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In the news
http://forums.chiffandfipple.com/viewtopic.php?f=10&t=105736
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Author:  Nanohedron [ Tue Nov 28, 2017 4:44 pm ]
Post subject:  Re: In the news

benhall.1 wrote:
Nanohedron wrote:
Gaah. Too lazy.

See? That's the trouble. That's why so many people believe all this fake news that the Earth is round, when it's clear just by looking that it's flat.

:D

Piffle. We speak of blinders, but what kind? Here's an interesting type I just found:

Image

To foil the boffins' disinformation campaign, this rig will help to keep the fashionable Flat-Earther looking out sideways in both directions at once, which is to say doubly askance.

Rather like this:

















Image

:wink:

Author:  chas [ Wed Nov 29, 2017 8:56 pm ]
Post subject:  Re: In the news

s1m0n wrote:
chas wrote:
benhall.1 wrote:
I routinely espouse the philosophy that the Earth is flat.


On a small scale, of course, you're absolutely right.

One way to get an absolutely flat reference surface is to use water. If you let it sit quietly long enough, it will be flat and level. This was used for a hundred years or so when optical surface measurement (interferometry) was new. A friend and colleague, around 20 years ago, tried to use this technique with a surface maybe 300 mm across. The measurements had progressed to the point where he said he wasn't measuring a perfect flat, he was measuring the curvature of the earth.


Scientists at the Greenwich Observatory in London used this method - only with a pool of mercury* rather than water - as their horizon when calculating the location of the prime meridian. There's a monument there today, with an iron (I think) line inlaid in the pavement showing the location. Interestingly, it's off by 100 yards from what present day visitor's GPSs show as 0° long. The explanation is that back in the 19th C when the experiment was being conducted, the presence nearby of a large mass was just enough to alter gravity locally and throw the instrument off, slightly.

Here’s Why The Greenwich Prime Meridian Is Actually In The Wrong Place

*In theory, a pool of mercury, at rest, makes a perfectly horizontal mirror.


Yep, it works with mercury, too. If you're using it as a perfect flat reference surface to measure something else, you use mercury if you're measuring a metal (high reflectance), and water if you're measuring glass (low reflectance). The way you make the measurements uses fringes resulting from the interference of light, so the contrast is maximum if the surfaces reflect a similar amount.

Author:  s1m0n [ Wed Nov 29, 2017 11:45 pm ]
Post subject:  Re: In the news

I don't get the reflectance distinctions. Can you elaborate in a way that a lit major might grasp?

Author:  Tor [ Thu Nov 30, 2017 8:37 am ]
Post subject:  Re: In the news

I just watch the nearby mountain at sunset. The part of the mountain which is still bright creeps upwards. Wouldn't happen if we lived on a disc.

Author:  chas [ Fri Dec 01, 2017 9:02 pm ]
Post subject:  Re: In the news

s1m0n wrote:
I don't get the reflectance distinctions. Can you elaborate in a way that a lit major might grasp?


If you shine a light onto a highly polished surface of a white metal like platinum or aluminum, almost all of that light will be reflected back. That's a high-reflectance surface. If you shine it onto a pane of glass, 4% will be reflected back. That's low reflectance. Silicon is in between, about 35%.

Another way to look at it is, if you look at a mirror, you see a good image of yourself. If you look at a pane of glass, you might see yourself, but it would depend on what's behind the glass since it's passing most of the light -- if you're inside at nighttime, you can see yourself well, if it's daytime outside, you see what's outside.

The most precise way to measure the shape of an optical surface is by comparing it to another surface. This is done by splitting a beam of light into two arms, reflecting those off of the reference optic and the optic under test, and recombining them. This results in a series of fringes -- stripes, bullseye pattern, or something else. The best contrast in the fringes happens when the two beams have the same intensity, which is when the two surfaces reflect the same.

So if you're measuring the shape of a metal mirror, a pool of mercury would provide a good "perfect" flat surface. If you're measuring a glass surface, a pool of water would be the appropriate perfect reference.

I hope that's a little clearer. Feel free to PM or email me or ask further on the board; I love talking about this stuff.

Cheers, Charlie

Author:  s1m0n [ Fri Dec 01, 2017 9:32 pm ]
Post subject:  Re: In the news

Thanx. I think I got the gist. When you talk about fringes, do you mean slightly out of phase interference patterns?

Author:  Dan A. [ Sat Dec 02, 2017 8:29 am ]
Post subject:  Re: In the news

s1m0n wrote:
Yeah. The whole thing is about attention, not about the curvature of the earth. Writing earnest pieces about why the stunt-guy is wrong is accepting his framing for the story, and means he wins. The public he's appealing to already knows he's wrong, and they don't care. They feel oppressed by science, and are willing to support a champion who'll tell smarty-pants scientists "up yours".

The same thing is true of anti-vaxxers, but the difference is that denying your children vaccines can seriously harm them, as well as society as a whole. This guy can harm only himself.


Let's hope so, especially considering the statement he made in the article:

Quote:
(H)e acknowledged that he still had much to learn about rocket science.


Taking what I know about ordnance (I do have a background in military aviation, though not ordnance), a rocket lacks any sort of guidance system. The contraption that the flat-earther in question has built appears to have no real means of control. If so, it will be at the mercy of gravity and the wind. Despite his plans to launch his rocket over a sparsely populated area, this has all the makings of something that will not end well, especially considering that he still has a lot to learn.

The anti-vaxxers are another matter...one I have strong opinions about, but I will not share said opinions here.

Author:  chas [ Sat Dec 02, 2017 9:17 am ]
Post subject:  Re: In the news

s1m0n wrote:
Thanx. I think I got the gist. When you talk about fringes, do you mean slightly out of phase interference patterns?


Exactly. The technique is interferometry — the evolution of what Michelson and Morely used to determine that the speed of light is invariant.

Author:  david_h [ Sat Dec 02, 2017 1:56 pm ]
Post subject:  Re: In the news

I think light being polarised by reflection off glass and water but not off metallic surfaces may have a lot to do with it.

Author:  chas [ Sat Dec 02, 2017 3:25 pm ]
Post subject:  Re: In the news

david_h wrote:
I think light being polarised by reflection off glass and water but not off metallic surfaces may have a lot to do with it.


No, it’s strictly intensity— if you have a 4% reflection on one arm and a 95% reflection on the other, the contrast is only a few per cent when you add them together (i. e., interfere them).

Author:  DrPhill [ Sun Dec 10, 2017 3:12 pm ]
Post subject:  Re: In the news

benhall.1 wrote:
.......You've heard of The Bedford Level Experiment have you?

I had not, but thank you. I read the wikipedia answer too - but the scientific 'explanation' seems a little too contrived. Atmospheric refraction can exactly match the curvature of the earth so the light 'just happens' to bend the same amount as the earth?

I prefer this:Image

Author:  Nanohedron [ Sun Dec 10, 2017 4:42 pm ]
Post subject:  Re: In the news

Umm...

Why is he crawling?

Author:  s1m0n [ Sun Dec 10, 2017 5:33 pm ]
Post subject:  Re: In the news

I wonder if that weird double wheel thing is Ezekiel's 'wheel within a wheel'.

Author:  Nanohedron [ Mon Dec 11, 2017 3:25 pm ]
Post subject:  Re: In the news

s1m0n wrote:
I wonder if that weird double wheel thing is Ezekiel's 'wheel within a wheel'.

That's what I chalked it up to be.

Author:  An Draighean [ Tue Dec 12, 2017 7:42 am ]
Post subject:  Re: In the news

Nanohedron wrote:
Umm...

Why is he crawling?


He's bein' repressed! Come and see the violence inherent in the system!

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