When will all the planets in our solar system align?

The next planetary alignment in the solar system will occur in 2854. While the planets will not ever be aligned in a straight line, they will reach their closest possible proximity that year.

According to Cornell University astronomers, the last instance of this type alignment was in 581 BCE. It is impossible for all planets to align in a straight line at any point, because of differences in orbit length and planetary placement within them. Calculations show that at their closest possible alignment, they lie within 30 degrees of each other. Astronomers do not consider planetary alignment to be of scientific importance. However, planetary alignment is crux in the pseudo scientific study of astrology.