this down in here and dividing the cylinder to two parts the now the clay is the flame will burn on as long as you leave that cardboard in because what has happened is the warm air started up and it started up one side first and then started a convection current up here and cold air came down the other side well how do you know it goes down the side and up the side well i don't hurl but if i put my finger over there and try both sides it gets warm here so i know the warm air is coming up the side not in the cold air is going down there well to test that if  the same thing as before oh let's go back over here and look at this boiling water come you have here in the paper cup you see what's happening oh she's still boiling merrily away can we dump that the end to him to keep from burning myself here gotten up sometimes in the morning and seen the sun come up over there rising on the other morning and just as soon as a see the light you feel the heat from the sun as it shows that from the sun he's traveled with the same speed of light and that's one hundred eighty six thousand miles a second so when i said radiation is fast i meant fast it travels with this enormous speed this that you have over here then is a measuring device yes this is a thermal pilar oh here's a little metal horn or reflectors and on the back of the corners are a lot of little wires and these wires are arranged so that when heat falls on them they develop an electric current tiny lector current and that current through these wires goes to a meter here which we object on the screen oh yes and you see the pointer this meter here it moves on i turn this on its it's a detector of heat and i pointed at the floor you see it shows in the center reading a reading of zero yes now if i pointed toward your face  the thing that's warm is indicated by the movement of the pointer and that's certainly a very accurate method of measuring heat coming back to something that we've known for many years a heating device radiant heat the old fashioned fireplace of course now the bottom areas they were the fire would be and then we have a chimney that comes up here the important thing about the fireplace is again convection currents most of the he comes up here and by radiant heat or reflected heat we get the heat coming out in the room by travelling and when they hit your face they're absorption hit your body and change into heat so what we have then in our fireplace at home is very much the same sort of thing and we saw demonstrated in this experiment a little bit before in other words convection currents going up the tube and as without the convection currents of course you wouldn't be able to have a fire in the fireplace any more than this flame would be able to stay there for just like seconds lol there's one other type of heating that we haven't mentioned yet and that's a panel heating it's a newer thing that's just come in and or an engine there's a very very satisfactory and economical not just how does this work very well in the panel here oh you have a similar principal fireplace you have a large area that's warm like the brick walls only here you warm the floors of the ceiling or sometimes the walls by by hoch water in pipes sort warms up the whole floor area the ceiling area and the warmer areas radiate heat towards the people the occupants of the room if you even though the room may be quite cold this radiant heat when it hits your face hit your body it's absorbed and becomes heat and you feel quite comfortable it was final experiments you have over here this is a gear that you have is certainly very interesting those big reflectors and just what is all of this gear now can you give us an idea of as all this works it's horrible here we have a large metal reflector the kind you have in a searchlight and at the focus of this search like mir we have one of these thermal files no way over across the room and way down the other end of the laboratory about thirty or forty feet down there is not ye you'll find another mirror down there is just like the one we have here and bob bell has a candle flame ready to put in this mirror now when he puts the candle flame at the center focus of the smear it acts like a searchlight it reflects the heat raises well as the light we have a beam of heat rays and light coming across to this one here they are again reflected and come into the thermal pile whereas now we'll see it on the galvanometer that will see it on a little pointer of the galvanometer as it moves now bob if you'll put the candle flame in sort of a fraction on this meter well earlier we could put that candle flame one hundred feet a mile two miles five miles even fifty miles of labels a clear day and we could pick up the heat from it and bring it over here and receive it as a matter of fact term a pilot to detect the heat radiation from start believe it or not millions of miles away and then then they mount equipment something like this in their telescopes and are then able to get a to get a reading yes they reflect the light are through their star a little thermal tiles and record the current from it and measure their heat ready by a star millions of miles away or less is certainly one of the most accurate pieces of measuring equipment that i've ever seen and looking back over these demonstrations that you brought to the laboratory it seems to me that a boils down again to the three basic issues first of all conduction secondly convection and third radiation and no matter where we turn in our everyday lives we're going to come up against these factors that have to do with heat that's right well i want to thank you again for coming through on science and action to bring these wonderful experiments and i see your system bob bell is still wrestling with amir down there thanks also to bob for helping with the demonstrations been a pleasure  are the two types and main difference is in the size of the front feet what is the size of this big foot this is eastern goal for the smaller size of the foot of the western gopher principle of differences between the eastern and western