Observations of Brighton from Worthing Pier

Z.W. Wolf

Senior Member
There's also the issue of scattered light. In the above video we are seeing laser "beams" coming from the lasers set up right there on the beach. In a vacuum the "beams" would be invisible. What we are seeing is light scattered by dust, haze, etc.



That spot of green light in the distance could be nothing more than scattered light - not the distant laser shining directly into the camera lens. The source of light could actually be hidden below the horizon. This is well established, with the scattered light of below the horizon lighthouses being visible in some conditions and not others - i.e. visible when scattered by clouds but not visible in clearer conditions.

The most familiar example of this effect is the sunlight in the sky after the Sun has gone down (here complete with crepuscular rays). In this case you could not get direct sunlight on a target, but you can still "see" the Sun.



What we need to see is the actual spot of light from the distant laser shining on a target. And a taget big enough to contain the entire beam, not just a part of it.
 
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Mick West

Administrator
Staff member
What we need to see is the actual spot of light from the distant laser shining on a target. And a taget big enough to contain the entire beam, not just a part of it.
A ten miles the spot would be huge. My tests show the main beam of the green laser diverged from essentially a point to 2" in 330 feet. extrapolating that to 10 miles (10*5280/330*2/12) gives 26 feet.
 

Mick West

Administrator
Staff member
There are some small breakers, and they seem to be standing where the water makes its way up the beach, stops and recedes. There's a lot of ambiguity about where the "water level" actually is. This is not the only problem, of course. Just one more bit of ambiguity.
Here's a brightened frame.
Metabunk 2019-02-25 09-09-59.jpg
I think that's pretty good for "at the water". It's a pretty shallow beach there.

It's not clear if that green dot is the the Worthing laser, or the end of the Brighton laser hitting something. Here's my laser (similar mode) hitting a tree 100m away. Looks very similar.

Still, as expected they were able to see the laser due to refraction. I look forward to seeing more photos and video.
 

jarlrmai

Member
It doesn't look that close to the water the laser water reflection seems to only start a way away from the laser and it's on a extended tripod.

The water seems to skirt around the area they are on the speckles seem to indicate there is shingle to the right and left.

This photo is a useful reference you can see the tall red light topped structure (Shoreham Power Station i think) in both photos and it shows the slant of the beach and the tops of the lights on Worthing pier.

https://goo.gl/maps/Gus2brag4N22
Metabunk 2019-02-26 05-43-50.jpg
Metabunk 2019-02-26 05-45-04.jpg
[mod: added photos]
 
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deirdre

Moderator
Staff member
It doesn't look that close to the water the laser water reflection seems to only start a way away from the laser and it's on a extended tripod.
in the beginning of the video above, when dr. john calls them, she says it was at the water line when they set it up. i didn't watch for long because the camera movement is too annoying for me (although at least she filmed! so that's good), but seems it took them a long time to set up (the other side) and the water line moved a bit.

I could be wrong, but i dont think it makes that much of a difference. considering we dont know what was happening on dr. john's side anyway. (unless he posted info since then).
 

Mick West

Administrator
Staff member
I could be wrong, but i dont think it makes that much of a difference. considering we dont know what was happening on dr. john's side anyway. (unless he posted info since then).
He live-streamed bits of it. They were in or near the water, and at several points had to run to get away from the incoming tide.

But it really does not make much of a difference. Refraction is probably going to be the major factor here.
 

deirdre

Moderator
Staff member
He live-streamed bits of it.
i see. at least his camera was less moving all over :) this is off topic really but just curious.. his laser beam looks pretty big, is the tube somehow making the beam come out fatter? it looks like half an inch. or is that just because the stick is so close so its 'spreading' as it hits the stick?
upload_2019-2-26_13-35-43.png
 

Mick West

Administrator
Staff member
his laser beam looks pretty big, is the tube somehow making the beam come out fatter? it looks like half an inch. or is that just because the stick is so close so its 'spreading' as it hits the stick?
That's just glare. The actual beam is about 1mm at that point.
 

Loki Thorson

New Member
Dr John D has made another bold statement in that in everyday, normal non specialised conditions ove the sea, in the evening and night, light will be retracted in an upward direction. would that be favourable in the case where the laser was seen to be going overhead, so therefore normal on a flat earth model ?
 

Mick West

Administrator
Staff member
And would you agree that temperature gradient could also be inverse meaning the laser can bend either way depending on the temp gradient
Sure. There's quite a variety of potential temperature gradients. It can go up, or down, to varying degrees, and can also change direction (i.e get cooler, then warmer (an inversion layer, then cooler). It's quite complicated.

Unfortunately, the best way we have of determining the temperature gradient is often just to observe the refraction it creates. This is especially true over water, where the temperature at the shore can differ quite a bit from the temperature even a few hundred feet out to sea.

Many of us have had the experience of swimming in the ocean and finding it's colder further out.
 

Mick West

Administrator
Staff member
Mick if the water temp and air temp for that day were very similar how does refraction account for this observation?
By there being a slight temperature gradient. You only need 0.5 degrees, or less.
And now Dr. John has published his results:
Source: https://www.youtube.com/watch?v=mKrZnKu9ID4


Showing this temperature gradient:
Metabunk 2019-03-19 20-54-44.jpg

that's at 1.5°C thermal inversion over 2m, you can get the lasers visible with 0.2°C
https://www.metabunk.org/refraction/?~(p~'Brighton*20to*20Worthing*20Pier)_
Metabunk 2019-03-19 20-55-58.jpg

More dramatic temperature profiles, like they showed, only makes it easier.
Metabunk 2019-03-19 20-58-43.jpg
 
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Laser

Member
If we could get an accurate height and distance between the top and middle lights on the i360, up higher where refraction would compress the image less, then maybe we could calculate approximately where the low tide line of the beach should be in the picture if there was no refraction, and verify whether or not the laser image was pulled up by refraction.
 
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