Just to risk giving @Ann K
Energy, generally speaking, is not conserved. Example: a photon across the expanding universe will redshift and thus become less energetic. Where does its energy go? It doesn't go anywhere, it's just not conserved in that particular situation.
This is another declarative and dogmatic statement without any rationale provided as to why the only viable logical alternative is the photon’s energy disappearing nowhere
. This is also a case of an unwitting encroachment into philosophy and the category mistakes that logically follow. The question of things occurring without any cause
has been discussed at length with much greater depth and analytical rigour in philosophy (ontology) as part of pre-modern and modern debates on the Principle of Sufficient Reason (PoSR).
The seemingly physics-concerning but effectively philosophical proposition that the loss of the redshifting photon’s energy means that the energy simply goes nowhere
is logically equivalent to proposing the photon’s energy slowly ceases to exist. It's equivalent to a claim that nothing
conserves the loss of energy of a photon – there simply isn’t a sufficient reason for the energy conservation. It just doesn't happen. However, such a claim raises these reasonable follow-up questions: If nothing conserves the loss of energy of a photon, how can it simply cease to exist? What inherent or external properties/entities cause it to cease existing? What short of sheer magic can cause total non-existence? How is energy ceasing to exist a scientifically more reasonable and viable explanation than it being conserved by something as yet undetermined?
The anti-PoSR proponent (or scientific instrumentalist) is left with one logical answer which is akin to pure Biblical dogma: We should never ask why. It just happens.
My response: Baloney.
The PoSR provides a powerful philosophical rationale for the Law of Conservation of Energy in physics. It essentially dictates that there must be (a) sufficient reason(s)
for all physical phenomena which the science of physics exists to investigate and to explore. No phenomenon occurs or behaves in a certain way without any cause. If there isn't a sufficient reason/cause for energy to cease existing, the energy is effectively not ceasing to exist. It's conserved by something else than the photon. Hence, to claim as a brute fact that its energy just gradually ceases to exist without any reason is both (literally) unreasonable, highly mystical and scientifically unnecessarily constraining. There could be all sorts of other explanations than the energy ceasing to exist, such as it being absorbed into the expansion of the universe itself (utterly irrespective of which coordinate systems or none are used for its description
). Indeed, under the PoSR, if there's no sufficient reason/cause for the energy to cease to exist, there must
be an alternative reason for the energy's seeming
disappearance. The exploration of this alternative reason is a worthwhile endeavour.
Commitment to such an enterprise of causal exploration of this phenomenon -- and other causes of other phenomena -- is the only constraint of the PoSR. However, on balance, it is less of a constraint than the irrational and dogmatic prohibition of any further exploration of a sufficient reason.
All types of causes are worth exploring in any exercise purporting to describe itself as 'scientific'. A silly commitment to not search for reasons is all well and good in a free world. But one doesn’t get to claim being scientific and open to all possible hypotheses in the same token.
How does this all feed back to the discussion on negative energy? Here’s how I see it, but don't claim infallibility. If energy exists (a self-evident empirical truth), it doesn’t non-exist or less-than-non-exist (i.e. minus-exist). Whatever properties it actually has are positive
by necessity – capacities for x, y and z
– such as rest, motion and radiance to varying extents. The only negative value that can be assigned to energy or any of its properties is purely mathematical or calculational and should not be misconstrued as having any real-world referent. Hence, negative energy/mass as a real physical thing powering warp drives is a category mistake and an absurdity, and therefore the energy condition
is empirically well-founded, and shouldn't be violated.
Wasn't I admirably terse and concise, Ann.