What are the units for the Heisenberg Uncertainty Principle?

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Discussion Overview

The discussion revolves around the units associated with the Heisenberg Uncertainty Principle, specifically focusing on the relationship between energy fluctuations and time intervals. Participants explore the implications of these units in the context of quantum mechanics.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that energy levels can fluctuate by an amount, e, for a short time, t, as long as e x t does not exceed h/4pi, questioning the units for time and energy.
  • Several participants confirm that the units for energy are indeed joules and for time are seconds, but one participant expresses uncertainty about this assumption.
  • A participant elaborates on the units of Planck's constant, explaining that it is expressed in m² kg / s, leading to the conclusion that energy is measured in joules when using this constant.
  • Another participant challenges the notion that energy fluctuations disprove the law of conservation of energy, suggesting that quantum mechanics requires careful and precise mathematical treatment of such laws.

Areas of Agreement / Disagreement

Participants generally agree on the units of energy being joules and time being seconds, but there is disagreement regarding the implications of energy fluctuations on the conservation of energy, with some participants asserting that it does not disprove the law.

Contextual Notes

There are unresolved assumptions regarding the interpretation of energy fluctuations and their relationship to conservation laws in quantum mechanics.

Lunct
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To my understanding(correct me if I am wrong), one consequence of the Heisenberg Uncertainty Principle is that energy levels can fluctuate by some amount, e, for a short time, t. As long as e x t does not exceed h/4pi (where h= Planck's constant). My quarry is that what are the units for the time and energy. I assume it is in joules and seconds but the book did not specify so I am unsure.

P.S this energy fluctuation is so weird, it kinda disproved the law of the conservation of energy.
 
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you assumed correct ...
 
Ssnow said:
you assumed correct ...
thanks for clarifying
 
Lunct said:
I assume it is in joules and seconds but the book did not specify so I am unsure.
When you look up the value of Planck's constant, you will see that it is stated with some units: For example, the first Google hit says that ##h=6.62607004\times{10}^{-34} m^2 kg / s##. So if you are measuring your distances in meters, your masses in kilograms, and your times in seconds that's the numerical value of Planck's constant that you'd plug into the calculation. When you do, you'll find that your answer for the energy comes out in units of ##kg\cdot{m}^2/s^2##, the unit that we call a Joule. So yes, Joules are right, but that's not something you have to assume - you chose to have the answer come out in Joules when you chose to write Planck's constant in that form.
P.S this energy fluctuation is so weird, it kinda disproved the law of the conservation of energy.
It does not, but with quantum mechanics you do have to be much more careful and mathematically precise in the way that you state and use the law. We have many other threads on this topic, but if you can't find one that explains it to your satisfaction, feel free to start a new thread asking that question.
 
Nugatory said:
When you look up the value of Planck's constant, you will see that it is stated with some units: For example, the first Google hit says that ##h=6.62607004\times{10}^{-34} m^2 kg / s##. So if you are measuring your distances in meters, your masses in kilograms, and your times in seconds that's the numerical value of Planck's constant that you'd plug into the calculation. When you do, you'll find that your answer for the energy comes out in units of ##kg\cdot{m}^2/s^2##, the unit that we call a Joule. So yes, Joules are right, but that's not something you have to assume - you chose to have the answer come out in Joules when you chose to write Planck's constant in that form.
It does not, but with quantum mechanics you do have to be much more careful and mathematically precise in the way that you state and use the law. We have many other threads on this topic, but if you can't find one that explains it to your satisfaction, feel free to start a new thread asking that question.
Thank you for the reply.
 

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