n In the following example, the numbers give how many times larger (x) the current object is compared to the previous object.
|
Current Object |
Time Larger Than Previous Object |
||
|
Atomnote 1 |
|
||
|
Human Cells |
100,000 x |
||
|
Human Body |
100,000 x |
||
|
Earth |
10 million x |
||
|
Solar System |
10 million x |
||
|
Milky Way Galaxy |
10 million x |
||
|
Observable Universenote 2 |
100,000 x |
Note 1: about 0.00000001 (1 x 10-8) cm
Note 2: about 15,000,000,000 (1.5 x 1010) light years
n Note that the scale from atoms to the entire universe is a factor of about 1,000,000,000,000,000,000,000,000,000,000,000,000
a one with 36 zeros after it or 1x1036
http://www.youtube.com/watch?v=9wd0i44vK04
 |
A solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially obscured. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth, with between zero and two of them being total eclipses. Total solar eclipses are nevertheless rare at any location because during each eclipse totality exists only along a narrow corridor in the relatively tiny area of the Moon's umbra. A total solar eclipse is a spectacular natural phenomenon and many people travel to remote locations to observe one. The 1999 total eclipse in Europe helped to increase public awareness of the phenomenon, as illustrated by the number of journeys made specifically to witness the 2005 annular eclipse and the 2006 total eclipse. The most recent solar eclipse occurred on January 26, 2009, and was an annular eclipse. In ancient times, and in some cultures today, solar eclipses have been attributed to supernatural causes. Total solar eclipses can be frightening for people who are unaware of their astronomical explanation, as the Sun seems to disappear in the middle of the day and the sky darkens in a matter of minutes. |
"Triangulation" using parallax has been used for centuries to find distances.
It can be used up to about 100 light years to estimate distance for stars; beyond that, the angles are too small.
Measurements are enhanced with a larger baseline. This baseline can be the diameter of the earth or the diameter of the plane of the Earth's orbit around the Sun.
This video demonstrates Trigonometic Parallax.
The top half of each frame shows the appearance of the sky as seen from the Earth (ignoring the Sun), and the bottom half shows a fixed view looking down from above onto the plane of the Earth's orbit around the Sun (the ecliptic). A red star is shown located some distance to the right (also in the ecliptic plane). In this simulation, the star is fixed in space with respect to the Sun, and its proximity to the Sun is greatly exaggerated to help make its parallax easy to see.
In the first half of the movie, the parallax motion of the red star over the course of one year is shown. Note that the star is not moving through space, as can be seen in the bottom panel, only the Earth is moving. The star's parallax motion is simply a reflection of the Earth's orbital motion. When viewed from the moving Earth (top panel), the red star appears to move first west (towards the right) then east (towards the left) with respect to the distant background stars which are so far away that their parallax motions are too small to be seen at this scale.
In the second half, we move the star 2x farther away (as indicated by the scale bar at the bottom) and run through another year. Now the annual the trigonometric parallax motions are 2x smaller because the distance to the star is 2x greater. This fact, that the trigonometric parallax of a star is inversely proportional to its distance from the Sun gives us a direct measurement of the star's distance.
Note that the parallax motion of the star is an illusion due to the orbital motion of the Earth around the Sun. Real stars are much more distant than shown here (the nearest stars, the Alpha Centauri triple star system, is about 150,000 AU away, resulting in a maximum parallax amplitude of about 1.3 arcseconds).