120,000 km Is Still Too Close

texchanchan writes: "BBC report: '...on 14 June, an asteroid (maybe as big as 120 meters in diameter)... made one of the closest-ever recorded approaches to the Earth. ..' but was only discovered three days later. This is well within the moon's orbit. 'If 2002MN had hit the Earth, it would have caused local devastation similar to that which occurred in Tunguska, Siberia, in 1908...'"

Comments

Re:U.S. Govt

[BranMan]

In all fairness, the article states that the path of the asteroid was on a line with the sun. There is no way Earth based telescopes could have seen it, even had they known exactly where to look.

This will become more scary in the future, when there is some capability to deal with an asteroid on a collision course. When we get to that point, we'll be complacent and will eventually end up being sucker-punched by one of these asteroids coming "out of the sun".

Still relatively unlikely.

[recursiv]

120,000 km sounds close, but consider this:
The Earth is about 7,926 miles (12,756 km) in diameter. Roughly 12,000 km, or about a tenth of the flyby distance. The chance of any object that comes within 120,000km of actually hitting the earth is about (0.1)^2, or roughly 1%. This is still unsettlingly likely, but it's not exactly doomsday.

Re:But actually its still a small problem...

[bravehamster]

I'm going to be worrying a lot more about travelling on the highway than I am about asteroid collisions.

Yeah, but if you crash on the highway, you and your kids might die. If an asteroid hits the earth, millions or billions could die. So on a personal level, driving is more dangerous, but we're talking about the survival of the species here. It's not something to ignore.

Better math

[Shimmer]

Assume:

Incoming asteriod is a point particle.

Diameter of the Earth is 12,000km.

Asteroid will pass within 120,000km of Earth's center (possibly less).

The question then becomes:

Choose a random point within a circle of radius 120,000km.

What is the probability that this point lies within a circle of radius 6000km?

In other words, what are the relative sizes of the two circles?

(pi * 6000^2)/(pi * 120000^2) = 0.0025 = 0.25%

-- Brian

Re:U.S. Govt

[tgibbs]

Recall the pondering and headscratching that goes on whenever one of our larger satellites' orbit decays. The speculation on where it will come down would be downright amusing if it weren't so serious.

Actually, satellite decay is a much harder problem, because it depends upon the friction with the atmosphere, which is variable. An object coming in from outside is actually rather simpler. In the unlikely event that anybody happens to be watching.