Standard units

[Jacques]

I found this web page and I thinks it make a lot of sense !

I would like to have your comments about it.

We know that measurements are the backbone of science. A lot of work has been done to get the present self-coherent SI system of physical parameters, so why not choose SI as the foundation of a unifying theory? Because if the present science is not leading to unification, it means that something in its foundations is really wrong, and where else to start searching if not in its measuring units.

 

http://www.blazelabs.com/f-u-suconv.asp

 

Thanks

[labfreek]

I so agree! I only found it a few days ago and i think it rocks!! :D

[JustStuit]

Maybe the foundation, but I don't think it will progress the Unification theory - there will need to be some more break-throughs than that.

[timo]

I´d have questions regarding two of the three sentences quoted in the OP but since the author possibly isn´t among us I´ll strip it down to an answer to what I think is written in these sentences:

 

Physics doesn´t depend on whether you measure distances in meters, miles or diameters of a unit-apple. When you switch to a different unit-system, all equations remain (structurally) the same. Only the values (constants/variables/parameters/number of apple diameters) change.

[insane_alien]

(My f key seems to be sticky please excuse any lack of f's)Units don't matter to much or a unification theory. its just that you will have lots of strange numbers instead of nice numbers. but the whole theory will still work.

 

for example, measuring the distances between galaxies in S.I. units(meters) in the strictist sense isn't practical for astronomers since the numbers are large and horrible so they use lightyears and parsecs in their measurements and calculations. also when measuring tiny scales angstroms are used. these can both be replaced with exameters and nanometers with little problems. units are arbitrary anyway.

[JustStuit]

I would agree that if we all used the same units, the world would be a lot easier place to live, observe, and learn. Changing to all the same units, however, would effectuate chaos. It has been tried before, who knows if it will ever succeed.

[Jacques]

Have you read the link ?

Or just the quote ?

Take some time

For example unit of mass is [math]t^3/s^3[/math]

Basically it is saying that all units can be expressed in space and time units

[JustStuit]

One part was talking about the redundancy of the mole, but it is pretty useful. When you look for the mass/weight of an element it is much easier to use it than one atom. It also has unquie attributes, such as being 12 grams in carbon 12, I believe. It is easier to relate the mass/size/amount of atoms when using a reference. I do not know about photometric units so I don't know about the candela.

It also seems that with a little dimesional analysis you could derive all the units composed of s and t. This would save time but I still don't see how simplifing units could help unification any more than using a little more calculations in old units. Can you explain any other advantages? I'm a little confused.

[Jacques]

Thanks for taking the time to read the web page.

About the mole the point is that it is included in the SI even if it's not a unit but is a pure number. I agree with you that it is a very usefull number and that it simplify calculation.

 

Also it is not about converting angstrom to light-years both are unit of space.

 

Have you ever ask yourself What is mass ? Why [math]E=mc^2[/math] ?

You don't find it puzzling that you can express all quatity in term of space and time ???

This page don't say stop calculating with your standard equations. They are working fine.

[insane_alien]

the mole is extremely useful in chemistry and chemical engineering. If we didn't us the mole we would use a similar sized number but the mole works so well with gas laws and the such. avagadros number is a constant that is why it is unitless.

[Meir Achuz]

The idea that SI tries to block progress toward unification is correct, but this implementation is awkward. Elementary paricle physicists have been using "natural units" for over 50 years. The natural system has only one unit, which could be either distance, time, or energy. hbar and c are conversion constants used to change from one unit to another.

Saviour's choice of S and T as two independent units violates the space-time symmetry of special relativity. Doing so makes simplicity complicated.

If he doesn't unify space and time, how can he hope for unity?

[Jacques]

The natural system has only one unit, which could be either distance, time, or energy.

You give 3 kind of units ...?

Saviour's choice of S and T as two independent units violates the space-time symmetry of special relativity.

Can you explain ?

Thanks

[Meir Achuz]

Anyone of those 3 units could be chosen as the single unit for calculation.

As an example, if you choose cm as the fundamental unit, a lifetime may come out as 12 cm. If you want to know it in seconds you divide by the conversion constant 3\times 10^8 cm/sec to get 4\times 10^{-8} sec.

It's just like if you get an answer in inches and want cm, you multiply by 2.54.

[Meir Achuz]

In SR, there are four dimensions x,y,z,t. There is the same symmetry for rotating between x and t as there is between x and y. Space and time cannot be independent units, any more than x and y can.

[swansont]

In SR, there are four dimensions x,y,z,t. There is the same symmetry for rotating between x and t as there is between x and y. Space and time cannot be independent units, any more than x and y can.

 

 

ct is the relevant coordinate, but c is a constant, making t the variable. The units are fine.

[Jacques]

How do you conver energy to spacetime ?

How do you convert electric charge to spacetime ?

[Meir Achuz]

How do you conver energy to spacetime ?

How do you convert electric charge to spacetime ?

In QM, E and t are connected by Fourier trasform, so the product

E*t is inherently dimensionless. hbar is just a conversion constant used because E and 1/t are usually given in different units. Again, its just like inches and cm. If you use cm and I use inches, it looks lik we are taking about different things, but we are not.

 

Electric charge is dimensionless. alpha=e^2=1/137 in natural units.

If charge were not dimensionless, we could not talk about its strength, since that would depend on what units we were using.

Georgi (the inventor of SI) thoght electric charge ws s;pecial, but now we know it is the same thing as the "strong charge" and the "weak charge", all of which are dimensionless.

[Jacques]

E*t is inherently dimensionless

Then can we tell that the unit for E is 1/t , or E is the inverse of time ?

 

Electric charge is dimensionless. alpha=e^2=1/137 in natural units.

I don't follow I thaught that the charge units are coulombs ??

And I know about inch and cm, you can convert from one to the other by multiplying by 2.5, but inch and cm are the same kind of units thay are units of lenght. I convert apple to apple.

The conversion from time to space with ct, for me, look like converting apple to bananas.

[Meir Achuz]

The conversion constant for energy and time is hbar which has the units

Mev-sec. What I am trying to say that just as you can describe your height in meters or feet and can convert from one unit to the other, you can describe the lifetime of an unstble particle in MeV and use hbar if you want it in seconds. Using MeV for the lifetime can be more useful because it directly gives the width of the spectral line. I am not making this up. Natural units like this have been used for 50 years in elementary particle physics.

Do you want a reference on natural units?

[Jacques]

Do you want a reference on natural units?

Yes that would be appreciated !

Thanks

[Meir Achuz]

The most recent I know of is in "Classical Electromagnetism" by Franklin,

section 16.5. The book may be advanced, but that section should be readable for natural units

[s pepperchin]

Personnally I think that everything should be looked at in terms of energy. Rest energy, kenetic, potential. I think that knowing all the energies associated witha particle one could write a total energy distribution for a particle as well as a field equation for the movement of energy in a system. I know that it would make some physics more difficult but it might make unification easier.