Is the Solar Constant Really 340 W/m^2 or 680 W/m^2?

[waynesplash]

TL;DR Summary

Which is the right answer in the real World, a or b ???

The solar constant is only on one side of the Earth, however it moves around and the Sun gives out it's energy/heat all over the Earth in 24 hours. And the seas and land have heated up over time.

However I got told this,
No its not. By definition the solar constant is referring to a 2 dimensional plane. This is not debatable. It is most definitely NOT what is hitting one side of Earth. The solar constant on a sphere = 340 W/m^2However I would say the Sun is not shining on the other side of the Earth, thus solar constant = 680 W/m^2, so why do some physicists divide it by 2 and get 340W/m^2 ?The Sun shines its solar constant on a flat disc, the solar constant = 680 W/m^2 do you agree ?

1,
Do you agree on a flat disc the solar constant = 680 W/m^2 ?

2;
Do you agree the solar constant only hits one side of our Earth at one time ? Yes I know it moves around the Earth, but its basically hitting one side of the Earth, and that solar constant = 680 W/m^2 ?

3,
Two men, one man has a light beam, shines a light on one side of the Earth, he gets paid 1000,000, another man has a light beam, but does not shine a light on the other side of the Earth, he gets paid nothing.

a;
If you average this out both men get 500,000.

b;
In the real World, just one man has 1000,000.

c;
Which is the right answer in the real World, a or b ?Half the Earth is in daylight, half the Earth is in dark, in some World as some average, half the World is half light, and the other half the World is half light. BUT, in the real World its NOT like that.I all don't understand why some think they should half the power of the Suns 680 W/m^2 ? The Suns power is NEVER 340 W/m^2, its always 680 W/m^2 ? Its only hitting one side of the Earth, so why divided ?e;
Two men, one man has a light beam, one shines a light on full power on one side of the Earth, another man has a light beam, but does not shine a light on the other side of the Earth.QUESTION, does one man use half his light beam and shine it on one side of the Earth, and does the other man use half his light beam and shine it on the other side of the Earth ? Or does just the one man shine his light beam full on, on one side of the Earth ?Dividing dose not make sense in what happens in the real World, do you agree ? If not please explain how when the suns constant = 680 W/m^2, but some magically half it, when its never half. I don't get why some half something that’s never half, and its only hitting one side or the Earth at a time ?

Wayne

 

[russ_watters]

This is just a definition. What value is there in arguing against a definition?

 

[mjc123]

From https://en.wikipedia.org/wiki/Solar_constant:

"The solar constant (GSC) is a flux density measuring mean solar electromagnetic radiation (solar irradiance) per unit area. It is measured on a surface perpendicular to the rays, one astronomical unit (AU) from the Sun (roughly the distance from the Sun to the Earth).

The solar constant includes all types of solar radiation, not just the visible light. It is measured by satellite as being 1.361 kilowatts per square meter (kW/m²) at solar minimum and approximately 0.1% greater (roughly 1.362 kW/m²) at solar maximum.[1]
...
The Earth receives a total amount of radiation determined by its cross section (π·RE²), but as it rotates this energy is distributed across the entire surface area (4·π·RE²). Hence the average incoming solar radiation, taking into account the angle at which the rays strike and that at anyone moment half the planet does not receive any solar radiation, is one-fourth the solar constant (approximately 340 W/m²)."

This means that at any moment, the average radiation striking the sunlit surface of the Earth (2·π·RE²) is 680 W/m². To answer your question 3, both statements a and b are true. It's a question of which is a more useful way of stating the facts in a given context.

 

[mfb]

I give you a $100 bill every hour. Giving you the bill takes maybe 2 seconds, the other 3598 seconds in an hour you don't receive money. Would you say you earn $100 in 2 seconds? Or would you say you make $100/hour?

To calculate temperatures on Earth the average over the full surface is more important than the average over the sunlit half. You can define your own constant, waynesplash's Solar constant, which considers the sunlit half only.

 

[stefan r]

Do you agree on a flat disc the solar constant = 680 W/m^2 ?

On a flat disc would depend on the angle between the surface and the incident radiation. A flat disc would also have a dark side (assuming one light source).

Light intensity decreases with the square of distance.

Edit: What does this have to do with Carbon dioxide?

 

[russ_watters]

On a flat disc would depend on the angle between the surface and the incident radiation. A flat disc would also have a dark side (assuming one light source).

I think an unstated assumption would be that it's perpendicular, however the number given by the OP was still wrong at that; it should be 1360w/m²

Edit: What does this have to do with Carbon dioxide?

Nothing. I've changed the title to more accurately represent the subject.

 

[berkeman]

I've changed the title to more accurately represent the subject.

LOL, that confused me. I was about to give the OP a bad time for starting another thread on the same subject...