Edwin Powell Hubble known as Edwin Hubble was a famous American astronomer who played an important role in formulating the basic principles of extragalactic and observational astronomy. Historians and astronomy experts consider him one of the most important astronomers in history. Hubble placed the space clouds, which before her time were known as gas and dust particles and were in the category of nebula or nebula, in the category of galaxies.. Historians consider Hubble’s discovery of other galaxies equal to Copernicus’ theory in terms of scientific value. Copernicus proved that the Earth is not at the center of the solar system, and Hubble proved that the Milky Way is not the center of the universe.

One of the important scientific relics of this astronomer is Hubble’s law in space. In short, this law states that the universe is expanding at a constant rate. In addition, in this law, the distance of each galaxy from the edge of the universe is directly proportional to its speed. Of course, this law was discovered two years before Hubble’s presentation by Georges Lemaitre, but its fame came to Hubble. The Hubble telescope is one of the most famous monuments built in the name of this legendary astronomer. An example of this telescope is installed in his hometown of Marshfield, Missouri. This telescope was sent into Earth orbit in 1990 to capture more detailed images of space outside the Milky Way.

Edwin Hubble has another great achievement in the field of cosmology and that is the classification of galaxies. This classification has been used by astronomers for many years. Hubble played a significant role in adding the astronomy category to the Nobel Prize. Of course, the sudden death of this scientist in 1953 prevented him from receiving this award.

Birth and education

Edwin Hubbell was born on November 20, 1889, in Marshfield, Missouri. His mother was Virginia Lee James and his father was John Powell Hubble. His father was a lawyer and insurance businessman. Edwin was the third child out of 8 children in this family. Of course, like many children of those years, some of Edwin’s siblings died in childhood.

Hubbell lived in a rich family that had to migrate many times because of his father’s work style. During these trips, which were generally in cities around Chicago and Illinois, they lived in luxurious houses with many servants. The children of the Hubble family were all brought up with work and responsibility; Because their parents believed that this style of upbringing would increase their sense of responsibility.

Hubble completed his high school education at Wheaton High School near Chicago. He finished high school easily and with excellent grades in English, mathematics, biology, chemistry, physics, Latin, and German languages. Of course, in high school, Edwin was more into sports than studying, and he owed his high grades to his innate intelligence. On his father’s advice, he was busy delivering goods on holidays. Finally, Edwin Hubbell graduated from high school in 1906 at the age of 16 and received a scholarship to the University of Chicago. He worked at this university as a laboratory assistant of the famous physicist Robert Millikan (Nobel Prize winner).

Edwin Hubble (left), with friends after returning from Oxford

After entering the university, sports still occupied a large part of Hubble’s time. He was fond of sports such as basketball and boxing. He was a tall and strong person and he left several records during his university days. Edwin Hubble graduated from the university in 1910 with a bachelor’s degree in general science and honors in physics and astronomy.

After graduating from the University of Chicago, Hubbell entered Oxford University with a Rhodes scholarship and studied there for three years. Hubble was quickly influenced by English culture and changed many of his past behaviors and habits and adopted an English appearance. Contrary to his strong interest in experimental sciences and especially astronomy, he chose the field of law theory out of respect for his father and graduated from Oxford in 1912. He stayed at this university for another year and studied Spanish. While studying at Oxford, Hubble had another achievement including traveling around Europe. In these trips, in addition to having fun, he paid special attention to planning and thinking about his future. In those years, Edwin wrote in a letter to his mother:

Work is pleasant when it is for a great purpose and end. A goal so great that the thought of it and the anticipation of its achievements, will remove all the fatigue of the difficult task. When I find the purpose and principles I want, I leave everything for it and dedicate my life to it.

Edwin’s father died in the fall of 1912. He asked his father for permission to leave Oxford to visit him but was refused. Young Edwin remained in Oxford and his father died in January 1913.

Hubble exploring the cave

His Career

Finally, at the age of 24, Edwin entered the field of science, which he had become interested in nearly two decades ago by observing space through the lens of his grandfather’s telescope. Upon entering the observatory, he began his doctoral course in astronomy and received his degree in 1917 with a thesis entitled  Photographic Investigations of Faint Nebulae. With the outbreak of World War I, Hubble served in the army for a year and rose to the rank of colonel despite not being actively involved in combat. He then went to Cambridge University to study astronomy.

Edwin Hubble started working at the Mount Wilson Observatory in California in 1919 at the age of 30. This observatory is famous for its excellent weather and excellent observation conditions. These factors made Hubble research in this place until the end of his life.

Hubble membership card in the army

Scientific achievements

As mentioned, Hubble wrote his doctoral dissertation on nebulae. He continued his research at Mount Wilson using the world’s largest telescope, the Hooker telescope. Hubble’s great discoveries, including galaxies beyond the Milky Way and the phenomenon of redshift, were the results of this astronomer’s research using the Hooker telescope.

In 1912, the American astronomer Henrietta Leavitt published an important discovery related to stars called the Cepheid variable. Beginning in the 1930s, Hubble was able to discover similar stars in nebulae using the Hooker telescope. While studying the Andromeda Nebula, he realized that these stars are very far from Earth and much farther than the stars of the Milky Way.

• His high-quality images of Andromeda and the Triangulum Nebula showed a massive cluster of stars.
• Many of the stars were of the Cephasian type.
• The studied nebula is one million light years away from Earth. 4 times more than all the objects that had been discovered until that time. (Of course, this distance is proven to be equal to 2.5 million light-years today.)
• The diameter of the Andromeda Nebula is 30 thousand light years. (Today, these dimensions have been proven to be 220,000 light years.)
• Andromeda galaxy emits light equal to one billion suns of our system.

Hubble published his findings three days after his 35th birthday. Of course, his discoveries were not published in a scientific journal, but in the New York Times. The results of his research were debated among astronomers for some time, and finally, his paper was reviewed at the meeting of the American Astronomical Society on January 1, 1925. Hubble changed everyone’s view of the universe with his discoveries. He proved that our vast galaxy, host to the Sun and hundreds of billions of similar stars, is only one of the billions of galaxies in the universe.

Andromeda Galaxy

In addition to this discovery, Hubble provided a standard for classifying galaxies that was used by astronomers for years.

Redshift phenomenon

Prominent astronomer Veslu Slifer has also researched nebulae. He stated in his report in 1913 that the light of the nebula tends towards the red color of the color spectrum. He explained his discovery as a form of the Doppler effect. According to the same explanation, the light tends to the red side of the color spectrum as the emission source moves away, similar to the Doppler effect. To test his discovery, Slifer studied many nebulae. He came to the conclusion that the light of many of these nebulae has a fast transition towards red color and as a result, they are moving away from Earth at a high speed.

The required density of matter is several times higher than the estimated maximum density of matter concentrated in the nebula. Furthermore, we have no evidence of significant interstellar matter increasing the density.

Classification of galaxies by Hubble

However, although Hubble had a lot of resistance to accept the effect of redshift, in his research he found that the speed of this expansion is slowing down. However, these findings and research on the speed of galaxy expansion are still ongoing and astronomers discover new issues every day.

One of the historical events regarding the theory of the expanding universe is Albert Einstein’s meeting with Edward Hubble in 1931. The two met at Mount Wilson Observatory. In 1917, in his theory of relativity, Einstein considered the universe to be constant and without change in size. He did not see any end or end to the universe. Although his research showed signs of the expansion of the universe, this scientist tried to deny it by determining a constant called the cosmic constant.

However, the January 1931 meeting earned Hubble the nickname of the man who forced the world’s smartest man to change his mind. This meeting caused Einstein to call his previous calculations the biggest mistake of his scientific life, and as a result, Hubble’s findings became the center of attention in scientific circles.

Edwin Hubble in old age

In addition to scientific research, Edwin Hubble worked hard to convince the Nobel Prize Society to add astronomy to the award’s branches. He intended to add this science to this event as an independent subsection of physics. He believed that the efforts of astronomers in stellar physics should be appreciated. Unfortunately, after Hubble’s death, this society decided to appreciate this science as a branch of physics.

Personal life and death

In 1949, at the age of 59, Edwin Hubbell suffered a heart attack while on vacation in Colorado and was nursed back to health by his wife. Of course, after this incident, the intensity of his research activities decreased until he died on September 28, 1953, due to a blood clot in the brain. He had willed that his burial place should not be known and personal notes were also destroyed by his wife. Grace also died in 1980 and was buried in a secret place next to her husband.

Awards and honors

The Cleveland Newcomb Prize was awarded to Edwin Hubble in 1924. In 1938, he was awarded the Bruce Medal, and a year later, he was awarded the Franklin Medal Science and Engineering Award by the Franklin Institute in Philadelphia. The Gold Medal of the British Royal Astronomical Society was awarded to this legendary astronomer in 1940. The Legion of Honor, which is a military award from the US Armed Forces, was awarded to him in 1946 for his research in the field of ballistics.

Hubble Space Telescope

Asteroid number 2069 and a hole in the moon are among the celestial objects that are registered in the name of this scientist. A planetarium at Edward R. Morrow High School in Brooklyn was also named after this scientist, and a street in Missouri was named after Edwin Hubble.

Certainly, the most famous monument of Edwin Hubble is the Hubble Space Telescope, which was launched in 1990. The main purpose of launching this telescope was to accurately calculate Hubble’s constant in his famous formula. Anyway, astronomers with this telescope first considered the number 72 as a constant in 2001, and then in 2006, by studying the microwave background of the galaxy, they reached the exact number 70. In addition, the Hubble telescope made it possible to observe not only the expansion of the universe but also the acceleration of this expansion. Today, the force that caused this expansion is called dark energy in scientific documents.

Isn’t that the Zoom? No; Because zooming in only makes everything bigger. This can be easily illustrated with the following image: zoom in as much as you want on the image, but once you pass a certain limit, you only enlarge the pixels and get no new information. To overcome this obstacle, you need to have high resolution rather than zoom.

The problem is that resolution depends on the telescope itself, meaning that a dramatic increase in resolution usually requires a much larger telescope; But no matter how big your telescope gets, it will still have limited resolution.

When light from an infinitesimal point, such as distant stars, passes through a telescope, the light is slightly scattered within the telescope’s optical instruments (mirrors or lenses). This fundamental property is called light diffraction and is unavoidable. The resolution of telescope images depends partly on the size of its mirror or lens. The larger the telescope’s light-gathering instrument, the higher its image resolution.

The way light propagates in optical equipment depends on wavelength, with shorter wavelengths producing higher resolution. So two nearby blue stars may be distinguishable in a telescope, while two red stars at the same distance may not be distinguishable.

When deciding on the size of a telescope’s camera pixels, astronomers must consider the wavelength they want to observe. Otherwise, they just magnify the noise; Like the previous example about zooming too much on the photo.

All these lead to an amazing result. The Hubble Space Telescope has a mirror with a diameter of 2.4 meters and the James Webb Space Telescope (JWST) has a mirror with a diameter of 6.5 meters. Therefore, the resolution of the James Webb telescope images can be expected to be much higher. At some wavelengths, it is: the shortest wavelength that the James Webb Space Telescope can see is about 0.6 microns (what our eyes perceive as orange light), and the resolution is technically much better than that of the Hubble image.

However, the James Webb Space Telescope was designed as an infrared telescope. At those wavelengths, say around two microns, the resolution is comparable to what Hubble can see at visible light wavelengths. In the mid-infrared, i.e. wavelengths of 10 to 20 microns, the resolution of the James Webb Space Telescope images is even lower. However, because the James Webb is the largest infrared telescope ever sent into space, it can provide the sharpest images we’ve ever had at these wavelengths.

Astronomers measure resolving power as an angle on the sky. From the horizon to the highest point of the sky is 90 degrees and each degree is divided into 60 arc minutes and each arc minute into 60 arc seconds. For example, the angular diameter of the moon from our point of view in the sky is about half a degree. That is, if we look at the moon from the Earth, the moon in the sky occupies a space equal to half a degree of the full circle of the sky, which is equivalent to 30 minutes of arc or 1800 seconds of arc.

The maximum resolution of a telescope refers to the smallest angular distance between two objects that the telescope is able to distinguish as two separate objects. This resolution is expressed as an angle.

At its best, the resolution of the Hubble telescope is about 0.05 of an arc, which is considered a very small angle. But the amount of detail Hubble is able to see depends on the distance and physical size of the target. For example, 0.05 seconds of arc is equivalent to the apparent size of a small coin that can be seen from about 140 km.

In this way, we return to the discussion of conspiracy theorists and their claims regarding the observation of astronaut footprints on the moon. Galaxies are usually tens of millions or even billions of light years away from Earth. At those distances, the Hubble telescope can distinguish objects with dimensions of several light years (i.e. tens of trillions of kilometers) with its best resolution. So even though it looks like we’re seeing galaxies in great detail in those amazing Hubble images, the smallest we can see is still pretty big.

At the same time, the moon is only about 380 thousand kilometers away from us and from the Hubble telescope. At this distance, the resolution of the Hubble telescope is surprisingly limited, unable to resolve objects smaller than about 90 meters. As a result, not only can we not see the astronauts’ footprints in the Hubble images, but we can’t even see the Apollo moon landings, which are about four meters across. Hubble’s resolution at this distance is so limited that it cannot distinguish details smaller than about 90 meters, so it is not possible to see objects smaller than this on the Moon.

In the images taken by the Nass Lunar Reconnaissance Orbiter (LRO), we can see the moon landings and the footprints of the astronauts. Although the camera of this orbiter has a mirror with a diameter of only about 20 cm, the spacecraft is in lunar orbit and passes the Apollo landing sites at an altitude of 50 km.

You’ve probably heard the story that the Apollo astronauts could see the Great Wall of China from the moon. This claim sounds funny from a scientific point of view, but why can’t it be true?

The important issue is resolution. Astronomers usually use this term for the ability to separate two space objects that are at a close distance from each other, and sometimes you may see them as a merged point. You probably had this experience too: while driving at night on the highway, you see the lights of the cars as a single light source until the car approaches you and you realize that you are actually seeing two lights.

Resolution is usually expressed in terms of an angle, which is measured based on the size of the object and its distance from the observer. For example, the diameter of the moon is approximately 3,500 km and it is 380,000 km away from the Earth; By doing calculations, you will find that the moon has an apparent width of 0.5 degrees.

The average human eye has a resolution of approximately one minute of arc (there are 60 minutes of arc in one degree). A person with very strong vision can distinguish an object half this size. The moon is bigger than this example, so it is seen as a disk, and its features can be easily seen.

But what about the Great Wall of China? This wall is very narrow despite its long length. One of the widest parts of this wall reaches 10 meters. Can something this big be seen from the moon?

The Great Wall of China appears from the moon as a line with a thickness of one-thousandth of an arc minute. Recognizing such a structure from the moon is like trying to see a strand of human hair from a distance of one kilometer with the naked eye; So you probably agree that it is impossible to see the Great Wall of China from the moon.

However, let’s manipulate the above claim a bit: Suppose we are in low-Earth orbit and we are seeing our planet from the International Space Station (ISS). This station is located 400 km above the Earth’s surface, so the Great Wall of China appears from there with a width of 0.1 arc minutes. Even so, it is too small to see with the naked eye.

However, there is still a chance. The human eye can well recognize narrow and long objects that have a high contrast with their surroundings. For example, astronauts stationed in Earth orbit can see roads in the middle of the desert and traces of ocean-going ships. Does this observation help? Unfortunately no. The Great Wall of China is made of stones that do not contrast well with the ground and also have a curved shape depending on the landscape, especially near cliffs and hills.

Of course, under certain conditions, the Chinese wall can be seen from orbit. At sunrise or sunset, when the sun is at the lowest point in the sky, the Chinese wall can create a long shadow; But again, this is not the same as seeing the wall itself.

But what can be said about other man-made objects? The Great Wall of China is long, but there are definitely other bigger structures. Egyptian pyramids are other obvious candidates. The Great Pyramid of Giza has an approximate diameter of 230 meters at the base, and thus it is large enough to be seen from low Earth orbit.

On the one hand, the dusty pyramid of Giza does not have much contrast with the sand around it, but the contrast can be reached from the light of the structure itself: in the low angles of the sun, half of the pyramid is lit and the other half is in the shadow, thus distinguishing it from a sandy landscape. It becomes possible. Leroy Xiao, a former NASA astronaut, claims to have seen two Egyptian pyramids and tried to see the other one, but failed.

According to NASA, the Three Gorges Dam in China can be seen from space. So far, there have been no reports of astronauts actually seeing it, but it is possible. This dam is huge. It is more than 100 meters wide at the base and its length reaches 2.3 kilometers. The light brown color of this dam appears next to the blue waters of the Yangtze River in the telephoto images of the astronauts.

It should be noted that you don’t necessarily need to separate an object to see it. Stars are good examples. Although they are very large and the diameter of some of them reaches millions of kilometers, they are remarkably far away; Even the nearest star (except the sun) is 40 trillion kilometers away from us. If there is enough light, even an object with low resolution can be seen.