stupid physics questions

[zip accident]

Since it seems that quantum works for tiny, relativity works for huge, what name would be good for the theories that work in between? Newtonian would probably be controversial, and Newton was apparently a jerk.

[k345y]

Willsimonjayneillian.

[gumboot]

Newton was apparently a jerk.

I think the modern term is sperg.

[pogo]

Since it seems that quantum works for tiny, relativity works for huge, what name would be good for the theories that work in between? Newtonian would probably be controversial, and Newton was apparently a jerk.

“Newtonian” is fine. Or just “physics”, or “classical physics”. Relativity is more needed when things go very fast than when they go large. E.g. redshift depends only on classical physics, and that lets us see and gauge the speed of incredibly large and distant objects.

Newtonian mechanics has not gone away; it’s still used extensively. Anyone doing engineering is using Newtonian mechanics, except for the very few concerned with the engineering and mechanics of spaceflight. Relativity only comes into play at high speeds of the sort not possible on the Earth’s surface.

[zip accident]

Since it seems that quantum works for tiny, relativity works for huge, what name would be good for the theories that work in between? Newtonian would probably be controversial, and Newton was apparently a jerk.

“Newtonian” is fine. Or just “physics”, or “classical physics”. Relativity is more needed when things go very fast than when they go large. E.g. redshift depends only on classical physics, and that lets us see and gauge the speed of incredibly large and distant objects.

Newtonian mechanics has not gone away; it’s still used extensively. Anyone doing engineering is using Newtonian mechanics, except for the very few concerned with the engineering and mechanics of spaceflight. Relativity only comes into play at high speeds of the sort not possible on the Earth’s surface.

Then has any work been done in classical/Newtonian physics since 1900?

[pogo]

Yes and no. Newtonian mechanics has been stable for a long time, and has not really changed since 1900 or so. What happened around then was people started applying classical physics to new things – electricity, magnetism and radiation – which had been recently discovered, and found they had problems explaining everything.

The solution to this was special relativity. It did not invalidate or replace Newtonian mechanics, but helped fill in the gaps that had arisen in it. Quantum mechanics arose in a similar way when classical physics was applied to very small things and the effects of very small things. They worked so well that both SR and QM quickly became part of physics, along with general relativity when it was discovered.

There is no separate “classical physics” now. There’s just physics which includes classical, relativity and quantum physics. So in a sense all physics done since 1900 has been done “in classical physics” as it’s all one thing.

[gravy]

Classical physics is a term often used to mark the divide between theories do and don't have the idea of quantisation at it's core. General relativity is a classical field theory.

It's an important theoretical distinction because there's likely no physical distinction and in turn highlights we're not close to a full description of physical law.

[zip accident]

Mond raises it's head again:

First test of rival to Einstein’s gravity kills off dark matter

[Absolute_Zero]

^^^

As a long-time critic of the exotic dark matter paradigm, I might be expected to cheer this slightly stale news... well, a little. But first: 'New Scientist' sucks.

co-author of the paper.
https://twitter.com/koenkuijken/status/ ... 0761263104

Whilst this MoND [Verlinde] suffers less in the way of adjustable parameters than the DM model, the objection remains.

Apart from my philosophical complaints... recent observations indicate that the rotation issue doesn't simply apply to galaxy-scale objects, it's an emerging problem for globular clusters too... which isn't a good fit with a theory that operates exclusively at the larger, galactic scale. This is what can happen when you tune/find a hypothesis to fit the data as it exists in the "present" in the expectation that the data won't change in the future. Dark Energy could well suffer a similar fate.

For a few years now I've followed an alternative that performs within the error bars of the observational data, without adjustable parameterisation. Just the visible matter, the co-moving diameter of the cosmos and the speed of light.

I haven't run it up the flag pole as-yet for its reliance on the hypothetical Unruh Effect... but I'm hopeful, not least since it fixes several other anomalies besides the galaxy rotation issue [and the aforementioned new cluster observations]. Not to mention [oops] a candidate theory of operation for the EmDrive, if real.

Still, as ever, if wishes were fishes...

[KlaxonCow]

There's clearly something wrong with gravity.

We essentially know this already. We have no quantum theory of gravity. General relativity and quantum mechanics just don't fit together - which, if they're both right, is a logical impossibility. There is definitely a truly massively important "missing bit" right there in our understanding of gravity and we know that already.

The value of a scientific theory can be measured by its predictive power. Well, the assumption was that gravity must be slowing down the expansion of the universe. The only question was by how much? Enough for a big crunch or not enough to expand forever?

Then we take a look - empirically test that predictive power - and, fuck me, it's beyond just wrong, it's entirely arse backwards. The expansion is actually speeding up! Its predictive power is not even zero, but actually bloody negative!

Quick, stuff some "dark energy" into the gaps and hope no-one notices.

We look at the mass of the universe, we apply our understanding of gravity to it and... oh... none of it is coming out right at all. Galaxies shouldn't really be doing that. Globular clusters ought not to be quite like that either.

Oh, bugger. Quick, stuff some "dark matter" into the gaps and hope no-one notices.

I mean, it's matter that's invisible, intangible, undetectable, reacts with nothing - which, you know, so far are all the properties of something that simply doesn't even exist - but has that one useful attribute of supplying the extra missing gravity that we can't account for. How horribly convenient.

Don't get me wrong, it could be right and I'm not saying otherwise. But it just sits badly with me, as it's much too close to the kind of "God did it" non-explanations of religion for my tastes. Can't explain the diversity of life? Quick, stuff a god into the gaps! Okay, it's much better to be stuffing missing mass into the gaps instead, of course, but it just feels too much like the same old sleight of hand relabelled as something else.

The four fundamental forces. We've combined three of them. But the fourth - gravity - remains elusively uncombinable and, indeed, is inexplicably at totally the wrong "strength". Why is it many, many orders of magnitude weaker than it really ought to be? I mean, it's handy that it is, from the perspective of the universe existing, but why?

There is definitely a problem there. And if you look at all these outstanding problems then gravity is the common factor.

Now, of course, I don't know what's wrong with it. I don't know what the actual right answer might be. So, in the meantime, we've no choice but to proceed with our understanding as it stands. Do the best with what we've got.

But, as we do so, we should feel niggled and irritated that it just doesn't quite sit right. We've clearly not solved this completely.

There is still something wrong somewhere with gravity.

[gumboot]

There's clearly something wrong with gravity.

Shut it down until we can figure out what's going on!

[KlaxonCow]

Oh, yes. I missed one.

There's also "dark flow". Shit on the most massive scales of all is moving about in weird ways. Why's it doing that? Again, fuck knows. But surely the only influence these massive groups of galaxies could be exerting on each other is gravitational, right?

[gravy]

I haven't run it up the flag pole as-yet for its reliance on the hypothetical Unruh Effect...

How does that work? Accelerated bodies gain energy, being in a gravitational field is identical to accelerating, energy increases a gravitational field. What stops a run-away feedback loop that tends to infinite energy?

[Absolute_Zero]

I haven't run it up the flag pole as-yet for its reliance on the hypothetical Unruh Effect...

How does that work?

The 'Unruh Effect'? Or do you mean in terms of its postulated part in modulating gravity? I'm not quite following, but in the meantime...

being in a gravitational field is identical to accelerating

I'm not sure it's the case here, but sometimes the "identical" is taken too literally. In principle the two are distinguishable.

You're in the proverbial lift-like enclosed space, hereafter 'box'

#1 With your arms outstretched, drop an object from each hand.

a) under acceleration, the two objects will hit the floor spaced exactly as released.

b) in a gravitational field, the two objects will land the tiniest bit closer... triangulated on the center of gravity.

Under acceleration - lines of force are exactly parallel
In a gravitational field - slightly not

#2 Measure the force at the top of the box and compare with the bottom

Under acceleration - same top and bottom
In a gravitational field - slightly less at the top per the inverse square law

[Dio]

If I had to put money on the winning trick, myself I'd go for gravity being unified with thermodynamics. It's a "force of order".