What are calories?
To most people, calories are usually associated with a very large piece of chocolate
cake. But in that case, they are called nutritionist’s calories, or the unit of energy-pro-
ducing potential equal to the amount of heat that is contained in food and released
upon oxidation by the body. The body needs the calories in the foods we eat to use as
energy. This is why nutrition and weight-control texts often contain such entries as “a
140 pound person walking for one hour at a moderate pace burns off 222 calories.”
In chemistry, a calorie also refers to a unit of energy. But in terms of chemical
experiments, a calorie is the amount of heat required to raise the temperature of 1
gram of water by 1 degree Celsius from a standard initial temperature at a pressure of
1 atmosphere (sea level). The unit measurement for energy is a joule, in which 1 calo-
rie equals 4.184 joules; 1 joule is translated (most often in metric) as the energy need-
ed to lift 2,000 grams a distance of 10 centimeters.
ASTRONOMY AND MATH
What are astronomyand astrophysics?
Astronomy is the study of matter in outer
space. It is usually considered a branch of
physics. But because it encompasses (lit-
erally) an astronomical number of sub-
jects—everything from the study of a
star’s surface to the end of the universe—
it is often considered a field of its own.
Astrophysics is a branch of astronomy
dealing with the physics of celestial bod-
ies and the universe as a whole. It deals
with problems that range from the struc-
ture, distribution, evolution, and interac-
tion of stars and galaxies to the orbital
mechanics of a near-Earth asteroid.
Who was Hipparchus?
Hipparchus of Rhodes (also seen as Hip-
parchus of Nicaea, as he was born there;
c. 190–c. 120 BCE) was one of the greatest
Greek astronomers. A partial list of his
discoveries includes: being the first to
discover the precession of the equinoxes, 287
MATH IN THE PHYSICAL SCIENCES
The famous astronomer Nicholaus Copernicus (pic-
tured here) is commonly thought of as the first per-
son to propose a heliocentric (Sun-centered) model
of the solar system, but actually Aristarchus sur-
mised the truth centuries before him. Library of
Congress.