Astronomy and Physics: Key Concepts in Celestial Mechanics and Light Interactions

Constellation

A region of the sky within official borders set in 1928

Zenith

The top point, the point directly above you

Horizon

All points 90 degrees from the zenith

Meridian

An imaginary line passing from North to South through the Zenith

Elevation or Altitude

The angle above the horizon

Azimuth

The angle measured around the horizon, starting from the North direction

Phases of the Moon

The appearance of the Moon determined by the combination of its bright and dark faces that we see as it orbits Earth

Heliocentric Model

A proposed model where planets, like Venus, orbit the Sun and not the Earth

Parallax

The apparent shift in a star's position due to the observer's movement

Kepler's Second Law

As a planet moves in its orbit, it sweeps out equal areas in equal times

Kepler's Third Law

More distant planets orbit the sun at slower average speeds

Mass

The amount of matter in an object (units of kg)

Weight

The force that acts upon an object (units of Newtons, or kg m/s^2)

Energy

The capacity to do work or cause change

Photons

"Pieces" of light (radiant energy), each with a precise wavelength, frequency, and energy

Planck's Constant (h)

The constant used in the photon energy equation (6.626 x 10^-34 J x s)

Atomic Number

The number of protons in the nucleus

Atomic Mass Number

The number of protons + neutrons in the nucleus

Isotopes

Atoms that have the same atomic number but different atomic mass numbers

Emission

A light and matter interaction where photons are produced

Absorption

A light and matter interaction where photons are consumed

Transmission

A light and matter interaction where photons pass through freely

Reflection or Scattering

A light and matter interaction where photons are redirected

Quantized Electron Energy

The concept that electron energy in atoms exists at distinct, specific energy levels