13. The Sun's effect on Earth's tides is approximately (twice / half / the same as) that of the Moon.

The tides are (more / less) extreme when the Moon is new or full because the gravitational effects of the Sun and Moon (reinforce / are perpendicular to) each other. In contrast, the tides are (more / less) extreme at the quarter phases of the Moon because the gravitational effects of the Sun and Moon (reinforce / are perpendicular to) each other.

If the Moon were farther away from the Earth than it actually is, the tides would be (the same as / stronger than / weaker than) they are now.

The Sun's effect on Earth's tides is approximately half that of the Moon.

The tides are more extreme when the moon is new or full because the gravitational effects of the sun and the moon reinforce each other. In contrast, the tides are less extreme at the quarter phases of the Moon because the gravitational effects of the sun and the moon are perpendicular to each other.

If the moon were farther away from the Earth than it actually is, tides would be weaker than they are now.

Explanation:

The relation between gravitational force and distance is inverse with respect to each other.

Hence, if the distance between the moon and the Earth increases, the gravitational pull of the moon on the earth and thus the tides would decrease.