michel123456

It is a geometric construction on how to draw a perspective drawing of a serie of objects (here, cubes positionned side by side with corner down). There are 3 parts: the down triangle is a horizontal plane projection. the left triangle is a vertical section the center part with the green ABCDEF schemes are the final result of the drawing, the perspective view. _At the bottom you have your eye. The horizontal red line is a representation of a vertical screen (say a sheet of paper) on which you will draw the perspective. _on this line are positionned several objects you will have to represent in perpective view. _the lines going from you eye to the objects indicate the projection of the corners of the objects upon the screen. _at left, you have your eye again. the vertical red line is the vertical screen again (distance from eye to screen is the same in both plane & section view) _the square (like losange) represent the serie of objects in vertical section (all objects superpose one another in this case) _the lines from the eye to the corners of the object intersect the vertical screen. _the central part is the combination of the plane & vertical projections, the perspective view. _the bunch of lines going from the green representations, up & down, are the constructions lines of the angled sides of the objects. They all join to the vanishing points up & down. The vanishing points are found drawing parallel lines to the sides of the objects, from the eye to the screen. I hope that helped, it is not the simplest example of perpective drawing. The original question was: from HERE "Behavioural studies show that many avian species focus on distant objects preferentially with their lateral and monocular field of vision, and birds will orient themselves sideways to maximise visual resolution. For a pigeon, resolution is twice as good with sideways monocular vision than forward binocular vision, whereas for humans the converse is true.[1]" source wiki http://en.wikipedia.org/wiki/Bird_vision If you move towards an object looking at him sideways, your path will be a logarithmic spiral. I guess that's what the "behavioural studies" tend to show. But if a bird looks sideways, it is probably to avoid the phenomena described by dalgoma, not to use it as a magnifying trick. In short, binocular vision is great to get a steroscopic image which helps on estimating the distance, but monocular vision is much better to focus. If a bird need to focus, he will obligatory look sideways. After approaching, a bird of prey will return to binocular vision to attack, since only by this way he can evaluate distance correctly.

My post was addressed to dalgoma. You made your point, Tony.

Here (in Greece) we call that effect "paramorphosi" (παραμόρφωση) and it is real. I use almost the same method than yours for perspective, which I have learned from a Greek Architect who learned it from his Greek teacher in Alexandria of Egypt. We don't use the section. We put the heights in full scale on the perspective at the intersection of the object with the projection screen. I don't know about the hawk, I guess with 270 degrees, his world is quite different from ours.

It is not because cups are positioned left or right of our centre of vision, it is because our axis of vision is not parallel to the plane of the circles.

Lemur, you are talking like a priest.

There is no need to be an expert in everything. The point is that you can be an expert in lets say mathematics and still have basic knowledge to change a light bulb. In my job (I am architect), I must have to know the basics of mathematics, physics, legislation, chemistry, geometry, geology, geography, history, history of arts, history of cities, town planning, climatology, semantics, politics, philosophy, air conditioning, philology, etc. without being an expert in any of these. But because I know something of all these, and I have learned as an extra how to use my mind wide open in order to take a pencil and create (that's my field of expertise), I can do a job no other can do, except another Architect of course. And as a feed-back, I must be able to understand, estimate, judge and even correct an electrician, or even a geologist or topograph, who didn't made his work correctly, without being able to do his job. The same way as you may be able to judge your car or your computer without being able to construct it. So you must understand that I cannot understand how it is possible that my friend Doctor of Medecine don't know how to properly put a fork and a knife on a table. Not to mention his ideas about religion, if he has any. I don't understand the diagram.

It is the philosophy of Sherlock Holmes, who didn't want to know about the Moon revolving around the Earth because it has nothing to do with his profession. IMHO it is an abomination. It is exactly the opposite of the Renaissance Man, a lost dream we have an urgent need to recover. There is a common concept that states that we have only a few drawers in our mind. When those drawers are full of knowledge, you must keep it safe from invasion of useless random information. As a consequence, people well educated avoid or refuse information upon subjects that have nothing to do with their beloved discipline. IMHO it is mental sclerosis. There is always room for new knowledge, drawers are never full, and you can create in your mind as many drawers you whish, the only thing you need is interest. If you are not interested in the first place, you will never learn.

In this case, it is not a question of religion or belief. There is no profound quest to investigate here. It is a question of intelligence or stupidity. I agree. I am tired of people who find these attitudes excusable. If you have a mind, and you can use to make physics or mathematics, why don't you use it for such simple things? IMHO, to not use your intelligence is a crime.

I am with you BH123. There are no excuses. Don't listen to excuses.

No, I don't think so. The horizontal 13,7 Light Years is a time, not a length. This time corresponds to a distance of 46,5 billion light-years following Wiki. The extended shape of the diagram is an indication of the expansion, because under normal circumstances (without expansion) a time of 13,7 BY should correspond to a distance of 13,7 Light years, and not 46,5 billion LY. So I think for this part the diagram is correct. But IMHO the diagram is misleading for other reasons. 1_the diagram does not represent the entire Universe. It represents only the evolution, following the Standard Model, of our Observable Universe. The whole Universe is probably much bigger. In other words, the black surrounding of the diagram is most probably full of stars & galaxies. The diagram is misleading in the sense that any kid looking at this diagram will immediately conclude that the Universe has boundaries and is finite although it is a question still under investigation. 2_The diagram does not represent the Observable Universe either, but the sum of all stages of evolution of our Observable Universe following Standard Cosmology. Our Observable Universe in this diagram is the surface of a cone with the basis upon "Afterglow Light Pattern" and the summit at WMAP (which is the observator). Our current Observable Universe is only a tiny part of the diagram. It is misleading in the sense that anyone looking at the diagram may believe that we are currently looking at all this stuff, and it is not the case. (for example WMAP can not observe anything that lies in his own slice of space). 3_It is a space-time diagram. Space is represented as a succession of disks, growing from left to right (like a salami). The representation of WMAP should be flat, and not 3d, and all galaxies should have been represented aligned in space, flatten upon the disks, in order to clearly show that each belong to a specific slice of space. It is misleading in the sense that the whole diagram looks like a 3D shape with a volume, and it is not the case, because volumes here are represented flat. 4_the length from left to right of the diagram is time, not distance. But it represents also the radius of the sphere of the Observable Universe, so in this sense, it represents distance also (see the OP question). Because it is a space-time diagram, a radius is not represented as construction part of a shere, but as a height as in a triangle. It is misleading because anyone looking at information about the Observable Universe will take the answer that the O.U. is a sphere, and not a cone or a diagram like this. 5_anyone looking at the diagram can ask the following question: what is happening on the left side of the Bang? In other words, what was before the Big-Bang? Many scientists struggle with this question, and no-one who have seen this diagram will easily accept the answer "there was nothing". So it is misleading in the sense that it raise uncomfortable questions. 6_ the same anyone may ask what happen on the far right side of the diagram. In other words, what is the future made of? Are there already stars & galaxies there, does the future already exist? Also an uncomfortable question. Following Standard Cosmology, there is nothing on the right of the diagram. Everything stops at our present time. With all respects to the NASA team who produced this diagram in the good intention of instructing people. It looks like Lie To Children. I suppose that any diagram of any kind may raise questions & misinterpretations. Besides, I may be the one who is wrong.

From your last post I understand that the short answer to my question is: "it is not what we are observing".

Where is Bascule?

You just won the game.

Correct. Something before the invention of Bluetooth.

what I am trying to say is that, when Martin says in the beginning of thread: (from post #5)and I am thus trying to say that we should observe the same thing today from the Earth concerning objects farther than the distant galaxy. We should observe today an increasing density of galaxies as much we look far away & into the past.

That's the point. We are witness of the same events. If you whish to calculate today's position of these galaxies, yes of course you are right, you would not calculate the same distance between those galaxies because there has been additional expansion since then. But if we are talking about the events we are looking at, these are exactly the same events in the same place, and in "real time". The events we are looking at now were observed by the Distant Galaxy then exactly the same way. Expansion of space don't play role.

That is part of the content. See it as an exercise. We have a new member who posts for the first time. And he says goodbye as he was another member. what do you think?

O.K. You are right in all you say. What I try to say is that one side of the past "triangle" of Distant Galaxy coincides with a segment of our past triangle. I have a problem in expressing my ideas properly. Do you agree with the following sentence: The relative position of galaxies X,Y,Z as seen today from the Earth today is the same as they were observed from Distant Galaxy then.

Upon the last picture, here is what is happening: 7 It is not speculation, it is really what we learn from physics. So, a form of scale factor, which is observed by us through common perspective view, is also an indication of the flow of time. I say that without clearly understanding what it means, but that's the way things seem to go. If I made any mistake somewhere, please correct me. Of course, one may say there is nothing weird happening, be cause what I call "past" is not "my" past (i.e. I was not in the past standing in the end of the corridor). It is simply an indication that the speed of light, which carry the image I get from reality, takes a certain amount of time to reach me. So, nothing is bizarre, everything is normal.

Yes. When you double the size of each side, ou quadruple the surface.

I couldn't find the exact place to put this topic. It's about geometry, but also about the way we observe objects, and space more generally. In another thread, I made a comparison between a flat 2d diagram representing the expansion of the universe, and a perspective drawing. Of course, the answer was "it is not a perspective drawing". Which is undoubtedly a correct answer. But there is a common point, which is the scale factor. Explaining. Lets take a simple square like the one here below: 1 Lets put a scale factor of 2, and approximatively double the size of the square, and lets represent both squares side to side so that we can compare: 2 We have the result of the operation "scale". Now, let's join the corners of the 2 squares. Something like this: 3 Fig. 3 here above is a perspective drawing. when you extend the Grey lines, they join to the vanishing point. 4 The vanishing point can be anywhere you want, even inside the square, like in the following fig. 5 And of course, it is equally a representation of a scale factor. Which means that in our everyday life, when we look around us, we see the living image of a kind of scale factor. The same counts for picture we get looking at the stars. Perspective always count, even without Earth's horizon. My point is that what we understand as an image of 3d space can also be interpreted as the image of a scale factor. The geometric laws that apply for both are the same. Perspective is a geometric construction, scale factor is a mathematic one. The result is the same. 6 there are much better pictures on the web, but they are all copyrighted. a link I liked:

You're very kind.

Well, some may say I am the peculiar guy... I read the goodbye post of Bascule. I don't want to discuss the content. I just wondered, why did he login under a new name? This post was not from Bascule, it was from a new member named "Goodbye Bascule". Did Bascule forget his password? Was Bascule banned? (Bascule has a 723 reputation score, and is member since April 2005). Or is this imposture?

If you were chosen for a time travel, would you take your cell phone with you? As mentioned before, there were no cell phone providers at the time, no emitters, & no receptors. It is simply ridiculous. Why do we have to prefer the most incredible explanation? Something in human mind drive people into mystery, and people like that. When someone comes and cancel the whole setting with a simple explanation, he is the bad guy. Mystery is better, even if it is complete nonsense. What a pity.

Hm. You are too educated to misuse poise for poesy. You certainly meant poise. I am not sure viewers using foreign language understood your post #45 properly. I voted for your post #41 too. It was nicely said. I use this forum to improve my english as well. I learn a lot here, good & bad. Usually good. I waste a huge amount of efforts reading my own posts and correcting, 2 or 3 times, often more. And I still make mistakes.