Magnitudes

[kidlands]

If something is 20,000 times more than something else ie mass or magnetic strength how do you work out this as a magnitude?

So if I said A is 10 magnitudes larger than B and I know A is 20,000 times larger than B how do I work out A is larger than B by X magnitudes?

or if I know both figures ie A is 20,000 and B is 2000 how do you work out how many magnitudes A is more than B.

Hope that make sense?

steve

[brianb]

"Magnitude" when applied to a star is a very precise term. A star with a numeric magnitude one less than another is 2.512 times as bright. A mag. 9.0 star is 1/100th the brightness of a mag. 4.0 star.

When used otherwise, we generally mean "an order of magnitude" to mean adding or subtracting a zero .... so e.g. 64 is the same order of magnitude as 100 but about an order of magnitude larger than 10 or smaller than 1000. Very imprecise ...

[kidlands]

'in order of magnitude' is what I think my examples need to be explained in.

If A is 317 and B is 17 how do I work out what order of magnitude is A more than B?

and if something is 20,000 times bigger, what order of magnitude is it larger?

I feel my scientific calculater warming up, does it involve Logarithms?

steve

[kidlands]

FAO forum admin I think this might be better in Physics space science and theories section?

[brianb]

I feel my scientific calculater warming up, does it involve Logarithms?

Take the logarithm (base 10) and round to the nearest number.

20,000 is 4 orders of magnitude. 317/17 is (a bit more than) one order of magnitude.