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He changed people's view of the universe. Today's astronomers are studying the universe in the direction he pioneered. A giant telescope in space survey is also named after him. He is the American astronomer Edwin Hubble.

Edwin Hubble was born in Missouri. He studied at the University of Chicago, and many teachers at the University of Chicago remembered him until many years after graduation. The tall and shy boy is good-looking, not good at words and does not like to socialize. Except for the language class, all the other grades are excellent. His outstanding sports skills made him famous at school. In only one track and field event in 1906, he won seven championships in pole vaulting, shot put, discus, hammer, standing high jump, run-up high jump and relay. In the same year, he set a high jump record in Illinois. In addition to track and field, he also likes basketball, football and long-distance running. This tall figure can always be seen in a group of boys who love long-distance running. He is also a major member of the college basketball champions at the University of Chicago.

In May 1914, Hubble realized his dream to study and work at the Chicago Observatory. After receiving his doctorate from here in 1917, Hubble received an invitation from the Mount Wilson Observatory in Pasadena, California, which was an excellent opportunity. But after the defense of his doctorate, he joined the army because of the outbreak of World War I. in 1919, he came to the Mount Wilson Observatory in military uniform.

Hubble and his sister Lucy Hubble were lucky that he came to the right place at the right time. At that time, astrophysics was just beginning as a new discipline, and the Wilson Observatory became the center of observation in this field, while the 100-foot-tall, 2.5-meter Hook Telescope, the most powerful astronomical observation tool in the world at that time, has just been built after nearly 10 years of assembly. The ambitious Hubble took off his uniform and went to work.

The Hook Telescope over the next 10 years, Hubble began to study the two most fundamental questions about the universe. How big is the universe? How long did he survive? To understand these two problems, we need to know how far away a galaxy-like system is and how it is moving. Astronomical observation day after day, year after year, on the top of the mountain in winter night, we have to endure the piercing wind and face complicated and lifeless numbers during the day. For ordinary people, this is a lonely and unbearable job, but Hubble is obsessed with it.

During this period, the famous astronomer Harlow Shapley of Harvard University, who later became one of his strongest competitors, became world-famous for having just finished measuring the size of the Milky way. Just then, Henrietta Leavitt, a talented female astronomer at Harvard College, came up with a very clever way to use the Cepheid variable as a benchmark for celestial distance, which became the basis of Hubble's work.

Cepheid variable star is a kind of red giant star with heartbeat characteristics, which is often called standard candlelight star. In the process of burning the remaining fuel, Cepheid variables are not only very bright, but also have specific periods of brightness changes, so it is easy to identify them.

The relative positions between the Cepheid variables can be calculated through the different angles of the Cepheid variables in the sky, and then the relative distance between the galaxy and the Earth can be calculated by observing the brightness of the Cepheid variables. Shapley's result is that the Milky way is 300,000 light-years across, but according to current measurements, the Milky way as a whole is like a large disk slightly thicker in the center, with a diameter of 100,000 light-years and a central thickness of 12,000 light-years. At that time, because of Shapley's popularity, astronomers generally believed that 300,000 light-years was the scale of the universe.

Since 1919, Hubble has used the Hook Telescope to observe several spiral galaxies, including Andromeda and Triangle, at the Mount Wilson Observatory in California, and measure their distance to Earth.

He made his first new discovery in October 1923, a new star in the Andromeda M31 nebula. He carefully examined photos taken by other astronomers, including Shapley, in the same position in the past, and identified the star as a variable star in the constellation Andromeda, so he used Levitt's method to measure the distance of the variable star. He found that the M31 Nebula, where the variable star is located, is millions of light-years away from Earth. At first, he was skeptical of his results, and then he examined several other spiral galaxies, including Triangle, and found that these galaxies were far beyond the Milky way, not only that, but also like the Milky way. it has millions of stars.

The results observed by Hubble show that the actual universe is much larger than people think, and that the Milky way is only one of the galaxies in the universe. This conclusion was difficult to accept at that time, and undoubtedly subverted the previous understanding of the universe as the heliocentric theory replaced the geocentric theory.

Hubble's discovery was opposed by many astronomers, including Shapley. Even so, he published his observations and ideas in the New York Times. He formally submitted his paper to the American Astronomical Society and officially published it in the Bulletin of the National Scientific Association on March 15, 1925. The New York Times called it a major discovery and said in the report: "the Vortex Nebula discovered by Dr. Hubble confirms that it, like our own, is a 'cosmic island' world." Later astronomical observations confirmed that Hubble was right. Hubble's discovery expanded people's understanding of the frontiers of the universe by millions of light-years. For this great discovery, Hubble won the American Academy of Science Award and a prize from the Bolton Livingston Commission.

Hubble's achievement is just the beginning, and he has made a bigger breakthrough again. In 1929, using the 5-meter telescope of the Palomar Observatory, he re-examined the galaxies discovered in the past one by one. He found that the wavelengths of light emitted from distant galaxies became longer and the spectral lines moved toward the red end. this is undoubtedly the response of the Doppler effect in light waves, known as the "redshift" phenomenon, the result of the movement of light sources away from us. Hubble concluded that distant galaxies are not only receding from us, but galaxies are also moving away from each other.

Hubble was so excited by the discovery that he used the magnitude of the spectral "redshift" to calculate the speed at which distant galaxies moved away from each other. After careful study, he found an important rule, that is, "the speed at which galaxies move away from each other is proportional to the distance between them." Later, this law was called "Hubble's law", and the ratio of velocity to distance was "Hubble constant".

Hubble's subsequent conclusion was even more earth-shaking, saying: "this means that the universe may have started with an incredible Big Bang, the Big Bang." Hubble's story about the Big Bang is the same as that of Belgian priest George Lemette, but two people come to the same conclusion in different ways, one from astronomical observation and the other from theory.

In 1927, Lemette first obtained the solution of Einstein's gravitational field equation. according to the nature of this solution, he pointed out that the universe was expanding and was the first to propose that the universe originated from a "primitive atom". As a result of the Big Bang of this unstable "primitive atom", the present universe was created and the universe continues to expand to this day. Unfortunately, Lemette's paper was published in an unknown publication and did not attract people's attention. Lemette's theoretical calculations coincide with Hubble's observations, and they come from the same period, so they have a strong impact on astronomy.

Hubble's discovery caused a sensation and subverted the traditional astronomical community's view that the universe is not as stable and static as people think. Before Hubble's discovery, Einstein learned that his gravitational field equation had obtained a solution to the expanding universe, but Einstein thought that the universe should be stable. "in order to maintain the stability of the universe," a cosmic term was specially added to the equation.

After learning about Hubble's results, Einstein, the world-famous old physicist, came to Mount Wilson to meet with Hubble to express his gratitude and said he had "made the biggest mistake of his life."

The second person from the left is Hubble, the fourth is Albert Michelson, and the fifth is Albert Einstein, taken at the library of the Wilson Observatory.

In more than a decade of observations, Hubble has obtained data on 46 extragalactic galaxies, all of which conform to Hubble's law without exception. Hubble's discovery of the expansion of the universe confirmed the Italian astronomer Lemette's hypothesis about the origin of the universe. Together with Lemette, he promoted the progress of astronomy, led to the emergence of the Big Bang theory, and pioneered cosmology.

The picture taken by Hubble with the telescope that discovered the redshift often has a misconception about the expansion of the universe, thinking that cosmic galaxies retreat outward like the expansion of a sphere. In fact, there is an essential difference between the expansion of the universe and the expansion of the sphere. The expansion of the sphere is centered on one point and expands outward, but the expansion of the universe not only has no center, but also uniformly distributed in all directions, that is to say, the expansion of the universe spreads outward at any point in time and space.

The Hubble constant marks the rate of expansion of the universe, but this "speed of expansion" is different from the normal speed, adding a "million second gap" in its unit denominator, that is, a gap of kilometers per million seconds. "million second gap" is a unit of distance, its size is about 3.26 million light-years. Because this distance is added to the denominator of the Hubble constant unit, the meaning of the "cosmic constant" is different from the normal speed. The cosmic constant has a value of about 68 kilometers per million seconds, which means that the distance between galaxies increases by 68 kilometers per second for every "million second gap" from the observer. This shows that the farther away from the observer, the greater the speed of retrogression of the universe, and the peculiar nature of this retrogressive speed is a sign that the expansion of the universe has no center.

Hubble devoted his life to the cause of astronomy, and he changed people's understanding of the universe. Unfortunately, the Nobel committee at that time failed to recognize the value of Hubble's achievement in astrophysics, let alone pay enough attention to it, and astronomers were not sufficiently prepared to accept this valuable achievement, so at that time, Hubble's discovery did not have the due impact. Shortly after Hubble died of a heart attack in 1953, the Nobel committee responded by including astronomical achievements in the scope of accreditation.

Half a century later, people began to realize the importance of the greatest astronomer of the century. On March 6, 2008, the United States issued stamps to commemorate Hubble. Victor Stubbin, the designer of the stamps, wrote in the design document: "Hubble is the pioneer of the vast universe and the whistleblower of the complex universe, and it is his meticulous and rigorous study of distant galaxies that proves the existence of extragalactic galaxies. If he hadn't died suddenly in 1953, he would have won the Nobel Prize that year. "

Source: 365 days in the History of Science, slightly edited by: Wei Fengwen Wu Yi Editor: Zhang Runxin this article comes from the official account of Wechat: Origin Reading (ID:tupydread), author: Wei Fengwen, Wu Yi, Editor: Zhang Runxin

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