When comparing the size of the Earth to the size of other planets, the Earth size may appear to change. The Earth can appear to be LARGER, SMALLER or the SAME as the planet to which it is being compared . The size of the Earth is "relative" to which planet we compare it with.
"The solar system is so vast that it's difficult to visualize how big some of the planets are. For example, Jupiter is so much bigger than Earth that Earth would fit inside its Great Red Spot. Earth's moon is unusual because it's a respectable fraction of the size of its primary; it's gigantic compared to Mars's moons, Phobos and Deimos, which look like specks next to it, and it's about as big as Io, one of the largest moons of Jupiter." - Bob Kanefsky, NASA Scientist