Planck's Temperature

Physics defines the coolest temperature possible in very clear terms, calling it ‘absolute zero degree Kelvin’ but the same cannot be said for the hottest temperature possible. Although physicists use the term ‘Planck temperature’ while referring to theoretically hottest temperature, the definite idea behind it is a little fuzzy.

What is temperature exactly?

Our intuitive idea of temperature is mostly related to the amount of heat that an object contains. Indeed heat energy is a vital part of the explanation. We gather from regular observations that heat has an inane tendency to flow from higher temperature bodies to cooler ones, much like a hot tea that slowly cools down. Heat energy in physics is described as the thermal energy possessed by particles due to random movement. Higher the heat energy possessed, greater is the random motion in particles.

Temperature is the description of this transfer of heat energy from hotter to cooler regions and is described in scales such as Kelvin, Celsius etc. Two bodies at same temperature give an idea that they both have the same amount of heat energy and thus, no transfer is taking place.

Describing absolute zero

Theoretically absolute zero is a point of temperature when no transfer of heat energy outwards from the system can take place. Simply put, it is the coldest state possible from which no amount of further thermal energy can be extracted. Though sounding basic in theory, this point is excruciatingly hard to achieve experimentally because some amount of heat i.e. random motion is always possessed by particles of a body. Though we have gotten really close to this point with help of flip-flopping magnetic fields and lasers, the exact point still exists on paper only for the time being.

Describing Planck’s temperature

Absolute zero describes the lowest point of temperature of a body from which no heat can be extracted. Following this reasoning, surely there must be a point of temperature for a body into which no more heat can be pushed? Planck’s temperature is a extreme that is often referred to as ‘absolute hot’. The approximate value of this point would be around 140 million million million million million degrees or 1.4 x 10^32 Kelvin! It is an astounding value to be sure and not one that is observed in our universe today. It is theorized that the only time a temperature this high could have been achieved would have been during the Big Bang. At this point the entire universe would have been concentrated into a negligibly small space making the random motion of particles as high as it could ever get.

If we stretch our imagination even further and ask what would happen if it got any hotter, one explanation would be that at such a stage forces like electromagnetism and nuclear forces would be at par with gravitation. Going even further our physics looks blurry because one needs to combine Quantum Mechanics with General Relativity to get a clear picture ahead, a task the scientific community is still working tirelessly on.

As far as practicality goes, Planck’s temperature exists only in theory. The conditions required for it demand time and space to confine in ways that have the rarest chance of happening in the future.