of the OP, but as someone who was in grad school at the time that string theory became fashionable (the 80s), I’d have to say there was a definite bias in favor of string theory over any alternatives. (Loop quantum gravity has been around a long time, also. If anyone cares, I met Lee Smolin at a party back in the 80s, and he was pursuing alternatives to string theory, even then.) However, the bias was primarily within the field of particle physics, from which it sprang. I don’t know if any up and coming theoretical physicists coming from the particle physics community were able to pursue any alternatives. It would certainly have been all but impossible to find a post doc. I can remember asking some questions about the then underlying assumptions, such as Poincare invariance at an informal seminar, and being jumped on. Here I was, just a second or third year grad student, curious about the subject, and I got an angry response of, “Well if you have any better ideas, why don’t you try them?” I think you would have had to pursue alternative areas of research, such as lattice gauge QCD. The most derogatory spin on it would be that it was a field of very bright lemmings. The most positive, that most of the world’s brightest physicists thought it was the field with the most promise.
The GR community was distinctly more welcoming of alternatives and debating the merits of the various assumptions. I don’t know that they have been anymore fruitful, though, and who knows, they might all be different representations of the same thing.