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laser reflectors on the Moon

■    The Apollo 11 astronauts took a laser reflector to the Moon in 1969 —it is the only Apollo 11 experiment still working.

■    Two morę laser reflectors were placed on the Moon by Apollos 14 and 15.

■    The Apollo 15 laser reflector is three times the size of the other two.

■    The Russian Lunokhod 1 and 2 lunar landers also carried laser reflectors.

■    Lunar laser reflectors are used to measure the distance from Earth to the Moon and show that the Moon is moving away from Earth at the ratę of 1.5 in (3.8 cm) per year.

How to: use a laser to measure the distance to the Moon

01 ■ Ask an astronaut to take a reflector to the Moon for you.

Sin Fire a laser at the reflector—measure how long it takes for the light to bounce back from the reflector.

03

Using the formula speed x time = distance, calculate how far the light has traveled.

04,

Divide the distance by two, because the light traveled to the Moon and back again.

How are lasers used in medicine?

# Lasers are used in surgery to cut through flesh.

#The heat produced by a laser can vaporize living cells and seal leaking blood vessels.

#A laser can also change the shape of a cornea in the eye to correct nearsightedness or farsightedness.

#Medical lasers are sometimes used to remove warts.

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The world’s smallest laser

is only 144 billionths of a foot across. A linę of morę than 2,000 of them would fit across the width of a human hair.

WEIRD OR WHAT?

The musician Jean-Michel Jarre is famous for playing a laser harp in his concerts. Blocking each one of the instrumenfs laser beams with his hand produces a different musical notę.

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Have you seen a hologram today?

#lmagine a photograph that lets you see behind a subject in it.

#lt’s not magie—it's a 3-D picture called a hologram.

*A hologram is a special image created by a laser.

#A hologram is neither a picture nor a photograph.

«lt is a complex pattern that interferes with light to produce an image.

#Holograms are used on

credit cards, DVD cases, and Computer software packages.

*Holograms can also be found on some bank notes to show that the notę is genuine because they are difficult to fake.

01: The scientific principle of the laser was predicted by Albert Einstein in 1916.

02: The first working laser was built by Theodore Maiman in 1960.

03: The first item bought after being scanned by a laser bar codę scanner was a pack of chewing gum from a U.S. supermarket in June 1974.

04: The most powerful laser beams can cut through the toughest materials, even diamond.

05: At the National

Ignition Facility (NIF) in California, 192 laser beams are produced at the same time.

06: The NIF lasers are designed to be fired at a tiny pellet of fuel in a quest to produce energy by a process called nuclear fusion, the same process that po wers the Sun.