Usually I really like the History channel. Along with the Discovery channel and Court TV, it's one of the few channels that I watch frequently. However, I caught most of a show tonight that was just awful.
The show was called "Last Days on Earth" and had a countdown of the "Seven deadliest threats to humanity. I first caught it as I was flipping through channels and the host said something about the Sun having 10 billion years left on its life. Nope. Solar mass stars have about 10 billion years in their main sequence lifetime (when fusion first begin until hydrogen is exhausted in the core).
Their #7 threat was a Gamma Ray Burst within our own galaxy hitting us. This is certainly a possibility. In fact, the professor I'm doing research with this semester is part of a team looking at just that possibility and has found evidence that a GRB may have been the trigger for the Ordovician extinction.
If a GRB nailed Earth, it would cause the ozone and diatomic nitrogen in our atmosphere to disassociate , reforming into nitrogen dioxide. This blocks out visible light, but lets through deadly UV light, and leads to acid rain as well. Not exactly fun. But nor is it exactly something to worry about.
Even if a GRB did happen in our galaxy (pretty likely), it would also have to be aimed right at us (not too likely). Additionally, our galaxy is pretty dusty and the amount of junk lying around would block anything but the closest ones. Overall, a GRB hitting us isn't something that we need to worry about. Not a chance that this should be on any serious list.
#6 was even dumber. This one was a rogue black hole passing by and sucking the Earth in. But the really big black holes are the ones that lurk in the centers of galaxies and we're plenty far away. No need for concern there. It's just the smaller ones we'd need to be concerned about. Such ones can exist out here in the disk of the galaxy, but since they'd some from disk stars, they'd be traveling pretty much the same direction, greatly reducing the risk of a collision. Sure, some would drift, but no need to panic here.
But black holes aren't even the only objects that would drift as they orbit the galaxy. Stars, which can be just as massive, but are millions of times as common are the ones we should really worry about. And that's what really matters; Mass. Contrary to science fiction, black holes don't "suck". They have a gravitational attraction just like anything else. So something with similar mass would be just as dangerous. So if this show were really being serious about things, wandering stars are the real threat! Of course, black holes are much sexier than stars, so it's no wonder they're getting the spotlight. At the beginning of the intro astronomy classes, we conduct a survey to see what topics students are interested in and among the students that actually answer, black holes is by far the most frequent. Popular, but again, not a real threat.
Some of the others weren't too bad. Supervolcanos are definately much more dangerous and probably do pose a serious threat as well as a deadly new virus and climate change. Although I also agreed that near Earth asteroids are also a threat that should make the list, the presentation of that particular one was botched yet again.
One of the people they interviewed was an astronaut who claimed that the number of people looking for these objects was only "enough to staff one shift at McDonalds." While it may be true that there's not many people that are undertaking a dedicated search, sky surveys and amateurs are constantly turning up these things. That's not to say that some will inevitably be missed, but to pretend that no one's looking for them is a huge distortion.
They also brought up asteroid 2004 MN (Apophis) which will make a close pass to Earth in 2029. In fact, it's so close, it will actually be passing closer to Earth than some of our satellites. We've known for quite awhile that it wouldn't hit in 2029, but there was a possibility that Earth's gravitational pull could perturb it to cause a collision in 2036. However, that was ruled out in 2006 and I've commented on it before. This MN 2006 is almost as bad as the Mars approach.
They also discussed a possible solution to divert a dangerous asteroid: Send up a massive craft which had enough gravitational pull to tug the asteroid onto a new course. Sure it'd work, but the more massive the craft, the harder it is to launch. No need to do that when smacking a less massive impactor in it would work just as well and be far cheaper. How about toting the practical solutions guys?
Typically the History channel's shows are pretty good, but even the preview for this week's episode of The Universe looked pretty bad. It's supposed to be about dark energy. At this point cosmologists aren't sure of the exact effect, but they do know that the "big rip" scenario that this coming episode looks to be pushing is less than likely.
Perhaps this is why I don't watch TV all that much.
There were some good bits though. One of the most frequent scientists interviewed was Neil deGrasse Tyson who's always a lot of fun to watch. Seeing him interviewed (both in this and Universe) always makes a show a lot better. But not enough to make up for all that nonsense.