Q 01/05

How long would a drop through a frictionless tunnel bored right through Earth take to reach the far side?

A) About 9 minutes

B) About 42 minutes

C) About 90 minutes

D) About 24 hours

Answer · why

B) About 42 minutes

About 42 minutes is the textbook answer for a uniform-density Earth, the same as half the orbital period of a low satellite. A realistic density profi...

Q 02/05

Gravity on the Moon, where Apollo astronauts bounded along in their suits, is roughly what fraction of Earth's?

A) About one-sixth

B) About one-third

C) About one-tenth

D) About one-half

Answer · why

A) About one-sixth

About one-sixth is right: lunar gravity is 1.62 m/s², 16.6% of Earth's, so 80 kg of suit and backpack felt like 13 kg. It still varies by 1.6% across ...

Q 03/05

Crew on the International Space Station, where gravity is still 90% of surface strength, float because they are in what?

A) Escape velocity

B) Orbital hover

C) Terminal velocity

D) Free fall

Answer · why

D) Free fall

Free fall is the whole trick: station and crew are falling toward Earth together, but moving sideways at 28,000 km/h so they keep missing it. Calling ...

Q 04/05

On most coastlines, how many high tides does the Moon's pull raise in the course of a single day?

A) One

B) Two

C) Three

D) Four

Answer · why

B) Two

Two high tides a day is the norm because the Moon raises one bulge on the side facing it and another on the far side, and Earth turns through both. A ...

Q 05/05

Which Canadian bay, a funnel-shaped basin that resonates with the tide, has the highest tidal range on Earth?

A) Hudson Bay

B) Frobisher Bay

C) Baffin Bay

D) Bay of Fundy

Answer · why

D) Bay of Fundy

Bay of Fundy tides average about 16 metres, against a worldwide average of roughly one metre, enough to push rivers that drain into it backwards twice...