But in fact, this stone has aroused another kind of ripple that you can't feel at all. This ripple is formed by the fluctuation of time and space and spreads around at the speed of light.
Where it passes, time and space will be stretched, and all objects existing in time and space will also be stretched, and the name of this ripple is already familiar to you-
Gravitational waves were first proposed by Henry Poincare in 1905. Based on the idea of Lorentz transformation, according to Poincare's inference, all objects will produce gravitational waves when they move, so you are always shrouded in gravitational waves.
But gravitational waves are invisible and intangible, and there is no way to prove them at all, but they seem to exist in theory and are everywhere. Another thing with the same characteristics as it is a ghost, so Poincare put forward the idea of a ghost.
10 years later, Einstein's general theory of relativity was born. This great theory more clearly predicted the existence of gravitational waves, and at the same time successfully pushed gravitational waves to the hot search, with many guns ... Oh, no, a large number of scientists participated in the research and discussion of gravitational waves.
Emmm…… ............ Anyway, it's about whether there are gravitational waves.
Interestingly, the general theory of relativity clearly predicted the existence of gravitational waves, but Einstein himself was once at odds with his own theory.
1936, he wrote a letter to his friend, German physicist Max Born, in which he said that after careful study, he and nathan rosen found that gravitational waves were only a mathematical illusion reflected in the gravitational field equation, but actually did not exist at all.
Also in the same year, he submitted a paper in american physical society's scientific magazine Physical Review, detailing his and Rosen's research conclusions. Generally speaking, once a gravitational wave is formed, it will collapse into a singularity under its own gravity, instead of carrying real energy in space as predicted by general relativity.
In other words, Einstein's position at that time was that although my theory showed that gravitational waves should exist, I personally proved that gravitational waves could not exist. Do you find it irritating?
But in the end, instead of making others angry, Einstein was very angry. As his paper failed to pass peer review, it was anonymously rejected by Howard Robertson as soon as it was published. Robertson also attached a note to the manuscript, indicating that there were mistakes in the paper, and asked Einstein to take it back and check and revise it himself. Knowing der's general theory of relativity, it's quite emotional to think about where you are wrong.
When it was published, Einstein was very angry and his paper was rejected. I don't know who did it, so he vowed never to publish a paper in Physical Review again.
Fortunately, the Polish physicist leopold infeld, who was Einstein's assistant at that time, had always been in contact with Robertson, so under his mediation, Einstein finally accepted Robertson's opinion, and after recalculation, he admitted the existence of gravitational waves.
Of course, Einstein never knew that Robertson rejected his paper. What would happen if he knew ... er ... didn't know?
However, although Einstein acknowledged the existence of gravitational waves, he always thought that gravitational waves were too weak to be detected at all. Einstein was actually right on this issue. As far as the weakness of gravitational waves is concerned, it is indeed impossible to be detected.
I know that when I say this, many people can't help asking, hey, buddy, aren't you all connected to the internet in the village? Isn't that thing detected by LIGO at 20 15? Who says it can't be detected
Indeed, gravitational waves have been detected twice by LIGO, but in this case, we can't say that Einstein underestimated the skills of future generations. We can only say that those physicists who engage in gravitational waves are really awesome. They really accomplished an impossible task.
Note that I said "impossible in the true sense", which means that I have never exaggerated or deliberately rendered it.
Because many people know that LIGO is composed of two perpendicular metal pipes with a length of 4 kilometers, and the information it detected at that time was that one of the pipes was stretched to the power of 10 at the moment when gravitational waves passed. This figure means that the stretched length of the pipeline at that time was only11000 of the proton diameter.
Protons are subatomic particles that make up the nucleus. The volume of a nucleus is only 100 billion times that of an atom, and protons are much smaller than nuclei. Then think about it. What is the concept of one thousandth of its diameter?
If you really can't figure it out, let's just say that even if you stand next to LIGO's interference arm and shout, its amplitude is hundreds of billions of times larger than the stretch caused by that gravitational wave.
It is difficult to measure such a small length change, but after thinking of a sensitive method, it is tantamount to dreaming to distinguish gravitational wave signals from various environmental disturbances.
For example, I put you in a wooden bucket and then drop a drop of water on it. You need to measure the time when the water drops fall through the vibration of the barrel, and most importantly, the barrel is placed in heavy rain.
In other words, you have to find a way to measure a specific drop of water through almost nonexistent slight vibration when the barrel keeps raining-this is the task that LIGO needs to complete. Therefore, it is obvious how impossible it seems to detect gravitational waves.
Because of this, when LIGO was first put forward, many people said-
However, this seemingly impossible task was completed by LIGO on September 20 15 14-when the news was announced, the whole world was boiling for it.
What used to be a fable has now become a reality, and mankind has finally seen the dawn of catching gravitational waves. It was followed by a series of gravitational wave detection plans, such as Einstein Telescope Plan in Europe, Cosmos Explorer Plan in the United States, KAGRA Plan in Japan, Ali Plan in China, Taiji Plan and Qin Tian Plan. Gravitational wave research has entered a new era from previous papers.
But the question is, why should we go to so much trouble and spend a lot of money to capture such a weak signal?
When we look up at the night sky, except for the bright moon and those bright stars, the rest is endless darkness. However, in these seemingly empty spaces, there are many answers that human beings are looking for.
From the day of the Big Bang, something happened all the time in the universe, such as the formation of galaxies, the disappearance of celestial bodies, the collision of black holes and even the birth of the universe itself.
Some just happened, some happened millions, tens of millions, even billions of years ago, and the information related to these events may not always be radiated in the form of electromagnetic waves, or the electromagnetic waves radiated by them will never come to the earth for various reasons.
For this kind of event, even if we build the most advanced astronomical telescope, it will not help.
It's like throwing you into a dark cave with your ears covered, and you won't know anything that happens in the darkness of the cave. But once you have sound, you can see these secrets through another information carrier besides light.
On the other hand, gravitational waves have characteristics very similar to sound. They carry information in space, which is difficult to be blocked by objects such as electromagnetic waves, so they can present us with many ancient information that electromagnetic waves can't bring, and give us a chance to spy on more cosmic events.
For example, the first gravitational wave signal detected by LIGO tells us that there are not only double black hole systems in the universe, but they also merge into a larger new black hole after collision, and this ancient event that happened 65.438+0.3 billion years ago, only gravitational waves can tell us, because it is a story between two black holes, and electromagnetic waves have no chance to escape from them.
Therefore, it is of great significance to study gravitational waves. The breakthrough of gravitational wave detection technology and the establishment of gravitational wave observation station are like a pair of clairvoyance after we have a telescope.