The helical model: do planets move in spirals?

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A 2012 viral video showed the planets moving in a spiral (“helix”) pattern due to the Sun’s motion through space. It also criticised the “heliocentric” conception of the Sun as being at rest with the planets on roughly circular orbits around it. This raises an interesting question about frames of reference:

(See also the 3rd and improved version embedded later). The author, music producer “DjSadhu”, has made a beautiful animation complete with Tron-style trails for artistic effect. However the main issue is the claim, “The old heliocentric model of our solar system… is not only boring but incorrect.” He continues, “Our Solar System moves through space at 70,000 km/hr”. He calls the planet orbits “rotation” for the stationary Sun perspective, and “vortex” for the moving Sun perspective; this is not standard terminology but we can understand his point.

This issue is that it is equally valid to choose either frame of reference. If we choose a non-rotating frame centred on the Sun, then from this perspective the Sun is at rest and the planets move in circles (approximately). If instead we choose a non-rotating frame centred on our Milky Way galaxy, then from this perspective the Sun is moving at 800,000 km/h (a dozen times higher than the figure in the video) and the planets move in helices, approximately. We could take this further and incorporate the galaxy’s own motion relative to the local universe, or any other natural (described earlier) or hypothetical motion one chooses.

The animator scoured NASA’s website but couldn’t find the helical model. He is probably correct that most of the public has an “incomplete” view, and that “even astronomers” don’t see it this way “even though they may have all the facts that support it.” However, neither would this model be a surprise to them. The concept of relativity of motion is well-known in physics — look up “Galileo’s ship”, a celebrated idea from 400 years ago. I suspect that many physicists would indeed think, “Oh that’s interesting, I hadn’t thought of it that way”, but then also quickly shrug their shoulders and think, “But it’s correct.” But on the other hand, the video fails to understand the merits of the usual conception: it works and it’s simpler! If you are studying planetary orbits in the Solar System, then typically you would ignore external influences as being very minor, and likely choose a coordinate system centred on the Sun (which gives an effective interpretation that the Sun is not moving). The principle of relativity — that the laws of physics are independent (in some sense) of the frame you choose — is a cornerstone of physics, and was furthered by Einstein amongst others. The animator is clearly unaware of what physics/mathematics/philosophy even says on this topic.

Astronomers Phil Plait and Rhys Taylor raised other issues, especially with a second video, including:

  • the Sun does not precede the planets (DjSadhu claims this criticism only applies to the 2nd video), and it is not “dragging the planets in its wake”
  • the Sun does not follow a spiral pattern around the galaxy — this is a misunderstanding of Earth’s precession — but the Sun does bob up and down a little
  • the plane of the Solar System makes an angle of 60° with the Sun’s path through the galaxy, not 90°
  • the correct terminology is “helix”, not “vortex” which applies to fluid flow. The animator’s distinction between “rotation” and “vortex”
  • dubious sources
  • the metaphysical analogy “Life spirals” with pictures of spiral aloe, a fern, rose, spiral galaxy, DNA double helix, shell, and a plughole vortex, was never going to go down well with many scientists.

Taylor wrote:

[Y]ou presented the idea of helical paths as though it were some revolutionary new model. You could have very easily checked with more or less any astronomer who would have told you that we already know this is the case. True, a shiny animation did not exist to show it… [B]ut in context it was saying, “I’m an unqualified DJ who’s overturned all of astronomy“.

To his credit, the animator listened to many of these criticisms. He did also request that people focus on the central claim. Putting aside some things, at his best he writes, “I’m willing to take it down a notch and say there’s more to reality than the heliocentric dinner-plate diagrams. Fair enough?”

This third video, version “2.0”, was praised by Taylor as a “win-win scenario”, stating “bravo, Sadhu, I salute you.” I am discussing this story because I feel it has more merits than flaws overall. So thank-you DjSadhu for sharing your artistic talents! See related animations by Vsauce (16:55–17:54 point, 19:48–end), and Taylor.