It is currently Thu Dec 14, 2017 2:31 pm

All times are UTC - 6 hours




Post new topic Reply to topic  [ 54 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
 
 Post subject: Re: In the news
PostPosted: Tue Nov 28, 2017 4:44 pm 
Offline
Moderatorer
User avatar

Joined: Wed Dec 18, 2002 6:00 pm
Posts: 32416
Location: Minneapolis
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:

_________________
"Dreams about the future are always filled with gadgets." - Neil deGrasse Tyson

"An anti-lunacy gadget would be nice..." - Nano


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Wed Nov 29, 2017 8:56 pm 
Offline
User avatar

Joined: Wed Oct 10, 2001 6:00 pm
Posts: 7328
Location: East Coast US
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.

_________________
Charlie
Whorfin whistles -- sample 1 -- sample 2
Don't blame me, I voted for Cthulhu


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Wed Nov 29, 2017 11:45 pm 
Offline
User avatar

Joined: Wed Oct 06, 2004 12:17 am
Posts: 9867
Location: The Inside Passage
I don't get the reflectance distinctions. Can you elaborate in a way that a lit major might grasp?

_________________
And now there was no doubt that the trees were really moving - moving in and out through one another as if in a complicated country dance. ('And I suppose,' thought Lucy, 'when trees dance, it must be a very, very country dance indeed.')

C.S. Lewis


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Thu Nov 30, 2017 8:37 am 
Offline

Joined: Wed Jun 06, 2012 6:23 am
Posts: 266
Location: Europe and Japan
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.


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Fri Dec 01, 2017 9:02 pm 
Offline
User avatar

Joined: Wed Oct 10, 2001 6:00 pm
Posts: 7328
Location: East Coast US
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

_________________
Charlie
Whorfin whistles -- sample 1 -- sample 2
Don't blame me, I voted for Cthulhu


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Fri Dec 01, 2017 9:32 pm 
Offline
User avatar

Joined: Wed Oct 06, 2004 12:17 am
Posts: 9867
Location: The Inside Passage
Thanx. I think I got the gist. When you talk about fringes, do you mean slightly out of phase interference patterns?

_________________
And now there was no doubt that the trees were really moving - moving in and out through one another as if in a complicated country dance. ('And I suppose,' thought Lucy, 'when trees dance, it must be a very, very country dance indeed.')

C.S. Lewis


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sat Dec 02, 2017 8:29 am 
Offline

Joined: Thu Nov 30, 2017 8:19 pm
Posts: 28
Location: Bitter-cold Michigan
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.


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sat Dec 02, 2017 9:17 am 
Offline
User avatar

Joined: Wed Oct 10, 2001 6:00 pm
Posts: 7328
Location: East Coast US
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.

_________________
Charlie
Whorfin whistles -- sample 1 -- sample 2
Don't blame me, I voted for Cthulhu


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sat Dec 02, 2017 1:56 pm 
Offline

Joined: Mon Aug 13, 2007 2:04 am
Posts: 1083
Location: Mercia
I think light being polarised by reflection off glass and water but not off metallic surfaces may have a lot to do with it.


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sat Dec 02, 2017 3:25 pm 
Offline
User avatar

Joined: Wed Oct 10, 2001 6:00 pm
Posts: 7328
Location: East Coast US
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).

_________________
Charlie
Whorfin whistles -- sample 1 -- sample 2
Don't blame me, I voted for Cthulhu


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sun Dec 10, 2017 3:12 pm 
Offline

Joined: Wed Nov 19, 2008 11:58 am
Posts: 1286
Location: None
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

_________________
Phill

Press any key to continue, any other key to exit.......


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sun Dec 10, 2017 4:42 pm 
Offline
Moderatorer
User avatar

Joined: Wed Dec 18, 2002 6:00 pm
Posts: 32416
Location: Minneapolis
Umm...

Why is he crawling?

_________________
"Dreams about the future are always filled with gadgets." - Neil deGrasse Tyson

"An anti-lunacy gadget would be nice..." - Nano


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Sun Dec 10, 2017 5:33 pm 
Offline
User avatar

Joined: Wed Oct 06, 2004 12:17 am
Posts: 9867
Location: The Inside Passage
I wonder if that weird double wheel thing is Ezekiel's 'wheel within a wheel'.

_________________
And now there was no doubt that the trees were really moving - moving in and out through one another as if in a complicated country dance. ('And I suppose,' thought Lucy, 'when trees dance, it must be a very, very country dance indeed.')

C.S. Lewis


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Mon Dec 11, 2017 3:25 pm 
Offline
Moderatorer
User avatar

Joined: Wed Dec 18, 2002 6:00 pm
Posts: 32416
Location: Minneapolis
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.

_________________
"Dreams about the future are always filled with gadgets." - Neil deGrasse Tyson

"An anti-lunacy gadget would be nice..." - Nano


Top
 Profile  
Reply with quote  
 
 Post subject: Re: In the news
PostPosted: Tue Dec 12, 2017 7:42 am 
Offline
User avatar

Joined: Mon Mar 26, 2012 11:18 am
Posts: 614
Location: Parker County, Texas, USA
Nanohedron wrote:
Umm...

Why is he crawling?


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

_________________
Deartháir don phaidir an port.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 54 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC - 6 hours


Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group
[ Time : 0.139s | 16 Queries | GZIP : On ]
(dh)