Planck mass; time; length derived out of air?

In summary, the Planck mass, Planck time, and Planck length were derived as algebraic combinations of three measured constants of nature - the speed of light, Planck's constant, and Newton's constant of gravity. These combinations were discovered through experiments and measurements of the constants. Planck's constant, h, was derived in 1900 by Max Planck as a way to explain the black body radiation spectrum. Experiments, such as using Josephson junctions, are used to determine the value of h to a high accuracy. The concept of h and its value are both important in understanding the nature of light and its behavior in different systems.
  • #1
Chaos' lil bro Order
683
2
Greetings,

Anyone know how the Planck mass, Planck time, and Planck length were derived in the first place? Please cite experiments or mathematics to support your comment as I'd like to intimately understand this, not just from a metaphorical standpoint.

Thanks a bunch,

Chaos' lil bro.
 
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  • #2
Chaos' lil bro Order said:
Greetings,

Anyone know how the Planck mass, Planck time, and Planck length were derived in the first place? Please cite experiments or mathematics to support your comment as I'd like to intimately understand this, not just from a metaphorical standpoint.

Thanks a bunch,

Chaos' lil bro.

The http://en.wikipedia.org/wiki/Planck_length" are algebraic combinations of three measured constants of nature, the speed of light, c, Planck's constant, h, and Newton's constant of gravity, G. Those constants have been measured many many times.
 
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  • #3
They are the only possible algebraic combinations of those 3 constants which obey dimensional analysis.

Daniel.
 
  • #4
Ok, then how was 'h' derived?

Ok, C, G, h.

Then how was Planck's constant 'h' derived? If possible please site an experiment, observation, or derivation since to help me understand the meaning beyond a google cut and paste.

Thanks.
 
  • #5
Do you mean the concept of h or the value of h?

The concept of h came from problems in thermdynamics/electromagnetism around 1900 which predicted that the black body radiation spectrum for a cavity (like a heated oven) should have infinite energy. In order to solve this Max Planck realized you could get the right spectrum if you assumed light was made up a particles which had energy hf, where f was their frequency and h a constant. He didn't initially agree with his own work, but the results were undeniable.

To get the value of h, experiments are done. I seem to remember reading a few years ago that Josephson junctions are excellent for determining h to a very high accuracy, but solid state physics isn't my thing and I can't be sure I'm remembering that correctly.
 
  • #6
Alpha, great post!

One little question:
Are you saying that the oven contains infinite energy because there can be infinite modes within it? As in a curve that extends towards but never reaches the x line?
 

Related to Planck mass; time; length derived out of air?

1. What is the Planck mass?

The Planck mass is a fundamental unit of mass in the Planck units system, named after physicist Max Planck. It is the mass of a hypothetical particle known as the Planck particle, and is equivalent to approximately 2.1765 x 10^-8 kilograms.

2. How is the Planck mass derived?

The Planck mass is derived by combining the fundamental constants of nature, including the speed of light, Planck's constant, and the gravitational constant. It is based on the theory of quantum mechanics and the theory of general relativity.

3. What is the significance of the Planck mass?

The Planck mass is significant because it represents the scale at which quantum effects and gravitational effects are equal. It is considered to be the smallest possible mass that can be measured, and is often used in theoretical physics to explore the nature of the universe at the smallest scales.

4. What is the relationship between Planck mass, time, and length?

In the Planck units system, the Planck mass, time, and length are all interrelated and can be derived from one another. This system is based on the idea that these fundamental units are all equal and can be used to express any physical quantity in the universe.

5. Can Planck mass, time, and length be derived out of thin air?

No, Planck mass, time, and length cannot be derived out of thin air. They are fundamental units that are derived from well-established theories and constants in physics. However, the concept of Planck units and their interrelation can help us better understand the fundamental nature of the universe.

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