“What are you learning about now in science class?” I asked some students.

 

“I do not know,” replied a student.

 

“The minimum you must know about each class is what they are talking about. You must know the subject. Can you try to think what you were learning?”

 

“We were talking about the universe.”

 

“Good. How BIG is the universe?” I asked, gesturing with my hands to show large size.

 

“Infinite,” the student replied.

 

“No, it is not infinite.”

 

Here is how we understand it. First, we know that it takes light a little more than 8 minutes to go from the sun to the earth. When we look at the sun, we see what was there 8 minutes ago. According to 20th century physics, the speed of light is the speed of information. The only reality is the position of the sun 8 minutes ago. Indeed, the gravitational force of attraction of the sun on the earth is directed to where the sun was 8 minutes ago, not where it is now. This is called the retarded force.

 

SEE THE BOOK FOR MORE DETAILS.