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We all know that according to the theory of relativity of Einstein , mass objects can't move faster than the speed of light. However, since the birth of 13.8 billion years ago, the universe is expanding rapidly at the superluminal speed !
Moreover, the speed of other galaxies in the universe is much faster than the speed of light. Is it because the theory of relativity is wrong? Or is this a paradox at all?
Cosmic superluminal expansion
Now the more mainstream theory of origin of the universe is the Big Bang theory.
In 2015, scientists simulated the Big Bang and Inflation model, and used the most accurate Hubble constant as the parameter value determined by the Planck satellite as the parameter value to derive the approximate age of the universe, which is 137.87±0.2 billion years old.
In other words, if the Big Bang theory is true, then it should have been about 13.8 billion years since the singularity of exploded in an instant, and everything in the universe was born.
The ancients said, "Arguing about the sky has a head and a foot", but why can't you see the boundaries at all when you look at the universe tens of billions of light years away?
First, let’s talk about what light-year is. As the name suggests, light years are the distance that light moves forward one year.
Einstein mentioned in the theory of relativity that with time and space as the axis, the combined speed of any matter traveling through time and space is equal to a constant value, that is, the speed of light.
Because photon has no mass, if the photon travels through space and space at the speed of light and the spatial distance is pulled full, the time taken is zero.
Therefore, no matter when moving or transmitting information, it cannot exceed the speed of light. The speed of light is the upper limit of the speed of all matter in the universe.
Because of the eternal nature of the speed of light, astronomers chose to use it as the cornerstone to measure the distance between celestial bodies in the universe using light years. So since the universe has been born 13.8 billion years, starting with the singularity, photons should also go outwards to a distance of 13.8 billion light-years.
The diameter of the universe is only 27.6 billion light-years at most. Why is the diameter of the universe calculated by scientists about 93 billion light-years? Is it that scientists have calculated it wrong, or is the universe expanding outward at superluminal speed? Is the theory of cosmic explosion contrary to the recognized theory of relativity?
It turns out that the reason why humans accept the fastest speed of light is because it can explain most physical phenomena. But the universe is not a uniform sphere as we imagined, but a structure similar to a film.
The substance inside it exists neither balanced nor flat.
Therefore, unlike the scope of application of the theory of relativity in the static universe, in the ever-expanding, bending and rippling space and time, objects may break through the speed of light!
is a vivid metaphor. Some people say that celestial bodies float on the surface of the universe, and the internal forces of the universe are like waves, pushing wave after wave, surfboards floating on the water surface move forward.
In this way, for the expansion of the universe itself, even if the speed of light is the speed limit in relativity, it seems that it is no longer so insurmountable. In other words, this is originally two concepts that do not intersect. The super-light expansion of the universe does not violate the theory of relativity.
At this point, a more interesting question arises, that is, why does the universe expand at superluminal speed, and where is the center of the universe's expansion?
Where is the expansion center
It all says that the universe is in expansion, so how does it expand, and where is the expansion center?
According to the predecessor of the Big Bang theory, the native atom expansion theory, the universe existed in a very small space at the beginning.
In the 1930s, radio astronomy emerged. Astronomers compared the synthesis ratio of the original nebula matter in Milky Way with the initial state of the Big Bang and found that the data were very close.
Then, the cosmic microwave background radiation generated by the Big Bang was also observed.At this point, the Big Bang theory has basically been proven.
And with Hubble's observations for more than ten years, the fact that the distant universe is leaving quickly has also been proved, which is the famous Hubble Redshift.
The so-called redshift phenomenon refers to the wavelength of light emitted by galaxies or celestial bodies. It stretches and becomes longer due to constant distance, which in our opinion is red.
uses balloon as an example. When we mark two non-adjacent points on the surface of the balloon.
When the balloon expands, the distance between points will be lengthened, but the actual position of each point relative to the balloon remains unchanged. Moreover, this kind of distance will accelerate as the distance continues to expand. This is the accelerated expansion of the universe!
Where is the central point of the expansion of the universe? Is it the singularity of the Big Bang?
Quantum Mechanics believes that the singularity is not originally in an empty space. The so-called "vacuum" is not actually empty, and it should be filled with ubiquitous absolute particles.
The universe initially had no space, and it was the continuous boiling of this particle that inspired space. Over time, the spatial structure continues to grow and expand, becoming larger and larger.
It is worth noting that space can expand at any speed because space is neither matter nor energy.
The super-light regression behavior observed by scientists in galaxies is caused by the expansion of space itself. So expansion is not limited to a certain point, but is everywhere.
Here we do a reverse deduction. If the expansion center is a point in the space where the big explosion occurs, then the cosmic background radiation generated by the big explosion, that is, the earliest light, should start from a point, and we can only see the light in the space radiating from this point.
But in fact, light is everywhere. The cosmic microwave background radiation in the universe can be said to be very uniform.
This also shows that these lights radiate from various points in the universe. Therefore, the center of expansion is not limited to one point, the universe is full of expansion centers.
Of course, there is another possibility, that is, the center of the universe exists in the folds of curved space and time somewhere, which will be a higher dimension that we cannot see.
is still unattainable with the current theoretical depth and detection level of human beings. Since the expansion center cannot be found, does it mean that the expansion of the universe is uncontrollable?
Will the expansion of the universe stop
The ultimate future of the universe, will it accelerate the expansion to a large tear, or will it stop suddenly?
Through observations of the GN-Z11 galaxy, the most distant celestial object observed by humans so far, astronomers discovered that this celestial body, which was formed within 400 million years after the birth of the universe, has now expanded to 30 billion light years away!
You should know that the implementation of celestial bodies in the universe is not really about flying away from each other.
only expands the space itself! The position of each celestial body in space is actually relatively fixed.
So it can be judged based on the redshift value of the universe , that the universe expands at super light speed! Moreover, the universe does not expand at the overall superluminal speed, but only exists in the edge areas of the universe.
is used to swipe dry buckets in a washing machine to compare, which is easier to understand. The molecules that are located outside the center circle away from the movement trajectory of the drum will accelerate due to the increase in the rotation radius, and the water molecules will be thrown out first.
Then where does the universe begin to surpass 's first cosmic speed and begin to expand at super-light speed?
Scientists calculated the expansion rate of the current 13.8 billion light-years based on the Hubble constant. It is 284,254.6 km/s, slightly slower than the speed of light.
Based on this calculation, the modern universe should have begun to expand beyond the speed of light at about 14.5 billion light years away! Moreover, as early as 1998, two scientific teams discovered that from a point of time, the universe has begun to expand at an accelerated rate of 4.5 billion years ago.
It is speculated that during the period of surge, the expansion speed of the universe can expand by 10ˆ26 times in an instant, which is really incredible! Therefore, the expansion speed of the universe is an order of geometric magnitude increase.
It seems that after 13.8 billion years of expansion to 92 billion light years, it is no wonder! Will the universe continue to expand in the future?
Some people speculate that the universe will expand to its limit like a balloon, causing a big tear, and some people believe that according to Einstein's famous equation, E = MC^2, we can know that weight and energy can be converted to each other.
So the expansion of the universe is limited, and it may one day in the future, the universe will stop expanding.
If the universe is "closed" shape, substituting the relevant calculations can be seen that when the residual mass of the universe is equal to the loss mass of the universe and equal to one-half of the total mass of the universe, the space radius of the universe reaches the maximum.
At that time, the universe will stop changing, collapse in place and move towards destruction, thus opening a new cosmic cycle.
But how will the universe end? We humans really can't wait for that day.
only hopes that humans can one day break through the existing limitations, try to surpass the speed of light, and build a Doraemon time machine. Because I want to go back to the past and see myself when I was a child.
