Expert: Tom Whiting - 6/19/2010

Question
Hello, I have a few questions to ask about a doomsday prediction by Nostradamus for a story I'm writing and I'm actually interested in the answer as I'm into space and sciency stuff. If a comet planet *like the one Nostradamus said would come to Earth* were large enough and passed close enough to the planet. could it pull on the Earth's crust as the moon does with tides seeing as it is basically lying on top of liquid? If it could would that result in massive earth quakes, volcanic eruptions, massive tsunamis, and radical tides? If it has the gravitational pull to make the crust act like an ocean, could it also pull the moon into a more radical elliptical pattern? Almost done, if a comet planet were to pass close enough, could it pull atmosphere from the planet as it passes? And last but not least, would a scenario like that threaten the human species as a whole?

Answer
Hi Chris,
We really don't worry about comets unless they impact the Earth. The reason being, they are all
very low density "dirty snowballs" in the words of Fred Whipple...
Mass-wise,... "A comet is the closet thing to nothing that something can be, and still be something."
 In fact, anytime a comet comes close to a body, it's the comet's orbit that is altered, not the planet. (Check out the 1994 impact into Jupiter by Comet Shumaker-Levy 9).  Even the moon is very massive compared to even the largest comet nucleus, so even it, the moon, would be unaffected. Actually we did take a hit back on June 30, 1908... the Tunguska event, either a small comet or asteroid.  All it did was destroy several thousand sq. miles of Tundra in Siberia.
There was no change in the crust, the orbit, the rotation, the atmosphere, or anything else.
And you can't get any closer than that explosion at altitude.

Even a rather large asteroid, say 20 miles in diameter, if it's just a close approach, the same would happen... it is the asteroid's orbit that is modified, not the Earth's. Those bodies only hurt the Earth if they impact us, and only if they are big enough to do harm.
Most astronomers do not buy into the various doomsday scenerios... we've had 4 or 5 the past
50 years... there was the planetary alignment scare in the 1960's, the Jupiter effect, the Halley Comet Effect in 1986, the Hale-Bopp effect, the Y2K effect, the galaxy alignment effect
(as if anyone knows when we line up with 'the galaxy')... and now the stupid Mayan Calendar effect coming up.  How many times can one be wrong?  Actually, the Mayans couldn't even accurately predict their OWN demise... how would one expect that they could predict ours?  Besides, we're not on the Mayan Calendar, they are... we're on the Gregorian Calendar, and it continues.  People write doomsday books just to make money, and that's it, taking advantage of
the ignorant and gullible people.
Actually there is an important event on December 21, but it's this year, not 2012. We (USA) get
a total lunar eclipse on 12/21/2010.
So the answer your question is, no, no, no, and no.
The only BIG event of 2012 is our last transit of Venus across the disk of the sun on D-Day
(June 6) of 2012. Miss that one and you're waiting until December 2117 until the next one, 105.5 years later.
The biggest "Doomsday" real story is the Gulf of Mexico seafloor oil GUSHER... in a few more years, at a million gallons a day, can you say  "Holocene sealife extinction?"
Clear Skies,
Tom Whiting
Erie, PA USA