Hawking is right.

[Termite]

Sooner or later, a fair sized one is going to hit us.

[mekender]

Of course he is right, sheer probability says that they have to hit every once in a while. Thankfully we have had a good 65+ million years since a major hit.

The trick is, it takes a pretty good sized one to actually do any real damage. The one that hit AZ leaving the famous crater there was about 50m across. If that hit a city, it would be absolutely devastating, but the likelihood is that it would hit ocean or unpopulated areas.

Of course, once they get past a certain size, it would not matter where they hit, but the likelihood of such an event is so low and the ability to stop such an event is so small that it is probably not even worth worrying about.

[PawPaw]

Well, sure he's right. It's easy to be right when you don't have to predict the time frame. And, Hawking is a bright lad. He's pretty good at what he does.

[MarkD]

Who was it that said that asteroids are the universe's way of saying "How's that space program going?"

[Weetabix]

The trick is, it takes a pretty good sized one to actually do any real damage. The one that hit AZ leaving the famous crater there was about 50m across. If that hit a city, it would be absolutely devastating, but the likelihood is that it would hit ocean or unpopulated areas.

The hard science end of the world books seem to say that an ocean strike is worse than a ground strike for climatic effects.

Of course, once they get past a certain size, it would not matter where they hit, but the likelihood of such an event is so low and the ability to stop such an event is so small that it is probably not even worth worrying about.

Plus, we already used up Bruce Willis in Armageddon.

[308Mike]

Nothing new here. It's been going on for millions of years, but we've only recently been able to track and watch them go by.

"This is not an unusual event," Paul Chodas, a senior scientist in the Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. "Objects of this size pass this close to the Earth several times every year."

Chances are, something that size (25 feet) would likely break up in the atmosphere, creating multiple small impacts (if it's an iron object), if it's a consolidated snow/ice ball, it would probably make a nice sonic boom, but that would probably be it.

2014 EC was just discovered on Tuesday night. It's about half as wide as the space rock that exploded without warning over the Russian city of Chelyabinsk in February 2013.

[Darrell]

This video shows all known asteroids and new discoveries from 1980 to 2010:

http://www.youtube.com/watch?v=S_d-gs0WoUw

Fascinating, and sobering, to watch--Earth is the third blue dot out, of course. New discoveries are white. Earth crossers are red. Note that the rate of discovery went way up after Comet Shoemaker-Levy 9 hit Jupiter in the mid '90s; this is when it really hit home with people that strikes can and do happen; it's not a coincidence that this is when really serious searches began. Note too that new discoveries tend to follow Earth as it orbits the Sun, on the side of the sky opposite the Sun, well, because that's where it's night on Earth.

There's a newer version at the link, runs to 2011, IIRC. I like the music better on this one.