The Absolute Zero

THE ABSOLUTE ZERO

All you need to know about “The lowest temperature possible in our universe”- THE ABSOLUTE ZERO

W

e always hear about temperatures around us or at least we read about them in our books. But one peculiar thing that I noted about them was that on the temperature scale while talking about rising temperatures or hot temperatures they can go as high as a thousand degree Celsius(for e.g. the temperature of the sun is about  5,505°C) or some even infinitely high values. But I never had seen this high variation in case of colder temperatures. I bet for you too that most of you might also have not heard about temperatures much below the freezing point of water i.e. 0°C. The concept of absolute zero is the explanation to this indiscriminant variation between the temperatures below the freezing point (0°C) of water and those above the steaming point (100°C) of water.

What exactly is it?

The temperature of -273.15°C (0°K) is called absolute zero. It is the lowest temperature possible in our in our universe. This means that it cannot get colder than -273°C. Sir William Thomson, 1^st Baron Kelvin first discovered about it in 1848. He set absolute zero as 0 on his temperature scale to get rid of the negative values as present in Celsius scale. This is how he invented the Kelvin scale (as we call it now).

According to Lord Kelvin, heat is just the movement of particles or we can say molecules moving around in a substance. So absolute zero, according to theory, is a condition when molecules stop moving. But mathematically, this cannot be proven. When the speed of the particles at the molecular level gets very low because of the decrease in temperature (kinetic energy of a particle is directly proportional to its temperature) there is still some heat around which keeps it moving. Also according to Heisenberg’s Uncertainty principle we cannot know both a particle’s momentum and position at the same time. But if the temperature of a particle has to be absolute zero then this would mean that its motion will be zero. So its momentum (p=vm) would also be zero and hence its position and momentum will be known at the same time. But this defies the condition of Uncertainty principle. This means that the condition of true -273°C (0°K) is not possible but it is possible to reach really close to it like a billionth of a degree away. But that one too is not an easy thing to accomplish. And the journey along that is quite long. Let’s see:

How the journey around decreasing temperatures leads us to absolute zero-

SUBSTANCES\PLACES	TEMPERATURES
Freezing pt. of water	0°C
Avg. winter temp. of Canada	-15°C
Freezing point of Mercury	-38.7°C
Avg. surface temp. at Moon during the day	-53°C
Avg. surface temp. at Mars during the day	-63°C
Sublimation point of Dry ice (solid Carbon dioxide)	-78.5°C
Coldest surface temp. ever recorded on Earth	-89.2°C
Freezing point of Chlorine	-101.8°C
Freezing point of Ethanol (alcohol)	-114.14°C
Oxygen liquefies at	-183°C
Nitrogen liquefies at	-196.8°C
Freezing point of Nitrogen	-210°C
Freezing point of Oxygen	-223°C
Hydrogen liquefies at	-253°C
Freezing point of Hydrogen	-258°C
Helium liquefies at	-269°C
Avg. temp. of Universe	-270.28°C
Temp. of first ever created Bose-Einstein Condensate (fifth state of matter)	170nK
Lowest temp. artificially created	1pK
Absolute zero	-273.15°C

The above table shows how lower we have to go in order to reach absolute zero. As we go on decreasing temperatures, rate at which chemical reactions happen is slowed down significantly or either stopped entirely. Below 200°C only 3 gases of 3 liquid elements remain unsolidified. Every element except that is in solid state. Unprotected exposure of temperatures at this level is highly lethal to humans. When we reach -250°C conditions become so extreme that almost all chemical reactions are completely halted. Movement for even particles becomes difficult. Only two gases remain that are not solidified. Also, the surface temperature of the minor planet 90377 Sedna is -261°C which makes it the coldest body in our solar system though it reaches that temperature once in every 11,000 years as it is its orbital period. At 272.2 degrees below zero every element is frozen and any chemical reaction is not possible. And even going lower after that, there comes the absolute zero. At this condition movement for any molecule, element or even an atom is not possible. Everything stops here but as we have discussed above, again this condition is not possible. The things that are possible is what we saw in the table above.

The opposite of absolute zero-

As we now know what is the lowest temperature possible so the question arises is there any highest possible temperature in our Universe or is it just infinite. I mean the temperatures like 5.5 trillion degrees have been created in the laboratories on earth. Though these are generated for a very minimal time but what is the maximum value of temperature possible. Is there any opposite existing value for absolute zero? Actually yes, it is possible. But to understand that you might need to know some things about radiation.

Ø Radiation – Radiation actually is the loss of energy either in the form of waves or particles.This radiation is of different types like infrared, ultraviolet, gamma rays, alpha rays et cetera divided on the basis of wavelength. Scientists can detect wavelengths of the range 2nm-2500nm.  

Now, according to Wien, temperature is inversely proportional to the wavelength of radiation emitted by objects. So if we would keep on increasing the temperature, the wavelength would go on decreasing. On increasing the temperature of the object to 1.41 X 10^32 K which is like 141,000,000,000,000,000,000,000,000,000,000 degree Kelvin, the wavelength of the radiation becomes 1.6 X 10^(-35)m (which is 0.00000000000000000000000001616nm and could not be reduced. Decreasing any length beyond that is not possible. So, there comes the shortest distance possible in our Universe known as the ‘Planck length’. It is not possible to obtain any shorter length than the Planck length. This means the temperature cannot be increased further because the wavelength cannot be reduced, which gives us the highest possible temperature in our Universe.

But even after that one would still wonder how can we not add or provide energy to something. Like, in whichever state something is we could still add energy to it in the form of heat or something else. So if we add more energy to an object even after the condition of Planck length is achieved it would result in the formation of a black hole. And this black hole would be different from the others in the sense that unlike other black holes, this one is not made from mass but from energy. (Generally black holes are formed when a “very X 10^100” large mass is compacted in a very small space, for e.g. the mass of a normal black hole is 3-4 times the mass of the sun present within a diameter of 8-9 km.)  

First black hole photo taken by Event Horizon Telescope