Q 01/05

Stars are almost pure balls of which state of matter, which makes up over 99% of the visible universe?

A) Gas

B) Liquid

C) Plasma

D) Solid

Answer · why

C) Plasma

Plasma forms when atoms are stripped of their electrons, which is why it conducts electricity and glows in neon signs and lightning bolts.

Q 02/05

When Apollo 15's David Scott dropped a hammer and a falcon feather side by side on the Moon, what happened?

A) The hammer landed first

B) They landed together

C) The feather landed first

D) The feather never landed

Answer · why

B) They landed together

They landed together because the Moon has almost no atmosphere, so no drag slowed the feather, exactly as Galileo had predicted centuries earlier.

Q 03/05

Lakes freeze from the top down because liquid water is at its densest at roughly what temperature?

A) 0 °C

B) 4 °C

C) 10 °C

D) 25 °C

Answer · why

B) 4 °C

4 °C is where water is heaviest, so the colder water near freezing floats on top and ice forms there first, leaving fish alive underneath all winter.

Q 04/05

An 80 kg astronaut keeps the same mass on the Moon, but their weight there drops to roughly what fraction of Earth's?

A) One twentieth

B) One sixth

C) One third

D) Two thirds

Answer · why

B) One sixth

One sixth is the figure because gravity on the Moon is only about 1.6 m/s², which is why astronauts in moonwalk footage seem to bounce across the surf...

Q 05/05

Ice is only slightly less dense than seawater, so roughly how much of a floating iceberg sits below the waterline?

A) About 50%

B) About 75%

C) About 90%

D) About 99%

Answer · why

C) About 90%

About 90% of an iceberg is hidden underwater, which is why 'tip of the iceberg' came to mean the small visible part of a much bigger problem.