J.C.MacSwell

So 1428.57 kg maximum on cable accelerating upward. Capacity would be that - the mass of the empty elevator or 228.57kg.

I think I read it as you intended...my point was implying that since we are not at that point it would be premature to give up on all attempts at modifying gravity. Obviously there are judgement calls to be made. A researcher has to have strong reasons to believe in the plausibility of it, not simply "lets see if we can find an equation that fits all the observations" (much of which is "noisy")

Those are specific models. I'm not suggesting every line of inquiry for modified gravity should be kept open. Certain lines of thought have been more or less shown to be inadequate. Modified gravity as a concept has not IMO. Proof of dark matter may put it to bed, but in the mean time it will no doubt remain open. We are not at that point yet.

I agree. But seems less ad hoc is still far from proof. It just means it seems more plausible at this time. Some form of modified gravity is the second most likely explanation. Why should all of science completely abandon it? A shared explanation between the two ideas is also a possibility.

I thought it was more complicated than that, and it could be tough to find a fit for the dark matter in many cases. Not that the theory/hypothesis was ever proven wrong, but assumptions of the details in particular cases were very much subject to change as more observations were made.

Right. As I said in my earlier post, isn't it just assumed to be where needed? If say, you assumed it was where not needed it would not fit at all...so nothing really special about the fact that it matches... ...or am I missing something?

I don't think that is correct. I think the amount, and positioning, that is required varies in different Galaxies. If I'm wrong and the amount and position is consistent wrt ordinary matter in some way...why would a modified gravity function not fit just as well?

"2.) Modified gravity: When you look at rotating galaxies... ...When we add dark matter, they all match. When we modify gravity, the modifications we need to make to solve one problem fail to solve the others. " The problem here is that of course it would match...you get to assume it is exactly where needed without basing it on any observation but the observation you are hoping to resolve. Until that changes modified gravity needs to stay in the game, even if it is the lesser likelyhood.

That would be the intent

Starting out just the 1 kg, otherwise empty...I think that was the idea

Yes. When it's moving, when it's a photon, it travels at c.

If it's not at c, it's not a photon...

If you are wondering why it's there twice...just my incompetence...I tried several times to edit one away.

What? You don't like my perpetual motion machine design? (others might call it an Escher drawing)

"It" would be the universe. I really don't know why a universe would expand, contract, or stay the same but thought mass density might have something to do with it.

Would it not depend on it's initial size? If it is small enough it would stay small or even contract? If it was expanding what would drive the expansion? (or is that unknown but assumed since this one does?)

That's a reasonable assumption. Possibly the most reasonable? (I don't know)

They would presumably follow a geodesic until it showed up in front of them...or not...but that would depend on the metric.

This was my thought as well wrt the size and metric of this universe, and whether equilibrium could be reached (expanding, contracting, static somehow etc). No other matter to radiate back (initially at least), but maybe it all comes back, reradiates etc etc. If the universe is small enough our kg might stay nice and toasty.

It would depend on the size and metric of this universe would it not? I guess if it is a 1 kg "mass" that might put limits on what is possible... It could reach equilibrium, or not, at or from almost any temperature where the matter itself is stable If, say, it was isolated (read remote) in this Universe it would be at or heading toward 2.7 K

For "perpetual motion" I tend to think in the same context as yourself and Swansont when it regards machine design especially, or physics generally, but the term is also used in the context Studiot describes. Wiki, for example, seems to look at it as Studiot does: https://en.wikipedia.org/wiki/Perpetual_motion Just my (overpriced no doubt), $0.02

+1 for the first honest perpetual motion claimer ever!

How about the idea that the present Laws of Physics don't allow it?

From what I've seen of many a successful perpetual motion machine, a little misunderstanding always helps. Cycling of seemingly insignificant errors until they add up to something special seems to be the key, and if all else fails when making a prototype, just cheat a little, put it on You Tube and by all means ask for money...you are after all saving the World at the expense of greedy oil and power companies...