NDT: Using a Gravitational Tractor to Prevent a Meteor Strike

"You know the solar system's a shooting gallery. And Earth, many people don't know, plows through several hundred tons of meteors a day. So, the range of these that could hit us is huge.

Apophis – that was discovered in December 2004. It's an asteroid about the size of the Rose Bowl. If the Rose Bowl – imagine that as kind of like an eggcup, and you place something in it to hold it, that's about how big that asteroid is. That's not too shabby – that one, if it hits, it'll do some serious damage.

The first calculation showed that there was a real chance it could hit Earth in the year 2029 on April 13th. Which, by the way, happens to be a Friday.

As the months went by we had better orbital data and we determined that no, it will not hit us April 13th 2029, but it will come very close. It will come closer than Earth's orbiting communication satellites. It'll be the biggest, closest thing we've ever seen in the history of history. It'd be visible from northern Europe and it's basically – think of it as a shot across our bow. The universe saying, "I'll miss you this time, but I'll give you another chance to try to deflect me."

What many people, we have top sort of engineers and dynamicists working on – one problem, which is – involves what we call a gravitational tractor. A kind of a tractor beam where you send up a spaceship, bring it close to the asteroid, but not touch it, and you sort of park it there. And what I mean by – both of these are moving through space so when I say park, I mean you match velocities with the asteroid. And their mutual gravity will want to attract them to each other. And as they drift, you say, no, I'm not going to let that happen. So, you put on the little retro rockets on the rocket to prevent them from colliding. The act of doing that effectively tugs the asteroid out of harm's way. Because all you really want to do is move it so that it will not hit Earth in its trajectory. It'll still be out there, its orbit will still cross the orbit of the Earth, but you've lived to enjoy another day."

Neill DeGrasse Tyson on the radio show, Living on Earth. Listen to the show or read the full transcript here.

Sunset on Mars

Sunset on Mars casts bluish light over the distant horizon.

from the Nat Geo photo series, Visions of Mars.

Images from the Hubble Telescope

Check out Harvard Magazine's "Eye on the Universe," an interesting article accompanied by amazing photographs taken from the Hubble Space Telescope.

Best Astronomy Photos of 2007

APOD (Astronomy Pic of the Day) has posted its favorite astronomy pics of 2007. The one below is my favorite -- be sure to click inside the pic to view a larger image of it.

Manhattanhenge

Manhattanites take it for granted that their avenues run north-south and their streets run east-west. But truly observant inhabitants know that Manhattan's street grid is rotated 29 degrees away from the north-south axis.

Why should you care? Well, as Geoff Manaugh writes in his delectable BLDGBLOG, this angle carries "interesting astronomical side effects" -- namely, "Manhattanhedge," as coined by Neil deGrasse Tyson. For two days every year (May 28 and July 12/13), the setting sun lines up perfectly with the east-west streets of Manhattan's main street grid. The result, needless to say, is spectacular:




Unfortunately, I'll be out of town next week. Otherwise, I'd be simultaneously watching the sunset and sweeping a lady off her feet in Union Square Park like the couple above :)