Question 5: the correct answer is True. Got it right? Score 1 point.
Question 6 of 10
A swallowed chewing gum stays in the stomach for years.
Why, in question 5: does the Moon always show the same side to the Earth?
It's true. The Moon rotates around its own axis in the same time it takes to orbit the Earth, about 27 days. That's why someone on Earth always sees the same face.
The side we don't see
This happens because of tides. Over billions of years, Earth's gravity slowed the Moon's rotation until the two cycles matched, in an effect called tidal locking.
The Moon's far side is not dark: it receives sunlight just as much as the visible side, it just doesn't face us. The first photo of it was taken in 1959 by the Soviet probe Luna 3.
In 2019, the Chinese probe Chang'e 4 made the first landing on the Moon's far side. Because the Moon itself blocks the signal, communication with Earth had to go through a relay satellite.
In practice, over time we can see a little more than half of the Moon, about 59% of its surface, because of small apparent oscillations called librations.
