# Space Exploration Project - PowerPoint PPT Presentation

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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