INTRO TO SPACE: The Expanding Universe and the Galaxies

Vocabulary terms and definitions covering the expansion of the universe, key astronomers, and astronomical units of measurement based on the lecture notes.

Edwin Hubble (1889-1953)

Leading astronomer in the early twentieth century for whom the Hubble Space Telescope is named; he deduced that apparent star clusters were actually distant galaxies.

Father Georges La Maitre

The Catholic priest who published a theory in $1927$ proposing that all matter and energy in the universe originated from a single point.

$13.7$ billions of years ago

The estimated time when the universe formed and began its expansion.

Red-shifted light

Evidence suggesting the Universe is expanding, characterized by light from galaxies moving away from us.

Cosmic background radiation

The heat remaining from the rapid expansion of the universe that can be seen everywhere today.

Astronomical unit (AU)

The distance from the Sun to Earth, which is approximately $150,000,000\,\text{km}$.

Light-year (ly)

The distance that light travels in $1\,\text{year}$, approximately equivalent to $63,000\,\text{AU}$ or $9,000,000,000,000\,\text{km}$.

Proxima Centauri

The nearest star to Earth, part of the Alpha Centauri system, located $4.3\,\text{ly}$ away.

$$0.39\,\text{AU}$$

The distance from Mercury to the Sun.

$$1.3\,\text{light seconds}$$

The distance from the Earth to the Moon.

$$2.5\,\text{million light years}$$

The distance from Earth to the Andromeda Galaxy.