In September 2011, physicist Antonio Ereditato shocked the world. His statement could turn our understanding of the universe upside down. If the data collected by the 160 OPERA scientists were correct, the incredible was observed. Particles - in this case neutrinos - moved faster than light. According to Einstein's theory of relativity, this is impossible. And the consequences of such an observation would be incredible. Perhaps the very foundations of physics would have to be revised.
While Ereditato said that he and his team were “extremely confident” in their results, they did not say that the data was perfectly accurate. On the contrary, they asked other scientists to help them figure out what was going on.
In the end, it turned out that the OPERA results were wrong. A badly connected cable caused a sync problem and the signals from the GPS satellites were inaccurate. There was an unexpected delay in the signal. As a result, measurements of the time it took for neutrinos to cover a certain distance showed an extra 73 nanoseconds: it seemed that the neutrinos flew faster than light.
Despite months of scrutiny before starting the experiment and double-checking the data afterwards, the scientists were seriously wrong. Ereditato resigned, contrary to the remarks of many that such errors always occurred due to the extreme complexity of the device of particle accelerators.
Why did the assumption - just the assumption - that something could move faster than light cause such a noise? How confident are we that nothing can overcome this barrier?
Let's look at the second of these questions first. The speed of light in a vacuum is 299,792.458 kilometers per second - for convenience, this number is rounded up to 300,000 kilometers per second. It's quite fast. The sun is 150 million kilometers from Earth, and light from it reaches Earth in just eight minutes and twenty seconds.
Can any of our creations compete in the race against light? One of the fastest man-made objects ever built, the New Horizons space probe whizzed past Pluto and Charon in July 2015. He reached a speed relative to the Earth of 16 km / s. Much less than 300,000 km / s.
However, we had tiny particles that were moving very quickly. In the early 1960s, William Bertozzi at the Massachusetts Institute of Technology experimented with accelerating electrons to even higher speeds.
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Since electrons have a negative charge, they can be accelerated - more precisely repulsed - by applying the same negative charge to the material. The more energy is applied, the faster the electrons accelerate.
One would think that you just need to increase the applied energy to accelerate to a speed of 300,000 km / s. But it turns out that electrons just can't move that fast. Bertozzi's experiments showed that using more energy does not lead to a directly proportional increase in the speed of electrons.
Instead, huge amounts of additional energy had to be applied to alter the speed of the electrons even slightly. It was getting closer and closer to the speed of light, but it never reached it.
Imagine walking towards the door in small steps, each of which travels half the distance from your current position to the door. Strictly speaking, you will never get to the door, because after each step you take, you will have a distance to overcome. Bertozzi faced roughly such a problem when dealing with his electrons.
But light is made up of particles called photons. Why can these particles move at the speed of light, but electrons cannot?
“As objects move faster and faster, they get heavier - the heavier they get, the harder it is for them to accelerate, so you never get to the speed of light,” says Roger Rassoul, a physicist at the University of Melbourne in Australia. “A photon has no mass. If he had mass, he could not move at the speed of light."
Photons are special. They not only lack mass, which provides them with complete freedom of movement in the vacuum of space, they also do not need to accelerate. The natural energy they have at their disposal moves in waves, just like they do, so at the time of their creation they already have maximum speed. In a sense, it's easier to think of light as energy rather than a stream of particles, although in truth, light is both.
However, light travels much slower than we might expect. While internet techs like to talk about communications that operate at "the speed of light" in fiber, light travels 40% slower in the glass of that fiber than it does in a vacuum.
In reality, photons travel at a speed of 300,000 km / s, but they encounter a certain amount of interference, interference caused by other photons that are emitted by the glass atoms when the main light wave passes. This may not be easy to understand, but at least we tried.
In the same way, in the framework of special experiments with individual photons, it was possible to slow them down quite impressively. But in most cases the number of 300,000 will be valid. We have not seen or created anything that could move as fast, or even faster. There are special points, but before we touch on them, let's touch on our other question. Why is it so important that the light speed rule is strictly followed?
The answer has to do with a man named Albert Einstein, as is often the case in physics. His special theory of relativity examines the many consequences of his universal speed limits. One of the most important elements of the theory is the idea that the speed of light is constant. No matter where you are or how fast you are moving, light always moves at the same speed.
But this has several conceptual problems.
Imagine light falling from a flashlight onto a mirror on the ceiling of a stationary spacecraft. The light goes up, is reflected from the mirror and falls on the floor of the spacecraft. Let's say he covers a distance of 10 meters.
Now imagine that this spacecraft starts moving at a colossal speed of many thousands of kilometers per second. When you turn on the flashlight, the light behaves as before: it shines upward, hits the mirror and is reflected on the floor. But to do this, the light will have to travel a diagonal distance, not a vertical one. After all, the mirror is now moving rapidly with the spacecraft.
Accordingly, the distance that the light travels increases. Let's say 5 meters. It turns out 15 meters in total, not 10.
Despite this, although the distance has increased, Einstein's theories claim that light will still move at the same speed. Since speed is distance divided by time, since speed remains the same and distance increases, time must also increase. Yes, time itself must stretch. Although it sounds strange, it has been confirmed experimentally.
This phenomenon is called time dilation. Time moves more slowly for people who move in fast moving vehicles, relative to those who are stationary.
For example, time passes 0.007 seconds slower for astronauts on the International Space Station, which moves at a speed of 7.66 km / s relative to Earth, when compared to humans on the planet. Even more interesting is the situation with particles like the aforementioned electrons, which can travel close to the speed of light. In the case of these particles, the degree of deceleration will be enormous.
Stephen Colthammer, an experimental physicist at the University of Oxford in the UK, points to an example of particles called muons.
Muons are unstable: they quickly decay into simpler particles. So fast that most of the muons leaving the Sun should decay by the time they reach Earth. But in reality, muons arrive to Earth from the Sun in colossal volumes. Physicists have long tried to figure out why.
“The answer to this mystery is that muons are generated with such energy that they move at speeds close to light,” says Kolthammer. "Their sense of time, so to speak, their internal clock runs slowly."
Muons "survive" longer than expected relative to us, thanks to the present, natural curvature of time. When objects move quickly relative to other objects, their length also decreases, contracts. These consequences, time dilation and length decrease, are examples of how spacetime changes depending on the movement of things - me, you, or the spacecraft - with mass.
What is important, as Einstein said, does not affect the light, since it has no mass. This is why these principles go hand in hand. If objects could move faster than light, they would obey fundamental laws that describe how the universe works. These are key principles. Now we can talk about a few exceptions and derogations.
On the one hand, although we have not seen anything moving faster than light, this does not mean that this speed limit cannot theoretically be broken under very specific conditions. Take, for example, the expansion of the universe itself. Galaxies in the Universe are moving away from each other at speeds much faster than light.
Another interesting situation concerns particles that share the same properties at the same time, no matter how far from each other. This is the so-called "quantum entanglement". The photon will rotate up and down, randomly choosing from two possible states, but the choice of the direction of rotation will accurately reflect on the other photon elsewhere if they are entangled.
Two scientists, each studying their own photon, will get the same result simultaneously, faster than the speed of light would allow.
However, in both of these examples, it is important to note that no information travels faster than the speed of light between two objects. We can calculate the expansion of the Universe, but we cannot observe objects faster than light in it: they have disappeared from the field of view.
As for the two scientists with their photons, although they could get the same result at the same time, they could not let each other know about it faster than the light travels between them.
“This does not pose any problem for us, because if you are able to send signals faster than light, you get bizarre paradoxes according to which information can somehow travel back in time,” says Kolthammer.
There is another possible way to make faster-than-light travel technically possible: rifts in space-time that would allow the traveler to avoid the rules of normal travel.
Gerald Cleaver of Baylor University in Texas believes that one day we may be able to build a spacecraft that travels faster than light. Which moves through a wormhole. Wormholes are loops in space-time that fit perfectly into Einstein's theories. They could allow an astronaut to jump from one end of the universe to the other using an anomaly in spacetime, some form of cosmic shortcut.
An object traveling through a wormhole will not exceed the speed of light, but could theoretically reach its destination faster than light traveling along the "normal" path. But wormholes may not be accessible to space travel at all. Could there be another way to actively distort spacetime to move faster than 300,000 km / s relative to someone else?
Cleaver also explored the idea of an "Alcubierre engine" proposed by theoretical physicist Miguel Alcubierre in 1994. He describes a situation in which spacetime contracts in front of the spacecraft, pushing it forward, and expands behind it, also pushing it forward. "But then," says Cleaver, "problems arose: how to do it and how much energy would be needed."
In 2008, he and his graduate student Richard Aubosie calculated how much energy would be needed.
"We imagined a 10m x 10m x 10m spacecraft - 1,000 cubic meters - and calculated that the amount of energy needed to start the process would be equivalent to the mass of a whole Jupiter."
After that, the energy must be constantly "poured" so that the process does not end. No one knows if this will ever be possible, or what the required technologies will be like. “I don’t want to be quoted for centuries as predicting something that will never happen,” Cleaver says, “but I don’t see solutions yet.”
So, travel faster than the speed of light remains a fantasy at the moment. So far, the only way to visit an exoplanet during life is to plunge into deep suspended animation. And yet it's not all bad. In most cases, we talked about visible light. But in reality, light is much more. From radio waves and microwaves to visible light, ultraviolet radiation, X-rays and gamma rays emitted by atoms as they decay, these beautiful rays are all made up of the same thing: photons.
The difference is in energy, which means in wavelength. Together, these rays make up the electromagnetic spectrum. The fact that radio waves, for example, travel at the speed of light is incredibly useful for communication.
In his research, Kolthammer creates a circuit that uses photons to transfer signals from one part of the circuit to another, so he deserves a right to comment on the usefulness of the incredible speed of light.
“The very fact that we built the infrastructure of the Internet, for example, and before that the radio based on light, has to do with the ease with which we can transmit it,” he notes. And he adds that light acts as the communication force of the universe. When the electrons in a mobile phone start to shake, photons fly out and cause the electrons in the other mobile phone to shake too. This is how a phone call is born. The tremors of electrons in the Sun also emit photons - in huge quantities - which, of course, form the light that gives life on Earth warmth and, ahem, light.
Light is the universal language of the universe. Its speed - 299 792.458 km / s - remains constant. Meanwhile, space and time are malleable. Perhaps we should not think about how to move faster than light, but how to move faster through this space and this time? To mature at the root, so to speak?