It's a beautiful universe, an indifferent universe, why it's sometimes even a Bad Universe. And who better to explain why it can be bad than my friend Dr. Phil Plait, the popular Discover Magazine blogger and author of Death from the Skies!, also known as the Bad Astronomer. Tonight on the Discovery Channel at 10 PM EDT Phil will boldly go on a grand special effects journey where many cosmic disasters have gone before. Watching it just might save your life!
Steven "DS" Andrew: So, it's a bad universe?
Dr. Phil Plait: "Yes, it's trying to kill us! We live in an environment that's tailor made for us and think that's normal. When in fact the vast, vast majority of the universe is either so inhospitable or so violent it would put the hurt on us. Most of that stuff we can't do anything about. But tonight's program is about one of the most plausible ways the universe can kill us, impacts, and that we can do something about."
DS: Let's say I happened to be near enough a medium sized impact to see it streak across the sky and hit on or near the horizon, what would I witness?
Phil: "It would vary greatly depending on how large the object is, what it's made of, what it hits, and even then there's some things we can be more sure of than others. Just generically, we're talking a rock in the 50 meter range seen from two dozen or so km away ... it would probably be incredibly bright, enough to dazzle you, make you wince. The irradiance, the part of the heat pulse that travels at the speed of light, might feel similar to the summer sun on bare skin. At least I don't think you'd burst into flame on the spot.
"But the blazing-hot shock wave that would quickly follow an airburst or a ground strike from an object that large would damage or flatten houses for miles. A direct hit on a major city would destroy the urban center, similar or worse than a Hiroshima-type atomic bomb, and probably set fire to the suburbs and whole counties around it. Over a rural area with lots of stuff on the ground to burn, say Kansas or Missouri, half the state might end up catching fire either from the ejecta thrown out from the crater or the burning fragments and heat wave raining down from a high altitude airburst. If it hit the ocean, it would cause tsunamis all over the world. It would be bad."
DS: That sounds bad, but how often do significant impacts happen and what can we do about it?
Phil: "We have to detect, intervene, and monitor. Just like a car speeding at you is easier to avoid when it's 200 hundred feet away as opposed to 10 feet away, our options are much better when an object is far away. We're doing better on detection lately, but we could do more with more telescopes especially in the southern hemisphere. After detecting a threat years before impact and tens of millions of miles away, the next thing we'd have to know is how it's put together.
"These things range from a loose collection of dust and snowflakes to hunks of solid rock and metal. If it's a solid object it might be possible to simply ram it with a spacecraft or a series of spacecraft, we might get enough momentum transfer from that to do the job. But a better idea is the gravity tractor, because that method works on all sorts of compositions: park an unmanned spacecraft something like the mass of Hubble nearby. One able to maintain station precisely, say with ion thrusters like Deep Space 1 had, and just the gravitational field of that small spacecraft will, ever so slowly, pull the object safely away over time. Then we'd have to monitor it, make sure it doesn't loop around and hit us on a later orbit.
"All kidding aside, what's starting to be a little scary, if we extrapolate the impacts we've been seeing on Jupiter lately and the ones we know about on earth, an object as big or bigger than the Tunguska event might happen every few hundred years. That's an impact big enough to injure or kill millions of people in a populated area. One big enough to throw a medium-sized nation into chaos might happen every few thousand years.
"That's exactly what we talk about and illustrate on the show tonight -- oh and I got to set off 3000 lbs of high explosives as part of the program! But scaling small explosions and other models like that up to big impacts is tricky science. 100 times more massive doesn't just mean 100 times the same kind of damage, it means whole new physics kick in, whole new phenomena amplify each other. Bad, violent things happen that don't happen at all at lower magnitudes."
Bad Astronomy employs a delightful mix of colorful science and a comedy channel approach to the mysteries of the universe. That same format and special effects wizardry are sure to entertain and inform science-aficionados age nine through ninety. Tune in tonight, and learn why good science is our best defense against a Bad Universe.