Conservation of energy

Ok, we have null momentum. But… see there’s this wee issue called, umm, conservation of energy. And as wee issues go, it’s not so wee.

Its basically all of physics in a nutshell.

If energy even LOOKS like it’s not going to be conserved, the universe says “NOPE.  Not gonna happen.”

Ah, yes, I can see the issue. But look, universe, I click this and (with no fanfare at all) momentum stops being the rotten little anal-retentive, every column has to add up, universe auditor (in a Terry Pratchett sense). And things just happen.

But, sadly too much of that sort of thing could be counter-productive. I mean, suppose the auditors started getting non-conformist. Horrible thought, scary. Can’t be doing with that. The universe could explode (or implode). Maybe it already did: what was, after all, the reason for the big bang?

So let’s not go around blowing up universes, or even exploding physicist’s brains. How can null-momentum be cool and dandy with energy conservation?

Look, energy has to be conserved. Doesn’t it?

Yes, absolutely. Especially if you’re an auditor (or a theoretical physicist).

Well, probably. At least almost all of the time.

Ok, ok, yes, there’s quantum tunneling, and hall effect, and yes, ok a few other very teeny tiny sub-microscopic violations that we know about.

And, umm, not to put too fine a point on it, one whopping big anomaly called “big bang”.


So, maybe energy conservation is a medium sized thing. At very very small scales, its more of a guideline (maybe the auditors can’t see so well, old buggers, failing eyes, etc.). And at mind bogglingly big scales (doesn’t get much bigger than the universe), which are also at the same time really tiny, maybe they make up their own rules as they go along (maybe the auditors got confused).

But what if I took some energy from over here and put it over there. This happens all the time, of course (hence a nice warm world to live on). Obviously energy wasn’t conserved here, cos there it is over there. So energy conservation is really a system thing. Its only over the whole connected system that energy gets conserved.

It’s just that momentum is kinda stuck to every teeny tiny bit of matter (energy really), it’s not like a light beam, zapping around looking for something to fall on. So momentum gets conserved on all the bits its connected to (all its teeny weeny or huge ‘systems’).

Well, maybe.

What about two balls with a string between them, spinning. CLEARLY each one is changing energy all the time, and its only considering the big system (both balls, the string, and anything else involved) that energy is conserved.

So lets get back to my wee switch: Click. Now, rather than taking time to get energy from object A to object B, this switch lets it disappear from A, and arrive at B. Really quickly. So A stops, the balls spin, B starts, whatever.

No apparent time to transfer, therefore no apparent momentum. And as any media spin artist will tell you, appearances are everything.

The system energy is conserved, just some energy got transferred from A to B, really quickly.

So all the null-momentum button does is provide an open circuit from here to (where?). The auditors can relax a bit, no violations of that energy conservation rule/guideline/whatever here.

Hmmm, now that raises some interesting concepts: maybe its not instant, light speed (or some other speed) limit could apply; what’s the ‘reservoir’; is it the same for everything (a car, a planet, an atom); can it be locally overloaded (or drained); and what does ‘local’ mean? Ooooh, lots to think about!

I can feel the beady non-eyes of the auditors looking my way again. I’d better go think off-line for a bit (they HATE that)


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