What’s the hottest colour of fire?
The colour of fire and its temperature are directly linked; red flames are cooler, blue flames are hotter. Acetylene and pure oxygen burns blue, at over 3,400ºC – the hottest temperature readily achievable with fuel and flame. That’s nearly hot enough to melt tungsten which has a has the highest melting point of any element at approximately 3,422ºC. And while that’s extremely hot on our very narrow human scale, it’s nothing compared to the temperatures achieved by nature.
Is blue the hottest colour of fire?
The hottest colour of fire is typically blue. Fire temperature is determined by the energy of the combustion process and the specific chemicals being burned. Blue flames generally indicate a higher temperature because they result from the complete combustion of fuel with ample oxygen, producing a hotter, more efficient burn.
Here is a rough guide to the temperature ranges associated with different colours of fire:
- Red: 525°C to 1,000°C (977°F to 1,832°F)
- Orange: 1,000°C to 1,200°C (1,832°F to 2,192°F)
- Yellow: 1,200°C to 1,400°C (2,192°F to 2,552°F)
- White: 1,400°C to 1,600°C (2,552°F to 2,912°F)
- Blue: 1,600°C to 3,000°C* (2,912°F to 5,432°F)
*Blue flames can indicate temperatures much higher than 3,000°C. For example, flames in certain plasma arcs can exceed 5,000°C.
What is the hottest temperature possible?
The hottest temperature possible, as far as current physical theories can predict, is known as the Planck temperature. The Planck temperature is approximately 1.416808×1032 Kelvin (K). At this temperature, it is theorized that conventional physics, as described by quantum mechanics and general relativity, breaks down and quantum gravitational effects become significant. The Planck temperature represents a limit beyond which our current understanding of physics cannot describe the behaviour of matter and energy.
The concept of maximum temperature in physics is indeed intriguing and complex. Let’s break down the details to clarify the confusion between Planck Temperature and Hagedorn Temperature.
Planck Temperature
- This is considered the highest theoretically possible temperature in the realm of modern physics. The Planck Temperature is approximately 1.416808×1032 Kelvin. At this temperature, it is believed that the effects of quantum gravity would dominate, and our current understanding of physics breaks down. Essentially, it’s the point where the energy of particles would be so high that gravity would need to be described using quantum mechanics. At the Planck temperature, the effects of quantum gravity become significant, and classical physics can no longer describe the phenomena.
Hagedorn Temperature
- This concept originates from the study of hadronic matter (matter composed of hadrons, which are particles made of quarks and bound by the strong force). The Hagedorn Temperature is a limiting temperature for hadronic matter, beyond which hadronic states cannot exist and a transition to a quark-gluon plasma occurs. The value often cited for the Hagedorn Temperature is around 2×1012 Kelvin. It’s important to note that this temperature is significantly lower than the Planck Temperature.
Clarifying the Distinction:
Planck Temperature: The highest theoretical temperature where known physics cease to be effective and quantum gravitational effects take over. It’s a fundamental limit. At the Planck temperature, the effects of quantum gravity become significant, and classical physics can no longer describe the phenomena.
Hagedorn Temperature: A much lower temperature associated with the phase transition in hadronic matter, leading to the formation of quark-gluon plasma.
Is there an infinite loop where hot becomes cold?
Some suggest that there may even be no limit to temperature as we know it; it could be a bizarre, infinite loop where hot becomes cold. But this statement although it contains some interesting ideas is not accurate according to our current understanding of thermodynamics and physics, no current physical theories support the idea of temperature looping back to cold.
Temperature Limits:
Lower Limit (Absolute Zero): Temperature has a well-defined lower limit, known as absolute zero (0 Kelvin or -273.15 degrees Celsius). At this temperature, the motion of particles theoretically comes to a complete stop. Absolute zero is the point where a system’s entropy reaches its minimum value.
Upper Limit: In theory, there is no known upper limit to temperature. As energy is added to a system, its temperature can increase indefinitely. However, at extremely high temperatures, such as those found in the early universe shortly after the Big Bang or in particle accelerators, the nature of matter and energy changes significantly, and our current physical theories (like the Standard Model of particle physics and General Relativity) may need adjustments or new frameworks to describe these conditions accurately.
Temperature as an Infinite Loop:
The concept of temperature forming a “bizarre, infinite loop where hot becomes cold” does not align with our current understanding of physics. Temperature is a measure of the average kinetic energy of particles in a system. As energy is added, temperature increases, and as energy is removed, temperature decreases. There is no known mechanism by which extremely high temperatures would loop back to being cold.
High-Energy Physics and New States of Matter:
At extremely high temperatures, new states of matter can emerge, such as quark-gluon plasma. These extreme conditions can challenge our current physical theories, but they do not imply that temperature itself loops back to cold.
The laws of thermodynamics related to heat flow:
The laws of thermodynamics govern the behavior of temperature and energy transfer. The second law of thermodynamics, for instance, states that heat naturally flows from hot to cold regions, not the other way around, which further supports the unidirectional nature of temperature change.
In summary, while there may not be an upper limit to temperature in the conventional sense, the idea of temperature forming an infinite loop where hot becomes cold is not supported by current scientific understanding. Temperature increases and decreases linearly with the energy of the system, and the behavior at extreme temperatures continues to be an area of active research in physics.
Laboratory Record for the Coldest Temperature:
The coldest temperatures achieved in laboratories can be as low as a few billionths of a kelvin above absolute zero. For example, scientists have managed to cool atoms to temperatures as low as 500 picokelvins (0.0000000005 K) using techniques such as laser cooling and evaporative cooling.
Th Coldest Temperature in Nature:
The coldest known natural temperature in the universe is found in the Boomerang Nebula, where temperatures have been measured at about 1 kelvin (-272.15°C). This is due to the rapid expansion of gas from the central star.
Heat Death and Absolute Zero:
The concept of “heat death” refers to a state in the far future of the universe where all energy is evenly distributed, and no thermodynamic work can occur. In this scenario, temperatures would asymptotically approach absolute zero but would never actually reach it because there would still be some residual thermal energy and quantum mechanical effects preventing it. Thus, while absolute zero is a theoretical limit, it is unlikely to be achieved naturally in the universe, even in the context of heat death.
Summary:
While humans have achieved high temperatures in controlled environments, nature far exceeds these, especially in phenomena like lightning. The hottest theoretical temperature is the Planck temperature, where physics as we know it breaks down. The concept of an infinite temperature loop is unsupported by current scientific understanding. Absolute zero is the theoretical lower limit of temperature, which is asymptotically approached but never naturally reached.
The BBC created an excellent visual representation of this in the form of an infographic.
