11.   The science is complicated, but it has to do with how the gravitational attraction of the sun and moon effects on our planet.

12.   These places were thought of as black because their gravitational attraction is so powerful that it consumes surrounding matter and does not permit the escape of any light.

13.   Until several years ago, scientists were all but certain that the gravitational attraction among the galaxies would slow the expansion.

14.   With masses about the same as that of the Sun, such stars begin their lives when interstellar hydrogen is drawn together by gravitational attraction into a dense cloud.