The Sky is Falling
Thursday, June 21, 2012
On June 14th, our planet played host to an itinerant asteroid bearing the catchy name of 2012 LZ1, as it flew by at a distance of 3.35 million miles at its closest approach. Science-centred media outlets were quick to issue interviews with astronomers, cosmologists, and even astrologists, to soothe fears in the global community that the gigantic, 500 foot-wide mass posed no threat to earthly populations. The ellipse experts did point out, however, since the universally accepted “near miss” boundary is at 4.65 million miles, this chunk of instant climate change was easily within that perimeter.
A number of facts that emerged amongst the mountains of data available regarding the approach of 2012 LZ1 may be somewhat concerning to the public at large, as well as those in the asteroid-related sciences. Of paramount concern is that, despite the immense size of this spatial specimen, various reports put it between 500 feet and 2500 feet wide, it had not been spotted until the beginning of the month, providing just two weeks of reaction time. If it had possessed a slightly different trajectory, in cosmological terms, and it had actually been bearing down on us, two weeks isn’t even time to send Bruce Willis and the boys up to blow it apart.
A majority of the asteroid experts felt a collision with a vacuum traveler the size of 2012 LZ1, may take out a continent, but might not destroy the planet outright. This is hardly a comfort. The airborne debris would cause instant extreme global distress. Not to worry. They are quick to assure us that a major collision with a large object such as that only occurs every 37,000 year, on average. This fact is not as comforting as they’d like it to be, either. This is because, given that averages encompass a multitude of variables, they do not discount the opportunity for a “one off” incident.
Another pronouncement by the scientific community, found in a number of published reports, is that the sky watchers in observatories located around the planet, who have access to the largest and most sophisticated telescopes on the globe, feel they have catalogued 93% of the globe-busting-proportioned asteroids that would ever come within our “near miss” boundary. This statement begs a few questions. First of all, how can they know the percentage of what they haven’t located based on the number they’ve located? How can they assign a percentage to something unknown? Even if accurate, that still leaves 7% of them up there, circling unseen, waiting to make their closest approach.
If you google “close earth asteroids”, you will see an article that appeared in a past issue of the UK’s The Guardian newspaper which itemizes 81 different near misses which had occurred between August 11, 2011 and January 30, 2012. That figure, in of itself may be worrisome to a segment of the population. That works out to over 100 near misses per year, of which the astral gazers admit they don’t know where, on average, seven of them are, how big they might be or how close they will approach.
The bright minds at NASA and the greater space community are to be commended for trying to ease the worry of citizens concerned for asteroid collisions as each close encounter is dutifully reported on. No good would come of mass panic. It may be interested to speculate, however, what their reaction would be if they knew, with 100% certainty, if Earth was in the path of a planet killer-sized asteroid, would they tell us? Should they?
It’s not like impacts never happen. They do. Most break up in the rigorous entry into the atmosphere to become shooting stars, instead of a threat to our existence. Indeed, the next really close flyby of a space-bound boulder large enough to wipe us out isn’t until 2028… that they know of. That is when 2001 WN5 will make an appearance a scant 140,000 miles away. That is even closer than 500 yard-wide 2005 YU55 which slipped by us last November at a distance of 198,000 miles. To put this into perspective, the moon is approximately 250,000 miles from us.
Knowing these celestial objects are on fairly stable, predictable paths is not very consoling for some. Given the enormous distances these weighty wanderers travel, any slight change in their trajectory can have a significant impact over the route they traverse. That slight change is provided by a process known as the Yarkovsky Effect. This effect is named for a Russian engineer from the 1800’s who deduced that a space-borne object’s trajectory would be altered by the absorption and radiation of heat when in proximity to sunlight. It would be extremely difficult to anticipate the change in direction caused by the effect due to the enormous variables at play such as they size, contours, mass and exterior features of the object. They know, with certainty, that the more solid the object, the more pronounced the effect, due to the greater ability of denser objects to accumulate and retain heat. Unfortunately, they have no real way to quantify these differences in any exacting fashion. They know the orbits of these near miss threats are being affected but don’t know by how much or to what result.
Experts would agree there is no point in going around wondering if the sky is falling but the possibility is there for us all to consider. Making the most of each day would be a great way to deal with it.