Wednesday, April 11, 2007
The Space-Time Continuum
Isaac Newton was brilliant. His incredible works on the nature of motion of bodies has stood the test of time.
I learned physics, a little in high school, and a lot in college. A lot of the initial stuff you learn in a physics class is Newtonian physics. The man's formulas were so well done, that even in my life time, men have been sent to and landed on the moon; satellites put in orbit around the earth and most of the other planets in our solar system, all using Newton's formulas.
In one of the great coinkidinks of history that never fails to intrigue me, Newton invented calculus to have the math to back up what he was researching. The coinkidink? Newton's sometime rival in Germany, a man named Leibniz, separately invented calculus at the same time, hundreds of miles from Newton. It's like the story of Alexander Graham Bell inventing the telephone. We think of him as the telephone's inventor, although at the same time another man invented the telephone too. Alexander Graham Bell beat this man to the U.S. Patent Office by something like one hour and became world famous. How many of you have heard of the name Elisha Gray?
As time went on after Isaac Newton's lifetime, physicists began to try to unravel the little inconsistencies with Newton's work. Although his formulas for gravitational effects and Force is Equal To Mass times Accelleration are accurate enough to put men on the moon safely, there were known problems that needed working out.
The most famous one is that the orbit of the planet Mercury moves a tiny bit each time it circles the sun. When I was a kid, I LOVED my Spirograph, and the movement of Mercury around the sun is kind of like a Spirograph drawing in that the line it travels moves over a bit each time around the sun. Newton's gravitational laws, although way more accurate than anyone else's attempts at explaining mathematically the travel of planets, were shown to still be off a bit.
Now almost everyone is familiar with the name of Albert Einstein. What Einstein first achieved fame for was what happened after he decided to look at the nature of space itself.
Newton, in his famous work, Principia, basically passed over the notions of space and of time. Newton, by choice, said that everyone knows what space is, and space is absolute. Likewise Newton said the same about time, that everyone knew how time just kept on keeping on, and that time is absolute and unchangeable just like space is.
But by the time Einstein was doing his work in physics, during his spare time as a clerk in Austria's patent office, technology had advanced such that the speed of light was consistently being measured with great accuracy. One problem showed up though that mystified everyone involved, but it was to prove to be key to Einstein's big breakthrough.
If you and I were standing on the back of a flatbed truck travelling at a steady 90kph, and I, standing in the rearmost part threw a baseball to you in the front of the flatbed part, since we were travelling at a steady 90kph, it would seem to me and you that I just normally threw a baseball at say, 30kph toward you closer to the front of the truck.
But someone on the sidewalk watching us go past, would see a baseball move at 120kph when I threw it to you. The man on the sidewalk's perspective is different that your's or mine. Hence the term relativity.
Only problem was that the ever increasingly accurate measurements of the actions of the travel of light itself was not like this at all.
If instead of throwing a baseball, I turned on a flashlight and shined it at you in the same exact situation in the moving truck, NO MATTER WHO IS DOING THE MEASURING, ME, YOU, OR THE MAN ON THE SIDEWALK, WE WOULD EACH MEASURE THE SPEED OF LIGHT EXACTLY THE SAME, THREE HUNDRED MILLION METERS PER SECOND.
You say, huh? How can that be? That's what intrigued Einstein and what got him to thinking, and figuring. A lot.
What he came up with turned the physics world upside down and changed our lives whether you understand how much or not.
In short, Einstein revisited Newton's decision to blow off the nature of space and the nature of time, and eventually came up with the idea that, just as you cannot have an electric current without an associated magnetic field, space and time are not two distinct entities, but that they are just as intertwined as electricity and magnetism.
If I drive my car at 90kph on a road that is due north, all of my effort and energy and progress are in the north direction. But if the road curves a bit to the west and I end up still travelling at 90kph, I'm no longer travelling northward at 90kph, some of my effort and energy and progress is in the westerly direction.
Same thing applies to us in space-time. A car sitting in the parking lot is obviously not moving through space. It is moving however. 100percent of it's movement is through time.
All of us, all the planets and stars, are moving through space-time. A 60,000kph rocket on the way to Mars is moving less through time than I am on I-95 every morning; more of his movement is through space and less through time than mine. And instead of Newton's notions of an absolute space and an absolute time, they are in fact changeable.
That rocket moving at 60,000kph is experiencing time at a different rate than I am sitting here typing this into the computer. Time is slower for the rocket than it is for me because some of his movement through space-time is diverted into the space component of space-time, meaning time is slower for him than me.
That's why Einstein theorized that nothing can move through space at faster than the speed of light. Light is essentially massless and all of it's movement through space-time is in the space portion, time for a photon of light is at a standstill. That car in the parking lot is the flip-side of that coin, all of it's movement is through time. And that's why light is always moving at 300,000,000 meters/second, regardless of who measures it and in what situation it is measured in.
In the hundred years or so since Einstein started laying this stuff onto an astonished physics community, technology has advanced to the point that many esoteric little points that his mathematical foundations predicted have further proved the accuracy of his theories. Another example is that massive objects like our sun distort space-time so that light is bent around them from our viewing perspective. It's called a gravitational lens. We use this effect to see things that actually should be blocked from view by our sun, but aren't. And just like a camera lens, constructed in such a way as to appear to bring objects closer, astronomers can use gravitational lenses based on distant star clusters to see even more distant stars and galaxies.
Been reading again about this stuff lately. I read stuff like this often, because it intrigues me. And although Einstein's work in his early career tended to deal with massive objects like planets and stars, the math involved eventually helped to spark other physicists and has lead to today's ever increasingly astounding advances in sub-atomic theoretical physics.
But in the meantime, Einstein's additions to the understanding that Newton had laid down finally explained perfectly the eccentricities of the orbit of the planet Mercury. Cool.
Just thought I'd share.