If we are light, why aren't we shining?

kw: book reviews, nonfiction, physics, theories

If you had a fast enough camera, with sharp enough "vision", a snapshot of a proton (the hydrogen nucleus) might bear some resemblance to this artistic depiction. How fast and how sharp? A full cycle (not a rotation but something roughly similar) takes about 10^-24 seconds, so the shutter speed needs to be 10^-26 seconds or faster, and the size of the whitish enveloping sphere is about 10^-13 cm, so the "camera" needs to resolve details in the 10^-15 cm range. Strangely enough, that kind of camera would not be really, really tiny; it would be huge. A particle accelerator, which Dr. Frank Wilczek calls a "superstroboscopic ultramicroscope", with a size of twenty kilometers or so, is expected to do the trick: the Large Hadron Collider, which is soon to come on-line. Its detector is not a postage-stamp-size chip like the one in your digital camera, but a complex the size of a five-story building (or several thereof).

Such a "camera" puts the energy of a small stick of dynamite into two clumps of protons (a few million per clump) by zipping them around in a huge circle in opposite directions, and letting them collide head-on inside a building-size detector. The resulting "picture" is not a 10-Megapixel or so image, but a clump of data thousands of times that voluminous, perhaps a terabyte, with which one may determine where the quarks and gluons (see next paragraph) are situated (or were, before everything went Wham). In the realm of subatomic physics, you have to destroy a proton to figure out how it was put together. To get reliable results, you have to do it many times. Luckily, there are lots of protons on hand.

In the image, the three colored globes represent quarks, and the smaller two-colored items represent the appropriate gluons that bind the quarks together into a proton, in this case. Other configurations result in other kinds of particles. The quarks are said to exchange the gluons and thus remain bound together as a proton.

A similar image that showed the particle physics explanation of the binding of an electron to the proton to make a hydrogen atom would show two small spheres of different sizes exchanging a pale wisp that represented a photon, in such a way that they were kept together at a distance about 100,000 times greater than the scale of the image above.

There are two more kinds of binding that we have some idea about. One has its components in pairs rather than triplets, and describes the weak interaction that can change a proton to or from a neutron. The other has, perhaps, a single binding particle, that interacts with both "matter" particles and their energy content, and literally binds the universe together. It is called the graviton. "It" may consist of more than one "thing"…nobody knows yet.

In Dr. Wilczek's book The Lightness of Being: Mass, Ether and the Unification of Forces, he describes the theories behind the understanding of these forces. This popularization of the deepest concerns and strongest theories of physics is written for the educated amateur. I have to confess, I got lost time and again; perhaps I am not a sufficiently "educated" amateur. But I am not totally bereft of understanding. My opening paragraphs outline major elements of the theory of forces, most of which I learned from this book. And the way of thinking and explaining the author uses helped me work out a partial understanding of something I've asked a few scientists about, though none has answered my e-mail.

As simply as possible, I've asked this:

Black holes permit the escape of nothing, not even light (photons), because the gravitation potential below the event horizon of a black hole exceeds the speed of light. If gravity is quantized, and is carried by a particle (which we've chosen to dub the graviton), will not the intense field trap such particles also? If so, how does any gravity escape from the black hole to mediate its attraction for the objects that continue to fall into it, and thus make black holes such as Cygnus X-1 detectable?

I expected an answer that invoked the general theory of relativity, in which gravity is considered a distortion of space-time by concentrations of matter and energy, such that the inertial paths of objects are curved in the way we would calculate for a centrally-directed "force". However, general relativity conflicts with any quantum theory of gravity in which its effect are attributed to particles.

I see that both sides, relativity and my concept of quantum gravity, are incomplete. Regardless of what the relativistic explanation might be, and regardless of how gravitational quanta might be reconciled to it, such a graviton , which I will call the G particle, must have these characteristics:

• G is a boson, like the photon, the gluon, and the W and Z bosons that ferry the Weak force about.
• G is massless, like the photon, so it propagates at the speed of light, c.
• Because both masses and energy are subject to gravitational attraction, the G particle carries no energy, and is thus not subject to gravitational attraction—else it could not escape a black hole.
• G probably has spin zero, like the photon.
• Whereas the photon can mediate both attraction and repulsion, because it is subject to (or carries) electrical charge, G is "blind" to electromagnetic forces and to the "color" charges of both gluons (dubbed either r, g, b or r, w, b) and W/Z bosons (with colors g and p, to make them distinct from gluon colors). Thus G can mediate only attraction—unless it is somehow also "visible" to the "dark energy" that is accelerating the universe, and mediates repulsion for whatever it is that the term "dark energy" refers to!

Take this as a somewhat chagrined testimony: There isn't really that much math in the book, but most of the author's math left me in the dust. However, he is a great explainer, and is able to transmit the "shape" of a concept even when you don't grasp the math that he finds so beautiful. Much of the material is based on the discoveries in quark-gluon interactions that led to his Nobel Prize five years ago. His colleague Richard Feynman, upon being asked "What did you do to earn the Nobel Prize", answered, "Buddy, if I could explain what I did in one minute, it wouldn't be worth a Nobel." It takes considerably more than one minute to grasp some portion of Dr. Wilczek's explanations (it took me six days), but I learned enough to understand how it is worth the Prize.