The speed of light and reality



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THE SPEED OF LIGHT AND REALITY



The finite velocity of light has an interesting implication for us concerning the question of reality. While this essay was being written, the Apollo 15 astronauts were on the moon, and I was listening to them. When a question was asked from the Houston Space Center, it took about 2-1/2 seconds before we received an answer. This of course was due to the time it took for the radio waves traveling at the speed of light to go from the earth to the moon and back again with the answer. Thus when a question was asked, "How are you?" the answer came back, "Alright." It wasn't how the astronaut was then, it was how he was 2-1/2 seconds ago, the amount of time it took to make that round trip from earth to the moon and back again. Obviously, then, it would never really be possible to know how the astronaut was right now. In fact, if anything were to befall the astronaut, we would not know about it for the amount of time it took to go from the moon to the earth.
Of course, the moon is a relatively close object. If the astronauts had been on Jupiter instead of the moon then it would have taken 35 minutes for a round trip, and if we asked the question, "How are you," and we received the answer, "Alright," 35 minutes would have elapsed. By that time, perhaps the answer would no longer apply. And although Jupiter is farther from us than the moon, Jupiter is still a relatively nearby object. Suppose these astronauts had been on Pluto; the round trip might have taken almost a half-day. And some day in the future, if the astronauts are ever able to go to a planet going around another star, say, the nearest star, it would take about 8 years before the question, "How are you?" and the answer, "Alright," was received.
And so it is that when we look at the sun, we are not looking at the sun as it is now! we are looking at the sun where it was 8-1/3 minutes ago, the time it took light to travel from the sun to the earth, a distance of 93 million miles at 186,000 miles/second. If the sun should go out right now, then we wouldn't know about it until 8-1/3 minutes afterwards. We would have sort of a grace period to get our affairs in order, of 8-1/3 minutes. When we look out at the stars at night, we don't see them as they are now, but we see them as they were some time ago, less time for the nearer stars, more time for the more distant ones. The nearest star to the earth is 4-1/3 light years away, this means that it takes 4-1/3 years for light to travel from the nearest star to the earth. And that is the nearest star; all other stars of course, are even more distant than that, and therefore, as we look at them, we are seeing them as they were even further back in time. Indeed, when we look out into the starry sky we are in reality looking back in time, and we can see some galaxies in telescopes that are so far away that the light which is just now reaching us started out on its journey over 5 billion years ago. The further out in space we look the further back in time we look. This of course, is something most familiar to astronomers. They have given up every hope of finding the universe as it is now. How could we ever see the universe as it is now? We can't even see the universe the way it is all at one time because the nearer objects are not as far back then as the more distant ones, and so when we look at the universe at night, what we are seeing is a journey back in time, and the amount of time we are going back is different for each object we look at.
Now if the speed of light were not so rapid, we would be much more aware of this. For example, when you look at someone across the room, you are seeing him as he is now, at least that's the way we think of it. But obviously, since it took a certain amount of time for the speed of light to cross the room, and then reach your eye, you are seeing him not as he is right now, but as he was a very brief, a very, VERY brief moment ago. Since the speed of light is so rapid, we aren't even bothered by it for this short amount of time which has elapsed from when the light was reflected off his body and entered our eye. We define when we see that person as now, even though it isn't now. If the speed of light were 1 inch/second, instead of 186,000 miles/second, then obviously it would make a great deal of difference between what we call now and what really is now. And it doesn't stop by simply viewing other people across the room. Put your hand out in front of you. Look at your fingers. Do you see them as they are now? Well, your fingers are much closer than the person across the room, but it still takes a certain amount of time for the light to be reflected off your fingers and into your eyes; and if you say, "I can feel my fingers; I can fell my fingers as they are NOW." The answer is, no, because you feel your fingers only through electrical nerve impulses that go from your fingers to your brain when you become aware of them. And these nerve impulses don't travel any faster than the velocity of light; they may even travel slower. Therefore, as you feel your fingers, as you look at your fingers, as you sense your whole body, you are not sensing your body the way it is NOW, you are sensing your body the way it was then, and the more distant the parts of your body that you are thinking about and looking at, the further back in time is the perception which you get.
All this leads us to conclude that it is essentially impossible to ever see anything and ever sense reality the way it is now. There is no now in reality.


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