Earth has been able to accommodate humans for thousands of years because natural resources that support life are plentiful. We have had the essentials for living - most notably air, water and minerals. Add the sun's energy and you have an ideal environment for the human race.
However, scientists tell us that in about two billion years or so, as the sun approaches its expiration date, our star will expand in size and increase its energy emission rate in such a way that oceans will boil and the environment will be unsustainable for human life.
In the meantime, we must keep in mind the possibility that a thousand-mile-wide asteroid could hit Earth. It has been estimated that such a life-ending event could happen at a rate of about one every 300,000 years. While it is true that several agencies and groups around the world are on the lookout for Near Earth Objects (NEO) such as large asteroids that may cross our planet's path, there is little we can do to divert one of these huge rocks.
Of course, there is the ongoing threat of total nuclear war which would last only an hour or so, but could eliminate most life on Earth. Fortunately, the horrific thought of this threat has acted as a deterrent to such wars for the last 75 years. We can only hope that it stays that way.
Even if Earth survives these various threats, the human race is consuming our natural resources at a rapid rate and we do not even have a solution to the effective disposal of waste products. As the world population continues to grow and resources become scarcer the pressure to leave our home planet will increase dramatically. However, leaving Earth is only part of the challenge for human survival.
To read more, click here.