Gravity's Rainbow

There are, as far as the layman is concerned, two kinds of scientific truth. At one end of the spectrum -- the gamma ray end, if we use the electromagnetic spectrum as a model -- there are the kinds of concepts we associate with science's grand design, the truths which permeate the dark depths of the unknown universe. These are the terrifying, metaphysical truths: unifying cosmic theories, the afterlife, quantum mechanics. Entire disciplines orbit these, while the average person has only a nebulous idea of what they even represent. On the short-wave radio end, there are those forces governing the makeup of our life, things like the atmosphere of planet Earth or the basic laws of physics. A lot of people think they have a firm grip on these truths -- we learn them in grammar school via dinky experiments and chalkboard lectures.

These concepts comfort us, even if we don't particularly understand them. Take gravity, for example. Its effects are easily measured and simple to calculate, yet they are also endlessly convoluted and vague, to the point where gravity's practicality in the everyday almost seems a wondrous coincidence. We all know what gravity does: it keeps us together, keeps our planet in orbit, and keeps the proverbial apple falling onto Newton's head. However, not even the most Nobel-winning physicist could give a fully comprehensible explanation of just how it does all of those things. Albert Einstein pulled the most impressive coup in scientific history by postulating -- without any experimental evidence or theoretical precursors -- that gravity is the product of the warping of the space-time continuum by large objects. As planets and stars move through the cosmos, Einstein suggested, they ripple the very fabric of space, sending off waves of gravity -- much like a swimmer passing through a body of water leaves a wake of ripples.

Great, so gravity is a wave, not a force. Do we have any proof? Surprisingly, no -- for a force (err, wave) which literally permeates every dimension of our universe, gravity is hard to understand and even harder to detect. Gravitational ripples coursing through space are tremendously weak; even those emitted by the violent formation of supernovas are only tiny atom-sized wrinkles by the time they make it to Earth. Although secondary evidence abounds for the existence of these waves -- the shrinking orbits of some pairs of neutron stars can only be explained by a loss of energy through gravitational waves -- direct observation of this phenomenon has long been considered an impossibility. Not even Einstein (who was, to say the least, a dreamer) envisioned a detector which could parse the tiny effects of gravity waves from the other noises bombarding Earth. After all, how in the hell do you separate a microscopic pulse of gravity (one 10^-15, to be exact, about the size of an atomic nucleus) from, say, a roar of seismic activity, the pounding of the ocean, or the movement of cars on a nearby freeway? I know that science is basically magic, but come on -- this is one is impossible. For decades, not even the most foolhardy of physicists even saw the point in trying.

That is, of course, until "dark matter" came along. Dark matter (along with dark energy, dark galaxies, and Los Angeles) is a completely mysterious substance now known to make up over 90% of the Universe, which leaves us and our high-falutin' observatories looking mighty stupid. Along with black holes and pretty much everything else that is deemed important in modern astronomy, dark matter cannot be seen with a telescope. The only reason we know it exists is due to a staggering discrepancy between how much the Universe weighs and how much we know it should weigh; the Universe is much, much heavier than the sum of everything we know to exist within it. Hence: something else, something invisible, is omnipresent. Dark matter.

Unless someone devises a way of detecting whatever dark matter emits, research in this all-important domain (one at the gamma ray end, if you will, of the spectrum of scientific truth) will come to a standstill. What astronomers desperately need is machinery that can feel outer space instead of seeing it. Something that could detect, for example, the gravitational ripples emitted by dark matter.

Enter LIGO: the Laser Interferometer Gravitational-Wave Observatory. The $300 million project, a product of National Science Foundation funding and over 25 years of construction and design, is the most sensitive American gravitational wave detector ever built -- nay, the only American gravitational wave detector ever built. It consists of an absurdist two-part compound, one half of which lies 200 miles from the Pacific in southeastern Washington (the other is in southern Louisiana). Each site is made up of two 2.4 mile-long perpendicular arms and a huge laser interferometer, which splits beams of light and sends them ricocheting back and forth until they lag in speed just enough to announce the presence of a nanoscale gravity beam. Measurements made at the Washington LIGO are cross-referenced with similar measurements taken at the Louisiana LIGO 2,000 miles away.

Friends on the short-wave end of the spectrum, don't worry: I do not understand it either. What is essentially happening at LIGO (where, incidentally, no gravitational waves have yet been detected) is that scientists are using one near-mythic unproven scientific idea to measure something equally fantastical and invisible. It's like using magic and dream-catchers to prove the existence of aliens and crystals, but then again, I'm just on the short-wave end of the spectrum.