I'm not quite so sure, though

jwoodward48 wrote: Planck's Law predicts that all wavelengths will be emitted.

jwoodward48 wrote:If I plug a wavelength that O2 (or is that just O?) doesn't radiate, I get a nonzero expected emission energy

jwoodward48 wrote: Emissivity - is it the same for all wavelengths, given an object?

jwoodward48 wrote:
... So is the atmosphere one of the things with varying emissivitiee? I can't decipher what the parenthetical statement means. (Are none closed gases bodies?)

jwoodward48 wrote:
But... The atmosphere is opaque to several wavelengths, no? And it is (clearly) not opaque to visible light?

jwoodward48 wrote:
So its absorptivity, transmitivity, and emittivity (I probably misspelled half those words) depend on wavelength!

jwoodward48 wrote:Planck's Law predicts that all wavelengths will be emitted.

jwoodward48 wrote:
So since incoming radiation has different wavelengths from outgoing radiation, it can act differently on each, right?

jwoodward48 wrote:
So if a body has a high absorptivity and a low emittance, then incoming energy will exceed outgoing energy, right? (Assuming that it used to have identical emittance and absorptivity, with a temperature reflecting that.)

jwoodward48 wrote:
For one wavelength, yes. But the atmosphere has shortwave going down through it and longwave coming up - it can have different emissivity for longwave than absorptivity for shortwave, right?

jwoodward48 wrote:
Yes, the Sun has a broad spectrum, but it's almost entirely non-overlapping with the radiation from Earth.

Wait, we need to consider all those other things too? I thought we could prove it with only basic laws of thermodynamics and radiation.

Conduction and convection cannot cool the Earth system. Only radiation can carry energy through the aether. (I am aware that that theory was disproven centuries ago. It is my attempt at a joke.)

How would you like to go about including those other factors?

jwoodward48 wrote:
Yes, the Sun has a broad spectrum, but it's almost entirely non-overlapping with the radiation from Earth.

jwoodward48 wrote:
Wait, we need to consider all those other things too? I thought we could prove it with only basic laws of thermodynamics and radiation.

jwoodward48 wrote:
Conduction and convection cannot cool the Earth system. Only radiation can carry energy through the aether. (I am aware that that theory was disproven centuries ago. It is my attempt at a joke.)

jwoodward48 wrote:
How would you like to go about including those other factors?

jwoodward48 wrote:
So you're saying that most radiation from the Earth system originates in (that is, the photon was emitted from) the atmosphere?

jwoodward48 wrote:
So I take it we are discussing the 2nd?

jwoodward48 wrote:
First, let me start with the statement that some radiation from the atmosphere will be directed downward. This seems indisputable, but you never know.

jwoodward48 wrote:
You are claiming that a cool object cannot heat a warm object.

jwoodward48 wrote:
In a particular set of circumstances (no other energy source, etc.), this is true.

jwoodward48 wrote:
But in application, false.

jwoodward48 wrote:
Imagine that the background radiation were changed to be 100K, instead of 2K. Would this change the temperature of the Earth? (The corresponding energy of the background radiation increases with temperature, of course.)

jwoodward48 wrote:
...what? Huh? How is that contrived?

Maybe I'm bad at explaining. Let me quote:

"This apparent paradox is again based on a misunderstanding. Imagine you are standing outside on a cold winters night. It's really cold and you are soon chilled to the bone so you step inside. Inside it's a pleasant 20°C and almost immediately you feel warmer. But you are at 37°C and the room is 17°C cooler at 20°C how can it warm you, the second law of thermodynamics forbids it!

jwoodward48 wrote:
Everything radiates. The 2nd Law of Thermodynamics says that the radiation from an object cannot on its own raise a body to above the temperature of the object.

So if I have two iron rods, one at -10K and one at 10K, there is radiation going from the cooler to the warmer, but there is even more radiation going from the warmer to the cooler. If we increase the radiation from the cooler, say, by increasing its temperature to 0K, the temperature of everything the radiation reaches will increase, regardless of its temperature. Cooler things will heat up, obviously. But warmer things must have a separate energy source. Increasing one of the energy sources will obviously heat up the body. And it doesn't violate 2LoT because the cool rod isn't the only energy source.

jwoodward48 wrote:
Radiation, convection, conduction, the 2nd Law doesn't care. If the rate of heat loss is decreased, in the Earth system (since we have a sort-of-constant solar energy source), the temperature increases.

With radiation, we have radiation going both ways, and one direction having a greater flow. Conduction is a bit different, but it still has the same end result - the net heat flow will be from warmer to cooler, at a rate dependent on the temperature difference.

I have two metal bars, both being heated on one end by a heat lamp, and each with their opposite end placed by a cooler object. With Bar A, the cooler object is 273K. With Bar B, the cooler object is 1K.

Is there a difference in temperature between the two bars?

Into the Night wrote:We are bottom dwellers. We live at the bottom of a sea of air.

That air has a mass. Like any mass, it absorbs light converting it to thermal energy...

it takes time to heat it or cool it

it moves heat by combinations of convection, conduction, and radiation

it has a weight in a gravity field; it has inertia

and it can convert one form of energy into another.

Remember the cold 'rod' is open space itself. You can't just arbitrarily make it warmer or colder. That's why I discarded your contrived example. The cold side of it is meaningless.

jwoodward48 wrote: That was not a representation of the Earth. It would be a really shitty representation.

jwoodward48 wrote: I am showing that the 2nd Law cannot be applied the way you are using it.

jwoodward48 wrote: Energy flows from warmer to cooler, and vice versa - the net energy flow is from warmer to cooler,

jwoodward48 wrote: The 2nd LoT does not state that a change in a cooler source of radiation cannot lead to an increase in the temperature of a warmer body.

jwoodward48 wrote: Also, what's wrong with net energy flow?

IBdaMann wrote:

jwoodward48 wrote:You're missing the point - the air conducts heat to the ground, yes, but the ground is conducting even more heat to the air.

Here's where you are going to allow yourself to be confused if you are gullible enough to listen to warmizombies.

The 2nd LoT is pretty clear. Heat flows from warmer temperatures to cooler temperatures.

Warmizombies will try to confuse you by creating an overly convoluted scenario based around the phrase "net flow."

Anyway, if you are speaking to any actual scientist and you assert that heat is flowing from cooler temperatures to warmer temperatures then s/he will simply stop you right then and there, tell you that you are violating the 2nd LoT and won't bother wasting time discussing the matter with you until you are no longer violating the 2nd LoT. I guarantee that it won't help if you start hurling around a "net flow" this and a "net flow" that.

Scientists pretty much consider the laws of thermodynamics to be inviolate. If you see someone arguing "greenhouse effect" and Global Warming and "climate change" using the phrase "net flow" (or some variation thereof) then you will know that person is not an actual scientist.


.