How We Measure Cosmic Distances

Students learn how astronomers measure distances they can never travel, climbing the cosmic distance ladder from laser and radar echoes to parallax, Cepheid variable stars and redshift.

Grades 5-8About 15 minutes of narrated flight, plus discussion stops8 stops

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What students will see and do

Students fly from Earth to the Moon, Venus, Proxima Centauri, the Cepheid star Delta Cephei, the Andromeda Galaxy, the Virgo Cluster and the edge of the observable universe. Aetherion pauses for discussion at Proxima Centauri (how parallax works), Delta Cephei (Henrietta Leavitt's patient discovery) and Andromeda (learning the Milky Way is one galaxy among many).

Learning objectives

• Explain how timing a radar or laser echo gives a distance when the speed of light is known.
• Use the thumb experiment to describe parallax and why nearby objects shift more than distant ones.
• Describe how Cepheid variable stars act as standard candles and how Henrietta Leavitt and Edwin Hubble used them.
• Identify redshift as evidence that the universe is expanding and as a way to estimate the distances of faraway galaxies.

NGSS connections

Stops on this journey

1. The Measuring Problem
2. Lasers to the Moon
3. Radar Echoes from Venus
4. The Thumb Trick (discussion stop)
5. A Star That Keeps Time (discussion stop)
6. Another Galaxy (discussion stop)
7. Galaxies Rushing Away
8. The Top of the Ladder

Vocabulary

• light-year
• radar
• parallax
• Cepheid variable
• standard candle
• redshift
• galaxy
• observable universe