Spooky action at a distance -Quantum Entanglement

          Quantum Entanglement: Spooky action at a distance as called by Einstein.

   In a Vague way, it says communication can occur faster than the speed of light hence the word ‘spooky’, as special relativity told us that nothing can travel faster than C(speed of light =3x10⁸m/sec).
  It is works on principle that result of a system depends on method or way of measurement. This is Quantum mechanical law and is not applicable to Classical mechanics (Newtonian mechanics- daily life phenomena).
If this does not confuse you, go back and read it again. Confused? Yes! How can an experiment’s result depend on way of observation?? 

Let’s bring in our favorite Schrodinger's cat, in this experiment, cat is in superposition state of being both dead and alive unless we open the lid and make a measurement, then on it will be either dead or alive.

Quantum Entanglement can be explained by this experiment. We need 2 cats in 2 different boxes such that the quantum states (here being dead or alive) are entangled, that is if one is alive other will be dead.

Let us use 2 methods, be it method 1 and method 2.

•        Our method of measurement affects the result or changing the property being measured alters the result.
•        Measurements affect each other.

METHOD 1	METHOD 2
0(Dead)	N(Dead)
1(Alive)	Y(Alive)

States of cat in box 1:
On measuring the state of cat 1 using method 1, we obtained result 1 implies cat in box 1 is alive. Similarly method 2 gave us Y that is cat is alive in box 1. Now, if we come back and measure again via method 1, the probability of this result is 50% again, which means it can be either 1 or 0 though we got 1 before there is no assurance that we get 1 again, we could get 0 for same exact method of measurement, it can be seen that measurements influence each other.

States of cat in box 2:
When method 1 gave result 1 for cat in box 1, cat in box 2 gives result 0 for same measurement and when method 2’s result of cat in box 1 is Y, it gives us N for cat in box 2. Each time the result of Cat in box 2 changes instantly and is in accordance with result of cat in box 1, happens vice verse too.

Each cat may produce random results but when compared with each other they are always impeccably associated.
 It is as if they communicated, but these results will be accurate even when the boxes are placed cities apart.

•        Usually cats are replaced by particles such as photons, electrons and their quantum states being spin of the particle.
•        Measuring one will tell the Quantum state of other with complete certainty.
•        Quantum states of particles are indeterminate unless measured.
• 
  
• Quantum Entanglement is widely used in powerful computers, Quantum computation and Quantum communications; they can provide secure codes via quantum encryption.

Schrödinger’s Cat(Meow) !!

                                                Schrödinger’s Cat(Meow) !!

It is a thought experiment by Austrian Physicist Erwin Schrödinger; this experiment is an interpretation of Quantum Mechanics. It is principally based on Copenhagen interpretation.

Quantum Mechanics:
 It is a branch of mechanics that deals with behavior of atomic particles of high energy and low mass like an electron, proton etc. Tiny masses like electrons don’t obey newton’s laws, but we need some laws for them obey so that we know them better and can control them, these laws are found based on their behavior and belong to Quantum mechanics.
 For macroscopic objects, classical mechanical laws (Newton’s laws) are applied, these laws will not give results if applied on atomic particles in the same way, and we cannot apply Quantum mechanical laws on macroscopic objects.

Experiment:

             google's doodle on schrodinger's birthday!

Cat is placed in an isolated and sealed box such that we are unaware of anything happening inside it, there is also an unstable radioactive element that might disintegrate, if it does, this will be picked up by Geiger counter which in turn breaks flask of hydrocyanic acid via hammer. This possibility leads to death of cat; alternate outcome is the cat doesn't die as the radioactive element did not disintegrate. The probability of both the outcomes is 50% each.
Which state is the cat in? is it dead or alive?
By our common sense we know the cat can either be dead or alive but not both.  But sometimes common sense is not the answer, thinking is!

Here, Quantum mechanics says otherwise, it says the cat is in 2 states, both dead and alive as along as we don’t interfere in the experiment by checking it after an hour (or any specified time). This comes from the famous Schrödinger equation and Copenhagen interpretation.

Schrödinger equation expresses all the probabilities of possible states of the particle before it is verified; it basically gives us the idea as to what are the chances of finding certain particle in specific state at defined time.  It is hence called as probability wave equation as well.

Copenhagen interpretation:
It says what we have seen above, that probability of cat being dead or alive is remained in superposition (adding them up) until externally observed (takes one state after checking it).

In conclusion, atomic particles are in all possible states until measured, our action of measurement makes them chose a definite state. This experiment is even better understood with knowledge of Quantum entanglement (which will be shortly posted).

Note: Above said experiment is restricted to atomic domain, on macroscopic scale things turn to be definite. Cat is taken for simplicity and to make it easy for anyone to understand or perhaps he chose a cat because he lived with one, but in reality cat is an atomic particle (electron/photon) and box is usually their orbit,states are their spins.

The Man Who Knew Infinity

                                              The man who knew infinity

His birth date is celebrated as national mathematics day and he is known also as father of mathematics!!

Yes, he is Srinivasa Ramanujan. Born on 22 December 1887 in Erode, Tamil Nadu.
Ramanujan compiled nearly 3900 results which include identities and equations, of which most are proven correct. He showed great interest in field of mathematics at early age, his scores in math were higher. Ramanujan could not finish his diploma because he could not clear subjects as arts; he then dropped out of college. Suffered from various health problems mainly due to poverty, he was not offered admission into University college of London as his approach to subject was informal.

Later he sent his work to G.H.Hardy who is renowned mathematician in Trinity College Cambridge with the help of limited friends .Hardy was very much impressed by the depth and nature of the work but raised uncertain as this came from an Indian lacking formal education. Hardy acknowledged the letter and requested Ramanujan to come over to London, as he was a Brahmin and crossing waters was considered unacceptable, Ramanujan rejected his offer. He was offered a scholarship of 75 rupees per month, it helped him focus on his work, in his letter he stated to Hardy “to preserve my brains I want food and this is my first consideration”.

Ramanujan went to England in 1914 after he was convinced by his mother and wife. He on association with G.H.Hardy and Littlewood published various papers on highly composite numbers, elliptic functions, infinite series as well as refined his previous works.

Ramanujan is one of the youngest and 2^nd Indian to become collaborator of Royal Society in 1918, same year, he was also elected as fellow of Trinity College Cambridge (first Indian). His declining health because of cold weather and lack of vegetarian food during WW1(World War 1) forced him to return to India.

He was diagnosed of tuberculosis and breathed his last on 26 April 1920 at a mere age of 32. Exquisite films and books were published on his contributions to the field of mathematics and struggles that he overcame, most recent one being ‘The man who knew infinity’ was released in 2016. Books include ‘The Indian clerk’ by David Seavitt,’lost notebook of Ramanujan’, etc.

Hardy-Ramanujan number:

1729                                  

Hardy said “I remember once going to see him when he was ill at Putney. I had ridden in taxi cab number 1729 and remarked that the number seemed to me rather a dull one, and that I hoped it was not an unfavorable omen. "No," he replied, "it is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways."

       1³+12³=9³+10³=1729
it must be noted that positive cubes are considered and on inclusion of negative cubes leads to result of 91

Ramanujan believed that an equation didn’t make sense unless it expresses a thought of god, his works were worth a few lifetimes not just one. He earned his name as the man who knew infinity.

Think of an Anti-You(Matter and Anti-matter)

     Think about an Anti-you (Matter and Anti-matter)

Bizarre title isn't? Science is bizarre too

What is matter?

Matter is us; we are composed of centrally of atoms which have neutrons, protons and electrons which in turn has quarks (smallest particles discovered), hadrons etc. All of these are nothing but matter.
Word matter used in post can be substituted by proton,electron,neutron,quarks etc.

Anti-matter: it can be called as twin of matter; Anti matter has opposite charge to that of matter, rest all aspects (mass, spin etc.) are same for both. Every matter has it anti matter counterpart somewhere in our Universe.

How are they produced?

When we say space is empty, it literally is not empty but filled with huge amount of energy. Einstein’s famous equation E=MC² gives us idea about the conversion of matter and energy, matter and anti-matter pairs are produced from energy described above. Matter and Anti-matter must be produced in pairs so that law of conservation of energy is not broken.

Law of conservation of energy basically states that a charge (positive or negative alone) cannot be created or destroyed, however it can be created in matter and anti-

matter pairs (as charge of these two are exact opposites so net charge remains zero).

What happens when anti-matter and matter meet?

They certainly will not have enough time for a chat, they clash into each other violently and disappear leaving pure energy, and this energy is equal to amount of energy expended to create them. This process is called Annihilation of matter and Anti-matter.

Seconds after big bang

There should have been equal amounts of matter and anti-matter created as they are always created in pairs, if that is the case how are we still alive? Annihilation must’ve occurred long before formation of stars or galaxies yet we live in a matter dominated world.

Various theories are developed to account for this discrepancy, few of them are:

One pair in billions of matter Anti-matter pairs has survived this bulk annihilation; this one matter particle could’ve been accidentally separated from its counter-part (anti-matter) and these one in billion matter particles constitute the universe we know about.

Another theory says that a disturbance caused in fabric of space-time after big bang set off matter and anti-matter in opposite paths. According to this theory just like our world there could be an anti-matter world in some part of universe, it also says that anti-matter repels gravity (has not been proved) so we still exist. This allows us with a possibility of finding an Anti-You.

How real is anti-matter?????

Bananas produce anti-matter; they release one positron every 75 minutes due to decay of potassium.

Positron: anti-matter particle of electron, it has positive charge unlike electron but has same mass, spin, quantum numbers.

But all anti-matter produced is short-lived as it annihilates immediately on contact with matter and we live in matter dominated universe which just increases chances of annihilation. Anti-matter is a future fuel source as a gram of it can produce energy equivalent to that of nuclear bomb, backdrop we currently face is in production and storage of anti-matter.

MATTER PARTICLES	ANTI-MATTER
Quarks	Anti-quarks
Electron	Positron
Proton	Anti-proton
Neutron	Since it is charge less, its anti-matter particles is itself
Leptons	Anti-leptons

It may not be advisable to wish of meeting your counter-part (anti-you) for it will end up in annihilation.

Big Bang Experiment(Particle accelerator)- key to understanding our universe

  Particle Accelerators – key to understanding our universe

Stephen Hawking says particle accelerators are the closest mankind got to time machine! What are these particle accelerators? How do they work? Why are they so important?

Particle accelerators as the name suggests are used to accelerate particles (such as protons, electrons), they basically increase speed of particles and collide them with desired targets under intent observation to unlock properties of universe and create states that were present moments after big bang.  The concept of accelerators were introduced in 1930s, cyclotron being the first and basic one. There are more than 30000 operating accelerators around the world.

How do they work?

Particle accelerators aka atom smashers vary in sizes, the smallest being 5 inches in diameter and largest being 27 kms in circumference. World’s largest atom smasher is the Large Hadron Collider (LHC), it is beneath the France–Switzerland border near Geneva, Switzerland, and the famous big bang experiment was done here. CERN is the European Organization for Nuclear Research which houses the LHC.

Working of LHC (an particle accelerator)

Hydrogen atoms are fed into source chamber of LHC and then stripped off their electrons, as a hydrogen atom has 1 electron and 1 proton; they are now ionized hydrogen or Protons. Protons as we know are positively charged and electric field is applied such that these protons are repelled and hence accelerate (gain speed).

In the 1^st stage these packets of protons are travelling in a linear accelerator and reaching 1/3^rd speed of light.

2^nd stage is a booster; it is a circular accelerator and is 167m in circumference. Packets of proton are divided into even smaller packets to increase intensity and are distributed among rings of circular accelerator. Powerful magnets are used to bend the beam of protons so as to circulate in the ring; protons reach 91.6% speed of light. All the divided packets are combined and flung into proton synchrotron.    

3^rd stage is proton synchrotron (it is a larger circular accelerator), it is 628m in circumference and protons reach to 99.9% speed of light here. A transition stage is reached as a proton cannot exceed speed of light as formulated by Einstein’s theory.

     E=MC² plays a vital role here- Energy supplied henceforth is converted into mass of proton, as a result they get heavier not faster, protons in synchrotron are 25 times heavier than a normal proton at rest.

4^th stage is a super proton synchrotron; it is a huge ring of 7kms in circumference. Soon injected protons will be at precisely desired velocity to launch them finally into orbit of the LHC

In LHC

It has a circumference of 27 kms and contains 2 vacuum pipes;. Packets of protons are systematically injected into these vacuum metal pipes in clockwise and anti-clockwise directions in order for them to collide at specified detector junctions. Protons finally have energy of 7000Tev (10¹²electron volt) of energy and 7000 times heavier than at rest. Magnetic fields needed to bend these high energy beams is enormous, it is however achieved by maintaining temperatures colder than outer space inside metal pipes of LHC, this cold temperature allows for superconductivity(no or least resistance). 4 detectors cabins are positioned to track the impact and elementary particles (quarks, gluons etc.) produced in these super high energy (more than 14000Tev) collisions. Detectors are connected to super computers to analyze the particle tracks and the observations made are anticipated to give us insight into birth of our universe. Particle accelerators are also used for hunt on ‘God Particle’ (Higgs boson)

Time Travel through accelerator as said by hawking:

This is a hypothetical situation and not anywhere close to reality (we are faced by many physical restrictions). Imagine injecting a human instead of particle accelerated to such high speeds. When our human is out of ring, he/she is going to look years younger than the rest of us cause of time dilation from special relativity. Similar effect on protons in accelerator and their time runs slowly than ours.   

Big Bang theory,Story of our universe!!

                                     STORY OF OUR UNIVERSE-BIG BANG

Theory rose from a basic question, where did our universe start? Did it just sprung into existence or is it a continuous timeline of existence without end or beginning?

Countless theories have been developed to explain this, big bang is most profound and it’s hence stood out. It gives an idea about the beginning of time.

Expanding Universe

Astronomer Edwin Hubble had observed movement of galaxies closer to ours over years, in 1929 conclusions drawn from these observations presented astounding results. His observations indicated red wavelength Doppler’s shift.

Doppler’s shift

 Sound produced by vehicle coming towards you is clearly heard, as it passes you and goes farther, and then the pitch drops, this is an example of Doppler Effect. As the source (being vehicle here) is moving and not stationary hence there is a change in transmitted and received wavelength. Basically when something is approaching towards observer its wavelength is shorter and has spectrum color of blue, when moves away from observer reflected wavelength has spectrum color of red. So when Hubble saw red Doppler shift it led to conclusion that galaxies are moving away from ours.

Back to expanding universe

Important thing to notice here is, galaxies on all sides of earth are moving away. If galaxies that are forward or backward of Milky Way alone are moving away, we can conclude that universe is moving in one particular direction, but here galaxies in all directions(that is all sides of milky way) are moving away from us at speed of light.

For a closer picture, consider this experiment

 Take a deflated balloon; mark 5 dots on it using marker/pen. Now, blow that balloon, you can notice that all dots  are moving away from each other, no matter which dot you take as reference and observe, you can see that other dots are moving away from it. There by concluding that the balloon is expanding uniformly in all directions. Apply same phenomena to expansion of our Universe, dots here are galaxies and balloon is the universe. Similarly it’s established that universe is expanding at the speed of light uniformly in all directions.

THE BIG BANG

Stephen Hawking thought what if we rewind this? Going back in time same way (contracting universe), universe has been expanding and now we go back in time to the point where it all existed in immensely hot (millions of degrees), extremely dense point which is a singularity (yes, the one in black holes).

Predictions say it took millionth of a millionth of a second for big bang to occur, this singularity’s density was too much to handle anymore and too hot as well, it burst out with a big “bang”, bang is from the expression used to describe sound produced in explosions, this is the biggest and most violent explosion in the history of universe.

Few seconds after big bang: 

Initially protons, electrons and neutrons were moving at such great speeds (due to very high temperatures) that they could overcome attractive forces, so no matter was formed. Within few seconds it cools down enough for nuclear forces to take over and form atoms. On cooling further over years, weak force such as gravity could also take over and lead to formation of planets, stars and galaxies.

E=MC² Energy mass conservation

It plays a vital role in explaining formation of matter from big bang theory, this blast had unimaginable amount of energy, which was converted into matter eventually as the temperature decreased.

Explosion of this magnitude sets of huge amount of radiation, and this radiation exists till today. In 1964 Arno Penzias and Robert Wilson accidentally picked unknown background radiation which is now called cosmic microwave background radiation (they won Nobel Prize for it in 1978) and it is proof of a consequence expected from big bang. We are exposed to this radiation everyday of our lives and it’s below harmful level and yet good enough for detection. This is most widely accepted story of our universe.

Travelling to a parallel universe via Wormhole

                         Parallel Universes via Wormholes

Ever thought about how big is our universe?

Best estimates of astronomers indicate 100 billion galaxies; Andromeda galaxy is closest one to ours and is 2.5 million light years away.

One light year is how much light can travel in vacuum within 365.25 days (1 Julian year)

Which is,   distance =speed x time

                   Distance = (3x10⁸(m/s)) x (365.25x24x60x60(s))

                 Distance =946728x10⁷kms or 9.467e⁺¹²kms =1 light year

You can imagine how gigantic our universe is!

Scientists have a theory that we are living in a multiverse, as per this theory ours is not the only universe, rather many universes exist parallel to each other and these are called parallel universes. They are anticipated to be similar but not same (with very few changes).

We agreed on our universe being enormous (taken into infinity), added to it are infinite parallel universes. Too Hard to picture!

Wormhole: it is a hypothetical concept (no proves found yet) and is like a tunnel through the space time or like a short-cut. 

White hole: It releases matter outward unlike black hole that sucks it in. Black hole ends at a singularity and white hole is born from singularity.

Entering a wormhole can be familiar to black hole (black hole + white hole could make up worm hole) and exiting it leads to 2 set of predictions

A)  Exiting in the same universe you entered but at a completely different space-time as shown in down imagine. So if there is a wormhole between our galaxy and Andromeda galaxy, and it is stable enough for interdimensional travel. I will be able to reach Andromeda galaxy within few minutes or hours(definitely less than 2.5 million light years) And therefore I even travel in time, that is travel to future (my friends on earth and I will experience time dilation due to me passing through wormhole  which is warping of space-time) 

B)  Exiting into a parallel universe as shown in first image. As in case of Alice in wonderland.

Our universe started off with a ‘Big Bang’ and is expected to end in a ‘Big freeze’. Few scientists hope that this can be avoided by hopping into a parallel universe.

The bridge of wormhole connecting two places is called Einstein-Rosen Bridge. Einstein believed that any communication through the bridge would be impossible, but recent studies show it hard but perhaps probable.

Amount of matter-energy needed to create wormhole is immensely large and it would still be highly unstable and disappear in wink of an eye, making it impossible to use it as an interdimensional travel.

So if you are bored of this universe, you may be lucky enough to travel through universes for some adventure in a future, if you live long enough by that i mean few centuries and when these theories turn into laws.

Black hole an interesting ambiguity !!

                                                              BLACK HOLES

Biggest one of many mysteries of Universe, can’t be seen can only be detected by changes in the surrounding space-time fabric. As the name suggests they are black and can be similar to hole formed in the space-time fabric. 

Ever wondered why they are black?

Objects can be seen only if they reflect light; well in case of a black hole its gravitational pull is very intense that even particles moving at 3x10⁸m/s or light cannot escape. Escape velocity of earth is 11.2km/sec. Black hole occurs where there is immense mass in small volume, we know from Einstein’s theory of relativity that more the mass , more the warping of space-time, and more the gravity.              

To give an idea of mass contained in a black hole, shrinking the earth to size of golf ball without removing any of its mass gives us a small black hole.

HOW ARE THEY FORMED?

 Dying stars whose mass is 20 times mass of sun or more form black holes. Stars shine due to enormous amount of heat liberated in nuclear fusion process. Stars are formed from condensed gases (mostly hydrogen nucleus ), these gases are stay put due to gravity which is also powerful  enough to crush the star. But these hydrogen nuclei gets fused together to form helium and thereby releasing large amounts of energy (E=MC²), this process is called nuclear fusion and this energy released tends to explode the star. As a result, gravity and nuclear fusion in star’s core are at a war, till the core of star runs out fuel and gravity Wins. Fate of the star hence forth is decided by its mass, in case of black holes we focus on super massive stars, gravity crushes the star aiming to form a singularity (infinite mass at one point).

Black holes are primarily of singularity within and an event horizon. Event horizon is also called “The point of no return”, because once you enter beyond this event horizon black hole sucks you to singularity and is impossible to escape its tug. 

WHAT IS IT LIKE TO FALL INSIDE A BLACK HOLE?

Time slows down inside a black hole, and at singularity time stops, laws of physics as we know, breaks down. Assume an unfortunate astronomer falls into a black hole, he will not realize it until he passes event horizon. Now, he undergoes a process called spaghettification(being stretched like a spaghetti) that is, gravitational pull at his head and feet is not same, it would stretch him and tear him apart. To his friends in spaceship orbiting the black hole, it appears as the astronaut slowed down and stopped at the event horizon, his time stops here.

Just for the sake of fun, we assume he overcame this spaghettification process and manages to reach center of black hole alive. Here starts our science fiction(interstellar, star trek, star wars), unproved theories(hypothesis), it could be a gateway to another universe, you could visualize present, past and future at once, time travel could be possible and much more.

DID U KNOW: There is a massive black hole at the center of our own Milky Way galaxy; as a matter of fact every galaxy has a black hole at its center. They are capable of destroying entire galaxies 

General Relativity simplified

GENERAL RELATIVITY

This theory spins around gravity; it is like an extension to special relativity by counting gravity too. Einstein developed it fundamentally based on equivalence principle

EQUIVALENCE PRINCIPLE:

Imagine being locked up in a closed container like an elevator with opaque walls and you are given a tennis ball. As you bounce the ball it touches floor of elevator with acceleration of 9.8m/s (earth’s gravity) as anticipated.

Now your elevator has a fuel tank or you were actually in a rocket, which is accelerating at 9.8m/s (32 feet/sec). When ball is bounced at the moment, what would happen? Would it be same as before?      

Yes to you it would just appear to hit the bottom as before because your body is also accelerating with 9.8m/s. But for an outside observer, it would be the floor accelerating at 9.8m/s towards the ball.

You are shielded inside and you cannot tell if its gravitational frame’s work or accelerating frame’s work that causes ball to touch the floor. In other more scientific and confusing words: laws of physics are same in accelerating (non-inertial) and gravitational frame (inertial) of references, this is called equivalence principle.

Combination of equivalence principle with its analogue in pure mathematics leads to formation of Einstein’s theory of gravitation. (This alone deserves another blog post)

GENERAL RELATIVITY: back to main topic

Einstein’s mathematics consists of 4 dimensions (3 spatial dimensions and 1 time dimension) also called space-time relations. He said “space itself is curved”.

Imagine a rock placed on a spread blanket, there is a depression caused by placing the rock, now a marble shot into blanket will follow an elliptical path around the rock. In analogy, blanket is the space-time fabric, this distortion is formed by matter is called warping of space-time (curving of space time). Imagine is a reference to warping

Proving this:

Light always chooses the least time taking path (hence it’s always straight line), when passing objects as sun (heavy objects that cause warping) light beams bend and the shortest distance it chose being a curved line, articulate us that space-time fabric itself is curved. This phenomena of bending of light is called gravitational lensing

Due to gravitational lensing of sun, light from distant stars is bent and we receive multiple apparent images of them. This was proved during 1919 eclipse; measures of distances of stars were taken at night (absence of sun) and during eclipse (so that sun’s light wouldn’t overwhelm star’s light). Observations obtained were close to Einstein’s theory predicted values. Einstein’s theory overcame, many limitations in newton’s predictions, though it had its own set of difficulties in mathematics domain.

E=MC²

Heard about it too often! But what does it signify?

As Energy is supplied to a particle, it increases its velocity thereby increasing its kinetic energy and mass. This extra mass emanates from energy supplied, it’s also another perspective into saying speed of light is not achievable; as the particle reach speeds close to speed of light, energy supplied is converted to mass gained by the particle.

E=MC² implies

MATTER is condensed form of ENERGY, a storage unit of energy. 

Insignificant amount of matter can generate loads of energy as mass is multiplied by speed of light squared (which is a huge number).

In conclusion: As matter-energy is more ─> curvature of space-time fabric increases hence more the gravitational tug.                    

 Einstein’s relativity theories led to foundation of principles behind motion of black holes, stars, big bang etc.

Special relativity simplified to its best

                    SPECIAL RELATIVITY

Special relativity postulated by the genius Albert Einstein                                                                                         

Relative velocity

To understand this spooky topic in a simplified and easier way lets clear out topic of relative velocity

Assume We both are on a flight (why train always?) just sitting there and having ice cream, so our both velocities are same and are zero with respect to each other (can also be said as relative to each other). Same case, now when our velocities are considered with respect to the ground(frame of reference is ground)we are in motion with a particular velocity( relative to the ground) and a different velocity when frame of reference is another plane flying across ours cause the velocity of that plane is subtracted from ours . so basically relative velocity pronounces  that speed with which we are moving varies with respect to our frame of reference (hence comes word relative) and also that space is not absolute.

Frame of reference:to the above Paragraph, it is from where one is calculating plane’s velocity

Back to main topic: SPECIAL RELATIVITY

Bottom line of this theory says Speed of light is constant for every observer. Okay I have been listening to this from really long time, what’s spooky about this?

Let me expand and confuse you a little more before clearing it out

For a space ship ‘A’ moving with speed of 2x10⁸m/s  and another space ship ‘B’ moving with speed of 1x10⁸m/s the speeds of light beam travelling parallel to them must be

For A  (3-2)x10⁸=1x10⁸m/s

For B (3-1)x10⁸=2x10⁸m/s  in accordance with relative velocity

But in reality it’s found out to be 3x10⁸m/s for both……does it seem absurd now? Now this appears to defy the concept of relative velocity.

In conclusion speed of light is always constant compared to anyone moving at any speeds, does it now make sense as to why you can’t beat this speed? Because when a particle moves closer to speed of light, light still passes that particle at 3x10⁸m/s.

Okay, all this is cool, but how can it be same?C'mon Something has got to change!

Yes, time compensates it.

TIME DILATION comes to play here.

TIME DILATION:

This basically says that racing of time depends on velocity, the faster you move slower your time runs. As you move with speeds closer to speed of light your time slows down, congrats you will age slowly than your peers. You will have more time in your hand. Same principle is used with various examples, most common one being a pulse bouncing off between 2 surfaces. Similar thing happens with length and this phenomenon is called length contraction.

If you hate Justin Bieber, you might be lucky enough to travel across space at speeds closer to speed of light and come back after a few minutes, few minutes is according to you, but for us on earth it would’ve been years-this is also the main principle of twin paradox(All these paradoxes will be put on soon)

In conclusion:

Special relativity is about speed of light being absolute and constant, doesn’t matter speed of observer, because pacing of time is altered.

Note: Difference between Special relativity and General relativity is that special relativity does not take gravitation into consideration unlike General relativity

And precise value of speed of light is 299792458 m/s