What temperature is absolute zero?

Science is full of zeroes. Light has zero mass. Neutrons have zero charge. A mathematical point has zero length. Those zeroes might be unfamiliar, but they follow a consistent logic. All represent the absence of a certain quality: mass, electric charge, distance.

Then there is the puzzling case of absolute zero.

We tend to think of hot and cold as relative things. A cup of hour-old tea, for example, is colder than the fire on your stove but hotter than an ice cube. Absolute zero represents the coldest possible temperature, which defies the this-versus-that pattern.

Stranger still, absolute zero isn’t even zero on the temperature scales used by nonscientists. It’s minus 273.15 degrees on the Celsius scale, or minus 459.67 degrees Fahrenheit, or zero degrees Kelvin.

How can there be a lowest temperature?

The key to decoding absolute zero is understanding what temperature is. It’s simply a measure of how fast the atoms or molecules within a substance are moving — or, to be more precise, the average kinetic energy of those particles.

Think of it as a game of atomic dodgeball. When the ball hits you, you feel its energy. Trillions and trillions of those dodgeball hits, happening on an invisibly small scale, are what we perceive as temperature.

Fast-moving atoms hit hard, which we feel as a high temperature. When a hot object touches a cold object, the faster, hotter atoms impart some of their velocity to the slower, colder ones. The hot object cools. The cool object grows warmer.

Now the zero in absolute zero makes sense: Absolute zero is the temperature at which the particles in a substance are essentially motionless. There’s no way to slow them down further, so there can be no lower temperature.

Does everything stop moving at absolute zero? Not quite. Atoms aren’t entirely still; they wobble as a result of effects related to quantum physics. And, of course, the activity within each atom continues no matter how cold it gets. Electrons keep moving, as do protons and neutrons.

Who discovered absolute zero?

Guillaume Amontons, a French inventor who lost his hearing in childhood and never went to college, figured out the basic concept in 1702. His experiments showed that air pressure is proportional to temperature, and he deduced that there was a minimum temperature at which pressure would drop to nothing. He even made an estimate of that temperature, minus 240 degrees C — remarkably close to the actual value.

In 1848, the Scottish-Irish physicist William Thomson, better known as Lord Kelvin, extended Amontons’ work, developing what he called an “absolute” temperature scale that would apply to all substances. He set absolute zero as 0 on his scale, getting rid of the unwieldy negative numbers. Physicists now rely on the Kelvin (K) scale for temperature measurements.

Where is the coldest place in the universe?

The energy left over from the Big Bang warms the whole universe, keeping it well above absolute zero. The average temperature of space is 2.74 Kelvin, or minus 454.7 degrees F.

Surprisingly, some celestial objects are colder than empty space. An expanding cloud of gas called the Boomerang Nebula behaves like an interstellar refrigerator. With a temperature of about 1 K, it’s the coldest naturally occurring location in the cosmos.

But humans have gone colder than that right here on Earth. In 2003, researchers at MIT used laser beams to slow sodium atoms, cooling them to one-half of a billionth of a degree above absolute zero. That’s still the world record.

The coldest place beyond Earth is artificial, too. Last summer, astronauts activated an experiment called the Cold Atom Lab aboard the International Space Station. The lab has attained temperatures 30 million times lower than empty space. “I’ve been working on this idea, off and on, for over 20 years,” says Robert Thompson of NASA’s Jet Propulsion Lab, one of the researchers who devised the experiment. “It feels incredible to witness it up and operating.”

What happens when matter gets that cold?

If Thompson sounds excited, it’s because ultra-cold atoms behave in fascinating and potentially useful ways. For one thing, they lose their individual identities, fusing to form a bizarre state of matter called a Bose-Einstein condensate.

“We have folks aiming to use condensates to do practical things like improving satellite navigation, while others are trying to test fundamental theories of physics or to simulate the physics of the early universe,” Thompson says.

Close to absolute zero, it’s also possible to manipulate chemical reactions in ways that are impossible under other conditions.

Last spring, Harvard chemist Kang-Kuen Ni assembled a molecule directly from two low-temperature, slow-moving atoms, making it the smallest chemistry experiment ever conducted. Under such conditions, the subtle effects of quantum physics become plain to see. “At these ultracold temperatures, we can actually observe the wave nature of atoms and molecules,” she says.

Next, Ni hopes to explore undiscovered rules of chemistry and to design new molecules. Other likely applications of absolute-zero experiments include precision sensors and clocks — maybe even the ultra-powerful quantum computers that tech companies keep promising.

In the field of ultra-cold research, you might say the bottom is the limit.

See more here: nbcnews.com

Header image: expii

Editor’s note: Particle accelerators, like the Large Hadron Collider at Cern in Geneva, cool the beam pipes down to -271C, so all electrical resistance is lost.

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Comments (11)

  • Avatar

    Allan Shelton

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    Quote… “But humans have gone colder than that right here on Earth. In 2003, researchers at MIT used laser beams to slow sodium atoms, cooling them to one-half of a billionth of a degree above absolute zero. That’s still the world record.”

    Question… How do you measure a half a billionth of a degree K???

    Reply

    • Avatar

      JaKo

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      A simple question requires simple answer:
      One doesn’t measure anything in “modern physics” — everything is “evaluated/approximated” by crooked math, aka special branch of statistics.
      BTW, there is no “Degree” of a Kelvin, as there is no need to extrapolate below zero or above another point fixed by its definition; this absolute is absolute; well, despite the fact that the size of the 1K step is equal to 1 deg C (hundred parts between freezing and boiling points of H2O at standard pressure;-)
      Cheers, JaKo

      Reply

  • Avatar

    Jerry Krause

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    Hi Allan and PSI Readers,

    You ask: “How do you measure a half a billionth of a degree K???”

    Answer: YOU DON’T!!!

    As soon as one reads something like this; one should stop reading the nonsense that is being written.

    How do I know this??? I have done experiments at pumped Helium temperatures, maybe below one kelvin (I forget the precise details). I have done experiments at above 800 Kelvin (again I forget the precise details). I have studied NOAA’s atmospheric temperature measurements during a hour and read that the difference between the maximum temperature and minimum temperature is often more than a degree Kelvin (Celsius). And many SCIENTIFIC EQUATIONS require the Kevin (K) temperature (approximately C + 273)

    Hence, I know that when people take any temperature measurements and claim a precision of more than a tenth of a Kelvin degree that their claimed temperatures are pretty much meaningless!!!

    THERE IS ALWAYS A PRACTICAL LIMIT ON HOW PRECISELY ANY ACTUAL MEASUREMENT CAN BE MADE!!!

    Have a good day, Jerry

    Reply

  • Avatar

    Joseph Olson

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    Kirchoff Laws of Spectroscopy, 1860
    1 Solid, liquid and dense gas (Sun) excited to emit light will radiate at all wavelengths and thus produce a continuous spectrum
    2 Low density games, exciting to emit light will do so at specific wavelengths and produce an emissions spectrum (Earth’s atmosphere)
    3 Light composing a continuous spectrum, which passes through a cool, low density gas, the result will be an absorption spectrum (Earth’s atmosphere)
    It is impossible to teach Radiation Physics to Warmists or Lukewarmists

    Reply

    • Avatar

      Jerry Krause

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      Hi PSI Readers and Joseph,

      Do you see a potential problem when Joseph begins: “Kirchoff Laws of Spectroscopy, 1860.”???

      I do!!! For in 1860 it had become generally accepted that matter was composed of tiny ATOMS for less than 60 years. And we certainly know there have been many instruments invented and experiments done since 1860.

      Have a good day, Jerry

      Reply

    • Avatar

      Jerry Krause

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      Hi Joseph and PSI Readers,

      Somewhere and sometime I have asked you about the possible phenomenon of RADIATION SCATTERING. Todate I have not read your answer. Now, I direct your attention to Chapter 32, Volume 1 of Richard Feynman’s ‘The Feynman Lectures On Physics’ (1963). And specifically to section 32-6 ‘Scattering of light’.

      Have a good day, Jerry

      Reply

      • Avatar

        Joseph Olson

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        Rayleigh Scattering occurs in the upper atmosphere by Ozone, giving the blue sky glow. Photons moving at the speed of light might be slightly deflected by gas molecules, but the diatomic N2 and O2, nor three atom H2O or CO2 molecules could NEVER “reverse” the trajectory of EMR at any frequency. Any absorption is followed immediately by an emission of longer wavelength, lower energy photon, COOLING the Earth. (repeated for first time readers)

        Reply

      • Avatar

        Jerry Krause

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        Hi Joseph,

        Go the link (https://principia-scientific.com/the-corvallis-or-uscrn-site-a-natural-laboratory-part-three/) and explain the colors seen in photo 2. Specifically the intense blue which I know is being caused by a smoke band due to a wildfire more than a hundred miles to the East.

        I have asked you to read what Richard Feynman wrote about light scattering but it seems you have not because you have not yet specifically referred to it. His lectures are available on the internet for free.

        Have a good day, Jerry

        Reply

  • Avatar

    Tom

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    Interesting subject. I wonder if there are limits to how hot or how cold something could be. It doesn’t seem possible that atoms could freeze solid or that they would never have at least some movement thus generating a tiny smidgen of heat.

    Reply

    • Avatar

      Jerry Krause

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      Hi Tom and other PSI Readers,

      The title of this article is: “What Temperature Is Absolute Zero?” Tom, you wonder: “how cold something could be”??? The person who wrote the title is playing with your mind!!! For what you wrote is enough evidence for me to conclude that you KNOW the answer to what you wonder is ABSOLUTE ZERO.

      And I suspect that you TOTALLY UNDERSTAND that the need of the Kelvin temperature scale is that a NEGATIVE TEMPERATURE really does not exist.

      Just as I read that Richard Feynman played a number game with the young son of a friend about word (idea) or INFINITY. Feynman knew this boy had learned to count and therefore knew about numbers. Therefore, his game involved the fact that there is always a number twice as big. And I have read that some consider that the number ZERO was an intellectual breakthrough. Which I do not accept because I consider it very evident there needed to be a number for NOTHING.

      And I have read that some philosophers (always intelligent people) of the past reasoned that matter was endlessly divisible (there was always a smaller particle but never ZERO). But in 1803, based upon experimental chemical results, forced the conclusion that matter was composed of tiny particles given the name atoms in the English language. However, Dalton did not and could not explain what these atoms were except he knew from chemical experiments that atoms of different elements were somehow different from each other.

      And he knew that atoms had a ‘electrical nature” because batteries had been invented any a process termed electrolysis had been developed to separate mixed elementary matter into pure elementary matter called ‘elements’. But none of this chemistry was done by reasoning, it was done by doing experiments. Just as new particles of matter are still being created by chemists.

      Tom, thank you for your comment because it stimulated what I have just written. Of which you can judge its value because PSI allows this free flow of ideas.

      Have a good day, Jerry

      Reply

  • Avatar

    Herb Rose

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    How do you detect something that is not radiating energy? We see space as empty even though it contains energy because there is nothing to radiate that energy..We see our shadow because an area is radiating less energy. If we were standing on a cliff there would be no shadow because of the absence of energy radiating towards us. How do you detect nothing?
    If they are using lasers to slow the atoms doesn’t that mean the atoms are absorbing the energy from the laser? How can they absorb energy and nor radiate energy?
    If energy cannot be destroyed but must be transferred to another object, what object is absorbing the energy being lost by these atoms?
    The stars are shining during the day but can’t be seen because the sky is emitting more light. Is the radiation from the atoms not detected because of background radiation?
    Since energy is emitted as a wave how do you know that the lack of observation is not the result of cancelation by an opposite wave instead of an elimination of the emitted radiation?
    Does not seeing anything prove that there are invisible objects?

    Reply

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