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In our Solar System, we see light from our sun reflected off the planets. In more distant galaxies, light from many millions of stars takes a long time to reach the Earth. It takes light 4 years to reach the Earth from Sirius, a near neighbouring star. Using the Hubble telescope, we can see the light from the Eagle Nebula, which takes 7,000 years to reach the Earth.
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First broadcast:
17 May 2007

Classroom Ideas

Provide a list of various planets and stars (not mentioned in the clip) and in pairs, students could calculate the light years between them and Earth. Discuss with students the concept that everything we see involves looking back in time, with light we see from further stars having originated longer ago. Relate this to delays in satellite transmissions.

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