Planck's constant and measurement

[Butch]

It occurs to me that a lot of math especially in QM would be easier to digest with a system of measurement based on Planck's constant... Is there such a system?

[Sensei]

Did you hear about Planck units?

https://en.wikipedia.org/wiki/Planck_units

But it's obsolete (it was made prior measurement of e.g. elementary charge in Millikan's oil drop experiment)

 

[Butch]

9 minutes ago, Sensei said:

Did you hear about Planck units?

https://en.wikipedia.org/wiki/Planck_units

But it's obsolete (it was made prior measurement of e.g. elementary charge in Millikan's oil drop experiment)

 

Hubble is not precise either, however when it is modified, we just modify our measurement... Why not for Planck?

[Sensei]

Physical constants are remeasured using newly developed techniques all the time, every couple of years.

What I said has nothing to do with the way Planck's constant is measured.

 

[swansont]

22 minutes ago, Butch said:

Hubble is not precise either, however when it is modified, we just modify our measurement... Why not for Planck?

Planck's constant is thought to be actually constant, and is measured to a far greater precision. 

Some quantum measurements are based onPlanck's constant. Spin and orbital angular momentum are typically expressed in units of hbar. (h/2π)

e.g. the electron is a spin 1/2 particle, meaning it has ± 1/2 hbar of angular momentum

[Tomanen]

Is it used (at present times) to measure distances smaller than planck?

[swansont]

Just now, Tomanen said:

Is it used (at present times) to measure distances smaller than planck?

Measurement anywhere close to the Planck length is currently not possible

[Butch]

I just mean a base system akin to gram meter second... Perhaps extrapolate from the energy of a photon with a wavelength equal to...?

On 3/28/2018 at 11:43 AM, swansont said:

the electron is a spin 1/2 particle, meaning it has ± 1/2 hbar of angular momentum

Yes, this is good! But qm does not have a system based on Planck's comparable to the gram meter second... Or am I mistaking? 

[Sensei]

25 minutes ago, Butch said:

Yes, this is good! But qm does not have a system based on Planck's comparable to the gram meter second... Or am I mistaking? 

In quantum physics we're using eV for energy, eV/c^2 for rest-mass, eV*s for angular momentum.

1 eV energy is equal to 1.6021766*10^-19 Joules. (or 1.602176565*10^-19 J in slightly older measurement).

ps. Did you mean kilogram-meter-second system? It's SI unit.

https://en.wikipedia.org/wiki/SI_base_unit

There is slightly older CGS, centimeter-gram-second system.

https://en.wikipedia.org/wiki/Centimetre–gram–second_system_of_units

 

 

Edited April 7, 2018 by Sensei

[Butch]

2 minutes ago, Sensei said:

In quantum physics we're using eV for energy, eV/c^2 for rest-mass, eV*s for angular momentum.

1 eV energy is equal to 1.6021766*10^-19 Joules.

However this is not based on Planck's constant and the math gets complex, makes things difficult to picture for us abstract thinkers.

That's ok though... If it were deemed important to the scientific community, it would already exist.

Thx all.

[swansont]

30 minutes ago, Sensei said:

In quantum physics we're using eV for energy, eV/c^2 for rest-mass, eV*s for angular momentum.

atomic mass units as well.

30 minutes ago, Butch said:

However this is not based on Planck's constant and the math gets complex, makes things difficult to picture for us abstract thinkers.

That's ok though... If it were deemed important to the scientific community, it would already exist.

Thx all.

Planck's constant is very small, and not necessarily convenient for calculations of things in QM.

[Strange]

59 minutes ago, Butch said:

a system based on Planck's comparable to the gram meter second.

Did you miss the link to Planck units earlier?

They are not widely used, I think, because the units are either much too small or too big. 

Edited April 7, 2018 by Strange

[Butch]

On 4/7/2018 at 5:47 PM, Strange said:

Did you miss the link to Planck units earlier?

They are not widely used, I think, because the units are either much too small or too big. 

To small for qm?

[swansont]

18 minutes ago, Butch said:

To small for qm?

Yes. A proton is about 10^20 times the size of the Planck length. The Planck time is more than 20 orders of magnitude smaller than anything we can measure.