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It's one of the most beloved astronomical scenarios of kooks, con-artists and Hollywood producers.
A planetary alignment: when the planets line up with the Sun to form a sort of celestial Newton's Cradle
and the Laws of Physics presumably use the Solar System as a little plaything.
You've probably seen this scenario in a movie or read one of the conspiracy theories online.
The gravitation of the aligned planets would cause a catastrophic force...
..causing earthquakes and tsunamis on Earth, throwing other planets out of their orbits and...
..probably other bad stuff.
Well, obviously, this Mayan apocalypse version of events has never come to pass.
But there are conflicting opinions about whether a true planetary alignment has ever happened.
Some scientists think it just might not be possible, at least not precisely because...
..the planets don't travel on the same exact plane.
It's true that most of them travel at roughly the same level as they orbit the Sun, an area known as the ecliptic...
..but Mercury dips a little above and below that line.
And Pluto is NOT a planet.
But if we were making a Sci-fi adventure movie in the 80's and we wanted to cast Pluto...
It's orbit is so rogue and weird it would never fall in line.
Other astronomers though argue that in the four and a half billion or so years that the planets have been around...
..they've probably fallen into a line at least a couple of times.
The thing is, even though we have a pretty good handle on the planets' orbits...
..there doesn't seem to be a single agreed upon calculation about how often...
..all eight of them will line up closely in three dimensions.
To give you a sense of how hard it is for these eight little ducks to fall in a row...
..it's kind of a big deal when the planets are simply all on the same side of the Sun.
That happened in March of 1982, for example...
..and a few hucksters managed to sell copies of their book by claiming a so called "Jupiter Effect" would...
..cause all sorts of catastrophe on Earth, especially to poor California.
Now, I wasn't born yet, but Hank was and he's fine so... no "Jupiter Effect" in 1982.
In May of 2000, meanwhile, Mercury, Venus, Mars, Jupiter and Saturn all happened to fall...
..into the same slice of the Solar System, about twenty-five degrees across.
But we couldn't see it...because they were all on the other side of the Sun.
Even if all of the planets were to line up with the Sun in true Hollywood fashion...
..nothing would happen to Earth.
Space is big and the planets are small and really far apart.
The vast majority of the gravitational effect felt by Earth is from the Moon and the Sun.
Everything else is negligible.
We can look at it this way: the Sun exerts less than half of the tidal force that the Moon does.
And the next biggest object in the Solar System, Jupiter...
..exerts only 0.001% percent of the force that the Sun does.
In 2000, NASA actually did the math and calculated...
..that even if all of the planets AND moons in the Solar System were lined up precisely with Earth...
..it would exert enough extra gravitation to raise the ocean tides...
..by 1/25 of one millimeter.
Which I think could be an interesting movie...
..but definitely more of a Terrence Malick than a Michael Bay.
But you know what would be an amazing movie with at least some appeal?
Syzygy: when three or more celestial bodies align.
This is a lot more common because it involves fewer parts...
..so it's easier for us to predict and understand.
Every time we can see a solar or lunar eclipse from Earth...
..that's a type of syzygy involving the Sun, the Moon and our home planet.
Which is swell, but there are practical applications too!
In 1966, engineers of the jet propulsion laboratory discovered that Jupiter, Saturn, Uranus and Neptune...
..would align in syzygy 13 years later in 1979.
So, NASA used that math to plot the course of the Voyager 1 and 2 spacecraft...
..allowing them to study all four planets as they passed by, giving us our best look yet at the outer Solar System.
Not only did the disaster not happen, but something really, really awesome happened.
You guys would watch that movie, right?
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