# How hot can it get in the universe?

We are slowly drawing near the cold season now. But our winter temperatures are nothing in contrast to the coldest temperature possible. The absolute zero is taken as minus 273.15 degrees Celsius (which equals minus 459.67 degrees Fahrenheit). Or in other words zero Kelvin. But what about the opposite? What is the hottest temperature possible in our universe?

In order to understand the lower limit of the temperature scale and a possible upper limit, we must first know what temperature even is. Thermodynamic temperature is a measure of the kinetic energy in molecules or atoms of a substance. The greater this energy, the faster the particles are moving, and the higher the reading an instrument will render. However, there is also the spectral temperature which is defined according to the wavelength at which the electromagnetic energy that an object emits is greatest. This is the temperature scheme that astronomers use to measure the heat in distant objects such as the sun’s corona or the gas and dust between stars.

Anyway, it would be practically possible to come close to the absolute zero point of minus 273.15 degrees Celsius (minus 459.67 degrees Fahrenheit), but due to quantum physical phenomena it can never be reached exactly. Heisenberg’s uncertainty principle states that it is fundamentally impossible to precisely measure the location and velocity of a particle.

But now regarding hot temperatures. Let us first start with ourselves, with the human body. Contrary to popular belief, there is no completely constant body temperature, it is influenced by many factors and thus fluctuates around. The average normal temperature is about 37 °C (98.6 °F).

We are an extremely sensitive organism. Thus we already undercool at 33 °C (91.4 °F) and experience life threatening dangers at 27 °C (80.6 °F). Below 20 °C (68 °F) we suffer death from freezing. Conversely, at approximately 39 °C (102.2 °F) we speak of fever. Hyperpyretic fever up to 42 °C (107.6 °F) is very dangerous, above 42 °C (107.6 °F) our circulation fails and at temperatures above 44 °C (111.2 °F) our enzymes denature and we die.

Let us now take a look at some temperatures from our everyday lives. Water boils at a temperature of 100 degrees Celsius (212 degrees Fahrenheit) – or does it not? Usually, the boiling temperature equals 100 °C and the aggregate state changes. However, it turns out that there is a factor that lowers the boiling point of water – the air pressure. Thus the water on the Zugspitze already boils at 90 degrees Celsius (194 degrees Fahrenheit) and on the Mount Everest you can actually boil water at 70 degrees Celsius (158 degrees Fahrenheit).

The coldest temperature ever measured on Earth is -89.2 °C (-128.56 °F) and it was measured on July 21, 1983 at the Vostok Station in the Antarctica. The heat record was measured on July 10, 1913 in Death Valley, USA at 56.7 °C (134.06 °F). The highest earth’s surface temperature since we started recording is 82.3 °C (180.14 °F) and was measured in the sand of the Turpan Basin in Xinjiang, China (record was published 1978). But it is going to become hotter, much hotter.

The maximum surface temperature of Venus, the hottest planet in our solar system, is 462 °C (863.6 °F). A lighter flame can get as hot as about 1,300 °C (2,372 °F). And at 3,500 °C (6,332 °F) carbon melts while silver and iron have already been boiling for a long time at such temperatures. But it gets even hotter. A conventional chemical bomb reaches up to 5,000 °C (0.032 °F), the earth’s core is about 6,000 °C (10,832 °F) hot. The temperature in a nuclear explosion is about 10,000 °C (18,032 °F) hot and the short-term x-rays in such a nuclear bomb can heat up to 10,000,000 °C (18,000,032 °F). Although this is considerably hotter than the atmosphere of the sun, the sun’s core is even hotter at 15 million degrees Celsius (27 million degrees Fahrenheit).

But this is nothing for the universe. The universe was 1 billion degrees Celsius (1,8 billion degrees Fahrenheit) hot when it was 100 seconds old. A newly formed neutron star is 99,999,999,726 °C (179,999,999,539 °F) hot. At the age of 10-4 seconds, the universe was unbelievably 1 trillion degrees Celsius (1.8 trillion degrees Fahrenheit) hot. But man has also surpassed that. We have managed to create temperatures of 5.5 trillion degrees Celsius (9.9 trillion degrees Fahrenheit) in the Large Hadron Collider at CERN in Switzerland.

However, we are not a match for the universe. Its temperature at the age of 10-35 seconds was the incredible amount of 1 octillion degrees Celsius (1.8 octillion degrees Fahrenheit). That’s a one with 27 zeros. And with such immense temperatures we are slowly approaching the end.

The hottest temperature physically possible in our universe amounts about 1,420,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000°C. That equals 1.42 nonillion degrees Celcius (2.556 nonillion degrees Fahrenheit). This is the so-called Planck temperature, corresponding to 1.417 * 1032 Kelvin. If we think of temperatures above this constant, the conventional laws of physics break down. Thus we can describe the Planck temperature as the absolute hot, the hottest temperature possible in our universe.

Interesting graphic:

Graphic: Information is Beatiful Studio for BBC Future, futurism.com

Featured image: pixabay.com