Thursday, 31 August 2017

25 Insane Optical Illusions That Will Leave You Dazed And Confused

The world is full of optical illusions and things aren’t always the way they appear. Although our mind is constantly trying to make sense of the world around us it can sometimes get a little out of control and make us start to see things…literally. While, some of the optical illusions on our list are relatively famous, others are a bit more obscure but all of them give us a glimpse into our amazingly complex minds. There is no magic involved, no strings attached, its all in your head. Here are 25 of the most incredible optical illusions you will find.


25.Rotating Rings





If you stare at the dot in the center and move your head away from the screen the rings will start to rotate. Now gradually get closer again…they change direction!


24

Hermann Grid



This is a classic optical illusion named after Ludimar Hermann who discovered it in 1870. At every point where the white lines intersect our eyes perceive a gray, shadowy blob. If you look directly at one of the intersections though, the blob disappears.

23

Fading Image

23
Stare at the image for about half a minute without moving your eyes and watch as it gradually disappears. This is a variation of Troxler’s effect which essentially says that if you fixate your eyes on a certain point, stimuli near that point will gradually fade.

22

Kanizsa Triangle

22
The Kanizsa Triangle was named after the psychologist Gaetano Kanizsa who first described its effect. When you look at the image your brain creates contours (outlines) of a triangle although none exist. In reality it is an illusion created by the the wedges and the angles.

21

Blivet

21
This is one of the most famous optical illusion pictures of an impossible object. It has two rectangular prongs at one end that morph into three cylindrical prongs at the other.

20

Monster Illusion

20
Found in virtually every psychology textbook in the world, the two monsters in this optical illusion are in fact the same size. Your brain automatically adjusts images that it perceives to be distant in order to compensate for the fact that they are larger than they seem.

19

Jastrow Illusion

19
Named after Robert Jastrow in 1889, the bottom figure appears to be larger although they are both the same size. This is because the shorter edge of “A” is directly adjacent to the longer edge of “B”.
18

Fraser Spiral

18
First described by British psychologist James Fraser in 1908, this illusion is also known as the “false spiral”. While it appears that the overlapping arcs are spiraling into infinity they are in fact only a series of concentric circles.

17

Scintillating Grid

17
This is a variation of the Hermann Grid where black dots appear and disappear at the intersections of the gray lines. Interestingly enough, if you cock your head at a 45 degree angle the effect is reduced (but not eliminated).

16

Blue vs Green

16
There are several variations to this optical illusion but the effect is the same. The “blue” and “green” backgrounds are in fact the same color (open it in photoshop).

15

Endless Staircase

Endless Staircase
This is a variation of the endless staircase optical illusion constructed out of legos. Like the the blivet, this is also an impossible object and is sometimes called the “Penrose triangle”.

14

Black on White

14
Stare at the center of the image for about 30 seconds and then look away at a preferably white surface (sometimes the ceiling works). What do you see?

13

Zöllner Illusion

13
This optical illusion was named after Johann Karl Friedrich Zöllner and consists of parallel lines that appear to be diagonal. You may need a ruler for this one.

12

Hering Illusion

12
Although the two red lines seem to be bowed outwards they are perfectly straight and parallel. This optical illusion is attributed to Ewald Hering, a German physiologist who believed that the distortion was derived from the mind overestimating the angles at the points of intersection.
11

Titchener Circles

Titchener Circles
Also known as the Ebbinghaus Illusion, there is still a debate in psychological circles as to the exact mechanism and implication of this effect. Essentially, the orange circle on the left appears to be smaller than the one on the right although in reality they are the same size.

10

Leaning Tower

Leaning Tower
Yes, the leaning tower of pisa does actually lean, but these two images are in fact one and the same. Although the image on the right appears to be leaning away from the one on the left this is only in your head. Go ahead and try the same thing with the empire state building…it will lean too, promise.

9

Wonder Block

wonder block
Yet again we have an example of an impossible object except this time it’s the rotation of the blocks that is inconsistent. Are they side by side or on top of each other? Maybe thats why they call them indecipherable figures.

8

Floating Stairs

8
For centuries artists have been pushing our perceptual limits and if you ever get lucky enough, from the right angle, you may just catch a glimpse into the practical artistic applications of optical illusions and the way our mind interprets them.

7

Spinning Silhouette

spinning1
Created by web designer Nobuyuki Kayahara, some people at first see the figure spinning clockwise while others see it spinning counterclockwise. Don’t spend too much time trying to decipher it though, you could be here all day.

6

Up and Down

6
Although it is obvious that the pillars in this optical illusion gif are staying in the same horizontal position, our brain is convinced that they should be moving to the right.

5

Rotating Squares

rotating squares
At first this optical illusion picture may be hard to see, but if you begin to scan back and forth across the image you will notice that the squares in your periphery begin to rotate. As soon as your eyes stop moving, however, rotation will cease.

4

Static Motion

static motion
No, this is not an optical illusions GIF. The image really is static. Notice that when you look at any individual point dead on, it will stop moving. This powerful optical illusion is derived from interacting color contrasts and shape positions within the image.

3

Lilac Chaser

3
Also known as the pac-man illusion, if you stare at the center cross for a couple seconds you will begin to perceive a green disco going around the circle of magenta discs. After a few more seconds the magenta discs will gradually begin to fade away until all you see is a green disc going in a circle around the cross (if you’re having trouble seeing this optical illusion move closer to the screen).

2

Cafe Illusion

2
Another famous optical illusion, this one was recently rediscovered in a cafe wall at the bottom of St. Michael’s Hill. Although the lines appear to be diverging from one another they are in fact quite parallel.

1

Checker Shadow Illusion

checker shadow
Probably one of the most unbelievable illusions out there, this one was first optical illusions pictures published by Edward Adelson, a professor at MIT. Although the square labeled “A” appears to be darker than the square labeled “B”, they are actually exactly the same shade of gray. It’s okay if you don’t believe it, we didn’t either, but Photoshop proved us wrong.

Source,credits and courtesy:list25.com




Monday, 28 August 2017

The Black hole

What is a black hole?
A black hole is a location in space with such a strong gravitational field that the escape velocity exceeds the speed of light. What this means is that you require a velocity greater than the speed of light (a physical impossibility) to escape the black hole, as can be seen in the image below.
In General Relativity, mass warps spacetime depending on the mass-density, and so when you pack a lot of mass in a very small area, spacetime curves so severely that it traps even light. Since a black hole does not reflect—apart, potentially, from the nearly undetectable Hawking radiation—it is thus completely black.
The image below is a nice analogy for a black hole, where, beyond a certain point, the water current is so strong that no speed will be sufficient to escape it. Do note however that the image below is a twodimensional representation, whereas a black hole is threedimensional.
Image credit: Answers magazine

How is a black hole formed?
It all starts with a massive star. As the star fuses hydrogen into heavier elements (a process called thermonuclear fusion), the heat produced creates an outward pressure, which acts against the inward force from gravity. In essence, the thermal pressure prevents the star from collapsing under its own gravity, and as long as the star has fuel to fuse and create heat, the thermal pressure and gravity are in balance (called hydrostatic equilibrium).
Image: copyright © 2017 Martin Silvertant. All rights reserved.
At one point the star runs out of fuel, which means the thermal pressure decreases, and gravity takes over. This is when a core collapse occurs. Stars with an end mass below the Chandrasekhar limit of 1.4 times the mass of the Sun will collapse into white dwarfs, stars with an end mass between the Chandrasekhar limit and the Tolman–Oppenheimer–Volkoff limit (TOV limit) of 2–3 times the mass of the Sun will become neutron stars, and stars with an end mass above the TOV limit will become black holes. This end mass correlates with an initial mass of at least 25 times the mass of the Sun.
Let’s say the star in the image above is 30 solar masses. When the core collapses, an explosion occurs called a supernova, which ejects a lot of the material into space. Here is an image of an actual supernova:

In the image below you can see how the initial mass of a star relates to its end mass. For a star with an initial mass 30 times the mass of the Sun, its end mass is around 4 solar masses—enough to form a black hole.


Image credit: Marco Limongi
I marked two lines in the image as examples on how to read it. A star with an initial mass of 25 M☉ (solar masses) will have an end mass of around 2 M☉ (remember the TOV limit of 2–3 M☉?). I also marked a star of 30 M☉ in blue, which as you can see corresponds to an end mass of 4 M☉. Also, as you can see any star with an initial mass below 25 M☉ will become a neutron star with a mass of 0.88–1.44 M☉[1].

Why does a black hole have such an intense gravitational field?
Now, here comes the crucial bit. The strength of a gravitational field depends on two factors:
  • The mass of an object.
  • How far away you are from the object.
Image: copyright © 2017 Martin Silvertant. All rights reserved.
If you look at the star above, it has a much bigger radius than the neutron star and the black hole. The proportions are way off however, as the neutron star and black hole are far smaller than this. While the Sun has a diameter of 1.3914 million km (and 1 solar mass), a neutron star is typically about 20 km in diameter (at around 1.4 solar masses), and a black hole with a mass of 3 solar masses is thought to be compressed to a point, though its Schwarzschild radius (or gravitational radius) at this mass is around 8.86 km (17.73 km in diameter). I will talk more about the Schwarzschild radius in a moment.
So here you have three objects of increasing mass, but decreasing radius. Now, although all three objects have gravitational fields of different strengths due to differences in mass, their radius is also crucial. If we assume all three objects to be of the same mass but different sizes, then in order to experience the same gravitational field from the star as from the neutron star, you would have to be inside the star. However, to experience the same gravitational field from the neutron star as from the regular star, you can be a long distance away from it (indicated by the yellow circle around the neutron star). So you see, given the same mass but a smaller radius, you can get much closer to the neutron star as you could to the regular star, and so you would experience a far more intense gravitational field on the surface of the neutron star as on the regular star. A black hole has more mass and a far smaller radius (presumed to be a point source), so its gravitational field when you get close to it is really extreme. Extreme enough so that not even light—which has the greatest speed possible in the universe—can escape, as we saw at the beginning.

What is the anatomy of a black hole?
Below you can see a simplified version of the relevant parts of a black hole. First of all, we talked about how a black hole is compressed to a point. At least, this is what is supposed, though in reality we really don’t know if a black hole is actually a point source. Whether this point source is physical or mathematical, it’s called a gravitational singularity. This singularity has a region within which the escape velocity exceeds the speed of light, defined by the Schwarzschild radius. The boundary beyond which not even light can escape the black hole is called the event horizon, which is a boundary in spacetime.
Image: copyright © 2017 Martin Silvertant. All rights reserved.
Mass curves spacetime, and in case of a black hole the mass density curves spacetime to such an extent that light becomes trapped. The image below gives some idea of what that is like, though do keep in mind that this is a two dimensional representation of the warping of space, whereas in reality space is warped three dimensionally. Therefore it’s better to think of spacetime curving inwards, creating a gravity well (pictured in b in the image below).
Let’s look at a more complete picture of the black hole anatomy. Below is a Schwarzschild black hole, which is the most general black hole model. It’s a non-rotating black hole without charge. No non-rotating black holes are thought to exist, but the Schwarzschild metric provides a simple model of what’s going on in a black hole. In a moment we will have a look at a rotating black hole.
Image: copyright © 2017 Martin Silvertant. All rights reserved.
As you can see, there are two to three additional components compared to the basic black hole anatomy. A black hole has an outer event horizon, and an inner event horizon, or Cauchy horizon. One side of the Cauchy horizon contains closed space-like geodesics, and the other side contains closed time-like geodesics. A geodesic is the shortest path between two points in a curved space. As matter falls into the black hole, it takes the shortest possible path, and beyond the Cauchy horizon space- and time geodesics become reversed. So beyond the inner event horizon, you are no longer traveling through space, but through time. As such, if you were to cross this horizon, you would move towards your inevitable future which is the singularity.
Outside the Schwarzschild radius, there is a boundary called the photon sphere, where gravity is strong enough that photons (light particles) are forced to travel in orbits. Beyond that boundary and you will move towards the event horizon, but at the photon sphere, photons will travel in orbits for at least a little while (the orbits are unstable). What’s interesting about photons orbiting in circles is that when you are located at the photon sphere, photons that start at the back of your head will orbit the black hole, and will then be captured by your eyes, so effectively you will see the back of your head. Weird stuff.
And finally, let’s have a look at a rotating black hole, which is either a Kerr black hole (a rotating black hole without electric charge) or a Kerr–Newman black hole(a rotating black hole with electric charge). A black hole can only have three fundamental properties: mass, electric charge and angular momentum (spin).
Image: copyright © 2017 Martin Silvertant. All rights reserved.
Stars rotate, and when a massive star collapses into a black hole, its angular momentum is not only conserved in the black hole, but as its radius decreases considerably, so too will its angular momentum increase. Think of an ice skater, who increases its spin rate when she pulls in her arms, which decreases her moment of inertia.
Image credit: Boundless
The rotation of the black hole causes the Schwarzschild radius to become oblate due to the centrifugal force. Also, the gravitational singularity is no longer a point source, but a twodimensional ring singularity. One important additional component to a rotating black hole is the ergosphere, which is a region beyond the outer event horizon. The ergosphere touches the event horizon at the poles of a rotating black hole and extends to a greater radius at the equator, and depending on the speed of rotation of the black hole, the ergosphere will be shaped either like an oblate spheroid or a pumpkin shape.
As a black hole rotates, it twists spacetime in the direction of rotation at a speed that decreases with distance from the event horizon, meaning that spacetime closer to the event horizon will be twisted to a greater degree than the space further out from the event horizon. This process is known as the frame-dragging. Because of this dragging effect, objects within the ergosphere cannot appear stationary with respect to an outside observer at a great distance unless the object was to move at faster than the speed of light with respect to the local spacetime, which is not possible. Since the ergosphere is located outside the event horizon however, objects in this region can still escape from the black hole by gaining velocity due to the rotation of the black hole.

As for how we can understand black holes, there are two ways:
  • Observation — Although you cannot observe a black hole directly, there are ways of indirectly making observations of a black hole—thus learning more about them:
    • You can observe the accretion disc, provided the black hole is feeding. As matter spirals into a black hole, it forms an accretion disc, which is being superheated and thus glows brightly, giving off X-rays and possibly gamma rays when too much matter tries to spiral in and becomes expelled at the poles.
    • You can observe the orbits of the stars[2][3] in proximity to the black hole. Since the black hole exerts a gravitational influence on the stars that orbit the black hole, by looking at the angles and velocities of the stars, you can deduce that there is a massive object influencing them.
    • You can observe gravitational lenses. Objects with high mass warp spacetime, and so light itself becomes curved in so-called gravitational lenses. By measuring how much light curves, you can deduce the presence and mass of a black hole.
    • You can in principle observe Hawking radiation. Black holes slowly radiate away their mass as part of Hawking radiation. This effect is not observable with current technology however, as the signals are drown out by the cosmic microwave background radiation.
  • Theoretical research — There are is also progress in theoretical physics to be made, as this is the only way to gain insights into what might be behind the black hole event horizon. And then there is also the black hole information paradox. Hawking applied quantum field theory to black hole spacetime and showed that black holes will radiate particles with black-body radiation called Hawking radiation, which slowly evaporates black holes over time. This poses a major problem for physics, because it implies that the information that constitutes the matter that falls into the black hole is lost forever, while the law of conservation indicates that information is never lost. There have been a myriad of attempts at solutions to this problem over the years, including:
Footnotes
Source,credits and courtesy:  quora-what is a black hole?



Sunday, 27 August 2017

Mechanics and Properties of Matter

Mechanics is the study of motion of bodies or objects 

Whats motion?

When a body tries to change its position from one place to other with respective time, we say that the body is in motion.

  • There are two types of motion:
1. Linear motion
2. Rotational motion

Linear motion: A person walking on the floor is a linear motion

Rotational motion: The motion of a top,spinning on its axis is rotational

Distance: The space between two points is called distance

Displacement: The shortest distance covered by a body is called displacement

Speed: The distance covered by a body per unit time is known as speed

   Speed = distance travelled/time period

units: metre/second i.e m/s     

Velocity: The rate of change of displacement per unit time is called velocity

units: The SI unit for velocity is metre/second i.e m/s

Speed vs Velocity: The difference between speed and time is speed is the distance between two points where as the velocity is distance travelled by a body in a specific direction.

Acceleration: Velocity of a body changes due to speed or direction or both.The rate of change of velocity of a body is called acceleration.

Acceleration = change in velocity / time

Acceleration due to gravity: it is defined as the rate of change of acceleration due to gravity  i.e the value of acceleration due to gravity(g)  on the surface of the earth is about 9.8 m/s^2

Ex: When a body is freely falling from 10th floor and the other body is falling from 5th floor the velocity of 10th floor body is more than that of 5th floor i.e the velocity increases every second by 9.8m/s.

Force: A force is just a push or pull which changes the bodies state of rest or uniform motion in a straight line.

Gravitational force: The force which attracts everything towards the earth is known as gravitational force, in fact there is gravitational force between all bodies.

 Newton's law of universal gravitation states that every particle in the universe attracts every other particle with a force that is directly proportional to their masses and inversely proportional to the square of the distance between them.


it is given by→ F= G m1*m2/r^2
where 'r' is the distance between two bodies of masses 'm1' and 'm2' respectively


Centripetal Force: If  a body is moving in a circular motion there must be a force which is directing it towards its centre, this is known as centripetal force.


Its given by F=mv^2/r


Centrifugal Force:The force which acts outwards to a body which is moving in a circular motion,its not a real force however it is used to explain some of the theories successfully.

Weight: The weight of a body is the force with which the earth attracts the body towards its centre where as the mass is the quantity of matter contained in a body.

W=mg(m=mass,g=gravity)

Friction: It is a force which opposses the relative motion of two surfaces to be in contact.

Newton's laws of motion: There are three laws given by newton on the account of motion


First law: Every body continues to be in rest or uniform motion until a net applied on it.

Second law:The rate of change of momentum of a body is equal to force applied on it(F=ma).

Third law: Every action has an equal and opposite reaction

work:If a force produces change in motion and can be calculated by the product of force and displacement then its known as work.It is given by W=F.S,units: Joule's

Power: The work done per unit time is known as power units: watt

Energy: The capacity to do work is known as energy units: joule

Kinetic energy:The energy possessed by a body due to its motion is called kinetic energy and its given by KE=mv^2/2

Potential energy: The energy possessed by a body by the virtue of its position is called potential energy PE=mgh

Conservation of energy: As energy can neither be created nor destroyed but can be transformed from one form to another the total energy remains constant

Centre of gravity:A point at which a body's whole weight is acted upon is called centre of gravity.

Escape velocity: The velocity required to go beyond earth's garvitational field is called escape velocity i.e 11.2km/s or 25k miles/hr or in other words the body would not return to earth's surface.

Density: The mass per unit volume of a body or substance is called as density 
units: kg/m^3.

Relative density: It is defined as the ratio of density of a substance to the density of water,it doesn't have units.

Pressure: It is defined as the force per unit area P=f/a units: Nm/m^2

Pressure in liquids: The pressure at any point in a liquid acts in all directions P=hpg

Atmospheric pressure: The air surrounding the earth is known as atmosphere.

Archimedes principle: If a body is completely or partially immersed in a liquid it experiences a upward thrust which is equal to the weight of the fluid displaced

Matter: A matter is something which occupies space.it consists of atoms and molecules.

Molecule: It is the smallest particle of a substance which has all its physical and chemical properties.

Atom: It is a smallest particle which has chemical propertities of their own.

Diffusion: It is a mixture of gases,liquid's and solids

Surface tension: The tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area is called surface tension.

Capillarity:When a clean glass tube having a small diameter is dipped in water then the water cleans the tube this is known as capillarity

Adhessive force: The force of attraction between unlike molecules is known as adhessive force

Cohessive force: The force of attraction between like molecules is known as cohessive force









Friday, 25 August 2017

The new High speed-Bullet trains

The world's top no.1 is from CHINA:


  • China is starting a worlds new fastest bullet train in this sept 21st 2017
  • From Beijing-Shanghai



  • These trains can hit the speed of 400kmph but to avoid accidents they can be driven at 350kmph only

World's top 2 bullet train is from CHINA

As spoken the second fastest bullet train is also from china which is currently being

Image result for harmony crh 380a free pics for commercial use


  • It can hit at a speed of 380kmph
  • Presently its serving between Shanghai-Nanjing
  • The capacity of the train is 494people
  • This was manufactured by one of the china companies named CRRC qingdao sifang and roling stock

World's top 3 bullet train is from ITALY


AGV Innotrans 2008.JPG

  • Manufactured by Alstom
  • It can travel at a speed of 360kmph
  • Serving between Rome-Nepal
  • It has high end facilities like TV,wifi and flexible seats

  • Some interesting facts about bullet trains:

In this Sept. 24, 2014 photo, a Shinkansen bullet train arrives at Tokyo Station in Tokyo. Japan launched its bullet train between Tokyo and Osaka 50 years ago Wednesday, Oct. 1, 2014.(AP Photo/Shizuo Kambayashi)

Read more at: https://phys.org/news/2014-10-world-bullet-japan.html#jCp


1. The first bullet train was started by JAPAN
2. Since 1930 the research on bullet train started
3. This train was started in 1964 i.e the first one

  • After bullet train→Hyper loop
Image result for free hyper loop pics for commercial use
credits: Mashable

1. There is one more type of travelling medium on the way which is ahead i.e Hyper loop.

2. Through hyper loop it can hit 700kmph

https://www.physicslover.in/firebase-messaging-sw.js https://www.physicslover.in/firebase-messaging-sw.js