Meaning of Temperature

Temperature measures the degree of hotness or coolness of a body -- the hotter a body, the higher its temperature -- and it is precisely this quantity that fixes the direction in which heat will spontaneously flow whenever two bodies are placed in thermal contact. The SI unit of temperature is the kelvin (K), while Celsius (°C) and Fahrenheit (°F) are the everyday scales; temperature itself is always read off using a thermometer, which is simply an instrument brought into thermal contact with an object until it reaches the same temperature as the object (see Table 8.1 for the complete set of conversions between all three scales). A subtlety worth noting: our skin does not directly sense an object's actual temperature -- it senses the rate at which heat is conducted into or away from it, which is why a tiled floor feels …