michel123456

I don't understand why the universe would have been cooler in the past. If matter and space were compressed by the same factor, for a compressed observer, everything would appear as it appears today, or in the future, or in the past. The time stamp would play no role. The question is what would the past look like? It would appear compressed. Why do you believe it would appear cooler?

Maybe it is an ancient unused cesspit. https://en.wikipedia.org/wiki/Cesspit

See the process here. Extruding of a 2D object in 3D. Brilliant!

Anyway, that makes a bizarre feeling. That of being at a very definite and special place in time. That constitutes another difference between Space and Time. We are lost in space in this Universe, but not lost in time. Because in time our position is well defined. Following Krauss.

That is not the opinion of L. Krauss from http://www.npr.org/2012/01/13/145175263/lawrence-krauss-on-a-universe-from-nothing

Swarm robots, or also called zooids robots

That would not be an illusion. The 2 balloons would really touch each other. And what would be the process that makes the observer move away?

Yes something like that: gravity should be a kind of acceleration. Or better, gravity should be the reaction we feel from a kind of acceleration. If that is true, then we know the direction of this acceleration: it has a direction from outside to the inside, it is radial. IOW it has the effect of a scale factor. But once you make such a statement like "everything is expanding" there is a question arising. If I am expanding, and you are expanding too, then why aren't we bumping together? Take 2 ping pong balls at a distance of 10 centimeters, then "expand" the balls and transform it into soccer balls. If each ball expands relative to its center, then the 2 balls will hit each other. The only way to avoid this is to make the distance between the ping pong balls also "expand". The 10 cm must also transform into 100cm. How is that possible? How can the void between the balls increase? And how does the expansion take place? Relative to what center?

It has been done, but in the decimal system. And not always.

Right, distance is always positive. Time is also always positive. And gravitation always attractive. There is a "direction" in the Universe.

But space has no direction either. Objects moving in space can have a direction, but inherently there is no direction in space. If objects can move following different directions in space that is because space is 3D. If time is 1D, then the only possible direction is along the 1D. The question is simply why does time "flow" along this 1D line in a particular direction and why is it impossible to make a U-turn in time.

Time is relative. Here below my understanding: The concepts of Future & Past in time are similar to Front & Back in space. If you make a U-turn, then what was Back becomes Front, and what was Front becomes Back. Because Front & Back are relative to you, the observer. If you translate this concept of Front & Back in time, then it may be (maybe) that the Past and Future are also relative. For that to be true, one must delete the apparent differences between Future and Past. It means that the Past should stop to be "frozen", stop to "exist" and become the same fuzzy as the Future is. If impossible then yes, the question remains: what is that thing that makes us go from the Past to the Future?

Yes and no. Yes because I understand your point about the "The two "times" of that view are clearly of different kinds; and the one like length is frozen." And No because the "frozen" part corresponds to what we call a path. A path is the inscription of motion. It is a way to describe, both in space and in time, the motion of an object. It is not motion itself. IOW I am thinking now that the 4D Block Universe describe paths. It does not describe what is actually happening. It is frozen picture of a dynamic system. It is not a frozen system.

Thanks to YSL Mon Paris commercial, since I couldn't spot the right one, found this:

(sorry I have skipped the last long posts of this thread) I don't know if I was clear enough. If double time exists, then time is not a line anymore, but a surface. Furthermore, if the past is not "frozen", it becomes something very similar to the future: something that can change (randomly). In such a way that even if time would "flow backwards" (to be read as a U-turn of the observer), the observer would observe nothing very special happening, only usual "flow" (to be read "usual motion in spacetime"). I know it is wild speculation, but that would make time and space a little more equal. Not to say that in principle, triple time would be needed. Each time for each spatial dimension.

Scenario 1. I disagree completely. Making the ruler moving is complete nonsense IMHO. It corresponds to a geocentric view of the Universe, as if the observer was really at the center and dictating how the ruler must do its job. To me, it is wrong. Scenario 2. Yes this is almost the way I see things. The observer is "moving" through time. It means that at some time stamp, the observer occupies a spacetime coordinate, at some other time stamp, the observer occupies another 4D coordinate, and so on. So simple. But lets improve the scenario 2: rain is falling along the ruler while the observer slides from one time stamp to another. IOW, the present is the crossing event between the position of the observer and some rain drop. In this scenario, the future is not "already there", and the past is not "frozen". If you understand what I mean. I don't quite follow the logic behind this comment. How do you propose for the past to be changed, to be unfrozen? Surely you can understand that if you were able to observe a spacetime coordinate that sits somewhere in the "past", you will observe the exact same event..? What else? The fact is that we are not able to observe a spacetime coordinate that sits somewhere in the "past", I mean in "our past". The only things that we can directly observe from any time stamp are very specific and depends on distance. ------------- (edit) I mean, the objects that we can observe all belong to the past, but they do not represent "all the past". They are the objects that lie at a specific distance and at specific time stamp of the past. All other events that are a time stamp that does not correspond to this particular distance are not (directly) observable.

How can an elephant cross a river without getting wet? . . . . . . . . . . . . . . . . . . . . . . He jumps from water lily to water lily.

I don't know if "double time" is a problem. It is surely bizarre but mathematically, and physically, seconds squared are being used without discussion. It is however conceptually difficult that there could be a 2nd Time topping Time. Even in String Theory, when eleven dimensions are introduced, it is explained that all dimensions are spatial and only one is time. And I wonder why. ------------------ And I think that in the 4D Block Universe, something must be introduced to explain the dynamics. I disagree with the concept of time being a "persistent illusion". Something physical is happening. Something like a "double time" is needed in this concept too. ------------------- And I repeat my nonsense: what element proves us that the past is "frozen"? That it still exist somehow in the past cone?

Have you ever been through the experience of being poor?

Sunlight is a good antidepressive. From my own experience: Drink water. Close the internet. Close the tv. Burn the newspapers. Better read a book. Or simply do something. Cook. Clean your place. Don't simply sit ruminating. Don't stay in bed. Don't stay all day long in your pyjamas. Go out. Meet some people (I mean, out of your relatives). A pet is also a terrific antidepressive. Or Come to Greece (as a tourist).