28. Put two thick dots on a piece of paper at a distance of 10cm. Close your left eye, always look at the left dot, and get slowly closer to the piece of paper. You will still recognize the right dot (do not look directly at it, still look at the left dot!) At a distance of about 25cm the right dot will disappear. Why? There is a 4mm^2 area on the retina where no detector cells are located. this is the place where all nerve strands get collected and leave the eye ball to the brain.
29. What will you see if the eye balls are strictly frozen? Nothing. Seeing is due to detector cells on the retina sending pulses. they only send pulses when light intensity CHANGES. Therefore even in morla conditions, the eye ball is making microscopic oscillations with about 100Hz.
30. Normally we take a breath every 4-5 seconds. Take 6-8 deep breaths. After that you will realize that for about 30 seconds you do not need to breathe. Why? Because we reduce the level of CO2 - and not because we also increase the level of oxygen.
31. Is the nerve signal which causes us to breathe induced by varying conentration of oxygen, or CO2? CO2.
32. What will happen if we get pure oxygen atmosphere? We will die because of too much CO2 in the blood. Additional oxygen is dissolved in the body, and blocks the backtransportation of CO2. Therefore we slowly die because of intoxication, but feel that we can not get air - since too much CO2 sends signals to the brain that we need more air - too bad since what we get is pure oxygen, and that makes thigns even worse.
33. Why can we save a person with mouth-to-mouth breathing? Isn't our air full of CO2? Because there is always a rest of air in the lungs, which has CO2 and oxygen concentrations somewhere between fresh and used air. When we breathe in, we push this air and the oxygen in this air into the lungs and the blood. In addition we press on the body, in order to reduce the lung volume, and let it expand again, so that fresh air gets in.
34. How old can a humang egg (cell) get? As old as the woman. Egg cells are ready (about 400 thousand) with the birth of a girl. They slowly grow and about 400 of them get mature. Only very few of these finally end up in a new child.
35. S=\sum_{n=1}^{N} a(n) . P = \prod_{n=1}^N a(n) . Find N,{a(n)} such that P is maximized at fixed S. Answer: N=S/e , a(n)=e !!!
36. put twop equal size triangles with 100 meters size on top of each other. This makes 6 houses. But the house 7 at a distance 100 meters from two edges of both triangles. Now rotate one of the triangles around the house number 7 until the most distant 9from house 7) edges also have distance 100 meters. That's it.