Planck Definition and 381 Threads

Can anyone help me with this question? Thanx Calculate the frequency of the photon emitted when an electron in an atom changes from (-2.42e-19 joules) to (-21.76e-19 joules). I know that I'm going to use E=hf and h=6.63e-34. I'm not sure what I do with the 2 energy levels, do i...

Is there an upper limit on temperature? Is the 'Planck temperature' the upper limt?

How does instantanious action at a distance reconcile itself with Planck Time and the assumption that nothing can happen in this minuscule timescale? Does the transition from cause to effect not have a Planck time after the cause and before the effect? Could one describe a unit of Planck Time...

I have been reading http://en.wikipedia.org/wiki/Planck_units Why do they use Newton's universal gravitational constant, when that is a low gravity approximation and general relativity is what it used to work things out?

Can someone explain what are they: For egs. What is Planck time, PLanck length, Planck particle etc.

I know that Planck Time is the amount of time it takes light to cross Planck Length, but how did they figure out Planck Length? What are all the Planck units, how large are they, and how were they figured out?

Hello, First time at this site really good. So on to the point.How can i calculate the Planck constant so i can compare it with the already known number for it??its for a physics test and i can't find out ... Thnx in advance

If I understand well, Planck units are fundamental in the sense that they don't depend on any arbitrary choice of measurement scale, but they emerge directly from the laws of physics. For Planck length and Planck time, this seems to fit with the widespread belief that they may well also be...

In 1981 Dimopoulous, Raby and Wilczek, considering SUSY GUT, remark that In the ordinary theory M \approx 10^{15} GeV and ... so the supersymmetric M \approx 10^{18} GeV. This is the same ordeor of magnitude as the Planck mass, hinting perhaps a larger unification including gravity as well...

I'm taking a course on astrophysics, and at this time I get the astrophysics of stars. In this section, I have to use the Planck radiation formula, but I have got it for the frecuency of radiation. What's the one for wavelenght? I have found one but I tried to reconstruct the one for frecuencies...

Planck Photon Power... What is the 'Power' equation for a single 'Planck Energy Photon'? What is the numerical value for the 'Planck Photon Power' solution? How does this 'Planck Photon Power' compare with the current power consumption of the world (at any instantaneous moment)?

Ok so I understand how we derive Planck Length using the natural constants G,h, and c. However, how do we know this indeed represents the smallest possible length an object in the universe? Or does Planck length just represent the smallest possible length under which gravity is still influential?

\gamma (E_1) \rightarrow e^+ + e^- \; \; \; E_1 = 2 m_e c^2 \gamma (E_2) \rightarrow p^+ + p^- \; \; \; E_2 = 2 m_p c^2 \gamma_p (E_3) \rightarrow m_p^+ + m_p^- \; \; \; E_3 = 2 c^2 \sqrt{\frac{\hbar c}{G}} E_n - photon energy \gamma_p - Planck Photon m_p^+ - Planck mass (matter) m_p^-...

I was reading about the Planck units, and they said that Planck came up with them before his quantum theory of blackbady radiation, and before the constant h had been discovered. They said it's unclear how he found these units. This seems pretty weird to me. How did he come up with these...

Over in SPR John Baez asked what is the value of the cosmological constant (Lambda) expressed in Planck units. I posted a reply earlier today, but it contained a mistake ---what I posted on SPR around 10AM today--- I think the current estimate of Lambda in Planck units is 4.0 E-123...

The wavefunction for a hypothetical quantum box of size Planck length (L), when inverted through L, models the universe with this lower bound required by quantum gravitational constraints. The initial quantum box solutions are given by: \phi_n=\sqrt(2/L)\\sin(n \pi x/L) However...

"Planck scale Lorentz-symmetry test theories" Amelino-Camelia new paper by Giovanni A-C http://arxiv.org/abs/astro-ph/0410076

As I understand the inflationary cosmology states that at around 10^-35 seconds to 10^-32 seconds after the Big Bang all matter was created as what Alan Guth called the "ultimate free lunch". However, it is said that at 10^-43, the so-called Planck time, was when gravity became separated from...

we could have a thread for talking about Planck units and getting accustomed to them Planck units are basic and everpresent in QG so it helps to develop a feel for them even tho LQG is itself based on a continuum the underlying spacetime is a continuum and it is only the geometric...

Almost a hundred years ago leading scientists were discussing the fact that if the most elemental constituents of mass all moved at the invariable speed of light, the phenomena of relativity would be a natural consequence. This, of course, required the classical space-time. Has anyone ever...

Is the Planck length a commonly accepted theory or is it controversial in any way?

O.k., so I'm reading this article by victor stenger called Fitting the Bible to the Data where he is criticizing this guy Schroeder's attempt to fit the bible creation story in with big bang cosmology. he chooses the time of quark confinement, or 10^-4 seconds to start. this is the part that...

april 2004 paper http://arxiv.org/abs/hep-ph/0404014 Decoherence has the potential to explain all existing neutrino data including LSND results, without enlarging the neutrino sector. This particular form of CPT violation can preserve the equality of masses and mixing angles between...

Can anyone please shed some light on how the Planck length or Planck time were found? I understand why they have to exist, but what predicts their values? Is it even a prediction or can we actually calculate the Plank length with experiment? Thanks,

Here is a great paper, obviously overlooked here, but not at (superstringtheory.com):wink: Anyway it has some major consequences for new thinking, like asking the above question in the post title. It is definately a important paper, and although it will no doubt stir the imagination in...

sorry I am not sure if this is the correct pigeon hole to use. planck dimentions are well known but why are they the smalest possible units? i think it was wheeler that used Planck units in his quantum foam theory, would we have this theory without planck units?

I have found references to a book that is either "to appear" or has already been published by Cambridge University Press. The book is Physics meets Philosophy at the Planck scale edited by C. Callender and N. Huggett this is apparently a collection of essays by philosophers and...

an integral of the Planck radiation law-- 2.701kT this is classical (vintage 1905) physics---kind of cute Planck's radiation law (one of the things that kicked off QM) can be written to show the numbers of photons at each frequency--in effect, a bar graph showing how the population of...

If somebody wants to know what Planck units are, how do you go about explaining? Can you make them intuitive without too much technical detail? What would your approach to describing natural units to a non-scientist (possibly a little vague as to what hbar and G are)? I want to know any...

this is not to argue or persuade but just to share a calculation. no answer needed unless you particularly like something about it. several websites, eg. NedWright's Cosmology tutorial have formulas for things like the critical density and the estimate that real density is very close to...