"Nothing in life is to be feared. It is only to be understood." - Marie Curie

"At any rate, I am convinced that He [God] does not play dice." - Albert Einstein expressing his dislike of quantum mechanics.

"If I could remember the names of all these particles, I'd be a botanist." - Enrico Fermi commenting on the profusion of subatomic particles discovered during the early 1950s.

"I think I can safely say that nobody understands quantum mechanics." - Richard Feynman

"Strings create everything, including space and time and even us." - Jim Gates

"not even false" - Wolfgang Pauli expressing contempt for an idea not even good enough to be considered "false".

"Who ordered that?" - I.I. Rabi expressing dismay at the identification of the muon, a hard-to-account-for particle whose mass is 207 times the mass of the electron.

"All science is either physics or stamp collecting." - Ernest Rutherford

"Anyone who expects a source of power from the transformation of these atoms is talking moonshine." - Ernest Rutherford made this statement in the mid-1930s referring to the potential for nuclear fission, a process that now powers nuclear reactors and the atomic bomb.

"A black hole has no hair" - John Wheeler commenting on the idea that that the properties of a black hole are limited to mass, charge, and angular momentum.

"I can't think that it would be terrible of me to say--and it is occasionally true--that I need physics more than friends." - J. Robert Oppenheimer

"On the infrequent occasions when I have been called upon in a formal place to play the bongo drums, the introducer never seems to find it necessary to mention that I also do theoretical physics." - Richard Feynman (A photograph of Feynman drumming appeared in the beginning of his introductory physics textbook.)

"Poets say science takes away from the beauty of the stars--mere globs of gas atoms. I too can see the stars on a desert night, and feel them. But do I see less or more?... It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined it. Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were a man, but if he is an immense spinning sphere of methane and ammonia must be silent?" - Richard Feynman

"The more I examine the universe and the details of its architecture, the more evidence I find that the universe in some sense must have known we were coming." - Freeman Dyson

"Nothing is too wonderful to be true, if it be consistent with the laws of nature; and in such things as these experiment is the best test of such consistency." - Michael Faraday

"Science and everyday life cannot and should not be separated." - Rosalind Franklin

"Only by doing the best we can with the very best that an era offers, do we find the way to do better in the future." - Frank Drake

"The laws of nature are constructed in such a way as to make the universe as interesting as possible." - Freeman Dyson

"The more we know about the universe, the more pointless it seems." - Steven Weinberg

"What I cannot create, I do not understand." - Richard Feynman

"Anyone who is not shocked by quantum theory has not understood it." - Niels Bohr

"If I were forced to sum up in one sentence what the Copenhagen interpretation says to me, it would be 'Shut up and calculate!'" - David Mermin (also attributed to Richard Feynman)

"Look here, I have succeeded at last in fetching some gold from the sun." - Gustav Kirchhoff

"Understanding is, after all, what science is all about-and science is a great deal more than mindless computation." - Roger Penrose

"Science is built up with facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house." - Henri Poincare

"The scientist does not study nature because it is useful to do so. He studies it because he takes pleasure in it, and he takes pleasure in it because it is 'beautiful.'" - Henri Poincare

"My God, space is radioactive!" - Ernie Ray, on the discovery of Earth's radiation belts.

• How the gravitational force between two masses depends on their separation (shapes the universe).
• How the electrostatic force between two charged particles depends on their separation (holds the atom together and determines chemical activity).
• How the "strong" force between nucleons depends on their separation (stabilizes the nucleus against electrostatic repulsion of the protons).
• How the binding energy per nucleon depends on atomic weight (makes possible fusion--that's what happens in the sun--and also fission).
• How the density of water depends on temperature (enables aquatic life to survive cold winters).
• How the arrangement of carbon's four outer electrons enables the wild variety of carbon compounds, especially those essential for life.
• How dark matter is required to provide enough gravity so that matter in the primordial universe clumps together (to begin the formation of stars and galaxies).
• How the increase in temperature vs. depth for Earth creates the "oil window"--7,500 feet to 15,000 feet--where dead organisms were cooked into oil.
• How the absorption of infrared radiation by gases in Earth's atmosphere depends on wavelength; the resulting greenhouse effect provides us with temperatures that enable life to flourish.
• How the absorption of ultraviolet radiation by ozone depends on wavelength; this absorption protects us from ultraviolet light from the sun.
• How Earth's magnetic field protects us from the solar wind, the stream of charged particles emanating from the sun. (In fact, a strong solar flare during the Apollo mission could have proved fatal to the astronauts.)
• How the neutron mass is greater than the proton mass, so the free neutron can decay into a proton and electron (and anti-neutrino). Had the proton mass been greater than the neutron mass, most of the protons in the universe would have decayed into neutrons, and there would hardly be any hydrogen nuclei left. Without hydrogen, there would be no stars, no organic chemistry, and no carbon-based life.
• How the force of gravity is 39 powers of ten weaker than the electromagnetic force. Had gravity been much stronger, stars would have burned out much faster, and life would not have had enough time to evolve.

• What is dark matter?
• What is dark energy?
• Can string theory be tested experimentally?
• Must the properties of the universe enable us to evolve to observe it? (This idea is called the anthropic principle.)
• Can we achieve room temperature superconductivity?
• Can the theories of gravitation and quantum mechanics be merged?
• How can we explain the "Pioneer Anomaly?"
• Does the proton decay?
• Do quarks and leptons have internal structure? (Protons and neutrons are made of quarks; the electron is a lepton.)
• Why does the observable universe have hardly any antimatter?
• Do black holes evaporate? (as per Stephen Hawking's prediction)
• What happened at the Big Bang? (and before?)