Strange

No. Go on. How was it vital? If it were vital, it would have been confirmed by experiment.

OK. Maybe I should have phrased that better: We had a model for the transmission of light waves before the aether was disproved and we had the same one afterwards. Do not confuse the two what? But is your point just that the aether was a hypothesis that was disproved and (most) dark matter explanations are hypotheses that will be disproved? In which case, why sound so negative about the normal process of science? (And it is Saturday here!)

No. We had a model that explained electromagnetic waves before the aether. We had exactly the same model after the aether was disproved. Nothing changed. So it can't have been vital. But I suppose you are right in that a model was proposed, tested and then rejected. This is what will, inevitably, happen to some (maybe all) of the current hypotheses for dark matter, etc. Because of evidence. So we should not attempt to create and test new models to explain new evidence? We should just ignore it? Of course it is conclusive. The measurements that Zwicky made have been repeatedly confirmed. And then similar measurements were made within galaxies. And then gravitational lensing observations have been confirmed this. And so on and so on. Do you have any reason (evidence) to say that all these many measurements are wrong? (Maybe I should as a moderator to split these posts to Speculations where you will have to properly defend you views.)

Those are completely different sorts of reasoning. One is not based on evidence, the other is. Can you explain what the similarity is, instead of just repeating the same thing. So, what should we do about the evidence? Ignore it because we don't have an explanation? Or come up with some models and test them (you know, do science)?

I don't understand the comparison you are making. The aether was an assumption made for no reason (ie. no evidence). When tests were done to test the various aether models, no evidence was found. And, as noted, the aether would require physically impossible and contradictory properties. So this seems to be completely different than the examples you give, which are entirely based on evidence. Dark energy is an explanation for the observations we have made (ie. evidence). There are multiple hypotheses for what dark matter could be (including various forms of matter, different ways of modifying gravity and others). These are all being tested by looking for further evidence predicted by each model. The same is largely true of dark energy: there is evidence that needs explaining. People are looking for more evidence to confirm or rule out various possible explanations. And inflation is a hypothesis to explain aspects of the early universe. There are alternative hypotheses. Again, people are looking for evidence to confirm these or rule them out. In all cases, we don't know what the explanation is, but there is evidence that requires an explanation. Do you think we should just ignore the evidence? What are you suggesting? how are these analogous to the aether?

This is a huge question. The short answer is evolution (https://en.wikipedia.org/wiki/Evolutionary_history_of_plants). The full answer is several years study at university and probably some postgraduate research. To provide an answer in between those extremes, probably requires something a bit more specific. Like: how did plants gan the ability to photosynthesise; or when did they colonise land or ... (I found a page that seemed to have a good summary of the timeline of plant evolution, but then I noticed it said things like "how things evolve is not understood" and "millions of years ago, supposedly" and "it is illegal to talk about god in the UK", so I decided it probably wasn't a reliable source!) p.s. Have requested this is moved to a more appropriate section of the forum

Light waves travel at a constant (and, more importantly, invariant) speed. Why is that so odd? The speed can be related to the permittivity and permeability of the vacuum (but that just pushes the question of "why that speed" back one step - why do they have those values). In relativity, all massless particles travel at c. Probably because it is the scaling factor between the units we use for measuring distance and measuring time. In natural units, the speed of light is 1. Which seems, well ... natural.

That is the same "common sense" assumption that made people think there was an aether int eh first place. It is still baseless. It doesn't matter how often you repeat it, there is still no reason or evidence for this claim.

There are a few models that could fall under this description (even though it is a bit vague): The "big bounce" where the universe is the result of the collapse of an earlier version (implementation!) of the universe. (Dark energy makes this one seem less likely than it used to be.) The universe could be infinitely old - this is the result of a model that attempts to add quantum theory to GR in the early universe. Eternal inflation where "bubble" universes like ours appear continuously from continuously inflating space. The what? You would need to show, mathematically, that this produced the effects we see. Also, as dark matter and dark energy have such vastly different properties, it is hard to see how they could share the same explanation (although there are attempts to do this).

I wouldn't call these theories; just speculative ideas. We have zero information about whether the universe was created and if so how. Nothing to be ashamed of. Some of my best friends are electronics engineers! No a good way to judge scientific ideas. I don't really know what this story is supposed to describe. Or how it relates to the universe. Do you want to have another go?

Some materials have can different crystal structures or allotropes with different densities. An obvious example is carbon where diamond is denser than graphite.

! Moderator Note I have locked this thread. This forum is not an appropriate place to seek medical advice. Especially if you are self medicating.

Having now convinced myself that there is (or could be) a magnetic field, I don't see why there shouldn't be a difference between the presence of an electric field and a magnetic field in the two cases. What you suggest looks a bit like the technique of minimising the magnetic field (or EM radiation) from signal wires by, for example, using a twisted pair (so the fields generated by the outward and return currents cancel out). Or, the opposite of that, perhaps...

The evidence against the ether now is largely the same as it was in the 19th century. All attempts to have measure the effects of any ether model have failed. We have developed alternative models, such as the invariance of the speed of light, which are consistent with the evidence. Some, if not all ether models, imply Lorentz violation. Noether's theorem tells us that if there were Lorentz violation then we would see different effects if the same measurements were made at different places. Many other types of experiments have been developed to test this, again they are all consistent with the view there is no ether. So, on the one side we have zero evidence for the ether (and no need for it, apart from "common sense" which is equivalent to no reason at all) and large quantities against it. It is a reasonably good example of how evidence and science can show that common sense is wrong. But I think there are many better examples of how science progresses. For example, phlogiston was a good theory that matched the evidence available. So it was, for a while, a scientific theory (unlike ether). But then, as more evidence became available, it was clear a new model was required and it was replaced. However, these are both examples of ideas (one unsupported and one a good theory) that were completely overturned. That is actually fairly unusual in science. Most theories are just incrementally adjusted and improved as more information becomes available. And often, even when there is a better model, the old one continues to be useful (eg. Newtonian gravity). Which is partly why modern science is not considered to be about discovering "truth" or "reality".

Perhaps you could clarify what you are asking (the luminiferous ether or something else) and why?

Am I right in thinking that if the ring (case A) is uniformly charged, there will be no magnetic field created? Or is it equivalent to a current flowing through the ring? edit: On second thoughts I assume the latter; as spinning charged particle generates a magnetic moment

The Richard Nixon defence. I might have to report myself...

Which is why I asked the OP to clarify. I get the impression that is exactly what he is talking about. We have models that work. We have had attempts at models that haven't worked. We will (probably) have better models. That doesn't seem to be what the OP is talking about. Even if someone did decide to apply the label "ether" to some of those models. I don't know. I was trying to understand your motivation. Was it just about the history of science and how one particular theory came to be rejected? Or was it a plea to resurrect that theory? (We get a very large number of people who wish to do the latter and I have very little patience with it. I'm sorry if that made my responses appear abrupt!)

There was an initial assumption that if there were waves, there must be some sort of physical medium for those waves. That assumption turned out to be false. Another example of science winning over "common sense". Basically, we have detected something that we can describe using wave equations. Does that mean that mean the waves are real or just a useful description? "Physically exists" is a difficult concept that belongs in the philosophy forum. You could spend months arguing about the meaning of "physical" and then months more arguing about the meaning of "exists". When you have a 5 definitions of each, you then spend years arguing about which of those apply to the electromagnetic waves. And, if you take the quantum view, there are no waves at all. Just quanta of the underlying field. Does that field exist? Yes, because we measure its effects. No, because it is just a mathematical abstraction. It is impossible to say which of these is "true". We have new models that work. The ether model did not work. Ditto phlogiston, caloric, "plum pudding" atom, steady state universe, etc. As these models are not consistent with the evidence, they have been replaced with new models that do. I cannot understand why so many people want to go back to models that have failed. Some of them seem to have a weird romantic attraction; a sort of "steam punk science" aesthetic. Fine. But this is a science forum, not an "aesthetics of dead theories" forum. I'm not really sure how that relates to the concept of a luminiferous ether as a substance that pervades space. Obviously, many people have later used the word "ether" to describe other things: Einstein famously described spacetime as being an "ether" (because it is everywhere) much to the delight of the steam-punk pseudoscientists. They ignore the bit where he went on to point out that it could not be a material substance (ie. is not the luminiferous ether they were looking for). Others have used to word to describe one or more of the quantum fields that pervade space, etc. This is not a science discussion. It is a history of science discussion. Maybe you should go and cast a vote in the "should there be history forum" thread. I knew someone (or two people) would pick up on that. But it is important to note that the leeches are used for very different things. Which is a good analogy for the fact that wave equations can be used to describe the movement of material substances (eg. sound waves in air) but can also describe things that are have no material existence (eg. light or electrons, etc). Just because we use the same tool, doesn't mean we are clinging on to the old, discredited ideas of how things work. Let's turn this around. What reasons do you have for considering the ether? If there are reasons to accept this ether, I would also like to see that. What properties are you claiming for the ether? How is the experimental evidence consistent with those properties? What other experiments do you need?

In A, do you have a single charge going in circles, or a uniformly charged ring that rotates?

Surely, B results in two opposing fields that cancel one another? But maybe I am confused by your references to charge instead of the more usual current. Oh, OK. I see you have reversed both charge and direction. And you are talking about a uniformly charged ring? Rather than a moving charge? So there will be no field in either case. They both seem equally symmetrical to me.

Or are you thinking of caloric, another out of favour idea? While we are at it, maybe we should start s thread one why leeches and blood letting are no longer in use

The neighbour might be tricky. Especially if it is a dinosaur.

By ether, do you mean the old idea of the luminiferous ether? if so: 1. There is no evidence for it 2. There is no need for it 3. Why resurrect a dead theory? In our next episode: “phlogiston: why has it fallen out of favour?”

Well, I suppose that when any two surfaces touch, there will be transient, weak bonds like those mentioned by Sensei. And, famously, "every contact leaves a trace" (*), which means there must be bonds made with the exchanged material. (*) Locard's exchange principle: https://www.app.college.police.uk/app-content/investigations/forensics/#the-principle-of-exchange