Louisville Process Theology Network

What is Time ?

May 10, 2010

Space and time are modes by which we think, not conditions under which we live. Time ?– the time that we know through clocks and calendars ?– was invented.?”

Albert Einstein, 1951



Einstein on Time ----

To begin with, Einstein reasoned that observers separated by the vast distances of our Universe cannot possibly see what is happening to each other. An event that occurred light-years ago can appear to be happening now by the time the sight of that event reaches us. Events that appear simultaneous to one observer or another may not actually be simultaneous.

We assume everything we see is happening now. Not so. The sight of events happening way across the Universe reaches us light-years after their occurrences.

This realization led Einstein to reason that space and time between locations vastly distant from each other differ by the speed of light.

Hold on to that thought for a few moments.



Our Perception of Space and Time in our Daily Lives ----

Locally, we know that time passes the same for everyone. This is common sense.

It also appears to us that our place in the Universe is standing still. Objects move when they are pushed and stop when the forces applied to them are removed, or when they meet significant resistance. But, scientific observations have long told a different story.

Even before 1600, Copernicus recognized in his observations of planetary movements that Earth revolves around the Sun; instead of the other way around. So apparently, we live in perpetual motion in sync with the movement of our planet.

Kepler did the math (trigonometry) on these observations several years later and produced ellipse shaped revolution cycles; not symmetrical circles. So, it would appear that the planets move at varying speeds in response to the gravitational forces they encounter along the way.

Taking Copernicus, Kepler, and the discoveries of others into account, Galileo reasoned around 1630 that every object moves in uniform motion until force is applied to change it.

This insight led him to formulate and test one of the earliest principles of Relativity. In Galileo?’s words, according to the introductory textbooks on Physics, ?“Any two observers moving at a constant speed and direction with respect to each other will obtain the same results for all mechanical experiments.?”

More broadly, Galileo reasoned that motion, gravity, and the other laws of Physics are the same for all objects in uniform motion with respect to each other.

Thus, space are time are both the same for everyone locally. This is also common sense.



How to Reconcile Invariant Equations ----

But, research into electromagnetic phenomena by Michael Faraday, James Clerk Maxwell, and others from approximately 1750 to 1900 demonstrated that mathematical equations (trigonometry and calculus) which describe the movement of electromagnetic waves differ from one point of observation to another.

Maxwell?’s equations are ?“not invariant?” according to the introductory textbooks. In other words, he needed to use different equations in different frames of reference.

That led some physicists to theorize on the existence of an absolute frame of reference somewhere. From such a place, the equations would be invariant after all.

Does this mean Earth is the absolute frame of reference for observing electromagnetic waves? If so, our planet would be the center of the Universe. That idea had been ruled out by Copernicus long ago.

Albert Einstein?’s insight was to recognize that the various equations for describing the movement of electromagnetic waves were not the problem. The problem was the variables for space and time. It appeared that a mathematical transformation was needed.

To correct that problem, Einstein added a step to Galileo?’s principle of Relativity. ?“The velocity of light is the same for all observers, in all directions, regardless of the motion of either the observer or the light source.?”

Doing the math, he demonstrated that space and time between locations vastly different from each other differ by the speed of light. The numbers worked even though the concept was, and still is, counter-intuitive.

Contemporary physicists reason that time and motion are essentially the same phenomenon in a Universe where everything is constantly moving. It?’s thought that we can only perceive motion in the Universe; not time.

Our human sense of past, present, and future appears to come from the neuronal dynamics of our brains. Through ?“psychological time?” we experience the motion of the Universe.