Every day, about a billion rice-size meteors fall on earth. Twice a week, the earth has an encounter with a space rock the size of a football. Once a year, a car-size rock comes hurtling towards our planet from space. And once in 250 years, a celestial rock the size of a house gives us a scare on earth. So, what's the chance of a human being getting hit by a meteor? "One in 20 billion," says Dan Riskin, the co-host of science show Daily Planet, reassuringly.
What has Riskin and his co-host, Ziya Tong, looking skywards is the recent encounter Chelyabinsk in Russia had with a 10-tonne meteor which created a sonic boom that left buildings damaged, glass windows shattered and about a thousand people injured, mostly by flying glass. Riskin and Tong, in the show
Fire in the Sky that airs tonight, take cue from this event that occurred early Friday morning on February 15 and step into the past to recount a similar incident that took place 104 years ago. That was on the morning of June 30, 1908 near the Podkamennaya Tunguska river in remote Siberia. Called the Tunguska event, that is the largest ever recorded explosion of a space object hurtling to earth. This February's blast, which took place roughly 3,000 miles west of Tunguska, is the biggest since.
The show brings some old footage of an expedition to Siberia undertaken in 1938 - 30 years after the Tunguska explosion - which shows the magnitude of destruction it had caused. The Tunguska explosion had flatted 80 million trees over 2,150 square km and created a shock wave that would have measured about 5.0 on the Richter scale.
Ever since, Russia has reported several meteor hits, leading many to wonder whether this part of the globe is prone to such strikes because of its geographical location or because of some cosmic factor. It emerges that given its sheer size, Russia is only getting its rightful share of meteor hits. Russia does, after all, form more than one-eighth of the earth's inhabited land area.
The reason both the Tunguska and the Chelyabinsk episodes escaped warning was because the meteors came screaming to the earth from the day sky and thus, could not be detected even by the most powerful telescopes.
Fire in the Sky, which offers some rare and exclusive footage of both these incidents, also draws attention to another visitor from space that came within kissing distance of the earth the same day a meteor hit Chelyabinsk. This was the asteroid called 2012 DA14. This giant rock, with an estimated diameter of 30 metres, was much closer to earth than our weather satellites are. Had it hit us, coming at a speed eight times that of a rifle bullet, the impact would have been akin to that of a 2.5 million ton TNT blast.
The two episodes - the meteor hit and the asteroid visit - were, however, not related. It emerges that the two were a "freaky cosmic coincidence," says Tong. While the meteor's path was east to west, that of the asteroid was south to north. And 16 hours elapsed between the two passages.
Through interviews with and experiments by scientists, physicists, astronomers and experts from around the globe, the show tells us about the possibility of future such encounters. And how we can, perhaps, protect our earth against them. The nearest such encounter, it seems, could be in 2029, with the asteroid called Apophis.
Fascinating details emerge of what scientists are trying to do to nudge it slightly off course so that it steers clear of the earth. Humongous effort is going into planning this "slight nudge". Should it be through laser beams? Or would energy reflected from giant and multiple mirrors fixed on some 20 spacecraft do the trick? At the Georgia Institute of Technology, students of Team Blast are sending "eyes to the skies" to learn more. It's critical to learn the composition of the asteroid, they tell us. Is it made of carbon or is it heavy metal which can do far greater damage in case of a strike?
The scientists say after all these efforts what "we've come to know is that we just don't know". NASA, for example, tracks about 10,000 asteroids. Yet, the show tells us, we know only about one-tenth of the asteroids in our space.
The February episodes, says Tong, only come as "a reminder that space is a violent place and we live in it".
Fire in the Sky, a Daily Planet special, airs on Discovery Science, tonight at 9 pm
