Say Birkat HaChamah

From time immemorial, the sun has played a central role in the lives of humans. From the vast numbers of societies for whom the sun has a religious significance, to modern day scientists who investigate its chemical composition and effects on our communications systems, the sun has always held a great deal of interest for humanity.

For most of human history, the sun was assumed to move around the earth (a doctrine called "geocentrism" which means "earth at the center." Sometimes it is also called "Ptolemaic" after its founder Ptolemy). Although today, we all take the sun's immobility for granted (our system is called "heliocentric" which means "sun at the center." Sometimes it is also called "Copernican" after its founder Copernicus), it is not hard to see how on first examination, the movement of the sun around the earth would be a natural assumption. The main piece of evidence for this position is that when you go outside, the sun appears to move across the sky.

But let's imagine for a moment that we DID'NT know that the earth moved around the sun, or let's say your skeptical friend demanded proof. He or she might say, "The sun looks like it moves, who are you to say different?" Well, when astronomers look at the night sky, they can identify where the other planets are. From night to night, they see the planets move relative to the background of more distant stars. If the earth were stationary, the planets should move in a straight line. However, the planets actually appear to move back and forth at random. To picture this, you might imagine being in a car on a highway. If you assume that you are not moving, the cars in the lane over from you appear to pass you, then reverse direction and then pass you again. However, if you realize that both your car and the others are moving, your observations become easy to explain!

Simliarly, a video simulation of the solar system designed from the assumption that the earth does not move, would require the planets to follow strange paths. But as soon as you allow the earth to move as well, the paths look much more normal. The reason we believe that the earth goes around the sun, is that the paths of the planets make more sense that way. Watch the video below and notice how for the first 25 seconds the sun (the bright spot) moves. At around 0:25, the whole picture shifts and becomes far more simple.

Here's another cool simulation of a Ptolemaic solar system: