Re: [Phys-L] Halfway point ???

["Donald Polvani" <dgpolvani@verizon.net>]

I used:

range of atmospheric dust particle "sizes" as 0.001 to 30 microns
mean radius of earth = r_e = 6371 km
mean "radius" of proton = r_p = 0.86 fm

Then arithmetic mean of r_e and r_p is about 3200 m
Geometric mean is about 2 microns
Harmonic mean is about 2 fm

So, thinking of the halfway point as the geometric mean is well in agreement with the range of atmospheric dust particle "sizes".

Don

Dr. Donald Polvani
Adjunct Faculty, Physics (Retired)
Anne Arundel Community College
Arnold, MD 21012

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@www.phys-l.org] On Behalf Of John Denker
Sent: Friday, April 03, 2015 9:28 AM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] Halfway point ???

On 04/03/2015 05:55 AM, Bob Sciamanda wrote:
> Can anyone discern a “thought process” which makes this statement meaningful ?

1) Evidently "halfway" means geometric average.

2) Suppose you are building a scale model.

An X particle with an extra proton stuck on the side is represented, at scale, by the planet earth with an extra X particle stuck on the side.

When I do the math, X is somewhat too big to qualify as a "dust" particle, but the general idea is not completely crazy.

============

More generally, it is an amusing grade-school exercise to build a scale model of the solar system.  If the earth is represented by a ping-pong ball, how big is the moon, and how far away?  How big is the sun, and how far away?

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