A Physics Question For Dr. Rice

Hi Dien,

The other day my 18 year old son came to me with a physics problem which I could not logically answer…..

Now I’m no physics expert, but when I was at school, I was always taught that you cannot travel faster than the speed of light.

My son posed this question to me…..

He said, “Dad, if two cars pass each other from opposite directions, and both are travelling at 100 mph…. What speed do they pass each other at?”

I answered, “Son, I believe that they pass each other at 200 mph”.

He replied, “Dad, that’s what I thought… Now let me put a hypothetical to you…. Suppose we have two space ships, and each was capable of travelling at more than half the speed of light…. And these two ships passed each other as in the car example…. Would it not be fair to say that for a brief moment in time…. Both space ships pass each other at a speed greater than the finite speed of light?
Thus for a very very brief moment in time…. The crew on board looking out the porthole would witness an object passing them at a speed greater than light itself, even though they would not physically notice it?

Dien…. How do I answer my Son?

Warmest Regards

Ricky Higgs




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