Planck Units / Planck's Constant / Planck Scale

[4_4_4]

I was wondering if anyone who actually knows his or her stuff might be willing to have a bit of a dialogue about Planck Units, Planck's Constant, and/or the Planck Scale with a total layperson

Comments

[tmfkan64]

Humans tend to use units that are, well, human-sized. Regardless of the formal definitions, a meter is about half our height, a kilogram is a reasonable amount of weight to hold in one hand, and a second is a small amount of time to wait. However, once we start trying to formulate the laws of nature, we find that there are all sorts of arbitrary conversion factors. As the wikipedia article points out, Planck units are simply an attempt to simplify the equations by defining all of these constants to 1 and seeing what the resulting units are

[eracerhead]

It is about nature. It is the point where the inherent uncertainty of the dimension becomes larger than the thing we are trying to measure. This isn't really a stretch because we see this in other forms of dimension. For example, optical lenses are limited by diffraction which means it is impossible to resolve anything smaller than the wavelength of light. This isn't a problem with our technology, it is a physical limit inherent in nature.

Planck units, scale, time etc. are all related mathematically to this limit imposed by nature and are used as appropriate depending upon the type of measurement you are trying to make.

[saskiiaa]

What tmfkan64 and eracerhead say is exactly it.

Planck's constant does sort of play a role when it comes to quantization: for example, when it comes to light, the energy of a photon (particle of light) is E = h * f, where h is Planck's constant and f is frequency. The Planck's constant in this equation sort of introduces steps in the energy, which is where "light is a particle" comes from.

But what this means for a discrete or continuous universe, you can take that up with someone else because I'm not interested in / know nothing about all that theoretical stuff :P

[firstashore]

Is it a Planck's Unit that implies a discrete as opposed to continuous universe?

Pretty much. The Planck scale is an inherent property of the universe.

I recall either reading about or having someone tell me about how Planck's Constant--or maybe it was the Planck Unit or maybe the Planck Scale--(and here how do these three relate to one and other?) is the smallest interval we are able to measure. If this is so can anyone explain why?Because of the Uncertainty Principle, as explained above. As to how they relate to each other, Planck's Constant is a physical constant of the universe that provides the basis of the quantum. Planck Units are basically extensions of that theory into other physical quantities. For instance, Planck's Constant quantises the energy of a photon according to E = hf. You can also talk about the momentum of a photon - since its energy is quantised, its momentum is too. You can extend this into other physical and non-physical quantities. For example, the smallest unit of flux is called a fluxon. It's not an

[dopplerduck]

Still looking to talk?