The Grand Illusion
When a science fiction writer starts pondering the basics of science, especially outside the confines of a story or novel, the results can be ugly. But…there’s this question, and a lot of them that arise from it, or cluster around it… or something.
Does light really maintain a constant speed in a vacuum and away from massive gravitational forces?
Most people, I’m afraid, would respond by asking, “Does it matter?” or “Who cares?”
Physicists generally insist that it does, and most physics discussions deal with the issue by saying that photons behave as if they have zero mass at rest [and if I’m oversimplifying grossly, I’m certain some physicist will correct me], which allows photons to travel universally and generally invariably [again in a vacuum, etc.] at the speed of light, which is a tautology, if one thinks about it. Of course, this is also theoretical, because so far as I can determine, no one has ever been able to observe a photon “at rest.”
BUT… here’s the rub, as far as I’m concerned. Photons are/carry energy. There’s no doubt about that. The earth is warmed by the photonic flow we call sunlight. Lasers produce coherent photonic flow strong enough to cut metal or perform delicate eye surgery.
Second, if current evidence is being interpreted correctly, black holes are massive enough to stop the flow of light. Now… if photons have no mass, how could that happen, since the current interpretation is that the massive gravitational force stops the emission of light, suggesting that photons do have mass, if only an infinitesimal and currently unmeasurable mass.
These lead to another disturbing [at least for me] question. Why isn’t the universe “running down”? Don’t jump on me yet. A great number of noted astronomers have asserted that such is indeed happening – but they’re talking about that on the macro level, that is, the entropy of energy and matter that will eventually lead to a universe where matter and energy are all at the same level everywhere, without all those nice gradients that make up comparative vacuum and stars and planets and hot and cold. I’m thinking about winding down on the level of quarks and leptons, so to speak.
Current quantum mechanics seems to indicate that what we think of as “matter” is really a form of structured energy, and those various structures determine the physical and chemical properties of elements and more complex forms of matter. And that leads to my problem. Every form of energy that human beings use and operate “runs down” unless it is replenished with more energy from an outside source.
Yet the universe has been in existence for something like fifteen billion years, and current scientific theory is tacitly assuming that all these quarks and leptons – and photons – have the same innate internal energy levels today as they did fifteen billion years ago.
The scientific quest for a “theory of everything” tacitly assumes, as several noted scientists have already observed, unchanging universal scientific principles, such as an unvarying weak force on the leptonic level and a constant speed of light over time. On a practical basis, I have to question that. Nothing seems to stay exactly the same in the small part of the universe which I inhabit, but am I merely generalizing on the basis of my observations and anecdotal experience?
All that leads to the last question. If those internal energies of quarks and leptons and photons are all declining at the same rate, how would we even know? Could it be that those “incredible speeds” at which distant galaxies appear to be moving are more an artifact of changes in the speed of light? Or in the infinitesimal decline of the very energy levels of all quarks, etc., in our universe?
Could our universe be running down from the inside out without our even knowing it?
As I understand the matter from the physics/quantum chemistry classes I’ve taken, at some fundamental level, energy and mass are supposed to be the same thing. Hence Einstein’s famous E=mc^2 and various other matters. The idea there is that matter is just an exceptionally dense/stable form of energy. Which makes me think that it’s dense enough that we can measure that density as mass, which /also/ makes me think that all forms of energy should have something corresponding to “mass”, even though it might be unbelievably small. Further, gravitational effects are (quadratically?) proportional to the mass of each object involved, so a photon might have such small mass that we can’t detect such mass except for ridiculously strong gravitational fields.
This seems to be consistent with what I know about gravitational lensing and black holes and the like, though I freely admit my theoretical physics knowledge is less than stellar.
As for energy on the “matter” level running down…It seems unlikely that everything would run down at the same speed, as it were. Of course, perhaps in such a small segment as our solar system that might work…But basic quantum mechanics suggests that there are some absolute minimums for the acceptable energy levels of certain forms. I don’t know, really, but this is going to be food for thought for some time…Thanks!
You hinted at some of these ideas in “The Eternity Artifact”. Does this mean in the future you may have another “novel” idea?
Enjoyed TEA. Found it more entertaining the second time around. I always enjoy your hard SF because so few do it well these days.
Hi Mr. Modesitt. I bought a copy of Imager last week. I already had all your Recluce books except Arms-Commander, but I prefer mass-market paperbacks because of their smaller size, so I have to wait for the release.
Yes, light travels at c, always, relative to anything that doesn’t travel at c, in the reference frame of the thing that doesn’t travel at c. No one has ever seen a photon at rest, and no one ever will. In its own reference frame, a photon crosses no space and experiences no time. It’s emission and absorption are simultaneous events from the photon’s point of view.
The familiar expression E=mc² is incomplete. The full form is E=√(m²c⁴+p²c²). Energy equals the square root of the sum of two products. One product is mass squared times the speed of light to the fourth power. The other product is momentum squared times the speed of light squared. For matter particles, like a neutron, the first term usually comprises most of the sum. For light, m=0, and the latter term comprises the entire sum.
I’ll answer your question about why sufficiently strong gravity can confine light. Gravity is (directly) not a force between two particles. It’s a relationship between mass and space. A mass curves the space around it, and the motion of any nearby masses responds to the adjusted shape. It’s a reciprocal interaction, of course. The 2nd mass is also doing the same thing, making adjustments to which the first (and third, and fourth, etc.) mass responds to.
If a mass is dense enough to curve space enough, it will pinch itself away from its parent spacetime. The partition is called an event horizon, which isn’t so much a wall as it is a topological warp.
Someone who falls toward a planet at first sees himself approaching a sphere (or, in cross section, a circle). The solid angle blocked by the sphere is a cone of less than 2π steradians. As the faller approaches the ground, this cone grows fatter. The horizon “rises” around him. At the moment he goes SPLAT (or just before), he sees opposite sides of the horizon separated by 180° or almost.
But someone who falls toward a black hole has a different experience. The event horizon reaches that 180° spread somewhat BEFORE the faller gets to it. As the faller continues to approach the event horizon, it mounts up above him, higher and higher. He still isn’t past it, however. By looking back outward, the faller sees the universe through a cone of rapidly decreasing solid angle: it’s getting narrower. The moment the faller crosses the event horizon, the cone pinches shut, and there is no longer any direction available to him which leads back to the universe from which he came.
Once inside the black hole, it no longer seems as if the faller is approaching the center of anything. Rather, it appears to him that he is motionless while the walls of his new spacetime environment come crashing down on him.
So, no. Photons have no mass, as long as they are photons. They have momentum h/λ, and there are natural processes (like pair production) that can shift the energy from momentum to mass. But once that happens, the energy isn’t making a photon anymore.
The universe as a whole is running down, in the sense that energy is spreading out of ordered states into relatively disordered ones. The forces confine energy to order a bit, but they do a lousy job of confining in the long run, because the energy always gets away from order into disorder.
But quarks and leptons have a better guardian. Quantum rules specify how they may exist. Think of them as “integers” and of your question as amounting to asking why they don’t have a string of random decimals behind the point.
Now, there is a chance that the universe is running down in another way. Other than by entropy. Consider entropy to be the “Second Law of Thermodynamics” way for the universe to be running down.
Is also a “First Law of Thermodynamics” way for the universe to be running down. One that might be hard to notice? Sure. The First Law basically pertains to the conservation of energy, just as the Second Law pertains to entropy. It might be the case that photons don’t, or don’t always, have the exact same amount of energy when they are absorbed as they had when they were emitted. Not even if the absorber is at rest in the emission frame of reference. Perhaps there is a quantum process, involving vacuum energy, that bleeds a little of the photon’s energy away. From the photon’s point of view, since it does not observe the crossing of space or the passing of time, the only thing of note is that it fissioned, with some of the energy remaining in our universe, while a bit of it went… somewhere else.
Where might that somewhere else be? Well, universes are analogous to black holes themselves, so maybe the missing energy reappeared outside our universe as external Hawking radiation. Just a speculation, of course.
I don’t think you answered the question as to why quarks and leptons don’t lose energy. Defining them as integers is merely saying that, by definition, they don’t lose energy. That doesn’t say why, and I’m rather skeptical of mathematical tautologies.
Okay, I’ll try again. In quantum mechanics, every kind of elementary particle is a wave function. In bound systems of more than one particle there will be quantized energy states in which they may relate to each other.
Quantized energy states are identified by quantum numbers, and quantum numbers are integers. Particles in a bound system can’t have just any old value of potential energy with respect to each other, but must accept values corresponding to a set of integers. (And for Fermions, which electrons are, the exclusion principle forbids any two in the same bound system from having the same set of quantum numbers.)
Strictly, no particle is alone. An “isolated” electron, say, still interacts with the virtual particle dipoles that emerge and disappear in vacuum. Vacuum interactions are responsible for splitting into narrow doublets atomic lines that would otherwise be singular. (Search Wikipedia for “Lamb shift” and “vacuum polarization.”)
It isn’t known why electrons (for example) have the mass (i.e., energy) they do. But physicists are reasonably sure that each electron in its intrinsic properties is indistinguishable from any other.
Electrons do occasionally gain or lose kinetic energy by moving faster or slower than before, or potential energy by shifting to a tighter or looser force relationship with another particle. But nobody has ever shown, as far as I know, that an electron can vary in rest energy.
Leptons and quarks are probably standing waves, which means that a whole number of cycles would be necessary so that the particle would not destructively interfere with itself.
Mr. Modesitt,
I don’t know if you’ll see this comment, due to the age of the original post, but there are two basic ways, given what we know about physics to date, that the universe can run down.
The first depends on the universe being closed, i.e. what we can see is all there is and that’s it. In this case, it’s similar to a balloon in an infinite vacuum, the gas expands infinitely far from the source. The total energy remains the same, but the gas particles are so far apart from each other that there’s basically no local energy of attraction, and the gas particles just keep on going. This is the heat death of the universe, and it’s the end result unless something really exotic does lie in gravitational theory in our future, since no known force internal to such a system can pull it back together once the expansion starts. This is partly why astronomers and cosmologists going back to Einstein keep getting worked up about the fact that all observations to date indicate that the expansion is accelerating as we go along. It’s consistent with Newton’s theory of gravitation as the limit of General Relativity in small masses.
The second way that the universe could be running down in energy is if the system is open, rather than closed. In that case, given what we can observe, it would mean that there is effectively a thermostat relationship between our local universe and “something else”, whatever that might be. The mechanism would be purely speculative, though of course black holes would be the immediate suspect. Hawking radiation, if observed, might contradict this as a mechanism, though, because it indicates that the black holes are leaking their energy back into our universe, not somewhere else.
Thank you… and I did see it.
Mr. Modesitt,
I realized that I could have been more specific in addressing the question that you were asking. There are some astronomers and cosmologists that believe that their observations support a decrease of the constants of the physical universe, like the cosmological constant and the speed of light, that would indicate that things are running down. If we were to take this as a given, and assume that it’s on the quark level that the mechanism is operating, then one way that it could be doing so is by something similar to a thermostat, in which whenever a fundamental particle is created or annihilated in the vacuum, it can carry energy with it, and this energy is in some way coupled to a larger, macro universe that contains our observed universe within it. If that were true, what it would mean is that the thermostat itself is winding down over time, and energy is bleeding out in infinitesimally tiny amounts with these fundamental fluctuations on the Planck scale.
That would ultimately mean that we would have to have some knowledge of what the macro universe is doing, and why. One interesting thing about something like that is that it would imply that the boundary of our universe with the outside is on the tiniest possible scale, and present everywhere in the universe simultaneously, wherever a fundamental particle is found.