1. The Universe

2. Energy travels from stars in the form of electromagnetic waves. Electromagnetic waves can travel through empty space because they do not require a medium. Electromagnetic waves can be: radio, microwave, infrared, visible light, ultraviolet, x-ray, and gamma ray. Each type of electromagnetic wave has a different wavelength with radio waves being the longest and gamma rays being the shortest.

3. The only type of electromagnetic waves that we can see without special instruments is visible light. In visible light, each color has a different wavelength with red being the longest wavelength and violet being the shortest. Because distances are so far in the universe, we use light-years to measure distance. One light-year is the time that it takes light to travel in one year. This distance is exactly 9,460,730,472,580.8 kilometers which is about 5,878,625,373,183.608 miles (about 6 trillion miles).

4. Doppler Shifts Light from moving objects appears to have different wavelengths depending on the relative motion of the source and the observer. This change in wavelength is called the Doppler effect. Light that is compressed from an object moving towards the observer will have a shorter wavelength which is called a blue shift. Light that is expanded from an object moving away from the observer will have a longer wavelength which is called a red shift.

5. Through the use of mathematical calculations and the spectral analysis from a spectroscope, blue and red shifts can be determined. A spectroscope works by breaking light into the wavelengths (or spectra) that make it up. Some spectroscopes are made of diffraction grating- a material that has lots of little parallel lines that are approximately one wavelength apart. There may be 35,000 of these little lines in one inch of the material. When light hits the lines, it bends. Scientists can tell the elements present in a star by looking at its light through a spectroscope. Each element will have its own unique spectral lines of color, just as people each have a unique fingerprint. Different wavelengths (colors) of light bend by different amounts, so it splits the light into its colors. Other spectroscopes are made of prisms- as light passes through the glass, the different wavelengths slow down by different amounts and are bent into their colors. The above picture shows 4 spectral analyses; the bottom is a stationary star and the ones above show galaxies getting progressively further away. Notice the shift in the spectral analysis.

6. Even more significantly, the evidence from the analysis of light from distant galaxies in our universe shows that the light from these galaxies show red shifts. These galaxies are moving away from the Earth. In astronomy, these red and blue shifts prove helpful. When observing a system, you can tell which is moving toward you and which away by analyzing how the frequencies change. In fact, the results of this are a bit beyond the mere Doppler effect. This is actually a result of space/time itself expanding, as predicted by general relativity. Extrapolations of this evidence, along with other findings, support the "big bang" picture of the origin of the universe.

7. The formation of the universe is difficult, if not impossible, to understand completely because humans simply do not know what the conditions of the early universe were like. Because of this fact, the science of cosmology was developed as a means of studying the origins of our universe. Although it is unlikely that cosmologists will ever fully comprehend the exact process from which our universe was born, there are numerous theories as to how it may have happened. Three possible theories are: 1.Big Bang Theory 2.Steady State Theory 3.Oscillating Universe Theory Origin of the Universe

8. The most widely accepted theory in the field of astronomy today is the Big Bang Theory, first proposed in the 1920s and 1930s. By observing physical properties of the universe, proponents of this theory speculate that time began about 12 to 15 billion years ago when all of the matter within the universe exploded from a singularity, a dense point with an infinitely small volume. Big Bang Theory The Big Bang theory is based upon three main supporting pieces of evidence.

9. The first of pieces of evidence is that the universe appears to be expanding. By observing light from distant galaxies, it was discovered in the 1920s that this light is shifted towards the red end of the spectrum, implying that these distant galaxies are moving away from the Earth. The Big Bang theory states that this recession is not due to the movement of the galaxies through space, but instead is an expansion of space itself. Assuming that the universe is expanding as a whole and that it has been since the beginning of time, cosmologists extrapolate back in time to when the universe was a small point.

10. The second piece of evidence relates to the relative abundance of chemical elements within the universe. The Big Bang model predicts that the universe should be composed of approximately 75% hydrogen, 25% helium, and small amounts of heavier elements. Although these predictions depend on the initial conditions of the early universe, which are nearly impossible to know accurately, the observable universe is nonetheless composed of about three-quarters hydrogen and one-quarter helium, along with small amounts of heavier elements.

11. The third piece of evidence concerns cosmic radiation. In 1948, a Russian astronomer named George Gamow speculated that the initial fireball of the Big Bang explosion should have left behind a uniformly distributed radiation which would fill the universe and cool as the universe expanded, and be visible in every direction of the sky. The Cosmic Background Radiation (CBR), as this radiation is called, was first detected in 1965 in the form of radio waves, and has a uniform temperature of 2.7K. The discovery of this radiation swayed many astronomers in favor of the Big Bang theory. Every theory involves assumptions, and the Big Bang is no exception; however, despite being proposed in the 1920s, the model has survived the scrutiny of 80 years of technological advancements and competing theories, contributing to its credibility.

12. One implication of the Big Bang Theory is that the universe may grow cold and dark and die an ultimate heat death. This will happen if the universe expands forever. Although this scenario will destroy all life, the universe itself would survive for an infinite period of time. This would be the outcome if the expansion of the universe were what scientists call an open universe. Open universe due to the Big Bang: The galaxies will continue to expand "forever“ All stars will eventually use up their fuel and burn out Universe will then be cold and dead Possible Future of the Big Bang Theory

13. Steady State Theory In addition, to account for the decrease in density that would result from expansion, steady state theory claims new matter constantly must be created in order to maintain a constant density (and therefore a static appearance). Steady State theory states that the universe looks the same no matter the viewpoint and that the universe has always looked like this; essentially, the theory states that the universe is uniform throughout both time and space. The advantage of Steady State theory over some other theories is its simple explanation of certain troublesome topics. For example, since the universe is unchanging throughout time, the universe needs explanation of its beginning. The future of the steady state theory suggests a flat universe.

14. Oscillating Universe Theory One of the implications of the big-bang theory is that the universe will one day end, or at least any life in the universe will come to an end. If the universe is either open or flat, meaning that it expands forever, it will survive for a finite period of time. But eventually all the material in all the generations of stars will be exhausted, and the universe will grow cold and dark. Some scientists speculate that due to the amount of gravity in the universe, that the matter moving outward following the Big Bang will eventually be slowed and pull back toward the center of the universe resulting in the Big Crunch. It possibly would not signal the end. Perhaps another Big Bang would follow the Big Crunch, giving rise to a new universe of possibilities. The idea that Bangs follow Crunches in a never-ending cycle is known as an oscillating universe. Though no theory has been developed to explain how this could ever happen, it has a certain philosophical appeal to people who like the idea of a universe without end.

15. Let’s talk about quasars … Quasars are the most distant objects in the universe and are about 12 billion light years away. Quasar is an acronym that stands for quasi-stellar, radio sources. Quasars are star-like objects that give off radio and x-ray electromagnetic waves. Scientists believe that quasars represent the earliest stages of galaxy formation… but why?

16. A look back in time ??? To travel 12 billion light years, it takes light 12 billion years to travel that distance. So the light leaving the quasars, left them 12 billion years ago. When we look at quasars that are 12 billion light years away, we are looking at those quasars as they existed 12 billion years ago. So we are actually looking back in time. Remember that we believe that the universe is 12-15 billion years old, so these quasars represent the early objects that existed near the beginning of the universe.