Earth under the Astronomical Microscope

The oceans cover _____ of Earth's surface.

No other planet's atmosphere contains more oxygen than Earth's, which has a ___ oxygen content.

These emerge when electron fluxes from the magnetosphere of the Earth fall on the atmosphere below, causing oxygen and other atoms to shine.

The simplest aurora. It looks like thin clouds are reflecting moonlight or city lights.

Shaped like a rainbow but with no sunlight to make one. A steady or pulsating green arc is the most common type of arc, but sometimes dim red arcs appear.

Also called drapery. This spectacular aurora resembles a billowing curtain at a theater, but nature is the star of the show.

One or more long, thin bright lines in the sky, appearing like faint beams from the heavens.

High overhead, a crown in the sky, with rays emanating in every direction.

Our planet's rocky terrain.

The water in the oceans, lakes, and elsewhere on Earth.

The frozen regions — Antarctica and Greenland’s ice caps.

The air from ground level up to hundreds of miles.

All living things on Earth.

Plays a vital role in protecting Earth from many of the dangerous emanations from the Sun.

Regions where electrically charged particles — bounce back and forth above Earth, trapped in its magnetic field.

Moving streams of molten iron in the outer core generate a magnetic field that reaches out through the whole planet and far into space.

High-speed, high-energy particles that come from explosions on the Sun and from distant points in space.

• Makes the needle of a compass point toward north (or south).

• Provides an invisible guidance system for homing pigeons, some migratory birds, turtles, salmon, various ants and bees (among other bugs), and even some ocean-dwelling bacteria.

• Forms the magnetosphere far above Earth.

The length of the day, 24 hours, is the average time it takes for the Sun to rise and set and rise again.

A year consists of approximately ___, the time that it takes Earth to make one complete orbit around the Sun.

Earth turns once in 23 hours, 56 minutes, and 4 seconds concerning the stars.

Measures sidereal time by registering 24 sidereal hours during an interval of 23 hours, 56 minutes, and 4 seconds of mean solar time.

Also known as Greenwich Mean Time (GMT); Common standard time, and simply the standard time at Greenwich, England.

The official international time standard.

The line through the North and South poles; it isn’t perpendicular to the plane of Earth’s orbit around the Sun.

The north star; the star Alpha Ursae Minoris, located in the Little Dipper asterism of the Little Bear constellation, Ursa Minor.

On the first day of spring, the Sun crosses from “below” (south) the equator to “above” (north).

The Sun reaches the farthest point north on the ecliptic.

The Sun crosses the equator going back down south, and fall begins.

The Sun gets as far south as possible on the ecliptic.

It turns into another isotope of the same element, or into a different element, at a rate determined by the half-life of the radioactive substance. If the half-life is 1 million years.

The original radioactive isotope atoms.

An approach to date minerals and rocks that makes use of radioactive isotopes.

The eruption of molten rock from within Earth, including the formation of new volcanoes.

These are considered debris from asteroids, and asteroids are thought to be debris from the very early solar system, when the planets first formed.