michel123456

http://www.esa.int/spaceinimages/Images/2011/03/New_GOCE_geoid

I missed how your long post #205 is an explanation of "An ocean floor feature 1km high results in a change in surface depression, reducing it by 2 metre". Your are explaining a variation of the force of gravity caused by a variation of the topographic relief. I posted a link to a map that shows it is not the case.

3 And 2. The whole thread slipped away. It has gone into explaining Relativity again. The aim of this thread was to show how much words can be confusing. To speak frankly, I think that the following statement is not compatible with your explanations. Which means either 1. it is a small mistake from Langevin (that can happen especially if it is a speech) 2. all your explanations are inaccurate (that is highly unlikely) 3. I don't interpret correctly the wording. I have chosen 3 and opened this thread.

Great job! However _you have no reference (that is the reason you had to create one) _that would mean that a gravity map of the Earth would show lower gravity under the oceans and higher gravity over mountains. It is overall simplified and not accurate at all . See http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE/Earth_s_gravity_revealed_in_unprecedented_detail For the Andes you seem correct but the Himalaya shows less gravity than the North Sea.

Thank you. Done. Exactly!! And we are experiencing all the time a similar phenomenon when looking around us.

I cannot disagree more. If you need metaphysics to "make sense" of physics it is a huge defeat. I will not step into this kind of discussion. To me, any model of physics must be self explainable and self comprehensible. You don't need metaphysics to explain physics. You don't need metaphysics to understand physics

Just wanted to share Click on the image if the gif doesn't start. It is a scale factor. It can also be seen as if you were traveling. It follows the rules of perspective: there is a focus point, all the lines are extending geometrically from this point. But the on graph it is a scaling. And the scale factor pictures an acceleration, but that is not so easy to decipher. Here below an explanation to my acceleration comment. *(edit) for a regular time interval (say each second) the length increase exponentially. So that the next time you travel on the highway you may realize that although moving at constant speed you see the surrounding scaling and that corresponds to an acceleration. Even worse: If you stay at rest, you see the world around you deformed exactly like a scale factor would do. And that corresponds to an acceleration.

That is clear. yes. I am thinking that the world lines of the objects that create the events are missing from the gif. So you mean an event can be happening in the wild future (say in the upper part of the gif, above the horizontal simultaneity line. This future event will then travel downwards as time is passing by and cross the horizontal line (not shown): it means the event is happening "now" but so far away that it is not observable. The same event will continue downward and cross the diagonal line thus becoming "currently observable" at the depicted origin. Finally the same event will enter the observer's past without the possibility to get out. That is what I guess is the block universe: nothing is happening, the observer is simply discovering his observable universe bit by bit. And this block universe appears soft like a marshmallow when the observer is accelerating. Is that it?

+1 for Leigh Rubin, never heard about him before, unfortunately. Great mind!

I am doing that all the time since the age of twelve. If you replace the cut with a scan, yes that may help. Because when you make a cut, it is done and you cannot make it again in another way. A scan does not disturb the bread, it is simply an image. Everything is great and fully comprehensible about the relativity of observation from each frame. The comprehensibility gets difficult when it comes to make the image a "real" thing. As if the image from the scan suddenly transformed into a real slice of bread. And as Swansont posted, the same utterly incomprehensible phenomenon appears with kinetic energy. Figure that the Earth is hit tomorrow by some gigantic asteroid, where was the KE hidden all this time? Inside motion? The KE reveals with the collision the same way the image of the scan reveals into a slice of bread.

The problem is that that doesn't explain anything. That makes everything mysterious. Kinetic Energy, length, distance, time become elusive. ---------------------------- edit That is why I am searching a way to ground all these. In the FOR of the object itself, length doesn't change, time doesn't change, and KE is null. Perfect.

Yes I accept this. Very enlightening post. +1 again.

Go to the "more reply options" in the bottom right corner of the post. It will give you the ability to upload an image file and add it to your post.

Maybe I was unclear. In an inertial diagram, are they dots that cross the diagonal in the same way? i mean crossing = moving, not simply being there.

Dear managers Does the software allow to add the "report" button in the preview panel ? I ask this because at this moment I must open the thread, tick the button report, write the report but then if I go out with the back button I see the spam report again, then the "new content" page as it was previously (the thread is indicated as not read). Then I need a refresh page. IOW I need about 7 moves for each spam report and that takes time. It should be more effective if the report was more easily accessible from the preview panel. Thank you.

Sure there is. Because in my examples nobody is arguing that B becomes "really" shorter because there is a distance between A & B. In Relativity some argue that B is "really" shorter and that time is "really" dilated because these are not optical effects. You must understand that it is really troubling. Especially when it is linked to the symmetrical effect. IOW any layman will accept that if B is "really" shorter than A, the A is "really" bigger than B. And a layman will not accept easily that they are "both really shorter than the other".

Maybe That is sensible, i cannot argue against anything you said above. Than you. Much appreciated. Wait... what other thread? (Alzheimer* striking again) *joking. I hope

This is exactly my question, see below after all comments This is clear, I have no problem with that. My question is the following: I have erased everything that is not observable at time stamp T The bottom triangle contains the events that were observable in past time (before time stamp T) At time stamp T only the events that lie exactly on the diagonals are directly observable. In the GIF, we are seeing dots that come from the blank upper zone and go into the bottom triangle. What does that mean for the observer? In my understanding (but I may be wrong) it means that the accelerated observer sees an event coming from the future suddenly happening and being directly observable. Then the event disappear from the directly observable zone and enters the past i.e. it was once observable. Is that correct?

Set of values, yes. That is what I was trying to say. If you have a set of values, how do you insert this set? All at once? Only the fact that you must insert this set means time. "for any given value", what does it mean for you? That you give all the values at the same time? Or that you insert a value, take the result, then insert another one, take the result & etc ad nauseam then draw the result. For example you can at t=0 insert a single value and at t=1 get the result, and at t=3 draw a single dot. I don't think it is conceptually acceptable to make those 3 steps in δτ=0

The equation gives a single solution. If you want many solutions to describe the entire wave, you must make several inputs the one after the other, no?

this is the last take on it http://www.independent.co.uk/news/science/nasa-publishes-faster-than-light-spaceship-design-to-imagine-interstellar-exploration-9535294.html

This gif was posted by a fellow member in another thread My question is: If you look carefully, some dots are crossing the diagonal lines. As explained above, the events that pass the two diagonal lines in the bottom half of the image (the past light cone of the observer in the origin) are the events visible to the observer. Does that mean that the dots as seen by the traveler suddenly appear as coming from nowhere? That events pop out? As if coming out from the unobservable part they appear suddenly? I hope that my question is clear.

Maybe a re-post.

This is the corner stone of all misunderstandings. i use to compare it to the optical effect caused by distance. When A see B at a distance, B looks smaller. At the same time, when B looks at A, then A is smaller. So it happens that A and B "are" smaller than each other. But it is not a contradiction. This is to be parallelized to standard comparison of heights: If A is bigger than B, then B is smaller than A. These are 2 totally different concepts.

this part: that the surface of the ocean follows the bed surface. That is not of my knowledge. 1.from what I (thought I) knew, the ocean bed is thinner than the continent. Where the mountains rise, the crust is deeper, like an iceberg. 2.I don't understand why the ocean surface should follow its bed. I am guessing that the ocean surface shoud follow the geoid, since it is the definition of what the geoid is.