Discussion in 'Flat Earth' started by Sandor Szekely, Jul 31, 2016.
Adjusting for the horizon, that's 24° of slope. Cos(24) = 0.91, so about 9% error.
That's assuming the measurements were completely flush with the board for every measurement. At times you can only see the top, maybe 9 inches of the tape. But I think it's safe to assume with the weight of a human adult also pushing down on the back of the boat adding to the potential angle that anywhere up to 9% is possible error.
These facts render the entire experiment inconclusive. I think if it's done again they need to do more pre tests for every aspect of the experiment. Test their leveling method, and document things they try. Test long distance beam divergence, not concerning themselves with curve measurements, so can be pointing on the horizon or just above.
Had this been any sort of a professional review, and I'm not putting anyone here down, this experiment would have been thrown out before the video buffered.
I think Mick's findings pretty much settle this. There were (retro)reflective surfaces in the boat at fixed heights, and the people on the shore only saw the reflection from those surfaces, thus incorrectly concluding that the laser height doesn't change.
A good experiment would have used a large white board (not retroreflective) that allows reliable identification of the center of the beam at any height. The heights should be measured in the boat.
Sándor, I don't even understand why you only used such a small board that is completely unsuitable for the purpose. Were you so sure that the beam will not rise higher that you didn't even think that you might need a taller board?
Sandor, you're saying that the argument that the beam is very wide is an assumption, not fact. Is that right?
But statements like this are also an assumption, not a proven fact. Is that not so?
In other words, your collimator is very good, and your math is flawless, therefore the beam divergence must be as small as you say it is. Two assumptions.
Why not be empirical and test the beam divergence? You can then put this argument behind you.
I suggest putting a much larger and unmoving target on dry land. An essential part of this is to leave the laser in a fixed position and measure the divergence at different times: most crucially at night when any reflection will be most noticeable.
Will your beam look like this?
You might say, "No," but that's an assumption. Let's find out.
I think this thread needs an index.
at the same time they could test the camra "direct hit" methord and show us that it is a valid methord or not
I think this demonstrates that it is not.
The boat moves several feet perpendicular to the beam while it is reflected off the camera being held by someone in the boat. This means that the person in the boat is getting a "direct hit" at each of those locations.
And if it's able to do this moving horizontal to the water, logically it can do the same moving vertical to the water. Which is why the whiteboard is entirely inappropriate. As you've stated before, they should be taking measurements of the top and bottom of the beam and finding the middle that way.
And here's a close-up of the reflection off the jacket retroreflective patch, making it clear that it's traversing the width of the beam. Youtube video has show motion contrast enhanced. From 02:38 in MVI_7124.
Notice the varying intensity as it traverses the beam, which seems around 3 feet across at that height.
And there's a hint of it just catching the top of the whiteboard at the start and end of the video loop.So I'd suggest the actual beam is more like:
And, the video description says:
So we can use that to calculate the height of the black tape from the waterline here:
With the boat at right angles, we measure the length of the edge of the board and the height of the tape above the waterline.
Since the board edge is 1m, then the height of the top of the tape is 513/438 = 1.17m, and yet in C2, etc, Sandor claims the top of the tape was calibrated at 1.30m. This is due to the use of the tape measure at an angle, as noted above.
The laser itself was measured at 1.25m.
So the laser was pointing down.
Hence all the measurable experimental results are consistent with the globe earth model.
I'd count that as a Metabunk 'debunk' and say good luck with future experiments.
If we go back to what happens if the laser is pointed down a bit:
The blue curved line is the expected drop of the earth. The other lines are the laser pointing down varying amounts. Notice that the drop of the laser tends to "hide the drop" of the earth over the first mile or two. This is faily consistent with what we saw in the experiment, with the laser staying at the top of the board for a while, then eventually rising above it (at which point it became unmeasurable due to divergence, and no target).
Yes I don't think there much more point analyzing this any more.
I'd like to commend Sandor and the others for the amount of work they put into this, and the openness. Had Sandor not shared most of the photos and videos then it might have simply been another flat earther video with unanswered questions. But here we can definitively say that the claimed measurements are invalid (and in some cases demonstrably wrong).
It does however provide a useful learning experience for anyone who would want to try a similar experiment. Ultimately it's somewhat pointless as the Wallace method is a lot more accurate, but I would love to see someone actually do this experiment correctly with more rigorous measurements and a bigger boat.
The original experiment was supposed to be between two points on the shore of the lake, 23 km apart, as explained here:
Then a "pre-test" was done with a laser shining on a target on a boat. This was only supposed to be an early test of the equipment and procedures. With a new laser, another boat test was done.
Has the boat test somehow become the main experiment? Has the original plan been abandoned?
Didnt we learn from this current experiment that that video won't work? The laser would have to be alot higher than 3.3 feet above the water and "direct hits into the camera" are not a plausible technique.
And they still have to figure out a real way to get the laser not pointing down.
Their method was fine on paper, just very poor measurements.
well it would be hard to lean over a squishy boat with a guys tape measure and a slanted board and get a good measurement. Maybe next time, sandor.. you use a dressmakers tape and make it into a plumb line, then you can just hang it off the top of the board. ??
I think they would be better off having a board that has measurements on it, and using a second boat. If the board was aptly big to make measurements for the globe model, the second boat could gather all the measurements.
It was fun examining different aspects of the experiment, but it goes to show that you can't just review the numbers in an experiment like this. You really have to look closely at the video and photo evidence to see that everything was done to a high standard. Small things can escape a busy eye/mind that ultimately cause major headaches. No one person had the answer on their own, it took many eyes and many thought processes to get the bigger picture.
oh yea me too. and i think they should have different colored markers to mark the center of the beam spot at the different locations right on the board. I think if everything was done properly you wouldnt need crazy accurate heights (in numbers) (after say c4 location) because it would be super obvious the beam is going up from the marker marks.
but they still would have to intially measure on the boat from the water line to level the laser, or no?
Or just mount the board sideways, and higher (2m or so, and set the laser at 2m, so the beam starts at the bottom, not the top), and at the front of the boat, so the beam hit can be imaged directly without a second boat.
Oh, and vertical (or with a precisely measured angle). And with marked 10cm bands.
I don't really think they need to make there leveling measurements from the water, no. With appropriate equipment they should be able to get the laser leveled on a level piece of solid land. They should pretest every aspect of the next experiment regardless. Pretest them to death!! Because that's how you construct a final paper for something like this. By saying, we've tried various methods, some worked better than others, this is why we chose the individual methods we chose and then discuss. Even if we couldn't find much fault ourselves, there's not enough in this experiment to put together any kind of a scientific paper for peer review.
I think a second boat would remove the need to have too many people in the main boat potentially shifting weight around it addingerror to measurements. They could put 50 people in the second boat (exaggeration to emphasise a point, and it would be amusing to see 50 people in a boat the size of the one in the video) for all that matters, so long as the first boat remains a controlled element of the experiment.
you're gonna need a bigger boat.
Do you have any pictures showing the amount of tilt of the boat in motion vs drifting? I know it's kind of academic given the other issues, but I do think it's yet another contributor to the inaccuracy.
Many of the "measurement" pictures show wake behind the boat so it was clearly moving, and since the boatman is also visible many of them they obviously weren't taken at the back of the boat near the measuring board.
The picture and video I showed Sandor earlier were for a Selva 500 series, this looks to be a 460 but likely behaves similarly. I can find pictures and video of a 460 in motion that do show significant "lift" but none at rest in the water. I did find a review of the Selva 460 that says.....
Great work finding the reflective patch on the boatman's jacket BTW. I went about it completely the wrong way, got as far as finding the jacket and info on it having patches but couldn't find any pictures of where they were.
Maybe a list of the issues in the OP would be useful? It's a long thread and probably very difficult for anyone coming to it fresh to root through.
As a bit of a boaty person I would not worry about the boat tilting or lifting if it is moving slowly. It is likely to tilt most when semi-planing, and lift most when planing. Provided the speed is a couple of knots below hull speed, moving is not likely to be an issue, and it makes sense to move slowly underway to maintain 'steerage'.
From MVI_7124, ten seconds apart, drifting vs underway at low-medium power
And at16 seconds, showing the laser in the same spot, but mostly off the board
The pushing of the propellor will tend to rotate the boat about its center of gravity. I'd estimate the back has dropped at least 5cm.
Are we talking about a tape measurement at position C2 before the final leveling at C4?
This 90 cms is an information to my laserist how much we have to raise the beam upwards.
Who said that we are measuring the laser heigh IN THE measurement with a tape?
We made the initial level marking on the board with vertical tape of course! check the video it shows the process
we leveled the laser beam to the black marker tape - as close as we could in 0.001 degree accurace
ha anyone tried to level a laser at a distance of 720 meters in a boat on water?
Are they taking measurements with a wake like that?
your assumption on this calculation is way wrong and that lead you all to a missunderstanding
that position was an intermediate levelin at position C2, before the laser was lifted upwards.
it is just an information to our laserist NOT a measurement...
what distance did you calculate that on Mick?
"The pushing of the propellor will tend to rotate the boat about its center of gravity. I'd estimate the back has dropped at least 5cm."
Mick a boat lifts the nose upwards at speed - how did you come to this assumption, that you will seem to take granted from now on?
the wave height is marginal to the differences according to the GE and FE model.
this is a calm water and we made many measurements.
from position C8 and onwards the GE curved water surface model can be discarded.
we are talking about meters of differences
Mick this is a ery false assumpion with the beam divergence here!
How come we have such a strong DIRECT hit of the laser beam at the very low side of your imaginary beam spot?
this is a nonsense and just full of assumptions
I have added a summary of the ket points of this thread to the OP
Pleas let me know if I missed anything, or if there are errors.
Because it's a retroreflective patch. The reflection will be orders of magnitude more intense than a diffuse reflection from a white surface.
We are talking about the height of the black tape. This is more accurately measured here as 1.17m, but you claimed 1.35
Meaning your laser is pointing down.
By analyzing the video. Did you not see the images in the post you quoted?
@Sandor, I suggest you take a day or two to really examine the video at all the places where we have pointed out the problems. They raised the beam at this point of the video, took the measurement of 90cm, but they didn't make the measurement vertically from the water. The fact they didn't that means the 90cm measurement is not accurate. Infact it would have been less than 90 cm had it measuref vertically. This is a fact, an undeniable fact. So why are you here trying to deny it?
It's you that seems to be misunderstanding here Sandor. The laser was pointing downwards and you didn't take adequate steps to ensure it wasn't. Micks calculations are correct. Can you not see from how much of a tilt the board had, and how the measurements were taken on the tilted board that the data collected is incorrect?
I've made a video demonstrating the intensity difference of retroreflection vs. diffuse white reflection
Laser dot on white background:
Laser dot on retroreflective patch
Of course this is somewhat different as the beam is not spread, but the brightness increase is similar.
We should make it clear what a retroreflector is. This is a good article:
This is a video showing a laser experiment. A laser is shone on a retroreflector on a hill 2 km away. As far as I can see this is a low power laser with no collimator. The light is being reflected back to the source and the position of the observer's eye is critical.
timestamp: laser reflectior start about :50
I was refering to the boat WAKE as an indication of the speed. At 3 knots or so I don't think there would be any significant tilt or lift, but the wake in the obove pictures suggested a higher speed at the time.
With a wider beam (shone through a 10mm lens to diverge it)
Even at the very edge of the beam, the retroreflector is significantly brighter than the center of the beam. This is a from a very weak <5mW laser.
Nearer the center of the beam it has overloaded the camera sensors at 100% brightness.
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