The Sun, Our Nearest Star

[Cyphermage]

I'm just listening to Randi's latest appearance on "The Skeptics Guide to the Universe." Excellent interview. Update on his bypass. Some Benny Hinn debunking. Cars with water-only engines. Fox News reports on the water car. Oh-Oh...

Randi: The announcer actually says, "He generates from this torch heat which is greater than the surface of the sun." Duh! The surface of the sun is at millions of centigrade degrees. This from a hydrogen flame? Not likely.

Would anyone care to debunk? Hint. Your TV, at a recommended color temperature of 6500K, is blue-white. The sun is yellow.

 

[The_Fire]

[nitpick]

Actually the correct kelvin degree of the midday sun on a cloudless day at noon is 5200 kelvin which makes the color of the sun blue.

[/nitpick]

 

[wollery]

The temperature of the Sun's photosphere (the visible surface) is about 5800K. It's corona is about 1,500,000K

It's a G2V star (main sequence dwarf), and is yellowish-orange in colour.

info here and here

 

[Cyphermage]

[nitpick]

Actually the correct kelvin degree of the midday sun on a cloudless day at noon is 5200 kelvin which makes the color of the sun blue.

[/nitpick]

The surface temperature of the Sun is about 5750k. We know that the product of the temperature in Kelvins with the peak wavelength is the constant 2.898*10^7. This allows us to determine the color of a star from its temperature, and vice versa. The sun peaks at about 504 nanometers, which is in the middle of the visible spectrum. The sun is a yellow star of spectral type G2V.

 

[rjh01]

Actually the colour of the sun is white. Proof - what colour is a white piece of paper in sunlight? Answer white. The sun is red when it is near the horizon because the blue light is scattered.
The core of the sun is millions of degrees C for fusion to occur.

 

[Cyphermage]

Actually the colour of the sun is white. Proof - what colour is a white piece of paper in sunlight? Answer white. The sun is red when it is near the horizon because the blue light is scattered.
The core of the sun is millions of degrees C for fusion to occur.

Due to some processing your brain does called "Color Constancy", you see colors correctly in pretty much any tint of light. The color of the sun is a function of the temperature of its surface only, and the color of the sun is yellow. The outer atmosphere of the sun is over a million degrees, and the core is at tens of millions of degrees, but it's only the surface temperature that determines the color we see. Take a sun filter or some exposed film and look through it at the sun. You will see a little yellow disk with black spots on it.

 

[The_Fire]

¨Well, I learn something new everyday around here it seems.

ETA: Oh bloody hell....This is what happens when you are not doing your trade for a prolonged strech of time and gets out of shape:
I checked my papers and should have written 5500 - 5600 kelvin, not 5200!
*Decides to do a rather extensive review of her skills/knowledge before she rusts completely*

ALSO: For some reason I failed to see that we were talking about the surface of the sun, not how it looks/measures out down here.

 

[rjh01]

Due to some processing your brain does called "Color Constancy", you see colors correctly in pretty much any tint of light. The color of the sun is a function of the temperature of its surface only, and the color of the sun is yellow. The outer atmosphere of the sun is over a million degrees, and the core is at tens of millions of degrees, but it's only the surface temperature that determines the color we see. Take a sun filter or some exposed film and look through it at the sun. You will see a little yellow disk with black spots on it.

I do not have a sun filter. Looking at the sun via exposed film is dangerous.
If you want to cut out 'colour constancy' then take a photo of a white piece of paper. Correctly exposed, if it was taken using sunlight it will be white (the camera may want to underexpose it and make it gray). Taken indoors with indoor lights it will be yellow because the light is a yellow colour.

Another way to find out the colour is to put the light though a prism and split the colours. You will find all the colours with a few dark lines. Or an even easier way is to look at a rainbow. All colours present. If the sun was yellow you will find significant colours missing like all of red and blue.

 

[Capsid]

Would anyone care to debunk? Hint. Your TV, at a recommended color temperature of 6500K, is blue-white. The sun is yellow.

I believe cyphermage covered it, but to reiterate, colour temperature and heat temperature are not the same thing.

 

[gfunkusarelius]

is there a transcript of this interview online? i am interested in hearing his take on the "power from water" bit. i have seen this a lot of other places now and there are tons of people taken in by it...

ETA: i know it has been debated pretty thoroughly on these forums

 

[Cyphermage]

is there a transcript of this interview online? i am interested in hearing his take on the "power from water" bit. i have seen this a lot of other places now and there are tons of people taken in by it...

ETA: i know it has been debated pretty thoroughly on these forums

I don't know about a transcript, but you can download the show as a podcast at http://www.theskepticsguide.org/

 

[Cyphermage]

Looking at the sun via exposed film is dangerous.

Many things in life are dangerous.

Exposed silver-based black and white film is safe to look at the sun through, if you use enough of it. It blocks the non-visible stuff just as well as the visible.

Color film and non-silver-based black and white film are not safe to look at the sun through.

Better yet is a sun filter, or a #14 arc welder filter. If you are using the filter with a telescope or other optics, it should go in front of the device. NEVER use an eyepiece filter with a telescope. It will heat up and possibly crack, frying your eyeball before you can move your head out of the way.

 

[Meffy]

Another good sun viewing technique, eyepiece projection is easy, cheap, and safe as long as you keep the eyepiece pointed down (which makes sense if you want to look at the screen onto which the image is projected). It provides a BIG image that several people can view at the same time. Careful artists can even sketch the image directly onto paper.

 

[CapelDodger]

If you want to cut out 'colour constancy' then take a photo of a white piece of paper. Correctly exposed, if it was taken using sunlight it will be white ...

RGB wheightings, in film or devices, are calibrated against sunlight. A photo only demonstrates that the calibration is accurate, not that the resultant colour is white. It's what appears white to us in sunlight.

"White" is an entirely subjective, human concept. There's no white (or black) in the spectrum, which is the only objective measure.

 

[Art Vandelay]

"White" is an entirely subjective, human concept. There's no white (or black) in the spectrum, which is the only objective measure.

There most certainly is an objective black: no light is black.

Randi: The announcer actually says, "He generates from this torch heat which is greater than the surface of the sun." Duh! The surface of the sun is at millions of centigrade degrees. This from a hydrogen flame? Not likely.

Actually, there's another problem (other than the poor sentence structure). There's a difference between heat and temperature. Generating as much heat as the sun means putting out as much energy as the sun.

The surface temperature of the Sun is about 5750k. We know that the product of the temperature in Kelvins with the peak wavelength is the constant 2.898*10^7.

Uh... units?

Actually the colour of the sun is white. Proof - what colour is a white piece of paper in sunlight? Answer white. The sun is red when it is near the horizon because the blue light is scattered.

When people talk of the color of the sun, they're talking about the peak wavelength. Truly white light would be of equal intensity at each wavelength, which would mean infinite power.

Take a sun filter or some exposed film and look through it at the sun. You will see a little yellow disk with black spots on it.

But that doesn't mean anything; we see the sun through the filter of the atmosphere.

 

[rjh01]

'The sun's actual light is mostly white, with a little yellow.'

Reference http://www.madsci.org/posts/archives/dec99/945169710.As.r.html

 

[Cyphermage]

Uh... units?

<scribble scribble> Uh, 2.898*10^7 Angstrom-Kelvins

But that doesn't mean anything; we see the sun through the filter of the atmosphere.

We can still tell pretty well what color stars are through the atmosphere. Yellow-Orangy can be distinguished from Blue or Red without a great deal of difficulty.

 

[Cyphermage]

'The sun's actual light is mostly white, with a little yellow.'

Reference http://www.madsci.org/posts/archives/dec99/945169710.As.r.html

He's analyzing looking at the sun in space without a filter? Uh, ok.

If I look at the sun from earth through a filter, I see the sky as black, so there's no color constancy effect making the sun appear more yellow. My color receptors aren't getting saturated because I've appropriately reduced the intensity. So the only effect is a teensy amount of the more bluish light scattered by the atmosphere preferentially over other wavelengths.

In space, through an appropriate filter, the same conditions apply, except I see the extra blue light.

Is this enough to make a huge difference? Probably not.

Let's see what it looks like from SOHO.
The Sun From Space

Hmm, a smidge more orangey. Still a yellow star.