Dark Side of the moon-Tidal effect

When I was a child, my grand mother used to tell me, look at the moon, there is an old women who is weaving and I was like...'wow.. that's true'. Actually this image of old women  changes with region. In many places people think of a face of a man (fig. 01)  and a rabbit for many others places. It is only because the creative nature of humans. It changes from place to place.I used to stare at that old women frequently.

 

FIG. 01

As I go to higher standards of school, I was taught that moon is a celestial body which revolves around the earth with a period of  27 earth days. I also rotates around the axis which passes through its center and takes 29 days to do it. wait a minute....if moon rotates around its  axis then how it is possible that the old women doesn't go to opposite side of and a new face replace it. It was a kind of fascinating observation. then I started to find the reason behind it and I found.

                      The key thing is its orbital time period (27 days) and its period (29 days). This means moon takes approximately same time as it rotates around its axis and to revolve around earth. That's why only one side of the moon  faces earth. 

                      Let me make you more comfortable with the explanation. Take two balls,one as earth,BALL E and other as moon,BALL M. In the BALL M, mark a point,and make this point to face BALL E.Now try rotate the BALL M and simultaneously revolve it around the BALL E. Try to make their time period same. This is a very good method to understand what's going on. You can also understand it with following animation video.

                 

This phenomenon is not just  unique for earth-moon system. This has been observed in many planet-satellite system of solar system.for example Pluto-charon.This is called spin-orbit resonance phenomenon. Tidal torques from the planet and internal friction in the satellite is explained as the cause behind this.

Question is what would happen if this kind of phenomenon doesn't occur.From Newton's gravitational law we know that the part of moon which is nearer to planet will face more gravitational pull than the part away from the planet. So if moon doesn't show spin-orbit resonance, then all the parts of moon will face squeezing and expanding simultaneously. This will cause moon to be unstable.Sometimes it will break it apart. Saturn's ring are thought as debris of an ancient moon which was wrecked by Saturn's strong gravity.Now-a-days its moon ENCELADUS is being the victim of the tidal effect.( figure below)

Speed of light- Foundation of Relativity of high speeds

From the invention of the vehicle,human is making his efforts to achieve the great speeds.He wants to move faster and faster. He built supersonic airplanes , rockets etc. to fulfill his desires. In his passion towards speed he attempted to speed up the particles at very high speeds.He thought he can speed the particles at whichever speed he wants. But Einstein had made an objection. He said NO, nothing can move faster than light. He made his conclusions on the basis of experiment done by Michelson-Morley.He postulated two ideas regarding speed of light which are the foundation of relativity theory.

1. Speed of light is constant ( 299,792,485 m/s ) in every frame of reference and in every direction.
2. All laws of physics must be same in all inertial frame of reference.

He suggested that concept of speed of light is somehow different from the speed of other particles in  Newtonian mechanics.Its velocity doesn't attach with source's velocity like we see in sound waves in classical mechanics. ( Do not relate it with relativistic Doppler's Effect) We should make an intuition  with the example.

Suppose there is a star, 5 light years ( lt. yr.) away from us. Take a hypothetical case (don't care about Keppler's and all other laws), in which a planet is swirling around the star ( fig 01), with a time period of  1 yr. with speed half of speed of light i.e. c/2 (c= 1 lt. yr. /yr., this notation will make our life easier)

                                                                            Fig 01


suppose current situation is like this,(fig 02)

                                                                             Fig 02

Speed of planet at this moment is c/2.Suppose it follow classical aspects of  speed  then the speed of light emerging from planet will be (c-c/2=c/2) means it will take 5/(c/2)=10 yrs. to reach us. Now after 1/2 yr. planet will be at situation( fig 03)

                                                                              Fig 03

But now light emerges with speed (c+c/2=1.5c) means now it will take 5/1.5c=10/3=3.33 yrs. It is less than time we calculated in previous situation. What it means actually. It means we see planet moving faster when it'll be at point B.You can visualize this phenomenon in following gif.

 But from our observations, i mean NASA and other space research center's  observations we can conclude that it is not actually happens. Einstien was right with his postulates.

In 1964, scientist named W. Bertozzi,tried to speed up the electrons to the extreme level. He had given energy  continuously  to electrons. But observed that at the low speeds he was able to speed up the electrons but as it approaches to light speed electrons started to converge their speeds to light speed c. No matter how much energy he gave to electrons he was not able to speed up electrons but the kinetic energy only.( fig 04) .Now you should start to believe on Eisntein.This can  give a solid prove for Einstein's Postulates and relativity. 

 Fig 04

I have another example to consolidate your belief on Einstein's Postulate , also on relativity consequently. There is a particle named "neutral pion". It is a short lived particle, being produced in particle accelerator, which decays in two gamma photons. Gamma rays are electromagnetic waves which travels with speed of light. Its speed is supposed to be constant, by Einstein postulate, in every frame of reference,means these should be decayed with speed c no matter pion is moving or not. But it was observed that  gamma ray  decays at speed c regardless pion is moving or not. This is a solid proof of relativity theories.

But here the queston is why can't anything achieve the speed of light? We try to get our answer from Relativity theory. From the theory we know that if a particle is moving with velocity 'v' with respect to a frame the it's mass will be increased by factor 'y'.

 If particle has rest is M0 then the mass after getting velocity 'v' will be,suppose M,

From the formula we can see, if  v tends to c then 'y' will become infinite, means particle's mass will become infinite. Infinite mass will need infinite energy to speed up it, so in W. Bertozzi's as electrons approaches light speed they need infinite energy to make their speed increase and this is not possible, infinite energy has no physical sense, we can't make electrons to travel at speed of light.

Here comes another question, why light is able to travel at its speed c ?actually if light is made up of photons which travel at light speed. So why their mass doesn't go infinity??...............This is because photon's rest mass is zero. Their mass doesn't goes infinity. So on their relativistic mass equation there is no effect of 'y'.

Sun's Wobbling And Exoplanet Detection

It is common that in the solar system every thing revolves around sun....the common barycenter of all bodies.It is true but  is it as far true as we think of it??

Let's try to understand physics behind this, there is a very common method of solving mechanical problems like this is center of mass (CM) method. Suppose we have n number of bodies M1, M2, M3, M4.....Mn, and they are at X1,X2, X3, X4....Xn distance from the origin. Then the CM of mass of the system can be  find with formula given below (for x, y and x directions) 

If we shift origin on X then (M1.X1)+(M2.X2)+(M2.X2)+(M2.X2)......+(Mn.Xn) will be equal to zero.Now if we put M1>>(M2+M3+M4...+Mn) then M1.X1 will become almost zero ( M1.X1~0 ) which in turn comes out as X1~0. What it physically means?? It means CM is almost at the M1's center.In our solar system M1 is sun and it is almost at the CM and all other bodies are revolving around it.

Here comes the point, sun is "ALMOST" at the center not "ON" the center.If we think of a system made up of only tow bodies sun and Jupiter, with all their characteristics , same mass, same distances, then barycenter will come out to be 743,114 km and sun's radius is 695,800 km., means above the sun's surface.Actually in earth-moon system system it lies 1,710 km below earth's surface.

Now think, a planet can make a star to wobble, wobble means star oscillates just like planets but with very small orbital radius. From Doppler Effect we know if a star is moving toward us, will project blue shift in its light spectrum and if it is moving away from us will project red shift on us.Amount of shift depends upon star and planet's masses and distance between them.

Red and Blue shift 

Scientists  observe star's spectrum and find red and blue shift periodically.From that they find exoplanets planets around other star systems.This method is called Radial Velocity method.This very small idea ,very basic physics lead us towards new worlds.Fascinating, isn't it..??

                                

Radial Velocity method

You can find exoplanets found by this method on this wikipedia page.

This kind of phenomenon has also observed with earth's rotational axis. Because of other celestial near bodies, like moon , mars, earth's rotational axis wobble around and a circular path and changes its polar star time to time.

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Nemesis- Reality or Mirage

Stars, we see them in the night sky.They glitter like tiny particles.Are they really sort of single particle..?? NO, most of the stars, studied till today, are actually star systems which has two or more stars.They are called BINARY star systems.Like our nearest star system,4.3 light year far, ALPHA CENTAURI, is made up of three stars. Then why we are alone,why we have only one star in our solar system......??

Alpha Centauri star system

          

Now-a-days scientists are thinking of  a companion of sun named NEMESIS. It is not discovered yet, but there are some reasonable evidences for this sun's sibling.

From the course of  history it is observed that in every 26 million years period mass extinction of species happen.Extinction of dinosaurs was part of these extinctions. It is some kind of mystery, why 26 million periodic extinction? A guy named Richard Muller, professor of physics, University of California, Berkeley and faculty senior scientist at Lawrence Berkeley National Laboratory, has come with a solutions. He forwarded a theory,suggests a sibling of sun, which is supposed to be 1 to 3 light-year  from the sun. Sun is much more massive than his brother. Nemesis creates anarchy in the OART CLOUD which leads some comets to rush towards inner solar system. Some comets get engaged with earth and create catastrophes in earth which  leads to mass extinction. I should mention here about oart cloud. Oart cloud is thick layer of icy comets covering outer solar system and when Nemesis passes through it, anarchy is being made and after story you know.  . 

Mass Extinction

Oart Cloud

It is supposed to be very less massive than sun. It together with sun, revolve around their common barycenter. It is less massive so it follow a long path around barycenter.

Here question comes, why it couldn't be seen till now..?? Richard answer that it can be a red dim dwarf star, after-all it has low mass (relative to sun) and red dwarfs are very common in the universe. It is being thought that today it is very far from sun and has very slow velocity relative to sun, means should be looked like a common star. We have a broad area to see and we don't know where to look for it. you can think like, we are able to see very far red dwarfs but why we didn't see it till now?....we don't know where to look.

NASA had a explorer named Wide-field Infrared Survey Explorer (WISE) in the space but it was unable to find Nemesis.but some kind of disturbance had been observed in the oart cloud. Later a planet hypothesized named TYCHE, nemesis's "good sister".It is supposed to be 4 times more massive than Jupiter and has about 500 times big orbit than Neptune.Can it be cause of mass extinctions......hmm......NO. Because first it has very lass mass to create such kind of rush in oart cloud and second its orbital time period is 1.8 million years and extinction happens in every 26 million years.

n 2003,a planet named SEDENA was discovered. It is almost 30 times most distant than where neptune is form the sun. Actually it has very eccentric orbit around sun,Aphelion is 937 AU ( AU=astronomical unit, 1 AU= distance between earth and sun ) and  Aphelion is 79 AU. It is where no planet was supposed to be discovered. Some scientists say that it could be nemesis's gravity which attracted sedana that far.

SEDENA-Hubble's Image

n Sumerian civilisation planet named "NIBIRU (Planet of the crossing) " has been told, which is now being thought as nemesis..or tyche maybe. Above them all, should we worry for the nemesis right now. I guess..actually Richard Muller guess...NO. Because he calculated that nemesis will revisit oart cloud after 10 million yIears and who knows where will we be at that time.