Page 50 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

What’s inside a Inside a modern

planetarium
planetarium? How several projectors
work together to create
one seamless image

The incredible theatres where you can explore Seamless
screen
the night sky and beyond The perforated
aluminium
ou no longer need to train for several years represent views from different points on the panels are very
thin, making the
as an astronaut to explore space, as Earth’s surface too. Traditional planetariums use joins almost
Yplanetariums can give you an amazing mechanical star ball projectors, but they are invisible.
virtual tour of the universe while you keep your limited to showing the stars and planets that can

feet firmly on the ground. Instead of a big cinema be seen from Earth.
screen at the front of the room, images are The most modern planetariums now use digital
projected onto a domed ceiling to create a more projectors hooked up to computers instead, and
immersive experience. can project any image onto the dome to show No echoes
The screen panels
“There’s no edge to the screen so it’s like you’re incredible views from anywhere in the universe. are made from
actually there,” says Jenny Shipway, Head of the Combining data from space agencies, spacecraft aluminium
Winchester Planetarium in the UK. “During a show and telescopes all over the world, realistic perforated with
you shouldn’t be aware of the dome at all, the graphical representations of entire galaxies can be tiny holes to let
sound pass
dome should be invisible so your brain can projected onto the dome. through, instead
imagine you are actually in this three-dimensional “We use software called Uniview and it has a of bouncing
virtual universe.” virtual model of the known universe in it”, says around the dome.

Early planetariums simply had paintings of the Shipway. “We use it as a flight simulator. It’s
night sky on the inside of the dome to give people a literally like playing a computer game; just using a
clear view of all the constellations. However, when computer mouse you can fly anywhere. You can do

projectors were developed they could depict a seamless zoom all the way out from Earth right to

moving celestial objects as well as fixed stars, and the edge of the visible universe.”

A star ball projector
can only show the view
from one hemisphere

Anti-reflective
The screen is painted
grey to reduce refl ections
Star-ball projectors from the bright lights of
the projectors.
Some planetariums still use traditional However, many projectors feature two star balls
analogue projectors known as star balls. These attached together in a dumbbell-shaped
metal spheres sit in the middle of the audience structure so that they can represent the view
and have a bright electric lamp inside that from anywhere on Earth. Additional moving Mechanical curtains
shines light through several small lenses projectors can also be attached to show moons, Each projector only shows a
surrounding it. The lenses are used to represent planets and other moving celestial objects. The section of each frame, using
stars, focusing light onto the planetarium dome main limitation of star-ball projectors is that mechanical curtains to block
out the rest.
to recreate the night sky as it can be seen from they can only show the view from Earth, while

Earth. Single star balls are often fixed at one end digital planetariums let you explore the far
so can only show the view from one hemisphere. reaches of the universe too.

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How It Works
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