Astronomy

Tides

The rise and fall of sea levels caused by the gravitational forces exerted by the moon and the sun.

Spring Tides

Tides that occur during full and new moons, characterized by higher high tides and lower low tides.

Neap Tides

Tides that occur during the first and third quarters of the moon, characterized by lower high tides and higher low tides.

New Moon

The phase when the moon is between Earth and the sun, not visible from Earth.

Waxing Crescent

The phase when a sliver of light begins to appear on the moon.

First Quarter

The phase when half of the moon is lit.

Waxing Gibbous

The phase when more than half of the moon is lit, approaching full moon.

Full Moon

The phase when the entire face of the moon is illuminated.

Waning Gibbous

The phase after the full moon, when the moon starts to decrease in light.

Last Quarter

The phase when half of the moon is lit again.

Waning Crescent

The phase with a decreasing sliver of light before returning to a new moon.

Galaxy

A system of stars, stellar remnants, interstellar gas, dust, and dark matter.

Black Hole

A region in space where the gravitational pull is so strong that nothing, not even light, can escape from it.

Light Year

The distance light travels in one year, about 5.88 trillion miles.

Expansion of the Universe

The observation that galaxies are moving away from us, indicating that the universe is expanding.

The Big Bang Theory

A theory explaining the formation of the universe from a singularity approximately 13.8 billion years ago.