Download Space Exploration

Space Exploration
Have you ever looked up at the sky and wondered what was out there? If so, you are not alone.
Humans have been wondering this throughout history. Scientists have long been developing
technologies to help satisfy our curiosity.
What are some obstacles that prevent people from exploring space? How do different
technologies help us to overcome these obstacles?
The Telescope
Humans have wondered about space for thousands of years, but when did
the scientific exploration of space begin? One possible answer is 1610,
when an Italian scientist and inventor named Galileo Galilei looked at the
night sky through a telescope. Before Galileo, telescopes were useful for
seeing distances on Earth only. They were not powerful enough to give
scientists clear views of space.
Galileo’s telescope
allowed him to
observe objects
in space more
accurately.
Galileo improved the telescope. His version was nearly seven times more
powerful than older models. Galileo’s telescope allowed him to make
observations about the Moon, the Sun, and the structure of the solar
system. His measurements helped to demonstrate that the Sun is at the
center of the solar system. He also made other discoveries, including
several of Jupiter’s moons.
The invention of the telescope was a critical part of scientific history. However,
telescopes have limitations. What do you think some of these limitations are? After
you have thought about this question, read about some of these limitations on the
next page of this companion.
The modern
telescope is
a powerful,
yet limited
tool for
exploring
space.
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Space Exploration
When you are looking through a magnifying glass at an object nearby, you are seeing that object
as it is now. When scientists look at stars and other objects in space, they are looking back in time.
Though light travels very fast, it still takes some time to travel across the great distances of space.
Even light from the Sun takes about 8 minutes to reach Earth.
Scientists measure very long distances in space using a unit
called the light-year. A light-year is the distance light travels in
one year—about 9.5 trillion kilometers! After the Sun, the closest
star to Earth is called Proxima Centauri. This star is 4.2 light-years
from Earth. This means light from Proxima Centauri takes 4.2
years to reach Earth. Therefore, when scientists look at Proxima
Centauri, they are not observing it as it is now. They are observing
it as it looked 4.2 years ago.
Moving Beyond the Telescope
Telescopes have led to huge advancements in our understanding
of space. However, telescopes have limitations. For example, the
lens of a traditional telescope cannot be made too large or it will
bend. This limits how far into space we can see through
telescopes.
The Hubble Space Telescope
took this photograph of
the gases surrounding an
aging star.
Telescopes on Earth are also limited by interference from the
planet’s atmosphere and from manmade lights, which make
distant stars appear less bright. One way to avoid this light
pollution is to launch telescopes into space. For example, in
1990 scientists launched the Hubble Space Telescope, which
orbits Earth at a distance of about 550 km. The Hubble gives a
clear view of space without interference from Earth’s
atmosphere or light pollution.
The top photograph
shows a hurricane on
Earth’s surface. It was
taken by a satellite such
as the one shown in the
bottom image.
Scientists have also developed new technologies that allow
them to experience space in ways telescopes cannot reveal. For
example, humans have designed space suits, tools, and vehicles
that allow astronauts to travel safely into space. The
environmental conditions that exist high in Earth’s atmosphere—
and beyond—are dangerous to humans. Specialized equipment
allows astronauts to survive in space for days or even months at
a time. Let’s learn about some of these technologies.
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Space Exploration
Unmanned Space Vehicles
People had to overcome many challenges in order to create vehicles for space travel. One such
challenge is the difficulty of safely traveling through Earth’s atmosphere.
Humans could not survive on Earth without our planet’s thick atmosphere. However, it presents
several problems for space travel. Objects can produce a lot of friction as they collide with the
particles that make up the atmosphere. (You can get a sense of this friction if you ride in an openroofed car.) A vehicle used for space travel needs powerful rocket engines to overcome Earth’s
gravitational force. As these vehicles blast through Earth’s
atmosphere, they travel incredibly quickly. The friction they
produce creates a lot of heat. Scientists had to develop
heat shields for space vehicles to prevent them from burning
up as they move through Earth’s atmosphere.
Before developing vehicles that could transport humans into
space, scientists experimented with many unmanned
vehicles. Scientists continue to send vehicles without
humans—including satellites, probes, and rovers—into
space. Today there are many manmade satellites orbiting
This photograph of a sunset on
Earth. We use these satellites for many purposes, including
Mars was taken by a rover.
photographing Earth’s surface, communicating, and
navigating. (The Global Positioning System, or GPS, that
many people have in their cars and phones relies on data collected by satellites.) Scientists have
also sent numerous probes into the solar system. Some of these probes travel to and orbit other
planets. They send images and information about the solar system back to Earth. Scientists have
also sent robots called rovers to land on and explore the surfaces of the Moon and Mars.
Manned Space Vehicles
On April 12, 1961, a man was sent into space for the first
time. This man—a Soviet astronaut named Yuri Gagarin—
orbited Earth in a spacecraft called Vostok I. His flight
lasted 108 minutes. The United States was not far behind.
On May 5, 1961, Alan B. Shepard, Jr., became the first
American astronaut to visit space. His flight—in a
spacecraft called Freedom 7—lasted 15 minutes and 28
seconds.
Powerful rockets launch the
space shuttle off the ground.
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Space Exploration
Scientists continued to develop new and better technologies for manned space flight. In the United
States, the National Aeronautics and Space Administration (NASA) led the way. On July 20, 1969,
Americans Neil Armstrong and Buzz Aldrin became the first men to walk on the surface of the
Moon. Early astronauts were launched into space in tiny spacecrafts that broke apart as they
reentered the atmosphere. Eventually, the United States developed its first reusable spacecraft:
the space shuttle. First launched in 1981, the space shuttle made regular access to space
possible.
Technologies also exist that allow astronauts to survive
outside their spacecrafts. Special suits protect astronauts in
space from extreme temperatures and dangerous radiation
and supply them with oxygen. These technologies allow
astronauts to repair their spacecraft. They also made possible
the construction of the International Space Station, which
began in 1998. The first crew arrived in 2009.
The International Space Station is a facility where scientists
can perform research in space and test spacecrafts. It is
positioned as a satellite orbiting Earth. The first commercial
flights to the International Space Station began in 2012. It
may not be long before people all over the world have the
opportunity to visit space!
The International Space Station
floats in orbit hundreds of miles
above Earth.
Scientists in the Spotlight: Women in Space
Visiting space was not just a man’s dream. On June 16,
1963, Russian cosmonaut Valentina Tereshkova became
the first woman to travel into space. She orbited Earth in a
spacecraft called Vostok 6. The spacecraft orbited Earth 48
times in a period of 71 hours.
On June 18, 1983, Dr. Sally Ride became the first American
woman to travel into space. She traveled for several days
aboard a space shuttle called Challenger. During this
mission, she helped to launch satellites and worked on other
projects. Ride made a second voyage aboard the space
shuttle the following year.
Sally Ride was the first American
woman in space.
Dr. Sally Ride later became a professor of physics and director of the California Space Institute at
the University of California, San Diego. In 2001, she started a company called Sally Ride Science
to encourage young girls to pursue careers in science and mathematics.
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Space Exploration
Looking to the Future: Lunar Base
Astronauts have made long-term visits to the space station.
However, scientists continue to push for a more permanent base
on a moon or planet. Earth’s Moon is a possible site for such a
base. Astronauts could use a base on the Moon to store
resources, equipment, and other materials necessary for
missions into deeper space.
Another possible site for such a base is Mars. Using current
technologies, humans could travel from Earth to Mars in about 8
months. However, it is not currently possible to send all the
necessary resources to Mars. A spacecraft would not be able to
launch from Earth carrying all the materials needed by the
astronauts— the load would be too heavy. For humans to
survive on Mars long-term, we would need to figure out how to
extract oxygen, water, and food from resources already on Mars.
Mars—the “red planet”—may
have the resources needed
to support humans long-term.
First, however, scientists
are still trying to perfect the
technologies for traveling
there safely.
What do you know?
Many explorers have contributed to our understanding of space. Match each space explorer,
below, with the correct description of his or her accomplishments.
Names of Space Explorers
• 
Buzz Aldrin
• 
First American in space
• 
Neil Armstrong
• 
First American woman in space
• 
Yuri Gagarin
• 
First human in space
• 
Galileo Galilei
• 
First woman in space
• 
• 
Sally Ride
Alan B. Shepard, Jr.
• 
Improved the telescope for scientific
observations
• 
Valentina Tereshkova
• 
One of the first humans to walk on the
Moon
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Space Exploration
Exploring Lenses
If you have a telescope, your child can learn
a lot about space simply by observing the
same section of the sky at the same time
each night. Encourage your child to sketch
his or her observations and to note how the
stars and other space objects change their
positions over time. (To fully appreciate these
changes, your child should make
observations for several months at least.)
Your child can also observe the night sky
without a telescope, though if you live in a
suburban or urban area with light pollution,
you may not be able to see many stars.
Your child can also follow this procedure to
explore the process of magnification through
a simple lens.
5.  Examine the letters on the page through
the droplets of water.
Your child should notice how the water
droplets magnify the letters beneath them.
This is because the water droplets have a
convex shape: they curve outward, so they
are thicker in the middle than at their edges.
Convex lenses are frequently used to create
simple telescopes. Looking at an object
through these lenses causes the object to
appear larger.
Here are some questions to discuss with
your child:
• 
1.  Gather a cup of water, a roll of plastic
wrap, and a page from a newspaper or
magazine.
How is a water droplet similar to and
different from a simple telescope?
• 
2.  Tear off a piece of the plastic wrap that is
about the same size as the page.
What objects do you see in the night sky
every night? How do their positions in
space change over time?
• 
Are there any objects you can see only
occasionally? Why do you think this is?
3.  Lay the plastic wrap flat over the page.
4.  Dip your fingers in the cup of water and
sprinkle some large droplets of water onto
the plastic wrap.
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