Science

Do fish sleep during the day or at night？

Answer explanation

Sleep is the rest of the brain. Since fish have no brain, where they rest is called sleep.

When it thunders, why do you see the lightning first, then hear the thunder?

Answer explanation

300000km/s > 300m/s

Does a perm keep your hair curly forever

• Yes

• No

Answer explanation

Normal hair transplants are unlikely to become permanently crooked, because curly hair is hereditary

Why do helicopters have to have small propellers at the back？

Answer explanation

The tail rotor is designed to counteract the torque generated by the main propeller, which would otherwise spin as soon as the helicopter leaves the ground. The tail rotor is separated by the main shaft of the propeller, and its speed is proportional to the main propeller. The ratio stays the same.

The concept of gravity was discovered by which famous physicist？

How many colors are there in the rainbow？

• 5

• 6

• 7

• 8

Electrons are smaller than atoms

• True

• False

What is the tallest grass on earth?

What is the hardest natural substance on earth?

Does sound travel faster through air or water?

• Air

• Water