Download Getting to Know: Evidence for the Big Bang Theory

Getting to Know: Evidence for
the Big Bang Theory
The next time you’re outside on a clear night, look up at the night sky. How many stars can you see? What do you think is beyond the stars? How old do you think the universe is, and how did it begin? Scientists have long been fascinated with the universe and its origin. We know more today than we did hundreds of years ago, but we’re still learning more and more about distant stars and galaxies. In this concept, you’ll explore the most widely accepted theory among scientists of the origin of the universe: the Big Bang Theory. As you study this concept, remember that the universe is huge. It’s made of billions of galaxies, and each of those galaxies is made of billions of stars. It’s almost hard to imagine the immense size of the universe. Images from space have been used as
evidence to support the Big Bang Theory.
What is the Big Bang Theory?
Although challenged by such theories as the Steady State Theory, the Big Bang Theory
continues to be the most widely accepted theory of the universe’s origin among scientists.
It states that the universe formed approximately 10 to 20 billion years ago when a single
point in space began to expand rapidly. This rapid inflation was probably a massive explosion
(hence the name Big Bang Theory).
Misconception 1: I heard that the Big Bang Theory is just an idea and that there is
no evidence to support it. Is that correct?
No, it’s not correct that there’s no evidence to support the Big Bang Theory. In fact,
you’re about to read about three key types of evidence that scientists use to support it:
spectrum analysis, studies of galaxy and star movement, and background radiation.
What evidence do scientists use to support the Big Bang Theory?
There is evidence to support the Big Bang Theory, but keep in mind that humans weren’t around to witness this explosion. The evidence scientists use to support the theory comes from data and observations about the universe today. One type of evidence that has been used to support the Big Bang Theory is spectrum analysis.
Spectrum analysis involves studying the wavelengths of light in the universe. We can study
the wavelength of light from distant stars and galaxies to draw conclusions about their
movement. For example, if objects are moving toward us, the light that they emit is shifted
toward the blue end of the spectrum. If objects are moving away from us, the light that they
emit is shifted toward the red end of the spectrum. So, if the light emitted by most stars and
galaxies in the universe is shifted to the blue end of the spectrum, it means that most stars
and galaxies are moving closer together. A red shift means that most stars and galaxies are
Concept: Evidence for the Big Bang Theory
Getting to Know
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moving away from each other. Analysis of stars and galaxies shows an average red shift, which
means that most stars and galaxies are moving away from each other. This evidence suggests
that the universe is expanding.
Other evidence also suggests that the universe is expanding. The Hubble Space Telescope provides us with images of the distant universe. Using calculations of star and galaxy movement, scientists have shown that most objects in the universe are moving away from each other. Finally, the discovery of microwave radiation coming from distant places in the universe also has been used to support the Big Bang Theory. Many scientists think that this microwave radiation is left over from the Big Bang. Which scientists helped develop the Big Bang Theory?
A scientist named Edwin Hubble deserves much of the credit for developing the Big Bang Theory. Hubble made detailed observations about distant galaxies and realized that the farther away a galaxy is, the faster it is moving. This helped him conclude that all matter in the universe started in the same location and expanded from that point. This idea became the Big Bang Theory. Perhaps you’ve heard the name Hubble before; his name is now attached to a famous telescope, the Hubble Space Telescope. It takes amazing images of distant galaxies and has helped us learn a lot about the structure of the universe. The Hubble Space telescope was built by NASA and named in Edwin Hubble’s honor. It was launched into space in 1990, many years after Edwin Hubble died.
Edwin Hubble may be one of the most famous scientists to explain the Big Bang Theory, but many other scientists have built on his work, collecting more evidence to support the theory. Often, one piece of evidence helps create as many questions as
it answers. For example, what existed before the Big
Bang? That means that scientists will be studying the
origin of the universe for a long, long time.
The Hubble Space telescope pro­
vides us with images of distant stars
and galaxies.
Misconception 2: If the universe is expanding, does that mean that stars and
galaxies are moving through empty space?
As the universe expands, the space between stars and galaxies increases. Galaxies and
stars are similar to nuts or raisins in a baking loaf of bread. As a loaf of bread bakes,
it expands, and the nuts and raisins move apart from each other. In the same way,
the expanding universe causes most objects in the universe to move apart from one
another. Stars and galaxies are not moving through empty space because the spaces
between them are also part of the universe.
Concept: Evidence for the Big Bang Theory
Getting to Know
www.discoveryeducation.com
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.