Astronomy Test 1 Practice Flashcards

Flashcards created to review fundamental astronomy facts, famous astronomers, Earth specifications, eclipses, moon phases, and unit conversions for Test #1.

Who invented trigonometry?

Hipparchus

Who was the first to predict a solar eclipse?

Thales of Miletus

Who calculated the circumference of the Earth?

Eratosthenes

Who discovered that Earth rotates on its axis?

Heraclitus of Pontus

What did Hypatia discover?

Conic sections

What did Copernicus contribute to astronomy?

The heliocentric model (sun-centered)

Who proposed the geocentric model?

Ptolemy

Who proposed the heliocentric model?

Aristarchus

What did Galileo contribute to astronomy?

Discovered Jupiter's moons

What is the radius of the Earth in miles and kilometers?

$\sim 3,959\,miles$ ($\sim 6,371\,km$)

What is the mass of the Earth in kilograms?

$$\sim 5.97 \times 10^{24}\,kg$$

What is the gravitational acceleration (gravity) of Earth?

$$9.8\,m/s^2$$

How many days are in a year?

$$365.25636\,days$$

How many hours are in a solar day versus a sidereal day?

A solar day is $24\,hours$. A sidereal day is $23\,hours, 56\,minutes, 4\,seconds$.

Why is the Earth not perfectly round?

Topography/mountains, centrifugal forces from spinning, a bulge from water being rotated, and tidal forces.

What percentage of the Earth is covered in water?

$$\sim 71\%$$

What causes Aurora Borealis and Aurora Australis?

Earth's magnetic field

What causes the seasons on Earth?

Earth's $23.5^\circ$ axis tilt as it rotates around the Sun

To what degree is the Earth tilted on its axis?

$$23.5^\circ$$

When do the solstices and equinoxes occur on Earth?

Winter solstice: $\sim\text{December } 21$; Summer solstice: $\sim\text{June } 21$; Vernal equinox: $\sim\text{March } 20$; Autumn equinox: $\sim\text{September } 22/23$

What is the most abundant gas on Earth?

Nitrogen

What are the two main elements in Earth's core?

Iron and Nickel

What causes Earth's magnetic field?

Convection of liquid iron and nickel in Earth's outer core (the geodynamo effect)

What is the key difference between a solar day and a sidereal day?

A solar day measures rotation relative to the Sun ($24\,hours$), whereas a sidereal day measures rotation relative to distant background stars ($23\,hours, 56\,minutes, 4\,seconds$).

What is Earth's natural satellite?

The Moon

What is the order of all the planets in the solar system starting from the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

What is the hottest planet in the solar system and why?

Venus, due to a runaway greenhouse effect.

What is the alignment order of the Sun, Earth, and Moon during a solar eclipse?

Sun - Moon - Earth

What is the alignment order of the Sun, Earth, and Moon during a lunar eclipse?

Sun - Earth - Moon

What are 4 facts about Venus provided in the notes?

1. Hottest planet. 2. Rotates clockwise so the sun rises in the west and sets in the east. 3. Its day is longer than its year. 4. Covered in sulfuric acid.

How long does it take for light to travel from the Sun to the Earth?

$\sim 8\,\text{minutes and } 20\,\text{seconds}$ ($1\,\text{AU}$, $150,000,000\,km$, or $93,000,000\,m$)

What are the historical origins of the Roman calendar and the word 'month'?

The Roman calendar originally began in March (Month 1), making July (Julius) and August (Augustus) months 5 and 6. The word 'month' comes from the Moon's cycle ($\sim 28.5\,days$).

What are the 8 moon phases in chronological order?

New Moon -> Waxing Crescent -> First Quarter -> Waxing Gibbous -> Full Moon -> Waning Gibbous -> Third Quarter -> Waning Crescent

How long is a lunar cycle?

$$\sim 29.5\,days$$

What is the Giant Impact Hypothesis for the origin of the Moon?

A Mars-sized body named Theia collided with early Earth, and the resulting debris coalesced to form the Moon.

What is the conversion factor between Astronomical Units (AU) and miles?

$$1\,\text{AU} = 93,000,000\,\text{miles}$$

What is the formula for calculating the circumference of a celestial body from its radius?

$$\text{Circumference} = 2 \times 3.14 \times \text{radius}$$

Based on a radius of $3,959\,miles$, what is the calculated circumference of Earth?

$$24,862.52\,miles$$