There is no other phenomenon in the universe that can accelerate from stopped to top speed instantly. And as particles try to get closer and closer to this speed, they resist more and more. There is absolutely nothing in this world that behaves like light. Physicists don’t even know where there is a cosmic speed limit. All they know is that time stands still when you travel and the speed of light. Isaac Newton’s enduring fascination with light began when he was a child. By the time he was in his 20s, Newton had become the first person to decipher the mysteries of the rainbow, Newton discovered that sunlight or “white light” was a culmination of all the lights, He made this discovery by can/ing a small hole of light into a wall and then placing a prism in front of the beam of light. He named the displays of colors “spectrum” which was Latin for phantom. Fast fon/vard to the 18005.
At the time, everybody who went outside knew that sunlight carries heat. By night. William Herschel scanned the starry skies With the largest telescope at the world. By day, he asked whether or not different colors were different temperatures. When Herschel first set up this experiment he placed three thermometers on a table With two of them being on the Spectrum’s red and blue ends. The third was placed below red and served as the control of the experiment. As Herschel recorded the temperatures he found that red light was warmer than blue light. Something far more interesting however was going on with the control. After duplicating his experiment many times, Herschel discovered that there was a new form of light that was not seen by humans.
He named the light Infrared, which is Latin for below red. At about the time of Herschel’s discovery, Joseph Von Fraunhoferwas a small boy working in a glass making factory in Germany. By the age of 27, Joseph was the world’s leading optician. At the time, this acutely refined glass making process of optics, which were instrumental in creating spectacles, magnifying glasses, and telescopes, and was cutting edge and an extremely close guarded secret by the Bavarian Government. One day, while working in his laboratory, Joseph was experimenting with prisms and he wanted to get a closer look at the spectrum. He called upon his primitive telescope and looked into the prism while the light was passing through and saw not only the light spectrum. but a large sum of black stripes going through the light spectrum at random intervals and sections.
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Little did he know that written in those black lines were a secret code. Harvard University, 1902. An astronomer named Edward Pickering kept a room full of “computers”. In other words. he set up a team of women to map and classify the all stars of the night sky. One of them in particular would prowde a key to understanding the substance of the stars, and another would devrse a way to calculate the size of the universe. The latter was Annie Cannon who was the leader of the team and throughout her life would categorize 250,000 stars; leavrng the former to be Henrietta Leavitt, a woman who was not only the first to closely estimate the size of the universe. but could calculate the distances for stars as well. Henrietta once described the work she was doing in a letter to her sister: We take the light given off by a star by looking at it through atelescope.
We let the light fall into a prism, thus magnified; the light is split up into a band, showing its component colors, the red rays are at one end, and the Violet is at the other. This is the spectrum of the star. Each shows the presence of fine dark lines. By comparing them to glowtng elements in the laboratory, we can thusly determine that the same elements that are here on Earth also exist in the outermost star. During this time of categorization at Harvard. a woman by the name of Cecilia Payne (who was born and raised in England) was traveling to the only school that was willing to give her the opportunity to research and study; she was joining Pickering’s team of computers at Harvard University. As she took the observations of this scientific sisterhood. she tried to formulate a new way to look at how they were categorizing the stars with stellar spectra. She sought out a way to determine the size and chemical composition of the stars.
She also brought to the table her background in quantum physics. One theory was suggested by the most popular and distinguished astronomer at the time, Henry Russell: the dean of Princeton. He believed that because the most prominent components that are seen in the stars are calcium and iron, this naturally suggested that the stars were made up of the same elements that we have here on Earth and also roughly the same proportions. Cecilia Payne knew that the pattern of features in the spectrum of any atom was determined by the configuration of its electrons. She also knew that at high temperatures, one or more electrons are stripped from the atoms. which are then called ions.
The Indian physicist M. N. Saha had recently shown how the temperature and pressure In the atmosphere of a star determine the extent to which various atoms are ionized. Their categorizations of the stars were a temperature scale! With this new theory, Cecilia was also able to conclude that there is a million more times hydrogen and helium than the metals in the stars. She sent this thesis to Henry Russell. He took pity on Cecilia, and wrote to her that he believed her thesis was fundamentally and clearly impossible. It would be another four years until Russell would come to realize that Cecilia was correct all along.
Her method of determining stellar photospheric abundances (AKA the black lines in the light spectrum given off by a certain star) was to compare the strengths of the absorption lines that different atomic and Ionic species formed in the spectra of stars With the predictions from the statistical thermodynamics of their level populations and from the theory of radiative transfer in LTE model atmospheres of the appropriate temperature T and surface gravity 9 : GM / RAZ. Thus. she did not assume that hydrogen was deficient in a star simply because its hydrogen lines were weak in absorption in optical spectra. She computed how many hydrogen atoms could be expected under the circumstances that not all hydrogen nuclei would be cloaked.
With an orbital electron. and not all of the orbital electrons would be present in state n = 2 available (With known radiative-absorption cross-sections from the old quantum theory) to produce absorption of a photon at the appropriate Balmer wavelength. What she found when she took these factors into account, was under the assumption of level-state and ionization-state populations given by the theory of statistical thermodynamics. was that hydrogen was more abundant than helium (by. as we now know. about a factor of ten in number). and that helium was more abundant than yet heavier elements, with the result holding for all normal stars, including the Sun. The following list gives a modern compilation of the ten most abundant elements the solar atmosphere and in the most primitive of meteorites, as determined by geochemical analysis.
