Chapter 3: Earth in Space Overview

Big Bang Theory

Theory that the universe began when all matter and energy erupted from an extremely dense singular mass

Universe

Approximately 20 million light years across and expanding

Galaxy

The largest definable unit in the universe

Milky Way

Galaxy estimated to have 400 billion stars, including our sun

Orbit

The path followed by a celestial body in its revolution around another body

Perihelion

Point in Earth's orbit where it is closest to the sun

Aphelion

Point in Earth's orbit where it is farthest from the sun

Beam Spreading

Phenomenon where insolation from lower angles must spread across more surface

Atmospheric Attenuation

Phenomenon where insolation from low angles passes through more atmosphere

Sphere

A three-dimensional curved surface

Equator

Region where the sun angle is high, resulting in high energy

Mid-latitudes

Regions with sun angles that are just right

Poles

Regions with low sun angles leading to more attenuation and less energy