A solar eclipse is when the moon moves between the earth and the sun, so the moon casts a shadow on the earth
It shows up in your stool. Specifically the undigested food includes material that cannot be absorbed by the vili found in the small intestine. Thereafter the material moves to the large intestine, goes through the bowel tract, turns into feces and exits the GI tract via the rectal cavity
If you talk about the process of fission in the nuclear field then the most used is U-235 because is the easiest to use. Have in mind that the majority of uses of uranium is U-238 but the easiest to be used is U-235
