* Gravity: The Earth's gravity constantly pulls on Hubble, trying to bring it down.
* Orbital Velocity: Hubble is moving incredibly fast, traveling at approximately 5 miles per second (8 km/s) in a direction perpendicular to the Earth's gravitational pull.
* Balance: The combination of gravity pulling Hubble down and its high orbital velocity pushing it forward creates a balance. This balance keeps the telescope in a stable orbit around the Earth.
Think of it like a ball on a string. If you swing the ball fast enough, the string is always taut, even though gravity is pulling the ball down. Hubble is essentially "swinging" around the Earth, constantly falling but never hitting the ground.
Key Points:
* If Hubble stopped moving, it would immediately start falling towards Earth due to gravity.
* The telescope's orbit is not perfectly circular, so its altitude varies slightly.
* Over time, atmospheric drag causes Hubble to slowly lose altitude. This is why the telescope needs occasional boosts from space shuttles (in the past) to maintain its orbit.
* Hubble's orbital path is above most of the Earth's atmosphere, minimizing the effects of drag.
In conclusion, it's not the absence of gravity that keeps Hubble in orbit, but rather the constant interplay between gravity and its high orbital velocity. This dynamic equilibrium allows the telescope to observe the vast universe without falling back to Earth.
