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Temperature is a fundamental concept in physics and is vital to life in many forms. However, at both extremely high and low temperatures, the behavior of matter can become quite strange. Below is a list of ten intriguing facts about this essential factor in our world:
10. The Hottest Temperature Ever Created by Humans
The hottest temperature ever achieved by humans is an astounding 7.2 trillion degrees Fahrenheit, or roughly four billion degrees Celsius. To give you some perspective, that’s around 250,000 times hotter than the core of the sun. This extraordinary heat was generated at the Brookhaven National Laboratory in New York, using their 2.4-mile-long Relativistic Heavy Ion Collider. Scientists were smashing gold ions together in an effort to recreate conditions similar to the Big Bang, forming a quark-gluon plasma. In this unique state, protons and neutrons, the particles that make up atomic nuclei, break apart, resulting in a “soup” of their constituent quarks.
9. Light Performs Incredible Feats When Cooled
We've already touched upon the fascinating phenomenon known as the Bose-Einstein condensate. This event occurs when matter is cooled just above absolute zero. While this effect was previously only observed at such ultra-low temperatures, scientists have now been able to recreate it using light rather than matter, even at room temperature.
This breakthrough was made possible by the relative density of both the matter and the light. Jan Klars, one of the scientists involved, explained, “Our photon gas has a billion times higher density, and we can achieve the condensation already at room temperature.” They made light pass between two mirrors with dye particles in between. As the light bounced back and forth, it lost a bit of energy each time it passed through the dye. Eventually, at room temperature, the light began behaving like a super-cold gas composed of traditional matter. This finding holds significant potential, as it could pave the way for new types of lasers—an ultimate aim in physics research.
8. The Extreme Temperatures of Our Solar System
Some of you might already be familiar with these comparisons, but take a moment to consider what they truly represent when compared to the everyday temperatures we experience. The sun—if we can call it anything less than extreme—is incredibly hot. Its core reaches temperatures of around twenty-seven million degrees Fahrenheit (fifteen million Kelvin). By contrast, its surface is actually a bit cooler, with temperatures less than ten thousand degrees Fahrenheit (roughly 5,700 K).
The Earth's core is roughly the same temperature as the sun’s surface. Aside from the sun's core, the hottest part of our solar system is the core of Jupiter, which is, astonishingly, five times hotter than the surface of the sun.
And the coldest place known to us? It’s actually on our very own moon, where the temperatures in the shadowy depths of certain craters are only thirty Kelvin above absolute zero. These temperatures, as recorded by NASA’s Lunar Reconnaissance Orbiter, are even colder than those found on Pluto.
7. Triple Points
The SI unit for temperature is the Kelvin. This scale is defined by two key points: absolute zero, the lowest possible temperature, and the triple point of water. A triple point is the precise temperature at which a substance’s three traditional states—solid, liquid, and gas—exist in equilibrium. At this point, even the tiniest change in temperature or pressure can cause a substance to shift from one state to another.
To define one Kelvin, you take the difference between the triple point of water and absolute zero, then divide that value by 273.16. While the triple point of water has limited practical uses, its proximity to the melting point plays a crucial role in generating the thin watery layer needed for people to ice skate.
6. Scientists Overlooked It
The principles of nature that govern temperature are known as the Laws of Thermodynamics. Initially, there were only three laws—the first, second, and third—but later, scientists introduced a fourth. The most recent law states, “If two systems are each in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.”
In simpler terms, this means that if two objects don’t exchange heat with a third object, they won’t exchange heat with each other. This is the fundamental principle used to define objects as having the same temperature.
Scientists soon recognized that this law is essential to the field of thermodynamics, and they also realized that it should have been the first rule they created. Since the “first law” was already taken, they respectfully called it the “zeroth law.” This term was coined around 1935, meaning that it took scientists a couple of centuries to formally define what temperature truly meant in the context of thermodynamics.
5. Extreme Temperatures in Human Habitation
Some individuals have made their homes in some of the most extreme locations on Earth. The coldest permanently inhabited places in the world are Oymyakon and Verkhoyansk, two towns in Siberia, which we’ve previously mentioned. During the winter months, the average temperature there falls well below minus fifty degrees Fahrenheit.
The coldest city in the world is also found in Siberia. Yakutsk, a city with a population of 270,000, experiences winter temperatures nearly as harsh as its smaller counterparts, often dipping below minus forty degrees Fahrenheit. However, during the peak of summer, temperatures can soar to nearly ninety degrees Fahrenheit.
The highest recorded average temperature belongs to the now-abandoned town of Dallol in Ethiopia, which reached an average of ninety-six degrees Fahrenheit during the 1960s. The record for the hottest city goes to Bangkok, where average air temperatures regularly exceed ninety-three degrees between March and May.
As for the hottest workplace, that distinction likely belongs to the Mponeng gold mine in South Africa. At two miles beneath the Earth's surface, rock temperatures can climb to 150 degrees Fahrenheit. To make working conditions survivable, ice must be pumped into the mine, and the walls are insulated with concrete.
4. Coldest Man-Made Temperature
The process of cooling things has led to many groundbreaking and significant discoveries in science. Humans have successfully created the coldest known substances in the universe, far colder than anything found naturally. Refrigeration technology can achieve temperatures as low as a few milliKelvins. The record for the coldest temperature ever recorded is just under one hundred picoKelvins, or 0.0000000001 K. To reach such extreme cold, a method called magnetic cooling is required. Lasers can also be used on a smaller scale to reach similar temperatures.
At these incredibly low temperatures, the behavior of matter changes drastically from its usual state (as seen in the Bose-Einstein condensate, for example), which is crucial for uncovering the strange and fascinating aspects of quantum mechanics.
3. The Planck Temperature
Absolute zero has been mentioned numerous times on this list, and we’ve even discussed it on Mytour before. But what about the other extreme of the temperature scale? How high can temperatures actually reach? The simple answer is that we don’t know for sure; this is a question that sits right at the cutting edge of modern fundamental physics.
The highest temperature frequently referenced in scientific discussions is the Planck Temperature. This temperature is believed to be the hottest that ever existed in the universe, occurring just a fraction of a moment after the Big Bang. It’s around 10^32 Kelvin. To put that into perspective, it’s roughly ten billion billion billion times hotter than the temperature we just mentioned, which was already 250,000 times hotter than the core of the sun. And you thought your bath water was hot. According to the Standard Model, the Planck Temperature represents the highest possible temperature. Any higher, and the laws of physics as we know them start to break down.
It’s possible that temperatures could keep increasing beyond this point, but we really don’t know what would happen if they did. Anything hotter than that essentially doesn’t fit into our current understanding of the universe.
2. Caloric Theory
Heat is a physical property of matter. Simply put, the hotter something is, the more energy its particles possess as they move. The atoms in a red-hot solid vibrate faster than the atoms in a cooler object. Similarly, particles in liquids or gases move at speeds that correlate to their temperature. This is basic stuff you may have learned in high school, but for centuries up until the late nineteenth century, scientists thought heat itself was a substance. This idea is referred to as caloric theory.
According to caloric theory, scientists believed that this ‘heat’ substance would evaporate from a hot object, causing it to cool down. It would then transfer from a hot object to a cooler one. Although the idea was fundamentally flawed, many predictions derived from caloric theory were accurate, and scientific progress was still made in spite of it. The theory had supporters until the late nineteenth century, when the mechanical theory of heat was established beyond doubt.
1. The Universe Is Cooling Down
If you were to take a thermometer into deep space and leave it in the absence of any radiation source, it would measure 2.73 Kelvin, which is just below minus 454 degrees Fahrenheit. This temperature represents the coldest naturally-occurring temperature in the universe.
Space is kept just above absolute zero due to the residual background radiation from the Big Bang. While space is indeed extremely cold, it's fascinating to note that one of the most significant challenges astronauts face is actually heat. Bare metal on objects in orbit can soar to 500 degrees Fahrenheit (260°C) because of direct exposure to the unfiltered heat from the sun, requiring special coatings to bring the temperature down to a more manageable 250°F (120°C).
Outer space, however, is continuously cooling. This phenomenon was predicted by theory long ago, and recent observations have confirmed that the universe is cooling at a rate of about one degree every three billion years.
The universe will keep edging toward absolute zero, though it will never actually reach it (which is impossible). The universe’s background heat has negligible impact on us; the influence of the celestial bodies within our solar system and galaxy far outweighs it. So, it won't be reversing global warming, if anyone was thinking that way.
