Gravity Probe B,
The Large Hardron Collider and
The Theory of Everything
by Paul Bird
It is September 2005 as I write this article and in a few years time we should have answered most, if not all the outstanding problems of physics: How to formulate a quantum theory of gravity, are there any new elementary particles to be discovered, why do some particles have mass?
Several experiments are under way to decide these questions. One of them is Gravity Probe B, which is a satellite containing six gyroscopes positioned on each side of a cube inside superconducting material. The tilt of these gyroscopes attempt to measure the geometry of space itself. Einstein postulated that space-time was curved in the presence of massive objects. Was he correct? By mid 2006 we shall find out. They have already finished collecting the data, they are now at the stage of analysing it all.
Is space-time curved or flat?
Experiments have been carried out in order to observe the curvature of space. For example Sir Arthur Eddington's observations of star positions close to an eclipse of the sun. However, people have pointed out that the experimental error involved due to factors such as turbulence in the atmosphere have left some people unconvinced. Other experiments have been performed to indirectly test Einstein's theory of curved space-time but none so far with the supposed accuracy of Gravity Probe B.
The reason it is so hard to perform an experiment that will test Einstein's theory is that it involves two important constants; the speed of light which is very very large by everyday standards; and the gravitational constant which is very very small. So combined together the effects that we are looking for are minuscule to say the least.
What difference does it make?
If space really is curved by matter, as Einstein predicted, then this means that light really does bend around massive objects. It would mean that, for small volumes of space, gravity really is equivalent to acceleration.
If space turns out to be flat after all then this means that objects at speeds close to the speed of light feel the force of gravity less than stationary objects due to (special) relativistic effects. This would mean, for example, that objects made of different substances could be affected by different amounts by gravity. However, even this difference would be minuscule in all but the most extreme cases.
New Particles
By mid 2007, the Large Hadron Collider (LHC) will begin its first particle collisions. Since no one has ever collided particles at these energies before it is unknown territory for everyone. Of course people have their predictions about what the experimenters are going to find, such as higgs, quarks, squarks, and so on. Some people have suggested that they might create a black hole that will escape and destroy the world!! Sounds unlikely but who really knows? Only time will tell...
My Predictions
Over the past few years I have developed my own ideas about what we should find. I favour the view that space is flat. My main reason being that in the four-dimensional space-time that we live in, a curved space-time theory of gravity can not be reconciled with quantum theory. Hence I predict that Gravity Probe B will find that space-time is flat. I have to admit, this is not a view shared by much of the physics establishment.
The Theory of Everything
So what will the final theory of everything look like exactly?
My prediction is that the Theory of Everything is given by the following action:
Which is the simplest chiral four-dimensional supersymmetric theory of flat-space gravity which satisfies the power-counting renormalization test (to put it simply!). To get what particles it predicts, we simply expand out the scalar superfield. We see that it contains within it the electron, neutrino, photon, weak-vector bosons, scalar-graviton, higgs, along with a some more unknown particles. What it doesn't include are quarks, gluons, or more than one generation of particles. My prediction is that these models will have to be abandoned in favour of particles from this superfield expansion.
As an example, the model of hadrons being made up of quarks might have to be replaced with a model of hadrons being made up of leptons held together by some yet unknown charge-changing force. Experimentally this would appear that the charges of the constituents had charges of 1/3 or 2/3. To test this theory we would expect that the average nucleon mass would equal three times the average lepton masses. Which is equivalent to saying that:
which, remarkably, matches up very well indeed. The smallness of the masses of the elementary particles such as the electron can be linked, as Dirac suggested, to the smallness of the gravitational constant which in turn can be linked to the largeness of the age (or size) of the universe.
I have yet to work out all the details of the theory as of yet, especially how to get the correct masses for all the particles but I believe I am on the right lines as I hope the experiments over the next few years will confirm.
Unanswered Questions
One of the most important unsolved questions of physics, I believe, and one that will surely unlock many mysteries is why the three charged leptons (electron, muon and tau) have mass ratios of approximately 1:207:3477. No one knows the answer to this although interestingly, the ratios 26:56:86 :: 0.85:207:3477 comes pretty close - except the electron mass is lower than it should be. However this is pure speculation and not to be taken too seriously! Those that have attempted to answer this question believe that these masses must be the eigenvalues of a mass-matrix though they haven't agreed on what that matrix should be. I believe that only using the Theory of Everything itself will anyone be able to determine the answer to this question.
References
An introduction to flat-space gravity (or Scalar Gravity) can be found at:
1. An Introduction to Scalar Gravity
This e-book has not been updated recently as there has been trouble uploading onto the server but it is still the most popular introduction to Scalar Gravity on the Internet.
This is a website for the public interested in the Gravity Probe B experiment. Results expected mid 2006.
This is a website for the public interested in experiments at the LHC. Tests begin in summer 2007.