To see or not to see. Bubble Suspension Soap bubbles float on a cushion of carbon dioxide gas. If you want to stay hidden, you'd better stay still.
Most human infants produce ample quantities of lactase for milk digestion.
We are not usually aware of our eyes' limitations. Persistence of Vision Your eye and brain hold on to a series of images to form a single complete picture. Even with our eyes closed, we have a sense of body position - where our arms and legs are, for example, and that we are moving them. Muscles, tendons, joints and the inner ear contain proprioceptors , also known as stretch receptors, which relay positional information to our brains. Pupil Your pupil changes size to control how much light enters your eye.