Having no formal training in much of anything except English literature and the martial arts, I tend to be an outsider in disciplines relating to science, religion, politics, and other art forms. That means I am not wedded to any particular doctrines or viewpoints. But I am interested enough, and read constantly—if haphazardly—enough that I tend to have opinions based on some knowledge if not deep, formal study. This means that, in the eyes of the conventionally trained, I am a dilettante and a meddling fool, while to the lay person and the general public, I am more of a voice lost in the wilderness. For myself, I am a contrarian who has not drunk the Kool-Aid of the formalists.1
As a science fiction writer, this can be awkward if not treacherous. I have to know the general principles of science, understand the nature of scientific inquiry, and be able to identify faulty thinking. But unlike any formally trained scientist, I must also be able to color outside the lines and engage my imagination in speculations beyond the limits of the known. My stories have to take us from what is already proven to what is possible without veering into what has already been shown to be dead wrong.2
A rich field for this sort of speculation lies in astronomy and its co-discipline of cosmology. We humans have been able to learn a remarkable amount about the universe, its origins, and its destiny just by looking outward from the surface of this planet with our eyes, our optical instruments, and now with technologies that can look beyond the spectrum of visible light into all the frequencies of photon radiation and measure a number of flying particles as well. We can analyze these energies, both on the Earth’s surface and from probes in intra-solar space. But the the more we look, the more we find questions and contradictions. It’s a place rife with speculation and theory.
One of the theories has to do with gravity. We understand it pretty well at the scales of human beings, planets, and stars—or at lease we think we do. But at the smallest scale, that of the elementary particles, gravity seems to have no effect. And at the largest scale, that of galaxies and galactic clusters, gravity seems far stronger than we can account for with the visible matter that makes up these objects. If we judge by the brightly shining stars we can see in the average galaxy, plus the unbright stuff we can infer from our own solar system—planets, moons, asteroids, comets, and dust, all of which are just a fraction of most any star’s mass—then our best calculations cannot account for the motion of the stars gravitationally bound in the galaxy.
With our current understanding of gravity and mass, the visible stars in a galaxy like our Milky Way or our sister Andromeda should move at varying speeds. Those in close to the center of galactic mass should trace their orbits rapidly around the dense galactic center, while those farther out should appear to move more slowly, taking more time to complete their longer orbits. This is the pattern in our solar system, where the inner planets orbit the Sun’s mass in a hurry of days or the Earth’s own year, while the outer planets saunter along in decades and even centuries. For visual effect, imagine chips of wood circling a maelstrom: those closer to the center move faster than those out on the edge.
But this is not what we see in most galaxies that have a pronounced spin. Instead of moving independently, the stars appear to move together in a flat rotation, as if they were painted in a fixed pattern on a spinning disk. It’s almost as if the mass of the galaxy increases with a star’s distance from the center. None of our calculations of the probable amounts of planets, dust, and cold icy bodies can account for this extra mass. No amount of mass attributed to a central black hole—the likes of which we now can predict lives at the heart of every galaxy—accounts for this extra mass, either.
Another observation suggests this extra mass as well. All massive bodies bend spacetime—that is, the effect of bodies existing and moving in space over time—and cause light rays to bend around them, either a little or a lot, depending on the amount of mass. Einstein’s prediction of this warping effect was confirmed almost immediately during the next full eclipse of the Sun: stars that should have been invisible because they lay behind the Sun’s disk were actually detected just outside its edge. Our Sun’s great mass and deep gravity well was bending the light rays from those more distant stars on their way to Earth. In the same way, galaxies that lie between observers on Earth and more distant galactic objects bend the light from those objects, so that they may appear offset from where we know they actually lie. In some cases, their shapes are distorted into a halo image surrounding the intervening body. This is called “gravitational lensing.” In all galactic cases, the amount of gravity required to achieve the effects we see is more than we can measure in just the stars of the lensing body.
To account for this flat rotation around a galactic core and its increased lensing power, many cosmologists propose the existence of “dark matter.” They envision this as some kind of invisible mass, perhaps a particle, perhaps not, that sheds no light and does not interact—except gravitationally—with the kind of matter that we know as atoms and their constituent particles.3
In some early theories, dark matter was proposed as an excessive number of normal interstellar bodies like brown dwarves, neutron stars, and black holes that just don’t emit much light. The common name for these objects supposedly scattered in a galaxy’s farther reaches was massive compact halo objects, or MACHOs. Sometimes they are called a robust association of massive baryonic objects, or RAMBOs. Although we haven’t seen evidence for enough of these dark bodies, when you add in a measure of heavy gases in a galaxy, you … still don’t come up with enough mass to satisfy observations.
The most common theory is that dark matter is composed of WIMPs, weakly interacting massive particles, which lie outside the Standard Model of quantum mechanics. They fall into the category of non-baryonic matter—that is, not like our protons, neutrons, electrons, neutrinos, photons, and other identified particles.4 These non-baryonic particles are also identified as “cold,” “warm,” or “hot,” based on how fast they are moving and their effect on the early universe. So, if you follow the WIMP particle theory of dark matter, rather than the MACHO brown dwarf theory, you are opting for massive particles that we cannot see or detect but that pass through every square inch of our bodies, the Earth, and everything else every second. They have no effect on us, except for their mass and inherent gravity—which would add to the gravity effects we can already account for on the local level pretty well from the masses of the Sun, the Earth, the Moon, and other nearby bodies. Uh-huh.
The more I think about this, the more I am reminded of past theories about phantom substances created to account for unexpected experimental results.
Early naturalists, before the development of commonly accepted principles of chemistry and molecular structure, observed fire consuming a log of wood and reducing it to a pile of fluffy ashes, which have not a tenth of the wood’s weight and content. To account for the missing mass, they proposed that burning released an invisible substance called “phlogiston,” which if recaptured from the air could be reconstituted with the ashes into new, hard wood. Now, of course, we understand that plants and other organic matter are rich in hydrocarbon molecules, which with proper heating in the presence of oxygen can be transformed into carbon dioxide gas and water vapor, leaving only the mineral residue from the wood as ash. A universal fire-like substance like phlogiston is not needed in this process.
Early physicists, before the development of quantum mechanics and special relativity, believed that light traveled in waves. Light couldn’t be a particle, because particles traveled in straight lines, like hurled rocks and fired bullets. Since ocean waves represent regular motion in water molecules, they proposed that light waves were regular motion in an invisible substance—not air, because light also traveled in the vacuum of space—that permeated the cosmos called “luminiferous aether.” It took an experiment by Albert Michelson and Edward Morley in 1887 at Case Western Reserve University in Cleveland to show that aether could not exist. If this substance was some kind of universal fluid, then the Earth must pass through it like a fish through water. In the experiment, Michelson and Morley split a beam of light at right angles and measured its travel in two different directions. Clearly, if light was a wave in aether, then the beam traveling in the direction of Earth’s passage, and so encountering a “headwind” in the aether, would be slower than the beam crossing the Earth’s passage and so encountering no headwind. They conducted their experiment on a rotating table, to allow for all possible angular effects. When light showed no preferred direction, they dismissed aether as a substance. This opened the possibility that light was a quantized packet of energy—equivalent to a lightweight particle, the photon—that travels at a constant velocity following an oscillating path whose frequency corresponds to its inherent energy.
Now, I may be indulging in faulty reasoning here. But if the phantom substances phlogiston and aether—materials created to explain our imperfect understanding of then-current observations—were later proven wrong, then might not the phantom WIMPs of dark matter also be an easy first approximation of a much more complex situation? In this I am reminded of the scene in one of my favorite movies, Aliens, where the slacker soldier Hudson is tracking the predator aliens with a motion detector. When the device shows them actually inside the room where the group has barricaded itself, Hudson bawls, “Hey, this thing ain’t reading right!” And the more dependable Corporal Hicks replies, “Maybe you aren’t reading it right.”
Maybe we aren’t reading the nature of gravity right. Other approaches have been proposed to account for the missing mass on a galactic scale. One is that the mass might be found in extra dimensions, but this is hardly better than massive, non-interacting particles. “Other dimensions” is becoming the broom closet into which physicists sweep any inconvenient observation that does not jibe with current theory. A possibly better approach is that the birth of the universe may have distorted and deformed the shape of quantum fields as we understand them. This is getting closer to an admission that the universe is strange and we haven’t worked out all the strangeness yet. A third approach is to admit that, as Einstein’s theories about time, space, and gravity enlarged upon those of Newton, perhaps at the galactic scale we are waiting for a new physicist to propose and prove further modifications to, and a refinement of, our understanding.5
I, for one, am more comfortable with that—with knowing our knowledge is incomplete and waiting to be furthered—than with accepting the existence of an invisible particle we can neither detect nor measure. I don’t begrudge the astronomic community spending money on search for this invisible particle, just on the off-chance it might exist. But I’m not about to become wedded to the idea as some kind of orthodoxy.
Our understanding of the universe is still in its infancy. As a sapient species, we have a lot of growing up to do. I can accept that.
1. My first publisher, Jim Baen, who was a contrarian himself, advocated this position. “Contrarians always win,” he once told me. My experience has been that, at least, they don’t get trampled by the crowd.
2. When I was first starting out as a writer, I submitted a short story—one of my very few, for I am by trade and inclination a novelist—about a harmless looking glass vacuum bottle, such as you might use for hot coffee or soup. The point was that the cap was stuck on tight and, when the thoughtless protagonist finally succeeded in opening it, the vacuum inside began sucking first the air, then all the matter out of first the room and then the universe. When the magazine returned this story, the kindly editor told me that science fiction about dead theories like luminiferous aether just don’t work. Being adaptable and easily trained, I have since been careful—or at least I hope I have—not to roam into the dead lands of bogus science.
3. Astronomers also speak of “dark energy,” which has to do with the fact that the universe seems to be expanding far more rapidly than you would expect from the impetus given by the Big Bang. Dark energy outstrips the tendency of the universe’s mass—even accounting for that dark matter—to pull everything back together. But let’s save dark energy for another time.
4. Ironically, the term “baryon” has its roots in the Greek word for “heavy.” So while normal baryonic matter is “heavy” stuff, this non-baryonic matter—which supposedly accounts for most of the mass in the universe—is the “non-heavy” stuff. Weird.