Most of the popular viewpoints that we have about outer space has to do with the perception that weightless astronauts float gently above our orb, slowly traversing orbit after orbit with nary a care. But space is not such a gentle, hospitable place as evidenced by a couple of close encounters in the past few weeks.
The space station, orbiting the Earth since 1998, and its astronauts, were just this past week, threatened by some detritus that had been left behind a few years ago on another project. This small, finger sized piece of garbage and its attached 100 cm length of string are in a strange oblong orbit which apparently makes it a touch difficult to predict positionally. It also means that it intersects with a whole lot of other orbits, including that of the space station. And given the fact that both the space station and the junk circumnavigate the globe every 90 minutes, it makes physical intersection a real possibility, if you extrapolate things into the realm of months and years. That possibility became probability a couple of weeks ago. NASA planners calculated that the space station and the space junk were both going to pass within 1 kilometer of each other. They immediately ordered the astronauts into the Soyez capsule attached to space station in case a worst case scenario materialized in the form of a collision.
Keeping with the theme of space detritus, last month we on spaceship Earth had a similar adventure with a piece of interplanetary space debris. It came in the form of an asteroid named DD45, a potato-shaped hill smaller than a hundred metres along its largest axis. In absolute term it also missed us. In relative terms, its distance was a whisker-thin 78,000 kilometres.
In both cases it was over before we knew it and nothing other than worry was the fallout. But it again there was a nagging fear, that perception and reality are sometimes not one and the same. In spite of what we refer to as “astronomical distances”, it appears, space can be a crowded place from time to time.
So what is the big deal? The space station is hundreds of tonnes and the threatening projectile a few 10s of grammes, an almost infinitesimal fraction of the mass of the space station. And the ratio of the respective masses between DD45 and the Earth is so small as to defy comparison. How could things so small in relation to the bodies being potentially impacted, be of any concern? The question is not a spurious one. Based on what we experience in the everyday world, there is no way a feather could every pose a threat to human. In no circumstances that we experience in our day to day lives, can this be possible. Even our colloquialisms reflect it. Who hasn’t heard the expression “you could have knocked me over with a feather”? It represents our reality. If something has the mass of a mosquito it cannot pose any threat. The size differential is the key, and it is verified over and over again by our daily experiences.
But stepping out into the realm of outer space requires us to to change that perception, one that has been honed by a million of years of living within the low velocity ecology of the Earth. In outer space velocity differentials are huge and relative differences can be hundreds of times larger what we experience on Earth. And there is more. Newton tells us that the energy of something is the square of its speed. And that is a critical expression. If you double the speed of something, you quadruple its energy. Treble the speed and you get nine times the energy; five times the speed, twenty-five times the energy! If the speed is one hundred time faster, the energy is magnified an astounding ten thousand fold. And now you are on to something. With that type of mathematics a paint chip becomes equivalent of a cannonball and a asteroid a planet wrecker.
So the next time you see a NASA video of a space walking astronaut, don’t be fooled by the perception of slo-mo floating. Space is not friendly and surprises and potential catastrophe await us every step of the way.
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