# Mapping on the cheap - spotlight method

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#### Sliver

• 557
##### Re: Mapping on the cheap - spotlight method
« Reply #30 on: May 29, 2010, 05:50:00 AM »
the sun is a floodlight
and floodlights dont always shine in a circle pattern

spotlights however do.
the sun is NOT a spotlight
And you, who claims they want to believe, has refused to try the experiment I gave you.  Here it is again for you...

Quote
According to the FAQ, the Sun is 32 miles across and 3000 miles away.  A ratio of 4/375.  You could also say that the distance is 93.75 times greater than the size of the object.  Let's apply this ratio to something else.  Hmmm, I know!  A U.S. quarter.  The quarter measures .96875in across.  That width would mean that the quarter would have to be 7.57ft above the surface.  Now, with the sun being 32 miles wide, and the Earth being 24,900 miles wide, that means that the Earth is 778.125 times larger.  Apply that to the size of the quarter, and we get a circular surface measuring 62.817ft wide.  So there you go.  Use a spotlight, use a floodlight, I really don't care which.  But let's see you get a lightsource with a surface area of .7367 square inches to properly illuminate a surface measuring 3097.59 square feet from a height of only 7.57ft.
« Last Edit: May 29, 2010, 06:19:42 AM by Sliver »

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#### Crustinator

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##### Re: Mapping on the cheap - spotlight method
« Reply #31 on: May 29, 2010, 06:04:35 AM »
Not all spotlights are circular.

The clue is in the name. "Spot". A spot would usually be thought of as circular. Hence the many times Tom Bishop has argued that we're seeing the edge of the "spotlight" sun.

However if you want to show otherwise, proceed.

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#### flyingmonkey

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##### Re: Mapping on the cheap - spotlight method
« Reply #32 on: May 30, 2010, 01:54:58 AM »
the sun is a floodlight
and floodlights dont always shine in a circle pattern

spotlights however do.
the sun is NOT a spotlight

Since when does the Sun have a giant reflector around it to make it a floodlight?

You realize that "floodlight" doesn't specify a shape, most floodlights still make a circular shape.

#### parsec

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##### Re: Mapping on the cheap - spotlight method
« Reply #33 on: May 30, 2010, 03:11:11 AM »
You can tell where on the circle to put the points because the latitude of the location tells you how far up or down you need to put the point.
How?

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#### flyingmonkey

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##### Re: Mapping on the cheap - spotlight method
« Reply #34 on: May 30, 2010, 07:03:19 AM »
You can tell where on the circle to put the points because the latitude of the location tells you how far up or down you need to put the point.
How?

Well you agree that latitudes and longitudes are correct for both models?

If it is sunrise at a certain point and sunset at another, you can (using the latitudes) figure out where on the edge of the circle they are because the point will intersect the Spotlight area.

You would also have to take into account the time of year (How far North/South the Sun is compared to Equator) to get a better approximation.

In keeping the Spotlight the same size, it would eventually scale itself out.

#### parsec

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##### Re: Mapping on the cheap - spotlight method
« Reply #35 on: May 30, 2010, 08:00:27 AM »
You can tell where on the circle to put the points because the latitude of the location tells you how far up or down you need to put the point.
How?

Well you agree that latitudes and longitudes are correct for both models?

If it is sunrise at a certain point and sunset at another, you can (using the latitudes) figure out where on the edge of the circle they are because the point will intersect the Spotlight area.

You would also have to take into account the time of year (How far North/South the Sun is compared to Equator) to get a better approximation.

In keeping the Spotlight the same size, it would eventually scale itself out.
lolwut? If you draw the spotlight edge as circular doesn't that mean that the shape is circular by construction?

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#### flyingmonkey

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##### Re: Mapping on the cheap - spotlight method
« Reply #36 on: May 30, 2010, 08:09:24 AM »
Pray tell, what shape would a square or triangle produce?

How does a source of light produce anything but a circular shape if there is nothing to direct the light?

I'd love to know.

#### parsec

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##### Re: Mapping on the cheap - spotlight method
« Reply #37 on: May 30, 2010, 09:07:41 AM »
Pray tell, what shape would a square or triangle produce?

How does a source of light produce anything but a circular shape if there is nothing to direct the light?

I'd love to know.
It depends.

#### Sliver

• 557
##### Re: Mapping on the cheap - spotlight method
« Reply #38 on: May 30, 2010, 10:09:22 AM »
Pray tell, what shape would a square or triangle produce?

How does a source of light produce anything but a circular shape if there is nothing to direct the light?

I'd love to know.
It depends.
I think the troll needs to elaborate on what "It depends" upon.

#### parsec

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##### Re: Mapping on the cheap - spotlight method
« Reply #39 on: May 30, 2010, 10:44:13 AM »
Pray tell, what shape would a square or triangle produce?

How does a source of light produce anything but a circular shape if there is nothing to direct the light?

I'd love to know.
It depends.
I think the troll needs to elaborate on what "It depends" upon.
Please draw a light source in the center of a sphere and a plane touching the sphere at some point. Now, let's suppose the source creates a circular lighted region on the sphere. What is its projection on the plane?

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#### Crustinator

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##### Re: Mapping on the cheap - spotlight method
« Reply #40 on: May 30, 2010, 11:04:05 AM »
Please draw a light source in the center of a sphere and a plane touching the sphere at some point. Now, let's suppose the source creates a circular lighted region on the sphere. What is its projection on the plane?

I've no idea what any of that is supposed to mean.

Why don't you just explain what "it" depends on?

#### parsec

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##### Re: Mapping on the cheap - spotlight method
« Reply #41 on: May 30, 2010, 11:07:50 AM »
It depends on your grasp of Euclidean geometry.

#### Sliver

• 557
##### Re: Mapping on the cheap - spotlight method
« Reply #42 on: May 30, 2010, 03:24:24 PM »
Pray tell, what shape would a square or triangle produce?

How does a source of light produce anything but a circular shape if there is nothing to direct the light?

I'd love to know.
It depends.
I think the troll needs to elaborate on what "It depends" upon.
Please draw a light source in the center of a sphere and a plane touching the sphere at some point. Now, let's suppose the source creates a circular lighted region on the sphere. What is its projection on the plane?
So, like a light bulb touching, say a piece of cardboard?

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#### Crustinator

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##### Re: Mapping on the cheap - spotlight method
« Reply #43 on: May 30, 2010, 05:24:52 PM »
It depends on your grasp of Euclidean geometry.

Go on...

#### Seņor R.

• 19
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##### Re: Mapping on the cheap - spotlight method
« Reply #44 on: May 30, 2010, 06:21:00 PM »
Oh, hey, it turns out this has been done before.

But it turns out the Earth is a sphere, so you need to break it up into segments if you want a flat map.

#### parsec

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##### Re: Mapping on the cheap - spotlight method
« Reply #45 on: May 30, 2010, 06:32:00 PM »
It depends on your grasp of Euclidean geometry.

Go on...
It isn't a circle.

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#### Crustinator

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##### Re: Mapping on the cheap - spotlight method
« Reply #46 on: May 31, 2010, 04:14:57 AM »
It isn't a circle.

Go on. Tell me what it is.

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#### Dr Disprover

• 14
##### Re: Mapping on the cheap - spotlight method
« Reply #47 on: May 31, 2010, 05:02:00 AM »
Wait a sec, wouldn't the sun have to get larger and smaller, because the 'pole' and 'ice wall' would be illuminated then darkened for six months of each year. How does that work? (Never in the FAQ)

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#### flyingmonkey

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##### Re: Mapping on the cheap - spotlight method
« Reply #48 on: May 31, 2010, 06:01:37 AM »
What parsec is trying to get is that the light from the globular spheroid projected onto the flat map would indeed be a different shape, but it would still be circular.

Infact, here it is here:

That's only a Northern Hemispheres Summer though, if I were to draw the Southern Hemispheres Summer, the gray and light areas would be switched - How screwy is that.

What's funny, is this is basically the reverse of this entire experiment.