How can people look up and see stars hundreds of light-years away? Is the human eye faster than the speed of light?
The reason why human beings have been able to step by step from the establishment of civilization to today has a great relationship with our ability to accumulate and inherit experience and knowledge . Most of the knowledge we learn in life and school does not require us to experiment and discover, but to learn the "ready-made" knowledge summarized by our predecessors.
If it weren't for the accumulation of human beings from generation to generation, with our personal brain capacity and length of life, it is obvious that we can only "step on the spot" forever. From this we can see how important the education of human society is. Whether it is family education or school education, it is one of the basic conditions for us to become a qualified modern human being .
We have learned the basic principles of materialist dialectics in school and know that everything in the world is in constant motion and change. The process of these changes constitutes what we know as "history" . To be precise, history is also one of the experiences passed down by human beings from generation to generation. We can learn from these experiences and acquire knowledge. Therefore, it is very necessary for a person to learn and understand history .
Time is constantly moving forward, and history is something that we cannot go back to. So have you ever thought that we can actually see "history" all the time ? It exists nowhere else but in the sky above us.
our ancient universe
Humans are a creature that lives on the earth, and it has been about five million years since the birth of the species. This time is very long compared to a human life, but it is very short for our planet . Earth itself is 4.6 billion years old and is a planet that has existed since the birth of the solar system.
When the earth was just born, the environment was very harsh, and life appeared after about one billion years , that is to say , the history of life on the earth was about 3.5 billion years . In this process, life on earth has gone through many extinctions and evolutions , and it is not in its "final form" until now, it is still in constant evolution .
But compared with the age of the universe, the earth is also a "child". According to scientists' continuous research on the universe, it is basically determined that our universe was born in a big bang 13.82 billion years ago. Matter spews out of the "singularity" and keeps expanding .
According to the researchers' calculations, the current universe is still expanding, and matter is moving away from each other. Maybe one day, the matter in the universe will become so thin that it will eventually reach the critical point of "heat death" . As for what happened at that time, scientists have made a lot of speculation, but now it is impossible to determine how the universe will end.
fastest speed in the universe
Our material universe is constantly moving, and since it is moving, there will naturally be differences in speed. So, do you know what the fastest speed in the universe is? That is the speed of light. The specific value of the speed of light is 300,000 kilometers per second, and it only takes more than eight minutes to travel from the earth to the sun .
The speed of light is the most ideal speed in the universe, and it is actually affected by various substances, just as "absolute zero" can only be reached in a complete vacuum . But for us, the speed of light is not just a concept, it can also be used as a unit for us to measure distance .
For us, all distances in the universe are very "exaggerated", and if we use the distance units we use on Earth to measure, then the numbers will become very complicated. Therefore, researchers use the distance that light travels in the universe for a period of time as a distance unit. For example, the "light-year" we often hear is not a time unit, but the distance that light travels in a year .
However, some people have also raised the question: When we look up at night, we can see stars hundreds of light-years away. Does it mean that our "vision" is faster than the speed of light? So why is the speed of light the fastest speed in the universe?
How the human eye sees objects
In fact, this question is "not established", because it is a misunderstanding of our senses . Compared with some other animals, humans are not particularly prominent in any one sense, but our advantage is "average" . For example , animals such as dogs and cats have developed senses of hearing and smell, but they do not have human vision, and many colors cannot be distinguished well .
So how exactly do our eyes work? First of all, we need to make it clear that human beings do not have a real "vision", which is just a description of the direction of our gaze. The human eye is not a "transmitter" in essence, but an out-and-out "receiver" .
The human eye is a very complex structure, mainly composed of cornea, pupil, lens, retina and other parts . The light first enters through the pupil, and the human body will automatically adjust the amount of light received by the pupil according to the intensity of the light . For example, under strong light , our pupil will shrink , and in a weak light environment, it will enlarge .
Through the pupil, the light will enter the lens, this tissue is equivalent to a lens , which can adjust the size, direction and so on of the image of the object . After a simple process of light, the retina accepts this information.
The retina is like a "converter" . After our lens transmits light signals, these signals are converted through the retina into bioelectrical signals , which are then transmitted to the brain through our complex optic nerve, and the brain responds .
Although the process looks complicated, it is actually so fast that we hardly feel the time it elapses . That is to say, there is no "vision" in our eyes, we just passively receive the light signals in nature, and then transmit them to the brain to form everything we "see".
celestial changes
After understanding the working principle of our eyes, I believe everyone understands that the reason why we can see stars hundreds of light-years away is because the light they emit is constantly transmitted in the universe , even if we Don't look at it, it's always there . If we feel that it does not exist without looking at it, then we have fallen into the misunderstanding of idealism.
From this perspective, what we see is only the light emitted by these stars hundreds of years ago . With the continuous expansion of the universe and the continuous movement of the celestial bodies themselves, they may no longer be "seen" by us at this moment. That location .
Celestial bodies are constantly changing, and in addition to changes in position, there are also changes in shape. All matter cannot be "eternal", and celestial bodies are no exception . For example, our star , the sun , is now experiencing the prime of a star . After about 5 billion years, it will end its life as a main sequence star and continue to expand into a red giant star. At that time, the entire solar system will be destroyed by it . devour .
According to this theory, the stars we see when we look up in the sky may have taken their own lives hundreds of years ago , but we have no way of knowing now. From this point of view, the vastness of the universe is beyond our imagination.
beyond the speed of light
Although the speed of light is the fastest speed of matter in the universe, it does not mean that there is no existence beyond the speed of light. As a simple example, the universe is expanding faster than the speed of light . According to scientists' calculations, the diameter of our observable universe is about 93 billion light-years , which obviously exceeds the speed at which light travels in the age of the universe.
Not to mention that there is a huge unobservable universe outside the observable universe, which shows that the expansion rate of the universe itself is amazing . Since the universe is so vast, will we never have the opportunity to roam freely in space? In fact, we can think from a different angle.
The aircraft that humans are making now can’t even reach the speed of sub-light, let alone the speed of light. But even at the speed of light, we have no way to travel freely between galaxies, because hundreds of years are too long for human life .
For this reason, some scientists have also proposed that we don't have to blindly speed up the absolute speed, but should start from another angle and directly use antimatter to fold and distort space to complete the transition , just like an artificial "wormhole". If we master this technology in the future, then the vast cosmic space will no longer be able to restrain us, and human beings can travel freely in space.