How does a vacuum bottle keep things cold?
The word vacuum is coined froze a latin word meaning empty. But the astrophysicists suspect that there is no such thing as totally empty space in the entire uriiverse. There are a few specks of matter in the most deserted regioris of space. And science has failed to produce a perfect vacuum. When we speak of a vacuum, we mean a space empty even of air. But since we cannot rmove all the m01ecuies of gas from a container, we can create only a partial vacuum. You might suppose that an empty space can do nothing at all. But like everything else, a vacuum has its own qualities. It is a barrier to light and sound. In a vacuum bottle, all but about a thousandth part of the air has been removed. This partial vacuum can keep things cold or hot for about 24 hours. A vacuum bottle is made to slow down the transfer of heat from the inside to the outside of the flask. And heat is transferred by three methods. A moving gas or liquid carries and spreads its heat from place to place by convection. The
