An astronomer on an extended lecture tour became weary of delivering the
same lecture night after night. He confided this state of mind to his
chauffeur as they were driving to their next destination. The chauffeur
expressed a similar boredom in his line of work.

Ive got it! said the astronomer. You are bored with driving and I am
weary of lecturing. Lets exchange places for one night. It will be a
refreshing change for both of us. My lecture is all written out word for word
and nobody in the next town knows me by sight anyway. The driver agreed and
the exchange of roles and dress was made. That night the lecture hall filled
to capacity. At the appointed time those in attendance heard a flawlessly
delivered lecture. At its conclusion the lecturer basked in the euphoric
applause. Then came the question and answer period.

Who discovered Uranus? came from a boy in the front.

Uh…William Herschel. He remembered that from somewhere.

And who discovered Pluto? continued the boy.

Aaaa…that would be Clyde Tombaugh. He had read a little.

Then from the back: Would you please comment on the relative merits
of the pulsation instability model and the accretion disk instability model for
the explanation of outbursts of cataclysmic variable stars?

The speaker paused for a moment, then said, I am surprised that you
would bother to ask me such a simple question. To show you how really simple
it is I shall have my chauffeur answer it for you.