The planets in our solar system never line up in one perfectly straight line like they show in the movies.
If you look at a two-dimensional plot of the planets and their orbits on a piece of paper you may be lead to believe that all the planets will circle around to the same line eventually.
In reality, the planets do not all orbit perfectly in the same plane. Instead, they swing about on different orbits in three dimensional space. For this reason, they will never be perfectly aligned.
Planetary alignment depends on your viewpoint. If three planets are in the same region of sky from Earth’s point of view, they are not necessarily in the same region of sky form the sun’s point of view.
Alignment is therefore an artifact of a viewpoint and not something fundamental about the planets themselves.
Even if the planets did all align in a perfectly straight line, it would have negligible effects on Earth.
Fictional and pseudo-science authors like to claim that a planetary alignment would mean that all of the gravitational fields of the planets add together to make something massive that interferes with life on Earth.
In truth, the gravitational pulls of the planets on the Earthare so weak that they have no significant effect on Earth life.
There are only two solar system objects with enough gravity to significantly affect Earth: the moon and the sun.
The sun’s gravity is strong because the sun is so massive. The moon’s gravitational effect on the Earth is strong because the moon is so close.
The sun’s gravity causes Earth’s yearly orbit and therefore, combined with earth’s tilt, it causes the seasons.
The moon’s gravity is primarily responsible for the daily ocean tides. The near alignment of the sun and the moon does have an effect on the Earth, because their gravitational fields are so strong.
This partial alignment occurs every full moon and new moon, and it leads to extra strong tides called ‘spring tides’.
The word ‘spring’ here refers to the fact that the water seems to leap up the shore with the extra strong tides every two weeks – not that they occur only in the spring season.
Source: Dr Christopher S. Baird/West Texas A&M University