Center of the Universe 7/9/21

Science with Richard Bleil

Well, look at that, the Scotty character said (no quotation marks as I’m paraphrasing). It never occurred to me to think of space as the thing that’s moving.

Is it possible to move all of space? Actually, yes, I did it just today as I went to fill my water bottle. See, motion is always relative to something. Are you two cars traveling to a fixed point in the road at 70 miles per hour, or are they traveling towards you at 140 miles per hour as you sit in your car? It’s all a matter of perspective.

Early astronomers assumed that the earth is the center of the universe since, after all, if they were moving, they would surely feel it, right? Then the sun, the moon, the stars, the planets all evolve around the earth. Today we think of the sun as the center of the solar system, but certainly not the center of the universe. That’s a different center. So why would you want to choose one center of motion over another?

Frankly, it’s ease of the mathematics involved. By assuming that the earth is the center, the orbit of the moon is trivial to calculate as just a simple ellipse (not quite a circle). But if we count the earth as the center of the solar system, then we have to account for some odd behaviors as some planetary orbits include loops that cause them to move backwards. This used to be called “retrograde motion” and I believe that astrologists still use this phrase. These loops, mathematically, are nightmarish in their equations, but by simply shifting our thinking so the sun is the center of our solar system, then the mathematics of all of the planets are simply elliptical.

Einstein called this relativity. The concept of relativity is actually a simple thing. Basically, he was talking about what I just suggested, the relative motion of two objects that are subject to the choice of the fixed center, be it a point in space, or the Enterprise fixed in its location as space moved around it. And yet, in this relativistic construct, there are some strange things that happen.

For example, the speed of light is always fixed, namely (in a vacuum although it does change in other media slowing down in more dense materials) six hundred seventy million miles per hour. But this velocity is the same if the Enterprise is at a full stop as light passes it, or if it is moving towards the light or away from the light. The speed is always the same, six hundred and seventy million miles per hour. The color of the light changes depending on if the Enterprise if flying towards it, away from it or standing still, but the speed is nonetheless the same. This is very odd.

Einstein also came to realize that the dimensions are not rigid, and they are not straight. We think of motion in one direction, say along the x axis or east and west as always the same, and always straight, but as it turns out, there is a curvature to space. This gives space a limited volume, and oddly flexible. The flexibility comes into play around massive objects or, if you prefer, enormous gravitational pull. The illustrations I’ve seen are usually akin to a bowling ball on a mattress, where the mattress bends towards the ball. This is perhaps not a great analogy, since the dimensions are not made of matter, and all axes bend near those massive objects. But it can be seen as a large planet passes near the line of sight between the earth and a distant star. The position of the star seems to shift, as the path of the light is affected by the gravitational pull of the object. Honestly, this shouldn’t happen based on the nature of light alone, but it does suggesting a distortion of the dimensions around the planet.

Another odd thing is that there is, indeed, a fourth dimension. Einstein suggested that, like direction, time is also a dimension in space. If it’s a dimension, and if the dimensions are not fixed, then that implies that time is not fixed either. There’s a kind of flexibility in it, and like direction, is affected by heavy gravitational objects. This often shows up in science fiction as time dilution. You’ve probably heard that time slows down near large objects like black holes, and at velocities that approach the speed of light. I have to admit, my mind of late has been awhirl with the thought that time is just a dimension, that dimensions are flexible around gravitational centers and that gravity is a wave. Somehow, these seem to point towards a time machine. No, I don’t think we’ll ever actually make one (especially since time seems limited to a single direction as opposed to the other dimension), but it’s fun to consider the possibilities.

The funny thing is that I really didn’t intend to make this a blog about the theory of relativity, but, apparently, that’s what it has become. I hope you enjoyed it!