From the beginning of my kindergarten class, I heard the teacher say: Children, the atoms are very small, you can't see it directly, but I thought that the clear soup provided by the teacher for them did not have meat balls, and I couldn't see the meat to find a reason
Where are the meatballs
But later, as we entered elementary school, junior high school, high school, and college, I understood more and more what our teacher said, and the atoms were indeed so small that it was impossible for humans to see them with the naked eye or even an optical microscope. However, one day I found a photo, the middle of this photo is actually an atom, note that this is not a picture under the electron microscope, he is directly with the camera to take a photo of the naked eye, the atom can actually be seen with the naked eye? Is it because my eyes are too fluttery, or the microscope can't lift the knife?
Atoms seen with the naked eye
<h1 class="pgc-h-arrow-right" Data-track="4" What are > atoms and can they be eaten? </h1>
Atoms can be eaten, but definitely not the meat balls you eat, but a tiny structure that makes up matter, microscopically speaking, most of the matter in our universe is composed of atoms (neutron stars, black holes, etc. are not, horizontal bar players please go out and turn right, thank you), But its diameter size is generally only 0.1 nanometers, this number is 1 million times smaller than the diameter of the hair, if you make an analogy, there are more than 45 trillion atoms in a drop of water, if the world's 7 billion people to count, a hundred a minute, non-stop counting also need a full 12,000 years to be able to count, you can imagine the meaning behind this huge number, the atom is too small, and for many myopic and presbyopia students, sometimes even a hair can not see clearly, why can you now see atoms that are a million times thinner than hair? This starts with the tools of human understanding of the microscopic world.
10 meters away from the hermaphrodite, 30 meters outside the animal is not divided
<h1 class="pgc-h-arrow-right" data-track="36" > lift your hijab and let me see your face</h1>
Lift the hijab and draw the lottery
In the long-term development of modern human science, because the atom is too small, what it looks like and how it exists has always been a huge mystery, making scientists itch to the point of not being able to do it, just as in ancient times and the lady with the red hijab that had never been seen before became a parent, and then waited to lift the red hijab to win the lottery. We can see this from the name of the atom, in Chinese, the original can be understood as primitive, that is, the most basic meaning, in fact, human beings have long believed that the atom is the smallest particle in the world, it can not continue to divide. Until the appearance of Thomson.
Thomson discovers electrons
In 1987, Thomson did a famous experiment, that is, to add a huge voltage at both ends of the vacuum tube, it turned out that there were rays emitted from the cathode, and deflected through the magnetic field, proving that it was negatively charged, so Thomson found electrons, thus proposing that atoms can actually be divided, and foodie soup also used its own food to name the structure of atoms: the jujube cake model, that is, the atoms are like the jujube in the jujube cake, the electrons are embedded in the atoms, but the Thomson who proposed this model has not finished laughing. Its student Rutherford directly shouted: Teacher, you are wrong, I am right, frightened Thomson did not come up, almost forked.
Date cake
Rutherford bombarded the thin gold leaf with helium ions, and found that most of the helium had passed through, and only a few deviations from the direction were even bounced back, so Rutherford said that the electrons were bounced back because of the positive charge, but now most of them passed through, and very few parts came back, which showed that the positive charge inside the atom was concentrated in a very small area, and the other places were empty, so he proposed the nuclear structure model that we are familiar with now. Only then did humanity realize the internal structure of the atom
The nuclear structure of the atom
But the question is whether these structures are deduced through experimental side reasoning, or are they true? If you can see it with your eyes, you can, so the microscope comes on
<h1 class="pgc-h-arrow-right" data-track="37" > saw the opening ceremony of the Atomic Olympics officially begin</h1>
Opening entrance
Hello audience, here is to see the opening ceremony of the Atomic Olympic Games, the first appearance is the optical microscope team, yes, is from the kindergarten to play, look at the cell of the thing, but the problem is, our kindergarten small class with the optical microscope can generally only be magnified hundreds of times, even regardless of the cost of the next door class only the national key laboratory inside the optical microscope is only more than 1000 times the magnification effect, with this thing, you can see the cells and bacteria, but even the virus can not see, Not to mention the atoms, Phalanx 1 has not yet entered the street!
The most common light microscope
The second appearance of the phalanx is the electron microscope, which brings two masters, TEM (transmitted electron microscopy) and STEM (scanning transmitted electron microscopy) Unfortunately, the TEM (transmitted electron microscopy) player working mode is similar to the optical microcrystalline, but it is changed from visible light wave to electronic matter wave, so in the face of opponents of this level of atoms, there is still no good way, TEM players pounce on the street!
TEM (Transmitted Electron Microscopy)
The last player is stem, and the strength of this player is not at all on the same level as the previous ones, because from its starting posture we can see that it is already a lot ahead of the opponent, and its atoms have actually used the magical quantum mechanics! That's right, the quantum mechanics of quantum mechanics.
Indecisive, quantum mechanics
And the specific principle is the legendary wall piercing, no, is the legendary tunnel effect, in simple terms, the insulator is equivalent to a wall, when the electron is going to pass will be blocked, but the magic of quantum mechanics is that if it is the macroscopic world, no matter how thin the wall is, unless you directly destroy it, then you can't get over, but in quantum mechanics, when the wall is very thin, the electron can magically pass through the insulator This wall, appearing on the other side of the wall, as if opening a tunnel on the wall, So it's called the tunneling effect.
Tunneling effect
And the scanning tunneling microscope is to use such a small probe close to the atomic level to continuously approach the sample we want to see, and then we add voltage in the middle of them, then the air in the middle segment becomes a wall, but the electron will magically jump over the air wall to reach the sample, the movement of the electron will produce a current, and the size of the current is related to the distance between the probe and the sample, we can see through the current whether there are atoms under the probe, where the atomic boundary is, and how big it is. This thing can clearly and accurately find the size and mass of atoms, which is simply awesome.
Schematic
<h1 class="pgc-h-arrow-right" data-track="45" > minesweeping is not OK, what if it explodes? </h1>
minesweeper
However, through the explanation process just now, we also found that we still have not really seen atoms, which is the use of electronic tunneling effect to show the side, which is like some creatures holding a mine detector to search for mines, when encountering a place with mines underground, it will ring, and by moving the detector can also find the size range of the mine, make a mark.
After that, he could clearly know where there were mines, how big each mine was, and what pattern they were arranged, but he did not see the mines underneath.
You can see the pattern of the mine arrangement
Even the scanning tunnel telescope that can be regarded as the most advanced microscope can not directly see the atoms, so why can this picture be taken with an ordinary camera and see the atoms with the naked eye?
Scanning tunneling microscope
<h1 class="pgc-h-arrow-right" data-track="52" > the power of time-lapse shooting technology</h1>
Night mode
The image, taken by quantum physicist David Naderlinger of the University of Oxford, is known as "a single atom in an ion trap." The point in the middle is a strontium atom, which is used because it has 38 protons and is relatively larger in diameter and easy to observe.
Devices on both sides
Then what you see on both sides are two metal electrodes two millimeters apart, the whole device is in a vacuum environment, the powerful electric field emitted by the two electrodes makes this strontium atom subjected, and at the same time, the laser light shot from all directions is added, suspending it in a fixed position and basically remaining motionless. Then the blue laser shines on the top of this atom, and its frequency is just the same as the strontium ion itself, so it is excited with light, and this light magnifies the diameter of the atom many times, just as we look at the bulb on a rainy day, and the large halo around it makes the bulb seem to become innumerable times larger.
Street lights make the lights bigger
Of course, even so, the naked eye can not see, because the light is too weak, so this photo uses time-lapse shooting technology, similar to the operation of the night mode of everyone using the mobile phone, so that the light accumulates a little bit, and finally reaches the point where it can be clearly visible on the photo, although the use of various means, but there is no doubt that this is indeed a direct photo to an atom, the matter of the microscopic world suddenly jumped to the macroscopic world, making people feel a shock, but also because of this, The photo has already won the grand prize in the Best Science Photo and Imaging Competition organised by the UK's Council for Engineering and Physical Sciences Research (EPSRC) in 2018.
Scan a picture taken by a tunneling microscope
What do you think? I am a teacher Li Jiangping who loves popular science, more wonderful, can you pay attention to one?