Universal Laws of Heavenly Bodies
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Good question Grandpa!
For the most part the speed of light is a constant but it can be altered with gravity if the gravitational force is strong enough I.E. black holes etc.
Distance measurement
Radar systems measure the distance to a target by the time it takes a radio-wave pulse to return to the radar antenna after being reflected by the target: the distance to the target is half the round-trip transit time multiplied by the speed of light. A Global Positioning System (GPS) receiver measures its distance to GPS satellites based on how long it takes for a radio signal to arrive from each satellite, and from these distances calculates the receiver's position. Because light travels about 300,000 kilometres (186,000 miles) in one second, these measurements of small fractions of a second must be very precise. The Lunar Laser Ranging Experiment, radar astronomy and the Deep Space Network determine distances to the Moon,[73] planets[74] and spacecraft,[75] respectively, by measuring round-trip transit times
Astronomy
The finite speed of light is important in astronomy. Due to the vast distances involved, it can take a very long time for light to travel from its source to Earth. For example, it has taken 13 billion (13×109) years for light to travel to Earth from the faraway galaxies viewed in the Hubble Ultra Deep Field images.[76][77] Those photographs, taken today, capture images of the galaxies as they appeared 13 billion years ago, when the universe was less than a billion years old.[76] The fact that more distant objects appear to be younger, due to the finite speed of light, allows astronomers to infer the evolution of stars, of galaxies, and of the universe itself.
Astronomical distances are sometimes expressed in light-years, especially in popular science publications and media.[78] A light-year is the distance light travels in one year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away.[79]
Measurement
There are different ways to determine the value of c. One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. However, it is also possible to determine c from other physical laws where it appears, for example, by determining the values of the electromagnetic constants ε0 and μ0 and using their relation to c. Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam, with their product equaling c.
In 1983 the metre was defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second",[80] fixing the value of the speed of light at 299,792,458 m/s by definition, as described below. Consequently, accurate measurements of the speed of light yield an accurate realization of the metre rather than an accurate value of c.
Astronomical measurements
Outer space is a natural setting for measuring the speed of light because of its large scale and nearly perfect vacuum. Typically, one measures the time needed for light to traverse some reference distance in the solar system, such as the radius of the Earth's orbit. Historically, such measurements could be made fairly accurately, compared to how accurately the length of the reference distance is known in Earth-based units. It is customary to express the results in astronomical units (AU) per day. An astronomical unit is approximately the average distance between the Earth and Sun; it is not based on the International System of Units.[Note 7] Because the AU determines an actual length, and is not based upon time-of-flight like the SI units, modern measurements of the speed of light in astronomical units per day can be compared with the defined value of c in the International System of Units.
Ole Christensen Rømer used an astronomical measurement to make the first quantitative estimate of the speed of light.[83][84] When measured from Earth, the periods of moons orbiting a distant planet are shorter when the Earth is approaching the planet than when the Earth is receding from it. The distance travelled by light from the planet (or its moon) to Earth is shorter when the Earth is at the point in its orbit that is closest to its planet than when the Earth is at the farthest point in its orbit, the difference in distance being the diameter of the Earth's orbit around the Sun. The observed change in the moon's orbital period is actually the difference in the time it takes light to traverse the shorter or longer distance. Rømer observed this effect for Jupiter's innermost moon Io and deduced that light takes 22 minutes to cross the diameter of the Earth's orbit.
Aberration of light: light from a distant source appears to be from a different location for a moving telescope due to the finite speed of light.
Another method is to use the aberration of light, discovered and explained by James Bradley in the 18th century.[85] This effect results from the vector addition of the velocity of light arriving from a distant source (such as a star) and the velocity of its observer (see diagram on the right). A moving observer thus sees the light coming from a slightly different direction and consequently sees the source at a position shifted from its original position. Since the direction of the Earth's velocity changes continuously as the Earth orbits the Sun, this effect causes the apparent position of stars to move around. From the angular difference in the position of stars (maximally 20.5 arcseconds)[86] it is possible to express the speed of light in terms of the Earth's velocity around the Sun, which with the known length of a year can be easily converted to the time needed to travel from the Sun to the Earth. In 1729, Bradley used this method to derive that light travelled 10,210 times faster than the Earth in its orbit (the modern figure is 10,066 times faster) or, equivalently, that it would take light 8 minutes 12 seconds to travel from the Sun to the Earth.[85]
Nowadays, the "light time for unit distance"—the inverse of c, expressed in seconds per astronomical unit—is measured by comparing the time for radio signals to reach different spacecraft in the Solar System, with their position calculated from the gravitational effects of the Sun and various planets. By combining many such measurements, a best fit value for the light time per unit distance is obtained. As of 2009[update], the best estimate, as approved by the International Astronomical Union (IAU), is:[87][88]
light time for unit distance: 499.004783836(10) sc = 0.00200398880410(4) AU/s = 173.144632674(3) AU/day.The relative uncertainty in these measurements is 0.02 parts per billion (2×10−11), equivalent to the uncertainty in Earth-based measurements of length by interferometry.[89][Note 8] Since the metre is defined to be the length travelled by light in a certain time interval, the measurement of the light time for unit distance can also be interpreted as measuring the length of an AU in metres.
For the most part the speed of light is a constant but it can be altered with gravity if the gravitational force is strong enough I.E. black holes etc.
Distance measurement
Radar systems measure the distance to a target by the time it takes a radio-wave pulse to return to the radar antenna after being reflected by the target: the distance to the target is half the round-trip transit time multiplied by the speed of light. A Global Positioning System (GPS) receiver measures its distance to GPS satellites based on how long it takes for a radio signal to arrive from each satellite, and from these distances calculates the receiver's position. Because light travels about 300,000 kilometres (186,000 miles) in one second, these measurements of small fractions of a second must be very precise. The Lunar Laser Ranging Experiment, radar astronomy and the Deep Space Network determine distances to the Moon,[73] planets[74] and spacecraft,[75] respectively, by measuring round-trip transit times
Astronomy
The finite speed of light is important in astronomy. Due to the vast distances involved, it can take a very long time for light to travel from its source to Earth. For example, it has taken 13 billion (13×109) years for light to travel to Earth from the faraway galaxies viewed in the Hubble Ultra Deep Field images.[76][77] Those photographs, taken today, capture images of the galaxies as they appeared 13 billion years ago, when the universe was less than a billion years old.[76] The fact that more distant objects appear to be younger, due to the finite speed of light, allows astronomers to infer the evolution of stars, of galaxies, and of the universe itself.
Astronomical distances are sometimes expressed in light-years, especially in popular science publications and media.[78] A light-year is the distance light travels in one year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away.[79]
Measurement
There are different ways to determine the value of c. One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. However, it is also possible to determine c from other physical laws where it appears, for example, by determining the values of the electromagnetic constants ε0 and μ0 and using their relation to c. Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam, with their product equaling c.
In 1983 the metre was defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second",[80] fixing the value of the speed of light at 299,792,458 m/s by definition, as described below. Consequently, accurate measurements of the speed of light yield an accurate realization of the metre rather than an accurate value of c.
Astronomical measurements
Outer space is a natural setting for measuring the speed of light because of its large scale and nearly perfect vacuum. Typically, one measures the time needed for light to traverse some reference distance in the solar system, such as the radius of the Earth's orbit. Historically, such measurements could be made fairly accurately, compared to how accurately the length of the reference distance is known in Earth-based units. It is customary to express the results in astronomical units (AU) per day. An astronomical unit is approximately the average distance between the Earth and Sun; it is not based on the International System of Units.[Note 7] Because the AU determines an actual length, and is not based upon time-of-flight like the SI units, modern measurements of the speed of light in astronomical units per day can be compared with the defined value of c in the International System of Units.
Ole Christensen Rømer used an astronomical measurement to make the first quantitative estimate of the speed of light.[83][84] When measured from Earth, the periods of moons orbiting a distant planet are shorter when the Earth is approaching the planet than when the Earth is receding from it. The distance travelled by light from the planet (or its moon) to Earth is shorter when the Earth is at the point in its orbit that is closest to its planet than when the Earth is at the farthest point in its orbit, the difference in distance being the diameter of the Earth's orbit around the Sun. The observed change in the moon's orbital period is actually the difference in the time it takes light to traverse the shorter or longer distance. Rømer observed this effect for Jupiter's innermost moon Io and deduced that light takes 22 minutes to cross the diameter of the Earth's orbit.
Aberration of light: light from a distant source appears to be from a different location for a moving telescope due to the finite speed of light.
Another method is to use the aberration of light, discovered and explained by James Bradley in the 18th century.[85] This effect results from the vector addition of the velocity of light arriving from a distant source (such as a star) and the velocity of its observer (see diagram on the right). A moving observer thus sees the light coming from a slightly different direction and consequently sees the source at a position shifted from its original position. Since the direction of the Earth's velocity changes continuously as the Earth orbits the Sun, this effect causes the apparent position of stars to move around. From the angular difference in the position of stars (maximally 20.5 arcseconds)[86] it is possible to express the speed of light in terms of the Earth's velocity around the Sun, which with the known length of a year can be easily converted to the time needed to travel from the Sun to the Earth. In 1729, Bradley used this method to derive that light travelled 10,210 times faster than the Earth in its orbit (the modern figure is 10,066 times faster) or, equivalently, that it would take light 8 minutes 12 seconds to travel from the Sun to the Earth.[85]
Nowadays, the "light time for unit distance"—the inverse of c, expressed in seconds per astronomical unit—is measured by comparing the time for radio signals to reach different spacecraft in the Solar System, with their position calculated from the gravitational effects of the Sun and various planets. By combining many such measurements, a best fit value for the light time per unit distance is obtained. As of 2009[update], the best estimate, as approved by the International Astronomical Union (IAU), is:[87][88]
light time for unit distance: 499.004783836(10) sc = 0.00200398880410(4) AU/s = 173.144632674(3) AU/day.The relative uncertainty in these measurements is 0.02 parts per billion (2×10−11), equivalent to the uncertainty in Earth-based measurements of length by interferometry.[89][Note 8] Since the metre is defined to be the length travelled by light in a certain time interval, the measurement of the light time for unit distance can also be interpreted as measuring the length of an AU in metres.
I've been looking on the internet for how astronomers calculate distances and it seems like they all assume at least one thing and then take that assumption and apply it to the rest of the solar system and universe.
I don't really understand exactly how they go about it but somehow they figure when Venus is tangential to the Earth and the sun that gives them a proportion for how much farther away the sun is from the earth than from Venus. They state Venus is 70% as far from the sun as Earth. And apparently some guy named Arius or something did the same thing except with the moon.
In geometry you have to know a distance before you use a sin or tangent. So someone is guessing at something it seems to me. Unless you really did run out there with your tape measure...
I don't know. I still say they assume too much.
I don't really understand exactly how they go about it but somehow they figure when Venus is tangential to the Earth and the sun that gives them a proportion for how much farther away the sun is from the earth than from Venus. They state Venus is 70% as far from the sun as Earth. And apparently some guy named Arius or something did the same thing except with the moon.
In geometry you have to know a distance before you use a sin or tangent. So someone is guessing at something it seems to me. Unless you really did run out there with your tape measure...
I don't know. I still say they assume too much.
The bible is Gods Word.
Heliocentrism is the unscientific musings of sun worshippers and witches.
I can choose to believe in one and not the other quite easily thank you.
Gods book contains enough info to understand the mechanics of the universe. I'll go with Gods Word.
You dont have any empiical data. You have hypatheics.
In actual fact I have 4 experiments that prove the Earth is stationary.
Before I show them to you, tell me....is space made up of something or nothing?
Heliocentrism is the unscientific musings of sun worshippers and witches.
I can choose to believe in one and not the other quite easily thank you.
Gods book contains enough info to understand the mechanics of the universe. I'll go with Gods Word.
You dont have any empiical data. You have hypatheics.
In actual fact I have 4 experiments that prove the Earth is stationary.
Before I show them to you, tell me....is space made up of something or nothing?
A
ROFL!!! What a troll this alt character is that rejects heliocentric theory for geocentrism... says the sun and planets revolve around the earth and the speed of light is off... haha.
People make up alternative characters and use them as trolls all the time. This is obviously one of them... lol. It's the only logical explanation. Isn't that right Desert Joe? HAHA!!!
People make up alternative characters and use them as trolls all the time. This is obviously one of them... lol. It's the only logical explanation. Isn't that right Desert Joe? HAHA!!!
Heres one of them gramps.
Time of flight techniques
A method of measuring the speed of light is to measure the time needed for light to travel to a mirror at a known distance and back. This is the working principle behind the Fizeau–Foucault apparatus developed by Hippolyte Fizeau and Léon Foucault.
Diagram of the Fizeau apparatus
The setup as used by Fizeau consists of a beam of light directed at a mirror 8 kilometres (5 mi) away. On the way from the source to the mirror, the beam passes through a rotating cogwheel. At a certain rate of rotation, the beam passes through one gap on the way out and another on the way back, but at slightly higher or lower rates, the beam strikes a tooth and does not pass through the wheel. Knowing the distance between the wheel and the mirror, the number of teeth on the wheel, and the rate of rotation, the speed of light can be calculated.[90]
The method of Foucault replaces the cogwheel by a rotating mirror. Because the mirror keeps rotating while the light travels to the distant mirror and back, the light is reflected from the rotating mirror at a different angle on its way out than it is on its way back. From this difference in angle, the known speed of rotation and the distance to the distant mirror the speed of light may be calculated.[91]
Nowadays, using oscilloscopes with time resolutions of less than one nanosecond, the speed of light can be directly measured by timing the delay of a light pulse from a laser or an LED reflected from a mirror. This method is less precise (with errors of the order of 1%) than other modern techniques, but it is sometimes used as a laboratory experiment in college physics classes.[92][93][94
Time of flight techniques
A method of measuring the speed of light is to measure the time needed for light to travel to a mirror at a known distance and back. This is the working principle behind the Fizeau–Foucault apparatus developed by Hippolyte Fizeau and Léon Foucault.
Diagram of the Fizeau apparatus
The setup as used by Fizeau consists of a beam of light directed at a mirror 8 kilometres (5 mi) away. On the way from the source to the mirror, the beam passes through a rotating cogwheel. At a certain rate of rotation, the beam passes through one gap on the way out and another on the way back, but at slightly higher or lower rates, the beam strikes a tooth and does not pass through the wheel. Knowing the distance between the wheel and the mirror, the number of teeth on the wheel, and the rate of rotation, the speed of light can be calculated.[90]
The method of Foucault replaces the cogwheel by a rotating mirror. Because the mirror keeps rotating while the light travels to the distant mirror and back, the light is reflected from the rotating mirror at a different angle on its way out than it is on its way back. From this difference in angle, the known speed of rotation and the distance to the distant mirror the speed of light may be calculated.[91]
Nowadays, using oscilloscopes with time resolutions of less than one nanosecond, the speed of light can be directly measured by timing the delay of a light pulse from a laser or an LED reflected from a mirror. This method is less precise (with errors of the order of 1%) than other modern techniques, but it is sometimes used as a laboratory experiment in college physics classes.[92][93][94