According to the facts of physics, if temperature increases, thermal expansion of an object is positive it will expand and with decrease of temperature it will shrink. Pressure will increase due to increase of temperature. On the contrary, during fever we can see blood vessels and skin are shrunk, pressure decreases, body shivers, sleep increases, motion decreases, inflammation increases, body pain increases, blood circulation decreases, dislike cold substances etc... In fever, the firing rate of Warm sensitive neurons decreases, and the firing rate of Cold sensitive neurons increases. At the same time if we apply hotness from outside by thermal bag or if we drink hot water, our body acts according to the Facts of Physics- increase of temperature pressure will also increase, expands blood vessels and skin, body sweats, motion will increase , inflammation will decrease , body pain will decrease, blood circulation will increase, like cold substances etc.. During fever, why our body acts against Facts of Physics? when disease increases, pressure and temperature will decrease. Blood circulation will decrease due to decrease of pressure. If the essential temperature of the body is going out, essential temperature and pressure will further decrease. This will further endanger the life or action of organ. when disease increase, it is the sensible and discreet action of brain that tends to act against facts of physics to sustain life or protect organ .There is no way other than this for a sensible and discreet brain to protect the life or organ. We will get a clear answer if we find out the purpose of fever, sensible and discreet action of brain . No medical books clarify this During fever, if the temperature of fever is not a surplus temperature or if it is not suppose to be eliminated from the body, the shrinking of skin and blood vessels, shivering of body, dislike towards cold substances etc are a protective covering of the body to increase blood circulation to important organs of the body it is against the facts of physics.