By David Ward
The universe is a scary place. Lurking out there in the depths of the cosmos are unbelievably massive black holes sucking up everything in sight. Not to mention supernova explosions, huge stars in their death throes blasting their guts out across the vastness of space. Then there are entire galaxies slamming into one another, hurling hapless planets like ours into their host stars or out into the cold and darkness of interstellar space.
But all that is out there, a long ways away and we do not have to worry about it, right? Have you ever heard of cosmic rays? Discovered in the early 1900s, they were first thought to be some kind of mysterious radiation coming from space. Now we know they are actually bits and pieces of atoms, a kind of cosmic detritus, shot at us at fantastic speeds from the most violent events of the universe like the ones described above.
Luckily we have several layers of protection from this onslaught. The first is way out there at the outermost edge of our solar system, billions of miles from earth, at a place called the heliopause. Think of it as a shock wave where particles streaming outward from the sun slam into the barrage coming at us from the universe. That shock wave acts like a barrier preventing many of the incoming particles from getting into our solar system. Unfortunately for us, for the past 20 years or so the sun has been putting out less energy than normal, weakening that protective barrier and allowing more cosmic rays to pour through and reach the earth.
When the 27 Apollo astronauts traveled from the earth to the moon from 1968 to 1972, they did something no other human has done before or since — they left the protective magnetic field surrounding the earth. Each of those astronauts experienced something entirely unexpected, a tiny flash of light in their vision every couple of minutes or so. NASA physicians decided those flashes were cosmic rays careening through the liquid in their eyeballs! It does not make you real anxious to take a trip into space, does it? In the International Space Station, the crews are much safer because they are still within the earth’s magnetic field.
The third layer of protection we have from these fast-moving particles is our atmosphere. At about 35 miles up they start to strike air molecules and break up into smaller and smaller pieces known as muons. Slowing down, they pose a lesser threat to us and other living organisms on earth. A couple of hundred muons zoom through your body every second and if one hits the wrong piece of genetic material in a cell nucleus it can be harmful.
If you spend a lot of time hanging out on the summit of Mount Everest or if you fly in jets on a regular basis, your risk goes up. Think of it as a frequent flyer hazard. Do you want to limit your exposure to these nasty little particles being shot at you by the universe? Consider taking up residence on the bottom floor of an underground parking garage!
What does this all mean for a six-month trip to Mars? Scientists are debating that very issue and some think an astronaut would receive the equivalent radiation of a CAT scan every day. Also, Mars has no magnetic field surrounding it like the earth and very little atmosphere, putting humans at greater risk the entire time they are on the red planet — unless they can find an underground parking garage around somewhere.
What to see
If you dare to go outside and look up at the stars tonight, here is what you might see. The only planet out there in the evening sky is Mars, now all by itself and feeling lonesome in the southwest sky just after dark. As we rush away from the red planet, it is getting dimmer, just a shadow of its glory last summer when we were much closer.
In the east, look for the beautiful little star cluster called the Pleiades. It appears to us as a small dipper about the size of the full moon. Just below, the reddish star Aldebaran marks the angry red eye of Taurus the Bull. Lower still and rising not too long after it gets dark, the brilliant stars of Orion herald the coming of winter for stargazers.
If you arise before dawn, look for the bright planet Venus dazzling us in the eastern dawn sky. She will be at her brightest in early December. If you have a small telescope, the planet will look like a tiny crescent moon hanging delicately in the morning sky.
Do not worry about those muons when you are out there stargazing. Just as many are zipping through you when you are inside!