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Is there any difference between antimatter and dark matter?

Anonymous asked :Is there any difference between antimatter and dark matter?

Answer:Anti matter is just like normal matter only the sign of certain properties is different.  The classic case would be the electron, which has as it's anti particle the anti-electron also known as the positron.  Electrons are negatively charged, and Positrons are positively charged.  Yet they are identical in every other way.    Then their are particles like neutrons and protons which are made of even smaller particles called quarks.  Quarks interact via the strong atomic force, and electromagnetism.  Anti Quarks have opposite charges to Quarks in those two forces.

Dark matter on the other hand only interacts by way of gravity and the weak atomic force.  Dark matter does not interact via either the strong atomic force or electromagnetism hence dark matter cannot be seen and is hard to detect.  It only interacts via the weak force which is what keeps neutrons and protons inside the nucleus of atoms together.    Such is why experiments to detect dark matter directly rely on a particle of dark matter bumping into a particle of matter dead bang on the nucleus of an atom of normal matter.

Most of the reason we think dark matter exists has to do with the fact that it solves problems in cosmology in a very expedient way without us having to alter General Relativity.  It is widely agreed that dark matter whatever it turns out to be quantifies how much we really don't know about the matter in the universe.

Negative matter is a hypothetical type of matter which if it exist will have negative mass and negative energy.  It will in essence have a negative gravitational charge and repel normal matter.  Yet it will interact just like any other matter in every other way.
 Normal Matter Anti- Dark- Negative- 
Gravity  As usual As usual* As usualOpposite sign 
Electromagnetism As usual Opposite sign No charge ?
Strong Force As usual Opposite sign No charge ?
Weak Force As usual Opposite sign As usual ?


*We assume that antimatter behaves as normal matter under gravity.  The truth is we have never seen a large enough mass of it to know for certain it behaves the same.  When it comes to Negative matter we know nothing and it may not even exist outside of certain theories.  Dark matter is on the edge of being a confirmed real entity.

XI Physics: Guess Paper / Impotant Questions 2013

For Board of Secondary Education of Karachi




XII Physics: Guess Paper / Impotant Questions 2013


For Board of Secondary Edacation of Karachi(BSEK)

The Physics Of Basketball




basketball shot




Physics Of Basketball — Hang Time
Jumping is a major component of the physics of basketball. When a basketball player jumps in the air to make a shot he can appear to be suspended in mid-air during the high point of the jump. This is a consequence of projectile motion. When an object is thrown in the air it will spend a large percentage of time in the top part of the throw.

A basketball player can jump as much as 4 feet in the air (vertically). And the higher he jumps the greater the hang time (the total time he is airborne), and the greater the time he will appear suspended in mid-air during the high point of the jump.
parabolic curve for physics of basketball
Typically, there is a horizontal and vertical component in the jump velocity at take-off. The magnitude of the vertical component of the velocity at take-off will determine the time the player spends airborne (since gravity acts in the vertical direction and will act on the player to bring him back down). Thus, the vertical component of velocity, after take-off, will change with time.
The horizontal component of velocity remains constant throughout the jump since it is not affected by gravity.
The figure below shows the typical trajectory a basketball player might travel as he makes a jump.

You can visually see that almost half the hang time is spent near the top of the arc.
Using some mathematics one can calculate the time spent in the top part of the jump.
The following formula is used for linear motion with constant acceleration:
d = V1t — 0.5g(t)2
Where:
d is the vertical jump distance
V1 is the vertical component of jump velocity at take-off
t is time
g is the acceleration due to gravity, which is 9.8 m/s2

Maximum jump height is reached at t = V1/g.
Using the above formula for d, the maximum height reached is
dmax = (V1)2/(2g).
Now, set t = V1/(2g), this is half the time it takes to reach maximum height. Call this time thalf.
Using the above formula for d, the height reached during thalf is
dhalf = 3(V1)2/(8g).
Now, calculate the following ratio:
dhalf/dmax = 0.75
This interesting result tells us that half the hang time is spent in the bottom 75% of the jump. The remaining time is spent in the top of the jump (the top 25% of the jump). In other words, half the jump time is spent in the highest 25% of the jump (the top part of the arc). This explains why a basketball player appears to "hang" during the jump.
So, a player who can jump 4 feet vertically will have a hang time of around a second, with half a second spent in the high part of the jump.

Physics Of Basketball — Backspin
backspin for physics of basketball

Backspin is used by players to improve their chances of getting the basketball into the net. When an object is spinning and bounces off something, it will have a tendency to bounce in the direction of the spin. This is useful for players who bounce the ball off the backboard, or the back of the net. The resulting bounce will more likely send the ball downwards into the net. Without backspin the ball is more likely to bounce away from the net.

Introduction to Fourier Optics 2nd - J. Goodman





Book Description

Fourier analysis is a ubiquitous tool that has found application to diverse areas of physics and engineering. This book deals with its applications in optics, and in particular with its applications to diffraction, imaging, optical data processing, holography and optical communications.

Statistical mechanics of nonequilibrium liquids - Evans , Morris





Book Description

In recent years the interaction between dynamical systems theory and non-equilibrium statistical mechanics has been enormous. The discovery of fluctuation theorems as a fundamental structure common to almost all non-equilibrium systems, and the connections with the free energy calculation methods of Jarzynski and Crooks, have excited both theorists and experimentalists. This graduate level book charts the development and theoretical analysis of molecular dynamics as applied to equilibrium and non-equilibrium systems. Designed for both researchers in the field and graduate students of physics, it connects molecular dynamics simulation with the mathematical theory to understand non-equilibrium steady states. It also provides a link between the atomic, nano, and macro worlds. The book ends with an introduction to the use of non-equilibrium statistical mechanics to justify a thermodynamic treatment of non-equilibrium steady states, and gives a direction to further avenues of exploration.

Q.According to relativity Moving clock ticks slow..i have 2 much confusion to understand this statement as well time dilation

Savera asked:
Q.According to relativity Moving clock ticks slow..i have 2 much confusion to understand this statement as well time dilation

 Answer:Sure let us consider that You are "at rest", and there's a rocket going past you, and a person on the rocket is holding a clock, a flashlight, and a meter stick oriented in the direction of travel. You also hold a clock, a flashlight, and a meter stick.

You see a one-meter-long stick, and a clock ticking at one tick per second, and you see the light traveling at the speed of light.


The person on the rocket also sees his stick as one meter long, the clock ticking at one tick per second, and the light traveling away at the speed of light.


But, when you look at the rocket, you see a meter stick that is shorter than a meter, and a clock that is ticking slower than one tick per second, but the light from the flashlight is still traveling at the speed of light. 


It turns out that the person on the rocket sees the same thing when he's looking at you. The stick is short, the clock is slow, but the light is traveling at the speed of light. What this means is that either frame can be the "rest" frame, and the other would be the "moving" frame, so there is no absolute reference frame, so everything is relative.


Note, the differences are extremely small unless the "rocket" is moving at a significant fraction of the speed of light. So in your example, there's hardly anything to notice. But if flashlight is moving at, say, 0.5c, both you and the moving observer see the light traveling at the speed of light, but you would see the meter stick as 0.866 meters long, and each second on the moving clock would take 1.15 seconds of your time.


This may all seem counterintuitive, since you're accustomed to speeds adding arithmetically. However, the above describes how the universe actually works.



Also understand that we measure time with electron clock in which an electron is emmited from a surface and when it comes back it is regarded as one second.so when a body travels at a speed near to speed of light then it will take a larger time to come back...so time moves slow.  (as shown in the figure above)

Quranic Explanation of Wormholes

Look up to the night sky and select a star as a destination. Can any human reach this star by just walking few steps? General relativity explained a mechanism to contract huge distances into few meters. Albert Einstein called this mechanism ‘bridges’ in space-time.

Today, scientists call them wormholes.
A wormhole acts as a shortcut connecting two distant regions in the universe.

God gave this method of transportation to his angels throughout the universe. The Quran calls them ‘Ma'arej’ (معارج) and describes how angels use them for long distance travel. Today Moslems know that these ‘Ma'arej’ is what scientists call wormholes.

Physicists know how a wormhole works but have never actually used one. Do you remember how a frictionless roller coaster works? That is, you start high and slow then you go down and fast but when you come back up again to your previous height you return to your previous slow speed? Well, the wormhole is the most efficient roller coaster you can imagine. Energy is not required to move through the wormhole, that is, you can simply switch off your rockets. Gravity accelerates you and pulls you through and then expels you the other side. You will feel like being swept by waves at the beach; nothing more. On your way through, gravity causes your clock to run slower and your ruler to shrink. Distant observers see you accelerating to relativistic speeds; as a result, your energy (and mass) increase dramatically in their view; but when you get out the other side everything returns back to normal (your clock, ruler...).
[Quran 70.1-4] Someone asked about the penalty that will befall the unbelievers; (A penalty) that has none to ward off; (a penalty) from Allah (who owns) wormholes [Ma'arej in Arabic] The angels and the Spirit ascend to Him in a day, the measure of which is fifty thousand years.
\Any object passing through this wormhole will also experience this same time dilation (one day inside wormhole vs. 50,000 years on Earth) and not just those angels. This time dilation does not say how long it takes you to cross the wormhole, it just says that when you pass through the wormhole you age by this ratio.
Moslems also believe that wormholes are not strictly for the use of angels. Their prophet used a wormhole once in the ‘Israa & Mi'raj’ (Mi'raj معراج is singular of Ma'arej)

God says that those wormholes are doors in the heaven that contract interstellar distances into walking distances; the resulting scenery is bizarre: God says that those who do not believe in the message will not believe it even if He showed them a bigger sign. He created beautiful towering structures in the heavens. If He opens for those nonbelievers a door in heaven and lets them continue passing through it to those distant structures, they would not believe that they really got there by simply walking few steps. Instead they would think that they are just optical illusions:
[Quran 15.13-17] They do not believe the Message, like those who preceded them; Even if We [Allah] opened upon them from the heaven a door and they continued passing through it they would say ‘Our sight is bedazzled, rather we have been bewitched’. It is We [Allah] who have made towering structures in the heavens and made them beautiful for beholders. And We protected them from every evil spirit accursed.    
Here, they wouldn’t believe their own eyes thinking that what they see is not real. They wouldn’t believe that they got to those heavenly structures by simply walking few steps. But God insists that what they see is real and not illusions (that is, they really got there).
[Quran 21.104] On the day when We will fold the heaven, like the folder compacts the books, and as We originated the first creation We shall return it; a promise (binding on Us); surely We will deliver.
Here God promises to make the Big Crunch not by gravity but rather by folding the Heavens like a book, that is, by the same mechanism He controls wormholes. This means that this Big Crunch can begin and end in a fraction of a second!


An Introduction to Wormholes

Principles Of Nonlinear Optics - Y. R. Shen




Book Description

A comprehensive treatment of nonlinear optics emphasizing physical concepts and the relationhip between theory and experiment. Systematically describes a number of sub-topics in the field. Up-to-date references and numerous illustrations will help both beginners and practitioners interested in gaining a more thorough understanding of the subject.

Fundamentals of Statistical And Thermal Physics - F. Reif

 

  




Bibliographic information

Statistical physics - Isihara A.

Quranic Explanation of Pulsars & Black Holes

Neutron stars are remnants of exploded stars. As more matter falls into a neutron star its mass increases; and as its mass increases its gravity increases. A point will be reached where gravity would have grown so much that not even light could escape, thus a black hole forms. Most neutron stars discovered today are in the form of radio pulsars. They are called radio pulsars because they emit radio waves. We can simply connect a radio telescope to a loud speaker and hear a pulsar. Pulsars sound like someone persistently knocking. Click here and listen to a slow knocking pulsar. Click here and listen to a fast knocking pulsar. So in short, we can hear a pulsar knock; and if matter continues to fall into this pulsar a black hole will eventually form. Moslems say that this is what Allah says. The Quran describes a star by "The one who knocks" and says that it is "The one who makes a hole".
[Quran 86.1-3] And the heaven and the "Knocker" (Tarek in Arabic) How could you know about the "Knocker"? The piercing star (Thakeb in Arabic).
The Arabic word "Thukb" means a hole; "Thakeb" means the one who makes the hole. The Quran is describing a knocking star that makes a hole.
How could an illiterate man who lived 1400 years ago have known that a star can make a hole?
God swears by celestial bodies that are invisible, that move, that sweep:
(Quran 81.15-16) I swear by those that are invisible (Khunnas خنس), that move, that sweep.
Satan is invisible and is described in Arabic as "Khannas" (Quran 114.4). The Quran uses the same word "Khunnas" to describe the celestial bodies that are invisible. All celestial bodies have gravity and can sweep everything in their way but the only ones that are invisible are blackholes.
(Our sun is a very small star. Actually our solar system (including the atoms that you are made of) came from a dying star 100 times more massive than our sun. Some stars are even bigger than our solar system, so you can imagine how large stars are.

Quranic Explanation of Big Bang and Big Crunch

 
After the Big Bang the universe was primarily Hydrogen, Helium and a tiny bit of Lithium. However when a gas is too hot it becomes ionized (loses the electrons) and becomes opaque (like today's smoke). In the beginning the universe was opaque to visible light (non-transparent). After 380,000 years the universe cooled enough and it became transparent to visible light. For other wavelengths it was opaque for a billion years. So "Let there be light" turned out to be false. However the Quran correctly said that at the beginning it was SMOKE, that is, a hot non-transparent gas:

[Quran 41.11] Then He directed himself to the Heaven when it was SMOKE, and then said to it and to Earth: "Come willingly or by force" they said "We do come willingly"
How could an illiterate man who lived 1400 years ago have known that it was just smoke after the Big Bang?
The universe was created in a Big Bang 13.7 billion years ago, is still expanding today, and billions of years from now it might recollapse by its own gravity with a Big Crunch (or continue expanding forever, Big Chill). Moslems say that this is what Allah says. The Quran says that on the first day of creation, God made the heavens and the Earth meshed together, tight and compact (Big Bang), continues to expand it into the universe we know today and at the last day God will recompress it into its original state (Big Crunch). About the first day (Big Bang), Allah says:
[Quran 21.30] Do not those who disbelieve see that the heavens and the Earth were meshed together then We ripped them apart? And then We made of water everything living? Would they still not believe?
In the Quran the Heavens expanded from a single point.
Cosmologists just confirmed the existence of "Dark Energy", a mysterious repulsive force that acts in opposite to gravity. As the distance increases, the attractive gravitational force decreases but this mysterious repulsive force increases. This repulsive force is pushing galaxies apart; the greater the distance the greater the repulsion. Scientists today do not know what this "Dark Energy" is, but they know that it is causing the entire universe to expand at an increasing rate.
[Quran 51.47] And the heaven, We built it with craftsmanship and We are still expanding.
The Quran told us about this expansion 1400 years before it was discovered.
There are three possibilities to how the universe could end: Big Crunch (Quran), Big Chill and the Big Rip. NASA recently ruled out the third scenario (No Big Rip; see also: Universe Today). This leaves the universe with only two possible endings: Big Chill or Big Crunch, depending on what this Dark Energy turns out to be. Learn more: Expansion of Universe in Quran. In the Quran God promises to make the Big Crunch:
[Quran 21.104] On the day when We will fold the heaven, like the folder compacts the books, and as We originated the first creation We shall return it; a promise (binding on Us); surely We will deliver.
Here God promises to make this Big Crunch however not by gravity but rather by folding the Heavens like a book, that is, by the same mechanism He controls wormholes. This means that this Big Crunch can begin and end in a fraction of a second!
Also after this Big Crunch is over, God promises to recreate those heavens and Earth once more before Judgment Day:
[Quran 14.48] On the day when Earth will be swapped by another Earth and so will be the heavens; and all (creatures) will resurrect before the One Dominant God.
[Quran 36.81] Is He not, who created the heavens and the Earth, capable of creating others like them? Yes, indeed! He is the All-Knowing Creator. His command, if He wanted a thing, is that He only says to it, "BE" and it becomes! So glorified is He in whose hands is the dominion of all things, and to Him you shall be returned.

Quranic Explanation of Kepler's Law

Orbits
For centuries it was believed that Earth is fixed and the sun, moon and planets revolve around it. However 1400 years ago the Quran said that not only the sun and moon but even Earth moves in a designated path:
[Quran 39.5] [Allah] Created the heavens and the Earth in truth. He overlaps the night over the day and overlaps the day over the night, and enslaved the sun and the moon, ALL MOVE (Kullon Yajree كل يجري) to a prerecorded destiny. Is He not the Exalted, the Forgiver?
Here the Quran is referring to ALL MOVING: not only the sun and moon but also Earth. In Arabic grammar there is difference between the singular (one), binary (two) and plural (three or more). The reference to binary is "Kulahuma Yajreean كلاهما يجريان" however the Quran said "Kullon yajree كل يجري" referring to the plural (three or more). Since the sun and moon are just two but the Quran refers to three or more then according to the Quran all the three move: sun, moon and Earth.
Moslems ask how could an illiterate man who lived 1400 years ago have known that Earth moves?

Quranic Explanation of Singularity

All stars will eventually die. They will either directly collapse on themselves and become black holes, or their remnants will merge with other stars that will eventually become black holes, or if external mass falls into those remnants they will blow up and leave black holes... So black holes are the destiny of most stars. Actually our solar system formed out of debris of a star 100 times more massive than our sun that exploded and became a black hole.

Singularity
At the center of black holes (collapsed stars) lies a location called the Singularity. An observer far away from a black hole sees the events near a back hole in slow motion. If he shines a beam of light into this black hole he will have to wait forever but still this beam of light will never reach the singularity. The singularity is a location in the future of stars where gravity goes so mad that space and time become indistinguishable. From general relativity we know that this is a location where the structure of spacetime becomes singular (hence the name singularity). However singular (Ahad in Arabic) is one of God's 99 names. In the Quran God swears by the locations of stars which turned out to carry His own name:
[Quran 56.75-77] I swear by the locations of stars, it is a great swear if you knew, it is a noble Quran...
Here God swears not by the stars themselves but rather by their locations (mawakeh in Arabic). Today we know that the future of those locations is singular, that is, they carry God's own name: "Ahad".

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