The distances are so great and vast that they need a large measurement to easier express the distances. They use Astronomical Units (AUs) for distances within our solar system.
Fossil Fuels. However, producing solar, water and wind power plants and generators cost a lot of energy, generated by fossil fuels. The problem is that 'green' energy sources don't repay the amount of energy used to make them. Fossil fuels are bad guys, but don't think placing solar panels everywhere will stop the greenhouse effect. Not until their efficiency is high enough to produce more energy than is put into them.
Fossil fuels are not effected by acid rain.
Most of the liquid water on Earth is found in the oceans, in fact the percentage is so big that it comes as if almost all liquid water on our planet is in the oceans while the water from the lakes, rivers, ponds etc. is just a minor part of the whole.
The water from the oceans contains salt, thus making it a salty water and not suitable for drinking as it is naturally. For this water to be consumed and be part of the daily of the humans for drinking it needs to be desalinated. Desalination is a process that gets the salt out of the water and makes it suitable for drinking. This is not an unknown or untested process, it is something that is practiced for decades now mostly on the Arabian Peninsula where there isn't any fresh water resources.
