Calcium & Vitamin D
Why does calcium need vitamin D to get into bones? (Vitamin D receptors in the intestine enhance …
Why Is It?
Alcohol & Bacteria
Why does rubbing alcohol kill bacteria? (Disrupts their cell membranes)
Forgetting Dreams
Why can't we remember all of our dreams? (Happens in the deep parts of the brain, perhaps not meant …
Bird Migration
How do birds know when to migrate? (They watch day length, and then wind conditions.)
Gray Hair
What causes hair to turn gray? (Toxins build up and kill the pigment cells in the hair follicle.)
Middle-Aged Eyes
Why do your eyes change over age 40? (Lens becomes less flexible due to aging.)
Spinning Earth
Why does the Earth spin? (Debris came together to form the Earth was spinning)
Green Leaves
Why are leaves green? (Chlorophyll doesn't absorb green light, so it reflects back.)
Camera Red-Eye
Why do flash pictures sometimes give subjects red eyes? (Light reflects off blood-vessel-rich …