# Why does the universe have a speed of light limit? What are the consequences when the speed approaches the speed of light infinitely?

The speed of light in the universe is 300,000 kilometers per second, so is the speed of light constant? The answer is yes.

One of the most important theories in Einstein's special relativity theory is that the speed of light is invariant, that is, the speed of light in vacuum is constant in any reference system, and the speed of any object is not greater than the speed of light.

# What happens when you approach the speed of light?

According to the famous physicist Albert Einstein's formula for prime numbers (as follows).

m₀ represents the rest mass of the object, m is the mass of motion obtained after the object moves, v represents the speed of motion of the object, c represents the speed of light, the larger v is, then the smaller the denominator (when v = 0, the rest mass is the mass of motion), the greater the mass of motion of the object in the case of constant rest mass.

So as v approaches c, the moving mass becomes infinite, and when the relative mass of an object is infinite, in turn, an infinite force is required to provide acceleration for the object to move, as inferred from Newton's mechanical equation of F = ma.

This infinite force, which cannot be found in real life for the time being, allows objects to approach the speed of light infinitely, and can only exist theoretically close, but in practice cannot approach infinitely, much less exceed the speed of light.

Theoretically, when an object moves at close to the speed of light, the length of the object is compressed, time is slowed down, and the mass increases infinitely.

For example, suppose that when a spacecraft travels close to the speed of light, people outside the spacecraft will see that the length of the spacecraft becomes shorter, or even tends to zero, while the mass of the spacecraft, including the astronauts, multiplies, and time becomes very slow.

In real life, analyzed from the perspective of special relativity, time slows down when people on Earth go to see astronauts in space.

Usually astronauts would fly at an altitude of 400 km above the Earth, and Earthlings would have the opportunity to see the astronauts doing movement at a speed of 7.7 km/s. Using atomic clocks on Earth, the astronaut's time in space would be 0.327 nanoseconds per second slower than on Earth, which would be 28 microseconds slower in a day and 10 milliseconds slower in a year.

So, from the point of view of the Earth's people, astronauts in space over time will be slower, but the time difference is too small, almost no difference, because the speed is far below the speed of light.

So what happens if humans fly faster than light? It's time to talk about the famous grandfather paradox.

# Results beyond the speed of light

As we have seen in many movies, if a person flies at FTL, then it will cause time to be turned back and the person can go back to the day his maternal grandfather and grandmother got married and killed his maternal grandfather so that there would not be his mother, much less his existence.

The question arises, if the man went back in time to kill himself, dead, how would he still be born and then time travel again? If there is such a thing, the cycle of karma will cease to exist, but it is not impossible.

Because objects that exceed the speed of light exist, such as the universe, which is expanding faster than the speed of light, what about this?

The diameter of the universe is about more than 90 billion light-years, about more than 90 billion light-years outside whether there is still outer cosmic space, temporarily unknown, but the universe since the big bang is only 13.8 billion years old, the diameter of the universe produces more than 6 times higher than the time of the birth of the universe, it is clear that the universe is expanding faster than the speed of light.
Some people may feel doubtful whether there is a problem with Einstein's theory about the constant speed of light, but there is no problem.

Einstein's theory of relativity is oriented toward solid matter in the universe, which cannot reach the speed of light as long as it has static mass, including humans.

And the universe is not, so far, scientists have not been able to fully deduce the cause and process of the Big Bang, so can not explain why the universe is expanding faster than the speed of light.

Through the Hubble Telescope, scientists had found that galaxies beyond the Milky Way are moving further and further away from the Milky Way, indicating that the universe is still expanding. One theory is that the cause of the expansion of the universe comes from matter that we cannot see, and this matter is known as dark matter.

In 1884, William Thomson estimated the mass of the Milky Way galaxy, but the budget turned out to be much larger than the actual observed stars, and he determined that there were some invisible stars in the galaxy.

In 1936, astronomer Sinclair discovered that stars farther from the center of the Virgo galaxy move at about the same speed as stars closer to the center of the galaxy.

According to the laws of gravity and celestial mechanics, objects at the center of galaxies move faster than those farther away, and Sinclair, like William Thomson, felt that there were invisible stars in the universe, and that such stars were "dark matter.

Today's scientific means can not observe the actual structure of dark matter, but scientists believe that there must be dark matter in the universe, and the energy of dark matter must be very huge, the matter in the universe can be stable movement is because of the existence of dark matter, but also the expansion of the universe faster than the speed of light.

Imagine if mankind can unravel the mystery of dark matter as soon as possible and make full use of the properties of dark matter, saying that it is not possible to really travel beyond the speed of light, instead of staying in theory.

In addition to the expansion of the universe can be "super speed of light", the speed of quantum entanglement is also beyond the speed of light, even 10,000 times faster than the speed of light. So what exactly is quantum entanglement and why is it so fast?

Quantum entanglement is a phenomenon that arises when two or more particles interact, even though these particles are separated from each other in space, they can affect each other.

The most amazing thing about quantum entanglement is that if one quantum is in the sun and another quantum is in Mars, if you change the state of one quantum, the state of the other quantum will also change. However, quantum entanglement does not transmit information and does not make objects move, so it does not violate the principle of invariance of the speed of light.

With the development of science and technology, human cognition of the universe and astrophysics is always in constant innovation, constantly learning among, nothing is absolutely correct theory, only in a particular condition, temporarily not overturned it. Even Einstein's theory about the constant speed of light is only a hypothesis.

Let's just say that the answer to the question of whether there is really a limit to the speed of light is, for the time being, with today's scientific development and human cognition.

Just like 1966 was the year of Newton's miracle, 1905 was the year of Einstein's miracle, perhaps in the near future there will be a new miracle year in physics, telling us that there is no limit to the speed of light, so it may not be difficult for humans to fly close to the speed of light or even beyond it, and the time travel plot in movies can become a reality.

Author: Zi Zi Primary Reviewer: Ding Zi Children Proofreader: Xiao Wan