Why Doesn't Earth Just Fang Off Into Space?

Hot on the heels of last weeks Ask ARSE about why we only see one side of the moon, we have another question about little space bodies and big space bodies.

This time the stakes (or mass) is a little higher. 

"Hey guys thanks for getting back to me. My question was about planets and stars like out sun and Earth. Why is it that we are moving so fast but we stay in one general spot in the solar system? And what would it take for us to exit it?" - Matthew

Thanks for the question Matthew and, like we said, it ties into last weeks Ask ARSE about the Earth and moon. Specifically in regards to gravitational pull. 

Astronomers long wondered if Earth could just fling off the sun's orbital influence and go hurtling through the darkness for a long while.

But in the 16th a man named Johannes kepler discovered that while the Earth's orbit around the sun isn't perfect, it is constant and makes the same path around the sun. This is what we call a year.

This discovery is the first of Kepler's Laws of Planetary Motion.

Kepler's Law of Planetary Motion were vital in Newton's 1684-86 formation of Law of Gravitation Theory between our moon and Earth. In essence, Newton found that the motion of bodies subject to central gravitational force don't always follow a perfect orbit. 

In fact, most take paths that are more oval in shape depending on the total energy of the planetary body.

Here's how that looks with the first four planets of our solar system as they orbit our sun.

 

 

Planets, like Earth, orbit stars because they are not travelling fast enough to escape their gravitational pull. But, they're travelling fast enough around the star not to be pulled into the star itself.

This is known as conservation of angular momentum.

If a planetary body was still, or even too slow, it would be dragged into the sun. But thanks to a little something called speed, Earth is maintaining an orbit between pulling away and being dragged into our sun. 

Think of it like Napoleon Dynamite playing tetherball forever.

 

 

Earth is moving sideways in relation to the sun at a rate of 3 km/second. 
This seems fast but its not enough to escape the gravitational pull of the sun and send Earth "fanging" into space.

Think of the rope/tether as the gravitational pull of the sun.

If there was no air or friction of any kind like space, the ball (Earth) would spin forever without getting closer to the post. And Napoleon could go home while the ball goes on and on spinning.

Sure, we could escape the sun's gravity.
But we'd need enough force to snap the rope/tether and that isn't happening anytime soon without a massive outside force like an asteroid. And so, Earth keeps going round and round. 

Something that's moving really fast on a hard angle (like a comet) can enter and exit without becoming stuck in our solar system as floating space rock or mini-moon.

 But the most interesting question is this:

How Fast Must Earth GoTo Leave the Solar System?

On the surface of the Earth, the escape velocity is about 11.2 km/s, which is approximately 33 times the speed of sound (Mach 33) and several times the muzzle velocity of a rifle bullet (up to 1.7 km/s).

However, at 9,000 km altitude in "space", it is slightly less than 7.1 km/s.

So in basic terms, Earth wold need to go over twice as fast in orbit to leave its pathway and venture out into the universe.

 

 

Another way to look at it is the Earth is "falling" around the sun. 

To picture this, think of a coin in one of those shopping centre funnel things. 

Eventually the coin reaches the middle and falls into the hole. But that's because our gravity is pulling it down into the Earth's core. 

What if the coin is dragged towards the hole (the sun) but has so much spinning momentum that it never can leave the funnel?

You get a stable, predictable orbit. 

What if the coin is going stupid fast.?
Like two times as fast as what's needed to keep it in stable orbit in the funnel.
The coin is exiting that funnel.

And that's what it would take for Earth to "fang" off out of our solar system.

We hope this answers your question mate!

If you loved this answer and found it interesting, please share with a friend to spread ARSE.

#Space_Aus