Presentation on theme: "What is the Big Bang Theory? Not the TV show.. It is a theory of what happened 14 (13.7) BILLION years ago. It tells us how the universe began! Singularity:"— Presentation transcript:
What is the Big Bang Theory? Not the TV show.. It is a theory of what happened 14 (13.7) BILLION years ago. It tells us how the universe began! Singularity: The theory is that one single finite speck (much much smaller than a pin head) with extremely high density and temperature instantly started expanding and inflating. (like the surface of an inflated balloon) The big bang is not an explosion of matter… it created space and matter and time…
Expansion of the universe! An astronomer noticed that there are more galaxies going away from us than approaching us Astronomers know that a galaxy is approaching or receding by looking at the spectrum of its light. If the spectrum is shifted toward a shorter wavelength (BLUESHIFT) then the galaxy must be approaching like a fire truck siren approaching you (shorter sound wavelength). If the spectrum is shifted toward a longer wavelength (REDSHIFT) then the galaxy must be receding. Like a fire truck siren that has passed you (longer sound wavelength) He observed more galaxies whose spectrum was redshifted than those whose spectrum was blueshifted
Hubble Edwin Hubble discovered that farther galaxies are going away from us at higher speeds. more distant galaxies had higher redshifts (light takes millions or even billions of years to reach us from a distant galaxy) This means we are seeing an image from millions or billions of years ago. He noticed that the light, when it was emitted, would have shorter wavelengths. But, he observed longer wavelengths…this is because….expansion of space over the years that the light was traveling to us! This redshift appeared to have a larger displacement for faint, presumably further, galaxies. Hence, Hubble’s Law- the farther a galaxy, the faster it is receding from Earth.
This graph shows different galaxies. Their distance apart (x) and the velocity at which they are spreading (y). Going backwards…the smaller the distance, the smaller the velocity. This continues until all matter is compacted into a completely shrunk volume of the universe that is incredibly dense. THIS is the moment of the big bang. (zero distance and zero velocity)
Dating In order to figure out how old our universe is, scientists examine the oldest things found in the universe. They use radioactive dating of uranium isotopes! we know that the oldest isotopes were created (through nuclear reactions in supernovae) about 10 billion years ago. We now know that the oldest stars in our Galaxy are about 12 billion years old. These ages are consistent with the age (13.7 billion) estimated from the observed expansion of the universe
Hydrogen and Helium Abundance in the Universe The most basic fundamental element is hydrogen. This was the first element to form after the big bang. Helium is created by nuclear fusion! Fusion of the nuclei of two hydrogen isotopes (deuterium) produces helium. Since this only occurs at EXTREMELY hot temperatures, it was theorized to have occurred during the big bang with the extreme temperatures.
Continued… Stars and hydrogen bombs are the only things we know of that make helium in the present universe. As we already know…H-bombs and stars combine hydrogen nuclei (protons) into helium nuclei through nuclear fusion, releasing great amounts of energy! Astronomers calculate that the night sky should be much brighter if all the helium we now observe had come from stars burning… Some, if not most, of the helium must have existed before star formation This abundance of helium is another piece of evidence that proves the big bang theory
studies of other galaxies have confirmed that the majority of the observed helium did exist before any star formation. Astronomers in the 1970s realized that no known process in the present universe could have produced deuterium (Remember, deuterium is an isotope of hydrogen with one extra neutron ). This is because any deuterium created in stars will immediately convert to helium due to the high temperatures. Scientists found that the some material between stars contain a trace of deuterium. Since stars could not have produced the deuterium, it must have been created either very early in the formation of the galaxy or even before!
Cosmic Background Radiation (microwave radiation) there is a very low energy and very uniform radiation that we see filling the Universe (the afterglow of the big bang) essentially a perfect blackbody spectrum obtained by NASA's Cosmic Background Explorer (COBE) satellite. (absorbs all electromagnetic radiation and emits it…so we can see where radiation is! Look at the pic below) This radiation is the strongest evidence for the validity of the big bang the radiation was originally produced in the big bang, but is now redshifted to longer wavelengths because we are seeing radiation from 14 billion years ago!