michel123456

That is new to me (the bold part). References?

I may be wrong, but I was simply reading the map provided. If the lake was level, it should be represented on the map by a single color. However is not a single color over the lake. Or maybe the colors are representing the bottom of the lake?

OK I understand that from the car's frame, the ground would appear contracted but please clarify. From the car's frame, what is the measurement? Is it 1m or 1,50m? i mean, the input in the Lorentz equation that will determine the proper length of the moving object ( the ground), is it 1m or 1,50m? I ask this because I really don't understand how one takes the measurement and multiplies it.

So you seem to agree that 1.5m is the measurement as taken from the Earth. What is the mathematical operation that the earthling must do with this number in order to find the proper length? Is it 1,50m multiplied by .... Or Is it 1,50m divided by .... ??

Nice! I don't know about this effect. What I know is that when you use a laser parallel and very close to a shiny surface you can get strange results. The slightest deviation gives you reflections from the shiny surface (in this case, the lake).

The noise produced by the human screaming? I don't know if it safe to make him inhale air at minus 40 celsius.

I will drive you all crazy, I know that. Do you all agree that Dground is the measurement taken in the FOR of the ground? Do you all agree that Dground is longer than Dcar?

+1 for Rovelli I don't see very much on the web for Rovelli, this https://en.wikipedia.org/wiki/Carlo_Rovelli and this https://en.wikipedia.org/wiki/Thermal_time_hypothesis what is it all about?

Please give some more information. Will the experiment be conducted in an open room (as a presentation for students where the students will freeze too), or in some kind of closed chamber? The -40c seems to me difficult to reach with conventional coolers. I guess you'll need some chemical thing.

Sure I did miss something. Here below the text with your corrections and my (mis)understanding ---------------------- | That is OK for me. | What I conclude is this: | The measured distance on the ground is larger than the measured distance on the car. | The measured distance on the car is the proper distance [of the car]. | So, in order to find the proper distance [of the car] from the ground measurement, you take the ground measurement and divide it by a [the] | contraction factor. (because the result [proper distance] is less than what has been measured [from the ground frame]) | Or do I miss something again? --------------------- I mean that the proper distance is less than the measurement from the ground frame, IOW that the measurement from the ground is more* than as measured on the car i.e. that the car "lives in a contracted reality" *It is what has been described in the sketches.

Woaw, you are fast. I din't manage to make it readable on this Forum and quit because I had other things to do. Very funny indeed. I wonder how people can spend their time in creating this. Unless he was laughing all along. ----------- edit _your link doesn't work for me _I found it here https://www.medien.ifi.lmu.de/lehre/ss10/ps/slides/tutorial2.html#(2) _I was wrong, it has a purpose. I expect the author to be still laughing though.

That is OK for me. What I conclude is this: The measured distance on the ground is larger than the measured distance on the car. The measured distance on the car is the proper distance. So, in order to find the proper distance from the ground measurement, you take the ground measurement and divide it by a contraction factor. (because the result is less than what has been measured) Or do I miss something again?

1 yes I hope so, see below 2.yes I am still struggling with simultaneity, that is to say: the difference between simultaneity lines and lines representing ray of lights. It seems to me that in some explanations simultaneity is understood as events that are observed as happening at the same time and that is not my understanding. Maybe it is worth a separate thread.

I understand your explanation. I understand that moving lengths are contracted. I don't understand Langevin's phrase. Making some cuts in his words he seems to say that "the spatial distance of two events reaches a minimum for reference systems in which the two events are simultaneous". The "reference systems in which the two events are simultaneous" is understood by me as the FOR at rest. So he seems to say that "the spatial distance of two simultaneous events reaches a minimum" in a FOR at rest. Is that correct? I mean, do I understand the phrase correctly?

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Sure. But you cannot input the length in the command line(not in my version of Autocad). You draw an arc and then measure it.

You must be trying to confuse me more. 1. means to me that proper length 10m is less than 10.02, thus that the ruler expands (and do not contract) 2. You seem saying in point 2 that the proper length on the ruler is 10.02??? quoting Langevin I would expect the first bold the be "maximum" instead of "minimum" And the second bold to be "longer" instead of "shorter" Isn't he talking about objects & observers at rest in the same FOR? And isn't he talking about "spatial distance" and not spacetime interval?

And smokers leaving cold ashes that smell so dirty. Or planting cig butts in the sand at the beach. Or throwing still burning cig butts out of the window of their car. Or not only smoking, but throwing with pleasure the smoke in your face. Or above your face for being polite. Or simply smokers that do not understand the bad smell they carry with them on their clothes. et caetera et caetera. I am certain String that you will enjoy new food tastes, the need for less spicy meals, the regular taste of French wine, and new smells coming from everywhere around you. Be careful about your weight, because you will breathe better and appetite will rise.

This thread is about Langevin's The Evolution of Space and Time Here in English https://en.wikisource.org/wiki/Translation:The_Evolution_of_Space_and_Time And in French https://fr.wikisource.org/wiki/L’Évolution_de_l’espace_et_du_temps Quoted from page 45 (enhancing by me) The first bold part is understood by me as the contrary of the second bold part. (I checked the original text in French and it is not an error in translation) Where is my error?

It continues. I am confused by Langevin, I will open a new thread that will not disturb this excellent one. --------------------- done. http://www.scienceforums.net/topic/98501-lost-in-langevins-language/

I went back to Mike's calculator https://www.metabunk.org/curve/?d=77&h=3&r=6371&u=m&a=n&fd=60&fp=3264 A small remark: (I did the same mistake) The input distance should not be the straight line (the chord) but the length of the arc I did the same mistake because in Autocad there is no way (at my knowledge) to draw an arc of a specific length. So I choose the facility and draw a straight line. But the distances on Earth (as the length of the lake) are geodesics, they are not straight lines.

If the board was slanted at ~24° then No, you cannot "tell the height of the laser by calculating the number of pixels above the board and comparing them with the board size". In any case, even with a vertical board* it is unsafe to measure on a photo. From my experience, every time there is a significant lack of precision. *not even vertical, it should be perpendicular to the laser beam, and the photo taken from the origin of the laser beam, which is quite difficult (it should be installed like a rifle scope)

Nice! +1 (to transfer also to Mick) with 6km input, as in the experiment, and 1.25 height, it gives 32 cm hidden. And i was wrong that with 1.50m height the entire shore is visible, you need 2.60m height for a null hidden result. That is a lot of work to prove what we already know (that the Earth is round) and I am pretty sure that the precision will not be much better than that of Eratosthenes 2000 years ago. Each cm of lack of precision will have a large impact on the estimated Earth radius. Maybe you'd need another version of the calculator to show that.

Yes it is complicated. But if you replace the bulge with a wall 70 cm high exactly in the middle, it gives the same effect. Which makes me think that from 1.50 height, even the shore is visible. 1.40m is the limit. From 1.25m, it must be calculated. Bizarre. That would make the beam go left & right, not only up & down.