Cold - below 60 F Comfortable - between 72 F and 76 F
In
1593, Galileo Galilei invented a rudimentary water thermoscope, which
is now known as the Galileo Thermometer. For the first time, the temperature
variations could be measured.
“If an object is denser
than a liquid, it will sink in that liquid. If an object is less dense
than the liquid, it will float in that liquid. Such an object will partially
sink until the weight of the liquid it displaces becomes equal to the weight of
the object. This means that some of the object will protrude above the liquid
surface.
Hot - above 84 F
Comfortable - between 68 F and 72 F
Cold - below 60 F
The clear liquid inside the Galileo thermometer is not water, but is another
liquid, typically ethanol, whose density varies with temperature more than the
density of water does. This makes it more sensitive to temperature changes
which makes it a better predictor for temperature than water. As the
temperature of the surroundings changes, the temperature of the thermometer and
liquid inside changes in order to match this temperature. This affects the
density of the liquid, which then causes some bulbs to rise and some to sink to
the bottom. The bulbs that rise are less dense than the liquid, and the ones
that sink are more dense than the liquid.
The bulbs are sized so as not to jam with each other as they move up or down in
the tube. They are either at least half the size of the inner tube diameter, in
order to maintain their stacking order, or their size is much less than the
inner tube diameter, in order to allow them to freely pass each other as they
move up or down.
In some thermometers, if there are some bulbs at the top of the tube, some at
the bottom, and one floating in the gap, the one floating in the gap tells the
temperature. If there is no bulb in the gap then the average of the values of
the top and bottom bulbs gives the approximate temperature. In other
thermometers, the lowest floating bulb gives the approximate temperature.”
Abstract
comes form Real World Physics Problem
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