
Natural resources such as , (crude oil) and take thousands of years to form naturally and cannot be replaced as fast as they are being consumed. It is projected that fossil-based resources will eventually become too costly to harvest and humanity will need to shift its reliance to such as solar or wind power. An alternative hypothesis is that carbon-based fuel is virtually inexhaustible in human terms, if o.

Nuclear power in space is the use of in , typically either small systems or for electricity or heat. Another use is for scientific observation, as in a . The most common type is a , which has been used on many space probes and on crewed lunar missions. Small fission reactors for Earth observation satellites, such as the , have also been flown. A

Passive nuclear safety is a design approach for safety features, implemented in a , that does not require any active intervention on the part of the operator or electrical/electronic feedback in order to bring the reactor to a safe shutdown state, in the event of a particular type of emergency (usually overheating resulting from a or loss of coolant flow). Such design features tend to rely on the engineering of components such that their predicted behavio.

Solar power produced around 1.3 terrawatt-hours (TWh) worldwide in 2022, representing 4.6% of the world's electricity. Almost all of this growth has happened since 2010. Solar energy can be harnessed anywhere that receives sunlight; however, the amount of solar energy that can be harnessed for electricity generation is influenced by , geographic location a.