Comet Sonnet

I am writing this quite pointless sonnet
about a big lump of ice in the sky.
That big lump of ice is called a comet,
“How on Earth,” you may ask, “does that thing fly?”
The answer, my friend, may seem rather strange,
but hang on a moment, and I'll explain.
The reason is gravity, “You're deranged!
That makes things fall!” you interject again.
It is all about its orbit, you see.
“Like how the Earth orbits the Sun?” you ask.
Yes, of course, that is quite correct, says me.
I'd explain but I must now end this task,
     because, as you can see, I'm out of time;
     this is, I regret, my very last line.