Strange

But the former example is for objects in a line: A -----> B ---------> C ----------------> Where I agree that the distance between them will increase. But you are talking about things side by side (Scenario 1): A ----> B ---> We are on A we look at B and (as you say) we will see it as it was in the past. So we should see it having a lower velocity than it actually does now. But it is travelling parallel to us. Why does it look as if it is moving away? Now, I can see that you might argue that we will see it fall behind because we are seeing it when it was moving more slowly. So after a while we see (Scenario 2): A -----> B ----> BUT... 1) We don't see distant galaxies moving, we only see red-shift. There would be no red shift when the galaxies are next to each other (Scenario 1) 2) I don't believe (and you need to demonstrate) that this effect would be the same for galaxies to the side of us as it is for galaxies the same distance ahead and behind us.

How do you know it is incorrect? I will assume that by "known universe" you mean "observable universe" (rather than the fictional worlds created by Larry Niven ) In which case it is entirely possible (but not known) that the "big bang" does not include the entire universe. We have no way of knowing. However, it seems very unlikely that the big bang is just the observable universe. That would put us in a very special position in the universe, which seems improbable.

No. That is why I keep asking you to explain why you think that.

You haven't explained. You have just asserted it as a fact. Done that. Logic tells me not to jump to a conclusion without evidence.

But we are talking (I thought) about two objects falling side by side and therefore with the same velocity (at any instant). (Obviously if they have different velocities then they will not stay the same distance apart. But that does not appear to be relevant.)

I think I might be getting where you are coming from with this. When you look at the raindrop or galaxy that is at 90degrees to the direction of fall, you will (because of light delay) actually be seeing one that is slightly ahead of you and therefore falling slightly faster. However, only a proportion of the extra velocity will be in the direction away from you because it is at some angle to the direction of fall (a bit of vector maths required there). So it looks like you need to show that this preserves an isotropic speed-distance relationship. (I'm betting it doesn't. But I am not going to do your maths for you.) However, there is an analogy between the free fall example and the increasing separation due to "expansion of space". They both examples of increasing separation in the absence of any force. But the former is not isotropic because it happens in curved space-time, whereas the latter is isotropic because it happens in flat space-time.

There is a third possibility (I don't know if it applies in this case - it may only apply to axioms). An axiom may not be true or false; it could be a choice. For example, Euclid's 5th postulate was assumed to be true for thousands of years, until someone realised that you could make other choices and invent/discover alternative branches of mathematics.

But that introduces the problem of potential energy on the Moon or Mars. So, conventionally, 0 is taken to be an infinite distance away (hence gravitational potential energy is negative). But we are getting off topic...

Logic is a branch of mathematics. So it isn't real (according to you).

No. It seems a completely random claim. I see absolutely no basis for it at all. And we are not talking about random velocities, but two things moving side by side at the same velocity. What, exactly, will make them appear to be moving apart? What mechanism are you suggesting? The maths that shows that they appear to be moving apart, even though they aren't. (And that the speed of this apparent movement is proportional to distance.) So you keep claiming. If it is so obvious, why

True. But that is true to some extent for all science. Cosmology is, perhaps, a more extreme example. Well, its no inappropriate data; the observations we make are the only data we have. All models/theories that attempt to explain the universe need to be based on that same data. There have been (and are) other models that attempted to explain the evidence. Currently, none of them fit ALL the evidence as well as the big bang model. As ar as the model is concerned, this is general relativity which is extremely well tested in every way we can think of. Many of these are far more direct that these observations, which you are doubtful about. So any explanation needs to be consistent with GR. Having a universe that doesn't expand (or contract) is a big problem in that respect. It has come up on this (and other) forums before. And other people have given far better answers than me! If you want to get really good answers, possible from people actually working in the field, I would recommend the Cosmoquest forum. (There are some experts here, but not as many or as regularly.)

Fair enough. But these are the sort of things you should consider when you come up with a new idea.

The thing is, what we see is the relationship between the distance the objects were at the time we see them and the (apparent) velocity then. So the most distant galaxies we see, which appear to be about 13 billion light years away are now actually about 46 billion light years away (and receding even faster). But when the light we see left them, they were only about 4.5 billion light years away. Also, the apparent recession of galaxies is not really caused by their movement, but by the scaling of the distances between them (a subtle but important distinction). This means that the relationship between distance and velocity is purely a matter of geometry - you can demonstrate this for yourself with some simple diagrams - and nothing to with cosmology. If all of that sounds confusing, it is because this not a simple concept and the only way to really get your head round it is to understand the math (which, I happily admit, I do not fully!) However, you are right in that it is entirely possible that stars a billion light years away could have reversed direction, exploded, danced a jig or turned to chocolate and we wouldn't know for a billion years. But what we do have are models based on what we can see. These models make all sorts of predictions (e.g. the nature cosmic microwave background, the primordial proportions of elements, etc) which can all be tested. And, so far, the predictions of the model stand up pretty well. So, until there is evidence to contrary, it is thought that the most distant galaxies are receding at ever greater speeds.

There are people who understand it could be. They are also intelligent enough to realise that it might not be, and that they need evidence to decide. But it does seem that there are some people who are not smart enough to realise that things are not necessarily true just because "common sense" says they should be.

At the risk of repeating myself: why would this make them look as if they were receding? It is no use simply repeating that it would. You need to explain what mechanism is involved and then show the maths for how you calculate the speed at which they appear to be receding.

And, of course, there is the possibility that the universe is infinitely large and infinitely old ...

It would be very easy to work out (but I am not going to do it for you). Well you might say that, of course delay is proportional to distance - because the speed of light is constant. But hang on, no it isn't: because the universe is expanding, it takes proportionately longer for light to get to us from more distant objects. And you still haven't explained why the raindrops (or galaxies) either side of you would appear to be receding ...

There are a whole class of models like this. I have even heard mention of the idea that this continual process could allow the laws of physics to have "evolved" (thus solving the "fine tuning" problem - if there is such a thing). This could mean that the universe is infinite temporally (but doesn't require it) but still says nothing about the universe being spatially infinite or not....

"What did you study at university?"

Could provide some support for this claim? Why do you believe it? And why do you expect others to believe it?

Maybe. If you mean that they are all moving on the same path, one behind the other, then yes. But: 1) That has nothing to do with what I was asking. 2) In the case of free fall, you haven't yet shown mathematically that their speed of separation is proportional to separation distance. But I am happy to leave that for the time being.

Isn't that what the quoted bit from ajb does? (Attempts to do?) I agree that nearly all such questions really centre on the meaning of the word "real" (or "exist", etc.) - and there are several live threads on this at the moment, with regard to various things, from numbers and the quantum wave equation, to scientific theories in general. It is worth worrying about when the two (or more) sides in a discussion have different assumptions about what it means and so may be in violent agreement.

A couple of questions: what problem does this solve? If everything we think of (which presumably means everything we see and hear?) is in another dimension, how is it any different from those things being in this dimension? Also, what evidence is there that does (or could) support this hypothesis? More precisely, what tests would show it to be wrong? (This is the key question you should always ask yourself about any such hypothesis - it is the basis of a scientific approach.)

There is a problem deciding where we stop thinking of our observations (measurements) and conclusions as "models" and when they become descriptions of "reality". Common sense tells us that the subjects of geology (whether a grain of sand or a mountain) are real while the status of electrons and, even more so, quarks is less clear. But I'm not sure that common sense view can be rationally defended. For example, how can "real" things (a grain of sand) be made of things which may not exist (quarks). And when it comes to things like the internal structure of the Earth and even plate tectonics, we only have indirect evidence. So does the Earth really have a solid iron core surrounded by a liquid outer core? Or is that just a model? And how can we sure that the way we perceive a mountain represents reality; all we have to compare it against is our own perceptions. Even "objective" measurements confirmed by others are only available via our perceptions (hearing or reading their results). So we don't have any direct access to reality; we only have our measurements (taking that to include informal observations, such as looking at things). I am a naive realist: I believe that when we see a chair or a mountain, or even data suggesting the existence of quarks, then that is what the world is really like. But I also know that this position is as logically unsupportable as arguments for (or against) solipsism. (And, just as an aside, "Those members, however, seemed committed to the view that all of science is like that" was a strawman created by SB.) Interesting question. There seem to be two meanings to "having no answer". One is cases like this where the "facts" exist (he did have something, or maybe nothing, for breakfast) but not accessible to us. The other case is where the answer doesn't exist (the question has no meaning), such as "which path did an individual photon take".

So you are repeating that strawman even when it has been carefully explained to you? But you seem to have largely ignored most of the responses to that and kept banging on about atheists.