Expert: Tom Whiting - 5/10/2004

Question
Tom,Hi,I read your answer, thank you,I understand about Polaris,I just wish I could see more stars at night.What I wanted to follw-up on,maybe is out of your area. My original question was about the term "order of magnitude" I have heard it used in reference to high power lasers, nuclear explosions,(atomic theory),and stars.But as I said, I understood "order of magnitude" to signify an increase or decrease by powers of 10,100,1000.etc., so an increase of 2 orders of magnitude would be a multiplying of 100, or 10 to the power of 2. Are you familiar with this type of notation?   Thanks,Mike  

Answer
Mike,
Not familar with nuclear explosions or lasers, but I
believe your quotation deals with something like the earthquake magnitude (strength) scale,
where a Richter 6.0 is 10 times stronger than a 5.0,
and a 7.0 is 100 times stronger than a 5.0,
and an 8.0 is 1000 times stronger than a 5.0,
and a 9.0 would be 10,000 times stronger than a 5.0...
I believe that is the way it works, on an "order of
magnitude" (strength)...scale, starting with a base of 10.

In astronomy however, the word magnitude is strictly a brightness measurement definition, not related to strength,  power, or even size, as like those other catagories....earthquakes and such.

So I don't believe your 10, 100, 1000 fits anywhere
into anything astronomical.  Or at least, I can't think
of anything astronomical where that system would apply.
(Even power output of a star only goes up as the square
of the surface area of a sphere), and increasing absolute
temperature....to the 4th power of T, if you increase surface temperature.)

Note however, that brightness difference figures ARE an order of magnitude; always raised to another whole numbered power, but the *base* number is 2.5 for stellar brightnesses, (or more precisely 2.512), not ten, like the
earthquake scale.

Also, I've read that nuclear explosions do not follow either, relative to the damage caused;  twice the explosion does not mean 10 times the damage.... or even twice the damage.

I've read that-
That is why we (USA) got away from those huge 500 megaton
nuclear detonations, and back to much smaller yields
as the percent damage efficiency of the smaller yields per
pound of enriched material, is much higher.  They found
that it is just 'overkill' using the massive yields like
the Bikini atoll test.
FWIW,
Tom Whiting, Major, USAFR (retired Nam pilot)
Erie, PA

FOLLOW UP
Even researching the Richter scale on Google, they still
only speak of a logarithmic scale based on the number 10...
See
http://www.geo.mtu.edu/UPSeis/intensity.html
So they don't even use the phrase "order of magnitude"
but I'm sure that is what they mean, because ground motion
goes up 10 times for each whole number change in
Richter number, for earthquakes.
Clear Skies,
Tom Whiting