- One wise can teach many fools something of interest, because the fools cannot avoid absorbing the message because they are without defense. Even if the message is not understood in detail, it will have an effect as elevation of general knowledge/temperature. Education is meaningful, to some degree in some sense.
- Fools, even many, cannot teach a wise anything of interest, because the wise will simply not listen, because of an inability to absorb trivialities: We know that intelligent FRSs proudly claim that they cannot learn anything from the blogosphere.
- In successful education, the student may over time become as knowledgeable as the teacher, but not more...as the student learns the teacher gets less and less to teach...
onsdag 28 juli 2010
The Wise and the Fools of Backradiation
Roy Spencer feels an urge to make a follow-up to his "controversial post on the effect of infrared "backradiation", the existence some dispute" by suggesting a "simple and inexpensive Experiment to Investigate Infrared Sky Radiation Effect on Temperature Changes".
This is simply the standard blackbody in the form of a box (cavity) with a hole absorbing and emitting radiation to the surrounding. The air in the box is initially at 300 K and the surrounding is kept at 290 K. Spencer asks for the temperature in the box after some time.
The answer is of course 290 K. But this is not because of any form of "backradiation", but because the cavity reads the temperature of the surrounding from its spectrum, and then decides to cool or warm depending on its own temperature. As illustrated in the model studied in Computational Blackbody Radiation, now updated with a section giving evidence that backradition is non-physical.
The key feature of this model is that the form of a blackbody spectrum is determined by
the temperature which sets the cut-off according to Wien's Displacement Law. The result is
that a warmer body can heat a colder body, because the colder body can absorb high-frequency radiation and grind it to heat. But a warmer body cannot get heated by absorbing low-frequency radiation from a colder body, because the required high frequency input is missing and cannot be created out of nothing.
Two blackbodies of equal temperature do not exchange heat energy, because the reason to do so is lacking (according to Leibniz' Principle of Sufficient Reason).
We may compare to the following familiar situation: