The upper layer of the skin, the epidermis, which consists of flattened dried-out dead cells, is replaced continously throughout life. As cells are worn away from the top layer of skin they are replaced by new cells from below. Tattoos are injected deeper into the skin into a layer called the dermis below where the cells that make the epidermis come from. This means that the dye stays where it is put for life.
Show featuring dermatologist Jane Sterling about the skin and skin diseases

The rumbling sounds you hear are your stomach gearing up to accept food. Whenever we feel hungry we usually placate our stomachs with some food soon afterwards and so the digestive system prepares itself in advance by releasing digestive juices and increasing the peristalsis of the stomach muscles. When we eat the food dampens the sound of the juices squirting around so the stomach sounds quiet. When we are empty though there is nothing to soak up the sounds and the result can be noisy !

This is a myth ! Although the Great Wall is extremely long it is only about 5 metres or so wide. At distances greater than about 20 km up (about twice the height of Mt. Everest), a person even with perfect eyesight, but without the aid of a telescope or binoculars, cannot physically resolve something that small on the ground. Allowing for the shadow cast by the Great Wall (making it wider) or sand accumulating on the windward side you might be able to see it from 60 km up, in places, but since this is still too low for a spacecraft to orbit, it's safe to say that you can't see it from space. Indeed, Neil Armstrong and other astronauts from the Apollo missions have all declared that it cannot be seen from space with the Naked Eye. Other man-made objects can though, such as cities because of their bright lights.

Tea leaves contain much more caffeine that coffee, but since less Tea than coffee is used in making a cup of each beverage, a cup of coffee actually has a much great caffeine content and hence you get a greater hit from a coffee than a tea. Unless you brew your tea really strong and make weak coffee !
Article about why plants make caffeine and how caffeine affects the body.