Ever seen a space shuttle launch and wondered why is the shuttle leaving behind a trail of burning fuel while taking off? You might have or might not have.
But believe it or not, gravity is the reason
GRAVITY: A PULL THAT YOU CANNOT AVOID
As much as gravity makes it possible for you to stay on the ground (and not jumping like a rabbit on the moon which has gravity one-sixth of the Earth), it makes pretty difficult for anything to leave Earth’s sphere of influence a.k.a gravity.
So you will be thinking of gravity as a curse. But remember it is this gravity that prevents the atmosphere from escaping into space. It is this gravity that helps bring down the rain. So be thankful.
Let’s suppose you are hell bent on leaving this beautiful planet anyway, as the space shuttle carrying astronauts do. If so, then in order to leave this planet, you have to produce enough energy and reach a velocity to break away from the gravitation pull of Earth. This velocity is termed as “Escape velocity” which is 11.2 km/s (7 miles per second or 40,000 km/h).
Rocket engines burn huge volumes of fuel rapidly to reach this “escape velocity.”
This is why space shuttles are so big just to carry enough fuel for the outward journey. Probably this is why rockets are so damn expensive.
IS THIS SAME FOR ALL PLANETS?
Of course not. Different planets in the solar system have different gravitational strength and so their “escape velocity” differs.
Compare this. On Jupiter, you’d have to reach a near impossible 217,000 km/h (135,000 mph) escape velocity to break free from it because the planet is twice the size of all the other planets combined. Whereas on Mercury, the smallest planet now (sorry pluto), the escape velocity is 15300 km/h (9507 mph). That’s a whopping 15 times change in the escape velocity.
Have a look at this animated GIF which shows what ‘escape velocity’ you’d have to achieve to leave every planet in the solar system.