Sending humans to other planets may cause danger. We dont fully know what these planets are capable of doing. If there is such a thing as life on other planets then we still dont know weather or not life there is friendly or not. They could be harmful, because just as we dont know know exactly who or what they are, they dont know who or what they are either, so its a high chance they may want to defend themselves.
By which organisms that contain the pigment chlorophyll convert light energy into chemical energy which can be stored in the molecular bonds of organic molecules.
Stars produce energy from nuclear reactions, primarily the fusion of hydrogen to form helium. These and other processes in stars have lead to the formation of all the other elements.
