The sun emits its own light whereas the moon reflects light from another source.
Fusion and fission within the sun fuels the sun. Within the sun, two protons fuse to form a deuteron. A third proton then fuses with the deuterons to form helium-3. Two helium-3's fuse to form a beryliium-6. The beryllium-6 degenerates (undergoes fission) into two protons and a helium-4. The final step also releases two neutrinos, two positrons and gamma rays. Meanwhile, light is emitted (see the points of "explosions" within the picture provided va the link below).
Light travels in a straight line until it hits an object. Once light hits an object, it can be absorbed (taken in) or reflected (bounced off of). Our eyes contain receptors that interpret reflected light as colors and shapes. The moon reflects the light emitted from the sun.
Sun's light originates from within the sun. Nuclear fusion takes place inside the sun and this process generates energy, which we receive in the form of light energy. Sun's light has enough energy to heat our planet and maintain temperature for survival. Sun's light is also necessary for the process of photosynthesis, the process by which green plants (that contain chlorophyll) make glucose and generate oxygen. Sun's light takes about 8 minutes to reach earth. The sun's light can be harvested using solar cells, solar cookers, etc.
The moon does not have its own light or fusion; no other energy generating process take place on the moon. In fact, the moon receives the sun's light just like our earth, and the moon reflects part of that light to earth. Since the moon is very close to us, it takes only about 1 second for the moon's light to reach earth. The moon's light is devoid of any energy and hence cannot be harvested.
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