1.   A layer of gases, including those which are known as the greenhouse gases, surrounds the Earth.

2.   A man who receives an electric shock does not ask himself whether he believes in the form of energy known as electricity.

3.   A precise statement of this idea is known as the second law of thermodynamics.

4.   About this time the Club was given its second trophy and which today is known as the Lovell Bowl.

5.   According to present-day ideas, a star begins its career by condensing out of a cloud of dust and gas known as a nebula.

6.   Aiding his efforts was an improved method for dating rock known as uranium-lead isotope analysis.

7.   Alaska is known as the last frontier.