The effect of gravity of the moon and the sun on our planet known. The strength of their influence is that every day is the ebb and flow. On land, this effect does not occur, because it is hard. However, even the land changes its spatial position, raising towards disturbing luminaries crust tectonic plates.
But since the whole pripodymaetsya layer evenly, we did not notice. And if the forces of gravity influences of the moon and the sun are so great and obvious that they make to move billions of tons of water in the ocean at high tide, then why are these forces can affect a grain of sand as a man or a dog?