Monthly Archives: June 2005

Strange Stars

 

Friends,

 

        We have seen in earlier VERITAS articles that neutron stars are stars that consist only of neutrons of atoms. So the atoms are not there.

The electrons and protons that form normal atoms have been stripped off in neutron stars. So a neutron star is a pure huge collection of neutrons. A neutron star is VERY dense. A teaspoon of a neutron star can weigh a million tonnes!

        What is denser than a neutron star? A black hole! It is so massive that it does not even let light escape it.

  Till a few years back two stars designated RXJ185635-3754 and 3C58 were thought to be neutron stars. But a more detailed analysis using the laws of Physics showed that they were much more dense than what they would have been if they were neutron stars. But they are not black holes either. So their density is between a neutron star and a black hole!

      But what kind of matter can be so dense?? We know that neutrons, electrons and protons are made up of quarks. If a neutron star gets too dense then the individual neutrons break and the quarks come out and fuse together. This kind of matter- formed by a collection of quarks is called “strange matter” or “quark matter”. And a star formed from this type of matter is called a “strange star”. So a strange star is not composed of neutrons but is composed of quarks. There are three kinds of quarks that form strange stars: up quark, down quark and strange quark.

        So we have a weird new form of matter: composed of quarks only.

Note that all matter is ultimately composed of quarks. But normal matter consists of quarks bound together as electrons, protons and neutrons and these bound in a atomic structure and those further bound as molecules. Strange matter is just a sea of quarks connected to each other without any other detailed structure. Theories suggest that strange matter may be stable and thus exist under normal conditions. Our universe could be full of strange stars of various sizes or small groups of quarks bound together. A small group of quarks bound together is called a strangelet. A strangelet may be microscopically small. Our universe may be full of strangelets.

 When ordinary matter comes in contact with a strangelet, the massive gravitational pull of the strangelet pulls the quarks out of the ordinary matter. So the quarks of the ordinary matter fuse with the strangelet to increase its size. So ordinary matter is “eaten” by the strangelet.

       We know that a huge amount of mass in our Universe is unaccounted for. Theories of Physics predict a much larger mass of the universe than what we see around us. This unaccounted mass has been named “dark matter”.

Scientists are desperately searching for it. Some Physicists suggest that strange matter may be able to explain this unaccounted mass. Dark matter may just be strange matter!

 

                “Call it then, what thou wilt-

                 Call it bliss! Heart! Love! God!

                 I have no name to give it!

                 Feeling is all in all:

                 The Name is sound and smoke

                 Obscuring Heaven’s clear glow.” – Goethe ( Faust )

 

 

 

Kanwar

 

 

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  Go, wondrous creature! mount where Science guides:                 

  Go, measure earth, weigh air, and state the tides:                 

  Instruct the planets in what orbs to run,                          

  Correct old time and regulate the Sun;                             

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The Many-Worlds Interpretation

 

Friends,

 

      We have seen in several earier VERITAS posts on Quantum Mechanics that Physics is facing a great problem- For the first time in the history of Science we have experimental facts that our minds(and hearts) refuse to accept. Some scientists close their eyes to their instincts and accept the strange experimental evidence. Others struggle with trying to find a theory that explains the experiments without having to change the way we think. For the first time in human history we need philosophical interpretations to understand experimental evidence.

 

      First let us revise the problem: Lets take an electron.

The electron may be in the spin up state ( call it |+> ), or the electron may be in the spin down state ( call it |-> ). Now experimental evidence has shown that the electron is not in a particular state till it is measured. And the electron’s state is in a way created by the experiment. So in a sense the observer ( the measuring apparatus) creates the electron’s state. And it is not deterministic whether the electron will come to |+> or |-> after the measurment. There is a probability that it will come to |+>  and there is a probability that it will come to |->.

So we say that the electron’s initial state is :

      |s> = a*|+> + b*|->

      The probability of it coming to |+> after measurment is a^2 and the probability of it coming to |-> is b^2. So we see that the traditional concept of determinism in Physics is shattered.

You cannot determine the future of the electron with certainty even if you are given all possible information about its present. You can only determine the probabilities of a particular future.

 

      Measurment collapses the electron state into either |+> or |->. But the collapse is something that Physicists don’t understand. When does it happen? How does it happen? How fast does it happen? How does it know what probabilities mean? etc etc. These are questions that keep bothering us.

      Note: In the above when I say electron I mean all microscopic particles. So the above effects are not specific to the electron. They are shared by all elementary particles.

      In 1957 Hugh Everett, A PhD student at Princeton came up with a even more dramatic idea that does away with collapse. He proposed that measurment does not create |+> OR |->. Instead it creates a |+> AND |->. So all possibilities are realized. So the measurment splits the state into all its possible parts. These parts evolve seperately and do not interact with each other. But what state does the observer see? Both! And this is bacause the observer is also split into two: one that sees |+> and the other that sees |->. And if you take this logic further you will see that the whole universe splits into two.

      So according to this interpretation of Quantum Mechanics whenever a measurment occurs in the microscopic world the universe splits into several parts-one part for every possibility. These universes do not interact with each other and evolve independently.

      So according to this interpretation since the big bang the universe has split millions and millions of times. So there are millions and millions of universes each different from the other- each realizing a possibility that existed in the past.

      This theory is very strange and does not find favour with a lot of Physicists. But cosmologists like this theory. And this is because this theory helps them comes to terms with the quantumness of the universe.

 

      But for the rest of us this has very strange consequences: in a vast majority of the universes I do not exist. In a vast majority of universes world war II never happened. And in a vast majority of universes life never started.

 

      Friends, Quantum Mechanics is a strange theory. And this is because this world is a strange place. Hundreds of years later when someone looks back at 20th and 21st centuries and analyses the most profound thought that changed mankind he will no doubt say “Quantum Mechanics”. This is because this theory, more than any other development in the last 100 years WILL change the way we think. Dont ignore it as just another branch of Physics. Realize that it is a shaper of the way we humans think. It is a shaper of human destiny.Be a part of this great revolution in human thought.

 

Kanwar

 

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  Go, wondrous creature! mount where Science guides:                  

  Go, measure earth, weigh air, and state the tides:                 

  Instruct the planets in what orbs to run,                          

  Correct old time and regulate the Sun;                             

|======================================================|