We all know that the limit speed of the universe is 29,977,92,450,8 meters per second. This speed is the highest speed that any form of energy in the universe can reach. The gravitational wave we measured is at this speed, and light is also at this speed in vacuum. In theory, gluon should also be at this speed! It can be seen that this speed is not a patent of light, but that all massless particles are born to reach this speed!
But the particles that make up our real world, including protons, neutrons and electrons, no matter how hard we try, there is no way to accelerate them to the speed of light. The reason is simple, because they have quality.
This is Special Theory of Relativity tells us the reason, then why can't mass objects reach or exceed the speed of light? The special theory of relativity says that as a mass object approaches the speed of light, its relativistic mass will tend to infinity, so we cannot accelerate a mass object to the speed of light.
This explanation seems to say nothing, it is more like a further emphasis on the limit of the speed of light, and does not say the essential reason why cannot exceed the speed of light . Therefore, the essential reason for not being able to exceed the speed of light, we don't know now.
Therefore, the limit of the speed of light of a mass object can be regarded as a basic principle in physics, and the basic principle can also be regarded as an axiom. There is no way to prove it, and there is no need to prove it, which means that our world is like this of.
Does it feel a bit unreasonable, but it is not. This is the general method of human scientific development, called the axiom system. At present, the limit of the speed of light meets our logical requirements,It is also in line with our observational empirical evidence, so we can consider it an axiom that does not need to be proved.
But you can completely assume that the axiom of the limit of the speed of light is wrong, and then perform a logical deduction on the basis of this new axiom you assume, and then draw a series of theorems. If your entire theoretical system is perfect and self-consistent, And in accordance with observational evidence, it means that under certain circumstances, mass objects can exceed the speed of light.
This is like Lobachevsky back then, he felt that the fifth axiom of Euclidean geometry , the axiom of parallel lines was problematic, he assumed it was in a plane , Passing a point outside the straight line, at least two straight lines can be made parallel to the known straight line.
Then, based on this new axiom, a series of logically self-consistent theorems are derived, and they are not contradictory. This is hyperbolic geometry , or saddle geometry.
However, if you assume that the limit of the speed of light is wrong, then this path will definitely not work. As long as you assume that mass objects or information can exceed the speed of light, you will definitely encounter logical difficulties.
Because it is faster than light, it violates the law of causality. The law of causality is the bottom structure of our real world. If there is no law of causality, you will see the missile explode first, then launch, the target is shot first, and then shot, etc. These logically confusing things.
Back then Einstein insisted on the principle of the limit of the speed of light because of one consideration, and then used formulas in the special theory of relativity to limit the possibility of mass objects exceeding the speed of light, and his special theory of relativity itself emphasized the law of cause and effect. theory.
Quality Speed
We all know that,In 1935, Einstein also used the principle of the speed of light to make an EPR paradox to attack quantum mechanics , saying that quantum mechanics was not complete. Einstein thought at the time that even if your quantum mechanics violates the determinism of reality, you can never exceed the speed of light, and you can never violate the law of causality, but I did not expect that quantum mechanics is really faster than the speed of light. The speed of light here is what we call quantum. Entanglement.
Quantum entanglement is totally a mystery to us at the moment. We don’t know what is entangled, why is it entangled, and what is the mechanism behind the entanglement? I don't know at all, but it is currently believed that this kind of entanglement, because the randomness of quantum cannot convey any useful information, it does not violate the principle of the limit of the speed of light, and of course it does not violate the law of causality.
In fact, the above is the best understanding of the principle of the limit of the speed of light. But I know that some people are not satisfied with this explanation. Then take a look at the following. It actually limits the energy that particles can carry. This is also considered a limitation of the speed of the universe. Before talking about this, let's review the speed limit of human beings.
In the large hadron collider , the speed of protons reached 29,907, 92,455 meters per second, this is human The fastest proton created. But this is not the limit of human speed.
has a particle that is 1836 times lighter than a proton, so it is much easier to accelerate it than a proton. This is the electron. In LEP, the predecessor of LHC, humans accelerated the electron to every The second is 299,907, 92,450, and 7.9964 meters, which is only 3.6 mm/sec slower than light in a vacuum.
It can be said that the speed of light is almost reached. Humans are really cows. What's the difference? Of course it is energy. On the earth we use chemical energy. The energy of the accelerator is at the Gev level. This G is called Kyrgyzstan, which is 10⁹, which is also called one billion electron volts .
Then there are many naturally formed accelerators in the universe, such as the material jets of massive black holes, supernova explosions, neutron star collisions, etc. These super-high energy explosion events, they will all produce a large number of explosions. cosmic rays, these cosmic rays are basically composed of protons. Compared with these natural accelerators, the LHC built by people is almost like a toy for preschoolers.
Now what we see is the jet of matter from the black hole in the center of the galaxy M87 . The magnetic field there is billions of times stronger than the magnetic field created by humans.
The highest energy of their accelerated particles cannot be expressed in Gev, but Tev, which is called too electron volt, which is 10^12 ev, and even Pev, which is called beat electron volt. It is 10^15 ev, and it will even soar all the way to more than 10^19 ev!
Think about it, our Gev on the earth, 10⁹ all accelerate the proton to the speed of light, then 10^19 ev in the universe, Don't send the proton directly to the sky.
However, according to the cosmic rays we receive on Earth,The energy of all protons seems to have a threshold, and the energy they carry does not exceed 5×10^19 eV.
Something seems to limit the energy of protons. In other words, if the universe does not allow the energy of protons to exceed this energy, if the energy cannot be increased, then the speed will definitely not rise.
Finally, we give an explanation. There are a large number of photons dispersed in the space of the universe. The average temperature of these photons is only 2.7 K, so the photon energy of each is only about 0.00023. Electron volts, this energy is very small, this is the microwave background of the universe.
Although its energy is very small, when some charged particles carrying huge energy shuttle through the universe, it will interact with these photons to produce some new particles.
For example, when the energy of an electron-carrying particle reaches 10^17ev or more, it will produce positive and negative electron pairs in the collision with the microwave background photon, and then lose energy, because the electron quality is relatively low , So this energy loss process is relatively slow.
But when the energy of an electron-carrying particle reaches 5×10^19 eV or more, a neutral pion will be produced. The mass of a neutral pion is 264.1129 times that of an electron, so every neutral pion The generation of will consume 135Mev of energy, Mev is one million electron volts, 10⁶.
This energy loss is faster, so when the energy of a charged particle is higher than 5×10^19 eV, the universe will quickly drop it below this energy, so we found it on Earth None of the cosmic ray energy exceeds this value.
This threshold is the so-called GZK limit of charged particles.Then this limit for the speed of the proton means that it can reach 299,997, 922,450, 7.99999999999999999999918 meters per second.
This speed can be said to be no different from the speed of light. If we now race such protons and photons to Proxima Centauri, the protons will only lag behind by 22 microns, and after 700 femtoseconds it will be Will reach.
If you let them go to the and Andromeda galaxy , 2.54 million light-years away, the distance is about 5 million light-years, and the protons will be about 13 seconds slower. It can be said that such protons have run almost as fast as photons.
So according to the GZK limit, in a universe full of microwave background photons, it is impossible for us to reach the speed of light, because we are composed of protons, neutrons, and electrons, and traveling faster than light is also very dangerous, you think Now, when we interact with photons in the microwave background, the universe appears to us as a big oven. We are chicken wings.
If you cannot accept the causality as the reason for the limit of the speed of light, then you can use the GZK limit as a good explanation.
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