Last year comes a research saying that blasts that create gamma-ray bursts may exceed the speed of light in its surrounding gas clouds. They propose jets going superluminal. 


Research indicate that these type of superluminal jets could actually create the time-reversibility seen in  the gamma-ray burst light curves.

Before moving forward let's see what consequences can occur if an object/energy exceeds the speed of light. 

In 1905, Einstein came up with the most shocking idea of all time known as the theory of relativity.
 He said that the speed of light is constant and independent of every other thing in the universe. And gave an equation explaining the difference that came in time, mass, length, energy with the speed of observer w.r.t. the speed of light as - t'=t/√1 - c^2/v^2.


The same theory says that the mass of the object increases with their speed, that requires increase in energy. The more mass, the more energy is required. And when an object reach the speed of light, Einstein calculated and said, its mass would be infinite, and the amount of energy required to increase its speed too. 
Similarly, if the object exceeds the speed of light it will experience time slow relatively and at the point would experience time moving backwards. 

Now that we know that violating Einstein's theory of relativity would bother Einstein but the whole universe too. Let's understand what are the gamma ray bursts and how they do it. 


In gamma-ray astronomy, gamma-ray bursts (GRBs) are tremendously energetic explosions that are observed in far distant galaxies. They are the brightest and most energetic electromagnetic events known to occur in the whole universe. An initial flash of gamma rays occur at first then a longer-lived "afterglow" is usually emitted at longer wavelengths.
Gamma-ray bursts (GRBs) originate from the violent ejection of material at the end of massive star evolution accompanying black hole formation. 
The sources of Gammma Ray Bursts are billions of light years away from us, hinting that the explosions are tremendously energetic (an average burst releases as much energy in a few seconds as our Sun will in its entire 10 billion year lifetime) and extremely rare (only a few per galaxy per million years) too.

After collecting enough knowledge about Einstein's theory of relativity and Gamma ray bursts(GRB). Let's find out how the gamma ray bursts are successful in Time Reversibility. 


Now, new research suggests a fascinating answer for what might be causing this time reversibility effect. If waves surrounded in these jets that produce gamma-ray bursts can travel faster than light  at 'superluminal' speeds ,Time Reversiblity will be one of the major effects. 


These type of speeding waves could actually be possible. We know that when light is travelling through a medium , its phase velocity (speed of propagation of a wave in a medium) is slightly slower than 'c' - the speed of light in a vacuum. 

Therefore, a wave could travel through a gamma-ray burst jet at superluminal speeds without breaking relativity. 

To understand this let's have a look on what is Cheronkov radiation and how is it making possible to travel at the speed more than the c without breaking relativity. 


Cherenkov radiation is too an electromagnetic radiation emitted when a charged particle (e.g, electron) passes through a dielectric medium at a velocity greater than the phase velocity of light in that medium. Theory of Special relativity is not violated since light travels slower in materials with refractive index more than one, and it is the speed of light in a vacuum which cannot be reached (or exceeded) by particles with mass. 
OR it can be easily defined as the Cheronkov radiation, often seen as a distinctive blue glow. That glow - 'a luminal bloom' - is produced when charged particles such as electrons move faster through water than the phase velocity of light.


"In this model an impactor wave in an expanding gamma-ray burst jet accelerates from subluminal to superluminal velocities, or decelerates from superluminal to subluminal velocities," . They write in their paper. 

"The impactor wave interacts with the surrounding medium to produce Cherenkov and/or other collisional radiation when travelling faster than the speed of light in this medium, and other mechanisms (such as thermalised Compton or synchrotron shock radiation) when travelling slower than the speed of light.

"These transitions create both a time-forward and a time-reversed set of [gamma-ray burst] light curve features through the process of relativistic image doubling."

Such relativistic image doubling is thought to occur in cheronkov radiation. When a charged particle travels at near light-speed and enters the water medium, it moves faster than the Cherenkov radiation it itself produces, and therefore it can hypothetically appear to be in two positions at once: one image would be appearing to move forward in time and the other would be backwards.

But remember, this doubling has not yet been experimentally observed/proven. But if it does occur, it could be responsible too for the occurence of the time-reversibility seen in gamma-ray burst light curves, occurring both when the impactor wave travells through the jet medium accelerates to speeds faster than light, and decelerates to subluminal speeds.

More work is needed, of course.

However, the researchers said, their model provides better explanations for the characteristics of gamma-ray burst light curves than models that don't include time reversibility.

"Standard gamma-ray burst models have neglected time-reversible light curve properties," Hakkila said. "Superluminal jet motion accounts for these properties while retaining a great many standard model features."

The research has been published in The Astrophysical Journal. 


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