Scientists have demonstrated an experiment that your physics lecturer may have told you was completely impossible - they created matter at a temperature below absolute zero. And the world beyond absolute zero is a completely unusual world.
Scientists have demonstrated an experiment that your physics lecturer may have told you was completely impossible - they created matter at a temperature below absolute zero. And the world beyond absolute zero is a completely unusual world.
Atoms floating upwards completely ignore gravity. As part of the phenomenon that theoretical physicists believe mimics the state of "dark energy", the atoms are even stable under conditions that would normally collapse in on themselves. It is as if gravity itself has been canceled and energy systems that would normally lead to instability suddenly become stable and possible. In short - we have reached the twilight zone of particle physics.
Professor Wolfgang Ketterle from the Massachusetts Institute of Technology (MIT) is a pioneering researcher in the field of temperatures below absolute zero. In one of his statements, he said: "With temperatures below absolute zero, it's as if you can put a pyramid on its head and not worry about it collapsing."
Together with Professor Ulrich Schneider from the Ludwig Maximilian University in Munich, Germany, the research team demonstrated for the first time ever a case where a substance found at a temperature below absolute zero breaks the laws of physics we know. The research began with the creation of an unusual quantum gas using laser beams and magnets. The gas, which is composed of potassium atoms, organizes itself in the configuration of a crystalline structure. A radical change in the magnetic fields applied to the material results in the transfer of atoms from the lowest possible energy level to the highest possible energy level.
Under normal conditions, the stabilizing repulsive force of the original modes would be replaced by a powerful attraction that would cause the system to collapse in on itself. However, instead, thanks to the laser beams trapping the atoms, the structure remains stable in the new excited energy state. Professor Schneider explains: "This sudden change (in the magnetic fields) moves the atoms from their most stable, low energy state to the highest possible energy state before these atoms have time to react. It is as if you are walking in a valley, and then immediately find yourself on the top of the mountain." The result is a gas that, within the framework of the official definition of the Kelvin temperature scale, is at a temperature several billionths below Kelvin's absolute zero (0 K).
At the same time, let's not get confused - the system that is at a temperature below absolute zero is not cold. In fact, it is very, very hot, even hotter than any other positive temperature on the Kelvin scale. In systems of colder positive temperatures, the number of particles in low-energy states exceeds the number of particles in high-energy states, a situation that gives rise to the official definition of temperature in the world of quantum mechanics. In a common way, the entropy (a physical measure of the level of disorder of a system consisting of many particles) on average, causes the atoms to be in the lowest energy states. Lord Calvin's temperature scale is based on probability, and not necessarily on the degree of heat. However, in special systems of quantum mechanics, entropy actually decreases as the energy of the system (and its heat) increases, leading to a negative quantum temperature. In other words, in order to understand this miraculous breakthrough, we must abandon our traditional understandings that negative is cold and positive is heat, and start thinking in quantum terms.
Can such a situation explain the faster than expected expansion of the universe (a phenomenon that cosmologists attribute to what is known as "dark energy" which itself is an unexplained mechanism)? Professor Schneider claims that this possibility is worth exploring. He adds and says: "It is interesting that this phenomenon exists both in the entire universe and in the laboratory. This is something that cosmologists should examine in more detail." Materials that exist at temperatures below absolute zero could be useful both in the fields of theoretical particle physics and for quantum computing. However, much further work is still required to understand this strange new deviation in the laws of physics. The study was published in the prestigious scientific journal Science.
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So the laws of physics may not be correct at all
They explained a lot of things in the mystery arbitrariness dark matter maybe all the theories are just wrong
Many times throughout history the science that was XNUMX% sure of its correctness was wrong and one theory was replaced by another
Maybe it's time to change another theory
deer
If the vacuum temperature is 2.73k, then what will be the temperature of a body moving with relative velocity relative to radiation?
Example: a spaceship at a distance of 1000 km from the Earth and another spaceship passing by at a speed close to c. The temperature of A is 2.73k. What is the temperature of B?
If the answer is that it is much higher than 2.73k, then the question arises about the equivalence of inertial systems, and also a puzzlement about well-known experiments with relative velocities such as the muon experiment, and also about particles in accelerators: after all, there is a preferred inertial system - that of the cosmic background radiation - a relatively moving body Elia heats up as it approaches the speed of light. What is the wonder then that it is not possible to exceed the speed of light, and this has nothing to do with relativity?
If, on the other hand, the temperature of the two spacecraft in the example is the same and equal to that of the background radiation, new problems of matching the existing models emerge.
Israel,
In order for a thermometer to be able to measure the temperature, there needs to be a mechanism that can bring it to thermal equilibrium - within a gas environment, it reaches equilibrium mainly by transferring kinetic energy to the gas particles, so the question arose of what would happen in a vacuum. The answer is of course that even in a vacuum a thermometer will manage to reach equilibrium with its environment since it will be able to "get rid" of excess energy through black body radiation (of course, if it is cold from its environment it will be able to heat up by absorbing photons).
Regarding the temp he will see:
This temperature will surely be equal to or higher than the temperature of the cosmic background radiation - this is because it will be able to achieve this temperature through equilibrium with this radiation that exists everywhere in the universe, in addition, there can be additional radiation that arises from local causes (let's say a nearby star).
It is indeed not clear what a vacuum thermometer will show - but it seems to me that if it is visible to the sun, then after a few minutes it will show a fairly high temperature, especially if the material it is made of is a dark material. That's why the shadow.
In the answers I received in various physics forums, the prevailing claim is that a vacuum thermometer will show the radiation temperature - 2.73K. A physicist also claimed that a spaceship approaching the speed of light would evaporate due to the radiation, which raises the question of the equivalence of inertial systems: why shouldn't we evaporate? We are moving relative to that spaceship at the same speed as it is moving relative to us, aren't we? It is true that we are almost stationary relative to radiation, but if at relative velocities the temperature of objects increases steeply, then what is the wonder that it is not possible to exceed the speed of light? After all, all the acceleration energy is wasted on heating the object. Note that this has nothing to do with relationships. Einstein didn't even know about the cosmic background radiation in 1905.
Anyway, thanks for the answers. No, I'm not planning any space travel, but I'm building all kinds of nice facilities to test all kinds of ideas, almost certainly without any foundation. The answers I get from you and others help me in planning those facilities.
Israel
There is no connection to a shaded area. A thermometer does not measure the heat of radiation, the temperature is deduced from the spectrum analysis of the radiation and not from a thermometer so there is no connection to a shaded area. Your question about what a thermometer looks like depends on what is found
In space, it is not clear to me what a thermometer will show in a vacuum, but if we assume that the particle density is high enough
affect a thermometer So the question is whether the particles are in equilibrium with the cosmic radiation or in equilibrium with the centers of heat near them ie stars.
As for the second question, the holster will heat up, but in my opinion, the radiation will not be the important source of heat, but the range
The interspace (by the way are you planning to fly somewhere?) . In addition, it is not clear to me whether there is a connection between the speed of the spaceship and its heating, that is, it is not clear to me that the faster the spaceship flies, the more it heats up, the heating depends on how momentum is transferred from the photons to the material of which the spaceship is composed and this depends on the atomic denominator of the materials that make up the spaceship.
Ehud, thank you. Just 2 more tiny questions - and you're released.
1. What will a simple Kelvin thermometer show in space in a shaded area? Will it be able to show a temperature lower than the cosmic background radiation temperature?
2. If a spacecraft cruises at a speed close to the speed of light relative to radiation, will it heat up? Can't we say that as far as she is concerned she is at rest and we are the ones who are moving? Do particles with mass in accelerators, which reach almost the speed of light, encounter "friction" because they move so fast relative to radiation?
Israel
Time is indeed pressing... but I will try to answer at least some of the questions... Let's start from the end, the temperature of the space is measured by radiation and not by a thermometer. When there is a heat source in thermal equilibrium that emits radiation into its environment, it is described by the formula of blackbody radiation. The temperature of the body can be estimated from its spectrum, that is, what is the intensity of the radiation at each energy. The distribution allows us to estimate the original temperature of the body (which could be measured with a thermometer). The background radiation is a measure of the temperature of the universe at the moment the photons were emitted. If the spacecraft is moving at the speed relative to the reference frame of the radiation, the radiation will undergo a doppler shift, but this will not change its distribution, therefore the temperature measured will be the same temperature
Regarding the second part, there will only be 2 temperatures in my opinion, the one that will be measured by the thermometer which is a low but positive temperature of the movement of the gas particles and the other one is the famous negative temperature that is obtained from the distribution of states. Although she is negative, she is very energetic.
Ehud, if I understood correctly, then we have here 2 temperatures for the gas composed of potassium atoms in the aforementioned experiment, or actually 3: one - the one we measured with a thermometer, and it is higher than absolute zero. The second - the temperature that is measured indirectly by measuring the occupancy of states, and is lower than that of absolute zero. The third - "It is very, very hot, even hotter than any other positive temperature on the Kelvin scale".
Confusing, isn't it?
And in the same matter: the space temperature is estimated at 2.73K. Does this mean that if we take a thermometer out of a spacecraft in an area without any direct sunlight, then this is the temperature that the thermometer will show? If not, then what will he see? What if the spaceship flies at a speed of 0.999C relative to the Earth, will the thermometer show a different, higher temperature, even though the spaceship in its frame of reference is at rest?
Sorry for the flood of questions. If you're too busy, let me know and I'll understand.
Israel
It is not a temperature in the usual sense that is measured with a thermometer, i.e. the average kinetic energy of particles, but a temperature resulting from the energy occupancy of degrees of freedom whose coupling with the environment is
very weak That is, you will not measure the temperature of the system if you approach it with a thermometer. The temperature measurement is measured indirectly by measuring the occupancy of states.
Thank you Ehud. What bothers me is the statement in the article: "The temperature of the system is actually higher than any other temperature on the Kelvin scale". Indeed, in Wikipedia, a negative temperature entry appears:
"The temperature scale from cold to hot runs:
+0 K, … , +300 K, … , +∞ K, −∞ K, … , −300 K, … , −0 K.”
When the maximum temperature is:
Current cosmological models postulate that the highest possible temperature is the Planck temperature, which has the value 1.416785(71)×10^32 kelvin.
So if I understood correctly what is written in the article:
"At the same time, let's not get confused - the system that is at a temperature below absolute zero is not cold. In fact, it is very, very hot, even hotter than any other positive temperature on the Kelvin scale."
It turns out that the same "extraordinary quantum gas" described there is at a temperature higher than 32^10 Kelvin, isn't it?
And if not, what is the temperature measured for that gas using a thermometer? Surely it has a certain and defined temperature that can also be measured, right?
Israel
The temperature in question is defined by the probability of finding the system in a certain state
When the number of possible states for the system increases with the energy of the system (the state
the usual) the temperature will always be positive, but when it is a closed system that succeeds
to excite almost all the particles to their excited state adding energy only decreases the
The number of possible states accessible to the system ie entropy decreases with increasing energy
Therefore, by definition the temperature is negative.
oak.
Your dilemma - my dilemma.
Until today I believed that the Kelvin scale is Celsius + 273, and that temperatures are measured with a thermometer. But apparently when you get close to absolute zero, quantum effects emerge. Maybe Ehud can explain, that's his field.
Israel,
Thank you for the clarification.
However, now the sentence quoted in my previous response is not understandable to me. Do you understand what it means?
I understood it like this:
The Kelvin scale is based on statistics.
Entropy is the relevant statistical measure.
A situation arose where the entropy decreased, therefore the temperature decreased.
But now it seems that either I did not understand him correctly, or that there is a missing step between the decrease in entropy, and the conclusion that the temperature can be negative.
oak.
Not necessarily. When an ice cube melts, there is no change in the temperature of the system but the entropy increases.
If I understood correctly, it means that when energy is added to a system, its entropy decreases because the energy temporarily raises the energy level in the atoms from the stable lower state to a higher state. It does not mean that we really got a temperature lower than absolute zero. If my memory serves me correctly, this is not exactly a new phenomenon and in fact almost all the mathematical formalism of the second law and of thermodynamics in general, remain unchanged even at negative temperatures.
What I don't understand is how you can talk about the temperature of the system being actually higher than any other temperature on the Kelvin scale. Ehud, could you perhaps clarify what you mean?
Thanks.
Israel,
Isn't that implied by what he writes?
"Lord Calvin's temperature scale is based on probability, and not necessarily on the degree of heat. However, in special systems of quantum mechanics, the entropy actually decreases as the energy of the system (and its heat) increases, a situation leading to a negative quantum temperature."
I am not an expert in the field, so the points are not prior knowledge that I am passing on.
In fact when I finished reading the scripture I felt that a lot of things were said in a way that I could not put together coherently. That's why I tried to exhaust the ideas that are conveyed here according to my understanding - precisely because I still feel that something is missing in my understanding.
Diogenes
The question is not stupid. The reason they haven't reached absolute zero to date is not technological
but physically. Reaching absolute zero contradicts the second law of thermodynamics,
The second law of thermodynamics can even be formulated as the impossibility of reaching zero
the absolute Other formulations of the law are: in a closed system the entropy always increases or there is no process
which only transfers heat from a cold system to a hot one
oak.
You write: "1.b) In the physical sense we connect the concept of temperature with the concept of entropy. That is, the "less ordered" the particles are, the higher the temperature, and the opposite direction is also true."
Can you elaborate or give an example?
Sorry for the ignorance and the funny question, but as far as I know, they have never been able to reach absolute zero due to the technological limitations, one of which is that to build a system that cools that much, you have to invest a lot of energy, which is expressed, among other things, in heat? (Sorry for the so uneducated explanation... any comments are welcome). And if this is indeed done, isn't this very serious news that has not been covered outside of scientific sites?
Hi Roy, sorry for the question that is not directly related to the topic, but is that your original name?
I thought Roy was always registered with 'A', am I wrong?
Thanks.
Roy, thanks. We will refer to the source and the idea presented in it.
I'm not sure I understand exactly what is being said here.
I will try to separate the points that I think exist in the article, and ask for corrections/clarifications:
1.a) In the "popular" sense, we associate adding energy/heat to a system with an increase in its temperature.
1.b) In the physical sense we connect the concept of temperature with the concept of entropy. That is, the more "less ordered" the particles are, the higher the temperature, and the opposite direction is also true.
1.c) Until now it was customary to look at the two previous definitions as not contradicting each other (ie more heat = higher entropy).
1.d) A new experiment showed that in certain situations, when heat/energy is added - the entropy actually decreases. Something that surprised the scientists, when the surprise can generally be described by the fact that we now know that there are situations where the definitions in (1.a) and (1.b) do not match each other.
2.a) Usually, when you add energy to an electron that is in a stable state (in the lowest energy state in the atom), it "jumps" to the new state, and "immediately" returns to the stable state, when it releases the energy to the system.
2.b) From a thermodynamic point of view, this "instant" had no meaning, and the system "balanced" with the new energy, in a way that is reflected in the increase of entropy - as expected.
2.c) In a new experiment, they managed to force the electron to stay in the new state after adding the energy, so it did not return to the previous state.
2.d) Contrary to the classical situation, the electron did not return "immediately", and a situation was created in which we added energy to the system, but because of the constraint, the energy did not "balance" - and is not reflected in its increase in entropy.
3.a) In one place it is written:
"In systems of colder positive temperatures, the number of particles in low-energy states exceeds the number of particles in high-energy states, a situation that gives rise to the official definition of temperature in the world of quantum mechanics"
3.b) Almost immediately afterwards it is written:
"In special systems of quantum mechanics, the entropy actually decreases as the energy of the system (and its heat) increases, a situation leading to a negative quantum temperature"
3.c) From (3.a) it is implied that quantum temperature is a statistical concept derived from the energy states of the electrons. A definition that in itself should always be "non-negative". Which leads to the question of what is meant by negative quantum temperature?
3.c.1) Is the reference here to the way in which the quantum state is reflected in the effect on the temperature index of the entire system? That is, "negative effective temperature" of the quantum state - like a way to describe "capsule heat"?
Thanks.
exciting!
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/neg_temperature.html
I did not understand, if absolute zero means that the atoms do not move and below absolute zero they move again, what is the explanation between below zero and above zero?