Year 7 Science · Unit 3 · Lesson 16
Challenge Worksheet
Learning Goals
What if…?
Scenario
Imagine that scientists discover a new type of sound wave — call it a "spaciton" — that can travel through a vacuum. In this hypothetical universe, sound does not need a medium to travel: spacitons can vibrate through empty space just as easily as they travel through air. The Sun is approximately 150 million kilometres from Earth. Sound travels at 340 m/s in air.
Using what you know about sound from this lesson, predict and explain what would be different about space exploration and daily life on Earth if sound could travel through a vacuum. Use scientific terms in your answer.
Extension calculation
Use the information in the scenario to help you.
(a) If spacitons could travel at 340 m/s (same speed as sound in air), how many years would it take for the Sun's sound to reach Earth? (1 year ≈ 31,536,000 seconds.) Show your working.
(b) The Sun is enormously loud — nuclear fusion releases huge amounts of energy. What property of sound determines loudness? If you could hear the Sun, predict whether it would be safe for human ears. Justify your prediction using lesson ideas.
1. A film shows an explosion in outer space accompanied by a huge boom of sound. A student says: "That's wrong — explosions in space are completely silent." Explain why the student is correct using the concept of a medium and longitudinal waves.
2. Scientists studying earthquakes in Australia use seismographs to detect infrasound waves travelling through Earth's crust. Explain (i) why infrasound cannot be heard by humans, and (ii) why the solid rock of the crust allows these waves to travel very fast over long distances.
Wrap Up
In one sentence, what was the main idea of this lesson?