Strange

I meant, "This is you in 1 spatial dimension". Sorry if that wasn't clear.

I don't see the logic of that. It depends on the definition of "real physical object." For example, I could define a "real physical object" as one made of atoms. That says that electrons are not "real physical objects" but we are still real. So, the problem is not the existence of photons or other particles, it is what is meant by the question. Until the terms are defined, no meaningful answer is possible (or, equally, any answer is possible). We are not made of electron-positron pairs, either.

It is not clear that an electron is a real physical object. But this depends what, exactly, is meant by "electron", "real", "physical" and "object". You can, if you wish, define those terms in such a way that a photon is a "real physical object" and an electron isn't. Or vice versa. Or both. Or neither. It doesn't really matter. (No pun intended!)

This is a bit counter-intuitive, I suppose. It puzzled me when I was young. One thing to note is that we are dealing with pressure. This is force (weight) per unit area. So the area is already (implicitly) taken into account. If you expressed the equation terms of force (not pressure) then you would need to include area in the equation. But then you could simplify it by replacing force/are with pressure. Back to square 1! (And, actually, I'm not sure how you would get force, other than multiplying pressure by area. And then the area would just cancel out.)

True. And I suppose another observer might consider your head and feet to be at different times from their frame of reference (although I struggle to come up with a suitable scenario). But from your own frame of reference, your head and feet are both in your that frame and therefore at the same time. (I think!)

Thanks for the explanation. I think I see what you are saying now. This is an interesting analogy (*) and is, ultimately, the reason that people assumed there was a thing called the aether that light and similar things took place in. The problem with your analogy, is that you are trying to say (I think) that there is no need for a materiel "thing"; that these properties, spin, momentum, etc can exist as a vortex which is not an object itself, Unfortunately, your analogy only works because you are embedding your vortex in a material thing; the water! (This is a bit like holes as charge carriers in a semiconductor - the hole is "nothing" but it requires the bulk material for its existence.) But on another level, I think your analogy does work. The photon is just a quantization of the underlying electromagnetic field. The electron is a quantization of the underlying electron field. And so on. In each case, you could consider the field as the water. (As long as one doesn't take that analogy too far.) (*) Although not as interesting as this: http://physicsworld.com/cws/article/news/2012/jul/09/bouncing-droplets-simulate-zeeman-effect http://backreaction.blogspot.de/2014/02/a-drop-makes-waves-just-like-quantum.html http://phys.org/news/2013-10-strange-behavior-pilot-wave-dynamics-action.html

That doesn't appear to make sense. If "proficient" is above "average" then it is, by definition, above average. Unless you live in Lake Wobegon, "where all the children are above average".

Can you explain what those photos are supposed to show. It looks like a swimming pool. With some shadows and arrows. One arrow appears to be pointing at a line (the edge of the pool?). The other appears to be pointing at the shadows of trees? Or the shadow of something round? How does this relate to photons? (Apart from the fact the image is created by photons, of course). I assume it makes sense to you because you know what you are looking at. As I say. That depends on your definition of "thing". Obviously photons are not material objects. Does that mean they don't exist? I don't know. And I don't care. That is a purely philosophical question (mainly dependent on the meaning of the word "exist") and of no interest to me.

There was no mention of, nor need for, any such aether. Imagine you and Michael are floating alone in space. You are also drifting apart slowly. The two of you are tossing a ball between you and, because there is nothing else to do, timing how long it takes. Because you are drifting apart, the ball takes a greater time to travel the distance each time you throw it. Does that require "aether" to explain it?

Because the distance between them has increased. In the past they were closer together. That doesn't seem too hard to understand.

The same is true for time. An object can be extended in space and it can be extended in time. You are extended through time for as long as you exist. You are extended in space for as long as you are ... long. The last two diagrams show a little snapshot of a short period of your life. In the first you are standing still so your spatial position doesn't change. In the last one your position changes uniformly over time. Your head and feet are always at the same time. They are observer dependent.

That means they are at different point in space, not time.

It is because water can pour out of the bottom and let air in. If the tube is narrow enough, then there will be sufficient surface tension to stop this happening. I have no idea know how one would work that out, but it may involve surface area...

Sorry, davidivad, I'm not sure what you are trying to say. My fault I'm sure.

Well, there is energy, momentum, angular momentum, frequency, ... But whether those things are "real" and whether photons "exist" depends largely on what the words "real" and "exist" mean (more than it does the word "photon"). And that is really just a philosophical point, of no real relevance to science.

Why? The light has taken 13.3 billion light years to get here (because of the expansion of space).

(Actually, the furthest galaxy seen so far is about 13.3 billion light years away.) At the risk of confusing you further, those galaxies were only about 4 billion light years away when that light was emitted, and are now about 40 billion light years away.

In the classical case, it is the result of splitting up the wavefront. But photons and electrons do not have a "makeup"; they cannot be split; their is no "piece which is not the full particle". Because they are quantized. (A word you should be familiar with ) I don't understand. Why would photons behave any differently? Obviously, any one photon can only hit one point on the detector. But a number of photons would be evenly distributed across the detector in the same way that a wave is (and they would all take the same time from slit to detector).

You may prefer yours, and they may prefer theirs. Which is why neither is absolute. An absolute frame of reference would be one that you, I and the Andromedan (and everybody else) agreed was somehow unique, special, and ... well, absolute. Compare with temperature for example. We have various scales with 0 degrees at different places. For Celsius it is conveniently chosen as the freezing point of water. For Fahrenheit it is chosen as <I have no idea what>. But these are just arbitrary conventions. But we also have Kelvin where the zero is absolute, not just a random choice. Everyone in the universe would agree that 0K is a unique, special, and absolute zero of temperature. And, as our local cluster moves through space, that "absolute" direction would change making it, again, just a randomly chosen relative direction. No one else in the universe would see any special significance to that direction over any other. An absolute velocity, direction or position would need to have some measurable characteristic that made it uniquely different from all the other possible velocities, directions or positions. Yes. Unless that person had some truly extraordinary evidence. If so, that would be a totally world-shattering discovery that would get them not just a Nobel prize but worldwide and eternal fame! That is why you should not misuse specialised words (jargon, terms of the art, etc) to mean something different.

That was a statement of my understanding of what you have said, in order to provide context for the following question (the one with a question mark at the end). I am reassured that you handle the math in the same way, but that wasn't really the question. OK. This sounds quite different from what you said previously. You seem now to be saying that any units (volts, metres, Planck units, etc) can be subdivided as necessary to do any measurements or calculations required. Is that correct? If so, then your focus on the use of units of measurement is nothing to do with quantization. The meaning of this word may be the only point of difference. You appear to be using it to mean quantification. If something is quantized, then it means you cannot divide it into parts. So photons are quantized, energy levels of electrons in an atom are quantized, electrons are quantized. But, as far as we know, length, time and voltage are not quantised. We measure them in appropriate units (whether metres, seconds, volts or Planck units) but any of those units can be subdivided as necessary in order to measure smaller quantities. Can we agree on that? You seem to confusing maths and numbers. Maths, especially the mathematics of GR is not just continuous because we think space might be continuous, the mathematics of GR must be smooth and continuous or it doesn't work. The fact that it does work as well as it does, suggests it is an accurate description of the nature of space and time (i.e. smooth and continuous). So, after appearing to agree, maybe we don't after all. There is no evidence that this is the smallest unit of time. You could choose a different units that was smaller. You can subdivide the units of Planck time. If you can divide it, I don't understand in what sense it is the smallest unit. The milliplanck is smaller (even if not widely used). It can be approximated, not described, by 22/7. It cannot be described by any fraction. I assume you are referring the word "quantized". So this entire argument is due to you deliberately misusing a word to cause confusion? Well, thanks a bunch. That is most kind of you. (Where I am not using the usual definition of the word "kind".)

Whoa! Hold on there. Light is theoretically, and as far as can be determined by experiment, massless and therefore travels at the speed of light.

Thank you, thank you. But I think we can all agree that at any instant it is not extended in time.

Actually, you seem to have that the wrong way round. Atmospheric pressure would keep the water in the cup ... until the cup got really big! It is easier to test this by putting a filled bottle under water and slowly pulling it out (with the opening under the water). You can see that the water stays in the bottle. The pressure caused by a column of water is density x height x g. If this pressure is greater than air pressure then it will no longer be supported by the atmosphere and you will get a gap at the top (which will actually be a vacuum). This requires a tube about 10 metres high so tricky to do in practice. Easier with mercury, which only requires a height of about 1 m. http://onlinephys.com/pressure2.html

And maybe start with some questions to establish the level of your audience. "You know how ... ?" a. "Yes" "Great. So what happens here is like that but ..." b. "No" "OK. Well imagine you have ..."

You're welcome. I have no idea why you find my usual style of asking questions so offensive. I assume you don't like brevity, in which case I will try to more verbose. But as a professional writer that comes very hard to me. Does that mean January? But that's OK. I can wait. (I am highly impressed you managed to write 400 words repeating the same statements, but were unable to find time to write 3 or 4 sentences answering my questions. Nor problem, though. I am not impatient.)