Can energy conservation be violated?

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Discussion Overview

The discussion revolves around the concept of energy conservation, particularly in the context of photon energy as observed from different reference frames. Participants explore whether energy can be created or if it varies based on the observer's frame of reference, with a specific focus on the Doppler effect and the interaction of light with moving mirrors.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant suggests that energy can be created and argues that the energy of a photon increases when emitted from a moving train and reflected back, as perceived by different observers.
  • Another participant counters this claim, stating that energy cannot be created and explaining that energy and momentum transfer occurs during the reflection of light off the mirror, which moves towards the train.
  • A third participant supports the idea that the mirror provides the additional energy, noting that light exerts pressure on surfaces, which affects the mirror's speed and energy conservation.
  • A later post asserts that energy conservation is upheld and directly answers the thread's title question with a definitive "No."

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the creation of energy and the implications of energy conservation in the described scenario. While some argue for the possibility of energy variation based on reference frames, others maintain that energy conservation principles are not violated.

Contextual Notes

The discussion includes assumptions about the behavior of light and energy transfer in moving frames, as well as the implications of the Doppler effect. There are unresolved nuances regarding the definitions of energy conservation in different contexts.

Who May Find This Useful

This discussion may be of interest to those exploring concepts in physics related to energy conservation, reference frames, and the behavior of light in relativistic contexts.

Ironman1998
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I think energy can be created...i agree that energy is not conserved between different reference frames..but i can show you that energy measured in a single frame may wary... Does photon's energy increase when i emit it from a train which is moving at comparable speed and get it reflected back by a mirror on a platform so that i can catch it again in the train? According to doppler effect the frequency of the photon for an observer standing near the mirror is greater to an observer in the train.So to the observer near the mirror, energy of the photon is greater than the energy observed by an observer in train.Similarly when it gets reflected back and reaches the train its frequency is larger than the initial frequency when observed by an observer in train .So obviously energy of photon is increased without doing any work...please correct me if i am wrong somewhere
 
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Ironman1998 said:
I think energy can be created
No it can't.

Ironman1998 said:
So obviously energy of photon is increased without doing any work...please correct me if i am wrong somewhere
The light bounces off the mirror, and there is energy and momentum transfer there. In the frame of the train the mirror is moving towards the train and is slightly slowed by the reflection. Its kinetic energy is carried away by the light.

[Mentors' note: This post has been edited to remove a loose end from when it was moved from another thread]
 
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Ironman1998 said:
So obviously energy of photon is increased without doing any work...please correct me if i am wrong somewhere
As @Ibix mentioned, the mirror is the source of the additional energy. Recall that light exerts pressure on a surface. This pressure reduces the speed of the mirror and thereby transfers both energy and momentum to the light. Energy is conserved in this case.
 
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Answer to the title question: No.

Follow-up: Do you really think that millions of scientists and engineers over the past hundred years could plausibly have all missed something so obvious?
 

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