The idea of all the planets in our solar system aligning perfectly is a misconception. While the planets do occasionally appear close together in the sky from Earth's perspective, they never truly align in a perfect line.

Here's why:

* The planets orbit the Sun in different planes: Each planet's orbit is slightly tilted compared to the others, so they won't all be in the same plane at the same time.

* The planets move at different speeds: Each planet takes a different amount of time to orbit the Sun. This means they are constantly changing their positions relative to each other.

However, there are times when the planets appear to be close together in the sky, known as planetary conjunctions. These events can be quite spectacular to observe.

The last time the major planets (Mercury, Venus, Mars, Jupiter, and Saturn) were in relatively close alignment in the sky was in December 2020. This doesn't mean they were perfectly lined up, but they were all visible within a small section of the sky.

It's impossible to say exactly when all the planets will "align" again in a perfectly straight line, as this is not a real phenomenon.