Geology is the study of the Earth, and many features and processes that we see on Earth occur on other planets as well. Our geology section provides extensive information about minerals, rocks and the rock cycle, Earth's layers and moving plates, fossils and Earth history, as well as information about careers in geoscience. Our Teacher Resources section includes numerous classroom activities on topics in Geology and Geography for you to try in your classrooms. This content is related to understandings highlighted in the National Science Standards (particularly Structure of the Earth System and Earth's History). Enjoy your geologic explorations on Windows to the Universe!
Earth at Perihelion
As I mentioned in last month's newsletter, students often mistakenly believe that the seasons are caused by variations in Earth's distance from the Sun. Earth's axial tilt is, of course, the real reason for our seasons. The Earth does, however, travel around the Sun in an elliptical orbit which brings it closer to and further away from our neighborhood celestial furnace during the course of each year. Astronomers call the point of closest approach "perihelion", and the most distant point "aphelion". These words come from Greek roots: "helios" is Sun, "peri" means near, and "apo" means away from.
Earth passes through perihelion in early January each year (on the 4th in 2006), so it is closest to the Sun in the depths of the Northern Hemisphere's winter. Earth is about 3% further from the Sun at aphelion (in early July) than at perihelion. Earth's orbit is very nearly circular, so its aphelion and perihelion distances are not much different from one another. Some planets have orbits which are much more elongated; astronomers say such orbits have a large "eccentricity". Pluto, for instance, is about 66% further from the Sun at aphelion than it is at perihelion.
Check out these pages on Windows to the Universe to learn more about elliptical orbits, perihelion & aphelion, and eccentricity:
These topics are relevant to "Content Standard D: Earth and Space Science" in the National Science Education Standards (Grades K-4: Objects in the Sky & Changes in Earth and Sky; Grades 5-8: Earth in the solar system).
You may not know that we have a fundamental physics section on the Windows to the Universe site. It really provides many supporting links for so many other sections of the site, and for so many areas you teach!
These pages and more include great graphics for you to share with your students.
Covering these topics hits National Science Content Standards in Physical Science - specifically motions and forces (at all levels).
For an in-depth look at the process of biological evolution and examples of evolution check out our new Evidence of Evolution Exploratour! This sequence of 11 pages provides a tutorial appropriate for middle and high school level students that includes topics such as microevolution, natural selection, dog breeds and artificial selection, and the evolution of bacteria.
The position of the planets affects their size and composition. Most planets are tilted, like Earth, so most planets have seasons, too. The four innermost planets in the Solar System (Mercury, Venus, Earth, and Mars) are all similar to Earth - they have solid bodies with compact, rocky surfaces. However, the four giant planets (Jupiter, Saturn, Uranus, and Neptune) are known as gas giants because they are comprised mostly of a thick outer layer of molecular hydrogen and helium gas. Each has a solid or liquid core made of rock, ice, or highly pressurized fluids such as liquid metallic hydrogen, deep beneath its dense atmosphere. These giant planets are also known as "Jovian" planets ("Jove" is a Latin variant of Jupiter) because Saturn, Uranus, and Neptune are much more like Jupiter than they are like Earth. Letīs find out more about these GIANTS: Jupiter, Saturn, Uranus, and Neptune!
There is also the 9th planet, Pluto, which is the farthest planet from the Sun and also the smallest. Pluto, which is a bit of an oddball, is even smaller than seven of the solar system's moons. Lets find out more about little PLUTO too!
In the last few years, numerous minor planets (sometimes called Plutinos!) have been found in orbits similar to Pluto's. Recently, an object that may actually be larger than Pluto was discovered, and some astronomers have dubbed it "the 10th planet". We'll have more on the "is Pluto a planet" debate in next month's newsletter.
Happy New Year and thank you for helping to make Windows to the Universe so popular in 2005! We had a record number of visits (user sessions) last year - over 11 million, including more that 2.8 million visits to the Spanish language pages on the site! Our users came from 210 countries. Click here to see these statistics in detail.
We now have almost 1,400 educators receiving this newsletter in 71 countries all around the globe. Thank you for your interest and please keep letting us know how we can serve you better.
Space Science Problem of the Week
Our colleagues at the NASA IMAGE mission (that is dedicated to imaging the Earth's magnetosphere) produce problems for teachers to use in their classrooms to help students learn about topics in space science. The Weekly Problem Archive for Year 2 of the project provides links to the most popular 20 problems for the 2004-2005 school year, as well as links to the first year archive as well.
Other Opportunities for Teachers!
The Seventh International Conference on School and Popular Meteorological and Oceanographic Education (EWOC 2006) will be hosted by the University Corporation for Atmospheric Research and co-sponsored by the American Meteorological Society, the Australian Meteorological and Oceanographic Society, the European Meteorological Society, the Royal Meteorological Society, the World Meteorological Organization and other meteorological and oceanographic societies from around the globe. Find out more about this opportunity at the AMS web site.
If you want to submit an abstract, the deadline is February 15, 2006.