The gases surrounding the Earth or any astronomical body of sufficient mass, held together by the gravity of the body.

A darkened enclosure in which images of outside objects are projected through a small aperture or lens onto a facing surface. A camera obscura uses the same principles as a regular camera.

A rudder is a device (vane) used to steer a ship, boat, submarine, hovercraft, aircraft, or other vessel that moves through a fluid (generally air or water).

We think of time as the ways in which we measure the passing of time, such as a clock or watch, or perhaps a measured interval of time such as an hour or minute.

Any water-soluble compound having a sour taste and capable of turning litmus red and reacting with a base to form a salt. Acid has a pH-level of less than 7.0 (A pH of 7 is neutral).

Rain which is unusually acidic (pH of less than the natural range of 5 to 6), caused mainly by atmospheric pollution with sulphur dioxide and nitrogen compounds.

A mixture of gases (especially oxygen) required for breathing; the stuff that the atmosphere consists of.

Air pressure is the weight of the atmosphere pressing down on the earth. It is measured by a barometer in units called millibars.

Albert Einstein (14 March 1879 – 18 April 1955) was born in Germany and was a Jewish philosopher and author, who is widely regarded as one of the most influential and best known scientists and intelle [..]

Relating to or containing an alkali, hence having a pH greater than 7. Alkaline batteries have potassium hydroxide as its electrolyte and a zinc / manganese dioxide cell.