Linked Questions

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2answers
2k views

If energy cannot be created, how did the universe come into existence? [duplicate]

The first law of thermodynamics states that energy cannot be created. If that's the case, how did the universe come into existence? I mean, doesn't that require energy to be created? Excuse my ...
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3answers
3k views

Why is energy conserved? [duplicate]

From basic principals, how does one prove that energy is conserved? Or a little more specifically - Why does this hold: $$\Delta \mbox{ PotentialEnergy} + \Delta \mbox{ KineticEnergy} = 0 $$ Or, for ...
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2answers
593 views

Is conservation of energy a set of principles that is inevitable in any 'possible world'? [duplicate]

It is usually stated in various books or stories 'Energy can't be created or destroyed , but is conserved'. I guess this is within a closed system. Are there any axioms or principles in physics that ...
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1answer
404 views

From Noether's Theorem, is it true that the law of conservation of energy can be proved? [duplicate]

So what I understand is that the law of conservation of energy, likes Newton's law of motion, can't be proved. However, by Noether's Theorem, if there is a time symmetry, the energy is conserved. It ...
2
votes
1answer
404 views

What is the reason behind why energy must always be conserved, apart from observation? [duplicate]

I know that we see in experiments (physical and thought) that energy is always transformed into something else, but what propels our universe to behave this way? What is happening at small levels that ...
4
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0answers
387 views

Conservation of Energy in the Universe [duplicate]

Possible Duplicate: Is energy really conserved? Why can’t energy be created or destroyed? One of the laws of the universe that dazzles me the most is the law of conservation of energy. I ...
0
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0answers
30 views

How do we know that the conservation of energy is true? [duplicate]

As I have studied Mechanics and Thermodynamics, it appears that many of the concepts and ideas behind Physics depend on the Law of Conservation of Energy. The textbooks, however, don't explain where ...
22
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7answers
4k views

How can energy be useful when it is 'abstract'?

The topic which haunted me for two years until I gave up on it. But now I am doing engineering and this topic suddenly popped out of my textbook from nowhere. I seriously need to understand this topic ...
23
votes
5answers
3k views

How do we know that energy and momentum are conserved?

How do we know energy and momentum are conserved? Are these two facts taken as axioms or have they been proven by an experiment? This question has been in part addressed here: Conservation of ...
26
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3answers
9k views

Energy conservation in General Relativity

I understand that energy conservation is not a rule in general relativity, but I'd like to know under what circumstances it can still be possible. In other words, when is it possible to associate a ...
9
votes
4answers
38k views

Proof of conservation of energy?

How is it proved to be always true? It's a fundamental principle in Physics, that is based on all of our currents observations of multiple systems in the universe, is it always true to all systems? ...
18
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5answers
7k views

Conservation law of energy and Big Bang?

Did the law of conservation of energy apply to the earliest moments of the Big Bang? If so, what theoretical physics supports this? I hear that Einstein's theory of relativity disputes the law of ...
10
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4answers
3k views

On what basis do we trust Conservation of Energy?

I'm happy to accept and use conservation of energy when I'm solving problems at Uni, but I'm curious about it to. For all of my adult life, and most of my childhood I've been told this law must hold ...
20
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3answers
12k views

Photons in expanding space: how is energy conserved? [duplicate]

If a photon (wave package) redshifts (stretches) travelling in our expanding universe, is its energy reduced? If so, where does that energy go?
3
votes
4answers
1k views

Is the principle of Conservation of Energy empirically verifiable?

Before I am inundated by myriad and vociferous claims that conservation of energy is the single most well-attested and experimentally verified principle in all of science, let me say that I am well ...

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