Some people are quite blase about these things but the single thing that is absolutely certain is the Earth will end one day but we have had a good run of it.
In the 200,000 years since Homo Sapiens began roaming the land we've built cities, created complex languages and sent robotic scouts to other planets. It's difficult to imagine it all coming to an end. Yet 99 percent of all species that ever lived have gone extinct, including every one of our hominid ancestors who came down from the trees with us.
In 1983, British cosmologist Brandon Carter framed the "Doomsday argument," a statistical way to judge when we might join them but as human activity is messing with the atmosphere and severely disrupting almost all life on the planet, the calculations could be out.
The correct answer to how long us humans have left is of course unknown, but two new studies suggest a collision with Mercury or Mars could doom life long before the Sun swells into a red giant and bakes the planet to a crisp in about 5 billion years.
Astronomers have known for years that our Milky Way and its closest neighbour, the Andromeda galaxy, (a.k.a M31) are being pulled together in a gravitational dance, but no one was sure whether the galaxies would collide head-on or glide past one another. Precise measurements from the Hubble Space Telescope have now confirmed that the two galaxies are indeed on a collision course, headed straight for a colossal cosmic collision.
No need to panic for the moment, as this is not going to happen for another four billion years.
An asteroid five miles wide would cause major extinctions, like the one that may have marked the end of the age of dinosaurs. For a real chill, look to the Kuiper belt, a zone just beyond Neptune that contains roughly 100,000 ice-balls more than 50 miles in diameter. The Kuiper belt sends a steady rain of small comets earthward. If one of the big ones headed right for us, that would be it for pretty much all higher forms of life, even cockroaches.
Every few hundred thousand years Earth's magnetic field dwindles almost to nothing for perhaps a century, then gradually reappears with the north and south poles flipped. The last such reversal was 780,000 years ago, so we may be overdue.
Worse, the strength of our magnetic field has decreased about 5 percent in the past century.
The magnetic field deflects particle storms and cosmic rays from the sun, as well as even more energetic subatomic particles from deep space. Without magnetic protection, these particles would strike Earth's atmosphere, eroding the already beleaguered ozone layer which we have carelessly made as holey as Swiss cheese.
Finally, the studies show that by 2040, machines will match human intelligence, and perhaps human consciousness. Then they'll only get even better and become more autonomous and become more powerful and us puny humans will be no match if they decide they should be the ones running the show.
It may be a gloomy outlook for us humans but its something our future ancestors will hopefully sort out, probably by shifting themselves to another planet.