The moon's orbit is an ellipse not a circle, so it does get closer and further from the earth. However, that change in the apparent size of the moon is negligible compared to the way the human eye focuses.
For a variety of reasons having to do with how the human eye and brain work together, the human brain interprets a full moon lying near the horizon to appear larger than when it lies high in the sky, away from the horizon. The illusion can be demonstrated with the picture below - both "moons" are in fact the same size.
To check the real size of the moon when it appears "huge", use this trick: get a 5 pence coin and hold it between your thumb and forefinger at arms length. Move it along so it covers the moon. You will see that the "large" moon close to the horizon actually is suddenly much smaller than it appears, as the coin forces the eye to adjust.
For a variety of reasons having to do with how the human eye and brain work together, the human brain interprets a full moon lying near the horizon to appear larger than when it lies high in the sky, away from the horizon. The illusion can be demonstrated with the picture below - both "moons" are in fact the same size.
To check the real size of the moon when it appears "huge", use this trick: get a 5 pence coin and hold it between your thumb and forefinger at arms length. Move it along so it covers the moon. You will see that the "large" moon close to the horizon actually is suddenly much smaller than it appears, as the coin forces the eye to adjust.