Pat's Strange Killer Asteroid.
According to Pat Robertson, the Earth is going to be destroyed by a large asteroid. Apparently this is in accordance with the word of Jesus and the book of Revelation. In addition, Pat says he has done the science.
I'll give Pat one thing - he considers that a previous asteroid wiped out the dinosaurs. He's an old earth creationist, not a young earth creationist. This is nothing new. He was attacked years ago by the band of willful ignoramuses at Answers in Genesis for his stand that the Genesis creation myth should not be considered literally.
But still, his talk of an asteroid a kilometer in diameter weighing six billion pounds struck me as unsound. I know six billion is a big number, but it just struck me as a low estimate for an asteroid of that size. So, while Pat says he has done the science, I don't think he did the math.
So - let's do the arithmetic.
We'll start by determining the approximate volume of the asteroid. We'll base it on the volume of a sphere.
This gives us a volume of 523,598,775 cubic meters. Now of course, the asteroid will not be a perfect sphere, so we'll round down to 500 million cubic meters.
Now, a cubic meter of liquid water weighs 1,000 kilograms or 2,200 pounds. So, if our asteroid was made of water, it would weigh 1.1 trillion pounds. That's a lot more than Robertson's 6 billion pounds. But of course asteroids are not made of liquid water. In general, they are made of iron and nickel ores or rock material, or a combination of ores and rocks. This takes us into a range of 3 trillion to about 6 trillion pounds. For a normal asteroid, Robertson is three orders of magnitude out.*
But perhaps Robertson was confusing asteroids with comets - generally considered to be dirty snowballs. This would drop the weight down to possibly 600 billion lbs (if the snowball is fairly loosely packed) - only two orders of magnitude out. And that's still one hell of a difference.
Assuming a composition that all televangelists are familiar with - well-aged horse manure - we end up with a 440 billion pound ball of crap - still way too much and still two orders of magnitude out.
So what could Pat Robertson's asteroid be made of? Consider polystyrene.** It comes in a variety of densities that would put the asteroid in the range of 1.5 billion lbs to 80 billion lbs. Finally an asteroid which meets the Robertson specifications.
Yes, Robertson's killer asteroid is a ginormous polystyrene packing peanut. I suggest that it would be so light relative to its size that it would just bounce away on hitting the upper atmosphere. It could not possibly destroy the world.
* A billion is commonly considered a thousand million, particularly in the US. Pat Robertson is an American and was addressing an American audience. In some non-English speaking countries, a billion is a million million. If Robertson was speaking in, say, French to a French audience, his numbers might be considered reasonable. But he was not. It is fair to claim he was intending the normal English and the normal scientific meaning of a billion, and thus quite wrong by a factor of a thousand (or three orders of magnitude.)
** Popularly AKA as Styrofoam - but that's a brand name.