Expert: Tom Whiting - 5/22/2009

Question
Hi Mr. Whiting! If you would be so kind as to give a little definition of comets for me i would greatly appreciate it. I need a quote from an expert for my science paper so anything you know would help. thank you for your time

Answer
Hi Karson,
Be glad to, although I can't take credit for it, the best definition
I ever heard for a comet is, at least mass wise:
"A comet is something that is the closest to nothing that anything can be, and still be something".    (that's basically saying that comets are extremely low mass objects).

And the other definition....turns out astronomer Fred Whipple of the 1950's was right with his guess back then...Comets are nothing more than low density large 'dirty snowballs'.

And that agrees with the current research that comets are nothing
more than frozen water and frozen lightweight gases like methane,
ammonia, carbon monoxide, carbon dioxide, etc. with some solid
dusty contaminants mixed in like silicon (basically sand), iron
oxide (rust), and a few other solid elements.
And of course, comets sublimate as they approach the sun
(solid ices go right to the vapor state, bypassing the liquid
state- because liquids cannot exist in a vacuum)...and the tail
is the result of the solar wind 'blowing' the tail downstream from
the comet in a direction opposite the sun. Thus the tail is NOT
an indicator of the direction of flight.  In fact, it's a non-
indicator, unless the comet is plunging right into the sun. But
if it's orbiting the sun, then the tail, by definition, is a
non-indicator of the direction of travel.
Most comets have 2 tails, the heavier dust tail which lags the comet,
and the ion (gas) tail, which maintains a direction directly opposite
the sun.
And remember that comets orbit the sun, not the Earth...in fact,
they don't even know that the Earth exists.
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA