"Light"
"Consider light," the old man said. "Our world appears infused with light's energy. But what is light?"
"It's made of photons," I said, thinking that was a start. By then I should have known better. I think he ignored my answer.
"If you were in a spaceship racing a beam of light, and you were moving at ninety-nine percent the speed of light, how much faster would the light be?"
"About one percent of the speed of light, obviously. I don't know the miles per hour."
"Not according to Einstein. He proved that the light beam would be faster than your rocket ship by the speed of light, no matter how fast you are traveling."
"That doesn't make any sense. But it sounds vaguely familiar. Did he really say that?"
"Yes, and it is accepted as fact in the physics world."
"That's, ridiculous," I said. "If I'm traveling ninety-nine percent as fast as the light beam, in the same direction as the light, the light beam can't be faster than me by the same speed as if I weren't moving at all."
"It's ridiculous indeed. But scientists claim it is proven."
"What if two rocket ships were racing the light beam and one was ninety-nine percent as fast as light and the other was fifty percent as fast? The light can't be faster than both of them by exactly the speed of light."
"And yet it would be."
"Okay, that's just plain crazy," I replied. "You see, the light beam should be speeding away from the slower ship. That's common sense."
"It's common and it's wrong, according to scientific tests," he argued. "It turns out that time and motion and the speed of light are different for all observers. We don't notice it in daily life because the difference is very slight for slow-moving objects. But as you approach the speed of light, the differences become evident.
"It is literally true that no two people share the same reality. Einstein proved that reality is not one fixed state. Instead, it is an infinite number of unique realities, depending on where you are and how fast you are moving.
"If you were a passenger in the slow rocket ship that you used in your example, I would observe you pulling away from me at high speed. But from the perspective of the light beam, neither of us is moving at all. Both versions of reality are verifiably true, yet they are absurd when considered together."
"So what the heck is light?" I asked.
"Light is the outer limit of what is possible. It is not a physical thing; it is a boundary. Scientists agree that light has no mass. By analogy, think of earth's horizon. The horizon is not a physical thing. It is a concept. If you tried to put some horizon in a bucket, you couldn't do it.
"Yet the horizon is observable and understandable. It seems to be physical and it seems to have form and substance. But when you run toward the horizon, no matter how fast you go, it seems to stay ahead of you by the same distance. You can never reach the horizon, no matter how fast you move."
He continued. "Light is analogous to the horizon. It is a boundary that gives the illusion of being a physical thing. Like the horizon, it appears to move away from you at a constant speed no matter how fast you are moving. We observe things that we believe are light, like the searchlight in the night sky, the cloud-red sunset. But those things are not light; they are merely boundaries between different probabilities.
"Consider two plants. One is in direct light and the other is in perpetual shadow. The lighted plant experiences more possibilities because it lives longer and grows bigger and stronger. Eventually it will die, but not before it experiences many more possibilities than its shaded counterpart."
"Okay," I said, "I'm having trouble imagining light as not being a physical thing. How can it influence physical things if it isn't physical itself?"
"There are plenty of nonphysical things that affect the world," he said. "Gravity is not physical, and yet it seems to keep you from floating off the earth. Probability is not physical, but it influences a coin toss anywhere in the universe. An idea is not physical and it can change civilization."
"I don't think ideas are an example of something nonphysical changing civilization. The brains of the people involved are physical things, and they influence our bodies, which are physical. I don't see how ideas really enter into it, except in the way we label things. Ideas don't float around in space by themselves. They're always associated with something physical in our brains."
"Suppose I write a hurtful insult on a piece of paper and hand it to you," he replied. "The note is physical, but when you look at it, the information enters your mind over a pathway of light. Remember that light has no mass. Like magnetic fields, light exists in no physical form. When the insult on the note travels across the light path from the note to your eyes it is completely nonphysical for the duration of the trip. The insult encoded in the light is no more real than a horizon. It is a pure transfer of probability from me to you. When the insult registers in your mind, physical things start to happen. You may get angry and your neck and forehead might get hot. You might even punch me. Light is the messenger of probability, but neither the light nor the message has mass.
"When we feel the warmth of sunlight, we are feeling the effect of increased probabilities and, therefore, increased activity of our skin cells, not the effect of photons striking our skin. Photons have no mass, the scientists tell us. That is another way to say they do not exist except as a concept."
He continued. "You might have heard it said that light is both a particle and a wave, sometimes behaving like one, sometimes like the other, depending on the circumstance. That is like saying sometimes your shadow is long and sometimes it is short. Your shadow is not a physical thing; it is an impression, a perception, left by physical things. It is a boundary, not an object.
"Light can be thought of as zones of probability that surround all things. A star, by virtue of its density, has high probability that two of its God-dust particles will pop into existence in the same location, forcing one of them to adjust, creating a new and frantic probability. That activity, the constant adjusting of location and probability, is what we perceive as energy.
"The reason you cannot catch up to a light beam, no matter how fast you travel, is that the zone of probability moves with you like your shadow. Trying to race light is like trying to run away from your own thoughts.
"The so-called speed of light is simply the limit to how far a particle can pop into existence from its original location. If a particle pops into existence a short distance from its original position, the perceived speed of that particle will be slow. If each new appearance is a great distance from the starting point, the perceived speed will be much faster. There is a practical limit to how far from its original distance a particle is likely to appear. That limit is what gives light an apparent top speed."
"My brain hurts," I said.
