# I Would we observe a changing Planck's constant?

1. Apr 17, 2017

### sgphysics

If Planck's constant is changing, how slowly would it need to change before we could observe that something was going on? And if changes were discrete, how large quanta would it take? (for us to observe the jumps)

And a follow-up question: If there was another universe here, running a different value of h(bar), would we observe it? Tunneling between them possible?

2. Apr 17, 2017

### Staff: Mentor

These questions can't be answered without some sort of theoretical model. AFAIK nobody has tried to construct a model in which Planck's constant is changing.

Same response: we don't have a model to work with, so there is no way to answer the questions.

3. Apr 17, 2017

### Meir Achuz

Planck's constant is just a number that is determined only by our definition of the units sec and eV.
What do you mean by changing Planck's constant?
If an alien has the same Planck's constant as we do, he is not an alien.

4. Apr 17, 2017

### Meir Achuz

... or she.

5. Apr 18, 2017

### sgphysics

Well, actually the model I had in mind was the Schrödinger equation. For a simple system one could easily explore altered solutions from variations in h(bar). So if a universe existed with a different h(bar), perhaps running the same E and V as in our universe, would that be possible? - presuming that everything is described by the SE.

6. Apr 18, 2017

### Staff: Mentor

That equation doesn't allow Planck's constant to change.

How? The equation doesn't allow $\hbar$ to vary. $\hbar$ is just a unit conversion factor in Schrodinger's equation; you can just as easily adopt units in which $\hbar = 1$ and it doesn't even appear.

7. Apr 18, 2017

### dextercioby

PF is not a place to speculate on ”What would happen if...?”. Actually, the speed of light in vacuum was fixed to 299792458 m/s in 1983. In 2018, the plan of BIPM is to sanctify h by rendering its normal experimental uncertainty to 0, just like they did for c in 1983.

8. Apr 19, 2017

### sgphysics

I do not share your view on physics, but I shall respect that any forum may decide their own limits. It's not speculation when something can be answered from understanding of math. The number of decimals obtained for c or h measurement is certainly bright engineering, but off-topic. So also the trivial fact that h-value is unit dependent,

9. Apr 19, 2017