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Space Scale
Earth & Moon
Solar System
Stars & Galaxies

Phenomena & Effects

100

What is the name of the galaxy that contains our solar system?

  • 100: The Milky Way.


100

Which object orbits Earth?

  • 100: The Moon.


100

Name one property common to the outer (gas giant) planets.

  • 100: Rings; many moons; mostly gaseous composition.


100

What is the main element that makes up most stars?

  • 100: Hydrogen.


100

What causes ocean tides on Earth?

  • 100: Gravitational pull of the Moon and Sun on Earth’s oceans (and Earth’s rotation).


200

What term describes a very large group of stars, gas, and dust bound together by gravity (for example, the Milky Way)?

  • 200: Galaxy.


200

Which lunar phase must occur for a solar eclipse to be possible?

  • 200: New moon.


200

Which planet is most similar to Earth in size and makeup?

  • 200: Venus.


200

If a star appears red, is it generally hotter or cooler than a white or blue star? Explain briefly.


  • 200: Cooler — red stars are cooler than white/blue stars.


200

What are spring tides and when do they occur relative to the Moon’s phase?

  • 200: Spring tides: higher high tides and lower low tides; occur at new and full moons when Sun, Moon, Earth align.


300

Put the following in order from smallest to largest: star, cluster, galaxy, supercluster.

  • 300: star, cluster, galaxy, supercluster.


300

Explain why the same side of the Moon generally faces Earth.

  • 300: The Moon is tidally locked to Earth — its rotation period equals its orbital period, so the same hemisphere faces Earth.


300

List the inner planets in order from closest to farthest from the Sun

  • 300: Mercury, Venus, Earth, Mars.


300

Name the shape classification of the galaxy that includes the Sun and Earth.

  • 300: Spiral galaxy.


300

Why do stars appear to twinkle when viewed from Earth's surface but not from space?

  • 300: Twinkling (scintillation) is caused by Earth's atmosphere refracting starlight; in space there is no atmosphere so no twinkle.


400

Define an astronomical unit (AU) and state approximately how many kilometers are in 1 AU.

  • 400: 1 AU ≈ average Earth–Sun distance ≈ 150 million km (1.5 × 10^8 km).


400

Describe two major effects Earth would experience if Earth had no Moon.

  • 400: (Examples) Smaller tides with no monthly spring/neap pattern; Earth’s axial stability reduced leading to larger climate/season swings; possible changes in day length and effects on life/evolution.


400

Contrast comets and asteroids in terms of composition and typical orbit shape.

  • 400: Comets: icy, develop tails near Sun, often elongated orbits; asteroids: rocky/metallic, usually more circular orbits in asteroid belt.


400

What is Polaris commonly used for, and approximately how long does its light take to reach Earth if it is 430 ly away?

  • 400: Used for navigation (north); light travel time ≈ 430 years.


400

Explain how Earth's axial tilt causes the seasons. Include which hemisphere leans toward the Sun during June.

  • 400: Earth's axis tilts ~23.5°. In June the Northern Hemisphere tilts toward the Sun, receiving more direct sunlight and longer days (summer).


500

The Hubble Space Telescope photographed a galaxy 1.23 × 10^20 km away. Approximately how many light-years is that distance? (Use 1 ly ≈ 9.46 × 10^12 km; show your math.)

  • 500: Distance / (9.46 × 10^12 km/ly) = (1.23 × 10^20) / (9.46 × 10^12) ≈ 1.30 × 10^7 ly (show dimensional analysis).


500

Explain why ancient observers used lunar eclipses as evidence that Earth is round.

  • 500: During lunar eclipses Earth casts a round shadow on the Moon; only a spherical Earth always casts a round shadow from different eclipse positions.


500

Explain why gravity is the dominant force that organizes motion of planets, moons, and other objects in the solar system. Use an example.

  • 500: Gravity pulls mass together and governs orbital motion; e.g., planets orbit the Sun because Sun’s mass creates a gravitational force that keeps them in elliptical orbits.


500

A star’s apparent color helps estimate its surface temperature. Rank these colors from coolest to hottest: red, yellow, blue, white. Explain your reasoning.

  • 500: coolest → hottest: red, yellow, white, blue. Color indicates surface temperature; blue hottest.


500

A coastal town records unusually high high tides during a storm. Explain how weather can affect tide heights even though tides are caused by the Moon and Sun.

  • 500: Storm winds, low pressure, and storm surge can raise local sea level and amplify tide heights; atmospheric pressure changes and wave action modify observed tides.