From: V Laxmanan (vlaxmanan@hotmail.com)
Date: Tue Jan 06 2004 - 20:54:14 PST
Eratosthenes Experiment on Mars using the Sundial Posted by V. Laxmanan, January 6, 2004 After the landing of NASA's Rover on Mars, I started thinking about an interesting experiment and sent the following email to the Principal Investigators at the NASA's JPL. As noted in my earlier posting today (Jan 6, 2004), and in other earlier postings, the shadow lengths reported by students do not agree with the theoretically predicted values (if we make the assumptions made by Eratosthenes, spherical earth and parallel rays from the sun). These anomalies suggest that we need some real precision measurements, even here on Earth. Now, with Rover on Mars, it would be of interest to repeat the Eratosthenes Experiment on this planet as well. We are looking for signs of life on Mars. But, if you think about it, humans indeed, are now the aliens on Mars with our new gadgets. However, repeating the Eratosthenes Experiment here might not be as easy as it sounds. For example, we do not know if there is an equinox on Mars, or when it occurs. Although, this is not important, the mathematics is much more complicated if we use shadow length measurements made on days other than the equinox. But, I would say, let's first get the data now that Rover is on Mars and then let's worry about the theory, math, etc. ******************************************* The following is the text of the email message sent to Professors Bell and Squyres about the proposed experiment. Dear Professors Bell and Squyres: For the last hour, I have been watching the Mars News Conference, where both of you were answering questions. Your remarks about the Mars Sundial caught my attention. I was very excited and then visited the JPL and Cornell University websites to see if I could find photos of the Mars Sundial. I am both excited and also a bit disappointed. Let me explain. As you know, the sundial is a vertical stick that casts a shadow. As the earth makes its daily rotation about its own axis, the length of the shadow changes. The orientation of the shadow also changes (with respect to east-west direction here on earth) and this can be used to tell time. And, as you know, the Greek Eratosthenes, however, did something remarkable from the shadow length observations at Alexandria and Syene, in ancient Egypt. He deduced the radius and hence the circumference of the earth from the shadow length measurements, on the day of the equinox. Interestingly, the Eratosthenes Experiment is now being repeated and performed by elementary, middle, and high school students, and even some college students, from all over the world. This has yielded large volumes of shadow length data from various latitudes, not available to Eratosthenes. I got interested in this work about a year ago and started analyzing the shadow length data reported by students, over the last five years, since such data was made available on the Internet. I notice some interesting anomalies as a result of my analysis. To make a long story short, I find that the shadow lengths do not agree with the theoretical values (see attached Microsoft Word and PowerPoint files). The discrepancies are much too large to be attributed to errors in shadow length measurements and even genuine experimental difficulties. I have discussed these points in articles posted on the website Eratosthenes Experiment Project (see http://www.youth.net/ , then click on Eratosthenes Experiment). This has certainly generated some interest and from time to time I have received emails from students and teachers from around the world. I have also performed the experiment, myself, during the equinoxes on March and September 2003. However, I would like to perform even more accurate measurements and have some ideas about how to build a very precision unit (or you may call a sundial) to reduce errors in the measurements. After the successful landing of Rover on Mars, I started wondering if we could make shadow length measurements on Mars using either the Mars sundial or any of the vertical posts that are located on the Rover and whose shadows fall on what can be reasonably taken to flat surfaces. From such data we can compute the radius of Mars, if we make the assumptions made by Eratosthenes. We can also use the times taken by European and NASA spacecrafts now orbiting Mars to deduce the mass and the radius of the planet. (I have also been studying the orbits data for the space shuttle and the spacecrafts that orbited the moon and again I notice some interesting anomalies, see articles on the website noted above). Ultimately all of the anomalies that I briefly noted here lead me to suspect that we may have to take a hard look at Newton's inverse square law. This law has never been challenged and is also retained by Einstein to develop the general theory of relativity. In summary, I hope I have sparked some interest. If so, I would very much to find out how I can work with you and other scientists at NASA and JPL on this exciting project, viz., repeating Eratosthenes Experiment on Mars using the Rover. I can be reached at vlaxmanan@hotmail.com. Very sincerely V. Laxmanan _________________________________________________________________ Expand your wine savvy — and get some great new recipes — at MSN Wine. http://wine.msn.com