I have discovered the secret of happiness - it is work, either with the hands or the head. The moment I have something to do, the draughts are open and my chimney draws, and I am happy.

If you want to see birds, you must have birds in your heart.

The U.S. had about 10,000 nuclear warheads. It is estimated that the U.S. is heading towards having 6,000 nuclear warheads in the year 2012.

I still find each day too short for all the thoughts I want to think, all the walks I want to take, all the books I want to read, and all the friends I want to see.

Science is a capital or fund perpetually reinvested; it accumulates, rolls up, is carried forward by every new man. Every man of science has all the science before him to go upon, to set himself up in business with. What an enormous sum Darwin availed himself of and reinvested! Not so in literature; to every poet, to every artist, it is still the first day of creation, so far as the essentials of his task are concerned. Literature is not so much a fund to be reinvested as it is a crop to be ever new-grown.

I seldom go into a natural history museum without feeling as if I were attending a funeral.

There is an international treaty framework for this. It's the Nuclear Non-Proliferation Treaty (NPT). Most countries in the world are members of the treaty.