### Dec

#### 7

# Planetary Interactions, from Phil McDonnell

December 7, 2007 |

Victor and Laurel have suggested that a fruitful area for market research may lie in replicating the methods of Brahe and Kepler. Brahe scrupulously gathered very precise data though years of observations. It was left to Kepler, his student, to develop the first model. Kepler first identified planetary orbits as elliptical.

Suppose we have two planetary bodies with periods P1 and P2 respectively. A quick review of Kepler's Laws reminds us that his third law is as follows:

P1^2 / P2^2 = R1^3 / R2^3

where R1 and R2 are the semi major axes of the two bodies. It is interesting to note that there are no linear terms in the above relationship. It can be read as the ratio of the squares of the periods are equal to the ratio of the cubes of the axes.

In the markets we know that the Efficient Market Hypothesis tells us that the market price change today should have no linear correlation with the price change tomorrow. Empirically this seems to be true most of the time for most markets. However a strict interpretation of EMH says nothing about the existence of non-linear relationships.

In particular when we evaluate the squares of changes we find they are significantly correlated. The same holds for the cubes at similar lags. It is left as an exercise for the reader to calculate the magnitude and direction of such correlations. So at first blush there may be an application for Kepler's third law in the markets.

In order to see if there is any similar Keplerian relationship in daily price series the data from the table on page 121 of Education of a Speculator hardback was studied. Using the midpoints of the classes in the table the model used only the squares and cubes of change to predict the next days performance. It turns out that the fit is statistically significant. Notably there is no linear term in the model. Checking whether a linear term would help, the data showed that it would not be helpful. Although the regression model was statistically significant it was based on out of date data and would have to be redone with current data.

## Michael Cook remarks:

Kepler was not a student of Brahe; he came to Brahe's observatory because Brahe had good data, continuous night by night observations of the planets. Kepler was desperate to prove that the orbits of the planets were circles, because the circle is the perfect shape, consistent with the beauty of the divine Mind. He decided to work on Mars because it seemed to be closest. After much work he realized the ellipse was a better fit. His comment: "I set out to show that the universe was based on the eternal harmony of the spheres. Instead I showed that it rests on a carthill of dung [the ellipse]."

The other beautiful law of Kepler's is that the planets sweep out equal areas in equal times.

It is also significant that all of his laws can be deduced mathematically from the inverse square law of gravitation.

## Adam Robinson replies:

As I'm sure Dr. Cook realizes, the point was that the law of gravitation can be deduced from Kepler's laws, as indeed Robert Hooke (whose insights into force and inverse square relationships were at least contemporaneous with Newton's) was able to do. Newton's genius (in that regard, there were many instances of course) was in showing the equivalence of the acceleration of a falling object with the acceleration of an object in orbit.

Newton, in other words, gave the relationships a theoretic underpinning (until then Hooke's insights, along with Kepler's, were mere "curve fitting," in the literal sense of the phrase!), just as Einstein did, since numerous scientists at the time (Poincare for one) had come to similar conclusions (e.g., the Lorentz contraction), but lacked any overarching theory to explain why such phenomena had to occur.

Dr. Cook's quotation of Kepler also reveals the extent to which aesthetics can hinder the progress of theory as much as promote it.

## Michael Cook responds:

Actually, I am not aware of any derivation of the inverse square law from Kepler's laws. I believe Hooke claimed to derive Kepler's laws from an inverse square law, which resulted in Newton's publishing his proof of the result. Hooke never published an actual proof — it's hard to do without calculus. Feynmann has a paper in which he does so, which I don't think he would have published it if it were already in the literature.

It is incorrect to say the law of gravitation can be deduced from Kepler's laws — Kepler's laws are descriptive, and don't by themselves imply any causal mechanism.

## Adam Robinson replies:

I refer Dr. Cook to the letters between Hooke and Newton; there was much controversy between the two about who had which insights, when. Hooke's insight was more of a conjecture, not a formal "derivation" as such. Not surprisingly, of course, since Hooke's inverse square law with springs contains a surprising analogue with gravitation.

## Kim Zussman writes:

A recent Bloomberg article on Jim Simons of RenTech mentions sunspots and markets, so along with Kepler's dung [see Dr. Cook's remarks above] this must explain the beauty of markets.

Recall that sunspots (which have been observed and recorded since well before Galileo) are magnetic storms on the sun, which appear dark in contrast to the photosphere because (though they are hot) they are relatively cooler. And to the extent that there may be related effects on solar wind (solar ions flowing past the earth), radiation levels, and earth's ionosphere, and radio/satellite communications, here is a study.

Monthly average sunspot count (American, of course) 1944-2007 is available from the National Geophysical Data Center:

Regression of SP500 monthly index return vs. monthly avg sunspot count (1950-Oct 07) shows almost significant negative correlation (P=0.07):

Regression Analysis: SP CHG versus SPOT AV

The regression equation is

SP CHG = 0.0110 - 0.000052 SPOT AV

Predictor Coef SE Coef T P

Constant 0.010961 0.002534 4.33 0.000

SPOT AV -0.0000518 0.000029 -1.79 0.074

S = 0.0405916 R-Sq = 0.5% R-Sq(adj) = 0.3%

Analysis of Variance

Source DF SS MS F P

Regression 1 0.005288 0.005288 3.21 0.074

Residual Error 691 1.138548 0.001648

Total 692 1.143836

Here is a plot of monthly avg sunspots vs date, which clearly shows the 11 year solar cycle. Note that we now near a minimum (good for stocks), and regardless of Fed actions relative to the housing market, explains the recent 5 year bull market (OK the last sunspot maximum was Sept 2001, so the prediction was off by about 1.5 yr).

## Eric Falkenstein remarks:

One of the keys of finance is the implication that arbitrage implies that pricing is linear in 'risk', or whatever is priced. Otherwise, you could generate arbitrage by buying bulk and selling little bits, or vice versa. It is intriguing to think that there are nonlinear relations in markets, but these necessarily imply profits, so, to the degree they exist, they must not be too obvious (please email me the exceptions!).

203e# Comments

## Archives

- November 2017
- October 2017
- September 2017
- August 2017
- July 2017
- June 2017
- May 2017
- April 2017
- March 2017
- February 2017
- January 2017
- December 2016
- November 2016
- October 2016
- September 2016
- August 2016
- July 2016
- June 2016
- May 2016
- April 2016
- March 2016
- February 2016
- January 2016
- December 2015
- November 2015
- October 2015
- September 2015
- August 2015
- July 2015
- June 2015
- May 2015
- April 2015
- March 2015
- February 2015
- January 2015
- December 2014
- November 2014
- October 2014
- September 2014
- August 2014
- July 2014
- June 2014
- May 2014
- April 2014
- March 2014
- February 2014
- January 2014
- December 2013
- November 2013
- October 2013
- September 2013
- August 2013
- July 2013
- June 2013
- May 2013
- April 2013 207c
- March 2013
- February 2013
- January 2013
- December 2012
- November 2012
- October 2012
- September 2012
- August 2012
- July 2012
- June 2012
- May 2012
- April 2012
- March 2012
- February 2012
- January 2012
- December 2011
- November 2011
- October 2011
- September 2011
- August 2011
- July 2011
- June 2011
- May 2011
- April 2011
- March 2011
- February 2011
- January 2011
- December 2010
- November 2010
- October 2010
- September 2010
- August 2010
- July 2010
- June 2010
- May 2010
- April 2010
- March 2010
- February 2010
- January 2010
- December 2009
- November 2009
- October 2009
- September 2009
- August 2009
- July 2009
- June 2009
- May 2009
- April 2009
- March 2009
- February 2009
- January 2009
- December 2008
- November 2008
- October 2008
- September 2008
- August 2008
- July 2008
- June 2008
- May 2008
- April 2008
- March 2008
- February 2008
- January 2008
- December 2007
- November 2007
- October 2007
- September 2007
- August 2007
- July 2007
- June 2007
- May 2007
- April 2007
- March 2007
- February 2007
- January 2007
- December 2006 a70
- November 2006
- October 2006
- September 2006
- August 2006
- Older Archives

## Resources & Links

- The Letters Prize
- Pre-2007 Victor Niederhoffer Posts
- Vic’s NYC Junto
- Reading List
- Programming in 60 Seconds
- The Objectivist Center
- Foundation for Economic Education
- Tigerchess
- Dick Sears' G.T. Index
- Pre-2007 Daily Speculations
- Laurel & Vics' Worldly Investor Articles