Gravitational Lensing
" Gravitational lensing refers to a distribution of matter between a distant source and an observer, that is capable of bending the light from the source, as it travels towards the observer." "Gravitational lensing is when light bends after it moves from one medium to another." Since light follows the curvature of space-time, when light bends around a massive object light bends. So massive objects serve as mirrors reflecting the images of anything which light has been bent.
For instance, the light emmitted by stars bends around the sun and is thus-forth reflected to the earth. So stars are not actually where humans physically view them outside.
This image shows the bending of starlight by the sun. "The arrows show the paths of light rays and the dashed stars show the apparent position of the stars as seen from Earth. "
Another example is the emission of light by quasar in the universe. The Earth will have no problem viewing this Quasar if it is directly in front of it. However, if a galaxy or an extremely large object is blocking the Quasar, the light emitted by the Quasar will be bent by gravitational field around the object. The gravitational bending of the light emitted by the Quasar will transmit not only one but multiple images of the Quasar into space. There, the Quasar is viewable from different areas of the universe.
This is diagram above depicts gravitational lensing for a Quasar.
This is a picture of gravitational lensing from the Hubble Space Telescope.
Thus forth, Einstein was correct in 1905 when he concluded that light is bent when traveling over time. Light is bent by large clumps of matter along the path in which it is emitted. As he concluded, gravity is a curvature of space and time. "Long ago Einstein recognized the potential existence of gravitational lensing, a consequence of his theory of general relativity. According to general relativity, celestial objects create dimples in space-time that bend the light traveling from behind."
To top it all off, a group of scientists led by Arthur Eddington traveled to West Africa in order to view the positions of the stars in solar eclipses. Their results align with Einstein's theory of relativity. "The stars did appear to be slightly moved relative to their nighttime positions in exactly the way predicted by GR. This observation was the first crucial test of Einstein's theory."
http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/gr1.html
http://imagine.gsfc.nasa.gov/docs/features/news/grav_lens.html
http://en.wikipedia.org/wiki/Gravitational_lens
http://www.space.com/1032-universe-einsteins-glasses.html
http://www.sciencedaily.com/releases/2009/02/090220172053.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/redshf.html
http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/gr1.html
http://imagine.gsfc.nasa.gov/docs/features/news/grav_lens.html
http://en.wikipedia.org/wiki/Gravitational_lens
http://www.space.com/1032-universe-einsteins-glasses.html
http://www.sciencedaily.com/releases/2009/02/090220172053.htm
The Red Shift of Light
"In physics (especially astrophysics), redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum."
The Red Shift process has to do with the color spectra. Accordingly, distant stars and galaxies emit light that has distinct spectral characteristics which coincide with the properties of the atoms in the gas around the stars. When these spectra are examined, they are found to be towards the red end of the spectrum. The shift in the color spectrum is a Doppler Shift. This emphasizes that galaxies are growing and moving away from the earth and the sun. This led Edwin Hubble to conclude that Red Shift is proportional to distance (Hubble' Law). When an object is moving away from an observer, its wavelengths of light are elongated and therefore record-able. If the object is coming towards you, it is known as blue shift; if it traveling away from you, it is known as red shift.
Redshifts are "a shift in the frequency of a photon toward lower energy, or longer wavelength. The redshift is defined as the change in the wavelength of the light divided by the rest wavelength of the light, as z = (Observed wavelength - Rest wavelength)/(Rest wavelength)"
There are three main types of redshifts.
Doppler Red Shift: This is the result of the motion of the light emitting object and the observer himself. If the source of light is moving away from the observer, the light is stretched out and shifted toward the red. This is given by the formula (Observed wavelength - Rest wavelength)/(Rest wavelength) = (v/c).
Cosmological Redshift: This Redshift is caused by the expansion of space. "The wavelength of light increases as it traverses the expanding universe between its point of emission and its point of detection by the same amount that space has expanded during the crossing time."
Gravitational Redshift: This is caused when a photon shifts in frequency to a lower energy when it climbs out of a gravitational field.
When in reference to the galaxy, the farther away a galaxy is, the faster it is moving. The higher the velocity at which it moves, the more redshift it releases. Astronomers are able to calculate the distance certain planet and galaxies are away from the earth by using red shift.
"The first of the classical tests discussed above, the gravitational redshift, is a simple consequence of the Einstein equivalence principle and was predicted by Einstein in 1907. As such, it is not a test of general relativity in the same way as the post-Newtonian tests, because any theory of gravity obeying the equivalence principle should also incorporate the gravitational redshift. Nonetheless, confirming the existence of the effect was an important substantiation of relativistic gravity, since the absence of gravitational redshift would have strongly contradicted relativity. The first observation of the gravitational redshift was the measurement of the shift in the spectral lines from the white dwarf star Sirius B by Adams in 1925. Although this measurement, as well as later measurements of the spectral shift on other white dwarf stars, agreed with the prediction of relativity, it could be argued that the shift could possibly stem from some other cause, and hence experimental verification using a known terrestrial source was preferable."
Red Shift was first proved scientifically in 1960 with an experiment that measured the change in wavelength of gamma-ray photons generated with the Mössbauer effect.
Einstein's theory of relativity is supported by the Red Shift. "To fully validate general relativity, it is important to also show that the rate of arrival of the photons is greater than the rate at which they are emitted. A very accurate gravitational redshift experiment, which deals with this issue, was performed in 1976,[34] where a hydrogen maser clock on a rocket was launched to a height of 10,000 km, and its rate compared with an identical clock on the ground. It tested the gravitational redshift to 0.007%."
http://en.wikipedia.org/wiki/Tests_of_general_relativity
Red Shift was first proved scientifically in 1960 with an experiment that measured the change in wavelength of gamma-ray photons generated with the Mössbauer effect.
Einstein's theory of relativity is supported by the Red Shift. "To fully validate general relativity, it is important to also show that the rate of arrival of the photons is greater than the rate at which they are emitted. A very accurate gravitational redshift experiment, which deals with this issue, was performed in 1976,[34] where a hydrogen maser clock on a rocket was launched to a height of 10,000 km, and its rate compared with an identical clock on the ground. It tested the gravitational redshift to 0.007%."
http://en.wikipedia.org/wiki/Tests_of_general_relativity
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/redshf.html
Black Holes
"A black hole is a region of space from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform space-time to form a black hole. Around a black hole there is an undetectable surface called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics.[1]Quantum mechanics predicts that black holes emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater."
In simpler words, a black hole is an area of space which has a gravitational field so intense that nothing can escape.
"A black hole is a region of space whose attractive gravitational force is so intense that no matter, light, or communication of any kind can escape. A black hole would thus appear black from the outside. (However, gas around a black hole can be very bright.) It is believed that black holes form from the collapse of stars. As long as they are emitting heat and light into space, stars are able to support themselves against their own inward gravity with the outward pressure generated by heat from nuclear reactions in their deep interiors."
Black holes are caused by Gravitational Collapse. A star or any other large space form reaches a very high critical density. At this high density, the stars gravity will cause it to collapse. In other words, the object's internal pressure is high enough to resists its own gravity. Black holes usually form when stars can no longer produce sufficient energy from its core which prevents the star from maintaining its own temperature.
Important properties of black holes:
This image depicts how no object can escape from an event horizon. The only motion an object travels once it reaches the event horizon is the center of the black hole.
Since black holes can not be seen, scientists have to rely on indirect evidence to prove their existence. Kormendy and Richstone discovered that 8 galaxies have large dark masses in their center. They think that these are black holes. "The masses of the cores of these galaxies range from one million to several billion times the mass of the Sun. The mass is measured by observing the speed with which stars and gas orbit around the center of the galaxy: the faster the orbital speeds, the stronger the gravitational force required to hold the stars and gas in their orbits." There are two reasons why they think these are black holes. First, there is nothing else that these beings could be. Secondly, the only thing to explain why large beings like quasars and galaxies exist is if they have black holes at their core.
Here is another example of proof. "A second discovery provides even more compelling evidence. X-ray astronomers have detected a spectral line from one galactic nucleus that indicates the presence of atoms near the nucleus that are moving extremely fast (about 1/3 the speed of light). Furthermore, the radiation from these atoms has been red shifted in just the manner one would expect for radiation coming from near the horizon of a black hole. These observations would be very difficult to explain in any other way besides a black hole, and if they are verified, then the hypothesis that some galaxies contain super-massive black holes at their centers would be fairly secure."
This coincides with Einstein's Theory of Relativity because he concluded that gravity influences light's motion. In a black hole, the gravitational collapse is so strong that not a single ray of light can escape from a black hole. Light is pushed towards the center and can not travel outward. Einstein actually believed that black holes are impossible to form. He proposed that the angular momentum of collapsing particles would stabilize their motion at some radius. It was not until Penrose and Steven Hawking that black holes were studied for serious functioning. They concluded that black holes do exist.
http://www.pbs.org/wgbh/nova/einstein/relativity/
http://science.nasa.gov/science-news/science-at-nasa/2001/ast12jan_1/
http://blackholes.stardate.org/resources/faqs/faq.php?p=black-hole-formation
http://en.wikipedia.org/wiki/Black_hole
http://cosmology.berkeley.edu/Education/BHfaq.html
http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/gr1.html
In simpler words, a black hole is an area of space which has a gravitational field so intense that nothing can escape.
"A black hole is a region of space whose attractive gravitational force is so intense that no matter, light, or communication of any kind can escape. A black hole would thus appear black from the outside. (However, gas around a black hole can be very bright.) It is believed that black holes form from the collapse of stars. As long as they are emitting heat and light into space, stars are able to support themselves against their own inward gravity with the outward pressure generated by heat from nuclear reactions in their deep interiors."
A probably black hole
Black holes are caused by Gravitational Collapse. A star or any other large space form reaches a very high critical density. At this high density, the stars gravity will cause it to collapse. In other words, the object's internal pressure is high enough to resists its own gravity. Black holes usually form when stars can no longer produce sufficient energy from its core which prevents the star from maintaining its own temperature.
Important properties of black holes:
- A massive object is in the center of black holes. This object is the source of the gravitational field. This object keeps collapsing and gets denser and denser. The object will keep collapsing until it reaches a point of infinite density called singularity.
- The object has a Schwarzschild radius. If anything gets squeezed into the radius of the object, it will also form another black hole. I will continue to shrink until it form singularity. "The Schwarzschild radius for an object of mass m is 2Gm/c2, where G is Newton's gravitational constant. For example the Earth, in order to become a black hole, would have to be squeezed into a sphere less than 5 mm across."
- The event horizon is also in a black hole. The event horizon is a sphere at the Schwarzschild radius. As the object inside the black collapses, it size remains constant. So the event horizon varies with the Schwarzschild radius.The event horizon is the place where light turn inwards. It is the point of no return.
This image depicts how no object can escape from an event horizon. The only motion an object travels once it reaches the event horizon is the center of the black hole.
"Gravity draws gas from a companion star onto a black hole in a swirling pattern. As the gas nears the event horizon, a strong gravitational red shift makes it appear redder and dimmer. When the gas finally crosses the event horizon, it disappears from view; the region within the event horizon appears black."
Evidence of black holes
Since black holes can not be seen, scientists have to rely on indirect evidence to prove their existence. Kormendy and Richstone discovered that 8 galaxies have large dark masses in their center. They think that these are black holes. "The masses of the cores of these galaxies range from one million to several billion times the mass of the Sun. The mass is measured by observing the speed with which stars and gas orbit around the center of the galaxy: the faster the orbital speeds, the stronger the gravitational force required to hold the stars and gas in their orbits." There are two reasons why they think these are black holes. First, there is nothing else that these beings could be. Secondly, the only thing to explain why large beings like quasars and galaxies exist is if they have black holes at their core.
Here is another example of proof. "A second discovery provides even more compelling evidence. X-ray astronomers have detected a spectral line from one galactic nucleus that indicates the presence of atoms near the nucleus that are moving extremely fast (about 1/3 the speed of light). Furthermore, the radiation from these atoms has been red shifted in just the manner one would expect for radiation coming from near the horizon of a black hole. These observations would be very difficult to explain in any other way besides a black hole, and if they are verified, then the hypothesis that some galaxies contain super-massive black holes at their centers would be fairly secure."
This coincides with Einstein's Theory of Relativity because he concluded that gravity influences light's motion. In a black hole, the gravitational collapse is so strong that not a single ray of light can escape from a black hole. Light is pushed towards the center and can not travel outward. Einstein actually believed that black holes are impossible to form. He proposed that the angular momentum of collapsing particles would stabilize their motion at some radius. It was not until Penrose and Steven Hawking that black holes were studied for serious functioning. They concluded that black holes do exist.
http://www.pbs.org/wgbh/nova/einstein/relativity/
http://science.nasa.gov/science-news/science-at-nasa/2001/ast12jan_1/
http://blackholes.stardate.org/resources/faqs/faq.php?p=black-hole-formation
http://en.wikipedia.org/wiki/Black_hole
http://cosmology.berkeley.edu/Education/BHfaq.html
http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/gr1.html
No comments:
Post a Comment