Why are solar systems planar?

In part of my shift from the negative field of economics to the positive field of technology, I have gotten myself hooked on a really great PBS TV series called Nova.  On Amazon Prime, season 5 is free right now, starting with the question “Can we go to Mars” in which Neil Degrasse Tyson goes into depth on a number of issues about colonizing Mars with actual Nasa visits, astronauts, and other industry experts.  I finished that season and started purchasing others.

Back to the question about why solar systems are planar… its really very simple and it occurred to me while driving through traffic the other day.

Solar System

Gravity is an attractive force between centers of mass.  This force pulls all of the planets together – so in a way you can think of think of any illustration showing the planets closer to each other as being “down”, with gravity moving the system towards this just like it pulls water down a hill.

Now make some quick assumptions that make it easy to picture:

  1. The planets orbit at a fixed distance from the sun.  This is determined by the momentum of the planets and the sun’s gravity, which dwarfs any influence the planets have on each other.

2. Think of the orbits – as drawn above – as rings that are a fixed distance from the sun but free to rotate in any direction.  The sun’s gravity has no effect on the angle the planets rotate at because the distance is always the same.

3. Now consider the affect of the rings on each other.  As I stated above, gravity would have them as close to each other as possible. It is easy to visualize how making the rings rotate all on the same plane brings them as close together as possible in this scenario.

Now think back to individual planets … how does this happen.  You have two planets with skew orbits that periodically have points at which they are closer together, in which they pull each other noticeably closer.  Any affect in the radial direction (inward or outward) is ultimately corrected by the outward force of the planet’s angular momentum balancing with the force of the sun’s gravity.  However, the sun’s gravity does not correct any movement in the angular direction of the planets when they pull closer – and as a result the planes both planets travel in remain affected slightly, like two rings being pushed closer together.  Over many rotations, the orbits of the planets will align into the same plane.

The other question I brought up last week is a much tougher one – it will require actual research rather than a quick “Eureka” moment.  Here is a chart of the scientific method:


Question:  Are there forces in natural evolution besides natural selection?  More specifically, are the genetic mutations that occur in nature totally random shifts in the genetic code, or is there a link between the lives & environment of the animals and the genetic mutations that occur?

Hypothesis:  The lives of animals prior to mating such as how different body parts and organs are stressed can influence the direction that successful evolutionary mutations take.

The statement that enough monkeys randomly hitting enough typewriters would eventually replicate the complete works of William Shakespeare never sounded convincing to me.  Nature has a lot of forces we don’t understand, DNA is exceptionally complex, and it simply doesn’t make sense that it’s assembly and variations are purely random.

Just like I couldn’t accept a planar solar system as a random coincidence and explained above how nature pushes this together, I believe there are forces here we just don’t understand yet.  It would make a lot more sense to me to discover that there are actually connections between the types of RNA the body demands for specific proteins and enzymes and how strands of passed-on DNA mutate, forming a sort of natural feedback loop.  This method would be particularly compelling if it could account for sections of DNA – which can be effectively turned “off” or “on” by certain genes, being slowly changed over time (but guided through feedback mechanisms in a particular direction) so that when they turn “on” it could change a number of things at once.  This system would ultimately allow genetic mutations to be “written” over a period of many reproductive cycles so that it could result in creating birds capable of flight without requiring either a whole series of debilitating partial changes leading up to that point or a monkey that successfully randomly hammered out Shakespeare in one sitting.

If this reasoning was sound, then in order to be fully understood we would need to look heavily into the reproductive process at the DNA level – how it combines and replicates to form the DNA of the offspring.  Based on my limited understanding of molecular biology, this is where it makes the most sense for a type of RNA feedback to take place.  Unfortunately I’d imagine that looking here would require information that is not easy to come by and might even require testing with resources I don’t have.

However, there is a much simpler place to start.  There is a lot of data out there on evolutionary patterns, and I could try to find examples which would point to environmental feedback … such as how long it took (according to latest models – provided the assumptions aren’t DNA-based in a way that conflicts with my hypothesis) for different evolutionary changes to take place.  I could chart them out and see if these tend to happen significantly faster than a system of totally random mutations combined with natural selection would predict.

I’ll leave it on that note and call it a night.  I’ve always been curious about the inner workings of things – first in science, then in markets, then in political/sociological systems, and now back to science again.  It’s not like any of these interests ever come and go, they are always there, it’s just what I choose to focus on.


About johnonstocks

I've been trading stocks since 2003, active on Motley Fool's discussion boards and using first Hidden Gems, then Global Gains. I no longer have the newsletters, but I keep up on the WSJ and read David Rosenberg everyday at gluskinsheff.com. Education: CFA level 2 candidate MBA-focus in Finance, Marshall, University of Southern California - expected Dec 2010. BS Mechanical Engineering, UC San Diego, June 2002
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