Regarding your FAQ, I think you need to update this statement:

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berny_74

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #90 on: July 03, 2011, 07:33:04 PM »
Indeed. 

 We are getting way O.T. here, but that's the facts. Inverse square does not apply to a light that been focused.  I can  cite some real world examples and show you the math, if you want.  Or you can just look it up - it's mentioned a lot.

Here's a question - can you focus light without any sort of artificial or mechanical means?  Removing of lenses and blinders to the light source - what would it's impact be?

Berny
OT ?
To be fair, sometimes what FE'ers say makes so little sense that it's hard to come up with a rebuttal.
Moonlight is good for you.

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Puttah

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #91 on: July 03, 2011, 09:11:40 PM »
Here's a question - can you focus light without any sort of artificial or mechanical means?  Removing of lenses and blinders to the light source - what would it's impact be?

Berny
OT ?
If there is, I haven't heard of it. Naturally, photons are emitted in random directions when the energized electrons in an atom fall to a lower state of energy. This random direction, coupled with an unfathomable amount of photons means that a source of light will radiate in all directions equally. If you wanted a spotlight effect with the sun, you would need something to either reflect the photons or absorb them.

Both seem equally unlikely however because we can't observe any reflective objects or see how it's possible that some matter could be absorbing the light since the sun is already a black body.
Scepti, this idiocy needs to stop and it needs to stop right now. You are making a mockery of this fine forum with your poor trolling. You are a complete disgrace.

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PizzaPlanet

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #92 on: July 03, 2011, 10:24:52 PM »
Then you completely missed my point.

My point is not that daylight at the equator is 12 hours, give or take 8 minutes.  My point is that daylight at the equator is 12 hours (give or take 8 minutes) EVERY DAY OF THE YEAR.
So you were proving Wallace right? Okay.
hacking your precious forum as we speak 8) 8) 8)

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #93 on: July 04, 2011, 02:32:04 AM »

Here's a question - can you focus light without any sort of artificial or mechanical means?  Removing of lenses and blinders to the light source - what would it's impact be?

Berny
OT ?
Every now and then there appears a humongous error in physics concepts in this forum, and this one is among the worst. There are no means, mechanical, optical, electromagnetic or otherwise to focus a beam of light to the point where the light travels in only one direction. This is one of the most basic characteristics of a wave. If you want a detailed description of the phenomenon you can look at:

    http://en.wikipedia.org/wiki/Airy_disk

You can focus a theater spotlight to a place of the same size of the diameter of the spotlight, getting a beam of light that is mostly uni-directional, but only for the small distances of a theater. And not even in a small theater can you get a totally uni-directional beam of light. If you could, you would not see the spotlight unless you step into the beam of light.

And I am not even talking about dust particles and other impurities in the air. Even in total vacuum you cannot have a perfectly uni-directional beam of light.

There is also no way whatsoever to avoid the "inverse square law". The light will come out of the light source covering an angle of at least arcsin(1.22 * wavelength / lens_diameter) and therefore will cover about four times the area when the distance to the source is doubled.

People in this forum are accustomed to making physical theories as they go, and in this case at least two forum members slept all the way through basic optics in freshman college. After so much sleeping in class you should have the decency to not fill your ignorance with made up physics theories.

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #94 on: July 04, 2011, 02:43:47 AM »
Actually, A.R. Wallace is right. The inverse square law applies to situations where the energy density of light weakens as it travels further. A spotlight would have the same energy density at every point on along the beam.
But of course, spotlights aren't perfect. As you mentioned, there is a little bit of light dispersion within the spotlight itself and dust and whatnot absorbs some of the light along its journey - but these factors don't account for an inverse square law relationship as you would expect from a spherical radiating source.
Please, Puttah, you know more physics than this. Read my previous post.

The inverse square law applies to all cases in which light covers more area as it travels further away from the source, and that is all the cases where light travels in vacuum, air or another homogeneous substance.

There may be cases in which light has other distributions, but only at short distances from the source. For example, if you focus light on one point it will have a maximum density at one point, but at long distances it will follow the inverse square law, because light is a wave.

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Puttah

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #95 on: July 04, 2011, 05:23:10 AM »
may be cases in which light has other distributions, but only at short distances from the source. For example, if you focus light on one point it will have a maximum density at one point, but at long distances it will follow the inverse square law, because light is a wave.
Yes, it will follow the law at long distances. If we consider a perfect laser (this is how I pictured the spotlight to be since I think the others were neglecting the slight divergence angle) then I don't believe it happens to follow the inverse square law for distance as short as within a theater.
Sadly it wouldn't be simple to conduct an experiment on this. The spotlight can hardly be approximated into a point source.
Scepti, this idiocy needs to stop and it needs to stop right now. You are making a mockery of this fine forum with your poor trolling. You are a complete disgrace.

Re: Regarding your FAQ, I think you need to update this statement:
« Reply #96 on: July 04, 2011, 06:37:45 AM »
The inverse square law applies to all cases in which light covers more area as it travels further away from the source, and that is all the cases where light travels in vacuum, air or another homogeneous substance because light is a wave.

This is just so WRONG.   I asked if you wanted examples and the math.  You did not answer.  Perhaps you don't want to know the answer?
« Last Edit: July 04, 2011, 06:39:19 AM by A.R. Wallace »

Re: Regarding your FAQ, I think you need to update this statement:
« Reply #97 on: July 04, 2011, 06:49:00 AM »
Here's a question - can you focus light without any sort of artificial or mechanical means?  Removing of lenses and blinders to the light source - what would it's impact be?

Well I can't.  But I can't create the sun, either.   At least not on that scale.  Don't forget reflectors - such as found on search lights.  Very tight beam there with a very shallow barrel and no lens.

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #98 on: July 04, 2011, 08:08:45 AM »
The inverse square law applies to all cases in which light covers more area as it travels further away from the source, and that is all the cases where light travels in vacuum, air or another homogeneous substance because light is a wave.

This is just so WRONG.   I asked if you wanted examples and the math.  You did not answer.  Perhaps you don't want to know the answer?
Show me the maths, and show me how you are going to avoid the diffraction patterns of light.

Please tell me what part of this scenario is wrong: The Sun is less than 50000 km above us and illuminating areas of Earth at least 40000 km wide, at least some of the time. And the Sun is less than, say, 500 km wide. Therefore, in FE's only well defined model, the Sun is far and away different from an uni-directional source of light, and therefore the inverse square law applies, even in FE's Sun.

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Puttah

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #99 on: July 04, 2011, 08:18:34 AM »
If we take the simple case where the top half (the part we can't see) of the sun's rays are being reflected towards the Earth, then this means the power of the light reaching us doubles, but it's still proportional to the inverse square law. I thought we were talking about spotlights though?
Scepti, this idiocy needs to stop and it needs to stop right now. You are making a mockery of this fine forum with your poor trolling. You are a complete disgrace.

Re: Regarding your FAQ, I think you need to update this statement:
« Reply #100 on: July 04, 2011, 09:22:50 AM »
I'll give you an example with a very tight beam - a laser.
Suppose you have a very bright laser with a beam diameter of 3mm.  You measure the radiated power at 1m and find it is 1W.  Now you shine that laser at a target 8Km away (5 miles) and the spot on the target is 3m across.  Not the tightest laser beam, but OK.

The beam now covers a surface area 1,000,000 times larger than it did at 1m. Area = πr2  The total energy is the same (minus air absorption) just spread out over a much larger area.  If you took your power meter with a 3mm aperture (same as the beam's original diameter) you'd measure 1 microwatt of power.  Got it?  The beam now covers 1 million times more surface area so at any given point it is 1 million time less powerful.

Now that we know that - calculate the light power at your target using the inverse square law from 1m to 8000m.  Tell me if they are close to the same.

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markjo

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #101 on: July 04, 2011, 09:49:31 AM »
Then you completely missed my point.

My point is not that daylight at the equator is 12 hours, give or take 8 minutes.  My point is that daylight at the equator is 12 hours (give or take 8 minutes) EVERY DAY OF THE YEAR.
So you were proving Wallace right? Okay.
No.  I was pointing out that Wallace's animation showed significantly more or less than 12 hours of daylight at the equator during the solstices.  Even during the equinox, the curved edge of the oval should have been straight in order to provide an accurate representation of the daylight pattern.
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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #102 on: July 04, 2011, 10:06:32 AM »
Even during the equinox, the curved edge of the oval should have been straight in order to provide an accurate representation of the daylight pattern.

It would IF the map used in my animation is accurate.  I doubt it is.  All these FE maps, pretty as they are, are based on a RE model then projected on a disc.  The real FE should be somewhat different to correspond to observed sunrise/sunset times, distances and other phenomena.

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #103 on: July 04, 2011, 11:28:39 AM »
I'll give you an example with a very tight beam - a laser.
Suppose you have a very bright laser with a beam diameter of 3mm.  You measure the radiated power at 1m and find it is 1W.  Now you shine that laser at a target 8Km away (5 miles) and the spot on the target is 3m across.  Not the tightest laser beam, but OK.

The beam now covers a surface area 1,000,000 times larger than it did at 1m. Area = πr2  The total energy is the same (minus air absorption) just spread out over a much larger area.  If you took your power meter with a 3mm aperture (same as the beam's original diameter) you'd measure 1 microwatt of power.  Got it?  The beam now covers 1 million times more surface area so at any given point it is 1 million time less powerful.

Now that we know that - calculate the light power at your target using the inverse square law from 1m to 8000m.  Tell me if they are close to the same.
Now I am starting to worry. Maybe you are not trolling, Maybe you are positively, honestly unaware of the difference between conservation of energy and inverse square law!

What you are saying, that the same watt of power is there when you look at it 8 km away, is the principle of conservation of energy! What you are saying that does not apply to spotlights is the  inverse square law! The inverse square law is exactly what you described in your explanation. At a certain distance the energy density will be a million times lower and the area covered will be a million times larger than close to the source.

If you want to apply your inverse square law again, at 16 km the energy density will be a quarter of the energy density at 8 km, and the area covered will be quadrupled. You are giving the textbook example of inverse square law and saying it does not apply. How much lower can you fall?

PS. I do not know what power meter you are using for your thought experiment, but it is definitely something you pulled out of your ... lets say "imagination". The real meter you would have is a light meter, which indirectly measures light density (if you know how to use it), not power.
« Last Edit: July 04, 2011, 11:35:02 AM by trig »

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #104 on: July 04, 2011, 11:44:54 AM »
If we take the simple case where the top half (the part we can't see) of the sun's rays are being reflected towards the Earth, then this means the power of the light reaching us doubles, but it's still proportional to the inverse square law. I thought we were talking about spotlights though?
It is terribly complicated to understand the ideas of FE'ers in part because they do not take the time to make a diagram of their world view.

I can only say that, yes, whatever they do with the Sun's light, either using the light from the "top" of the Sun or not, the inverse square law will apply because it is a direct consequence of the principle of conservation of energy.

I think we are really talking about magical spotlights, because any real kind will never, ever, illuminate the Earth correctly, assuming any Earth model from this forum. You will always have to add mirrors in the sky, or weird shades and anti-moons or whatever fancies them at the moment.

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #105 on: July 04, 2011, 12:12:38 PM »
OK, here is a link to the Flash animation.  Sorry I couldn't embed it here.   It works pretty well, give it a whirl.  See what mistakes you can find.
http://www.earthnotglobe.com/FE_sun.htm
So much work, such a terrible result.

Lets start with the best part: The northern hemisphere is very wrong, but not totally, definitely, absurdly wrong. We can say it is a good try, even though it does not explain the 24 hour daylight and 24 hour nighttime some days per year, north of the Arctic Circle.

But now lets look at the Southern hemisphere. In Antarctica you also have continuous daylight for months at a time, but this "model" does not even explain days longer than 12 hours in the southern hemisphere. Ask any Argentinian or Chilean and they will laugh you out of the room with this "model".

I was, in fact, visiting Punta Arenas, at the southernmost part of Chile, some years ago and daytime extended from before 4 am to past 9 pm. Your diagram does not even show how a 12 hour daytime would be possible in Punta Arenas.

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berny_74

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #106 on: July 04, 2011, 01:35:19 PM »
I was, in fact, visiting Punta Arenas, at the southernmost part of Chile, some years ago and daytime extended from before 4 am to past 9 pm. Your diagram does not even show how a 12 hour daytime would be possible in Punta Arenas.

I still find it funny how many of us have been to Punta Arenas.  A tourist town it was not.


It would IF the map used in my animation is accurate.  I doubt it is.  All these FE maps, pretty as they are, are based on a RE model then projected on a disc.  The real FE should be somewhat different to correspond to observed sunrise/sunset times, distances and other phenomena.

Wouldn't that be an easy start to making an FE map?  All the major population centers have accurate sunrise/sunset/noon times so finding longitudinal distances should be easy enough.  Next is north-south distances that might be trickier.

All that info is pretty much available on the net.

Berny
Lock is fixed
To be fair, sometimes what FE'ers say makes so little sense that it's hard to come up with a rebuttal.
Moonlight is good for you.

Re: Regarding your FAQ, I think you need to update this statement:
« Reply #107 on: July 04, 2011, 05:45:03 PM »
Now I am starting to worry. Maybe you are not trolling, Maybe you are positively, honestly unaware of the difference between conservation of energy and inverse square law!

Sigh..... I hand it to you on a silver platter and just ask you to do the inverse square part - and you don't!  What more can I do?  Is the light at 8000 meters 1/1000000 of the light at 1m according to the inverse square law?  I'll wait for the answer.

As for the animation, I agree and have even stated as much, if you care to read my posts.  It was an attempt to to see how it might work.  It works well for north of the equator, poorly for the south.  I've already stated that.  ::)

Go actually DO something - then come talk to me.

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trig

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Re: Regarding your FAQ, I think you need to update this statement:
« Reply #108 on: July 05, 2011, 03:26:37 AM »
Now I am starting to worry. Maybe you are not trolling, Maybe you are positively, honestly unaware of the difference between conservation of energy and inverse square law!

Sigh..... I hand it to you on a silver platter and just ask you to do the inverse square part - and you don't!  What more can I do?  Is the light at 8000 meters 1/1000000 of the light at 1m according to the inverse square law?  I'll wait for the answer.

As for the animation, I agree and have even stated as much, if you care to read my posts.  It was an attempt to to see how it might work.  It works well for north of the equator, poorly for the south.  I've already stated that.  ::)

Go actually DO something - then come talk to me.
Get your terms straight so that we can even have a conversation:
Is the light density at 8000 meters 1/1000000 of the light density at 1 meter? YES (assuming the circumstances you describe).
Is the light's total power flux at 8000 meters  1/1000000 of the light's  total power flux at 1 meter? NO.

Talking about "the light" instead of one specific, measurable parameter of it is just changing a physics problem into a cheap word game.

What you are handing on a silver platter is your right not to be called stupid or ignorant. But after working with light since the Johnson administration and not being able to talk coherently about luminous flux (the total production of light by a source, measured in lumens) and illuminance (the density of light traveling through a given area, measured in lux), we can only wonder why you still do not grasp their meanings.