Are tides really higher during a full moon? The moon isn't any larger, and doesn't have a stronger gravitational pull, after all, just because we can't see part of it!

It is fuller than when the moon is cresent or any position between full and new. But, the tide at full moon is no higher than when at new moon. The resaon for the higher tides at these two positions is that the Moon and Sun are in conjuction: directly in line with the Earth. At these positions their gravitation forces supplement each other, which is in contrast to their effect when they are at right angles to each other relative to the Earth, and tend to cancel out one another, and produce low tides.

Minnesota is right
the moon is not the only reason for the tides.
The sun has the same effect on the water, except about 1/8 the gravitational force of the moon.

So when the sun and moon are on the same side of the earth, the tides are higher,
and when they are on opposite sides, they are lower.

-Chris

Bibc

Two corrections:

The tide generating power of the Sun is .4576% (27/59) that of the Moon.

As mentioned in my answer above, when there is a full moon (where the earth is directly between the Sun and Moon), high tide (spring tide) also takes place; the same as it does when there is a new moon (where the Moon is directly between the Sun and Earth). Low tides (neap tides), as I pointed out, occur when the Sun and Moon form a right angle with the Earth and the Moon appears as a cresent.

Yes both the moon and the sun create tidal forces on earth...

Tidal forces vary as the inverse cube of the distances between the masses. The mass of the moon is 7.35 x 10²² kg and its distance is 384,400 km. The mass of the sun is 1.99 x 10³⁰kg and its distance is 149,597,870 km. Therefore moon/sun = (7.35 x 10²²/384,400³)/(1.99 x 10³⁰/149,597,870³ = 1.29 x 10⁶/5.94 x 10⁵ = 2.17 which means the moon has more than twice the effect on tides as the sun.

minnesota, thanks for correcting that.
i forgot that high tides also occur when the earth is between the sun and moon,
and that low tides occurr when the two are perpindicular to the earth.

i am sure that you are right,
but i just get confused because logically it would seem that when the earth is between the moon and sun, the forces would somewhat cancel each other out resulting in a lesser gravitational force and a lower tide.

have any idea why it is otherwise?

Bibc14:
They don't "cancel" even though the two bodies (sun and moon) are on opposite sides of the earth because of the nature of tidal forces.

When the sun and moon are on opposite sides of the earth, they do indeed pull in opposite directions. But tidal forces arise from the gradient of the gravitational force. That is, tides arise from the fact that the gravitational forces vary across the diameter of the earth because different parts of the earth are at slightly different distances from the center of mass of the moon or the sun.

This produces an axis of symmetry along which the sphere becomes elongated (so-called bulges at the near and far sides). It doesn't matter whether this axis represents stronger-to-weaker or weaker-to-stronger gravitational pull.

So if the axes line up, they reinforce each other and produce greater tides. If they are perpendicular (at half-moon) then the earth is elongated in perpendicular directions, becomes less distorted and consequently has smaller tides.