Mind-Blowing Science Facts: questions and answers
Study every question with its correct answer and explanation.
1. Which planet takes longer to spin once on its axis than to travel once around the Sun?
- A. Mercury
- B. Mars
- C. Venus
- D. Jupiter
Answer: Venus
Venus takes about 243 Earth days to rotate once but only about 225 days to orbit the Sun. It also spins backwards compared with most planets!
2. Why does ice float on water?
- A. It has air trapped inside it
- B. It is less dense than liquid water
- C. Cold things always rise
- D. Water pushes frozen objects upward
Answer: It is less dense than liquid water
When water freezes, its molecules lock into an open crystal pattern, making ice about 9% less dense than liquid water. Lucky for fish — lakes freeze from the top down, leaving liquid water underneath!
3. A single teaspoon of which material would weigh around a billion tonnes on Earth?
- A. Gold
- B. Lead
- C. The Earth's iron core
- D. A neutron star
Answer: A neutron star
Neutron stars are the collapsed cores of giant stars, squeezing more mass than the Sun into a ball only about 20 km across. That makes their matter unimaginably dense!
4. Which fruit is so well known for its tiny natural radioactivity that scientists jokingly use it as a unit of radiation dose?
- A. Banana
- B. Apple
- C. Mango
- D. Orange
Answer: Banana
Bananas are rich in potassium, and a tiny fraction of all natural potassium is radioactive potassium-40 — hence the informal 'banana equivalent dose'. The amount is far too small to harm you.
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5. A lightning bolt can heat the air around it to about 30,000 °C. How does that compare with the surface of the Sun?
- A. About the same
- B. About five times hotter
- C. About half as hot
- D. About 100 times hotter
Answer: About five times hotter
The Sun's surface is roughly 5,500 °C, so lightning briefly gets around five times hotter. This sudden heating makes the air expand explosively — the boom we hear as thunder!
6. The Moon is slowly drifting away from Earth. Roughly how fast?
- A. About 3.8 cm per year
- B. About 3.8 m per year
- C. About 3.8 km per year
- D. It isn't moving away at all
Answer: About 3.8 cm per year
Scientists measure this by bouncing lasers off mirrors left on the Moon by Apollo astronauts. 3.8 cm a year is about as fast as your fingernails grow!
7. Olympus Mons, the tallest known volcano in the Solar System, is found where?
- A. On Venus
- B. On Earth
- C. On Jupiter's moon Io
- D. On Mars
Answer: On Mars
Olympus Mons on Mars rises about 22 km — roughly two and a half times the height of Mount Everest! Its base is around 600 km across.
8. Which animal can regrow lost legs — and even repair parts of its heart and brain?
- A. Frog
- B. Crocodile
- C. Axolotl
- D. Tortoise
Answer: Axolotl
The axolotl, a salamander from lakes near Mexico City, can regenerate whole limbs, its tail and parts of vital organs. Scientists study it closely to learn how such healing might one day work in humans.
9. Apart from primates like us, which animal has fingerprints so similar to human ones that they are hard to tell apart, even under a microscope?
- A. Kangaroo
- B. Koala
- C. Giant panda
- D. Dog
Answer: Koala
Koalas evolved fingerprints separately from humans, probably to help them grip branches and handle eucalyptus leaves. It's a great example of nature arriving at the same solution twice!
10. Which taste can cats NOT detect?
- A. Salty
- B. Sour
- C. Bitter
- D. Sweet
Answer: Sweet
Cats lack a working version of one of the genes needed for the sweet-taste receptor. As strict meat-eaters, they never needed to find sugary food anyway!