Fundamentals of String Theory
The fundamental objects of string theory are open and closed string models.
In the twentieth century, two theoretical frameworks emerged for formulating the laws of physics. The first is Albert Einstein's general theory of relativity, a theory that explains the force of gravity and the structure of space and time. The other is quantum mechanics which is a completely different formulation to describe physical phenomena using the known probability principles. By the late 1970s, these two frameworks had proven to be sufficient to explain most of the observed features of the universe, from elementary particles to atoms to the evolution of stars and the universe as a whole.
In spite of these successes, there are still many problems that remain to be solved. One of the deepest problems in modern physics is the problem of quantum gravity. The general theory of relativity is formulated within the framework of classical physics, whereas the other fundamental forces are described within the framework of quantum mechanics. A quantum theory of gravity is needed in order to reconcile general relativity with the principles of quantum mechanics, but difficulties arise when one attempts to apply the usual prescriptions of quantum theory to the force of gravity. In addition to the problem of developing a consistent theory of quantum gravity, there are many other fundamental problems in the physics of atomic nuclei, black holes, and the early universe.
String theory is a theoretical framework that attempts to address these questions and many others. The starting point for string theory is the idea that the point-like particles of particle physics can also be modeled as one-dimensional objects called strings. String theory describes how strings propagate through space and interact with each other. In a given version of string theory, there is only one kind of string, which may look like a small loop or segment of ordinary string, and it can vibrate in different ways. On distance scales larger than the string scale, a string will look just like an ordinary particle, with its mass, charge, and other properties determined by the vibrational state of the string. In this way, all of the different elementary particles may be viewed as vibrating strings. In string theory, one of the vibrational states of the string gives rise to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.
One of the main developments of the past several decades in string theory was the discovery of certain "dualities", mathematical transformations that identify one physical theory with another. Physicists studying string theory have discovered a number of these dualities between different versions of string theory, and this has led to the conjecture that all consistent versions of string theory are subsumed in a single framework known as M-theory.
Studies of string theory have also yielded a number of results on the nature of black holes and the gravitational interaction. There are certain paradoxes that arise when one attempts to understand the quantum aspects of black holes, and work on string theory has attempted to clarify these issues. In late 1997 this line of work culminated in the discovery of the anti-de Sitter/conformal field theory correspondence or AdS/CFT. This is a theoretical result which relates string theory to other physical theories which are better understood theoretically. The AdS/CFT correspondence has implications for the study of black holes and quantum gravity, and it has been applied to other subjects, including nuclear[6] and condensed matter physics.
Since string theory incorporates all of the fundamental interactions, including gravity, many physicists hope that it fully describes our universe, making it a theory of everything.
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The fundamental objects of string theory are open and closed string models.
In the twentieth century, two theoretical frameworks emerged for formulating the laws of physics. The first is Albert Einstein's general theory of relativity, a theory that explains the force of gravity and the structure of space and time. The other is quantum mechanics which is a completely different formulation to describe physical phenomena using the known probability principles. By the late 1970s, these two frameworks had proven to be sufficient to explain most of the observed features of the universe, from elementary particles to atoms to the evolution of stars and the universe as a whole.
In spite of these successes, there are still many problems that remain to be solved. One of the deepest problems in modern physics is the problem of quantum gravity. The general theory of relativity is formulated within the framework of classical physics, whereas the other fundamental forces are described within the framework of quantum mechanics. A quantum theory of gravity is needed in order to reconcile general relativity with the principles of quantum mechanics, but difficulties arise when one attempts to apply the usual prescriptions of quantum theory to the force of gravity. In addition to the problem of developing a consistent theory of quantum gravity, there are many other fundamental problems in the physics of atomic nuclei, black holes, and the early universe.
String theory is a theoretical framework that attempts to address these questions and many others. The starting point for string theory is the idea that the point-like particles of particle physics can also be modeled as one-dimensional objects called strings. String theory describes how strings propagate through space and interact with each other. In a given version of string theory, there is only one kind of string, which may look like a small loop or segment of ordinary string, and it can vibrate in different ways. On distance scales larger than the string scale, a string will look just like an ordinary particle, with its mass, charge, and other properties determined by the vibrational state of the string. In this way, all of the different elementary particles may be viewed as vibrating strings. In string theory, one of the vibrational states of the string gives rise to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.
One of the main developments of the past several decades in string theory was the discovery of certain "dualities", mathematical transformations that identify one physical theory with another. Physicists studying string theory have discovered a number of these dualities between different versions of string theory, and this has led to the conjecture that all consistent versions of string theory are subsumed in a single framework known as M-theory.
Studies of string theory have also yielded a number of results on the nature of black holes and the gravitational interaction. There are certain paradoxes that arise when one attempts to understand the quantum aspects of black holes, and work on string theory has attempted to clarify these issues. In late 1997 this line of work culminated in the discovery of the anti-de Sitter/conformal field theory correspondence or AdS/CFT. This is a theoretical result which relates string theory to other physical theories which are better understood theoretically. The AdS/CFT correspondence has implications for the study of black holes and quantum gravity, and it has been applied to other subjects, including nuclear[6] and condensed matter physics.
Since string theory incorporates all of the fundamental interactions, including gravity, many physicists hope that it fully describes our universe, making it a theory of everything.
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👍1
What Is Cosmology?
Cosmology is the branch of astronomy involving the origin and evolution of the universe, from the Big Bang to today and on into the future. According to NASA, the definition of cosmology is “the scientific study of the large scale properties of the universe as a whole.”
Cosmologists puzzle over exotic concepts like string theory, dark matter and dark energy and whether there is one universe or many (sometimes called the multiverse). While other aspects astronomy deal with individual objects and phenomena or collections of objects, cosmology spans the entire universe from birth to death, with a boatload of mysteries at every stage.
History of cosmology & astronomy
Humanity's understanding of the universe has evolved significantly over time. In the early history of astronomy, Earth was regarded as the center of all things, with planets and stars orbiting it. In the 16th century, Polish scientist Nicolaus Copernicus suggested that Earth and the other planets in the solar system in fact orbited the sun, creating a profound shift in the understanding of the cosmos. In the late 17th century, Isaac Newton calculated how the forces between planets — specifically the gravitational forces — interacted.
The dawn of the 20th century brought further insights into comprehending the vast universe. Albert Einstein proposed the unification of space and time in his General Theory of Relativity. In the early 1900s, scientists were debating whether the Milky Way contained the whole universe within its span, or whether it was simply one of many collections of stars. Edwin Hubblecalculated the distance to a fuzzy nebulous object in the sky and determined that it lay outside of the Milky Way, proving our galaxy to be a small drop in the enormous universe. Using General Relativity to lay the framework, Hubble measured other galaxies and determined that they were rushing away from the us, leading him to conclude that the universe was not static but expanding.
In recent decades, cosmologist Stephen Hawking determined that the universe itself is not infinite but has a definite size. However, it lacks a definite boundary. This is similar to Earth; although the planet is finite, a person traveling around it would never find the "end" but would instead constantly circle the globe. Hawking also proposed that the universe would not continue on forever but would eventually end.
Some researchers think concentric ring patterns in measurements of the cosmic microwave background are evidence of a universe that existed before our own was born in the Big Bang.
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Cosmology is the branch of astronomy involving the origin and evolution of the universe, from the Big Bang to today and on into the future. According to NASA, the definition of cosmology is “the scientific study of the large scale properties of the universe as a whole.”
Cosmologists puzzle over exotic concepts like string theory, dark matter and dark energy and whether there is one universe or many (sometimes called the multiverse). While other aspects astronomy deal with individual objects and phenomena or collections of objects, cosmology spans the entire universe from birth to death, with a boatload of mysteries at every stage.
History of cosmology & astronomy
Humanity's understanding of the universe has evolved significantly over time. In the early history of astronomy, Earth was regarded as the center of all things, with planets and stars orbiting it. In the 16th century, Polish scientist Nicolaus Copernicus suggested that Earth and the other planets in the solar system in fact orbited the sun, creating a profound shift in the understanding of the cosmos. In the late 17th century, Isaac Newton calculated how the forces between planets — specifically the gravitational forces — interacted.
The dawn of the 20th century brought further insights into comprehending the vast universe. Albert Einstein proposed the unification of space and time in his General Theory of Relativity. In the early 1900s, scientists were debating whether the Milky Way contained the whole universe within its span, or whether it was simply one of many collections of stars. Edwin Hubblecalculated the distance to a fuzzy nebulous object in the sky and determined that it lay outside of the Milky Way, proving our galaxy to be a small drop in the enormous universe. Using General Relativity to lay the framework, Hubble measured other galaxies and determined that they were rushing away from the us, leading him to conclude that the universe was not static but expanding.
In recent decades, cosmologist Stephen Hawking determined that the universe itself is not infinite but has a definite size. However, it lacks a definite boundary. This is similar to Earth; although the planet is finite, a person traveling around it would never find the "end" but would instead constantly circle the globe. Hawking also proposed that the universe would not continue on forever but would eventually end.
Some researchers think concentric ring patterns in measurements of the cosmic microwave background are evidence of a universe that existed before our own was born in the Big Bang.
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Common cosmological questions
What came before the Big Bang?
Because of the enclosed and finite nature of the universe, we cannot see "outside" of our own universe. Space and time began with the Big Bang. While there is a number of speculations about the existence of other universes, there is no practical way to observe them, and as such there will never be any evidence for (or against!) them.
Where did the Big Bang happen?
The Big Bang did not happen at a single point but instead was the appearance of space and time throughout the entire universe at once.
If other galaxies all seem to be rushing away from us, doesn't that place us at the center of the universe?
No, because if we were to travel to a distant galaxy, it would seem that all surrounding galaxies were similarly rushing away. Think of the universe as a giant balloon. If you mark multiple points on the balloon, then blow it up, you would note that each point is moving away from all of the others, though none are at the center. The expansion of the universe functions in much the same way.
How old is the universe?
The universe is 13.7 billion years old, give or take a hundred million years or so.
Will the universe end? If so, how?
Whether or not the universe will come to an end depends on its density — how spread out the matter within it might be. Scientists have calculated a "critical density" for the universe. If its true density is greater than their calculations, eventually the expansion of the universe will slow and then, ultimately, reverse until it collapses. However, if the density is less than the critical density, the universe will continue to expand forever.
Which came first, the chicken…er, the galaxy or the stars?
The post-Big Bang universe was composed predominantly of hydrogen, with a little bit of helium thrown in for good measure. Gravity caused the hydrogen to collapse inward, forming structures. However, astronomers are uncertain whether the first massive blobs formed individual stars that later fell together via gravity, or the mass came together in galaxy-sized clumps that later formed stars.
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What came before the Big Bang?
Because of the enclosed and finite nature of the universe, we cannot see "outside" of our own universe. Space and time began with the Big Bang. While there is a number of speculations about the existence of other universes, there is no practical way to observe them, and as such there will never be any evidence for (or against!) them.
Where did the Big Bang happen?
The Big Bang did not happen at a single point but instead was the appearance of space and time throughout the entire universe at once.
If other galaxies all seem to be rushing away from us, doesn't that place us at the center of the universe?
No, because if we were to travel to a distant galaxy, it would seem that all surrounding galaxies were similarly rushing away. Think of the universe as a giant balloon. If you mark multiple points on the balloon, then blow it up, you would note that each point is moving away from all of the others, though none are at the center. The expansion of the universe functions in much the same way.
How old is the universe?
The universe is 13.7 billion years old, give or take a hundred million years or so.
Will the universe end? If so, how?
Whether or not the universe will come to an end depends on its density — how spread out the matter within it might be. Scientists have calculated a "critical density" for the universe. If its true density is greater than their calculations, eventually the expansion of the universe will slow and then, ultimately, reverse until it collapses. However, if the density is less than the critical density, the universe will continue to expand forever.
Which came first, the chicken…er, the galaxy or the stars?
The post-Big Bang universe was composed predominantly of hydrogen, with a little bit of helium thrown in for good measure. Gravity caused the hydrogen to collapse inward, forming structures. However, astronomers are uncertain whether the first massive blobs formed individual stars that later fell together via gravity, or the mass came together in galaxy-sized clumps that later formed stars.
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Cosmology - The Expanding Universe
Cosmology is the study of the universe. Tracing back in the time, there were several school of thoughts regarding the origin of the universe. Many scholars believed in the Steady State Theory. As per this theory, the universe was always the same, it had no beginning.
While there were a group of people who had faith in the Big Bang Theory. This theory predicts the beginning of the universe. There were evidences of hot left out radiation from the Big Bang, which again supports the model. The Big Bang Theory predicts the abundance of light elements in the universe. Thus, following the famous model of Big Bang, we can state that the universe had a beginning. We are living in an expanding universe.
The Hubble Redshift
In the early 1900’s, the state of the art telescope, Mt Wilson, a 100-inch telescope, was the biggest telescope then. Hubble was one of the prominent scientists, who worked with that telescope. He discovered there were galaxies outside the Milky Way. Extragalactic Astronomy is only 100 years old. Mt Wilson was the biggest telescope until Palmer Observatory was built which had a 200-inch telescope.
Hubble was not the only person observing galaxies outside the Milky Way, Humason helped him. They set out on measuring the spectra of nearby galaxies. They then observed a galactic spectrum was in the visible wavelength range with continuous emission. There were emission and absorption lines on top of the continuum. From these lines, we can make an estimate if the galaxy is moving away from us or towards us.
When we get a spectrum, we assume the strongest line is coming from H-α. From literature, the strongest line should occur at 6563 Å, but if the line occurs somewhere around 7000Å, we can easily say it is redshifted.
From the Special Theory of Relativity,
1+z=1+vc1−vc−−−−−√1+z=1+vc1−vc
where, Z is the redshift, a dimensionless number and v is the recession velocity.
λobsλrest=1+zλobsλrest=1+z
Hubble and Humason listed down 22 Galaxies in their paper. Nearly all these galaxies exhibited redshift. They plotted the velocity (km/s) vs distance (Mpc). They observed a linear trend and Hubble put forward his famous law as follows.
vr=Hodvr=Hod
This is the Hubble Redshift Distance Relationship. The subscript r indicates expansion is in the radial direction. While, vrvr is the receding velocity, HoHo is the Hubble parameter, d is the distance of the galaxy from us. They concluded far away galaxies recede faster from us, if the rate of expansion for the universe is uniform.
The Expansion
Everything is moving away from us. The galaxies are not stationary, there is some expansion harmonic always. The units of the Hubble parameter are km sec−1Mpc−1. If one goes out a distance of – 1 Mpc, galaxies would be moving at the rate of 200 kms/sec. The Hubble parameter gives us the rate of expansion. As per Hubble and Humason, the value of HoHo is 200 kms/sec/Mpc.
The data showed all galaxies are moving away from us. Thus, it is apparent that we are at the center of the universe. But Hubble didn’t make this mistake, as per him, in whichever galaxy we live, we would find all other galaxies moving away from us. Thus, the conclusion is that the space between galaxies expand and there is no center of the universe.
The expansion is happening everywhere. However, there are some forces that are opposing expansion. Chemical bonds, gravitational force and other attractive forces are holding objects together. Earlier all the objects were close together. Considering the Big Bang as an impulsive force, these objects are set to move away from each other.
Time Scale
At local scales, Kinematics is governed by Gravity. In the original Hubble’s law, there were some galaxies which showed blue-shift. This can be credited to combined gravitational potential of the galaxies. Gravity has decoupled things from the Hubble’s law. The Andromeda Galaxy is coming towards to us. Gravity is trying to slow things down.
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Cosmology is the study of the universe. Tracing back in the time, there were several school of thoughts regarding the origin of the universe. Many scholars believed in the Steady State Theory. As per this theory, the universe was always the same, it had no beginning.
While there were a group of people who had faith in the Big Bang Theory. This theory predicts the beginning of the universe. There were evidences of hot left out radiation from the Big Bang, which again supports the model. The Big Bang Theory predicts the abundance of light elements in the universe. Thus, following the famous model of Big Bang, we can state that the universe had a beginning. We are living in an expanding universe.
The Hubble Redshift
In the early 1900’s, the state of the art telescope, Mt Wilson, a 100-inch telescope, was the biggest telescope then. Hubble was one of the prominent scientists, who worked with that telescope. He discovered there were galaxies outside the Milky Way. Extragalactic Astronomy is only 100 years old. Mt Wilson was the biggest telescope until Palmer Observatory was built which had a 200-inch telescope.
Hubble was not the only person observing galaxies outside the Milky Way, Humason helped him. They set out on measuring the spectra of nearby galaxies. They then observed a galactic spectrum was in the visible wavelength range with continuous emission. There were emission and absorption lines on top of the continuum. From these lines, we can make an estimate if the galaxy is moving away from us or towards us.
When we get a spectrum, we assume the strongest line is coming from H-α. From literature, the strongest line should occur at 6563 Å, but if the line occurs somewhere around 7000Å, we can easily say it is redshifted.
From the Special Theory of Relativity,
1+z=1+vc1−vc−−−−−√1+z=1+vc1−vc
where, Z is the redshift, a dimensionless number and v is the recession velocity.
λobsλrest=1+zλobsλrest=1+z
Hubble and Humason listed down 22 Galaxies in their paper. Nearly all these galaxies exhibited redshift. They plotted the velocity (km/s) vs distance (Mpc). They observed a linear trend and Hubble put forward his famous law as follows.
vr=Hodvr=Hod
This is the Hubble Redshift Distance Relationship. The subscript r indicates expansion is in the radial direction. While, vrvr is the receding velocity, HoHo is the Hubble parameter, d is the distance of the galaxy from us. They concluded far away galaxies recede faster from us, if the rate of expansion for the universe is uniform.
The Expansion
Everything is moving away from us. The galaxies are not stationary, there is some expansion harmonic always. The units of the Hubble parameter are km sec−1Mpc−1. If one goes out a distance of – 1 Mpc, galaxies would be moving at the rate of 200 kms/sec. The Hubble parameter gives us the rate of expansion. As per Hubble and Humason, the value of HoHo is 200 kms/sec/Mpc.
The data showed all galaxies are moving away from us. Thus, it is apparent that we are at the center of the universe. But Hubble didn’t make this mistake, as per him, in whichever galaxy we live, we would find all other galaxies moving away from us. Thus, the conclusion is that the space between galaxies expand and there is no center of the universe.
The expansion is happening everywhere. However, there are some forces that are opposing expansion. Chemical bonds, gravitational force and other attractive forces are holding objects together. Earlier all the objects were close together. Considering the Big Bang as an impulsive force, these objects are set to move away from each other.
Time Scale
At local scales, Kinematics is governed by Gravity. In the original Hubble’s law, there were some galaxies which showed blue-shift. This can be credited to combined gravitational potential of the galaxies. Gravity has decoupled things from the Hubble’s law. The Andromeda Galaxy is coming towards to us. Gravity is trying to slow things down.
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Initially the expansion was slowing down, now it is speeding up.
There was a Cosmic Jerk because of this. Several estimates to the Hubble parameter has been made. It has evolved over the 90 years from 500 kms/sec/Mpc to 69 kms/sec/Mpc. The disparity in the value was because of the underestimation of distance. The Cepheid Stars were used as distance calibrators, however there are different types of Cepheid stars and this fact was not considered for the estimation of the Hubble parameter.
Hubble Time
The Hubble constant gives us a realistic estimate of the age of the universe. The HoHo would give the age of the universe provided the galaxies have been moving with the same velocity. The inverse of HoHo gives us Hubble time.
tH=1HotH=1Ho
Replacing the present value of Ho,tHHo,tH = 14 billion years. Rate of expansion has been constant throughout the beginning of the Universe. Even if this is not true, HoHo gives a useful limit on the age of the universe. Assuming a constant rate of expansion, when we plot a graph between distance and time, the slope of the graph is given by velocity.
In this case, the Hubble time is equal to the actual time. However, if the universe had been expanding faster in the past and slower in the present, the Hubble time gives an upper limit of age of the universe. If the universe was expanding slowly before, and speeding up now, then the Hubble time will give a lower limit on age of the universe.
· tH=tagetH=tage − if rate of expansion is constant.
· tH>tagetH>tage − if universe has expanded faster in the past and slower in the present.
· tH<tagetH<tage − if universe has expanded slower in the past and faster in the present.
Consider a group of 10 galaxies which are at 200 Mpc from another group of galaxies. The galaxies within a cluster never conclude that the universe is expanding because kinematics within a local group is governed by gravitation.
Points to Remember
· Cosmology is the study of the past, present and future of our Universe.
· Our universe is ∼14 billion years old.
· The universe is continuously expanding.
· Hubble parameter is a measure of the age of the universe.
· Current value of Ho is 69 kms/sec/Mpc.
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There was a Cosmic Jerk because of this. Several estimates to the Hubble parameter has been made. It has evolved over the 90 years from 500 kms/sec/Mpc to 69 kms/sec/Mpc. The disparity in the value was because of the underestimation of distance. The Cepheid Stars were used as distance calibrators, however there are different types of Cepheid stars and this fact was not considered for the estimation of the Hubble parameter.
Hubble Time
The Hubble constant gives us a realistic estimate of the age of the universe. The HoHo would give the age of the universe provided the galaxies have been moving with the same velocity. The inverse of HoHo gives us Hubble time.
tH=1HotH=1Ho
Replacing the present value of Ho,tHHo,tH = 14 billion years. Rate of expansion has been constant throughout the beginning of the Universe. Even if this is not true, HoHo gives a useful limit on the age of the universe. Assuming a constant rate of expansion, when we plot a graph between distance and time, the slope of the graph is given by velocity.
In this case, the Hubble time is equal to the actual time. However, if the universe had been expanding faster in the past and slower in the present, the Hubble time gives an upper limit of age of the universe. If the universe was expanding slowly before, and speeding up now, then the Hubble time will give a lower limit on age of the universe.
· tH=tagetH=tage − if rate of expansion is constant.
· tH>tagetH>tage − if universe has expanded faster in the past and slower in the present.
· tH<tagetH<tage − if universe has expanded slower in the past and faster in the present.
Consider a group of 10 galaxies which are at 200 Mpc from another group of galaxies. The galaxies within a cluster never conclude that the universe is expanding because kinematics within a local group is governed by gravitation.
Points to Remember
· Cosmology is the study of the past, present and future of our Universe.
· Our universe is ∼14 billion years old.
· The universe is continuously expanding.
· Hubble parameter is a measure of the age of the universe.
· Current value of Ho is 69 kms/sec/Mpc.
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Fundamental Forces
There are four fundamental forces in nature. They are Electromagnetism, the Weak Nuclear Force, the Strong Nuclear Force and Gravitation.
The Weak Nuclear Force is associated with radioactivity in unstable nuclei, specifically the decay of a neutron into a proton in the form of Beta radiation. The gauge bosons that mediate the force are the W and Z bosons. This interaction can cause quarks to change flavours.
The Strong Nuclear Force binds together quarks to form nucleons, in turn, it also acts to bind these nucleons together, forming atomic nuclei. The force is mediated by an exchange of gluons, which are a type of gauge boson. The charge associated with this force, analogous to the electric charge associated with electromagnetism, is the Colour charge, of which there are three varieties; Red, Green and Blue. The mathematical theory describing the elementary particles interacting with this force, Quarks and Gluons, is known as Quantum Chromodynamics (QCD). At atomic levels, it is by far the strongest of all forces, but only interacts on a scale on the order of 10-15m, and therefore, whilst incredibly important for the formation of matter, does not play any observable role in day to day life.
Electromagnetism is a force associated with the electric charge associated with certain molecules. Along with gravitation, is is one of the four forces that has a major noticeable effect on day to day human life. It manifests as two different fields electric fields and magnetic fields, although they are aspects of the same force and therefore interact with each other through electromagnetic induction. The gauge boson that mediates this force is the photon, which is also the quanta (discrete packet) of light and other forms of electromagnetic radiation, such as infra-red radiation (most thermal radiation), X-rays, Ultraviolet radiation etc..
Gravitation is a force of attraction between two massive bodies. Objects on Earth are attracted to the Earth via gravitation, why is why, when an apple falls from a tree, it falls down towards the Earth, instead of in any other direction. Gravitation also gives weight to objects, weight being the mass of an object multiplied by the gravitational force acted upon it by another object. Gravitation on a Universal scale is described by Einstein's theory of General Relativity, where it is described as being a result of curved spacetime. Classically, it has been described by Newton's law of gravitation, which is an accurate approximation up to a certain level of detail. Gravitation is mediated by the still-hypothetical gauge boson the Graviton. On a quantum level, there is no sufficient theory that can explain the force, although string and M-Theory are potential candidates. Explaining gravity on a quantum level is one of the major challenges in present-day physics.
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There are four fundamental forces in nature. They are Electromagnetism, the Weak Nuclear Force, the Strong Nuclear Force and Gravitation.
The Weak Nuclear Force is associated with radioactivity in unstable nuclei, specifically the decay of a neutron into a proton in the form of Beta radiation. The gauge bosons that mediate the force are the W and Z bosons. This interaction can cause quarks to change flavours.
The Strong Nuclear Force binds together quarks to form nucleons, in turn, it also acts to bind these nucleons together, forming atomic nuclei. The force is mediated by an exchange of gluons, which are a type of gauge boson. The charge associated with this force, analogous to the electric charge associated with electromagnetism, is the Colour charge, of which there are three varieties; Red, Green and Blue. The mathematical theory describing the elementary particles interacting with this force, Quarks and Gluons, is known as Quantum Chromodynamics (QCD). At atomic levels, it is by far the strongest of all forces, but only interacts on a scale on the order of 10-15m, and therefore, whilst incredibly important for the formation of matter, does not play any observable role in day to day life.
Electromagnetism is a force associated with the electric charge associated with certain molecules. Along with gravitation, is is one of the four forces that has a major noticeable effect on day to day human life. It manifests as two different fields electric fields and magnetic fields, although they are aspects of the same force and therefore interact with each other through electromagnetic induction. The gauge boson that mediates this force is the photon, which is also the quanta (discrete packet) of light and other forms of electromagnetic radiation, such as infra-red radiation (most thermal radiation), X-rays, Ultraviolet radiation etc..
Gravitation is a force of attraction between two massive bodies. Objects on Earth are attracted to the Earth via gravitation, why is why, when an apple falls from a tree, it falls down towards the Earth, instead of in any other direction. Gravitation also gives weight to objects, weight being the mass of an object multiplied by the gravitational force acted upon it by another object. Gravitation on a Universal scale is described by Einstein's theory of General Relativity, where it is described as being a result of curved spacetime. Classically, it has been described by Newton's law of gravitation, which is an accurate approximation up to a certain level of detail. Gravitation is mediated by the still-hypothetical gauge boson the Graviton. On a quantum level, there is no sufficient theory that can explain the force, although string and M-Theory are potential candidates. Explaining gravity on a quantum level is one of the major challenges in present-day physics.
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11 Amazing Facts
1. The first person to look into space with a telescope was Galileo, nearly 400 years ago
2. Because fragrance is dependent on several environmental factors, such as temperature, humidity, and a flower’s age, flowers smell differently in space than they do on Earth. The fragrance of a variety of roses grown on the space shuttle Discovery was later replicated and incorporated into “Zen,” a perfume sold by the Japanese company Shiseido.
3. Space is flexible. It’s been expanding at a measurable rate since the beginning of time.
4. There is no sound in space.
5. In the film 2001: A Space Odyssey, Bowman should have exhaled instead of inhaling before attempting to re-enter the ship from the pod after HAL locks him out. The vacuum of space would have damaged his lungs if they had been full of air.
6. On Earth, a flame will rise. In space, however, a flame will move outward from its source in all directions. Because space has no gravity, the expanding hot air experiences equal resistance in all directions, so it moves spherically from its source. A match would need to be struck in a space vehicle or station with an oxygen-bearing atmosphere because a flame needs oxygen.
7. The first woman in space was Valentina Tereshkova, a Soviet cosmonaut who flew aboard the Vostok 6 on June 16, 1963.
8. Because there is no gravity in space, there is no natural convection, which means body heat won’t rise off the skin. Because of this, the body will constantly perspire to cool itself but, unfortunately, the sweat won’t drip or evaporate—it will just build up.
9. Because there is no gravity in space, there is no buoyant force, which means nothing pushes bubbles up and out of carbonated drinks in space. Therefore, it is impossible to burp out the gas of, say, a root beer.
10. Astronomers hypothesize three different possible scenarios for our universe: 1) we have a closed universe, which means the universe will eventually collapse into another singularity; 2) we have an open universe, which means that the universe will keep expanding forever until everything is so far apart that the universe becomes inert and dead; and 3) we have a flat universe, which means gravity is just right and will hold the universe together at just the right dimensions to allow things to go on indefinitely. This last scenario is also known as the Goldilocks effect, where everything is “just right.”
11. Cosmic rays are highly energetic particles that flow throughout our solar system from deep in outer space, but astronomers are unsure of their origins.
@LAQMC @LAQMC
@BIOOZOO @BIOOZOO
1. The first person to look into space with a telescope was Galileo, nearly 400 years ago
2. Because fragrance is dependent on several environmental factors, such as temperature, humidity, and a flower’s age, flowers smell differently in space than they do on Earth. The fragrance of a variety of roses grown on the space shuttle Discovery was later replicated and incorporated into “Zen,” a perfume sold by the Japanese company Shiseido.
3. Space is flexible. It’s been expanding at a measurable rate since the beginning of time.
4. There is no sound in space.
5. In the film 2001: A Space Odyssey, Bowman should have exhaled instead of inhaling before attempting to re-enter the ship from the pod after HAL locks him out. The vacuum of space would have damaged his lungs if they had been full of air.
6. On Earth, a flame will rise. In space, however, a flame will move outward from its source in all directions. Because space has no gravity, the expanding hot air experiences equal resistance in all directions, so it moves spherically from its source. A match would need to be struck in a space vehicle or station with an oxygen-bearing atmosphere because a flame needs oxygen.
7. The first woman in space was Valentina Tereshkova, a Soviet cosmonaut who flew aboard the Vostok 6 on June 16, 1963.
8. Because there is no gravity in space, there is no natural convection, which means body heat won’t rise off the skin. Because of this, the body will constantly perspire to cool itself but, unfortunately, the sweat won’t drip or evaporate—it will just build up.
9. Because there is no gravity in space, there is no buoyant force, which means nothing pushes bubbles up and out of carbonated drinks in space. Therefore, it is impossible to burp out the gas of, say, a root beer.
10. Astronomers hypothesize three different possible scenarios for our universe: 1) we have a closed universe, which means the universe will eventually collapse into another singularity; 2) we have an open universe, which means that the universe will keep expanding forever until everything is so far apart that the universe becomes inert and dead; and 3) we have a flat universe, which means gravity is just right and will hold the universe together at just the right dimensions to allow things to go on indefinitely. This last scenario is also known as the Goldilocks effect, where everything is “just right.”
11. Cosmic rays are highly energetic particles that flow throughout our solar system from deep in outer space, but astronomers are unsure of their origins.
@LAQMC @LAQMC
@BIOOZOO @BIOOZOO
The Perseverance Rover (Astronomy Club)
Rover is a man made device made to explore planetary surface or planets. Such types of device or vehicle are made to travel on planets or planetary mass celestial bodies, like Mars, Venus, Moon and other planets.
Rovers use solar powers or nuclear power to keep working since rovers are electrical vehicles.
Purpose
Rovers are made to study other planets surface, scientist have sent rovers to moon and mars, more specifically rovers are send to Mars. This is because it is believed that 4.1 billion years ago both Mars and Earth were similar. They both have liquid water and magnetic field that protect them from dangerous solar winds. So scientists speculate that if life developed at that time on our planet, could it also have developed at mars?
To answer that question scientist sent rovers to study and collect information about Mars, the terrain, and to take crust samples such as dust, soil, rocks, and even liquids. Because of that, Rovers are essential tools in space exploration.
Pervious rovers
The only rovers to successfully land on Mars were sent there by NASA. They have special equipment on arms for testing the soil, taking pictures and doing other planetary science.
• Sojourner rover - The first Mars rover, this was a test vehicle to see if a solar vehicle would work on Mars. It landed on July 4th, 1997 and lasted nearly three months.
• Spirit rover (MER-A) - Spirit and Opportunity were launched as a pair. Spirit landed January 4, 2004 and lasted a little over six years.
• Opportunity rover (MER-B) - Landed January 25, 2004 and lasted a little over fourteen years until it was stopped by a dust storm.
• Curiosity rover - A nuclear-powered rover, landed August, 2012 and is still going.
What make Perseverance rover different?
The Perseverance rover will land today February 18 at dangerous sandy pits at Mars’s Jezero Crater. The reason they planned to land it at such point or place is because it is believed that this Crater was once filled with liquid water. And once the rover land and start driving toward the actual science location it can shave off a year or more of drive time.
And that is why they named it Perseverance because perseverance means persistence in doing something despite difficulty or delay in achieving success.
This is not the only reason it is different from the previous rover. The Perseverance rovers contain something new, and that is it has a little helicopter or drone named Ingenuity.
Ingenuity will test the first controlled flight on other planet
This is not the only thing the rover contains it contain many complicated technology that mankind ever made.
Links if you want to see the live steam.
Live stream: https://youtu.be/gm0b_ijaYMQ
Mark Rober video: https://youtu.be/tH2tKigOPBU
Veritasium: https://youtu.be/GhsZUZmJvaM
Join our channel:
👉 @scienceQM
👉 @LAQMC
Rover is a man made device made to explore planetary surface or planets. Such types of device or vehicle are made to travel on planets or planetary mass celestial bodies, like Mars, Venus, Moon and other planets.
Rovers use solar powers or nuclear power to keep working since rovers are electrical vehicles.
Purpose
Rovers are made to study other planets surface, scientist have sent rovers to moon and mars, more specifically rovers are send to Mars. This is because it is believed that 4.1 billion years ago both Mars and Earth were similar. They both have liquid water and magnetic field that protect them from dangerous solar winds. So scientists speculate that if life developed at that time on our planet, could it also have developed at mars?
To answer that question scientist sent rovers to study and collect information about Mars, the terrain, and to take crust samples such as dust, soil, rocks, and even liquids. Because of that, Rovers are essential tools in space exploration.
Pervious rovers
The only rovers to successfully land on Mars were sent there by NASA. They have special equipment on arms for testing the soil, taking pictures and doing other planetary science.
• Sojourner rover - The first Mars rover, this was a test vehicle to see if a solar vehicle would work on Mars. It landed on July 4th, 1997 and lasted nearly three months.
• Spirit rover (MER-A) - Spirit and Opportunity were launched as a pair. Spirit landed January 4, 2004 and lasted a little over six years.
• Opportunity rover (MER-B) - Landed January 25, 2004 and lasted a little over fourteen years until it was stopped by a dust storm.
• Curiosity rover - A nuclear-powered rover, landed August, 2012 and is still going.
What make Perseverance rover different?
The Perseverance rover will land today February 18 at dangerous sandy pits at Mars’s Jezero Crater. The reason they planned to land it at such point or place is because it is believed that this Crater was once filled with liquid water. And once the rover land and start driving toward the actual science location it can shave off a year or more of drive time.
And that is why they named it Perseverance because perseverance means persistence in doing something despite difficulty or delay in achieving success.
This is not the only reason it is different from the previous rover. The Perseverance rovers contain something new, and that is it has a little helicopter or drone named Ingenuity.
Ingenuity will test the first controlled flight on other planet
This is not the only thing the rover contains it contain many complicated technology that mankind ever made.
Links if you want to see the live steam.
Live stream: https://youtu.be/gm0b_ijaYMQ
Mark Rober video: https://youtu.be/tH2tKigOPBU
Veritasium: https://youtu.be/GhsZUZmJvaM
Join our channel:
👉 @scienceQM
👉 @LAQMC
YouTube
Watch NASA’s Perseverance Rover Land on Mars!
Watch an epic journey unfold on Thursday, Feb. 18 as our Perseverance rover lands on Mars. To reach the surface of the Red Planet, the rover has to survive the harrowing final phase known as Entry, Descent, and Landing.
Only then can the rover – the biggest…
Only then can the rover – the biggest…
What If: What If You Fell Into Jupiter?
YouTube
What If You Fell Into Jupiter?
Humans have explored the Moon, Mars, and of course, Earth. But what do we know about Jupiter?
For the most part, this gas giant is a mystery. So what would happen if you wanted to discover it for yourself and jumped right onto the planet? Or should we say…
For the most part, this gas giant is a mystery. So what would happen if you wanted to discover it for yourself and jumped right onto the planet? Or should we say…
CrashCourse: Jupiter's Moons: Crash Course Astronomy #17
YouTube
Jupiter's Moons: Crash Course Astronomy #17
Before moving on from Jupiter to Saturn, we’re going to linger for a moment on Jupiter’s moons. There are 67 known moons, 4 of which are the huge ones that we want to explore in greater detail. Ganymede is the largest - larger, in fact, than any other moon…
🌔Galilean Moons🌖
✨The Galilean moons are the four biggest of Jupiter's moons. They were discovered by Galileo, centuries before astronomers identified the others, smaller ones.
✨Ganymede is the biggest of Galilean moons. At 5262 km across, it is larger than the planet Mercury.
✨Ganymede looks solid, but under its shell of ice is 900 km of slushy ice and water.
✨At 4806 km across, Callisto is the second biggest moon of Jupiter.
✨Callisto is scarred with craters from bombardment early in the Solar System's life.
✨Io is the third largest moon at 3642 km across.
The surface of Io is a mass of volcanoes caused by it being stretched and squeezed by Jupiter's massive gravity.
✨Io's yellow glow comes from sulphur, which is thrown out as far as 300 km upwards by the moon's volcanoes.
✨The smallest of the Galilean moons is Europa at 3138 km across.
✨Europa has a smooth icy surface full of cracks, but the Galileo probe discovered an ocean of water under the ice where there might be living creatures.
@LAQMC
✨The Galilean moons are the four biggest of Jupiter's moons. They were discovered by Galileo, centuries before astronomers identified the others, smaller ones.
✨Ganymede is the biggest of Galilean moons. At 5262 km across, it is larger than the planet Mercury.
✨Ganymede looks solid, but under its shell of ice is 900 km of slushy ice and water.
✨At 4806 km across, Callisto is the second biggest moon of Jupiter.
✨Callisto is scarred with craters from bombardment early in the Solar System's life.
✨Io is the third largest moon at 3642 km across.
The surface of Io is a mass of volcanoes caused by it being stretched and squeezed by Jupiter's massive gravity.
✨Io's yellow glow comes from sulphur, which is thrown out as far as 300 km upwards by the moon's volcanoes.
✨The smallest of the Galilean moons is Europa at 3138 km across.
✨Europa has a smooth icy surface full of cracks, but the Galileo probe discovered an ocean of water under the ice where there might be living creatures.
@LAQMC
Brian Cox (physicist) - Wikipedia
https://en.m.wikipedia.org/wiki/Brian_Cox_(physicist)
https://en.m.wikipedia.org/wiki/Brian_Cox_(physicist)
Wikipedia
Brian Cox (physicist)
Brian Edward Cox (born 3 March 1968) is an English physicist and musician. He is a professor of particle physics in the School of Physics and Astronomy at the University of Manchester and the Royal Society Professor for Public Engagement in Science. He is…
First-ever 'space hurricane' detected over the North Pole | Live Science
https://www.google.com/m?q=space+hurricane&client=ms-opera-mobile&channel=new&espv=1
https://www.google.com/m?q=space+hurricane&client=ms-opera-mobile&channel=new&espv=1
Google
space hurricane - Google Search
Forwarded from ⚛️LIA Astronomy & Quantum Mechanics Club⚛️ (Kaleab Milion)
Which of the following is not the moon of Saturn?
Anonymous Quiz
23%
A. Hyperion
24%
B. Mimas
37%
C. Ariel
17%
D. Rhea
Forwarded from ⚛️LIA Astronomy & Quantum Mechanics Club⚛️ (Kaleab Milion)
Light travels at 186,282 miles per _________?
Anonymous Quiz
22%
A. hour
14%
B. minute
60%
C. second
4%
D. year
Forwarded from Quality button
Animals are one of the amazing part of our nature. Enjoy these your short time with them.
💁♂Here is all what you want !🤗
💁♂Here is all what you want !🤗
Forwarded from ⚛️LIA Astronomy & Quantum Mechanics Club⚛️ (Kaleab Milion)
On which planet do we find the great red spot?
Anonymous Quiz
61%
A. Jupiter
31%
B. Mars
4%
C. Saturn
4%
D. Uranus
Forwarded from ⚛️LIA Astronomy & Quantum Mechanics Club⚛️ (Kaleab Milion)
Which planet is closest to the sun?
Anonymous Quiz
6%
A. Ceres
84%
B. Mercury
5%
C. Venus
4%
D. Mars