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Space Exploration Project

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Space Exploration Project Light-years ,Triangulation and Parallax By Fang Ming Zhang AU Astronomical units (AUs) , are used to measure distances in the solar system . – PowerPoint PPT presentation

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Title: Space Exploration Project


1
Space Exploration Project
  • Light-years ,Triangulation and
  • Parallax
  • By Fang Ming Zhang

2
AU
  • Astronomical units (AUs) , are used to
    measure distances in the solar system . The AU
    ,based on the distance between Earth and the Sun
    ,is equal to 150 million km.

3
Light-years
  • As the distances to most stars from Earth
    are in billions of AUs ,astronomers have devised
    a different unit to talk about the enormous
    distances outside our solar system .That unit is
    called a light-year .

4
  • A light-year is the distance that light ,
    which moves at 300 000 km/s ,travels in a year
    .It is equal to about 9.5 trillion km.

5
Techniques for Indirectly Measuring Distance
  • Telescopes cannot directly determine the
    distance to objects in space . It is also not
    possible to physically measure such long
    distances . For these reasons , two such
    techniques have been used for thousands of years
    to determine distances on Earth
  • Triangulation and parallax .

6
Triangulation

Imagine you are standing at the side of a lake
and can see a small island in the distance . If
you cannot reach the island , you have no way of
directly measuring how far it is from where you
are.The same problem confronts astronomers but on
a far greater scale.
7
  • Suppose point A is the position of Earth in
    January , point B is the position of Earth in
    June , point C is a nearby star . we need to
    measure the distance from point C to line AB .

8
  • There is a solution. We need measure angle
    1 and angle 2 . Then construct a scale drawing
    and draw a perpendicular line between baseline AB
    and C on the scale drawing . Measure the length
    of CD , and then calculate the actual distance
    according to the scale of the drawing. Then we
    will know how far the star C from AB is.

9
Parallax
  • Try this extend your arm and hold up
    your thumb . As you look with your left eye only
    , line your thumb up against an object on the far
    wall , such as light switch or the corner of
    window . Without moving your thumb , now look
    with your right eye only . The apparent shift of
    your thumb against the stationary background is
    called parallax .

10
The end
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