a billion years, the sun will have expanded so much that the heat will begin to melt the

earth's surface. So, is there any way us Earthlings can avoid this detrimental event? Can we save

ourselves from the suns ultimate death?

Sure, none of us will be here, assuming we don't find the secret to everlasting life.

But, at the billion year mark, the sun will have used up the hydrogen fuel in its core,

forcing it to burn at its surface. The increased radiation will boil away all of the water

on Earth creating an international desert. Flash forward about 5 billion years, and the

swelling sun will begin literally melting mountains, with most, if not all life on earth

now extinct. Around 7.5 billion years, the expanding sun - now a Red Giant - will engulf

the Earth entirely. Sounds bleak -- so can we avoid this hot mess?

It turns out; our best bet lies in something called "Gravity Assist". A technique we've

been using for years, only to launch space crafts throughout our solar system.

Anytime a spacecraft or satellite comes in close proximity to a planet, gravity grabs

hold. And if the spacecraft arrives at the perfect angle, it's able to use some of the

planets velocity to catapult it further into space. This 'extra' energy comes from the

planet's own energy of motion around the sun. But, as Newton famously said "To every action,

there is an equal and opposite reaction". As the spacecraft uses the Earths gravity

to speed up and move towards Earth, the planet will ever so slightly slow down and move towards

the spacecraft.

Of course, the spacecraft's mass is so small, comparatively, that it gets launched incredibly

far, while the planet experiences little change. But, if we were to increase the spacecraft's

size -- or use an asteroid -- we could potentially move the Earth's orbit away from the sun.

This would take millions of years, and involve large objects coming just close enough to

not collide with Earth, but hey, we've got a billion year head start!

It may seem far-fetched, but it's already happening! On October 9th, 2013, Earth will

be used to gravity assist a spacecraft called Juno, which is on its way to Jupiter. As Juno

flies within 559 kilometers of us, it will use Earth's gravity as a slingshot to boost

its velocity by 7.3 km/s; Meanwhile, Earth will have been moved by a fraction. Juno will

later arrive at Jupiter, in 2016, where it will study the interior of the planet and

help to unveil many new spectacular mysteries of our Solar System.

In order to move the Earth within our billion year timeline, we would need approximately

1 encounter every 6,000 years, using an object with a mass of approximately 10^19kg. That's

19 zeros - somewhere around the size of a 100 km-wide asteroid. In between passes, the

asteroid would slingshot around the sun, fly out to Jupiter, and then be gravity assisted

back to Earth - like one long version of catch between planets. Over millions of years, this

would move Earth to a comfortable 225 million kilometer orbit out from the sun.

And while it is feasible, even with today's technology, it doesn't come without risks.

For one, we may lose the moon, which could ultimately create some extreme weather patterns.

Not to mention, the Earth's spin may increase, making days only hours long. The surrounding

planets, like our new neighbor Mars, would likely have their own orbits destabilized.

And...you know...the asteroid could come plummeting into Earth by accident.

But, perhaps these are the risks we need to take to give our descendants, the planet and

all life on it a few extra billion years.

Got a burning question you want answered? Ask it in the comments, or on Facebook and

Twitter. And if you want to learn more about Juno? Check out its awesome interactive website

we have linked in the description. Special thanks to NASA for inspiring and supporting

this episode, and subscribe for more weekly science videos.