What is actually happening when someone takes a temperature?

A person has a fever if their body temperature rises above the normal range of 98–100°F (36–37°C). It is a common sign of an infection. As a person's body temperature increases, they may feel cold until it levels off and stops rising. People describe this as “chills.”

Explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.