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Guru
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Bode's Law

06/04/2006 9:54 AM

Engineers know Bode diagrams and Bode plots well, but do you know about Bode's Law? It has to do with the spacing of the planets of our solar system. According to Wikipedia, it was discovered in 1766 by Johann Daniel Titius and "published" without attribution in 1772 by the director of the Berlin Observatory, Johann Elert Bode, thus the name. However, some say it was first proposed by Christian Wolff in 1724. Whatever the case may be, it was not the same Bode (Hendrik Wade Bode) that gave us our Bode plots. Today the astronomical 'law' is generally known as the Titius-Bode Law. It says that the distance of a planet from the Sun is roughly given by:

D = 0.4 + 0.3N a.u., where N = 0,1,2,4,8,16…, i.e. integer(2^(n-2)) and n is the n'th planet from the Sun, counting in the largest asteroid (Ceres) as number 5. The unit a.u. is astronomical unit, the mean distance of Earth from the Sun.

Nobody knows why this formula (or 'law') works, but it does... up to a point. Read more by clicking this link . The page contains a downloadable PDF with lots of info.

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The Engineer
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#1

Interesting Problem

06/05/2006 9:52 AM

I noticed in the paper that you link to that you mention extrasolar planetary systems seem to have the same characteristics, in particular the Pulsar with the three planets. I guess my question is regarding the majority of the extrasolar planets found to date which tend to be Jupiter size planets in Mercury type orbits about their stars, do these fall into the pattern as well, or is it too early to know?

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Guru
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#2
In reply to #1

Re:Interesting Problem

06/05/2006 1:44 PM

I'm afraid I don't recall mentioning this about extra-solar planets - it must be some other paper! (Give me a reference if you remember it). As far as I know, there is not enough data yet to detect similar patterns in extra-solar planets.

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Guru
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#3
In reply to #1

Re:Interesting Problem (erratum)

06/05/2006 2:00 PM

Sorry Roger, I missed my own quote in my own PDF - you were right! Still, it's probably too early to say. The most promising ideas today have to do with "orbital resonance", something nobody seems to understand very well.

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The Engineer
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#4
In reply to #3

Re:Interesting Problem (erratum)

06/05/2006 3:13 PM

Yes, I meant to comment that the pattern seems like the normal modes in an periodic system (like springs and masses). With all the gravitational interactions going on I can see why it's difficult to figure out.

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