A diagram showing the path of a planet around the Sun.
Click on image for full size
Kepler's 2nd Law: The Speeds of Planets
Kepler's second law he again discovered
by trial and error. Kepler realized that the line connecting the
planet and the Sun sweeps out equal area in equal time. Look at the
diagram to the left. What Kepler found is that it takes the same
amount of time for the blue planet to go from A to B as it does to go
from C to D. But the distance from C to D is much larger than that
from A to B. It has to be so that the green regions have the same
area. So the planet must be moving faster between C and D than it is
between A and B. This means that when planets are near the Sun in
their orbit, they move faster than when they are further away.
Kepler's work led him to one more important discovery about
the distances of planets.
Shop Windows to the Universe Science Store!
The Summer 2010 issue of The Earth Scientist
, available in our online store
, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.
You might also be interested in:
You may think that most objects in space that orbit something else move in circles, but that isn't the case. Although some objects follow circular orbits, most orbits are shaped more like "stretched...more
People from Asia crossed the Bering Strait into North America. These people were first in this new land and so they are known as Native Americans. Over time, these people broke into tribes (as seen on...more
"The movements of the heavenly bodies are an admirable thing, well known and manifest to all peoples. There are no people, no matter how barbaric and primitive, that do not raise up their eyes, take note,...more
The stones of Carnac, France, are probably the most famous stones markings outside of those found at Stonehenge in England. There are many, many stones at Carnac. And these stones are very old too, the...more
Not too far from Loch Ness, there lies three giant tombs made of stones. They are called the Balnuaran of Clava. The Balnuaran of Clava, giant tombs encased in stone, can be found close to Inverness in...more
Cuzco is located in Southern Peru. It is the ancient capital of the Inca Empire. It is the oldest, continuously occupied city in the Americas. In ancient times, Cuzco was the ceremonial capital and hub...more
The stone structures of England and France are very famous. In Italy, you'll also find standing stones, stone rings, and stone tombs. An example of these stone structures is in Fossa, Abruzzo, in Italy....more