Neptune discovery in physics class: activities and simulations Hezi Yizhaq, Environmental High...
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Neptune discovery in physics class: activities and simulations Hezi Yizhaq, Environmental High School, DAT Fulbright Teacher from Israel Email Address:
Neptune discovery in physics class: activities and simulations
Hezi Yizhaq, Environmental High School, DAT Fulbright Teacher from
Israel Email Address: [email protected] Matthew Bobrowsky,
Department of Physics, University of [email protected]
Email Address: [email protected]@umd.edu
Slide 2
Introduction: Planet Orbits Kepler's laws of planetary motion
are three scientific laws describing orbital motion, each giving a
description of the motion of planets around the Sun (1619).
Kepler's laws are: 1. The orbit of every planet is an ellipse with
the Sun at one of the two foci. 2. A line joining a planet and the
Sun sweeps out equal areas during equal intervals of time. 3. The
square of the orbital period of a planet is directly proportional
to the cube of the semi-major axis of its orbit.
Slide 3
Newton's law of universal gravitation (1687) explains Keplers
laws Every point mass attracts every single other point mass by a
force pointing along the line intersecting both points. The force
is proportional to the product of the two masses and inversely
proportional to the square of the distance between them
Slide 4
Uranus A very badly behaved planet Discovered by William
Herschel in 1781 Period of revolution 84 years, average distance
from the Sun is: 19.22AU. After 1800 discrepancies started to be
apparent between the planet position as predicted by theory and as
measured in the sky
Slide 5
Discrepancies between the observed and the calculated
longitudes of Uranus after known causes have subtracted
Discrepancies between calculated to observed longitudes
Slide 6
An Astronomical Mystery Two possible explanations: 1.Newton's
law of gravity might not hold as distances as great as Uranus i.e.
the law of gravitation is not universal !!! 2.The law of
gravitation is correct but there is another unseen planet far
beyond Uranus which perturbed its orbit.
Slide 7
Where to look for the new planet? Bode Titus law (1772) An
empirical law for the distances of planets from the Sun
Slide 8
The Search for the Missing Planet Independently, two
astronomers, John Couch Adams in England and Urbain Jean Josef Le
Verrier in France, calculated the position of this yet unknown
planet. Le Verrier was already a know scientist whereas Adams was a
young Cambridge undergraduate, 26 years old, who seems to have
taken on a own personal quest to search for an explanation for the
apparent misbehavior of Uranus. Urbain Le Verrier John Couch
Adams
Slide 9
Neptune Discovery Chronology In October 1845, Adams wrote to
George Airy, the Astronomer Royal of Greenwich Observatory,
claiming that he had solved the problem of Uranus' orbit, and
stating the position where the unknown planet could be found. In
December 1845 Le Verrier independently published a short manuscript
on the orbit of the missing planet. Neptune was ultimately
discovered by the German astronomer Johann Galle, on September 29,
1846, using Le Verriers predictions.
Slide 10
Why Neptune was not discovered in England? In October 1845,
Adams wrote to George Airy, the Astronomer Royal of Greenwich
Observatory, claiming that he had solved the problem of Uranus'
orbit, and stating the position where the unknown planet could be
found. Now, if Airy had pointed a telescope at that spot, he might
have found Neptune (however, not at the exact spot that Adams had
pinpointed). Although, he tried to conceal it, Airy had a strong
negative reaction to Adams paper. His altitude later turned out to
be of critical importance to the fact that Neptune was not
discovered in England. The problem was that Airy was strongly
opposed to theoretical investigations and skeptical of the
abilities of younger scientists. He was not the sort of man to take
a leap into the scientific unknown. God forgive me for writing in
this way The truth lies on the other side & Adams is the 1 st
theoretical discoverer of Neptune. The whole thing was parried [?]
and perverted by Airys indefensible reticence. On him be the
responsibility of the (temporary) transfer of one of the brightest
stars in Britains Scientific fame to France. British Astronomer
John Herschel-1846
Slide 11
Star Map from the Day of Discovery
Slide 12
Who was Neptunes discover Le Verrier, Adams or Galle?
Slide 13
Developed Activities Finding the year of conjunction by
performing time numerical derivative of the data
Slide 14
MATLAB Numerical Simulations of Planet Orbits Using Feynmans
Method
Slide 15
The program can calculate different physical quantities Neptune
Uranus
Slide 16
Calculation of the perturbation near the conjunction Assuming:
Circular orbits, conservation of energy and angular momentum of the
system the students will find the perturbed radius of the planet
near the conjunction Numerical Solution of the Corrected Orbit of
Uranus (unperturbed orbit=19.22AU,R2=38.8AU )
Slide 17
The Discovery of Neptune and the Dark Matter in the Universe
Rotation Curves in the Solar System Rotation Curves in the Milky
Way