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Cosmic Rays

Do cosmic rays get reflected by a mirror?Just like the normal(visible spectrum) light, do cosmic rays and lasers get reflected by a polished surface or are they strong enough to penetrate through them? (Sangeetha Varma posted this question)

Answer: Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth’s atmosphere and surface. Cosmic rays were thought to be electromagnetic radiation in the past. Most primary cosmic rays entering the atmosphere from deep space are composed of subatomic particles that normally occur on Earth, such as protons, atomic nuclei, or electrons. However, a very small fraction are particles of antimatter, such as positrons or antiprotons. The precise nature of this remaining fraction is an area of active research.

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How OPERA found the fast µ neutrino traveled faster than light?

After the news of the neutrino travelling faster than light came, everyone is enquiring about this. Many students are of the opinion that “It is time to change the Physics Textbooks” But time has not come. It is just the first result pointing towards a possibility that some particles can travel faster than light. Here is an account of the result obtained by the researchers at OPERA.

Researchers on the Opera (Oscillation Project with Emulsion-tRacking Apparatus) experiment recorded the arrival times of ghostly subatomic particles called neutrinos sent from Cern on a 730km journey through the Earth to the Gran Sasso lab.

The trip would take a beam of light 2.4 milliseconds to complete, but after running the experiment for three years and timing the arrival of 15,000 neutrinos, the scientists discovered that the particles arrived at Gran Sasso sixty billionths of a second earlier, with an error margin of plus or minus 10 billionths of a second.

The measurement amounts to the neutrinos travelling faster than the speed of light by a fraction of 20 parts per million. Since the speed of light is 299,792,458 metres per second, the neutrinos were evidently travelling at 299,798,454 metres per second.

The result is so unlikely that even the research team is being cautious with its interpretation. Physicists said they would be sceptical of the finding until other laboratories confirmed the result.

Many think that IF neutrinos really traveled faster than light, the entire principles and theories proposed by Einstein would be proved wrong. But this is not true. One of the great dream of Einstein was the unification. This would pave way for the theory of unification of forces.

You can download the research report here
Learn all about Neutrinos

A Question From Relativity

Sreeram Asks:

“my question is on relativity.Let us say two persons,one is standing still and other is moving with uniform velocity in a straight line(in +ve x direction),both are carrying  a clock synchronized previously.For the moving person he is at rest and the other guy is moving away from him in the opposite direction(negative x direction).Both of them feel that clock of the other guy is moving slowly.let us say the moving guy never stops and he calls the other in telephone at some point of time and asks the
time in his clock.But he will find that clock with him,is actually faster.how can that happen?”

Answer:

Please note that the theory of relativity can  be applied only for velocities compared to that of light in vacuum (3 lakh km/s). The situation will be very much different when we travel at such velocities. So far we are able to accelerate only subatomic particles to this speeds (LHC).

 

 

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