Perfect physical constant

[FrankM]

What is a perfect physical science constant?

When I examine the NIST list of fundamental physical constants, they identify a group of constants that
they categorize as "universal".

Universal constants

Each of the constants have numeric values that are dependent upon SI base units or SI derived units. There
is not one unit in the list that is an actual invariable universal unit.

Units

Mathematics has defined a number of perfect constants, they are dimensionless and are truly universal.
In the physical sciences it is rare to find a dimensionless constant, at least there are none defined in the
SI list of constants. The next best thing to a perfect physical science constant is one that would be defined
by only one unit, but that unit should be something that is an actual universal value.

Are there any such physical science constants?

[Tormod]

Originally posted by: FrankM
What is a perfect physical science constant?

Good question. It depends on what "perfect" means, but if it is to include the "dimensionless" requirement the it becomes difficult as physics deals with real world stuff while the constants of pure math often deals with things that are not "real" in any physical sense.

Frank, to aid in this discussion could you post some examples of perfect mathematical constants...my knowledge is a bit lacking in that area.

Each of the constants have numeric values that are dependent upon SI base units or SI derived units. There is not one unit in the list that is an actual invariable universal unit.

I don't understand. What do you mean? All of them are invariable AFAIK. What would have to vary is the SI base unit, which would mean the formulae for the constants would have to change. The Planck length is a fixed value, the values we use to explain it are not. There is a big difference.

Now if you say that a mathematical constant are things like Phi, Pi, the Fibonnaci sequence etc then these also apply in the physical realm, of course.

However, some of the physical constants are related to things like the expansion of the universe (the hubble constant and the alpha constant), properties of it (speed of light in a vacuum, gravitational constant) and while these are considered constants they might change over the age of the universe because of the way they are calculated.

John Barrow discusses this in his book, "The Constants of Nature".
Review: http://www.hypography.com/article.cfm?id=32630

[Aki]

I think he's talking about the SI units as in metres, grams and seconds....right?

Well if you're asking about that, then I can answer you, I just have to look the explanation up in my physics textbook

[Tormod]

No, I think Frank refers to something less related to human beins. The SI units are created by people (ie, meters, grams, seconds). He is asking for true physical contants which are not "invented" by human beings but rather discovered.

Frank, wouldn't the frequencies of the electromagnetic spectrum be constants? Waves could change, but the frequencies themselves are always what they are.

[alexander]

Tormod said:

Now if you say that a mathematical constant are things like Phi, Pi, the Fibonnaci sequence etc then these also apply in the physical realm, of course.

Those numbers seem to come from our natures sequences, so i can see how they can be physical constants, but i still argue some of them like the fibonacci sequence. How can it be a true physical sequence if not all things that it is supposed to represent follow it; for example Pi applies to every circle and phi occurs in every decagon inscribed into one, but fibonachi sequence does not apply to all spirals or all squares, not to say that fibonacci wasnt a great mathematician, who dicovered a sequence that some of nature seems to follow?
Other constants:
Euler-Mascheroni constant - limits difference between all harmonic series and natural logarithms
Feigenbaum constant - every chaotic system of all one-dimensional maps displaying a single hump will bifurcate at the same rate
and there are others see: http://en.wikipedia.org/wiki/Mathematical_constant

[Tormod]

I didn't mean to belittle mathematicians (I'm a fan of mathematics!) but was trying to find out what is required for something to be a "true" universal physical constant.

[lindagarrette]

How about the "fine structure constant?" "There is a most profound and beautiful question associated with the observed coupling constant, e the amplitude for a real electron to emit or absorb a real photon. It is a simple number that has been experimentally determined to be close to -0.08542455. (My physicist friends won't recognize this number, because they like to remember it as the inverse of its square: about 137.03597 with about an uncertainty of about 2 in the last decimal place. It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it.) Immediately you would like to know where this number for a coupling comes from: is it related to pi or perhaps to the base of natural logarithms? Nobody knows. It's one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the "hand of God" wrote that number, and "we don't know how He pushed his pencil." We know what kind of a dance to do experimentally to measure this number very accurately, but we don't know what kind of dance to do on the computer to make this number come out, without putting it in secretly! " R.P. Feynman

[Tormod]

Very good example, Linda. I did mention it above (alpha) but your description is very good.

[Freethinker]

Originally posted by: FrankM
What is a perfect physical science constant?

When I examine the NIST list of fundamental physical constants, they identify a group of constants that
they categorize as "universal".

Each of the constants have numeric values that are dependent upon SI base units or SI derived units. There
is not one unit in the list that is an actual invariable universal unit.

Are there any such physical science constants?

As Tormod has suggested, are you talking about CONSTANTS from the UNITS standpoint? It would seem that there are many "fundamental physical constants" from the standpoint that any entity that would measure it anywhere in the universe would come up with the same measurment, but would probably use a different set of symbolic units to represent it. The speed of light in a vacuum would be the speed of light in a vacuum. But they would not use meters to measure it. Such as the US might use FEET instead. Yet the speed would be the same even though it is represented by different numbers.

[FrankM]

Originally posted by: Tormod
No, I think Frank refers to something less related to human beins. The SI units are created by people
(ie, meters, grams, seconds). He is asking for true physical contants which are not "invented" by human
beings but rather discovered.

Frank, wouldn't the frequencies of the electromagnetic spectrum be constants? Waves could change,
but the frequencies themselves are always what they are.

Yes, the SI constants are created by humans using units (meters, grams, seconds). It is easy to
find a host of mathematical constants as they are invariably dimensionless, like Pi, a ratio.

Frequencies are not constants, the numeric value is dependent upon the definition of the time segment.
The physical length of a wavelength is invariable, but the numeric value we apply to it changes depending
upon what units we are using to describe a length. If I cut an iridium bar to the length of the wavelength
that results from the Larmor precession of neutral hydrogen, it would represent 1 wavelength. If I
want to describe that length in metric it would be 21.1061...+ cm long, or 8.3097...+ inches in English
units.

The frequency would be 1420.4 MHz whether I calculate the frequency using the speed of light in metric
or English units, because the length unit cancels. If I changed the duration of the time unit to something
different than the second the numeric value of frequency would change, but the wavelength represented
by the iridim bar will always be the same, "a constant".

Scientists discovered the wavelength emission from neutral hydrogen, the length is constant. Why
isn't that wavelength used as a constant?