Light travels about 300,000 km each second. The Sun is about 150,000,000 km from Earth. About how long does sunlight take to reach Earth?

Light travels about 300,000 km each second. The Moon is about 384,000 km from Earth. About how long does moonlight take to reach Earth?

Light travels about 300,000 km each second. About how far does light travel in one minute?

Light travels about 300,000 km each second. At its closest, Mars is about 78,000,000 km from Earth. About how long does a radio signal, traveling at light speed, take to reach Mars?

Light travels about 300,000 km each second. A probe near Saturn is about 1,400,000,000 km from Earth. About how long does its radio signal take to reach Earth?

One light-year is about 9,500,000,000,000 km. Proxima Centauri is 4.2 light-years from Earth. About how far is that in kilometers?

A radio signal from a distant space probe takes 22 hours to reach Earth. Light and radio travel about 300,000 km each second. About how far away is the probe?

Light travels about 300,000 km each second. At one point in its orbit Jupiter is about 630,000,000 km from Earth. About how long does light take to travel from Jupiter to Earth?

Light travels about 300,000 km each second, and a year contains about 31,500,000 seconds. About how far is one light-year?

Light travels about 300,000 km each second. Neptune orbits about 4,500,000,000 km from the Sun. About how long does sunlight take to reach Neptune?

Four objects: the Moon, the Sun, Proxima Centauri and the Andromeda Galaxy. Which list puts them in order from nearest to Earth to furthest from Earth?

Use the table of distances from Earth. Light from which listed object has been traveling for the longest time before reaching us?

Which of these lies inside our solar system: Neptune, Proxima Centauri, the Orion Nebula, or the Andromeda Galaxy?

Not counting the Sun, which of these stars is nearest to Earth?

The Milky Way is about 100,000 light-years across, and the Andromeda Galaxy lies about 2,500,000 light-years away. Roughly how does that distance compare with the width of our galaxy?

Sirius is 8.6 light-years from Earth and Betelgeuse is about 640 light-years away. About how many times further from Earth is Betelgeuse than Sirius?

Earth orbits 1 AU from the Sun, Neptune about 30 AU, and Proxima Centauri lies about 268,000 AU away. About how many times further from the Sun is Proxima Centauri than Neptune?

Jupiter, Pluto, Proxima Centauri and the Andromeda Galaxy. Which list runs from nearest to Earth to furthest from Earth?

The Sun is the nearest star to Earth.

Sunlight reaches Earth in minutes, light from Proxima Centauri takes years, and light from the center of the Milky Way takes tens of thousands of years. What do these travel times show?

The galaxy M81 lies 12 million light-years from Earth. A telescope records an image of M81 tonight. What does that image show?

If the Sun stopped shining, people on Earth would see the sky go dark at that very instant.

A star lies 500 light-years from Earth. It exploded 200 years ago. What do observers on Earth see when they look at that star tonight?

Proxima Centauri is 4.2 light-years away. A radio message from Earth travels at the speed of light and is answered the moment it arrives. About how long until Earth receives the reply?

Astronomers record a supernova tonight in a galaxy 30,000,000 light-years from Earth. When did that explosion actually happen?

One astronomical unit is a greater distance than one light-year.

Star A is 10 light-years from Earth and Star B is 1,000 light-years from Earth. Both are visible tonight. Whose light left its star earlier?

A star 4.2 light-years from Earth suddenly stops shining today. For about how long will people on Earth keep seeing it in the sky?

Telescope images of the most distant galaxies show galaxies at an early stage of their development. Which reasoning explains that observation?

Mission controllers cannot hold a normal back-and-forth conversation with a rover on Mars. Which explanation fits the distance involved?

Distances inside the solar system are given in astronomical units, where 1 AU is the Earth-Sun distance. The nearest star beyond the Sun is about 268,000 AU, or 4.2 light-years. Why switch to light-years?

A teacher wants to state the distance from Earth to the Moon in a convenient unit. Which unit should the teacher use?

The Andromeda Galaxy is roughly 24,000,000,000,000,000,000 km from Earth. Why do astronomers state this distance as 2.5 million light-years instead?

In a scale model, 1 AU stands for 1 meter. Proxima Centauri lies about 268,000 AU from the Sun. How far from the model Sun would Proxima Centauri be placed?

In a scale model the Sun is a basketball 24 cm across, so Earth becomes a bead about 2 mm across. At the same scale, how far from the basketball should the bead be placed?

A light-year measures an amount of time rather than a distance.

Astronomers usually give the distances between planets in astronomical units rather than in light-years.

A textbook diagram shows the eight planets spaced evenly across one page. Which criticism of that diagram is correct?

An astronomer describes the distance between two galaxies in a distant cluster. Which unit suits that distance best: kilometers, astronomical units, light-seconds, or millions of light-years?

Distances in the solar system are sometimes given in light-minutes. What does it mean to say an object is 12 light-minutes from Earth?