Quantum Theory Cannot Hurt You_ A Guide to the Universe - Marcus Chown [83]
SOLAR SYSTEM The Sun and its family of planets, moons, comets, and other assorted rubble.
SPACE-TIME In the general theory of relativity, space and time are seen to be essentially the same thing. They are therefore treated as a single entity—space-time. It is the warpage of space-time that turns out to be gravity.
SPECTRAL LINE Atoms and molecules absorb and give out light at characteristic wavelengths. If they swallow more light than they emit, the result is a dark line in the spectrum of a celestial object. Con-versely, if they emit more than they swallow, the result is a bright line.
SPECTRUM The separation of light into its constituent “rainbow” colours.
SPIN Quantity with no everyday analog. Loosely speaking, subatomic particles with spin behave as if they are tiny spinning tops (only they are not spinning at all!).
STAR A giant ball of gas that replenishes the heat it loses to space by means of nuclear energy generated in its core.
STRING THEORY See Superstring Theory.
STRONG NUCLEAR FORCE The powerful short-range force that holds protons and neutrons together in an atomic nucleus.
SUBATOMIC PARTICLE A particle smaller than an atom, such as an electron or a neutron.
SUN The nearest star.
SUPERCONDUCTOR A material that, when cooled to ultralow temperatures, conducts an electrical current forever—that is, with no resistance. This ability is connected with a change in the conducting particles from fermions to bosons. Specifically, electrons (fermions) pair up to form Cooper pairs (bosons).
SUPERFLUID A fluid that, below a critical temperature, develops bizarre properties such as the ability to flow uphill and squeeze through impossibly small holes. The best example is liquid helium, which becomes a superfluid below a temperature of 2.17 degrees above absolute zero. Superfluid liquid helium owes its weirdness to quantum theory and the fact that helium atoms are bosons.
SUPERNOVA A cataclysmic explosion of a massive star. A supernova may, for a short time, outshine an entire galaxy of 100 billion ordinary stars. It is thought to leave behind a highly compressed neutron star or even a black hole.
SUPERSTRING THEORY Theory which postulates that the fundamental ingredients of the Universe are tiny strings of matter. The strings vibrate in a space-time of 10 dimensions. The great payoff of this idea is that it may be able to unite, or “unify,” quantum theory and the general theory of relativity.
TACHYON Hypothetical particle that lives its life permanently travelling faster than light.
TELEPORTATION The clever use of entanglement to pin down the exact state of a microscopic particle, in apparent violation of what is permitted by the Heisenberg uncertainty principle. This enables the information necessary to reconstruct the state of the particle to be sent to a remote site.
TEMPERATURE The degree of hotness of a body. Related to the energy of motion of the particles that compose it.
THERMODYNAMICS, SECOND LAW OF The decree that entropy, or microscopic disorder of a body, cannot ever decrease. This is equivalent to saying that heat can never flow from a cold to a hot body.
TIME DILATION The slowing down of time for an observer moving close to the speed of light or experiencing strong gravity.
TIME LOOP See Closed Time-Like Curve.
TIME MACHINE See Closed Time-Like Curve.
TIME TRAVEL Travel into the past or future—in the case of the future, at a rate of more than 1 year per year.
TIME TRAVEL PARADOX Nonsensical situation that time travel appears to permit. The most famous is the grandfather paradox in which someone goes back in time and shoots their grandfather before he conceives their mother. How then could they have been born to go back in time and commit the act?
TOTAL ECLIPSE OF THE SUN The coverage of the Sun by the disc of the Moon when the Moon moves between the Sun and Earth.
TWIN PARADOX The paradox that