The universe can be a very strange place. While groundbreaking ideas such as quantum theory, relativity and even the Earth going around the Sun might be commonly accepted now, science still continues to show that the universe contains things you might find it difficult to believe, and even more difficult to get your head around.

Negative Energy

Theoretically, the lowest temperature that can be achieved is absolute zero, exactly −273.15°C, where the motion of all particles stops completely. However, you can never actually cool something to this temperature because, in quantum mechanics, every particle has a minimum energy, called “zero-point energy,” which you cannot get below. Remarkably, this minimum energy doesn’t just apply to particles, but to any vacuum, whose energy is called “vacuum energy.” To show that this energy exists involves a rather simple experiment– take two metal plates in a vacuum, put them close together, and they will be attracted to each other. This is caused by the energy between the plates only being able to resonate at certain frequencies, while outside the plates the vacuum energy can resonate at prettymuch any frequency. Because the energy outside the plates is greater than the energy between the plates, the plates are pushed towards each other. As the plates get closer together, the force increases, and at around a 10 nm separation this effect (called the Casimir effect) creates one atmosphere of pressure between them. Because the plates reduce the vacuum energy between them to below the normal zero-point energy, the space is said to have negative energy, which has some unusual properties.

Frame Dragging
:
One prediction of Einstein’s theory of general relativity is that when a large object moves, it drags the space-time around it, causing nearby objects to be pulled along as well. It can occur when a large object is moving in a straight line or is rotating, and, although the effect is very small, it has been experimentally verified. The Gravity Probe B experiment, launched in 2004, was designed to measure the space-time distortion near Earth. Although sources of interference were larger than expected, the frame-dragging effect has been measured to an uncertainty of 15%, with further analysis hoping to reduce this further.

Relativity of Simultaneity

The relativity of simultaneity is the idea that whether two events occur simultaneously or not is relative and depends on the observer. It is a strange consequence of the special theory of relativity, and applies to any events that happen that are separated by some distance. For example, if a firework is let off on Mars and another on Venus, one observer traveling through space one way might say they happen at the same time (compensating for the time light takes to reach them), while another observer traveling another way might say the one on Mars went off first, and yet another might say the one on Venus went off first. It is caused by the way different viewpoints become distorted compared to each other in special relativity. And because they are all relative, no observer can be said to have the correct viewpoint.
This can lead to very unusual scenarios, such as an observer witnessing effect before cause (for example, seeing a bomb go off, then later seeing someone light the fuse). However, once the observer sees the effect, they cannot interact with the cause without traveling faster than the speed of light, which was one of the first reasons faster-than-light travel was believed to be forbidden, because it is akin to time travel, and a universe where you can interact with the cause after the effect makes no sense.

Cosmic Strings

Shorty after the Big Bang, the universe was in a highly disordered and chaotic state. This means that small changes and defects didn’t change the overall structure of the universe. However, as the universe expanded, cooled, and went from a disorderly state to an orderly one, it reached a point where very small fluctuations created very large changes.
This is similar to arranging tiles evenly on a floor. When one tile is placed unevenly, this means that the subsequent tiles placed will follow its pattern. Therefore, you have a whole line of tiles out of place. This is similar to the objects called cosmic strings, which are extremely thin and extremely long defects in the shape of space-time. These cosmic strings are predicted by most models of the universe, such as the string theory wherein two kinds of “strings” are unrelated. If they exist, each string would be as thin as a proton, but incredibly dense. Thus, a cosmic string a mile long can weigh as much as the Earth. However, it would not actually have any gravity and the only effect it will have on matter surrounding it would be the way it changes the form and shape of space-time. Therefore, a cosmic string is, in essence, just a “wrinkle” in the shape of space-time.
Cosmic strings are thought to be incredibly long, up to the order of the sizes of thousands of galaxies. In fact, recent observations and simulations have suggested that a network of cosmic strings stretches across the entire universe. This was once thought to be what caused galaxies to form in supercluster complexes, although this idea has since been abandoned. Supercluster complexes consist of connected “filaments” of galaxies up to a billion light-years in length. Because of the unique effects of cosmic strings on space-time as you bring two strings close together, it has been shown that they could possibly be used for time travel, like with most of the things on this list. Cosmic strings would also create incredible gravitational waves, stronger than any other known source. These waves are what those current and planned gravitational wave detectors are designed to look for.

Antimatter

Antimatter is the opposite of matter. It has the same mass but with an opposing electrical charge. One theory about why antimatter exists was developed by John Wheeler and Nobel laureate Richard Feynman based on the idea that physical systems should be time-reversible. For example, the orbits of our solar system, if played backwards, should still obey all the same rules as when they are played forwards. This led to the idea that antimatter is just ordinary matter going backwards in time, which would explain why antiparticles have an opposite charge, since if an electron is repelled while going forwards in time, then backwards in time this becomes attraction. This also explains why matter and antimatter annihilate. This isn’t a circumstance of two particles crashing into and destroying each other; it is the same particle suddenly stopping and going back in time. In a vacuum, where a pair of virtual particles are produced and then annihilated, this is actually just one particle going in an endless loop, forwards in time, then backwards, then forwards, and so on.

While the accuracy of this theory is still up for debate, treating antimatter as matter going backwards in time mathematically comes up with identical solutions to other, more conventional theories. When it was first theorized, John Wheeler said that perhaps it answered the question of why all electrons in the universe have identical properties, a question so obvious that it is generally ignored. He suggested that it was just one electron, constantly darting all over the universe, from the Big Bang to the end of time and back again, continuing an uncountable number of times. Even though this idea involves backwards time travel, it can’t be used to send any information back in time, since the mathematics of the model simply doesn’t allow it. You cannot move a piece of antimatter to affect the past, since in moving it you only affect the past of the antimatter itself, that is, your future.

Gödel’s incompleteness theorems

It is not strictly science, but rather a very interesting set of mathematical theorems about logic and the philosophy that is definitely relevant to science as a whole. Proven in 1931 by Kurt Gödel, these theories say that with any given set of logical rules, except for the most simple, there will always be statements that are undecidable, meaning that they cannot be proven or disproven due to the inevitable self-referential nature of any logical systems that is even remotely complicated. This is thought to indicate that there is no grand mathematical system capable of proving or disproving all statements. An undecidable statement can be thought of as a mathematical form of a statement like “I always lie.” Because the statement makes reference to the language being used to describe it, it cannot be known whether the statement is true or not. However, an undecidable statement does not need to be explicitly self-referential to be undecidable. The main conclusion of Gödel’s incompleteness theorems is that all logical systems will have statements that cannot be proven or disproven; therefore, all logical systems must be “incomplete.”
The philosophical implications of these theorems are widespread. The set suggests that in physics, a “theory of everything” may be impossible, as no set of rules can explain every possible event or outcome. It also indicates that logically, “proof” is a weaker concept than “true”; such a concept is unsettling for scientists because it means there will always be things that, despite being true, cannot be proven to be true. Since this set of theorems also applies to computers, it also means that our own minds are incomplete and that there are some ideas we can never know, including whether our own minds are consistent (i.e. our reasoning contains no incorrect contradictions). This is because the second of Gödel’s incompleteness theorems states that no consistent system can prove its own consistency, meaning that no sane mind can prove its own sanity. Also, since that same law states that any system able to prove its consistency to itself must be inconsistent, any mind that believes it can prove its own sanity is, therefore, insane.

Nuclear Weapons

nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. They are also called the weapons of mass destruction. The first fission (“atomic”) bomb test released the same amount of energy as approximately 20,000 tons of TNT. The first thermonuclear (“hydrogen”) bomb test released the same amount of energy as approximately 10,000,000 tons of TNT.

Since their introduction in 1945, nuclear explosives have been the most feared of the weapons of mass destruction, in part because of their ability to cause enormous instantaneous devastation and of the persistent effects of the radiation they emit, unseen and undetectable by unaided human senses. The Manhattan Project cost the United States \$2 billion in 1945 spending power and required the combined efforts of a continent-spanning industrial enterprise and a pool of scientists, many of whom had already been awarded the Nobel Prize and many more who would go on to become Nobel Laureates. This array of talent was needed in 1942 if there were to be any hope of completing a weapon during the Second World War. Because nuclear fission was discovered in Germany, which remained the home of many brilliant scientists, the United States perceived itself to be in a race to build an atomic bomb.

Fat Boy

Fat Boy

Little Boy

Little Boy

There are two basic types of nuclear weapons: those which derive the majority of their energy from nuclear fission reactions alone, and those which use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output.

Nuclear Fission: An ordinary “atomic” bomb of the kinds used in World War II uses the process of nuclear fission to release the binding energy in certain nuclei. The energy release is rapid and, because of the large amounts of energy locked in nuclei, violent. The principal materials used for fission weapons are U-235 and Pu-239, which are termed fissile because they can be split into two roughly equal-mass fragments when struck by a neutron of even low energies. When a large enough mass of either material is assembled, a self-sustaining chain reaction results after the first fission is produced.

Fission weapons require a system to assemble a supercritical mass from a sub-critical mass in a very short time. Two classic assembly systems have been used, gun and implosion. In the simpler gun-type device, two subcritical masses are brought together by using a mechanism similar to an artillery gun to shoot one mass (the projectile) at the other mass (the target). The Hiroshima weapon was gun-assembled and used 235 U as a fuel. Gun-assembled weapons using highly enriched uranium are considered the easiest of all nuclear devices to construct and the most foolproof.

Gun-Device

In the gun device, two pieces of fissionable material, each less than a critical mass, are brought together very rapidly to form a single supercritical one. This gun-type assembly may be achieved in a tubular device in which a high explosive is used to blow one subcritical piece of fissionable material from one end of the tube into another subcritical piece held at the opposite end of the tube.

Gun Device

Implosion-Device

Because of the short time interval between spontaneous neutron emissions (and, therefore, the large number of background neutrons) found in plutonium because of the decay by spontaneous fission of the isotope Pu-240, Manhattan Project scientists devised the implosion method of assembly in which high explosives are arranged to form an imploding shock wave which compresses the fissile material to supercriticality.

Implosion Assembly Principle

The core of fissile material that is formed into a super-critical mass by chemical high explosives (HE) or propellants. When the high explosive is detonated, an inwardly directed implosion wave is produced. This wave compresses the sphere of fissionable material. The decrease in surface to volume ratio of this compressed mass plus its increased density is then such as to make the mass supercritical. The HE is exploded by detonators timed electronically by a fuzing system, which may use altitude sensors or other means of control.

Fusion weapons

The basics of the Teller–Ulam design for a hydrogen bomb: a fission bomb uses radiation to compress and heat a separate section of fusion fuel.

The other basic type of nuclear weapon produces a large amount of its energy through nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs), as they rely on fusion reactions between isotopes of hydrogen (deuterium and tritium). However, all such weapons derive a significant portion, and sometimes a majority, of their energy from fission. This is because a fission weapon is required as a “trigger” for the fusion reactions, and the fusion reactions can themselves trigger additional fission reactions.

Fusion reactions do not create fission products, and thus contribute far less to the creation of nuclear fallout than fission reactions. However, because all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage from depleted uranium, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons, if not substantially more.

Nuclear Weapon Effects

Nuclear detonations are the most devastating of the weapons of mass destruction. To make this point one need only recall the pictures from Hiroshima or the international furor over the accidental but enormous radiation release from the Chernobyl power plant. The contamination from Chernobyl was significantly larger than would have been expected from a nuclear detonation of about 20 kT at ground level, but was comparable in extent to what might result from a small nuclear war in which a dozen or so weapons of nominal yield were exploded at altitudes intended to maximize blast damage.

Mass Destruction

Mushroom of Cloud over Nagasaki after Fat Boy was exploded.

A nuclear detonation creates a severe environment including blast, thermal pulse, neutrons, x- and gamma-rays, radiation, electromagnetic pulse (EMP), and ionization of the upper atmosphere. Depending upon the environment in which the nuclear de-vice is detonated, blast effects are manifested as ground shock, water shock, blueout, cratering, and large amounts of dust and radioactive fallout. All pose problems for the survival of friendly systems and can lead to the destruction or neutralization of hostile assets.

The energy of a nuclear explosion is transferred to the surrounding medium in three distinct forms: blast; thermal radiation; and nuclear radiation. The distribution of energy among these three forms will depend on the yield of the weapon, the location of the burst, and the characteristics of the environment. For a low altitude atmospheric detonation of a moderate sized weapon in the kiloton range, the energy is distributed roughly as follows:

50% as blast;

35% as thermal radiation; made up of a wide range of the electromagnetic spectrum, including infrared, visible, and ultraviolet light and some soft x-ray emitted at the time of the explosion; and

15% as nuclear radiation; including 5% as initial ionizing radiation consisting chiefly of neutrons and gamma rays emitted within the first minute after detonation, and 10% as residual nuclear radiation. Residual nuclear radiation is the hazard in fallout.

Considerable variation from this distribution will occur with changes in yield or location of the detonation.

Because of the tremendous amounts of energy liberated per unit mass in a nuclear detonation, temperatures of several tens of million degrees centigrade develop in the immediate area of the detonation. This is in marked contrast to the few thousand degrees of a conventional explosion. At these very high temperatures the nonfissioned parts of the nuclear weapon are vaporized. The atoms do not release the energy as kinetic energy but release it in the form of large amounts of electromagnetic radiation. In an atmospheric detonation, this electromagnetic radiation, consisting chiefly of soft x-ray, is absorbed within a few meters of the point of detonation by the surrounding atmosphere, heating it to extremely high temperatures and forming a brilliantly hot sphere of air and gaseous weapon residues, the so-called fireball. Immediately upon formation, the fireball begins to grow rapidly and rise like a hot air balloon. Within a millisecond after detonation, the diameter of the fireball from a 1 megaton (Mt) air burst is 150 m. This increases to a maximum of 2200 m within 10 seconds, at which time the fireball is also rising at the rate of 100 m/sec. The initial rapid expansion of the fireball severely compresses the surrounding atmosphere, producing a powerful blast wave.

Black Holes

Black Holes

What is a Black Hole ?

One of the most awe inspiring phenomenons in space is the black hole. According to the definition of Wikipedia, A black hole is a region of space-time 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 a mathematically defined 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. 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.

Blackhole Milkyway

How big is a black hole?

There are at least two different ways to describe how big something is. We can say how much mass it has, or we can say how much space it takes up.

There is no limit in principle to how much or how little mass a black hole can have. Any amount of mass at all can in principle be made to form a black hole if you compress it to a high enough density. We suspect that most of the black holes that are actually out there were produced in the deaths of massive stars, and so we expect those black holes to weigh about as much as a massive star. A typical mass for such a stellar black hole would be about 10 times the mass of the Sun, or about 10^{31} kilograms. Astronomers also suspect that many galaxies harbor extremely massive black holes at their centers. These are thought to weigh about a million times as much as the Sun, or 10^{36} kilograms.

The more massive a black hole is, the more space it takes up. In fact, the Schwarzschild radius (which means the radius of the horizon) and the mass are directly proportional to one another: if one black hole weighs ten times as much as another, its radius is ten times as large. A black hole with a mass equal to that of the Sun would have a radius of 3 kilometers. So a typical 10-solar-mass black hole would have a radius of 30 kilometers, and a million-solar-mass black hole at the center of a galaxy would have a radius of 3 million kilometers. Three million kilometers may sound like a lot, but it’s actually not so big by astronomical standards. The Sun, for example, has a radius of about 700,000 kilometers, and so that supermassive black hole has a radius only about four times bigger than the Sun.

Artist's concept of a black hole from top down. Image credit: NASA

Artist’s concept of a black hole from top down. Image credit: NASA

 In the strictest and most exact sense, there are currently 14 known black holes.

 The known closest black hole to Earth is Cygnus X-1, located about 8000 light years away.

 Although black holes have a strong suction force, they may only suck up what crosses their event horizons, and, therefore, are not capable of absorbing the whole universe.

 In theory, any matter can become black holes, as long as they are compressed to zero volume and thus, yielding infinite density. However, only the largest of stars have cores capable with the gravitational force to compress the star to the Schwarzschild radius. Most others stars without this gravitational force end up as neutron stars and white dwarfs.

 Although white holes are mathematically possible, there have yet to be observations to prove their existence.

 Black holes can suck up other black holes when they come in close proximity. Usually the larger one will suck up the smaller one. Depending on the size of the matter that is making up the black holes, the size of the black hole created will differ. Direct collisions between black holes are rare, as black holes are very small for their mass. Black holes may also merge.

Black Hole Fusion

Black Hole Fusion

 The center of a black hole, the singularity, is the point where the laws of physics break down. These singularities are hidden, or ‘clothed’ by the black hole, so that the effects of the breakdown cannot be observed by people outside.

 At the center of a black hole, spacetime has infinite curvature and matter is crushed to infinite density under the pull of ‘infinite’ gravity. At a singularity, space and time cease to exist as we know them. The laws of physics as we know them break down at a singularity, thus, making it impossible to envision something with zero volume and infinite density, such qualities of a black hole.

 By using the correct equations for motion, it can be predicted that near a black hole, an object on a radial path will have a velocity approaching the speed. This occurs as the object approches the event horizon.

 Stars are powered by nuclear fuel; most stars use hydrogen. The larger a star is, the faster it will use up its fuel, and thus, the sooner it “dies”. If the stars are large enough, however, then the gravitational pull will crush the star to ‘zero volume’, or in the Schwarzschild radius. This forms a black hole.

 As black holes, age, they gain more mass, as they suck in more matter

 A black hole cannot be viewed directly because light cannot escape it. However, matter swirling around a black hole, usually gas and dust, heats up and emits radiation that can be detected. However, deep in the center of a supermassive black hole, stars can also be found.

 On February 1997, the Hubble Space Telescope had a new instrument installed. Called the Space Telescope Imaging Spectrograph (STIS), this equipment is the main black hole seeker on the telescope. A spectrograph splits any incoming light using prisms and diffraction gratings into a rainbow. The STIS can measure ultraviolet, visible, and near-infrared wavelengths, allowing it to capture a wide range of places at once. The placement and intensity of the spectrum gives indispensable information to scientists. Every spectrum can be analyzed to find out the speed of which stars and gas swirl at a certain location. From this information, the mass of the object that the stars are orbiting can be found. A massive central object is found if the stars swirl quickly.

Conclusion:

Black holes are weird.

Work Citations:

http://en.wikipedia.org/wiki/Black_hole

http://cosmology.berkeley.edu/Education/BHfaq.html

http://www.universetoday.com/46687/black-hole-facts/

http://www.odec.ca/projects/2003/chowa3a/public_html/interesting.htm

Modern Physics

Ever since my childhood, I have always been fascinated by Physics. According to the definition of Wikipedia, Physics is a natural science that involves the study of matter and its motion through space time, along with related concepts such as energy and force. More badly, it is the general analysis of nature, conducted in order to understand how the universe behaves. The modern definition of Physics is a slight modification of the traditional definition, “The science of the properties and inter-relations of matter and energy.” (Oxford English Dictionary)

I got first introduced to the term Modern Physics after my tenth grade and found it even more interesting. The term Modern Physics refers to the post Newtonian conception of Physics. The term implies that classical descriptions of the phenomena are lacking, and that an accurate, “modern”, description of reality requires theories to incorporate elements of quantum mechanics or Einsteinium relativity, or both. In general, the term is used to refer to any branch of physics either developed in the early 20th century and onwards, or branches greatly influenced by early 20th century Physics.

And if there is one man who more than any other has come to be regarded as the personification of modern discovery in the field of physics it is the reputed giant among scientists – Albert Einstein.

Albert Einstein (1921-1955) Also referred as “Father of Modern Physics”

Albert Einstein played a large part in modern physics. He developed formulas that described the way matter and energy was related. Just about everyone has heard of the formula E=mc^2. That formula explains how energy is related to mass. The idea found its way into the study of fission reactions, and it was proved that enormous amounts of energy were stored in even one atom of a substance.

Even now, scientists are stilling testing the boundaries of physics and the laws of physics. Only a few years ago a new state of matter was created. The Bose-Einstein Condensate was theorized decades ago, but scientists have only recently been able to create it in lab. Everyday astronomers are studying space and learning how black holes and galaxies interact. Stephens Hawking is one of the more famous scientists working in that field.

Stephen Hawking (Theoretical Physicist and Cosmologists)

In “A Brief History of Time” , one of the most successful non-fiction books published in this century, Stephen Hawking relates how far scientists have progressed in this, and his own considerable contribution. Amongst other results, he and Roger Penrose showed that General Relativity implies that at some point in the past, the universe had zero volume and infinite mass density. This point would represent the beginning of time.
And the study continues to go continue.
These are generally considered to be the topics regarded as the “core” of the foundation of Modern Physics.
1. Atomic Theory
http://en.wikipedia.org/wiki/Atomic_theory
3. Franck-Hertz experiment
http://en.wikipedia.org/wiki/Franck%E2%80%93Hertz_experiment
4. Geiger-Marsden experiment
http://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experiment
5. Gravitational Lensing
http://en.wikipedia.org/wiki/Gravitational_lensing
6. Michelson-Morley experiment
http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment
7. Photoelectric effect
http://en.wikipedia.org/wiki/Photoelectric_effect
8. Quantum thermodynamics
http://en.wikipedia.org/wiki/Quantum_thermodynamics
10. Perhelion precession of Mercury
http://en.wikipedia.org/wiki/Tests_of_general_relativity#Perihelion_precession_of_Mercury
11. Stern-Gerlach experiment
http://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experiment
12. Wave-particle duality
http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality

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