The universe is trying to kill you.The Universe is the most dangerous place that you can imagine. There are a lot of perils: asteroids and comets, supernavae, gamma ray bursts and finally our star, the Sun. Every source of danger is examined in nine chapters introduced by a fictional short story, that is scientifically correct. In these introductory stories, Plait describes a possible scenario in which Earth is shotted by, for example, a comet o a great asteroid, like the one that leaves the Meteor Crater in Arizona
Philip Plait, Death from the skies
or the ones that probably caused the dinosaurs extintion.
In order to prevent a bad encounter with a great object, physicists describe a lot of possible solutions: in the list there are a nuclear bomb, an impact against an artificial object (like Deep Impact with Tempel 1) or try to change the bullet's trajectory using the gravitational force of an ather astetoids. This last solution is proposed by B612 Foundation and, like the others, present a lot of difficulties, but is technically realizable now!Some possible problems are, for example with shot solutions, that the object is broken into too big pieces, while for the gravitational solution we must demonstrate a very precise control of the gravity. These are the only enemies we can prevent, but against the others we could realize some particular protection, like radiations from Sun or from supernovae explosions. In this last case, the probability to be shot is 1/10000000, against 1/700000 of an asteroid shot, that is a probability actually higher than terrorism!
Another danger from outer space is an... alien attack! Don't worry! I don't mean the little green men from Mars, but simply eventually microscopic life present in asteroids or comets. An attach like this has a very low probability, first of all because the aliens must survive at Earth atmosphere, and after because they have a low probability to interact with DNA developed in our environment: following our knowledge, we must remeber that in the Universe our planet is unique!
I don't know if we are alone or not, but in this moment it is so...
In the last part of the post I spend some words about Sun: