# Has the sun's irradiance become whiter in the past few decades?

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#### Classical Motion

I believe the sun has a rarefied core. With a gravity shell around it. This gives the core a surrounded temp/heat source, and also the ability to accelerate to the high temps needed for fusion. The same reason the corona is hotter than the surface. Acceleration time.

The core has less density, and a higher temp because of it.

#### billslugg

At the center of the Sun, where the density is 150 times that of water and the temperature 30 million degrees F, the rate of fusion heat generation per unit volume is about 1% of the human body at rest.

Sun output = 4e26 watts.
Core is innermost 24% of solar radius.
Core volume is 2e25 m^3
Specific heat production of Sun's core = 4e26/2e25 watts/m^3 = 20 watts per cubic meter
Human produces 300 BTU/hr at rest.
Electrical equivalent is 90 watts.
Human weighs about 150 pounds or 60 kg.
Human volume is 0.06 m^3
Human specific heat generation is = 90/0.06 W/m^3 = 1,500 watts per cubic meter.

Humans over the Sun, on a volume basis, by a ratio of 1,500/20 or 75.
Given the Sun needs 150 times the mass, in the same volume, to produce but 1.3% of a human, we beat it by a factor of 11,250 on a unit mass basis.

#### Classical Motion

Kinda sounds like cold fusion results. I am now, unimpressed with Sol's fusion.

#### Helio

At the center of the Sun, where the density is 150 times that of water and the temperature 30 million degrees F, the rate of fusion heat generation per unit volume is about 1% of the human body at rest.

Sun output = 4e26 watts.
Core is innermost 24% of solar radius.
Core volume is 2e25 m^3
Specific heat production of Sun's core = 4e26/2e25 watts/m^3 = 20 watts per cubic meter
Human produces 300 BTU/hr at rest.
Electrical equivalent is 90 watts.
Human weighs about 150 pounds or 60 kg.
Human volume is 0.06 m^3
Human specific heat generation is = 90/0.06 W/m^3 = 1,500 watts per cubic meter.

Humans over the Sun, on a volume basis, by a ratio of 1,500/20 or 75.
Given the Sun needs 150 times the mass, in the same volume, to produce but 1.3% of a human, we beat it by a factor of 11,250 on a unit mass basis.
I get about 13.5 humans (150 lbs. each) Per cubic meter; 19.4 watts per cu meter from solar core, so humans 62-1/2x more powerful,…but usually not as bright.

billslugg

#### billslugg

Humans don't shine unless under pressure.

Helio

#### Classical Motion

No wonder they live so long. And size does matter.

Helio and billslugg

#### Classical Motion

So if we compare heat to size, we live on a much hotter object than the sun?

That didn't come out right. What's the heat production in earth's core?

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#### billslugg

The Sun has a lower heat production rate in each of its cubic meters than a cubic meter of humans.
Because the Sun is so large, there are a lot of BTUs to deal with.
Because the surface to volume ratio of the Sun is so low compared to humans, there is far less radiation area per BTU at the Sun therefore the Sun must be much hotter to radiate the heat.

What is Earth core heat production rate?
The Earth core is 1221 km in radius.
Earth core volume is thus 8e18 m^3.
Earth heat budget is 47 TW. (Includes primordial heat still escaping).
Earth heat budget = 6 microwatts per cubic meter.
Very small as compared to the Sun (20 w/m^3).

Classical Motion

#### lilianawale

The perception of the Sun as yellow in childhood drawings and its current appearance as white or slightly yellowish in the sky is primarily due to atmospheric scattering. The Sun emits white light, but as sunlight enters Earth's atmosphere, shorter wavelengths like blue and violet scatter more, while longer wavelengths like red, orange, and yellow scatter less.
When the Sun is higher in the sky and there's less atmospheric scattering, it appears closer to white. Changes in the Sun's internal processes, such as variations in helium levels, do not significantly impact its visible color over human timescales. The Sun's inherent color, determined by its surface temperature, has remained relatively stable, and any noticeable changes would require geological or astronomical timescales to manifest.

Helio and billslugg

#### Atlan0001

"Red sun in the morning (coming up), sailor take warning! Red sun at night (going down), sailor's delight!"

#### Helio

The perception of the Sun as yellow in childhood drawings and its current appearance as white or slightly yellowish in the sky is primarily due to atmospheric scattering. The Sun emits white light, but as sunlight enters Earth's atmosphere, shorter wavelengths like blue and violet scatter more, while longer wavelengths like red, orange, and yellow scatter less.
When the Sun is higher in the sky and there's less atmospheric scattering, it appears closer to white. Changes in the Sun's internal processes, such as variations in helium levels, do not significantly impact its visible color over human timescales. The Sun's inherent color, determined by its surface temperature, has remained relatively stable, and any noticeable changes would require geological or astronomical timescales to manifest.
Yes. My avatar shows nicely the Sun’s color. The plastic color pieces are for color calibration.

So, given your scattering (Rayleigh) arguments, showing that blue light is scattered by our atmosphere — giving us our blue sky — is the color one must add to the white image to represent its true color, as seen in space.

Therefore, there’s no way the Sun can be a yellow star since adding blue to white never yields a yellow result. Snow is white, clouds are white, the Moon is white, etc.

This begs the question how it became deemed as yellow, which is, IMO, an interesting story.

Here is part 3 of 3 of a zany explanation of one amateur’s attempt in 2008 to resolve the color conundrum….Here.

#### billslugg

The only time I can look at the Sun is when it is on the horizon, usually about half a diameter from the horizon. Looking at it when overhead can't be done except with just the right amount of fog. I have seen sunspots with my naked eye under such conditions. At that point, it looks white to me.

#### Helio

The only time I can look at the Sun is when it is on the horizon, usually about half a diameter from the horizon. Looking at it when overhead can't be done except with just the right amount of fog. I have seen sunspots with my naked eye under such conditions. At that point, it looks white to me.
I've had some rare moments of clouds and fog to allow a quick glance, but I've yet to see any spots. But, there are numerous ancient accounts of them.

But your white result for a setting Sun suggests something extra is happening. Water looks blue because it absorbs more of the red light. If this is happening then the loss of blue-end combined with a loss of the red-end perhaps explains it.

Clouds, however, have particles too large to allow color separation. This is known as Mie Scattering, so the clouds are scattering light mostly forward and backward, not to the side as much, but with little change in color. Hence it argues for a white star.

But I would have guessed that your fog would be more Mie Scattering than absorption. Perhaps traveling through maybe 10 atmospheres makes a difference.

#### Helio

"Red sun in the morning (coming up), sailor take warning! Red sun at night (going down), sailor's delight!"
Yes. The extra morning scattering due to distant storm coditions explains the need for ship warnings.

Atlan0001

#### billslugg

Sorry, I wrote it wrong. I MEANT to say the Sun looks yellow on the horizon but white through overhead fog.
Bottom line: The Sun is white.

Atlan0001

#### Helio

Sorry, I wrote it wrong. I MEANT to say the Sun looks yellow on the horizon but white through overhead fog.
Bottom line: The Sun is white.
Ah, that's better.

billslugg

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