michel123456

What is wrong with this? You can draw the world lines like in the previous diagram, and it fits. You can draw other world lines, and it fits too. The Earth is nowhere, lost in the universe. It is not upon the axis, it is not at the edge. IMO it looks O.K. The Earth is also nowhere in time, completely nowhere, not at some peculiar moment from the beginning. It makes some sense to me. From any object (event, point) of the diagram, you can draw a similar light-cone. Every point will have about the same view of the universe. It makes sense to me. The mass of the universe is much larger than what we can see. That is not bad IMO. The only catch is that it doesn't fit with the BB theory, I must admit. But that doesn't mean that "stars randomly pop into existence, emit some light, and quickly disappear." IMO there are other possibilities, but to get into this, we will slide into speculations. So I prefer agree with you and admit it is all wrong. I had the chance to discuss seriously about all this, and that's enough to me.

At least, 2 other people agree with me that the event Y is not observable. Not too bad. Spyman wrote: IMO it is difficult to do that. All that we are observing are only events. Here below is another draft diagram of what we are observing: We are observing events ABCDE & abcde. All the rest, the life-lines, the Bang etc, are deductions & theories. We are not observing the event Y. Quite an empty diagram, isn't it? The observable universe. ------------------------------ From the above diagram, we have to explain something that looks like this: That is not the observable universe any more. It is the Universe.

Well I have to admit you Iggy & Spyman made some points. I made some diagrams of your point of vue, and they make sense. I am taking back my proposal for dark matter, it is not compatible with the Big Bang Theory. If all matter-energy that makes up the Universe has been created at a single moment in the past, and if no matter-energy can be created or destroyed since, you are right, and I am wrong. But I still find intriguing that the universe we are looking at in our telescopes is collated upon the surface of the light-cone. We cannot see anything outside neither inside the light-cone. ---------------------------------- Here is a draft. Looking around us, back in time, upon our light-cone we see ABCDE. Today, ABCDE are in the present (tautology), they are upon the horizontal line, and not where they are observed. And we declare that X and Y do not exist, because we cannot see any of them.

Iggy, it is a pleasure to discuss with you. The world line gives a width to the light-cone. The width is not given by the object, but by the observator. When we see a star, we know that it existed yesterday, and that it will exist tomorrow. We can draw its world-line by some approximation. But we cannot do the same for an object we have never seen. At the scale of the diagram, the length of humanity's life-line (lets say 10.000 years) is equal to the width of the line you drawed. From the invention of telescope till today, only 500 years have passed. At this scale, a line of 500 years width is thinner than a hair. At the scale of the universe (say 12 billions years), the line-life of the Earth (4 billions years) is only a third. So, even if we were able to collect all the information from the birth of our planet till now, we woud collect only a third of the universe's information. Now, if you believe that the only mass is the mass we can see & observe, put yourself at planet B in your diagram, and draw the new light-cone from your new point of vue. You will observe the universe differently, isn'it? You will see other stars at other places. The same that we are observing today? That's the question.

What are those "other methods"? _Nothing can travel faster than C. (It concerns what is outside the light-cone) _Electromagnetical radiation is condamned to travel at speed=C (that is the surface of the light-cone) _Gravitation travels also at speed = C. _Only matter can travels at speed less than C. That concerns what is the inside of the light-cone. So, the only method of observation available to investigate the inner part of the light-cone is to collect matter. The only & most usual matter at our disposition is the Earth itself, and some rare asteroids. Most other material elements ,galaxies, stars, planets, gases & plasma, are detected through some radiation (see above). Neutrinos travel at speed near C. What else? If you put all the above upon a diagram, you will see that the observable parts are close to the surface of the light-cone, except Earth's life-line (the vertical DC axis in your diagram). All the rest is not observable. My point is, the Earth past light-cone is full of regular matter that we cannot observe. That means, for us, the light-cone looks empty. You can plot into your diagram a lot of other stars like A, inside the light-cone, that are not observable. All the observable objects placed upon the surface of the light-cone are influenced by those non observable stars, made of regular matter, hidden in the past. So, maybe that is dark matter. Not hidden in space but hidden in time.

Square?

Iggy, you are not following my thoughts, you are preceding. Marvelous. Light does not follow ABD trajectory. Light coming from star A follows AC. (& AB) From our point of vue, at D, we cannot see the exploding star. Point A is INSIDE THE LIGHT CONE and is not directly observable. that's what Sisypuhus meant when saying in his previous post "behind the leading edge" is "inside the light-cone." Merged post follows: Consecutive posts mergedAnd from point D, we are not able to see point C either. Point C is the Earth's own past and is not currently visible. But that is not the important point. The important point IMO is that A (the exploding star event) and B (the planet) are related through EM radiation & through gravitation, since it has been demonstated that gravitation is transmitted at Speed Of Light. In other words, the effect of A upon B can only be interpretated by us through some effects on B, and not by observing directly A, because A is hidden "somewhere" inside the light-cone. An effect comparable to the definition of dark matter.

Sure. Your post means you have understood my thoughts. Thank you for your observations, and sorry if I missed the correct words. Now, i think we can all agree that we can see a planet placed in the past 1,5 million years ago, & 1,5 million LY from us. There is no trick, it is a simple standard planet like many others. says Law. The point is this: Taking my telescope and looking at that distant planet, 1,5 million LY away (& thus as it was 1,5 million years ago), I am astonished seeing my E.T. friends (the inhabitants) looking in their telescopes too. They don't look at me. They are actually observing an event I cannot see. They are observing an exploding star, positionned relatively to me 2 millions years ago, one million LY from me (the star of my first post). That is more difficult to understand. I'll try to explain.

We would see in the mirror what the inhabitants of such a planet were looking at: we would see the Earth 1,5 + 1,5 = 3 millions years ago, roughly speaking. -------------------- Hm, editing. We would see a portion of an image of the universe as seen by the inhabitants of this planet at that time of the past. If the mirror is flat & oriented to us, we wouldn't see ourselves 3 millions years ago, but we would see the object that was positionned at our actual coordinates 3 millions years ago, i.e. probably another planet or simply nothing.

I agree, Sisyphus. Information is not lost. I will keep your interesting light cone observation for later discussion, if you don't mind. Now, other question: Can we see (today) a planet placed in the past 1,5 million years ago, & 1,5 million LY from us? (please try a simple answer, like yes or no)

Sisyphus is right on everything he writes, and he knows my point from older posts. He thinks I am wrong. So I have to take the question otherwise. All that stuff mentionned by Spyman is too complicated in comparaison with my purpose. Forget the star. Take a pencil, and let it fall down the floor. Then pick it up, and put it upon the table. Now, can you see your pencil falling down? The answer is no. You cannot see it NOW, you saw it, in the past. Now the pencil is upon the table, and you can take the remnants of the pencil in your hand. But you cannot see the past event of the pencil falling down. Why can't you see it? Because it is in the past and because it is too close to you. Can you find someone else that can see it? The answer is yes. Your friend placed at a distance of a few light-seconds can see your pencil falling down. As a matter of fact, distance tells exactly what your friend is able to see. Is there anything wrong with this?

Yes. But we can't see it, nor gather information transmitted by EM radiation. I cannot see today my father who passed away, because he is close to me (upon Earth) and in the past. A fellow E.T. placed upon a planet 20 LY from here can see my father alive. By extension, we cannot see today the explosion of a star 2 millions years ago at a distance of 1 million Light Years from us, because it is too close to us. We would have missed the explosion by 1 million years, as mentionned by Hendrix.

Hm. Lots of considerations here. Personnaly I liked 1 answer: Hendrix wrote: That was my point, so simple. Not regarding any other consideration about relative speeds or remnants. If I had asked wether we can see today a living dinosaur chewing grass in a valley of Germany, I guess everybody could agree about the answer: No. (not talking about the remnants, but about the living creature). Why? Because the dinosaur is close to us (upon Earth) but in the past. If the dinosaur was chewing grass upon a planet 2 million LY away from us, 2 million years ago, we could see the living animal today.

The star exploded, lets suppose it dissapeared. Puff. It doesn't matter. which means....what? Do we see it (today) or don't we? We can not recede faster than light, so the "has not reached us yet" is not an option. The light from the star has reached us 1 million years ago. Can we see it (today)?

Right. Wrong to me. Correcting: A star exploded 2 millions years ago. The star WAS at a distance of 1 million Light Years from us. Can we see the explosion (today)? Merged post follows: Consecutive posts mergedYes or No will do.

IMO infinity is a human concept. I guess changing the concept you can always get rid of infinity. Simple geometrical example. Angle. _Can be defined by degrees, from zero to 360, making the whole circle. _Can also be defined as a slope (used to describe the slope of a road): a distance divided by a height. A slope of 8% corresponds approximatively to an angle of 5 degrees (tangent 5~= .08). A slope of 100% is equal to 45 degrees. And 90 degrees corresponds to a slope infinite. Here we can easily understand that the concept "slope" is not applicable for all angles. The problem of infinite slope is not a problem of the road, nor a problem of the angle: it is a problem arising from the concept.

A star exploded 2 millions years ago. This star is at a distance of 1 million Light Years from us. Can we see the explosion?

Religion is much more than a tool. Religion is a social establishment. It puts people under the same laws. These laws are made unbreaklable by the fact that they were established by a deity, not by any human. It is most often the first and last reason for people to respect any form of central civil government, like kings and other emperors (& Constitutions in some cases). Religion is also a cultural establishment, it makes recognizable people from other people, making it by this way a defense system (& sometimes an offensive system). Religion is part of the economic power and in some case part of the military system. And surely there must be many other aspects of religion I forget here. IMO the fact that religion proposes explanation for unknown physical phenomenas is only a side effect. It is not the main purpose of religion, it is a must do. Religion just cannot avoid this part of the game. The only conflict with science is due to the fact that religion cannot step back easily, because it would be like admitting that God was wrong.

You're very kind. To be honest, there are more than 30.000 reasons to thank the Greeks, but that is out of topic. You wrote: "No one moves through time". I strongly believe exactly the contrary. "Τα παντα ρει", ta panta rei, Everything flows , Heraclitus of Ephesus ~535 ~475 BCE

This was intended to Pioneer who wrote I don't think colour or distance are mental constructs. And I stopped considering time as a "mental construct" ....a long time ago. IMO it cannot be that a "mental construct" appears in almost all physical equations. It must be something more than that.

Right. But Ricci is the onlly Italian I knew that had a relation with Einstein's work. I didn't knew about De Pretto. I found this paper http://www.mathpages.com/rr/s8-08/8-08.htm

Or Joules = Newton Meters [math][Energy] = [mass] [acceleration] [distance][/math] In which the accelerated distance is a constant. ----------------------------------------------------------------------------- As for the thread's question: "Tensor calculus was developed around 1890 by Gregorio Ricci-Curbastro under the title absolute differential calculus, and originally presented by Ricci in 1892.[6] It was made accessible to many mathematicians by the publication of Ricci and Tullio Levi-Civita's 1900 classic text Méthodes de calcul différentiel absolu et leurs applications (Methods of absolute differential calculus and their applications) (Ricci & Levi-Civita 1900) (in French; translations followed). In the 20th century, the subject came to be known as tensor analysis, and achieved broader acceptance with the introduction of Einstein's theory of general relativity, around 1915. General relativity is formulated completely in the language of tensors. Einstein had learned about them, with great difficulty, from the geometer Marcel Grossmann.[7] Levi-Civita then initiated a correspondence with Einstein to correct mistakes Einstein had made in his use of tensor analysis. The correspondence lasted 1915–17, and was characterized by mutual respect, with Einstein at one point writing:[8] “ I admire the elegance of your method of computation; it must be nice to ride through these fields upon the horse of true mathematics while the like of us have to make our way laboriously on foot." from http://en.wikipedia.org/wiki/Tensor#History No plagiarism at my knowledge, only but help.

Many interesting posts lately. One can agree that religion is a human construct. I don't know if that was the meaning of your intervention, but it is the way I understand it. The peculiar thing is that the light of knowledge that makes humans so different from animals, was not given to humans by God. That was Prometheus job. Lucifer in latin (the one who wears the light). The devil.

There is a difference between religion and belief. Belief is a personal thing. Religion is a social structure that obliges you to accept a specific belief in a specific way and to act following specific laws (holy laws). I think belief in itself , or non-belief, is not incompatible with science. As for religion, I think it is incompatible.