Seeking the unknown in the known (part 1, energy)

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In summary, the conversation discusses the concept of energy and how it relates to systems changing with time. The speaker realizes their lack of understanding and hopes to find more explanations on the subject. They also mention the classical and quantum mechanical aspects of energy, specifically the Hamiltonian equation. The conversation ends with a request for a book recommendation on the topic.
  • #1
A few years ago it came to my attention that everything somehow always related to energy. But the more I thought about it, the more I realized that I don't understand what energy actually is . There isn't a very good explanation of energy in my physics textbooks, only the basic stuff about energy. And my physics teacher sounds like she has never heard of the subject physics .

I'm hoping for some good explanations on energy (I say explanations and not explanation, because I think that there are more perspectives on this subject than just one).
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  • #2
The concept of energy is classical, but when we convert it to a quantum mechanical concept we find that it is just the change of the phase of a quantum mechanical amplitude with time.That is what makes energy so important, it is related directly to how systems change with time. The quantum mechanical equation that describes the energy of a system is called the Hamiltonian, and it tells us how a system changes with time. If we want to make a system change with time we have to put some energy into it, which is why we heat a mixture of chemicals to make them react faster, etc..

That should give you some perspective on the true nature of energy.
  • #3
Thanks tyger, finally I'm learning some of the good stuff

Could you please recommend a book on this subject? I'd really appreciate it.

I thank you in advance,


1. What is energy?

Energy is the ability to do work or cause change. It exists in many forms, such as kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat), and electric energy.

2. How is energy measured?

Energy is measured in joules (J) or calories (cal). One joule is equal to the amount of energy needed to lift a small apple one meter off the ground. One calorie is equal to the amount of energy needed to raise the temperature of one gram of water by one degree Celsius.

3. What is the relationship between energy and matter?

Einstein's famous equation, E = mc², describes the relationship between energy and matter. It states that energy and matter are interchangeable and can be converted from one form to another.

4. How does energy transfer and transform?

Energy can transfer from one object to another through various processes, such as conduction, convection, and radiation. It can also transform from one form to another, such as potential energy being converted into kinetic energy as an object falls.

5. What are some examples of renewable and non-renewable energy sources?

Renewable energy sources include solar, wind, hydro, geothermal, and biomass. These sources can be replenished and will not run out. Non-renewable energy sources, such as fossil fuels (coal, oil, natural gas) and nuclear energy, are finite and will eventually run out.

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