michel123456

Maybe dinosaurs encountered fulgurant technological evolution and used coal and oil only for a few years (or maybe they were less in population number) and went quickly to solar power and wireless internet. That's why we found no underground cabling . ----------------- Or Maybe oil was emergent everywhere at the surface, as it is today in a very few places.

Particles do not obey laws. We humans have artificially extracted some "laws" that help us understand nature, make calculations and predictions. These laws are usually simplifications of what really happens (for example the laws of motion). As much scientists go deeper trying to understand what is deeply going on, the laws get more and more obscure. I guess one could derive the laws of motion of a macroscopic object from sum of all little quantum-foam-laws of each sub-particle, but in the end, if you go into calculations by this way you would do slower than nature.

Two different definitions and 2 different results: isn't that there are 2 "temperatures"?

The entire world is waiting.

I have a speculation: -Dinosaurs became intelligent and created a brilliant civilization that eventually came in contact with an alien race. After the third Worlds War, dinosaurs lose definitely . The alien race was so afraid of what happened that they tried to destroy anything alive on planet Earth. Better: they tried to sterilize it in order to avoid future disaster. The cheapest way was to spread huge amount of salt over the surface the planet (since salt was an element they could find on the planet) like the legend says the Romans did after winning over Carthage. That's why there is salt in the oceans .

I did that (i read it again but I am experiencing some difficulties to push my keyboards buttons with my elbow while having my fingers in my ears, fearing the noise of your posts in the dark) My opinion is that you are reading what you want to read and not the words that are written. I hope your opinion is the same: that Michel reads what he wants to read and not the words that are written. In the meanwhile, please do something for me: go read again your own post #26 and ask yourself about the followings: "the cosmological principle is extended" "the cosmological principle is preserved because ...." And the false assertion that: "a universe must be non-static if it follows the cosmological principle" Newton turns into his grave. Copernicus too.

(bolded mine) I remember a respected professor of mine arguing that everything from our civilisation will be lost in a few thousand years. The only thing that would last, maybe, would be the highways and only on places where huge change in the landscape are involved.

Here below my views: Change is tightly related to time. At T=0 you have situation A At T=1 you have situation B "change" is what we call when the same entity is recognized under A and B. For example you have an Apple and a Bed. Since the Apple and the Bed do not share an enough amount of common properties, we do not say that the Apple changed in Bed. That is common sense. If you take 2 Apples separated by a distance, although the 2 Apples share many properties, again we don't recognize that as a change, but as 2 different apples. The reason is not the fact that they are 2 apples, but the fact that there exist space between the 2 apples "at the same moment" 1.Now if you take the 2nd apple and put it exactly at the same place (and time) with the first one, you will realize that it is not possible. That is common sense too, but in physics it is a specific property. 2. In order to have "change", you must take only one apple and for example move the apple to new spatial coordinates. That is; you will have 2 apples at 2 different spatial coordinates (like in 1.) but at different time coordinates. That is a situation where you must care about recognizing carefully that it is the same Apple and not 2 different objects. (illusionists know about that) 3. Or do nothing, then the apple will have "moved" to new temporal coordinates. In the absence of any physical interaction, that would not be a change. But since all 4 fundamental interactions are acting over time, macroscopically we interpret the apple standing at rest on the table as a change. But maybe that is circular thinking. About birth & death, I think it is completely wrong. One of the most powerful law of physics is about conservation of matter-energy. What we observe is that we call "birth" is a transformation, and what we call "death" is another transformation. Applying both terms of 'birth" and "death" to physics should be an analog to "creation of mass-energy" and "loss of mass-energy", both of which are concepts that circulate here and there but do not rely on observation. IMHO.

No. Take it one by one. I am correct, Spyman is wrong. what Spy should have done is to follow the the POV of the Wiki talk page: that is to decide that the BBT is correct and thus put a question mark onto the CP, and not trying to conciliate the one with the other. 1. Following the BBT, we are living a SPECIAL epoch in between an extremely hot beginning and an extremally cold end. That is the reason why Krauss explains that "we are lucky'. There is NOTHING NORMAL in the epoch we are living because the Universe is EVOLVING, so the is no "normal" epoch. 2. Observers that are 'far from us in the present" are outside our light-cone. The concept of "far from us" includes the notion of time thanks to Relativity. The concept of 'far from us in the present" (which is in the basis of the CP) relies on the concept of an universal present time. I guess that is because the CP is an extension of the Copernican Principle at a time when nobody had a clue about Spacetime. In fact, "far from us" includes time, and since only the past is observable, the only part of Time that we can include into the CP is the past. Except if you come and explain that we can observe the future. 3. The Big Bang theory does state that the time and place determines what one will observe. Today here I observe the actual sky. Yesterday here the dinosaurs were observing a different sky. Tomorrow here in a few billion years we will observe a different sky. Somewhere else at a different time an alien was or will observe a different sky. ONLY the aliens that are upon our supposed "universal present" are observing the same things that we do. THAT is what the BBT states. 4. If there are many scientists that follow the mainstream, that is not for a surprise, that is the definition of "mainstream". I know that the collective judgment is that the Universe has been created and is evolving since then. The question is not wether the BBT is right or wrong. the question is wether the BBT is compatible with the CP. Because if the BBT is correct, there is something wrong in the CP, IMHO.

Wonderful, I didn't know it had a name. The talk page is better than the article. (bolded mine) Let the public judge about that.

That need some explanation.

(bolded mine) But gravitation makes things come together. And an orbit is not what we call a state of disorder.

I disagree with the Wiki article: it is an attempt to conciliate the unconciliatables. It is written: Bolded mine. The word "sequence" has been added artificially to the C.P. in order to fit with the BBT. There is no "sequence" word in the C.P. The BBT states that we are living in a special epoch of the Universe. It also states that all observers far from us (and thus in the past) observe different things than we do. BBT states that an observer on Earth a few billion years ago could observe a more dense universe than we do. The Theory also states that in the far future an observer on Earth will observe a universe more dissipated. IOW the BBT states that the place & time of the observer determines what he will observe. There are even some scientists that argue that in the far future an observer would see a totally different universe. (see below) From here: (Lawrence Krauss On 'A Universe From Nothing' January 13, 2012 1:00 PM) - Bolded mine. I don't consider that all this is compatible with the C.P.

Quite astonishingly, on the basis of observation, the structure of the universe never repeats itself. It is a very big tentation to describe the atom as a planetary system, or the reverse. Things don't go that way. If you go deep in the infinitely small, you discover other kind of structures than those you have in macroscopic size. And when you observe the infinitely large, you discover other kind of structures. So that from the very small to the very big, there exist no repetition. Galileo first observed that you cannot scale a horse and double its size just like that; the doubled horse would collapse. See a good small introduction here. As it appears, you cannot change the scale of things just like that.

A burglar at the appartment's door. The sign writes "BEWARE DANGEROUS PARROT" The buglar smiles, breaks the lock and opens the door. He goes slowly in the dark through the corridor when he hears from the kitchen "Wake up Rex, attack!"

Just found this old superb thread with historical answer from Martin (where is Martin?):

Now, going one step further, we know that velocity is relative: what my device measures is the same with what measures an observer upon the stone. IOW if the observer on the stone has to measure the velocity of my device, he will measure always the same velocity.

That is not the OP question. You are assuming that evolution will follow (or not) the technological progress. i am not sure. I often wonder maybe the ancients were more intelligent than we are.

So every alien we se today on billion of galaxies are observing a different (younger) universe than we do. The cosmological principle states that they should observe the same thing as we do, not "the same universe younger or older", but the same universe. In fact I guess (putting words in your mouth) that you assume that all those aliens are today somewhere else in other places and time where they observe the same thing than we do. But you are forgetting those other aliens that died billion years ago and for which the cosmological principle should work. Nobody has ever stated that the cosmological principle is valuable only in the same time frame. As a reminder: (from Wiki) The cosmological principle is usually stated formally as 'Viewed on a sufficiently large scale, the properties of the Universe are the same for all observers.' This amounts to the strongly philosophical statement that the part of the Universe which we can see is a fair sample, and that the same physical laws apply throughout. In essence, this in a sense says that the Universe is knowable and is playing fair with scientists.

I am on your side. I agree with you. I simply linked to another thread where it seems that your (and my) point of vue is not considered as part of mainstream science. Usually (Eddington aside) it is considered that there is an absolute dimension, that our meter stick does not change, that atoms have a size that do not change over time. As you do, I prefer to consider everything relative: as you said, if the universe expands relative to us, that can also mean that we are shrinking relatively to the universe. That changes nothing. But to quote AJB (*)2. the atoms (all elementary particles) are getting smaller and the Universe has a defined dimension. And Swansont:

My answer to Q1 is

So I had a thought about the following device: It is a shell of circular shape (A) with a small opening (B) and a small receptor C. The shell is rotating clockwise from Time 1 to Time 2. For the sake of the argument, the shell is made of steel and the receptor is a stone-receptor. For simplicity the stones follow always a straight path. The shell "understands" a stone only when it hits the receptor. If a stone enters the shell but does not hit the receptor, nothing happens. When a stone hits the receptor, bingo, a bell rings. So I am at point D and I have to throw a stone into the opening B so that it hits the receptor C. It is evident that the velocity of the stone must be a function of the rotating rate of the shell A and of its radius. If I throw a stone too slowly, the stone will not hit the receptor. If I throw too quickly again the stone will not hit the receptor. IOW the rotation rate of my device will give the only specified velocity that the device will understand as "stone" by ringing the bell. If 100 people all around throw stones in my device at random velocities, only the stones that travel at the specified velocity will be able to ring the bell. So I made a device that understands only and only one velocity. I guess there must be other ways to obtain a similar result. For example one can replace the B orifice with a 2nd receptor and make the bell ring only when both receptors understand the stone. In this case the shell can vanish.

The aether again. IIRC Mendeleev had reserved a place for aether in his periodic table. But so far no aether is needed to explain physics. On the other hand the question "what is space" is very interesting. But not in the sense that space could be some material thing. Space alone means nothing. Space AND time means something. Since it has been established that time & space are so tightly linked in such a way that what one observer call Time another observer call Space, it should be obvious that time & space are interchangeable (I call that rotatable). Would you ever imagine that time is a kind of material thing? A kind of Aethertime? I don't think so.

Bolded mine. Say you are living on that planet 13 BY ago. You say that a galaxy that is 0,04 BLY from you emits a ray of light. This ray of light will reach you in 13 BY (and not in 0,04 BY) You are observing a quite different universe, aren't you?

Bolded mine. So you say that an alien 46 BY away does not see the same thing in the sky as we do. That is in contradiction with the cosmological principle.