Light Year How far is far How fast is fast What Is It A light year is the DISTANCE that light will travel through a vacuum in one year Calculate Seconds How many seconds are in a year ID: 746457
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Slide1
CSCOPE
Grade 8 Unit 10Slide2
What type of measuring unit would we need for distances across space?
Slide3
Light Year
How far is far?
How fast is fast?Slide4
What Is It?
A light year is the
DISTANCE that light
will travel, through a
vacuum, in
one
year.Slide5
Calculate Seconds
How many seconds are in a year?
31,557,600 s/
yr
60 s
60 min
24
hr365.25 days1 min1 hr1 day1 yr
Slide6
What is the fastest speed we know?
The Speed of LightSlide7
Speed of Light
c
= 299,792,458 meters
per second
or
186,000
miles per secondSlide8
Speed of Light
To get an idea of how fast this
is. . .
light can travel about seven times around Earth in one second!Slide9
Other Values
One
light year is
approximately 5.880
trillion
miles or 9.5 trillion km.
The s
ymbol for light year is “ly”.Slide10
Why “ly”?
Light years are used to
measure the vast distances
in space.
In the universe, the kilometer measure is too small to use. Slide11
History Seen
Every time you look at
objects in the night sky or
the Sun, the light from
that object is old. You are looking at history.Slide12
An Example
It takes
eight
light minutes for light leaving the Sun to reach the Earth
.
To put this in perspective, if you could drive from the surface of the Sun to the surface of the Earth, it would take you 180 years driving nonstop at 60 mph.Slide13
Example: Sirius
Sirius,
in the constellation
Canis
Major, is
the sky’s brightest star. It is easy to find on winter and spring evenings.When you look at Sirius, you are looking back in time to see how
Sirius looked eight years ago. The light left the star eight years ago.