Aim: How do scientists explain the development of life on earth?
What Evidence Do Scientists Use to Explain the Nature and Origin … · 2018-08-23 · Explore What...
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Understanding the Universe | Explore What Evidence Do Scientists Use to Explain the Nature and Origin of the Universe? The Origins of the Universe Scientists estimate that the universe is about 13.7 billion years old. This is much older than Earth. Earth is approximately 4.6 billion years old. The universe is also much older than the solar system to which Earth belongs. Scientists cannot make direct observations of most astronomical objects. Instead, they must study the light from these distant objects to gain an understanding about them. Scientists then can use this information from the objects’ light to better understand the origin of the universe. Advances in technology over the last century have allowed astronomers to make observations of fainter and more distant objects across the entire electromagnetic spectrum. These observations have yielded evidence about the origin of the universe. With this evidence, scientists developed a theory to explain the initial formation of the universe. Scientific theories are ways of explaining why things happen in the natural world. They begin with a hypothesis, or an idea of how scientists think something works. Scientists then collect data to test the hypotheses. Scientific theories are thought to be correct until new information suggests alternative theories. Scientists always check theories by collecting more observations and by experimenting. Sometimes, new observations cause a theory to be reshaped or modified to match
Transcript of What Evidence Do Scientists Use to Explain the Nature and Origin … · 2018-08-23 · Explore What...
Understanding the Universe | Explore
What Evidence Do Scientists Use to Explain the Natureand Origin of the Universe?
The Origins of the Universe
Scientists estimate that the universe is about 13.7 billion years old. This is much
older than Earth. Earth is approximately 4.6 billion years old. The universe is also
much older than the solar system to which Earth belongs.
Scientists cannot make direct observations of most astronomical objects. Instead,
they must study the light from these distant objects to gain an understanding about
them. Scientists then can use this information from the objects’ light to better
understand the origin of the universe. Advances in technology over the last century
have allowed astronomers to make observations of fainter and more distant objects
across the entire electromagnetic spectrum. These observations have yielded
evidence about the origin of the universe. With this evidence, scientists developed a
theory to explain the initial formation of the universe. Scientific theories are ways of
explaining why things happen in the natural world. They begin with a hypothesis, or
an idea of how scientists think something works. Scientists then collect data to test
the hypotheses. Scientific theories are thought to be correct until new information
suggests alternative theories. Scientists always check theories by collecting more
observations and by experimenting.
Sometimes, new observations cause a theory to be reshaped or modified to match
Sometimes, new observations cause a theory to be reshaped or modified to match
the new evidence. The theory of how the universe came to be is explained by the big
bang theory. The big bang theory was first proposed in 1927. Today, the big bang
theory is generally accepted because many observations and experimental results
support it. However, details about the theory are still being debated.
Introduction to the Big Bang TheoryThe big bang theory states that the universe formed in a single event. How would you describe the big bangtheory?
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The Big Bang Theory
Less than a century ago, the universe was thought to be static and infinite. The
steady state theory held that the universe had always existed in its current state,
with a constant average density. However, in the 1920s, American astronomer
with a constant average density. However, in the 1920s, American astronomer
Edwin Hubble discovered that the universe was in fact expanding. This showed the
steady state theory to be invalid. The big bang theory eventually took its place as the
generally accepted theory to explain the origin of the universe.
The big bang theory states that the universe formed during a single event in which
all matter and energy suddenly expanded from an extremely small point. This point,
called a singularity, is thought to have been infinitesimal, infinitely dense, and
infinitely hot. It is thought to have been smaller than a single atom and made of
pure energy. One of the biggest mysteries of the universe is how the entire universe
inflated at an extremely high rate from a point smaller than a single atom to the size
of a baseball, almost instantaneously. This mystery continues to plague scientists,
but the laws of physics do allow for such an event.
To measure the age of the universe, scientists exploit the fact that light travels at a
known finite speed. Scientists express distances in the universe in units called light-
years. A light-year is a measure of distance in space equal to the distance that light
travels in one year. One light-year equals about 9.46 × 10¹² km. Because objects in
space are many light-years away, the light and other electromagnetic radiation that
an observer on Earth detects actually originated many years ago. An observer is
literally seeing into the past. This means that if scientists look back in time far
enough, they can make observations about earlier states of the universe. By
determining the rate at which the universe is expanding, scientists can work
backward to determine the age of the universe: approximately 13.7 billion years.
VIDEO SEGMENT
Understanding the Big Bang Theory
Understanding the Big Bang TheoryThe first step to understanding the big bang theory is acceptingthat the entire universe came from a single point, and since apoint has no mass, essentially everything came from nothing.What prompted scientists to change their...
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Expansion of the Universe During the Big BangThe universe expanded at a rate faster than the speed of lightfrom a single point smaller than an atom during the big bang.How do scientists describe the amount of time it took the bigbang to happen?
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The Light-YearA light-year is the distance that light travels in one year. Howfar does light travel in one year?
The Universe Following the Big Bang
During the initial expansion of the big bang, the laws of physics came into effect.
Science assumes that the universe works as a single system and the interactions of
mass and energy are governed by the same principles everywhere. The theories and
laws we develop from observations on Earth can be used to explain the formation of
the universe. Our understanding of gravity is a good example of this. Scientists say
the exact amount of gravity necessary to produce the universe existed in the
singularity. Too little gravity, and nothing would exist because matter never would
have formed. Too much gravity, and nothing but a series of black holes would have
formed. Because just enough gravity existed, some of the tremendous energy of the
big bang converted to matter in the form of electrons and other subatomic particles.
All objects in the universe are made of matter that developed during the first
fractions of a second following the big bang. The law of conservation of energy
states that energy can neither be created nor destroyed, but only changed from one
form to another. The theory of relativity states E = mc , which means energy is
equal to mass times the speed of light squared. That means that matter can be
changed into energy, and energy changed into matter. Scientists use these two laws
to explain how the energy from the expansion of a singularity can form the matter
in the universe. After the initial expansion, the universe was a hot soup of electrons
and other subatomic particles. As the universe slowed and cooled in the first second
of expansion, protons and neutrons formed. Within the first three minutes of
GravityThe laws of physics formed during the big bang. What role did gravity play in the big bang?
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of expansion, protons and neutrons formed. Within the first three minutes of
expansion, matter was still too hot to form atoms. The universe was a dense cloud of
protons, neutrons, and electrons from which no light could escape.
Mass exists in two opposing forms called antimatter and matter. For example, an
antielectron (also called a positron) has a positive electric charge. An antiproton has
a negative charge. Matter and antimatter annihilate each other when they come into
contact. This contact releases energy. For anything to exist in the universe, there
had to be more matter than antimatter. All objects that exist in the universe are
made of this excess matter. Some have found contradictions between the law of
conservation of energy and the big bang theory, since neither address where the
singularity of condensed energy originated. However, the big bang theory only
refers to the time after the singularity began to expand, and here the law of the
conservation of energy applies.
The two most common elements in the universe are hydrogen and helium. This is
because hydrogen and helium are the simplest atoms to form. Scientists think the
first atoms of hydrogen began to form three minutes after the big bang. Hydrogen
atoms contain only one proton, so when the universe cooled enough to form atoms,
these were the first to form. As the universe cooled further, helium atoms formed.
Helium atoms contain two protons. Next to form were lithium atoms, with three
protons. As the cloudy soup of protons, neutrons, and electrons ordered itself into
atoms, light penetrated through the universe for the first time, about 380,000 years
after the big bang.
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Matter and Antimatter
Matter and AntimatterMatter and antimatter cancel each other out. What isantimatter?
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Converting Energy to MatterDuring the earliest moments of the big bang, energy wasconverted to matter. How are matter and energy related?
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The Early UniverseIt took three minutes after the big bang for the first atoms toform, but another 380,000 years passed before the milkyuniverse became clear enough for light to shine through. Whydo we say that telescopes look “back in time”?
FULL VIDEO
Creating Conditions at the Big BangScientists use the Large Hadron Collider to simulate conditionsas they may have existed at the beginning of the universe.What questions can this tool help answer?
Evidence for the Big Bang Theory
Evidence that supports the big bang theory includes:
cosmic background radiation
cosmic background radiation
the measureable expansion of the universe
the relative abundances of the different elements in the universe
the known laws of physics
Cosmic background radiation, also known as cosmic microwave background (CMB)
radiation, is radiation that fills the observable universe almost uniformly. It is
thought to be left over from the big bang. It was first discovered by accident in the
1960s by the physicists Arno Penzias and Robert Wilson. The COBE (Cosmic
Background Explorer) satellite was launched in 1989. It gave the first clear images
of cosmic background radiation. The WMAP (Wilkinson Microwave Anisotropy
Probe) satellite was launched in 2001. It gave scientists a much clearer picture of
CMB radiation that was nearly uniform throughout the universe. In other words,
CMB radiation was made of electromagnetic waves with similar wavelengths. As a
result, scientists concluded that nearly all of the light within the early universe was
released at the same time. This evidence supports the big bang theory.
The small temperature variations found in the CMB represent slight density
differences. These density differences illustrate variations in the distribution of
mass throughout the early universe. Areas with more matter in the early universe
have large clusters of galaxies today. This evidence gives further support to the big
bang theory.
Scientific knowledge is based on the assumption that laws of physics operate the
same today as they did in the past. Using the data collected from spectral analysis,
CMB radiation, and red-shift evidence (explained later), scientists can infer
conditions of the past using the laws that are now known to be true. Applying the
law of the conservation of energy and the theory of relativity to observational data,
scientists have developed a plausible explanation of the origin of the universe.
Using Electromagnetic Radiation to Observe the UniverseScientists use electromagnetic radiation to gather information about stars. What information doeselectromagnetic radiation from space reveal?
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Hubble’s Observations
The expansion of the universe can be observed and measured. Observing the
expansion of the universe provides strong evidence for the big bang theory.
Measuring the rate of expansion allows scientists to work backward to determine
the precise age of the universe, beginning with the big bang.
In the 1920s, American astronomer Edwin Hubble made some of the first
observations of the expansion of the universe employing the principles of the
Doppler effect. The Doppler effect is the apparent change in the frequency of a wave
caused by the changing distance between the observer and the object emitting the
wave. When waves are moving toward an observer, they appear to be compressed,
resulting in an apparent shortening of wavelength and an increase in frequency.
When waves are moving away from an observer, the waves appear to be stretched,
resulting in an apparent lengthening of wavelength and decrease in frequency.
With light waves, the apparent change in wavelength shifts the light toward
different colors. Redshift is the apparent shift of light wavelengths toward the red
end of the electromagnetic spectrum. Redshift happens when a luminous object is
moving away from Earth. Blueshift is the apparent shift of light wavelengths toward
the blue end of the electromagnetic spectrum. Blueshift happens when a luminous
object is moving toward Earth. Both of these phenomena can be explained by the
Doppler effect.
If the universe is expanding, one would expect most objects in the universe to have a
redshift, meaning they are moving away from Earth. Hubble observed the redshift
of most galaxies in the universe, which is evidence for the expansion of the universe.
Scientists apply the rate of expansion backward to estimate the moment of the big
bang.
Hands-On Lab: The Doppler EffectIn this investigation, you will observe how the Doppler effect causes an apparent changein the sound emitted by a source. How would you describe your perception of sound asthe source moved?
Student Version
Teacher's Guide
Understanding the UniverseScientists use a variety of methods to study the expansion of the universe, the mostimportant method being the Doppler shift. How can the Doppler shift be used to determinethe motions of various stars?
Student Guide
VIDEO SEGMENT
The Origin of EverythingDr. Hawking explains that the Doppler effect makes distantgalaxies appear red as they are viewed from a telescope onEarth. How do the Doppler effect and redshift provide evidenceof an expanding universe?
READING PASSAGE
Edwin Hubble and the Hubble Space TelescopeThe Hubble Space Telescope is named after Edwin Hubble,who was key in invalidating the steady state theory. What greatdiscoveries have been made with this telescope?
VIDEO SEGMENT
The Doppler EffectThe Doppler effect is the apparent change in the frequency of awave caused by the changing distance between the observerand the object emitting the wave. How does frequency changeas an object...
More Evidence for the Big Bang Theory
The relative abundance of elements in the universe and the known laws of physics
provide additional evidence for the big bang theory. The two most common
elements in the universe are hydrogen and helium. In fact, hydrogen and helium
may compose more than 98 percent of the ordinary matter in the universe. The next
most common element in the universe is lithium. Recall that hydrogen, helium, and
lithium atoms contain, respectively, one, two, and three protons. They are the three
simplest elements, and so they would have been the first to form out of the soupy
mix of free protons and neutrons produced by the big bang. The fact that most of
the matter in the universe consists of these three simple elements is further
evidence for the big bang theory.
The remaining elements on the periodic table were made much later than hydrogen,
helium, and lithium. Irregularities in the density of the early universe allowed
gravity to exert an uneven pull on the matter in the universe. This uneven pull of
gravity allowed hydrogen gas molecules to come together. Countless collisions
between these hydrogen atoms generated tremendous heat. Eventually, they ignited
to form the first stars. The universe’s early stars formed the first galaxies, including
the Milky Way galaxy. The Milky Way is thought to be one of the oldest galaxies in
the universe, about 13 billion years old. Today, the universe is composed of billions
of galaxies. Stars and galaxies now contain most of the visible mass of the universe.
Stars are fueled by a process called nuclear fusion. Fusion is a nuclear reaction in
which the nuclei of certain light elements, particularly hydrogen, combine with
atoms with larger nuclei. This process is accompanied by an enormous release of
energy. The nucleus of a hydrogen atom contains one proton. During nuclear
fusion, hydrogen nuclei fuse together to form helium atoms with nuclei that contain
two protons. These heavier atoms sink toward the core of a star. They fuse into new
atoms of heavier elements with more and more protons in their nuclei. The heavier
elements continue to sink toward the core of the star. The nuclear fusion process
continues until iron is formed. Iron does not give off energy through nuclear fusion.
When most of the elements in the star have fused into iron, the star runs out of fuel.
Then, the star becomes more and more dense until it explodes into a supernova.
This explosion spreads the star’s elements throughout the universe. The energy
from the explosion causes more fusion, producing even heavier elements. The
deaths of the first stars gave birth to the elements of the universe.
The processes that first began immediately after the big bang continued, and they
are still occurring today. About five billion years ago, gas began to coalesce to form a
star known as the sun. Dust and gas coalesced around this star 4.6 billion years ago
to form a very special planet known as Earth. Nuclear fusion is still happening in
the sun and in countless other stars, and the universe is still expanding.
VIDEO SEGMENT
The Role of GravityIrregularities in the density of the universe allowed gravity tohave an uneven pull on matter. What elemental gases werebrought together in the earliest stages to form our universe?
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Copyright © 2017 Discovery Education. All rights reserved. Discovery Education is a subsidiaryof Discovery Communications, LLC.
VIDEO SEGMENT
Nuclear FusionNuclear fusion in the core of stars formed the heavy elementsup to iron. What process formed the heaviest elements in theuniverse?
VIDEO SEGMENT
The Hubble Deep FieldThis video segment discusses a long-exposure image thatrevealed an unimaginable number of galaxies in the universe.Why was this image so valuable to astronomy?
Deep Field Image from the Hubble Telescope | Early Observations andModern Exploration | Does the Evidence Support an ExpandingUniverse?
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