Through out the history of China, people are curious about how Sun, Moon and stars move according to Earth, and astronomers have created different tools to assist observing stars.
Armillary Sphere
The earliest well-known tool is Armillary Sphere (Chinese: 浑天仪), which is designed by Zhang Heng in 117 AD and completed in 125 AD. An Armillary Sphere is a spherical model of object in the sky, with Earth centered in the middle of the sphere. (At that time, Chinese people still believe in geocentric.) The spherical model contains multiple rings and each ring is movable. Different ring represent different solar objects – the 28 Mansions (28 important constellations in Chinese Myth), north/south pole, the equator, the ecliptic, the 24 Solar Terms (Chinese: 节气). There are two water clock in the Armillary Sphere. In the bottom of each water clock, there is a hole. As water leaking from the hole, the Armillary Sphere will gradually move by itself.
According to the Science Civilizations in China, the emergence and improvement of Horologe happened both in Eastern and Western at almost the same time. However, there is some difference between the Horologes made by the east and by the west. The horologes designed by the Western Countries are Vertical Sundial and Flat Sundial. On the other hand, the horologes designed by China are the Equatorial Sundial. Although each type of sundials has its own advantage, Joseph Needham mentioned in Science Civilization in China that Equatorial Sundial has always been the most accurate one.
The rise and fall of tides produces a renewable energy source called Tidal energy. Originally, at the beginning of the 20th century engineers began to use spring tides to generate electricity because of the dramatic change in water levels. While tidal energy has grown in the past century, it is still at the beginning of its age. So far, tidal energy has only produced a small output of energy, but with more research and with the development of more intricate generators, there is a possibility of increasing energy output. The first tidal power plant was in La Rance, France. The United States still does not have any tidal power plants because we don’t experience dramatic spring tides like other areas of the world.
Generators currently use the rate of the flow of water to generate electricity. Tidal energy is shown to generate more electricity than wind energy because water is denser than wind. Tides are also easier to predict than the occurrence of winds, which makes it a more reliable source of energy. Presently, more research and experimentation need to take place to further develop technology to generate electricity from tides.
Ever since Edwin Hubble’s groundbreaking observations, it has been known that the universe is expanding. According to his observations, galaxies farther away from us are moving faster than objects closer to us (at least in terms of relative velocities). However, according to more recent studies, the Milky Way and other galaxies near us seem to be moving towards a central point. Nicknamed the “Great Attractor,” this point in space must have a mass thousands of times greater than the Milky Way in order to produce the gravitational forces that we have measured.
The Great Attractor was first noticed when astronomers measured the velocities of galaxies close to the Milky Way. While all of these galaxies are moving away from us- in accordance to Hubble’s ideas- but many of these galaxies had velocities that did not match with the estimates given to us by Hubble’s Law. These “Peculiar Velocities” told astronomers that there must be something with enough mass to pull galaxies away from their natural paths, and thus the idea of the Great Attractor was born. The biggest problem currently facing astronomers with regard to the Great Attractor is that it’s almost impossible to see. It lies in an area of space known as the Zone of Avoidance: the area of space that is made invisible by the large dust clouds located inside the disk of the Milky Way. This makes direct observation of the Great Attractor almost impossible. Therefore, the actual mass of the Great Attractor is highly debated. Some astronomers believe the newly discovered Vela Supercluster contains enough mass to cause the gravitational forces attributed to the Great Attractor, others claim that much more undiscovered mass is needed to explain the shift. Either way, the idea that there is enough concentrated mass in the universe to shift the movements of galaxies is a truly awe-inspiring idea.
A picture of the area of space that the Great Attractor lies in Source
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Ever since Edwin Hubble’s groundbreaking observations, it has been known that the universe is expanding. According to his observations, galaxies farther away from us are moving faster than objects closer to us (at least in terms of relative velocities). However, according to more recent studies, the Milky Way and other galaxies near us seem to be moving towards a central point. Nicknamed the “Great Attractor,” this point in space must have a mass thousands of times greater than the Milky Way in order to produce the gravitational forces that we have measured.
The Great Attractor was first noticed when astronomers measured the velocities of galaxies close to the Milky Way. While all of these galaxies are moving away from us- in accordance to Hubble’s ideas- but many of these galaxies had velocities that did not match with the estimates given to us by Hubble’s Law. These “Peculiar Velocities” told astronomers that there must be something with enough mass to pull galaxies away from their natural paths, and thus the idea of the Great Attractor was born. The biggest problem currently facing astronomers with regard to the Great Attractor is that it’s almost impossible to see. It lies in an area of space known as the Zone of Avoidance: the area of space that is made invisible by the large dust clouds located inside the disk of the Milky Way. This makes direct observation of the Great Attractor almost impossible. Therefore, the actual mass of the Great Attractor is highly debated. Some astronomers believe the newly discovered Vela Supercluster contains enough mass to cause the gravitational forces attributed to the Great Attractor, others claim that much more undiscovered mass is needed to explain the shift. Either way, the idea that there is enough concentrated mass in the universe to shift the movements of galaxies is a truly awe-inspiring idea.
A picture of the area of space that the Great Attractor lies in Source
Posted inGalaxies|Taggedastro2110, blog3|Comments Off on Blog Post #3: The Great Attractor
For centuries astronomers have used telescopes to look into the night sky. In 1946 Lyman Spitzer, a prominent astrophysicist in his time, theorized that a telescope placed outside of Earth’s atmosphere would be able to collect much clearer data than telescopes on the surface of the planet. The logic behind his theory is that the atmosphere blocks many wavelengths of light, thus limiting what data earth-based telescopes can collect. Although the idea seemed outlandish at the time given their level of technology, Spitzer never lost faith and kept promoting the idea of space telescopes until technology caught up to his dreams. It took over 20 years for Spitzer’s dream of a space telescope to become reality, with the first American space telescope being completed in 1968.
Formally titled the James Webb Space Telescope, it is named in honor of James E. Webb, the administrator of NASA who oversaw the United States’ first manned missions outside our atmosphere. The primary mirror onboard is over 6.5 meters (or just over 21 feet) in diameter. With a projected launch date of spring 2019, JWST will be launched into an orbit of the Sun (not the Earth) about 1.5 million kilometers away from Earth’s surface. The goal of JWST is to provide astronomers with information they were previously unable to collect. The instruments onboard are so sensitive that they could sense the heat of a bumblebee if it were on the surface of the moon, and its picture will be so sharp you could make out the details of a penny from over 20 miles away. These instruments will be pointed at very faint galaxies in order to compare them to newer, brighter galaxies which will hopefully allow astronomers to learn how galaxies form. JWST will look at exoplanets and analyze their atmospheres in the hope of finding evidence of life on other planets. Finally, JWST will analyze infrared light in the universe to try and better understand what was happening at the very beginning of the universe. JWST represents a new age in astronomy: an age of extreme precision and unprecedented vision. Regardless of what JWST will find, astronomers around the globe are eagerly awaiting those first few pictures we will receive from the James Webb Space Telescope.
For centuries astronomers have used telescopes to look into the night sky. In 1946 Lyman Spitzer, a prominent astrophysicist in his time, theorized that a telescope placed outside of Earth’s atmosphere would be able to collect much clearer data than telescopes on the surface of the planet. The logic behind his theory is that the atmosphere blocks many wavelengths of light, thus limiting what data earth-based telescopes can collect. Although the idea seemed outlandish at the time given their level of technology, Spitzer never lost faith and kept promoting the idea of space telescopes until technology caught up to his dreams. It took over 20 years for Spitzer’s dream of a space telescope to become reality, with the first American space telescope being completed in 1968.
Formally titled the James Webb Space Telescope, it is named in honor of James E. Webb, the administrator of NASA who oversaw the United States’ first manned missions outside our atmosphere. The primary mirror onboard is over 6.5 meters (or just over 21 feet) in diameter. With a projected launch date of spring 2019, JWST will be launched into an orbit of the Sun (not the Earth) about 1.5 million kilometers away from Earth’s surface. The goal of JWST is to provide astronomers with information they were previously unable to collect. The instruments onboard are so sensitive that they could sense the heat of a bumblebee if it were on the surface of the moon, and its picture will be so sharp you could make out the details of a penny from over 20 miles away. These instruments will be pointed at very faint galaxies in order to compare them to newer, brighter galaxies which will hopefully allow astronomers to learn how galaxies form. JWST will look at exoplanets and analyze their atmospheres in the hope of finding evidence of life on other planets. Finally, JWST will analyze infrared light in the universe to try and better understand what was happening at the very beginning of the universe. JWST represents a new age in astronomy: an age of extreme precision and unprecedented vision. Regardless of what JWST will find, astronomers around the globe are eagerly awaiting those first few pictures we will receive from the James Webb Space Telescope.
A gravitational lens is an observed image of light that is bent into a circle around the gravitational objects. The general relativity theory or the curvature of the space time is used to explain this amazing phenomena. When there is a sufficiently large gravitational objects such as stars, black holes and celestial bodies in the light’s trail, the light bends around the mass and forms a circular ring. This formation of a circular ring is called the gravitational lensing or an Einstein’s ring.
There are 3 different types of such gravitational lensing. First of all is the strong lensing of light that occurs when the distortions of the light can easily be distinguished in forms of Einstein rings, arcs and others. Secondly, there is weak lensing, which occurs when the center of the mass is much smaller to create only hardly detectable gravitational lensing that must be analyzed from many different angles and sources to be deemed as gravitational lensing. Lastly, there is micro-lensing, where there is no visible light distortion, but the amount of light changes in time.
Regardless the type of the gravitational lensing, all types of electromagnetic radiation is affected due to the curvature of the space time created by the mass. Therefore, the analysis of the gravitational lensing is widely used in practice. For example, micro lensing is used to find extra-solar planets. Also, weak-lensing analysis is used to moderate the map of dark matter and the shape of galaxies. Not only does the image of the gravitational lens look interesting, but also the conclusions and data we can draw out from the gravitational lens help us understand more about the space we did not know before.
A gravitational lens is an observed image of light that is bent into a circle around the gravitational objects. The general relativity theory or the curvature of the space time is used to explain this amazing phenomena. When there is a sufficiently large gravitational objects such as stars, black holes and celestial bodies in the light’s trail, the light bends around the mass and forms a circular ring. This formation of a circular ring is called the gravitational lensing or an Einstein’s ring.
There are 3 different types of such gravitational lensing. First of all is the strong lensing of light that occurs when the distortions of the light can easily be distinguished in forms of Einstein rings, arcs and others. Secondly, there is weak lensing, which occurs when the center of the mass is much smaller to create only hardly detectable gravitational lensing that must be analyzed from many different angles and sources to be deemed as gravitational lensing. Lastly, there is micro-lensing, where there is no visible light distortion, but the amount of light changes in time.
Regardless the type of the gravitational lensing, all types of electromagnetic radiation is affected due to the curvature of the space time created by the mass. Therefore, the analysis of the gravitational lensing is widely used in practice. For example, micro lensing is used to find extra-solar planets. Also, weak-lensing analysis is used to moderate the map of dark matter and the shape of galaxies. Not only does the image of the gravitational lens look interesting, but also the conclusions and data we can draw out from the gravitational lens help us understand more about the space we did not know before.
In many different scientific, astronomical movies, different planets than Earth are often portrayed as hardly habitable environments with almost impenetrable, dusty atmosphere. The atmospheres of these planets seem to vary a lot in many aspects such as density, and components. Among all 8 planets, including Earth in the solar system, the atmospheric conditions of each are interesting as they are very different from one another. The planets are divided into 2 groups, one is the inner planet with the inner-most 4 and the other is gas giants with the outer-most 4.
Staring from the inner most planet, Mercury does not have considerable atmosphere. Because Mercury’s mass is small and so is the gravitational force to hold onto elements to form atmosphere. The elements of this thin layer of gas on Mercury’s surface are sodium, helium, potassium and oxygen caused by the solar wind, radioactive decay, meter impacts and the breakdown of Mercury’s crust. Thus the condition changes over time as these elements escapes due to Mercury’s heat. Following Mercury, Venus has its atmosphere mainly filled with carbon dioxide. Venus’s atmosphere is much denser and hotter than Earth’s, but it does not have any stratosphere within. The dense amount of carbon dioxide in the atmosphere creates a green house effect, making the surface temperature really hot. Mars has very thin atmosphere, composed of carbon dioxide and some nitrogen and argon. Because the atmosphere is very thin, Mars’s surface temperature is subject to a high variation from about -220 F at the lowest to 70 F, the highest.
The outer most 4 planets are called gas giants because they share some common characteristics in their atmospheres. The atmospheres contain mainly hydrogen and helium and there are no clear boundaries between the body and the atmosphere as hydrogen and helium turns into liquid interior. The first member of the gas giants, Jupiter has its upper part of the atmosphere of 75% hydrogen and 24% helium with 1% of other elements. Jupiter’s inner part is roughly the similar combination of hydrogen and helium with some heavier elements. The atmosphere on Jupiter is very unstable and the circulation of the gases create storms and disturbance. There is one very famous storm, called the Great Red Spot that is persistently anticyclonic and is larger than Earth in size. The second member is Saturn. Saturn’s outer atmosphere has higher hydrogen density and lower helium density than Jupiter. Even though Saturn is very much similar to Jupiter’s atmosphere as it has persistent storms and the liquid interior, one most distinct feature of Saturn’s atmosphere is that it has the fastest winds among all the planets in the solar system. The fastest wind speed recorded by Voyager is 500 m/s. Uranus shares the similar combination of hydrogen and helium as main components of its atmosphere. However, it has very low temperatures and thus relatively stable atmospheric conditions with much fewer storm formations. Lastly, Neptune has very similar atmospheric conditions like Uranus with more activity such as storms, high speed winds and cyclonic clouds.
Upon looking at all 8 planets and their atmospheric conditions, it seems that the greater mass it is, the thicker atmosphere it has due to the gravitational force to hold more gas near the surface level. It is interesting to note that all the planets vary greatly in their atmospheric conditions even if some share similar components and characteristics. For planets beyond the solar system, it would be interesting to look at their atmospheres and their elemental compositions to compare those with ours.
In many different scientific, astronomical movies, different planets than Earth are often portrayed as hardly habitable environments with almost impenetrable, dusty atmosphere. The atmospheres of these planets seem to vary a lot in many aspects such as density, and components. Among all 8 planets, including Earth in the solar system, the atmospheric conditions of each are interesting as they are very different from one another. The planets are divided into 2 groups, one is the inner planet with the inner-most 4 and the other is gas giants with the outer-most 4.
Staring from the inner most planet, Mercury does not have considerable atmosphere. Because Mercury’s mass is small and so is the gravitational force to hold onto elements to form atmosphere. The elements of this thin layer of gas on Mercury’s surface are sodium, helium, potassium and oxygen caused by the solar wind, radioactive decay, meter impacts and the breakdown of Mercury’s crust. Thus the condition changes over time as these elements escapes due to Mercury’s heat. Following Mercury, Venus has its atmosphere mainly filled with carbon dioxide. Venus’s atmosphere is much denser and hotter than Earth’s, but it does not have any stratosphere within. The dense amount of carbon dioxide in the atmosphere creates a green house effect, making the surface temperature really hot. Mars has very thin atmosphere, composed of carbon dioxide and some nitrogen and argon. Because the atmosphere is very thin, Mars’s surface temperature is subject to a high variation from about -220 F at the lowest to 70 F, the highest.
The outer most 4 planets are called gas giants because they share some common characteristics in their atmospheres. The atmospheres contain mainly hydrogen and helium and there are no clear boundaries between the body and the atmosphere as hydrogen and helium turns into liquid interior. The first member of the gas giants, Jupiter has its upper part of the atmosphere of 75% hydrogen and 24% helium with 1% of other elements. Jupiter’s inner part is roughly the similar combination of hydrogen and helium with some heavier elements. The atmosphere on Jupiter is very unstable and the circulation of the gases create storms and disturbance. There is one very famous storm, called the Great Red Spot that is persistently anticyclonic and is larger than Earth in size. The second member is Saturn. Saturn’s outer atmosphere has higher hydrogen density and lower helium density than Jupiter. Even though Saturn is very much similar to Jupiter’s atmosphere as it has persistent storms and the liquid interior, one most distinct feature of Saturn’s atmosphere is that it has the fastest winds among all the planets in the solar system. The fastest wind speed recorded by Voyager is 500 m/s. Uranus shares the similar combination of hydrogen and helium as main components of its atmosphere. However, it has very low temperatures and thus relatively stable atmospheric conditions with much fewer storm formations. Lastly, Neptune has very similar atmospheric conditions like Uranus with more activity such as storms, high speed winds and cyclonic clouds.
Upon looking at all 8 planets and their atmospheric conditions, it seems that the greater mass it is, the thicker atmosphere it has due to the gravitational force to hold more gas near the surface level. It is interesting to note that all the planets vary greatly in their atmospheric conditions even if some share similar components and characteristics. For planets beyond the solar system, it would be interesting to look at their atmospheres and their elemental compositions to compare those with ours.
