# I Uncertainty principle

#### Kara386

For an unstable particle is it reasonable to take the uncertainty in energy as the energy it was created with? If so, why?

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#### ZapperZ

Staff Emeritus
2018 Award
For an unstable particle is it reasonable to take the uncertainty in energy as the energy it was created with? If so, why?
Your question is extremely puzzling. What "energy" are you talking about when you are referring to the "uncertainty in energy"?

Secondly, muons are created in many different ways at many different energies. Yet, they have the same decay lifetime. So if you think that a muon's decay is dependent on the energy that was used to create it, then this should already answer your question.

Thirdly, what do you mean by "unstable particle"? How "unstable" are we talking about here? A free neutron is unstable. Is this part of the particle that you want to know even though its lifetime is in minutes?

There are many "baggages" surrounding this question that you have not explained.

Zz.

#### Kara386

Your question is extremely puzzling. What "energy" are you talking about when you are referring to the "uncertainty in energy"?

Secondly, muons are created in many different ways at many different energies. Yet, they have the same decay lifetime. So if you think that a muon's decay is dependent on the energy that was used to create it, then this should already answer your question.

Thirdly, what do you mean by "unstable particle"? How "unstable" are we talking about here? A free neutron is unstable. Is this part of the particle that you want to know even though its lifetime is in minutes?

There are many "baggages" surrounding this question that you have not explained.

Zz.
Apologies, I didn't really consider those things! Ok, so to clarify:
The question was prompted by an example from a lecture. A delta baryon is produced with energy of 12,300MeV and its mean lifetime is calculated using the uncertainty principle. But the uncertainty in energy used in the calculation was simply the given energy of the delta baryon.

"Uncertainty principle"

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