the big bang theory
Timeline of the Big Bang and the expan- sion of the Universe. The Big Bang theory is the most widely accepted cosmological explanation of how the universe formed. If we start at the present and go back into the past, the universe is contracting getting smaller and smaller. What is the end result of a contracting universe? According to the Big Bang theory, the universe began about 13.7 billion years ago. Everything that is now in the universe was squeezed into a very small volume. Imagine all of the known universe in a single, hot, chaotic mass. An enormous explosion a big bang caused the universe to start expanding rapidly. All the matter and energy in the universe, and even space itself, came out of this explosion. What came before the Big Bang? There is no way for scientists to know since there is no remaining evidence.
after the big bang
In the first few moments after the Big Bang, the universe was unimaginably hot and dense. As the universe expanded, it became less dense and began to cool. After only a few seconds, protons, neutrons, and electrons could form. After a few minutes, those subatomic particles came together to create hydrogen. Energy in the universe was great enough to initiate nuclear fusion, and hydrogen nuclei were fused into helium nuclei. The first neutral atoms that included electrons did not form until about 380,000 years later. The matter in the early universe was not smoothly distributed across space. Dense clumps of matter held close together by gravity were spread around. Eventually, these clumps formed countless trillions of stars, billions of galaxies, and other structures that now form most of the visible mass of the universe. If you look at an image of galaxies at the far edge of what we can see, you are looking at great distances. But you are also looking across a different type of distance. What do those far away galaxies represent? Because it takes so long for light from so far away to reach us, you are also looking back in time (Figure 1.2).
After the origin of the Big Bang hypothesis, many astronomers still thought the universe was static. Nearly all came around when an important line of evidence for the Big Bang was discovered in 1964. In a static universe, the space between objects should have no heat at all; the temperature should measure 0 K (Kelvin is an absolute temperature scale). But two researchers at Bell Laboratories used a microwave receiver to learn that the background radiation in the universe is not 0 K, but 3 K (Figure 1.3). This tiny amount of heat is left over from the Big Bang. Since nearly Images from very far away show what the universe was like not too long after the Big Bang. all astronomers now accept the Big Bang hypothesis, what is it usually referred to as? Click image to the left or use the URL below. URL:
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the big bang theory is a hypothesis that states that all matter and energy were at one time compressed into a small volume and then __.
a) imploded --> b) expanded outward c) stayed compressed d) none of the above
the first stars didnt form until about 4 billion years after the big bang.
a) true --> b) false
according to the big bang theory, the universe began
a) 1 billion years ago b) 3.7 billion years ago --> c) 13.7 billion years ago d) 23.7 billion years ago
at the time of the big bang and just after
a) all the matter and energy of the universe was compressed into a point. b) after a few seconds, protons, neutrons and electrons formed. c) after a few minutes, hydrogen formed. --> d) all of the above.
during the immediate aftermath of the big bang, hydrogen nuclei collided and fused into ____ nuclei.
a) oxygen b) carbon --> c) helium d) potassium
in the early universe, matter was held together by which force?
--> a) gravity b) centrifugal c) inertia d) attractive
scientists have discovered the temperature of space is 3oc.
a) true --> b) false
which of the following is true?
a) the temperature of space in the universe is 0 kelvin. --> b) a tiny amount of heat left over from the big bang is spread around the universe. c) galaxies and the space between them are the same temperature. d) there is no evidence for the big bang beyond the expanding universe.
at the farthest edges of what scientists can see, there are
--> a) galaxies that formed not long after the big bang. b) galaxies that formed recently. c) no things that astronomers can identify. d) nothing but blobs of gas and dust.
its very difficult to determine scientifically what existed before the big bang because there is no evidence.
--> a) true b) false
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