The Future Is Wild

 

The Formation of Our Solar System Original Image by NASA, released to the public domain.

 

The Earth is a pretty amazing place. At around 4.54 billion years old the Earth has already had a rich history filled with incredible events including the beginning of life, a few mass extinction events, and at one stage the Earth even became a snowball. That’s not even mentioning us; humans, the most amazing forms of life on the planet.

Our Planet orbits the Sun, a 4.6 billion year old star that formed after the collapse of a molecular cloud and now exists in the Milky Way Galaxy. The Earth currently sits in the Sun’s habitable zone, a region in space that is the right distance away from the sun to support life and house water. We are quite lucky to be around today when our planet can accommodate us and a host of other flora and fauna but, like anything in life, it all comes and goes.

 

When the River Runs Dry

Let’s take a trip forward in time and look at some spectacular predicted events that will impact Earth and our solar system. Humans probably won’t be around any more when most of these events occur but you can humour yourself and pretend that we will be.

In one billion years, an estimated 27% of the Earth’s water will have moved underground into the mantle. The remaining surface water will eventually be lost to evaporation due to the sun’s increasing luminosity.

The sun is currently increasing in luminosity by 10% every 1 billion years. This is going to be annoying for anyone still around in 1.4 billion years because the Sun’s habitable zone will have moved outside of Earth’s orbit and closer to Mars’ orbit. At this time the average temperature on Earth will be a balmy 47°C. I guess that’s a good reason to buy some property on Mars before the prices sky-rocket

 Earth will from an atmosphere similar to Venus Original Image by NASA, released to the public domain.

 

A Collision on a Galactic Scale

But that might only save us for a few more billion years. Ever heard of the Andromeda Galaxy? It’s a massive spiral galaxy that’s 2.5 million light years away from us. It contains an estimated 1 trillion stars, which is more than double the estimated 400 billion stars in the Milky Way. You can actually see the Andromeda Galaxy on a moonless night. “Wow that’s amazing! I’ve got to get a good look at this!” I might hear you say. Well slow down there! You’ve got plenty of time to see it now but I suggest you wait two billion years when it’s a bit closer.

The view would be pretty nice from Earth in a few billion years Original Image by NASA, released to the public domain.

 

That’s right, the Andromeda Galaxy is currently approaching the Milky Way at 120 kilometres per second! In roughly two billion years, the galaxies will pass each other like two cosmic jousters before swinging back and colliding over and over. This will happen until the super-massive black holes central to the two galaxies converge approximately five billion years from now.

Oh dear! That doesn’t sound good for our solar system. Actually it’s not as bad as it seems… maybe. The sun’s luminosity would have increased nearly 40% by then and Earth would be completely inhabitable, devoid of life and water. But if we were, say, still around on Mars at the time there’s a 50% chance our solar system will remain as part of the newly formed galaxy (often dubbed ‘Milkdromeda’) with no adverse effects.

 

This Could be a Bumpy Ride…

There’s also a 12% chance our solar system will be flung out with a lot of other ejected material and a 3% chance that the solar system will ‘jump ship’ with the Andromeda galaxy during its first pass of the Milky Way.

But nothing is certain here and it is possible (although incredibly unlikely) that our Sun will collide with another star or that it will get swallowed up by one of the super-massive black holes at the centre of these galaxies taking all the planets we know and love with it. But nothing is forever.

Even if our solar system does make it through this cosmic calamity, our Sun’s main life sequence will end shortly after and it will turn into a red giant. The Sun’s radius will increase by a factor of 250 and its luminosity by a factor of 2700. Close planets like Mercury, Venus and dear old Earth will probably be swallowed by the giant star. This is likely to occur between five and seven billion years from now.

A Scorched Earth close to the Red Giant Original Image by Fsgregs via Wikipedia (CC BY-SA 3.0)

 

Don’t worry though, as it is predicted that Saturn’s moon Titan might become habitable at this time. There’s another investment opportunity!

 

An Unknown Fate

In roughly 12 billion years our Sun will turn into a white dwarf and could remain that way for some time. The Sun will cool indefinitely from this point for an unknown period of time but it should still harbour a habitable zone. However this zone will be much closer to the Sun than it is at present day. It could be as close as 750,000km compared to 150 million km, which is roughly the distance from the Earth to the Sun now.

Anything beyond here is too difficult to predict and I won’t scare you any further on how screwed our planet eventually is. Perhaps our future descendants will reach out into space to colonise distant planets when our own solar system becomes inhospitable. Or maybe we will figure out a way to move Earth continually into the habitable zone with some zany engineering ideas.