"May the force be with you", this may be one of the most out-of-the-circle movie lines. The word "Force" is "force" in English. Therefore, you can understand the Force as any form of energy or power, because the concept of the Force also contains philosophical, religious, ethical and other cultural connotations, so we will not discuss its specific form here, this article we mainly focus on whether the "lightsaber" can be realized.
A lightsaber is not a laser sword. The original text of the lightsaber is lightsaber, not laser. Although Chinese often translates to laser sword, it is more appropriate to call it a lightsaber, and it is not very appropriate to make a lightsaber with a laser.
The principle of laser light is "light amplification by stimulated radiation". It means that in the atoms that make up matter, there are different numbers of electrons, and they are at different energy levels, some of which are high and some are low. When an electron at a higher energy level is excited by an external photon, it jumps back from the higher energy level back to the lower energy level, and then emits light with an energy difference between the two energy levels. When the light radiated is exactly the same wavelength and direction as the light that excites it, we can get a collimated laser beam.
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
Because of the high energy of the laser, it can indeed be used to cut objects, which led to the development of laser cutters and laser weapons. One problem, however, is that the lasers that can cut objects are so large that they are difficult to hold in their hands. The more important question is that the light doesn't stop. Lightsabers have lengths, and in order to make lightsabers, we need to devise a way to make the radiation range of these photons around 1.5 meters, and then magically stop there. This is completely beyond the existing physical understanding, just like the light emitted by your flashlight must be infinitely extended. Another issue is the concept of a lightsaber as a physical rod or sword, which has a sound when it collides with each other. But if you turn on the two flashlights and cross the beams, it won't "buzz". This is because photons do not have a mass at rest, that is, the laser beam has no mass, so two lasers cannot "collide" in a mechanical sense.
So can you make a lightsaber that is closer to what the movie describes? The answer is yes. In fact, the official answer has been given - plasma. Plasma is a state of high-energy matter composed of electrons and ions with a temperature of about 5,000 to 10,000 °C. Fire, lightning, gas discharges from fluorescent lamps, and the solar wind that triggers the aurora are all plasma. Because the plasma has an ultra-high temperature, it can also cut objects, and the electrons and ions in it have mass, so the effect of collision can be realized, and the plasma beam is not a light beam, it can be limited in a certain range without infinite extension. In fact, the tech nerds have already made a finished product that is close to a lightsaber, and a team named Hacksmith has used strontium plasma (4500°C) to create what may be the most similar to the lightsaber at present, and you can see their video at station b. Different colors of the lightsaber can also be achieved through the flame color reaction.
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
If you think this sounds sci-fi, then I'm sorry, but changing the name may make you understand it instantly, but it also shatters the illusion: the "lightsaber" here ≈ the large airbrush.
Bibliography:
The "Laser Sword" in Star Wars? You Misunderstood!, Student Branch of QSA Institute of Physics, Institute of Physics, Chinese Academy of Sciences
Expert Answer: Is the lightsaber in Star Wars theoretically possible?
by opzk
Q.E.D.
Q2
by Normal Distribution.
Answer:
For example, everyone uses a spoon to send soup to drink, replace the soup with wind, and the concave surface of the spoon to supply air, which can be compared to a fan blowing. The fan blade is similar to the spoon, the concave surface is the air outlet, and the convex surface is the air supply outlet, so you can simply judge the high-pressure area and low-pressure area of the fan, as shown in the figure below.
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
When the blades rotate, they will push the gas in the air to move in a uniform direction (concave side), so that the blade area is a low-pressure area, and under this air pressure difference, the air on the convex surface of the fan will continue to flow to the low-pressure area, thus generating airflow.
On the concave side of the fan, the main role is to rotate the blades to guide the air to carry out centrifugal movement, so as to realize the acceleration and steering of the air.
To sum up, the principle of wind generation is the same as that of fans and fans, and the human fan is similar to a single blade swinging to generate wind.
by Lan Duoduo
Q.E.D.
Q3
by 至人 (无己)
Answer:
The principle of bonding is actually very complex, and the basic principles include mechanical theory, adsorption theory, diffusion theory, electrostatic theory, etc. For most glue bonding principles, the adhesive force is mainly due to the interaction between molecules. When the "glue molecules" fully moisten the surface of the adhered object, have good contact with it, and the distance between the molecules is small to a certain extent, the two form an interaction between the molecules, in which water plays a great role in the infiltration of the "glue molecules". The moisture in the glue then evaporates and the adhesive object is bonded. This adsorption is not only physical, but also sometimes chemical, and its adsorption is derived from chemical bonds, and it is these adsorption forces that bind the two objects together.
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
Resources:
Why glue sticks to things
by Sid
Q.E.D.
Q4
By Not all milk is called Trensu
Answer:
In fact, whether the milk is easy to pour out has nothing to do with whether it is inserted into a straw, but whether or not air enters. As shown in Figure A, insert the straw into a sealed milk bottle, assuming that the connection between the bottle mouth and the straw is well sealed and almost no air flows into the bottle, and you will find that the milk basically cannot flow out. Conversely, if the seal between the mouth and the straw is poor, air can flow into the bottle, and milk will flow out of the bottle mouth and the straw, as shown in Figure B. This is due to the fact that after the bottle is turned upside down, the pressure above the liquid level is less than the outside atmospheric pressure, and at this time, the gravity of the milk itself + the pressure of the gas inside the bottle = the outside atmospheric pressure, so the milk will not flow out. If air enters the bottle, the milk will flow out due to its own gravity. Similarly, if the straw is pulled out, the milk will not flow out even if the hole in the mouth of the bottle is small, and the milk will only flow out if the hole is large enough for air to enter the bottle.
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
by Sid
Q.E.D.
Q5
by 匿名
Answer:
Why crabs go sideways has always been an age-old question, and the relationship between crabs and geomagnetic fields has also been widely circulated on the Internet. According to some theories [1], crabs rely on the geomagnetic field to determine their direction. In the long years since the formation of the Earth, there have been many inversions of the geomagnetic north and south poles. The crab is an ancient migratory animal that has small directional magnets in its inner ear and is very sensitive to geomagnetism. Due to the inversion of the geomagnetic field, the small magnets in the crab's body lose their original orientation. In order to survive the reversal of the geomagnetic field, the crab adopts a sideways approach.
However, in the existing studies, there is no evidence to support the claim that crabs use geomagnetic fields to navigate. Most of the known crab species do not have the ability to navigate magnetic fields. Instead, they usually find their way home based on cues such as a reference in the sky, the inclination of the sand, waves, etc. In addition, crabs do not have the so-called "inner ear" structure, their hearing organs are distributed on the legs. Crabs have a number of special sensory organs distributed on their legs, which can receive sounds from the air and high-frequency ground vibrations. As a result, crab legs are very sensitive to perceiving their environment [2].
The rampant movement of crabs is related to their body structure and living environment. Each foot of the crab is composed of multiple segments, and the joints can only move up and down, and cannot turn outward. This structure dictates that the crab can walk forward slowly, but with far less stride, speed, and efficiency than walking sideways. The width of the crab's body is larger than that of the head and tail, and the whole body is in a wide, flat shape, which helps to enter the narrow burrow with low energy consumption and the fastest speed to avoid the attack of predators. Therefore, crabs usually choose to walk sideways [2].
Overall, there is currently no evidence to support the use of geomagnetic fields in crabs to navigate. Beware of the strange talk of "indecision, geomagnetic explosion/geomagnetic field" (manual dog head). The crab is more due to its body structure and adaptability to the living environment, and its rampaging way allows it to move more efficiently in confined environments.
Resources:
Interesting science| Why do crabs walk sideways?
Why do crabs walk sideways?
by Fish Not Me
Q.E.D.
Q6
by 高中物理洪老师的学生
Answer:
First of all, we need to make it clear that energy will not be generated for no reason, nor will it disappear out of thin air, after the interference of two beams of light, the energy must be conserved, after the interference of two beams of light, there will be light and dark stripes, the bright stripes are the position of the enhanced interference, and the dark stripes are the interference cancellations. Among them, only when the intensity of the two beams of light is the same, the light intensity of the position where the interference cancellation occurs is 0.
Interference conditions: the same frequency, constant phase difference, vibration in a straight line.
There are two beams of light with the same frequency and different phases:
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
At this point, you can clearly see that after the interference of two beams of light, if the light intensity of the two beams of light is the same, after the interference is eliminated, the light intensity of the corresponding position is 0, and correspondingly, the light intensity of the position of the interference enhancement reaches the maximum value.
by Lan Duoduo
Q.E.D.
Q7
by Life Finder
Answer:
I haven't seen a green rainstorm day, so it would be nice if I could provide a picture to give me a long insight (bushi). Severe convective weather does show some unusual skies, but the unusual skies are nothing more than ordinary scattering. Of course, scattering has several lofty-sounding names, and hopefully that doesn't bother you.
The scattering of light is a phenomenon in which a portion of light light passes through an inhomogeneous medium that deviates from its original direction of propagation (if the light passes through a homogeneous medium, we do not call it scattering, we call it reflection and refraction). The scattering family is generally divided into elastic scattering and inelastic scattering by whether energy loss occurs or not. The main members of the elastic scattering family are Rayleigh scattering and Mie scattering, while the main members of the inelastic scattering family are Raman scattering and Brillouin scattering. The situation we are discussing today has little to do with inelastic scattering, so this part is left to the reader to consult for himself (in fact, the author is too lazy to write about it).
Rayleigh scattering is characterized by the intensity of scattering inversely proportional to the 4th power of the wavelength, which occurs when the particle size is much smaller than the wavelength of light. This means that the shorter the wavelength of light, the more it is scattered. The sky is blue because the wavelength of blue-violet light is short, and it can only be received by the naked eye after being scattered, otherwise it will be as dark as in the universe; if the blue light is scattered too much and consumed, for example, the sunrise and sunset sun inclination angle is relatively large, the light path is long, and the blue light is scattered too much, and the sky is mainly red.
Another type of scattering that is more important in severe convective weather is Mie scattering. When the size and wavelength of particles in the optical path are comparable, Mie scattering mainly occurs. The intensity of Mie scattering is inversely proportional to the second power of the wavelength of light, and the fluctuation of scattering intensity with wavelength becomes weaker as the particle increases. Because the particle size of clouds is similar to the infrared wavelength, this scattering pattern occurs mainly when there are large particles in the air, such as dust, water droplets, and particles from pollutants. There are a large number of small water droplets and Xiaoice crystals in the clouds under strong convective weather, which can cause a large amount of Rayleigh scattering and Mie scattering. These particles are larger than the nitrogen molecules scattered under a clear blue sky, and the wavelength scattered by a certain coincidence will be exactly blue-green.
In addition, this phenomenon is somewhat similar to the article we forwarded two days ago, the blood is actually green under the deep sea, if you are interested, you can refer to it.
Bibliography:
Lecture on Fundamentals of Optics - Issue 8: Light Scattering, Fang Zaijin, Jinan University
Zhengzhou, Henan Province was shocked by the "green sky", what is the reason for this phenomenon?
by opzk
Q.E.D.
Q8
by Please, the question must be drawn
Answer:
The process of fertilization is the process by which the sperm overcomes all odds to combine with the egg and give birth to a new life.
After mating, about 300 million sperm enter the vagina, of which millions of sperm will escape the vagina or die in the acidic environment, and the remaining sperm will survive under the protection of weakly alkaline semen.
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
Sperm pass through the cervix into the uterus. The cervix is usually closed and only opens during ovulation (and a large number of poor quality and low motility sperm are eliminated later in the process due to their short survival time). The rest passes through the cervix and swims towards the uterus, where millions of sperm sink into the folds of the cervix (stroke).
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
Arriving at the uterus, it swims to the egg with the help of uterine muscle contraction, and the sperm will be attacked by the immune cells in the woman's body, and some sperm will die (tens of thousands).
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
After that, half of the sperm swims to the empty fallopian tube, and the other half swims to the egg with it, leaving a few thousand sperm, where the tiny cilia push the egg to the uterus, and the sperm continues to move inward despite the ciliary blockage.
Chemicals in the reproductive tract cause changes in the membrane structure of the sperm head, and when the sperm reaches the egg, there are only a few dozen left, and the egg is surrounded by a layer of radial crown cells, through which the sperm touches the outer layer of the egg, the zona pellucida.
When the sperm comes into contact with the zona pellucida, it immediately binds to the receptor on it, triggering the sperm acrosome to release digestive enzymes that allow the sperm to burrow into the egg, which is a narrow space filled with fluid, that is, the outside of the egg cell
The first sperm that comes into contact with the egg cell fertilizes it, and the sperm fuses with the outer membrane of the egg within a few minutes, pushing the sperm inside the egg. After that, the egg membrane undergoes a cortical reaction to prevent other sperm from entering, and the egg simultaneously releases chemicals to isolate the sperm from the outside to form a fertilization membrane, and the zona pellucida hardens (zona pellucida reaction), further preventing the sperm that are passing through the zona pellucida and the sperm that are separating the sperm from the outside.
According to an article in the journal Cell (attached), the process of hardening of the zona pellucida is inseparable from a protein called ZP2, which hardens after a single sperm fertilizes the egg, thus blocking the entry of multiple sperm (this process is irreversible). Zona pellucida sclerosis is an overall physicochemical change associated with cleavage of the N-terminal region (NTR) of the glycoprotein ZP2, one of the four glycoproteins that make up zona pellucida (ZP1, ZP2, ZP3, and ZP4).
How do sperm beat hundreds of millions of other sperm and finally combine with the egg? No.404
Cleavage of ZP2 triggers its oligomerization (i.e., the formation of dimers or trimers or long chain molecules between individual compounds), or understood as the formation of these protein biomolecules by non-covalent bonds. Two fibrils composed of type I (ZP3) and type II (ZP1/ZP2/ZP4) are connected to each other to form a left-handed double helix, from which the NTR region of the type II subunit protrudes, including the N-terminus of the ZP2 protein. The cleavage of ZP2 oligomerizes its NTR region, which allows a large number of ZP proteins to be cross-linked, hardening the zona pellucida and thus physically blocking the entry of other spermatozoa.
Bibliography:
Shunsuke Nishio,ZP2 cleavage blocks polyspermy by modulating the architecture of the egg coat,Cell,Volume 187, Issue 6,2024,Pages 1440-1459.e24,ISSN 0092-8674
Nucleus "Bio Laboratory"
by Lan Duoduo
Q.E.D.
Q9
by 匿名
Answer:
From a thermodynamic point of view, temperature is a physical quantity that measures the internal energy of an object. According to the zeroth law of thermodynamics, when two objects are in thermal equilibrium, their temperatures are equal, and this law provides the basis for the definition of temperature. According to the third law of thermodynamics, we can define absolute zero, which is the theoretical lower limit of temperature. Absolute zero is defined as (Kelvin), which is equivalent to. At this temperature, the movement of the molecules and atoms of the substance almost ceases and the thermal energy reaches its lowest point.
Why is the minimum temperature but not the maximum in physics? This is because in thermodynamics, the definition of temperature is based on the thermal motion of matter. When the temperature of the object increases, the motion of the molecules and atoms becomes more intense and the heat energy increases. However, there is no theoretical upper limit to constrain the maximum value of the temperature. This is because the thermal motion of a substance can increase indefinitely without a definite limit.
From a cosmological point of view, there is a possible maximum temperature in the universe known as the Planck temperature. The Planck temperature is derived from the theory of quantum mechanics and gravity and has a value of about [1]. This temperature is defined based on the physical constants in the Planck system of units, which represents the temperature in the very short period of time after the Big Bang. At this temperature, if an object reaches the Planck temperature, it will emit blackbody radiation corresponding to the Planck length. If the temperature is higher, it will emit blackbody radiation at a lower wavelength than Planck's length, but we lack a theory to describe this situation.
The existence of Planck's temperature does not imply that there is a maximum temperature constraint in the universe. Planck temperature is only a theoretical temperature based on dimensional analysis and has no practical significance. In the real universe, the highest temperature we can observe is determined by the nature and interaction of matter. For example, at high temperatures, hadrons "melt" into quark soup, which is known as the Hagedorn temperature, which is about [2]. However, this is not an absolute maximum temperature, as quark matter may be able to be further heated.
In thermodynamics, the lower limit of temperature is absolute zero, because the thermal motion of matter almost ceases at this temperature. And there is no clear constraint on the upper limit of temperature, as the thermal motion of matter can increase indefinitely. In cosmology, the Planck temperature is considered the highest possible temperature, but it is only a theoretical temperature and has no practical significance.
Resources:
Planck temperature
Since the universe has a lower limit on the minimum temperature, is there an upper limit on the maximum temperature?
by Fish Not Me
Q.E.D.
Participants in this issue: Sid, opzk, Lan Duoduo, Yu Fei Me
