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Doppler effect and how it relates to stars

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Doppler effect and how it relates to stars

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If anyone has ever heard a car with a siren drive by they would notice that it sounds higher pitched until it passes you when it becomes lower pitch. Since light is also a form of wave we can use this to determine how far away stars are and if they are moving away or towards us. We can determine this based on the color the star emits. A red star would most likely mean the star is far away and moving away from us while a purple star would mean the opposite.

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The text was first published in 1966. Considering how far technology has developed sic 1966 I would have to see that some of the information is inaccurate but I would guess the historical information is accurate. How does the publishing date relate to the history of the topic.

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In 1840 an astronomer named Henrich Olber created the theory that the universe cannot be infinite or the stars cannot be infinite. He argued that if the universe and stars are infinite we should be receiving infinite amount of light. If we thing of the universe as rings surrounding our galaxy and solar system each ring should have the same amount of stars and therefore have the same luminosity but they do not as if they did the entire sky would appear as one giant glowing object.Another astronomer Herschel decided to count the amount of stars in hundreds of different regions around space. He found that the number of stars increased the closer he got to the milk way cluster (as it was known before galaxies were known).Knowing that more stars were closer to the cluster he theroized that we exist on a similar plane to this group of stars which is now known as a galaxy.

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The text is comprehend able to me although I would say it requires a little background knowledge in trigonometry and probably some history.The text structure and formatting help the reader to understand the text very well especially with the footnotes and pictures added the contribute to the readers understanding of the text.

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Many renaissance astronomers noted that certain stars are brighter than others. Today we know for sure that this is because the stars are vast distances away from earth. Renaissance astronomers rated the stars based on what they could see on a 1 to 6 scale. Today we use high tech instruments that measure light to detect in greater accuracy how far away these stars are.

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Isaac Asimov had a PhD in chemistry from Columbia and later became a professor at Boston university. He wrote over 500 science-fiction and nonfiction stories some of these include famous books such as I, robot.

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I know they basics on how gravity attracts and how we can measure how strong gravity is.I also know how we measure how far away a star is and how fast objects are moving away from this. Along with this extra knowledge I also have a basic understanding of physics from my high school physics class.

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Why does a black hole consume matter and how can it consume light?
How where elements formed after the big bang?
Is the universe still expanding? Are entire galaxies effective by the gravity of a super massive object?
How do we know how far away objects that are not stars are?
How did primitive people figure out the earth wasn't flat?
How did we theorize planets and their orders without the modern telescope?

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How we figured out the Earth wasn't flat.

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How we figured out the Earth wasn't flat.

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In very early history scientist and philosophers believed that the earth was flat. However along the way many people thought this idea is unrealistic. People started to realize the earth was not flat because they would watch ships leave harbor and disappear into the distance. This was not because they couldn't see that far but because it was not on the same plane as them.This idea was first establish by a Greek philosopher in 382 B.C.

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How we figured out the order of the planets

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How we figured out the order of the planets

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Greek astronomers theorized that the stars and the planets were like a giant dome moving around the earth every 24 hours. From this knowledge the could determine the order of the seven celestial bodies they could see. This included Mars,Jupiter,Saturn,Venus,mercury,the sun and the moon. The figured out the moon had to be in front of the sun because during solar eclipses it passed in front(keeping in mind that at this point we thought the solar system revolved around the earth). They also knew that things appeared to move faster the closer they are so from the knowledge they could measure how fast the planets move and try and come up with an order. Hundreds of years later using geometry and the fact that we knew how big the earth was they were able to approximate the distance the moon was away from the earth and the approximate size.Later in the early renaissance period astronomers would be better able to detect how far way objects are using what is called the parallax method witch much greater accuracy.

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The foot notes are useful for defining the words in the text that I may not understand so that I don't have to look them up.