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M or String theory

~enigma~

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SInce I mentioned branes in one of my other posts I thought I would ask for some opinions here regarding the topic. What do you guys think, is the theory true or false?
 
IMHO, String Theory is pseudo-science. My opinion could change if someone used ST as the basis for a gravity-control device, FTL travel, or some other such gimmick from the realm of science-fiction.

Without a practical application, String Theory, if true, is completely irrelevant in the common scheme of things.
 
Read "The Trouble with Physics" by Lee Smolin. He doesn't think that String Theory has as much promise as it seemed to 15 years ago.He presents a great case.

Great book, though. I've almost finished it.
 
Fnord said:
IMHO, String Theory is pseudo-science. My opinion could change if someone used ST as the basis for a gravity-control device, FTL travel, or some other such gimmick from the realm of science-fiction.

Without a practical application, String Theory, if true, is completely irrelevant in the common scheme of things.
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Well there is FTL travel as far as light goes as can be seen in the experiment by Wang here

The experiment has been duplicated and done with different gases. others (most notably Gisin) have done other experiments that show entangled particles transfer "information" at speeds that dwarf light speed. But then again, this is quantum stuff and not string theory.
 
Well ... I didn't mean FTL transfer of information based on quantum theory, but an actual, operating "starship" based on string theory taking real people going to Alpha Centauri (for example) and returning in less time than it takes light to make the round trip. (That's about 8.70 years for Alpha Centauri).
 
Fnord said:
Well ... I didn't mean FTL transfer of information based on quantum theory, but an actual, operating "starship" based on string theory taking real people going to Alpha Centauri (for example) and returning in less time than it takes light to make the round trip. (That's about 8.70 years for Alpha Centauri).
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that's quite a high standard you've set there :D
 
I don't believe there's anything in String Theory or M-Theory that supposes such a trip is possible.

However, to be real science it ought to at least predict an observation... can anyone describe that aspect of it?
 
andyandy said:
that's quite a high standard you've set there :D
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Well ... think about it ...

Which would make "String-Theory" more believable: a "String-Theory" based star drive, or a "String-Theory" based toothpaste?

"String-Theory" is supposed to unify the four quantum forces. Once you have gravity linked to the Electro-Magnetic-Weak force, you should be able to exploit the link to control gravity with electricity (IMHO, of course)...

"Honey? I need three more D-cells for my grav harness. Could you pick some up on your way home?"
 
gnome said:
I don't believe there's anything in String Theory or M-Theory that supposes such a trip is possible.

However, to be real science it ought to at least predict an observation... can anyone describe that aspect of it?
Click to expand...

an observable violation of the inverse square law at the microscopic level would be evidence to support a multi-dimensional hypothesis....

basically suggesting that gravity might be disapating into the postulated extra dimensions.....


TO SOME, it might seem that Eric Adelberger is on a wild goose chase. Not only is he trying to disprove Newton's law of gravity, which has withstood over 300 years of scrutiny, but for years now every experiment he has done at the University of Washington in Seattle has come up with zilch.

Despite this, Adelberger has no shortage of graduate students keen to help, even though they are all getting null results too. So what's going on - why do they bother? Because the first person to find what they are looking for will make history. Find the blip, and you have proved that gravity leaks out from our world into hidden dimensions.

It might seem like a far-fetched scenario, but it seems to be the best way to explain the strangeness of gravity, a force totally unlike the three others we have observed in the universe - the electromagnetic, strong and weak forces. For a start, every bit of matter, from the tiniest speck of dust to the greatest star, generates gravity and attracts every other thing. But its most curious aspect is its strength.

Gravity is vastly weaker than the other three forces. You only have to look at a fridge magnet to see that: even for a fairly heavy magnet, gravity's pull - which is also proportional to the enormous mass of the Earth - is as nothing compared with the attraction to the fridge door. Nobody has yet managed to explain the huge gulf in strength between gravity and the other forces.

Adelberger's search for an explanation began in 1998. That's when Nima Arkani-Hamed, now at Harvard University, Savas Dimopoulous from Stanford University in California and Gia Dvali of New York University came up with a hypothesis. The three theorists had been playing with the idea of extra dimensions, because modern theories that unite gravity and the other forces of nature often require that the universe has extra spatial dimensions too tiny for most experiments to observe (New Scientist, 29 September 2001, page 26).

snip snip

One of the predictions of the theory is that leakage into those extra dimensions might cause gravity to deviate from Newton's inverse square law. This law of gravitational attraction says that the mutual pull of two objects decreases in proportion to the inverse of the square of their separation. That's because the way gravity varies with distance depends on the number of dimensions the space has.

In three dimensions, the surface area of a sphere surrounding a point mass increases as the square of the radius of the sphere. The idea is that, since the total "amount" of gravity reaching successively larger spheres should remain constant, the strength of that gravity therefore falls off like the inverse of the square of the distance. In four dimensions the surface area of a sphere depends on the cube of the radius, in five it's the fourth power, and so on. So in higher-dimensional spaces, the force of gravity must dissipate ever more rapidly, which means it will no longer obey Newton's inverse square law, but some law in which its strength falls off far more sharply.
snip sip

So these extra dimensions might be accessible to experiments after all. But that's not to say they would be easy experiments to perform: gravity is so weak that it is extremely difficult to bring together enough matter to generate a measurable force at a few millimetres of separation. After all, you can't play around with things the mass of a planet in an Earth-bound laboratory. Nonetheless, Adelberger and his colleagues have slowly and surely been finding ways to put an upper bound on the size of the hidden extra dimensions.


snip snip

To look for gravitational anomalies, Adelberger simply sets the attractors rotating together. The rotation of the thin upper attractor alone would cause the pendulum to twist back and forth 10 times per rotation (each twist is around one ten-thousandth of a degree). That's because the holes in the plates and the pendulum act, mathematically, like negative masses, which you can think of as attracting each other. However, the rotation of the lower, thicker attractor - or rather its offset holes - compensates for this. "You can arrange things so the peak of the signal from one plate corresponds to the trough of the signal from the other, so they just cancel out," Adelberger explains.

The result is that the pendulum should not twist at all, provided gravity follows an exact inverse square law. If, on the other hand, a component of the gravitational force from the lower disc decreases more rapidly with distance, its effect on the torsion balance will be negligible, since it is further away. The forces will no longer cancel exactly, and the pendulum will twist.
snip snip

Torsion balances are not the only way forward. Groups at Stanford and the University of Colorado have constructed what amount to microscopic tuning forks made from single crystals of silicon. If you set one of these tuning fork vibrating and then bring a test mass up close to it, the gravitational attraction subtly changes the pitch of the tuning fork, and this change reflects the strength of the force. But again, errors can creep in.

Aside from eliminating stray vibrations, the experimenters have to watch out for electromagnetic fields and other effects. Even the ghostly Casimir force, caused by pairs of particles and antiparticles that spontaneously pop into existence out of the "empty" space of the quantum vacuum, is far greater than the gravitational force and must be carefully accounted for. Preliminary measurements have still revealed no evidence of any deviation from the inverse square law down to the 10-micrometre scale.
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http://www.newscientist.com/channel....100-the-mystery-of-disappearing-gravity.html
 
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andyandy said:
"An observable violation of the inverse square law at the microscopic level would be evidence to support a multi-dimensional hypothesis ... basically suggesting that gravity might be disapating into the postulated extra dimensions ..."
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Yeah, but ... supported hypothesis' are all well-and-good, but what practical applications could be derived? I have enough trouble finding my keys, without losing them in a multi-dimensional pocket!
 
A tricky part of waiting for a practical application is that due to marketing geniuses, many products will use the name of the new technology without actually being based on that technology at all.

For example, how many products had "Laser" in the brand name without having any lasers at all in their operation or creation. I fully predict that if the quantum computer is ever invented, that the major manufacturers will release their next generation of conventional silicon-based CPU's under the "quantum" brand.

So, looking even farther into the future, how do you know your Superstring Gravity Harness(tm) really has anything to do with Superstrings? :)
 
gnome said:
So, looking even farther into the future, how do you know your Superstring Gravity Harness(tm) really has anything to do with Superstrings? :)
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Uhh ... the way the optional parachute is attached to the harness?
 
The theory makes predictions, my main problem with it though is what happens if when they manage to test those theories what happens?

Last time there was flaw someone said ... oh they are just much smaller than we thought. It starts to stink of "curve fitting". There are enough degrees of freedom such that I don't know if it could really be disproven.

A secondary problem is that I don't think the language chsoen is appropriate. If it terms out the model predicts things correctly at these high energies I am not sure that it would be proof of more than 4-dimensions.

That is the short explaination, but I'm no expert.
 
Simple physics) It's obvious that everything is vibrating, otherwise everything would be dead. How does everything move around, with magic? Humans don't even know how it works, they are just guessing. How can they know how the Universe works if they don't even know how their own body works?

One movement sets off another movement. Energy gets transformed into heat and the heat affects the human body etc. It never stops. How can something start moving if the source isn't vibrating in the first place? Everything is the source and it's all vibrating.
The vibration can never be stopped, the same amount of vibration will always exist in the Universe, in some places more than others. That's why there is evolution, otherwise the whole Universe would be just a vibrating grid. It's not about the grid vibrating, it's about the interaction of the particles which sets off another motion. And how can the particles set off the motions if they aren't vibrating in the first place so they can hit each other? It's pretty obvious. You don't need to be a genius to figure that out.


Advanced physics) But how did it all start? It didn't, you are the source yourself and you are the one who set off all the movements when you were born, it can't be stopped.

Were you really born when you entered the human vessel or were you born before that? Just because you can't remember the time before that doesn't mean it didn't exist.


Truer physics) Everything exists which means that everything has and will exist. What you currently see is just a possibility in existence. There is no beginning or end, which means that there is no grid or vibrating particles, it's all in your mind.

There are no physics because there is no beginning. People try to explain why things work etc. But it's flawed from the beginning, something can only be explained if there's a beginning in existence, and that is not a possibility in the first place. For something to exist it needs to have existed in the first place. You can't just invent it like magic.

Nothing can be explained without the explanation being flawed in the first place.
 
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~enigma~ said:
Well there is FTL travel as far as light goes as can be seen in the experiment by Wang here

The experiment has been duplicated and done with different gases. others (most notably Gisin) have done other experiments that show entangled particles transfer "information" at speeds that dwarf light speed. But then again, this is quantum stuff and not string theory.
Click to expand...

Which is why I think SETI is doomed to fail. Any advanced civilisation won't be using light speed communications.
 
Walter Wayne said:
The theory makes predictions, my main problem with it though is what happens if when they manage to test those theories what happens?

Last time there was flaw someone said ... oh they are just much smaller than we thought. It starts to stink of "curve fitting". There are enough degrees of freedom such that I don't know if it could really be disproven.

A secondary problem is that I don't think the language chsoen is appropriate. If it terms out the model predicts things correctly at these high energies I am not sure that it would be proof of more than 4-dimensions.

That is the short explaination, but I'm no expert.
Click to expand...

One way of thinking of it... (which is the way chosen by Stephen Hawking if I explain it right...) is called "Scientific Positivism" ... which instead of attempting to encompass the idea of what's "real" instead simply asks the question of how well the model fits known facts and can be used to predict new observations. Basically, whether the theory is useful as a description is more important than whether "superstrings" really exist. In fact there may be more than one valid model for the same observations...
 
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