# What is Planck: Definition and 388 Discussions

Max Karl Ernst Ludwig Planck, (German: [maks ˈplaŋk] (listen); English: ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918.Planck made many substantial contributions to theoretical physics, but his fame as a physicist rests primarily on his role as the originator of quantum theory, which revolutionized human understanding of atomic and subatomic processes. In 1948, the German scientific institution Kaiser Wilhelm Society (of which Planck was twice president) was renamed Max Planck Society (MPS). The MPS now includes 83 institutions representing a wide range of scientific directions.

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1. ### B Can the force of gravity overcome the Planck force?

Can the force of gravity overcome the Planck force? I remember that a long time ago I read that in the universe the Planck force was the maximum force that could be reached. But when Sagittarius A and the black hole at the center of the Andomeda galaxy approach, I have made the calculation that...
2. ### How does one calculate the number of photons striking a surface per second?

I am more so stuck on where to start with this problem. I know dividing the photons per second by the area gets me the photon per area, but I am not sure how the distance is related to this part of the problem. If anyone can help, thank you.
3. ### A Is M_{Pl} the Planck mass or the reduced Planck mass?

What is the value of M_{Pl} used in the Planck (CMB) collaboration's observation papers, such as the one referenced in this link: https://arxiv.org/pdf/1807.06211.pdf. Specifically, I am wondering if it refers to the Planck mass or the reduced Planck mass?
4. ### I Deriving the Planck relation

How do one derive the relation E=hf?
5. ### I Why are Planck units considered fundamental?

Why are Planck units considered fundamental ? After all, there is a square root in their expressions. And the value of the Planck mass is 20 orders of magnitude greater than the average values of elementary particles. $$m_{pl}=\sqrt{\frac{1}{2\pi}\cdot \frac{hc}{G}}$$ The order of the value of...
6. ### I Between a Zeptometer and the Planck length

What exists between approximately 1 X 10 E-21 meters (preon length?) and the Planck Length of 1.6 X 10 E-35 meters?
7. ### B Is the highest frequency possible the inverse of Planck time?

Is the highest frequency possible the inverse of Planck time? Separate or connected question, what's the highest frequency achievable practically today?
8. ### B Planck Length 1 Detector? Emitter?

Do we have the ability to detect the gamma ray of Planck Length 1? Is there any known phenomenon, natural or man-made, that could emit on Channel 1? How dangerous to man and machine would Channel 1 be / at what density (is that the right term?) would it become dangerous? Would there be any...
9. ### Did Planck think the light emitted from black bodies to be quantised?

However I need to know whether Planck also had to assume that emitted light was quantised to make his model work? I need to teach this topic in the context of how different experiments shaped our understanding of the light model. I have found 2 sources which seem to contradict each other:(...
10. ### A Exploring Planck 2015 Results on Power Law Potential Models

I am reading Planck 2015 results. In particular, I focused on "Power law potentials" subsection. The issues I have are 1. I do not understand why the validity of the model can be determined by the value of the ##B## mode. 2. Why the ##B## mode values ##\ln B = −11.6## and ##\ln B = −23.3## for...
11. ### B Reduced Planck Constant vs Dark Matter?

Is the Reduced Planck Constant the minimum frequently/movement/spin matter can have to exist? So if a matter were to spin lower than 1.054 571 817... x 10-34 J s, it when cease to exist? Or would matter falling below the Reduced Planck Constant by classified as Dark Matter? I heard that Higgs...
12. ### B Is The Planck Length the smallest length possible?

So, I was wondering is the Planck length the smallest length possible for measurement in physics? Please give as much details as to why or why not.
13. ### Photoelectric Effect Classical Breakdown

So I'm kind of confused about how to interpret the question and the idea of there being a small enough ##\tau## for the classical picture to break down. I started with the max KE eqn: ##KE_{max} = E_{incoming} - \phi## I suppose ##E_{incoming}## is the power (W) times time and that is also...
14. ### B Dark Matter -- Is it possible that Dark Matter has Planck mass and Spin two?

Is it possible that dark matter has Planckmass and Spin two?
15. ### I To measure a Planck length would require a black-hole photon?

I was viewing this video in which the narrator says that the energy of a photon that could discern a Planck length would require a photon of such high energy that it would be a de factor black hole. Is this accurate?
16. ### B What does the unit "Js" of the Planck constant mean?

what means unit j.s in plank constant As Planck's constant is the smallest unit of energy so what this unit j.s
17. ### Can We Travel Close to the Speed of Light?

Hello! My kid asks if this is theoretical idea is correct and I just don't know this stuff very well: It is impossible to travel at light speed but not impossible to travel just below. So the highest theoretical speed should be: "The distance light has traveled in one second" minus "One Planck...
18. ### I Necessity of Quantum Gravity given Planck scales for nuclear physics

In the solutions (page 6, points ii) and iii)), https://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2013/assignments/MIT8_04S13_ps1_sol.pdf, it is mentioned that given that the Planck mass is about 20 orders of magnitude larger than a proton and that the Planck length is about 20...
19. ### I Why does nothing happen at the Planck mass?

It appears as clear to me that the Planck mass has a fundamental role, since for it the deBroglie wavelength and the Schwarzschild radius are equal. So it is some borderline between elementary particles and black holes. What intrigues me, however, is that the universe is mostly made up of...
20. ### A Zero-point Energy Contribution Below the Planck energy cutoff

Is it possible to determine the amount of zero-point energy contributed by all fields below the Planck energy cutoff?
21. ### B Is There a Connection Between Planck Length and Planck Time in Relativity?

If Planck length is 10^-35 of a meter and Planck time is 10^-43 of a second, doesn't that mean that as the relative speed gets closer to the speed of light and time acceleration and length contraction are happening, they are happening at a different rate, since length contraction has to reach...
22. ### I Comparing Planck's Mass, Length, Time and Energy

Sean Carroll gives the Planck's set of four dimensioned quantities: Planck's mass, length, time and energy. I wanted to compare them with actual things.\begin{align} m_p=\sqrt{\frac{\hbar c}{G}}&=2.18\times{10}^{-8}\rm{kg}&\rm{{10}^{7}\ E. coli}\phantom {100000000000000000000}&\phantom...
23. ### I Planck Length & Singularity: Point or Sphere?

Since Planck length is a distance unit of space-time which cannot be further subdivided, would that not imply that an electron, or singularity, or any other point particle cannot actually be a “point”, but must rather be a spherical volume with a Planck length diameter? i realize this may well...
24. ### Does Planck's relation apply to radio waves?

I have some doubts about whether Planck's relation (E=hf) applies to radio waves. This has been bugging me because trying to apply Planck's relation to radio frequency results in some inconsistencies that I've been unable to resolve. BTW, I have no physics training, so please go easy on me...
25. ### B Schwarzschild radius of an object is smaller than Planck length

I had this idea when some people said that LHC can produce black hole. Based on the calculation of Schwarzschild Radius, any mass than 9.375×10^7 kg have a Schwarzschild radius smaller than the plank length. Particles inside LHC or other particle accelerator have clearly radii smaller than that...
26. ### B A question about the Planck Epoch

During the Planck Epoch was the universe in a pure state prior to the Grand unification epoch?
27. ### B Can a wavelength be smaller than a Planck length?

According to this article https://physics.stackexchange.com/questions/321229/why-dont-we-have-proton-neutron-microscopes, they seem to hint that heavier objects have a shorter wavelengths and give better resolution. If I kept increasing the mass of a particle and kept it's speed at .9c would I...
28. ### I Relationship between Planck Distribution and Quantization of Energy

I came to understand that Planck Distribution is necessary to explain UV catastrophe. With that necesity in the background, the distribution equation eventually suggests that the energy emitted by black body has discret values. But I wonder how that's related to E=nhv. I understand that "n" also...
29. ### I Why don't strings have a Planck mass?

I understand that strings have a size of roughly the Planck length ##l_P## of ##10^{-35}## m. If that is the case then one would expect that their mass would be roughly the Planck mass which is an enormous ##10^{19}## GeV. (Strings that have small spins, like standard model particles, are...
30. ### I Planck had 2 definitions of energy in 1900, how?

So, I was looking into Einstein's 1907 paper where he derived the specific heat of solids using quantum mechanics and I found that Einstein just took the derivative of Planck's equation from 1900 for the average energy, U, as a function of time (and multiplied it by 3N for the three dimensions)...
31. ### B Planck Length: Upper Limit on Photon Frequency & Momentum

Is it known how much momentum a photon possesses if it's wavelength is at the Planck length, and what happens if it's momentum is somehow increased from that?
32. ### I Is it possible for something to be smaller than a Planck length?

After watching a youtube video 2 years ago, the video said the smallest thing known is at Planck length, but could there be something smaller than Planck length

I am quite confused, as I start this question. I can easily find the following when searching up Planck's law: However, this is not u. My prof is quite unclear and sometimes chooses his own variables as he sees fit, so i am not sure if this would be equivalent to what he is looking for u(λ)dλ...
34. ### A On the Planck Blackbody Function

The graph of the Planck blackbody function has an interesting feature:## \\ ## ## \rho_o=\frac{\int\limits_{0}^{\lambda_{max}} L_{BB}(\lambda,T) \, d \lambda}{\int\limits_{0}^{+\infty} L_{BB}(\lambda, T) \, d \lambda} \approx .2500 ##, where ## \lambda_{max} ##, in an exact derivation of...
35. ### I The Planck length and string theory

String theorists frame much of their studies in the context of Planck length. The theories are meant to fold together QM and general relativity. The equation for Planck length includes the gravitational constant, G. It seems to me the theorists are assuming the gravitational laws extend to...
36. ### B Significance of the Planck Particle

Taken from the Wikipedia page: Is there something significant about the physics of the Planck Particle or its properties? If so, then what is the significance? If there's nothing especially significant about the Planck Particle, then you can just say "No" and I will consider the matter closed...
37. ### Thermal Physics: Photon Statistics on Bose Particles

Homework Statement [/B] I have solve the rest of this problem pretty easily and see no problems with working with Indistinguishable particles, Distinguishable particles, fermions and Bosons. Part c has me very confused though about what it is even asking. Suppose a system with equally spaced...
38. ### I Wavelength approaching the Planck length

If I heat up an object,the object emits a electromagnetic wave with a shorter and shorter wavelength. But if I heat an object up to Planck temperature, and making the EM wave that it emits has a wavelength of Planck distance,what will happen when I heat it up even more? Will the wavelength...
39. ### How many Planck lengths are there in a parsec?

[Mentor's note: moved to GD because this is a thread about Alexa, not parsecs or Planck lengths] I know it's a strange question. Here is Alexa's answer: https://drive.google.com/open?id=1hXYFT_zBnFy-N0BotiTSDL8_S6nHK3ns
40. ### I Does the Planck Length Experience Length Contraction at High Speeds?

Imagine I had a ruler 1 Planck length long, I then send it on a rocket close to the speed of light, does its length contract? It seems to my simple intuition, relativity would say yes and Qm would say no. Is there a simple solution to this ?
41. ### "Ant Man" and the Planck scale

Ant-Man can shrink to the subatomic quantum realm where space and time cease to have meaning. Can he reaches inside the Planck scale? I wanted to use the words "below" or "above" the Planck scale. But when describing inside it.. do you use "below" or "above" the Planck scale to describe inside...
42. ### I Could the original size of the Universe be the Planck length

If you guys haven’t noticed through my posts so far is that I am interested in the Big Bang. I am considering the concept of the Planck length, but I may have some confusion. How did Space time start? Did the universe start from nothing and created units of spacetime? Could the original size...
43. ### I Planck Emission Spectrum

Hello Everyone, I have some thoughts about Planck's law. The graph describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. I think the absorption (or absorbance?) spectrum of an ideal blackbody should be a horizontal...
44. ### B Planck level effects of virtual particles

Knowing that virtual particles appear and disappear at the Planck length, what is the effect of the annihilation on space-time where the particles used to be?
45. ### A Planck 2015 CMB temperature individual pixel variance

Hi, I'm hoping someone can point me in the right direction please. I'm using the Planck 2015 CMB temperature (intensity) SMICA pipeline maps (Nside = 2048) and am trying to determine the temperature variance of each individual pixel. Variance and hit-count were provided with the 2013 CMB maps...
46. ### I Are Planck Units Merely a Pop-Science Fad?

As a physics undergrad, a set of natural units is nothing strange to me, we use them all the time. Having said this, I've never used Planck units. Does any area of research use them on a typical day in the office? There also seems to be this idea that I hear from time to time, perpetuated by...
47. ### I Could Planck Stars Explain Black Hole Bounce and Resolve Physics Paradoxes?

https://arxiv.org/pdf/1708.01789.pdf In line whit LQG which renders time(Tomita time) to evaluated differently. Would it be possible for a bounce scenario in Blackhole. This is the update from the old paper of Planck Star http://arxiv.org/abs/1401.6562 . -- It is something to with how time...
48. A

### B Planck-Einstein relation and the Photoelectric Effect

Hi everyone, I just have some confusion regarding Planck's and Einstein's equation. The following is an explanation of the photoelectric effect using Einsteins theory: Light is composed of photons. Each photon has energy hf and mass hf/c^2. When ultraviolet photons are brought to rest by zinc...
49. ### B Question About Planck Scale Unit

Can someone clarify this for me. Is it the case that Planck scale unit is the smallest unit of measurement that can can observe/make, but not the smallest unit of measurement that exists? If so, is there some name for that which is smaller? Is there some fundamental measuring unit that...
50. ### B Planck Length and Lorentz Contraction

I've heard that Planck length is the smallest length ever! but if something that his length is equal to Planck length and moving by speed dv which is infinitesimal change in speed or higher than that , then according to special relativity his length must be equal to L'=L \sqrt1-v^2/c^2 which...