Benchmark 4A
The Physical Setting: The Universe
Grades 9-12, page 65
On the basis of scientific evidence, the universe is estimated to be
over ten billion years old. The current theory is that its entire contents
expanded explosively from a hot, dense, chaotic mass. Stars condensed by
gravity out of clouds of molecules of the lightest elements until nuclear
fusion of the light elements into heavier ones began to occur. Fusion released
great amounts of energy over millions of years. Eventually, some stars
exploded, producing clouds of heavy elements from which other stars and
planets could later condense. The process of star formation and destruction
continues.
NSES Content Standard D
Earth and Space Science: Origin and evolution of the earth system
Grades 9-12, page 189
The sun, the earth, and the rest of the solar system formed from a
nebular cloud of dust and gas 4.6 billion years ago. The early earth was
very different from the planet we live on today.
NSES Content Standard D
Earth and Space Science: Origin and evolution of the universe
Grades 9-12, page 190
The origin of the universe remains one of the greatest questions in
science. The "big bang" theory places the origin between 10 and 20 billion
years ago, when the universe began in a hot dense state; according to this
theory, the universe has been expanding ever since.
NSES Content Standard D
Earth and Space Science: Origin and evolution of the universe
Grades 9-12, page 190
Early in the history of the universe, matter, primarily the light atoms
hydrogen and helium, clumped together by gravitational attraction to form
countless trillions of stars. Billions of galaxies, each of which is a
gravitationally bound cluster of billions of stars, now form most of the
visible mass in the universe.
NSES Content Standard D
Earth and Space Science: Origin and evolution of the universe
Grades 9-12, page 190
Stars produce energy from nuclear reactions, primarily the fusion of
hydrogen to form helium. These and other processes in stars have lead to
the formation of all the other elements.
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