General Science: 600+ Most Important Science Facts - Part 6 (Definitions)

Question 176. What are isomers?
Two (or more) isomers of the same compound have the same chemical composition, but different structures.

Question 177. What is a transformer in electronics (not the movie)?
A transformer is a device consisting of primary and secondary coils of wire, which applies Faraday’s law in order to step AC voltage up or down.

Question 178. What is flux in physics? Which types of flux can you name?
Flux could be the rate of flow of a quantity across a surface, or it could be a measure of the number of field lines passing through a surface. Types of flux include electric flux, magnetic flux, gravitational flux, energy flux, momentum flux, heat flux, mass flux, diffusion flux, particle flux, probability flux density, Poynting flux, and the list goes on. You should have named electric, magnetic, and at least 1-2 others.

Question 179. What is viscosity?
Viscosity provides a measure of internal friction in the flow of a fluid.

Question 180. What does triage refer to in health science?
In an emergency room or on a battlefield, triage refers to assigning priority to patients based on factors like severity of wounds and prospects for survival.

Question 181. What is riboflavin?
Riboflavin, also known as vitamin B2, is important for the growth and function of cells.

Question 182. What is a bolometer?
A bolometer measures the power of electromagnetic radiation. It is useful, for example, in astronomy for wavelengths from a submillimeter to the far infrared.

Question 183. What is retrograde motion?
Retrograde motion refers to a short period for which a planet appears to travel backward relative to the stars as viewed from earth compared to the direction that it normally appears to travel relative to the stars. Bonus if you can explain why.

Question 184. What is salmonella?
Salmonella infection is a bacterial disease commonly caused by contaminated food or water, which affects the intestines.

Question 185. What is simple harmonic motion?
Simple harmonic motion is sinusoidal motion experienced when the net force on an object is proportional to the negative of the displacement of the object from equilibrium (for example, when the net force equals the restoring force exerted by a spring), in which case the acceleration is also proportional to the negative of the displacement of the object from equilibrium.

Question 186. What does propagate mean (in physics, not biology)?
Propagate refers to the traveling of a wave, often with the sense of spreading outward (like a ripple in water or like a sound wave), but it could just mean to transmit through a medium (like a ray of light traveling through glass).

Question 187. What does adiabatic mean?
Adiabatic refers to a process that occurs without any heat exchange.

Question 188. What does ablation mean in geology?
In geology, ablation refers to material (ice and snow) lost by a glacier (or the amount of this lost material that is melted).

Question 189. What is propulsion? What is thrust?
Propulsion refers to the act of propelling, pushing, or driving an object forward, such as to accelerate an object (but such a system is also necessary to overcome resistive forces like air resistance just to maintain constant velocity in an atmosphere). Thrust is a driving force that generates propulsion. Thrust is created from Newton’s third law: By ejecting a fluid backwards, for example, Newton’s third law produces an equal and opposite reactionary force of thrust on a rocket.

Question 190. What is a cosmic ray?
A cosmic ray is a stream of high-energy particles (such as protons or helium nuclei) from space which interact with atoms in earth’s atmosphere.

Question 191. What is a polymer?
A polymer is a giant molecule which consists of monomers chained together.

Question 192. What do the terms coniferous and deciduous mean?
Coniferous trees produce cones and have needle-like leaves. Deciduous trees shed their leaves annually.

Question 193. What is a hadron?
A hadron is a particle composed of quarks, such as a baryon (three quarks) or a meson (quark-antiquark pair).

Question 194. What is a lepton?
A lepton is a fermion that isn’t subject to the strong nuclear force, and includes the electron, muon, tau particle, and their neutrinos.

Question 195. What is isostasy?
Isostasy is basically the concept of buoyancy applied to earth’s crust, that it is “floating” in equilibrium (with balanced pressures) on the mantle.

Question 196. What is mitosis? What are its stages?
Mitosis refers to the division of the nucleus of a eukaryotic cell. Phases include prophase, metaphase, anaphase, and telophase.

Question 197. What is a heat engine?
A heat engine is a device that adapts the natural flow of heat from a thermal reservoir at high temperature to a thermal reservoir at low temperature in order to perform mechanical work.

Question 198. What are dendrites in biology?
Dendrites extend from neurons and carry impulses.

Question 199. What is moment of inertia?
Moment of inertia provides a measure of a rigid body’s tendency to maintain constant angular momentum (which is a sense of rotational inertia).

Question 200. What are the thalamus and hypothalamus in anatomy?
The thalamus is the gray matter in the brain which receives sensory messages and relays them to parts of the cerebrum. The hypothalamus lies under the thalamus and regulates basic body functions like hunger, fatigue, and body temperature.

Question 201. What is a solenoid?
A solenoid is a coil of wire in the shape of a right-circular cylinder, which serves as a magnet when carrying current (and may or may not have an iron core).

Question 202. What is pumice?
Pumice is porous volcanic rock, which is typically light in color and less dense than water.

Question 203. What is a thermal reservoir?
A thermal reservoir is a heat source that offers (or may receive) a virtually limitless supply of thermal energy, with virtually no effect on the temperature of the heat source.

Question 204. What is hepatitis?
Hepatitis is inflammation of the liver. Bonus if you can describe A, B, and C.

Question 205. What is the Gregorian calendar? What is the Julian calendar? Which is in use today?
The Gregorian calendar (currently in use) has 365 days in most years, a 366th day on years divisible by 4 (called leap year) but not years divisible by 100 (unless they are also divisible by 400). For example, 2000 had a leap year because it was divisible by 400, but 2100 won’t have a leap year, whereas 2104, 2108, 2112, etc. will have leap years. The Julian calendar (used previously) has 365 days in most years and a 366th day on years divisible by 4 without any exceptions. The problem with the Julian calendar is that one astronomical year is slightly shorter than 365.25 days long, and the Gregorian calendar corrects for this discrepancy.

Question 206. What is a vestigial structure?
A vestigial structure is a trait inherited from an ancestor which has lost most or all of its original function, like the appendix in humans.

Question 207. What is impulse in physics?
Impulse equals the change in an object’s momentum or, equivalently, the product of the average collision force and the time duration of the collision.

Question 208. What is luminosity?
Luminosity is the total amount of energy radiated or emitted per unit time. It is equivalent to the radiant power. For a star, luminosity provides a measure of its intrinsic brightness (which we can use to determine its apparent brightness from earth).

Question 209. What is a pheromone?
A pheromone is a chemical substance secreted by an animal, which impacts the behavior of other animals in the same species.

Question 210. What is an eddy current in magnetism?
An eddy current is induced in a metal that travels through a magnetic field (by Faraday’s law), which is often undesirable from a practical perspective because this dissipates energy (in the form of heat).

Question 211. What is a polypeptide?
A polypeptide is a long chain of amino acids. Polypeptides are found in proteins.

Question 212. What is Atwood’s machine?
Atwood’s machine consists of two masses connected to a cord that passes over a pulley, which is suspended in the air. When the system is released from rest, the heavier mass falls down, pulling the lighter mass upward. Atwood’s machine is useful for measuring gravitational field (since it involves long time durations compared to dropping an object from rest).

Question 213. What do orthopedic surgeons do?
Orthopedic surgeons specialize in disorders relating to the musculoskeletal system, including bones, joints, tendons, etc.

Question 214. What is an ideal gas?
An ideal gas has sufficiently low density so as to obey the law PV = nRT. Bonus for describing an ideal gas at the molecular level, such as assuming identical molecules, negligible intermolecular forces (except for collisions), momentum and kinetic energy are conserved for collisions, motions are random, molecules obey Newton’s laws of motion, and there are very many molecules with large separations.

Question 215. What is pneumatics?
Pneumatics is the branch of engineering that studies compressed gases.

Question 216. What is entomology?
Entomology is the branch of zoology that studies insects.

Question 217. What is stoichiometry?
Stoichiometry is the branch of chemistry that studies the quantitative relationships between reactants and products in reactions.

Question 218. What do nodes and antinodes refer to on a standing wave?
On a standing wave, a node is a point that does not oscillate and an anti-node is a point where there is maximum oscillation.

Question 219. What is the opposite of a conductor?
An insulator (not inductor) is the opposite of a conductor.

Question 220. What is an inductor in a circuit?
An inductor is a coil of conducting wire (or even a single loop of wire), such that Faraday’s law applies to it.

Question 221. What is an endoplasmic reticulum?
An endoplasmic reticulum is a network of membranes in the cytoplasm of a eukaryotic cell, which is involved in the synthesis of proteins and lipids.

Question 222. What does duality mean in modern physics?
Duality means that light exhibits both wave-like and particle-like properties, and also means that a “particle” like an electron also exhibits wave-like properties (the latter is according to the de Broglie relation).

Question 223. What is libration in astronomy?
In astronomy, libration refers to the oscillation of an object around a stable point in the three-body problem. In the sun-earth-moon problem, this results in a slight wobble of the moon in its orbit around earth, allowing us to see a little more than 50% of its surface (which would be expected since the moon always shows the same side toward the earth due to tidal lock).

Question 224. What is precession in astronomy?
In astronomy, precession refers to a slight change in the position of the stars as viewed from earth due to the tilt of earth’s axis.

Question 225. What is dark matter?
Dark matter is non-luminous matter in the universe that can’t be seen through a telescope, but which is postulated to exist to explain gravitational effects that can’t be explained solely from visible matter.

Question 226. What are the metacarpals?
Metacarpals are the five bones in each hand connecting the fingers to the wrists.

Question 227. What does orthogonal mean?
In a basic sense, orthogonal means perpendicular. (Bonus if you can do better.)

Question 228. What is a neutrino?
A neutrino is a neutral particle with very little mass, which interacts only very weakly with other particles (and through the weak nuclear force).

Question 229. What do the terms ventral, dorsal, and lateral mean in medical science?
Ventral refers to the region of the body near the belly, dorsal refers to the back side, and lateral means toward the side.

Question 230. What is special about the Carnot cycle? (Bonus if you can describe the diagram.)
The Carnot cycle has the maximum possible efficiency for a heat engine that operates between a given pair of high and low temperatures.

Question 231. What is nucleosynthesis?
Nucleosynthesis refers to the formation of the heavier elements, which occurs in stars.

Question 232. What does polarization mean in physics? (Bonus if you can name four methods.)
The polarization of a beam of light occurs when the electric fields of all of the waves in the beam oscillate in a common direction. Light may be polarized by reflection (maximized for Brewster’s angle), passing through a birefringent crystal (like calcite), through scattering, or by passing through a polarizer.

Question 233. What is arrhythmia?
Arrhythmia is an irregularity in the beating of the heart.

Question 234. What is a cyclotron?
A cyclotron is a particle accelerator in the shape of a circle.

Question 235. What is an axon in biology?
In biology, an axon is a long fiber that carries an impulse away from a neuron.

Question 236. What is a nephron?
A nephron is a structure in the kidneys which collects waste (in the form of urine) and purifies blood.

Question 237. What is Ebola?
Ebola is an RNA virus which causes fever and internal bleeding, often resulting in death.

Question 238. What is the work function of a metal?
The work function of a metal is the minimum energy with which an electron is bound to its atoms.

Question 239. What is an embolism in medical science?
Embolism refers to a foreign material (like a blood clot) that obstructs a blood vessel.

Question 240. What do pair production and pair annihilation refer to in particle physics?
Pair production occurs when two photons produce an electron and positron, and pair annihilation is the opposite

Question 241. What is graphene?
Graphene is an allotrope of carbon in a hexagonal lattice just one atom thick, yet is very strong. (Andre Geim and Konstantin Novoselov received a Nobel Prize in 2010 for their research on graphene.)

Question 242. What does it mean to normalize a wave function?
In quantum mechanics, normalizing a wave function is a method to determine an unknown coefficient by demanding that there be 100% probability of finding the particle somewhere, using an integral (in 1D) of the form

Question 243. What are stem cells?
Stem cells are unspecialized cells found in adults, which replicate to produce new body tissues, becoming specialized cells in the process.

Question 244. What were the hypothetical epicycle and deferent? (Bonus if you know equant.)
The ancient Greeks devised (an incorrect) geocentric model with the earth at the center of the solar system, which used epicycles and deferents. The deferent is a large circle centered around the earth, and the epicycle is a smaller circle containing a planet (such as Mars). The epicycle rotates as it travels along the deferent. (This forms a curve known as the epicycloid in geometry.) The Greeks improved on this idea by placing the earth not at the exact center of the deferent, but by placing the earth a little off-center, equally distant from a symmetric point called the equant. The epicycle revolved around the equant with uniform angular speed.

Question 245. What was the hypothetical substance called phlogiston?
Phlogiston was a hypothetical substance thought to be involved in burning, but now we know that combustion occurs without any such substance.

Question 246. What is a Hertzsprung-Russell diagram? What is plotted on each axis?
A Hertzsprung-Russell diagram plots luminosity (or, equivalently, absolute magnitude) on the vertical axis and spectral type (or, equivalently, color, wavelength, or temperature) on the horizontal axis for stars. Most of the stars in the night sky appear on a diagonal known as the main sequence. The H-R diagram illustrates the life cycle of a star and can be used to determine the distance from earth to a galaxy.

Question 247. What is meningitis?
Meningitis refers to inflammation of the membranes (known as the meninges) that enclose the central nervous system, usually caused by infection.

Question 248. What is a synapse?
A synapse is the junction between a neuron and an adjacent cell, allowing an impulse to be transferred.

Question 249. What is magnetic hysteresis?
Magnetic hysteresis refers to a lag in the magnetization of a ferromagnetic material when the magnetizing force varies, such that if the magnetizing force increases and then decreases to its original value, a plot of the magnetization as a function of the magnetizing force includes a loop (rather than simply retracing the curve).

Question 250. What is the function of the gall bladder?
The gall bladder stores bile until food enters the small intestine.

Question 251. What was the hypothetical ether in older theories of physics?
The ether was a hypothetical substance once believed to fill space, thought to serve as a medium for the transmission of light waves. The Michelson-Morley experiment failed to support the ether theory.