真空真的是“虚无”吗？真空的奥秘超出了我们的想象

Vacuum literally means "nothing", but such a vacuum does not exist. The definition of vacuum in physics is a state of complete nothingness except time and space. In other words, a state where there is only time and space and nothing else is a vacuum.

真空，从字面上来理解就是“什么都没有”，不过这样的真空是不存在的。物理学上对真空的定义是，除了时空之外，完全虚无的状态。也就是说，只有时空，其他什么都没有的状态就是真空。

So does such a vacuum exist?

那么这样的真空是否存在呢？

Ancient humans were very curious about vacuum, but the level of science and technology at that time was greatly limited, and people's understanding of vacuum was mostly at the level of thought experiments, and even philosophical thinking was needed to understand vacuum.

古代人类对真空就很好奇，不过当时的科技水平受到很大限制，人们对真空的认知更多的只停在思想实验层次，甚至需要哲学思想去理解真空。

Humanity's real understanding of vacuum began in the 17th century. In 1641, physicist Torricelli conducted such an experiment, which was very simple.

人类对真空真正的认识开始于17世纪。1641年，物理学家托里拆利做了这样的实验，实验很简单。

He filled a one-meter-long tube with mercury, blocked the opening of the tube with his hand, and placed it upside down in a tank filled with mercury. He then found that the length of the mercury in the tube dropped to 76 centimeters, and a 24-centimeter vacuum state appeared at the top.

一根一米长的管子注满水银，然后用手堵住管子的开口，倒放在装满水银的槽里。之后他发现管里的水银长度下降到76厘米，最上端出现了24厘米的真空状态。

In fact, this is the earliest barometer. So is the vacuum environment 24 cm above the water pipe really a "vacuum"?

其实这就是最早的气压计。那么水管上面24厘米高的真空环境果真是“真空”吗？
原创翻译：龙腾网 https://www.ltaaa.cn 转载请注明出处

Now we know that the local area 24 centimeters high cannot be a vacuum, because although it seems that there is nothing, the universe is full of electromagnetic waves of various energies, which can easily penetrate obxts. So the environment 24 centimeters high will not be a vacuum, various electromagnetic waves will pass through there, and there are neutrinos that we cannot see, they are everywhere.

如今我们知道，那24厘米高的局部不可能是真空，因为虽然看起来什么都没有，但由于宇宙中充满了各种能量的电磁波，它们能轻易穿透物体。所以那24厘米高的环境不会是真空，各种电磁波会穿过那里，还有我们看不到的中微子，它们无处不在。

So, if all electromagnetic waves, neutrinos and other microscopic particles are removed, will the remaining environment be a vacuum environment?

那么，如果把所有的电磁波，中微子等微观粒子全部去除掉，剩下的环境就是真空环境了吗？

It is not. Although from a macroscopic perspective, it seems that there is only time and space and nothing else, if we continue to magnify the so-called vacuum and reach the microscopic world, we will find something different.

同样不是。虽然从宏观上来看，好像只有时空，其他什么都没有了，但如果我们把所谓的真空不断放大，到了微观世界，我们就会有不一样的发现。

Because at the quantum level, the vacuum is far more complex than we imagine. Even if we can remove all matter from the vacuum, or even make the vacuum temperature reach absolute zero, the vacuum will not be an absolute vacuum.

因为在量子层面，真空远比我们想象的更复杂。即便我们能去除真空中的一切物质，甚至让真空的温度达到绝对零度，真空也不会是绝对的真空。

Quantum field theory, which is based on quantum mechanics, believes that the so-called vacuum is actually filled with different types of quantum fields at all times, and each quantum field corresponds to a fundamental particle. Normally, the quantum field is in the ground state, which is also the most stable state, like a calm sea.

基于量子力学发展起来的量子场论认为，所谓的真空，其实时刻充斥着不同类型的量子场，每种量子场都对应着一种基本粒子。通常情况下，量子场处于基态，也是最稳定的状态，就像风平浪静的大海一样。

However, according to the uncertainty of quantum mechanics, the uncertainty of time and energy must not be less than a constant, which means that the quantum field in the ground state must fluctuate, and the more time, the greater the energy fluctuation. Just like the temperature cannot reach absolute zero and the speed cannot exceed the speed of light, the quantum field cannot be completely in the ground state, it must be disturbed and become an excited state.

不过根据量子力学的不确定性，时间和能量的不确定性必须不小于一个常数，这意味着处于基态的量子场一定会存在波动，而且时间越多，能量波动就越大。这就像温度不可能达到绝对零度，速度不可能超越光速一样，量子场也不可能完全处于基态，它一定会受到扰动从而成为激发态。

At a certain moment, the fluctuation of the quantum field may be very large, so that a pair of virtual particles and antiparticles can be derived out of thin air in the vacuum. This does not violate the law of conservation of energy, because the derived virtual particles and antiparticles will be annihilated and disappear instantly.

在某一瞬间，量子场的波动可能非常大，这样真空就能凭空衍生出一对正反虚粒子，这并不违反能量守恒定律，因为衍生出来的正反虚粒子会瞬间湮灭消失。

The reason why they are called "virtual particles" is that we cannot directly observe their existence. They are somewhat different from real particles. Strictly speaking, virtual particles are not particles.

之所以被称为“虚粒子”，就是因为我们不能直接观测到它们的存在，与真实存在的粒子有些不同，严格意义上来讲，虚粒子并不是粒子。
原创翻译：龙腾网 https://www.ltaaa.cn 转载请注明出处

You may ask: Since we can't see virtual particles, how can we be sure of their existence?

你可能会问：既然看不到虚粒子，怎么确定它们的存在呢？

Although we cannot see them, we can confirm the existence of virtual particles based on their interaction with real particles. The specific process will not be described in detail here.

虽然看不到，但我们可以根据它们与真实存在的粒子发生作用，进而确实虚粒子的存在。具体过程这里就不详述了。

In general, the vacuum is not empty, and the vacuum also has energy, which is the so-called "vacuum zero-point energy". There are vacuum fluctuations in the vacuum at all times, which looks like a calm sea surface suddenly becoming turbulent.

总的来说，真空不空，真空也拥有能量，也就是所谓的“真空零点能”，真空中时刻存在真空波动，看起来就像是平静的海面突然变得汹涌澎湃一样。

Not only does the vacuum have energy, but the amount of energy it has is also relative. In other words, there are different levels of vacuum, some vacuums are relatively empty, while others are not so empty.

真空不但拥有能量，而且拥有的能量多少还是相对的。也就是说，真空也有等级之分，有些真空相对来讲比较空，而有些真空就不那么空。

The famous physicist Casimir once conducted such an experiment in 1948. He placed two thin metal sheets close to each other in a vacuum. Since the metal sheets were not charged, they would not attract or repel each other.

著名的物理学家卡西米尔曾经在1948年做过这样的实验，在真空中让两张薄金属片相互靠近，由于金属片不带电，所以它们不会相互吸引或排斥。

However, when the metal sheets were close enough, something strange happened. The two metal sheets actually began to move closer to each other, as if gravity was generated between them.

不过，当金属片靠得足够近的时候，奇怪的事情发生了，两张金属片竟然开始相互靠近，好像两者之间产生了引力一样。

This is actually the Casimir effect. It is not that the metal sheets attract each other, but because the two metal sheets are close enough, the fluctuations on the inner side will be restricted, and only the fluctuations with shorter wavelengths can exist. The fluctuations on the outer side of the metal sheet will not be restricted at all.

这其实就是卡西米尔效应。并不是金属片相互吸引，原因在于，由于两张金属片靠得足够近，内侧的波动会受到限制，只有波长更短的波动才可以存在。而金属片外侧的波动不会受到任何限制。

Therefore, the fluctuations on the outside will be more numerous and more violent than those on the inside, and more virtual photons will be derived from the outside, which will in turn squeeze the metal sheets and bring the two metal sheets closer to each other.

于是外侧的波动就比内侧的波动更多更剧烈，外侧衍生出来的虚光子就会更多，进而挤压金属片，让两张金属片相互靠近。

So is there any way to turn virtual particles into real particles that we can observe? So that we can get energy out of nothing? In theory, it is indeed possible to turn virtual particles into real particles, but it is not possible to get energy out of nothing.

那么有没有什么办法让虚粒子变成我们能观测到的真实粒子呢？从而可以无中生有获取能量？理论上确实能让虚粒子变成真实的粒子，但并不能凭空获取能量。

For example, in the Casimir effect mentioned above, we can continuously pull one of the metal sheets back and forth, so that the two metal sheets continue to move closer and then farther away, and repeat this action. In this process, some virtual particle pairs that should have been annihilated may not be able to find their "other half" due to the constant movement of the metal sheet, and thus become real particles.

比如说，上面所说的卡西米尔效应，我们可以来来回回地不断拉扯其中一片金属片，让两张金属片不断靠近然后远离，一直重复这个动作，在和这个过程中，某些本应该湮灭的虚粒子对，可能会因为金属片的不断移动找不到自己的“另一半”，从而变成真实的粒子。

This process cannot come out of nothing, because we also put in energy!

这个过程并不能无中生有，因为我们也付出了能量！

Similar to this is the "Hawking radiation" proposed by Hawking. Virtual particle pairs will be derived near the event horizon of a black hole. Normally, they will annihilate instantly, but under certain accidental circumstances, a virtual particle will be swallowed by the black hole, and the other virtual particle will escape into space and become a real particle. This process is manifested as the evaporation of the black hole. The black hole continues to evaporate in this way and eventually disappears!

类似的还有霍金提出的“霍金辐射”，黑洞事件视界附近会衍生出虚粒子对，通常情况下它们会瞬间湮灭，但某个偶然情况，某个虚粒子被黑洞吞噬，另一个虚粒子就会逃逸到太空成为真实的粒子，这个过程表现出来的就是黑洞的蒸发，黑洞就是通过这种方式不断蒸发，最终消失的！