Is it scientifically possible to prove something is impossible?

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I am not sure of the correct place to pose this question, thus I put it here.

Is it scientifically possible to prove something is impossible?

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It must be either possible or undecidable. If not then you have successfully proved that it is impossible to prove that something is impossible - and that is self-contradictory.

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Science doesn't deal in proof, per se, since it's inductive. However, there are principles that are so well-established, e.g. the laws of thermodynamics, that a phenomenon like free energy is considered impossible.

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Science doesn't deal in proof, per se, since it's inductive. However, there are principles that are so well-established, e.g. the laws of thermodynamics, that a phenomenon like free energy is considered impossible.

Entropy

Reversal of entropy has long been discussed

The laws of thermodynamics state that "Entropy", the measure of order towards disorder, in a closed system, "cannot be reversed". This theory is not in question, even when the nature of closed systems is at issue. The increase in entropy is contained in the Second Law of Thermodynamics, and effectively states that the arrow of time (time theoretically being one-directional) requires everything to proceed toward ever increasing chaos, such that all structures are ultimately doomed and sadly that is one of the reasons that cause our death..

However, in an open system, there can be an influx of energy into the system capable of, in full accord with the Second Law of Thermodynamics. Energy input can decrease entropy, and can simultaneously increase order thus there might be "outside energy sources" which somehow blast energy into our universe, maybe a "White Hole" for example etc.

The point is do we know for absolute certainty whether our universe, is a closed or an open system?

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We don't exactly know, but we do know that the total amount of energy and mass in the universe is conserved.

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We don't exactly know, but we do know that the total amount of energy and mass in the universe is conserved.

The British physicist Stephen Hawking, speculated at a scientific convention that information, or energy could leak out of the universe via the death or evaporation of a black hole. If this were true then energy could likewise come into our universe in the reverse, maybe in the form of a white hole This does not violate the conservation of mass and energy, it just pushes the question further back.

When asked where the information/energy went after the final evaporation of a black hole, he suggested that the energy or information from our universe, did not vanish out of existence but was forced into some other universe via said black holes.

However, Hawking’s proof of black hole evaporation violated this most fundamental law. If a black hole disappeared, what happened to all the information it absorbed? It would disappear with the black hole, a clear violation of the conservation of mass/energy. In essence, Hawking described black holes as huge cosmic machines that went around erasing parts of the universe and proclaimed that parts of the universe were missing as a result.

Physicists were mind boggled and needed to disprove this theory. Why? Because the implications were that if black holes could violate this law, then the law was no longer a law of the universe. If it was no longer a law, that means that information anywhere in the universe could potentially be erased, and not just inside black holes. Further, at this time more black holes were discovered – there were supermassive black holes and micro black holes. There could even be micro black holes existing in your room as you read this. If black holes have the power to erase information, how can you say anything you know or see or feel or believe is real? Nothing is certain if everything is impermanent. This caused a huge fuss and was known as the Information Paradox.

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I would say that within some theory one can prove that some processes are impossible. But then we are left with asking how well the theory matches the Universe. In that sense, we cannot really prove that something is impossible. Nature may be more subtle than our theory may suggest and mechanisms we have not yet thought of could exists, but they must not violate what we know holds.

For example it could be the case that we have Lorentz violation at some energy scale and this would upset our notions of causality and the speed of light as a maximum speed. However, any observable effects of this must be very small on the scales we have already probed well.

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I would say that within some theory one can prove that some processes are impossible. But then we are left with asking how well the theory matches the Universe. In that sense, we cannot really prove that something is impossible. Nature may be more subtle than our theory may suggest and mechanisms we have not yet thought of could exists, but they must not violate what we know holds.

For example it could be the case that we have Lorentz violation at some energy scale and this would upset our notions of causality and the speed of light as a maximum speed. However, any observable effects of this must be very small on the scales we have already probed well.

The Big Bang singularity seems to violate causality?

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The Big Bang singularity seems to violate causality?

We don't really understand the nature of singularities like this so it is hard to say for sure if you should really think like this. For sure, the physics at these scales requires quantum gravity and this will most likley require us to think differently about space and time than we do in classical general relativity. Questions like "what caused the big bang?" and similar may not be so well posed. But I speculate here.

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I am not sure of the correct place to pose this question, thus I put it here.

Is it scientifically possible to prove something is impossible?

What came first, the chicken or the egg?

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What came first, the chicken or the egg?

The egg because there were egg producing animals before chickens existed on earth, of course this just pushes the answer further back

http://en.wikipedia.org/wiki/Proof_of_impossibility

A proof of impossibility, sometimes called a negative proof or negative result, is a proof demonstrating that a particular problem cannot be solved, or cannot be solved in general. Often proofs of impossibility have put to rest decades or centuries of work attempting to find a solution. Proofs of impossibility are usually expressible as universal propositions in logic (see universal quantification).

One of the oldest and most famous proofs of impossibility was the 1882 proof of Ferdinand von Lindemann showing that the ancient problem of squaring the circle cannot be solved, because the number π is transcendental and only algebraic numbers can be constructed by compass and straightedge. Another classical problem was that of creating a general formula using radicals expressing the solution of a polynomial equation of degree 5 or higher. Galois showed this impossible using concepts such as solvable groups from Galois theory, a new subfield of abstract algebra that he conceived.

Edited by Alan McDougall
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The egg because there were egg producing animals before chickens existed on earth, of course this just pushes the answer further back

I think it refers to the chickens egg, not any egg ever. However, I was just making a joke on the topic of hard to answer questions.

Edited by Ailurophobia
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http://en.wikipedia.org/wiki/Proof_of_impossibility

A proof of impossibility, sometimes called a negative proof or negative result, is a proof demonstrating that a particular problem cannot be solved, or cannot be solved in general. Often proofs of impossibility have put to rest decades or centuries of work attempting to find a solution. Proofs of impossibility are usually expressible as universal propositions in logic (see universal quantification).

One of the oldest and most famous proofs of impossibility was the 1882 proof of Ferdinand von Lindemann showing that the ancient problem of squaring the circle cannot be solved, because the number π is transcendental and only algebraic numbers can be constructed by compass and straightedge. Another classical problem was that of creating a general formula using radicals expressing the solution of a polynomial equation of degree 5 or higher. Galois showed this impossible using concepts such as solvable groups from Galois theory, a new subfield of abstract algebra that he conceived.

But that is mathematics, not science, a field (the only field?) where it is possible to prove things.

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I think it refers to the chickens egg, not any egg ever. However, I was just making a joke on the topic of hard to answer questions.

I know you were joking, however, the best answer biologically is neither.

But that is mathematics, not science, a field (the only field?) where it is possible to prove things.

I agree, but is mathematics not a very necessary part of science?

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I agree, but is mathematics not a very necessary part of science?

Yes it is. But that doesn't mean that science as a whole can prove anything.

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I know you were joking, however, the best answer biologically is neither.

I agree, but is mathematics not a very necessary part of science?

OK lets put it another way, can science prove something is false or untrue?

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OK lets put it another way, can science prove something is false or untrue?

Sure. If you claim that objects fall at a rate that depends on their mass, I can do an experiment and show that your claim is false. The more specific a statement, the easier it is (in principle) to show that it's false, if it is indeed a false statement.

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Sure. If you claim that objects fall at a rate that depends on their mass, I can do an experiment and show that your claim is false. The more specific a statement, the easier it is (in principle) to show that it's false, if it is indeed a false statement.

The astronauts did that test on the moon, with a feather and I think a rock , the fell at the exact same rate reaching the ground at the same moment, they used a feather to show that on the moon, unlike earth, there was no atmosphere to hold up the feather . Of course I know you are aware of this, just added it for the interest of those that don't.

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It would not be a violation of conservation of mass and energy, since the black hole gains mass. When the black hole evaporates, the mass it absorbed would also be evaporated, and this would not violate the conservation of mass.

Energy and mass are interchangeable, since $E=mc^2$. A black hole evaporating would basically mean that all of the energy of a black hole would be converted into radiation. I don't see how this violates the conservation of energy.

If white holes exist, they would have negative entropy. Therefore, the entropy is negative of that of a black hole, i.e $S=\frac{-Akc^3}{4G\hbar}$. That would be a violation of the 2nd law of thermodynamics in a closed system universe. Meanwhile, the metric would still be the same, as the metric for a spherical, non-rotating body (Schwarzschild metric) is $ds^2=(1-\frac{Rs}{r})dt^2-(1-\frac{Rs}{r})^{-1}dr^2-r^2d \theta ^2 - r^2sin^2(\theta )d \phi ^2$. But, a white hole needs to have everything away from it. It has to move in a direction opposite of that of black holes, i.e negative gravity. In order for this to work, we need to have the metric in the direction outwards. Since a white hole would have negative gravity, we find that the mass of a white hole must be negative. And because black holes emit hawking radiation, white holes would have to absorb it, making them eventually evaporate, since it would gain mass from hawking radiation.

White holes would be a violation of thermodynamics if the universe is a closed system. If black holes actually do make mass disappear, there would have to be white holes to keep the amount of mass and energy in the universe the same. But, I don't see how black holes violate the law of conservation of mass/energy, since the mass and energy would turn into radiation with the black hole.

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It would not be a violation of conservation of mass and energy, since the black hole gains mass. When the black hole evaporates, the mass it absorbed would also be evaporated, and this would not violate the conservation of mass.

Energy and mass are interchangeable, since $E=mc^2$. A black hole evaporating would basically mean that all of the energy of a black hole would be converted into radiation. I don't see how this violates the conservation of energy.

If white holes exist, they would have negative entropy. Therefore, the entropy is negative of that of a black hole, i.e $S=\frac{-Akc^3}{4G\hbar}$. That would be a violation of the 2nd law of thermodynamics in a closed system universe. Meanwhile, the metric would still be the same, as the metric for a spherical, non-rotating body (Schwarzschild metric) is $ds^2=(1-\frac{Rs}{r})dt^2-(1-\frac{Rs}{r})^{-1}dr^2-r^2d \theta ^2 - r^2sin^2(\theta )d \phi ^2$. But, a white hole needs to have everything away from it. It has to move in a direction opposite of that of black holes, i.e negative gravity. In order for this to work, we need to have the metric in the direction outwards. Since a white hole would have negative gravity, we find that the mass of a white hole must be negative. And because black holes emit hawking radiation, white holes would have to absorb it, making them eventually evaporate, since it would gain mass from hawking radiation.

White holes would be a violation of thermodynamics if the universe is a closed system. If black holes actually do make mass disappear, there would have to be white holes to keep the amount of mass and energy in the universe the same. But, I don't see how black holes violate the law of conservation of mass/energy, since the mass and energy would turn into radiation with the black hole.

Have they proved that when black holes evaporate, they give off radiation? Black holes already give off radiation. Did you read this some where, or were you using logic to reach your conclusion.

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Have they proved that when black holes evaporate, they give off radiation?

It is the other way round: black holes radiate, therefore they lose mass (energy) and therefore they evaporate. (Although, in reality, they will always gain more mass than they radiate.)

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When black holes radiate, they loose some mass. The reason black holes evaporate is because they radiate, since they eventually loose all of their mass.

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Have they proved that when black holes evaporate, they give off radiation? Black holes already give off radiation. Did you read this some where, or were you using logic to reach your conclusion.

Is there proof that after a black holes has radiated "all the matter and energy" that has been "sucked into them" by their colossal gravity field "over their life time", back into the universe, thus maintaining the conservation of information within the universe?.

Or has the idea that a black hole "actually evaporates" have any proof mathematically or otherwise,out of the universe at large ? At one time it was thought that the stuff pulled into a black hole went elsewhere, maybe into another universe, this is/was a theory of Stephen Hawking, I am not sure if he still believes this as a possibility! Note "Evaporate" in my opinion is a bit vague!

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• 1 month later...

No, proving something impossible is never possible. Impossible will only mean you have lack of resources or knowledge. In early times it was impossible to imagine space-time as curved, but later on with upgradation in knowledge it's possible.. Nothing is impossible

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Nothing is impossible

While the underlying message here is laudable (that we should recall our current limitations are often overcome with cleverness and creativity and that we should not give up before we even begin... that we are capable of amazing things and brilliance), there truly are some things that are impossible. For example, it's impossible for you to give me an accurate answer to "What is the square root of 2" using a rational number. Some things truly are impossible, and IMO it's okay to acknowledge that. We can do so without losing the passion and energy that is human exploration.

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