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The Big Bang Theory. A Theory in an explanation based on what is observed in the natural world and experimental evidence. What is the Big Bang Theory?. The theory states that the universe violently expanded in a single event called the “ Big Bang ” . Occurred 10-20 billion years ago .
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The Big Bang Theory A Theory in an explanation based on what is observed in the natural world and experimental evidence.
What is the Big Bang Theory? • The theory states that the universe violently expanded in a single event called the “Big Bang”. • Occurred 10-20 billion years ago. • The universe has been expanding since.
Notes of Concern! • It is believed that all matter and radiation was packed into a primeval fireball no larger then the period at the end of this sentence. • There was no“bang” or “explosion”, it is just a term. • Since there was no space prior, the big bang was more of an unfolding of space and matter from a very small region. Also time as we know it started.
What was created at the onset ofthe Big Bang? • Matter(Something that has mass and takes up space.) • Energy( ex. Radiation /Light ) • Time(A condition which has a past, present and future.) • Space(What the universe filled in.)
The first second • In one-millionth of a second after the Big Bang, the Universe was a hot, seething mass of radiation and exotic particles. • This mass expanded and cooled, forming protons, neutrons and electrons (subatomic particles).
Minutes later…….. These subatomic particles grouped together forming the first atoms of hydrogen and helium.
After several billions of years… GRAVITY caused clouds of gas to collapse, forming planets, stars, and galaxies.
And today… The present day Universe continues to expand. Galaxies and stars are continuing to move away from one other.
SO WHY DO SCIENTISTS BELIEVE THIS THEORY? The Big Bang is accepted because of three very persuasive pieces of evidence. 1. Red shift 2. The relative amounts of certain chemical elements in the universe 3. The existence of cosmic radiation detected by microwave telescopes
1. Red Shift When a star or galaxy's light is looked at through a special instrument called a spectroscope, scientists observe that the wavelengths have shiftedtoward the red end of the spectrum.
Red shift cont… The red end of the spectrum has longer wavelengths, thus meaning the object is moving AWAY from the observer. Example: When you hear an ambulance siren approaching, and then moving away.
2. Chemical Make-up Since, according to this theory, all matter was created at the Big Bang, the Universe today retains an imprint of its initial cosmic mixture. Astronomers can analyze a star’s chemical make-up and the ratio of hydrogen to helium. The amounts of these gases agree with what the Big Bang theory predicts.
The most convincing piece of evidence… COSMIC BACKGROUND RADIATION
3. Cosmic Background Radiation • The last signs ofheat left over from the Big Bang. • That original energy has cooled to -455F (a hundred million times cooler than a typical birthday candle!) • Can be detected by microwave wavelengths.
How will it end? The ultimate fate of our universe will be determined by the competition between the outward expansion and the inward pull of gravity (I’ve been told, in the end, gravity always wins)
The future of uncertainty • There are several interesting scenarios, ranging from never ending expansion, to a contraction inward called the Big Crunch. • It all depends on the density of the Universe, and that depends on the amount of matter it contains.
