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Astrophysics/Orbital mechanics


Hello! Considering that the earth is gaining as much as 10,000 tons of mass each day in the form of micrometeorites, is this causing our orbit to slow down, to shrink, or both (*has* to be both, right?). I know the time-scales involved make this effect unnoticeable, but I'm curious as to what our orbit might look like in ten million years or so. Thanks in advance! -JMM

Hello, and thanks for your question!

Even at 10,000 metric tons, (1 metric ton = 1,000 kg or 10^3 kg) this is only 10^8 kg which is negligible compared to Earth's mass of 6 x 10^24 kg. Hence, we'd expect no alterations (including slowing) of Earth's orbit from a mass increase this minute.

As for projecting "ten million years" to what Earth's orbit would be like, this is extremely problematical owing to effects from chaos, or non-linear dynamics. While we can very well forecast orbital changes over hundreds of years from celestial mechanics, when you get to millions you have serious problems! These arise from the lack of absolute precision in the initial coordinates, values, say for orbital parameters.

The smaller the predictive timescale, the less critically dependent the process is on chaos – which is very sensitive to initial conditions. More than one researcher has taken great pains to point out that celestial mechanics remains largely unaffected, provided prediction intervals aren’t too long (See, e.g. 'Chaotic Phenomena in Astrophysics', New York Academy of Sciences,   1987, Introduction.)

But predictions for orbital parameters over extremely long timescales, i.e. extrapolating one million years hence is a largely futile exercise. Chaos, intruding via real number extra digits (arising from lack of total precision in initial coordinates), would play havoc with the result.

I suppose if we could somehow manufacture a quantum computer (there are plans on the books) then we might be able to attain such a precision in initial values that enabled chaos to be diminished in the computations, we might get a better handle on this.

For now, however, it's not the case, so there's no way to definitively answer your query right now!


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Philip A. Stahl


I specialize in stellar and solar astrophysics. Can answer questions pertaining to these areas, including: stellar structure and evolution, HR diagrams, binary systems, collapsars (black holes, neutron stars) stellar atmospheres and the spectroscopic analysis of stars – as well as the magnetohydrodynamics of sunspots and solar flares. Sorry – No homework problems done or research projects! I will provide hints on solutions. No nonsense questions accepted, i.e. pertaining to astrology, or 'UFOs' or overly speculative questions: 'traveling through or near black holes, worm holes, time travel etc. Absolutely NO questions based on the twaddle at this Canadian site: purporting to show a "new physics". Do not waste my time or yours by wasting bandwidith with reference to such bunkum.


Have constructed computerized stellar models; MHD research. Gave workshops in astrophysics (stellar spectroscopy, analysis) at Harry Bayley Observatory, Barbados. More than twenty years spent in solar physics research, including discovery of SID flares. Developed first ever consistent magnetic arcade model for solar flares incorporating energy dissipation and accumulation. Developed first ever loop-based solar flare model using double layers and incorporating cavity resonators. (Paper presented at Joint AGU/AAS Meeting in Baltimore, MD, May 1994)

American Astronomical Society (Solar physics and Dynamical astronomy divisions), American Geophysical Union, American Mathematical Society, Intertel.

Papers appearing in Solar Physics, Journal of the Royal Astronomical Society of Canada, Journal of the Barbados Astronomical Society, Meudon Solar Flare Proceedings (Meudon, France). Books: 'Fundamentals of Solar Physics', 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level', 'Astronomy & Astrophysics: Notes, Problems and Solutions', 'Modern Physics: Notes, Problems and Solutions'

B.A. degree in Astronomy; M.Phil. degree in Physics - specializing in solar physics.

Awards and Honors
Postgraduate research award- Barbados government; Studentship Award in Solar Physics - American Astronomical Society. Barbados Astronomical Society award for service (1977-91) as Journal editor.

Past/Present Clients
Caribbean Examinations Council (as advisor, examiner), Barbados Astronomical Society (as Journal Editor 1977-91), Trinidad & Tobago Astronomical Society (as consultant on courses, methods of instruction, and guest speaker).

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