Facebook Physics: Heat Retention
Now here’s a question for you guys – I’m really impressed how interested you all are in Physics and Science in general. Well, we don’t want to take too much notice of Phd.s do we, as they are always quarrelling amongst themselves? Let us just keep to our own observations and avoid bigots like the plague.
Let’s take the Sahara. The Sun shines down and the radiation passes through the Oxygen and Nitrogen that makes up 99{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} of the atmosphere and encounters the surface of the Planet – in this case sand. We all know that radiation has to encounter mass to produce heat. So the sands get pretty hot. You can see David Attenborough in one of his films standing there and saying that the temperature of the sand was circa 70ºC and the air above it was 40ºC. Pretty damn hot, eh?
So the sand here was clearly heating the atmosphere from the bottom up. If we go up 5,000 feet we know that the temperature will only be 30ºC. How do we know that? Simple – Adiabatic Lapse Rate. We know that the temperature declines by 2ºC for every 1,000 feet of altitude. So the higher you go the colder it gets, as any aviator knows, or anyone who has climbed a mountain and reached the snowline.
Now here’s an interesting thing. The Sun goes down and within a few minutes the air is so cold that the Bedouin have to light fires and drink hot tea. Where the hell has all that heat gone?
Let’s take an example nearer home that everyone of you can verify for yourselves. When it is cold you switch the central heating on. You can get a real fug up in your living room. You go to bed say midnight and the central heating switches off. There is a nice frost overnight. When you go down to your living room, which was so cosy while you were watching TV, the room is quite chill. Where has all the heat gone? Especially when there was such a lot of Carbon Dioxide in the room from your breathing.
I don’t have to tell you guys about the three methods of heat exchange – radiation, conduction and convection. So we know that the heat is carried away upwards like on an escalator, called convection, which carries the heat away upwards towards Outer Space.
So where exactly does Global Warming come in? We know that all heat has to be generated – which is another way of stating the 1st law of Thermodynamics. We also know that all heat by itself always flows from hot to cold and never vice versa – 2nd law of Thermodynamics. So what the heck is this Global Warming? What is supposed to be warming? Is it the soil, the seas or the atmospheres?
Let us take a scenario. It is a cold Autumn day – the temperature outside at 5ft off the ground is only 10ºC. So we know then that at 5,000 feet it will be zero Centigrade. Pretty damn cold.
Let’s take a molecule of Carbon Dioxide up at that height. It is surrounded by 2,500 other molecules of Oxygen and Nitrogen. The molecules are not packed closely together, as they have grown farther and farther apart with altitude. The air has gotten thinner as they say, and more difficult to breathe. What is between the molecules? Any ideas?
Some infrared photon flies up from the Earth and hits this lonely molecule of Carbon Dioxide, which unlike the other gases is opaque. It absorbs the infrared and emits it in all directions including downwards within a nano-second. Now what happens? There are some eminent scientists, University Professors, who will tell you that this back-radiation warms the Lower Atmosphere below.
Wait a minute! What is this Lower Atmosphere? If it is 99{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} Nitrogen and Oxygen, that is impossible, as these gases are transparent to radiation. So the only possibility is that this so-called back radiation could only warm other Greenhouse Gas molecules. But again is that possible? The Convective gradient is flowing upwards and away to Outer Space, like a huge travellator. Can even a cluster of Carbon Dioxide molecules warm anything at all?
Forget the Professors; just use your own judgment. Now here is another thing, which is called the Inverse Square Law. Oh well! You guys are so much more learned than I am, I have to admit. I am sure you will advise me in a friendly way.
So here’s the enigma. If Carbon Dioxide cannot generate heat, we know also that in an open or even in a fairly closed atmosphere like a room it cannot retain heat, or trap heat, then we are only left with back-radiation. Now I ask you, could this back-radiation even warm a pebble on beach?
You tell me.
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