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Why Is the Solar System Flat?

It’s no mystery that the planets, moons, asteroids, etc. in the Solar System are arranged in a more-or-less flat, plate-like alignment in their orbits around the Sun.* But why is that? In a three-dimensional Universe, why should anything have a particular alignment at all? In yet another entertaining video from the folks at MinutePhysics, we see the reason behind this seemingly coincidental feature of our Solar System — and, for that matter, pretty much all planetary systems that have so far been discovered (not to mention planetary ring systems, accretion disks, many galaxies… well, you get the idea.) Check it out above.

Video by MinutePhysics. Created by Henry Reich

*Yes, I know about barycenters/centers of mass being the real orbital foci for everything in the Solar System, including the Sun. Let’s not get nitpicky.

About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Comments on this entry are closed.

  • Michael Martinez January 21, 2014, 11:24 AM

    This video makes it sound like there are only three dimensions in the physical universe, so Space Time doesn’t seem to have anything to do with how planetary systems form (via gravity). Maybe he should do a follow up video to explain that.

    • Olaf2 January 21, 2014, 12:56 PM

      Space-time has almost no effect because the masses and the velocities are tiny to have any effect. It does have an effect on mercury.

    • Jose Luis January 22, 2014, 3:35 AM

      The video does mention, albeit quite fast and briefly, a “three dims space “, which I understand as “a three spatial dimensions space” something correct also for our four-dimensional space-time. In the video, the time dimension is only involved in the natural time evolution of the initial particle system up to the present solar system, but not in a relativistic way. In my opinion, no further explanation is required and would unnecessarily complicate things for such a simple explanations of the observed solar system flatness.

      • Michael Martinez January 22, 2014, 11:51 AM

        Not everyone has an equal understanding of physics and the math involved. But I’ll grant you can only explain so much in a single brief video.

  • john kulick January 21, 2014, 3:15 PM

    This topic leads an issue about the formation of our solar system.
    As the nebular cloud collapses, there would be a dispersal of the momentum throughout the cloud. For example, if half way out in the cloud a region was moving 3 times as fast as the surrounding matter, collisions with the slower moving particles would cause an “even ing” out of the momentum.
    Now as the matter is drawn in towards the gravitational center, the momentum of the matter would be carried with it as well. If 99.9 percent of the mass is found in the sun, then 99.9 percent of the angular momentum should be found in the sun.
    This is not the case. Some how most of the angular momentum of the solar system resides with Jupiter.
    How could this occur?
    It is my belief that this is evidence our “mini proto sun” blowing up when the effect of gravity was much greater in the past. This would displace the momentum back outwards into the solar system. The evidence of this explosive event in our early solar system is overwhelming.

  • straw walker January 21, 2014, 3:15 PM

    The Solar System is flat from extending the “x” axis of the Suns equator. This is Newton’s gravity, not Einstein’s curved space gravity. The Solar System does NOT demonstrate curved space. as the planet’s orbits are flat, just as the Galaxies are flat as a pancake as they extend outward from the mass of a Black Hole.
    If there existed curved space the planets orbits would demonstrate this curvature. The Comets and asteroids that approach the Sun perpendicular to this plane also do NOT demonstrate curved space.
    The Solar System has never demonstrated orbital decay, again a theory of Einstein, (Mercury’s orbit is NOT orbital decay, but movement of it’s perigee). Some would suggest a binary pulsar shows orbital decay, but our knowledge of Pulsars could be totaled in a small paragraph containing mostly guesses.

    • Jose Luis January 22, 2014, 3:55 AM

      The video deals with the flatness of solar system orbits, that all lie in the same plane. These orbits are obviously curved (in a plane), as they are elliptical. A curvature in the Z axis would require additional accelerations that have no possible known source. The only possible alternative would be the (wrong) “atom model”, that would be in contradiction to astronomical observations, and the video provides an explanation of why it is not so. Short periodic comets, that also orbit the Sun are exceptions, as they have orbits with inclinations of ten or more degrees, but they are affected by gravitational effects by our giant planets and their orbits and inclinations have much changed in the past and continue to change.

      • straw walker January 22, 2014, 12:32 PM

        Elliptical orbits do not demonstrate curved space, but reflect the 2nd law of Kepler.
        Einstein’s curved space theory would suggest the perigee point of the planets elliptical orbits would have to be near the bottom of the Sun and the orbits would have a “basket effect” pointing upwards. This is not observed, as the orbits are on a plane.

        The next problem for the curved space theorists, is how the planets would follow this curvature in their ever increasing concentric alignments.. example; Mercury’s orbit is inside Venus, which is inside Earth’s and so on.

        These orbits do not reflect any curvature to space. and cannot be demonstrated to do so.
        The real problem with General Relativity is that Gravity waves, Mass waves have never been detected.
        We know that the Sun/star does distort space, but how?
        The Cassini space probe sent back a message to earth that was delayed as it passed by the Sun.
        The question is what caused this?
        The Sun did not curve space
        The Suns magnetic field contracted space and time.

  • newSteveZodiac January 22, 2014, 6:40 AM

    I presume the gyroscopic principle tends to prevent collapsing cloud systems from flipping end over end as well as rotating on one axis but even with a gyro there is precession, as in the Earth’s spin. Has anybody observed precession in the solar system or in galaxies or is the time-frame too long?

  • ashok v patil January 22, 2014, 7:29 AM

    It is all based on simple laws of motion and gravitational force. As the matter starts gravitating at a single point, a torque is formed, and all the matter starts rotating around an axis. (much like water gushes out of a holed bucket). As the gravitational force is maximum on the equatorial plane, all the planets tend to remain on the equatorial plane. (Exactly like moon which always revolves around Earth’s equatorial plane).

  • Suzanne Ennazus January 22, 2014, 4:08 PM

    I always wondered that, but I was told the images are simplified and
    junior school suited, and some planets such as Pluto don’t have a flat
    orbit.

    • IVAN3MAN_AT_LARGE January 22, 2014, 4:25 PM

      That’s why Pluto is not a planet.

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