Sattelites don't need any fuel to stay in orbit. The applicable law is...."objects in motion tend to stay in motion". Having reached orbital velocity, any such object is essentially "falling" around the earth. Since there is no (or at least very little) friction in the vacuum of space, the object does not slow.... It simply continues.
Sattelites in "low" earth orbit do encounter some friction from the very thin upper atmosphere, and they will eventually "decay".
:)
Our solar system consists of the sun and the 9 planets and their moons.
The galaxy is outside our solar system.
9.8 ms^-2 is acceleration
The heat and energy of coal burning is more easier and more efficient to turn into electricity than any method using renewable resources.
Systematic is just a certain way of doing something. So science being systematic may just refer to the scientific method or how theories are proved in science by repeating the scientific method over and over again.
