Grade 6 Science Practice Test: Solar System, Moon Phases and Eclipses

The Sun always lights half of the Moon; its position in its orbit decides how much of that half faces us. Earth's shadow only falls on the Moon during a lunar eclipse.

One full cycle, for example from new moon to the next new moon, takes about 29.5 days. A week is only about a quarter of the cycle.

In a solar eclipse the Moon blocks the Sun's light from reaching part of Earth. When Earth is in the middle, its shadow falls on the Moon, which is a lunar eclipse.

A lunar eclipse needs Earth between the Sun and the Moon, which is where the Moon is at full moon. Solar eclipses happen at new moon.

The order outward from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Venus is the hottest planet, but it is second from the Sun.

The four inner planets are small and rocky. Jupiter, Saturn, Uranus and Neptune are the large outer planets made mostly of gases and ices.

The Sun's gravity pulls on each planet, bending its path into an orbit. There is no air in space, and magnetism does not hold planets in orbit.

Because Earth's axis is tilted, each hemisphere gets more direct sunlight for part of the year. Distance is not the cause: Earth is actually closest to the Sun in early January, during the Northern Hemisphere's winter.

Because one spin and one orbit take the same time, the same face keeps pointing toward Earth. The far side does get sunlight; it is lit during our new moon.

12,700 / 3,500 is about 3.6, which rounds to about 4. Picturing the Moon as much smaller than that is a common mistake caused by drawings that are not to scale.