1. Calcium
   Hydrogen
2. Helium
   Gold

Hydrogen has the atomic number 1, and its symbol is simply "H." It's earned its place at the top of the heap: Hydrogen is the most abundant element in the universe, and an essential part of both water, the stars and carbohydrates.

1. The earth
   The moon
2. Mars
   The sun

"Corona" comes from the Latin word for "crown," and describes the gorgeous flare-like ring around the outer edge of our sun. A total eclipse, though rare, is the best time to see the sun's corona (don't forget, you still need proper eye protection).

1. Clouds
   Flowers
2. Gemstones
   Stars

Cirrus clouds are the highest ones, as measured from their base. Because of their high altitude, they are made of ice crystals, which make lovely, spiny structures, not like the opaque formations seen inside ice cubes.

1. Biome
   Habitat
2. These are words for the same thing.

Think of a "biome" as a biological region, a large area with certain characteristics that make it nurturing to many types of flora and fauna. A "habitat" is smaller and more specific to one species; a biome will encompass many individual habitats.

1. Barium
   Gold
2. Oxygen
   Tin

This abbreviation reflects the Latin name for gold, "aureus." Fun fact: When the conservative politican Barry Goldwater ran for president, his backers made signs reading "AU-H20" to show their support.

1. Old-growth forest
   Treeline
2. Tacoma
   Taiga

Much of Russia and Canada are encompassed by this second-largest of Earth's biomes. Also included are Scandinavia and some of Japan. The taiga is marked by large evergreen forests, with many of the trees pines and spruces.

1. Core
   Crust
2. Ionosphere
   Mantle

Geologists essentially divide the earth into core, mantle and crust. The ionosphere is part of the earth's atmosphere, as the name implies. It encompasses the area between 37 and 600 miles above sea level.

1. Ocean temperatures
   The force of winds
2. Barometric pressure
   The heat of foods like peppers

This can be a little confusing, as wind speed is simply measured in knots. But the Beaufort scale is observational, rating the force of winds in relation to their effect on bodies of water, from "calm" to "hurricane force." You'll never hear the Beaufort scale used to describe winds over the land, just seas and oceans.

1. Between lobes of the brain
   Between continental plates
2. At CERN
   In the rings of Saturn

The Cassini division is a dark gap in the rings of Saturn. Astronomers have learned that there isn't a total absence of material there, but rather some ring material which doesn't reflect light all that well. Fun fact: Oleg Cassini, the designer who dressed first lady Jackie Kennedy, was a descendant of astronomer Giovanni Cassini.

1. Bears
   Cats
2. Dogs
   Rabbits

This family includes both rabbits and hares. As people who have bred rabbits know, this family is very fertile, often having several litters a year if the circumstances (mostly proximity of males and females) allow it.

1. Evaporation scale
   Half-life
2. Lead time
   Overton window

We're not talking about simple evaporation here. This term is often used in relation to radioactive elements which undergo decay, or medications, which are gradually halved in potency in the body, then break down to nothing.

1. The circumference of the earth
   The distance between the earth and the sun
2. The distance between our sun and Alpha Centauri
   The distance between the earth and the moon

This distance has been adopted by astronomers to measure distances between near-earth bodies, like other planets in the solar system. It isn't really used in measurements beyond the solar system, as it'd be much too small. Light-years are used instead.

1. The discovery of stellar parallax
   Penicillin
2. The periodic table
   A system of taxonomy

Linnaeus created the two-name, or "genus-and-species," way of identifying biological organisms. He was a Renaissance man with interests in several academic fields, but taxonomy is the one for which the world remembers him.

1. Aether
   Plasma
2. X-rays
   There are only three states of matter.

Plasma is an extremely energy-intensive state of matter, not found all that often on the earth. Lightning bolts, however, are an example. Also, the interior of the sun is mostly plasma.

1. Bird
   Lizard
2. Rock
   Star

This is one of the first things you learn in geology or earth science, the three classifications of rock. Igneous is formed from hot magma, sedimentary from compressed layers of soil or broken-down rocks, and metamorphic is made from other rocks under extreme heat or pressure. This is known as the "rock cycle," with rocks changing from one type to the other.

1. Jupiter
   Mars
2. Saturn
   Uranus

The planet Mars is named for the classical god of war; you probably knew that. So it's fitting that its moons are named "fear" and "panic" (from the Greek), things which follow in the wake of war.

1. Astronomy
   Kinematics
2. Quantum mechanics
   Time travel is not believed to be possible by any branch of science.

We know it makes for some fantastic movies and TV, but no branch of science accepts that humans will be able to move back and forth in time. Although time may exist "all at once," humans are made of matter, therefore a part of the fabric of spacetime — and thus trapped in our particular part of the tapestry.

1. Calcium
   Lead
2. Potassium
   Strontium

Potassium gets its symbol from its late-Latin name, "kalium." Potassium is essential to the human diet. While sodium moves water into cells, potassium moves it out again, so both are essential to a correct balance.

1. Animal science
   Biology
2. Chemistry
   Vivology

"Animal science" is too narrow a field to cover all life forms. Animals are just one of five kingdoms into which all life on earth is divided; kingdoms being the largest grouping in biological taxonomy.

1. The bacteria
   The cell
2. The organ
   The organism

Bacteria are unicellular, of course, but they're only a small fraction of living things on earth. But all living organisms have cells, and it's this that biologists consider to be the essential building block of life.

1. Biorhythm
   Torpor
2. Homeostasis
   Homunculus

Sound boring? Nope, this is the state that you *want* your body to be in. A viral infection, like a cold or the flu, knocks your body out of homeostasis, as the viruses and your immune system fight a kind of war. Fortunately, homeostasis is usually restored within a few days, unless the patient is very young, very old or immunosuppressed.

1. Birds
   Fish
2. Mammals
   Spiders

An ornithologist is someone who studies birds. Fun fact: Birds are the closest descendants of the few surviving dinosaurs that we have. (Also, in case you were wondering, the study of fish is "ichthyology," spiders are "arachnology," and mammals are simply "mammalogy.")

1. The imprinting of images on the retina
   The way plants grow toward a light source
2. The way plants make energy from sunlight
   The way sun exposure affects skin tone

If you chose the second option, it is true that plants grow toward a light source, and this is called "phototropism." However, a much more important process in biology is photosynthesis. It allows plants to, well, live and to nourish many animal species that feed on them.

1. True
2. False

Angiosperms are flowering plants, and you probably spent a good bit of time in school learning about how they reproduce using flowers with pistils and stamens. However, gymnosperms (often evergreen trees) use cones to spread their seeds, and ferns just have spores.

1. Blood
   Chlorophyll
2. Legs
   A spine

If you chose "chlorophyll," you might have been thinking that the "verte" part was related to "verde," meaning "green" in the Latin languages. Sorry, it was a fake-out. Invertebrates don't have spines; it's a group that includes spiders, insects and crustaceans.

1. Between "domain" and "kingdom"
   Between "family" and "genus"
2. Between "phylum" and "order"
   Between "genus" and "species"

"Class" is about midway on the taxonomic scale. In full, it goes "Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species." There are a variety of mnemonic devices you can use to memorize this; look it up online and pick the one that suits you.

1. Acid
   Alkaline
2. Animal
   Archetype

DNA is the molecules that make up genes. As such, we think of it mostly as being responsible for passing traits from parents to children. However, DNA remains important throughout a person's lifetime -- it is the blueprint for how each individual cell should function.

1. Birds
   Cats
2. Dogs
   Humans

This didn't happen by accident, of course. Dogs were bred by humans to exaggerate certain valued characteristics, and over about 7,000 years of this, became highly genetically diverse animals. If humans had the same disparity in, say, height, some of us would be two feet tall, while other ethnicities would grow to about seven feet tall.

1. True
2. False

About 90 percent of plants have vascular tissue, meaning vessels that carry water and nutrients to their outer extremities. Early plants did not have these veins, and therefore could not grow very tall -- there was no way for the plant to feed growing tissues far from its roots and stem.

1. Archaea
   Bacteria
2. Eukarya

Archaea are single-celled organisms, and a recent addition to the biological hierarchy. They thrive in places that other single-celled life forms can't, including acidic and salty environments, and in temperatures over 100 Celsius.

1. Hematite
   Lava
2. Stalactites
   Quicksand

Magma and lava are essentially the same thing. You're probably a bit more familiar with the term "lava," as it can be seen on guided tours of volcanically active sites. Or, maybe, it's just what you called the stuff that oozed out of your science-project "volcano" in junior high.

1. Diamond
   Iron
2. Silver
   Titanium

Of course, it's the beautiful diamond. However, here's a interesting fact: Diamonds weren't chosen as the symbol of engagement because they were beautiful, nor are they rare. They were chosen for their durability, as they didn't scratch despite being worn daily. Not very romantic, eh?

1. The brain and nerves
   The lungs
2. The heart
   The bones

If you know Spanish, you had a head start on this question, as "pulmon" is the Spanish word for "lung." A pulmonologist specializes in these essential organs and in disorders that affect the breathing.

1. The prehistoric earth
   The earth's poles
2. The moon
   The ocean floor

You probably didn't study much selenology in school, but that's the name for the geological study of the moon. With the moon landings and the samples the astronauts brought back, selenology made a "giant leap" forward (to use Armstrong's phrase).

1. Birds
   Horses
2. Deer
   Whales

A passerine is a perching bird, with two toes facing forward and one backward, which allows it to cling to tree branches. Most birds that are not passerines are aquatic birds, which have webbed feet that help them swim, but do not allow perching in trees.