May 22, 2022

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We've only seen the quantum Unruh effect in science fiction.  Now MIT has a plan to hunt him down

We’ve only seen the quantum Unruh effect in science fiction. Now MIT has a plan to hunt him down

Unruh’s effect is elusive. and relatively unknown. However, fans of science fiction films are often familiar with it. We can see a reasonably similar phenomenon in some films that show spaceships capable of accelerating in an instant to reach them Speed ​​close to the speed of lightor even overcome, like those in the epics ‘star Wars’ also ‘Star Trek’.

physical or physical William George UnruhAnd Stephen Fielding s Paul Davis He described it mathematically in independent work between 1973 and 1976, and since then several research groups have attempted it Recreate it in their lab. I used the word “attempt” explicitly because although those responsible for some of the experiments claimed to be their flirts, the greater part of the scientific community has cast many doubts about these demonstrations.

Namely that some of the ingredients that we must introduce in our recipe if we want to cook this phenomenon is quantum field theory, The space or black body radiation. It sounds complicated, and in fact, it is, so it’s a good idea to resort to the influence that some science fiction movies suggest on us so that we can intuition as accurately as possible. Which consists According to the theoretical description laid down by physicists.

The void isn’t really empty

Perhaps the recreations that cinema give us of this mechanism are episodic and only seek to provide greater excitement for the sequences in which we see that the spaceship suddenly manages to speed up Exceeding the speed of light.

In any case, some science fiction films show us how during those moments the cabins of these ships are flooded with intense light despite being in a space area far from any star. It is strange that this phenomenon Similar to what physicists describe When they talk about the Unruh effect.

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The formal description of this effect is complex and not at all intuitive, but we can approach it in a slightly amicable way if we take as a starting point the fact that quantum field theory tells us that, in fact, The void is not empty. The idea familiar to all of us invites us to accept that in order to obtain a vacuum, we must extract all matter and energy from a certain region of space.

From a quantitative perspective, a vacuum is subject to fluctuations described by Heisenberg’s Uncertainty Principle.

However, modern science has superseded this view. evolution for relativistic mechanics And quantum mechanics has allowed scientists to develop a description of a vacuum that is more modifiable to reality as it is seen as the physical state of an associated system. with the least amount of energy That this could be. The implications of this idea, which have been experimentally verified, are very profound. It is also surprising.

From the point of view Quantum mechanics The void contains waves that arise randomly. Also, these waves behave like particles, so one way to define this quantum vacuum is to describe it as a mixture of particles that come and go very quickly. This is what is known as vacuum fluctuations, and the best way to understand it is Heisenberg’s Uncertainty Principle.

Empty space

The emptiness of space is not empty at all. It contains at least trace amounts of matter, as well as cosmic rays and the cosmic background radiation.

We don’t need to know what this principle tells us in full, but going forward, it is good for us to know that it is a theory that defends this in physical systems described by quantum mechanics, which studies the properties of nature at the atomic scale, We can’t select at once The value of all physical parameters that we can observe.

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In classical mechanics we can describe any physical system by listing the value of the parameters that we can measure, but in quantum mechanics We can not do that.

In search of the elusive Unruh effect

This phenomenon is based on the idea of ​​a vacuum proposed by quantum physics. In fact, it suggests from a theoretical point of view that nature of emptiness It depends on the path an accelerating observer follows through the space-time continuum.

Unruh, Fulling, and Davies’ prediction suggests that an object whose mass is subject to acceleration in a vacuum is exposed to electromagnetic radiation from Interact with quantum fluctuations Which, as we have seen, occurs in a pseudo-vacuum of space.

This description is inconsistent with the traditional notion of a vacuum that we all easily sense, but it fits a gauntlet with the formulation of a vacuum that Introducing quantum mechanics.

Moreover, according to physicists, the radiation generated by the interaction between the accelerating mass and fluctuations in the quantum vacuum should acquire glow shapeWhich brings us, once again, to the unexpectedly appropriate way in which science fiction films visually describe hyperbolic travel.

According to physicists, the radiation from the interaction between the accelerating mass and fluctuations in the quantum vacuum should take the form of a glow.

The problem is that empirically verifying the existence of this effect is not easy. Not that because scientists are to be able to identify and measure the electromagnetic radiation generated by the interaction, it is necessary to The acceleration the body is going through is brutal. In fact, if a massive object was made up of only one atom, it would have to accelerate to the speed of light in a millionth of a second.

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This is the great challenge that physicists have been facing for more than forty years, but researchers from the Massachusetts Institute of Technology (US) and the University of Waterloo (Canada) published an interesting article in the scientific journal Physical Review Letters in which they assert that they have found a way to do so Determining the Unruh Effect Experimentally.

His strategy is based on the idea that theory tells us that this phenomenon can arise spontaneously as a result of fluctuations in a quantum vacuum. If we introduce an accelerating mass into this region of space, the probability of this effect being it increasesso these physicists suggest maximizing this possibility by introducing light.

By adding photons to the vacuum-exposed region, the fluctuations multiply exponentially

In their article they explain that by adding photons to the vacuum exposed region, the fluctuations They multiply greatly, so that the probability of the Unruh effect when an accelerating mass is introduced is much greater. In fact, the way they plan to approach their experiment is to speed up a single atom so that it follows a specific path through a region of space filled with photons.

The most important difference between this experiment and those performed previously for the same purpose is that on paper, these physicists can effectively induce the production of the Unruh effect. Moreover, they hope that their experience will help shed light Hawking radiationwhich is assumed The late Stephen Hawking. But this is another date. One we will indulge in if you are interested in this topic and let us know in the comments.

cover photo | Javier Nouval

More information | Physical Review Letters | science daily