Since the Big Bang, temperature has formed, and nuclear fusion reactions occurring in stars, emitting light and generating heat, are the initial sources of temperature in the universe. When humanity had not yet developed technology, temperature was primarily derived from the sun. The sun illuminates Earth every day, providing light and warmth.
As we know, a planet can only support life at a suitable temperature, which is true for Earth and also for other life-supporting planets in the universe. What temperature is suitable? Different extraterrestrial beings have varying temperature requirements.
To delve deeper into the mystery of temperature, scientists have proposed a definition of temperature, categorized into above zero and below zero. From our perspective, temperature has no upper limit; it can increase infinitely, reaching tens, hundreds, thousands, or even millions of degrees. For instance, the surface temperature of the sun can reach up to 6,000 degrees, the core temperature can soar to 15 million degrees, and the temperature inside Earth exceeds 5,000 degrees. Currently, scientists have managed to raise temperatures to over 100 million degrees through nuclear fusion experiments. While temperature can rise infinitely, it cannot decrease infinitely; it has a lower limit of -273.15 degrees Celsius, known as absolute zero.
Temperature can increase infinitely but cannot decrease infinitely.
Scientists are uncertain whether absolute zero exists in the universe. While many acknowledge that temperature has no upper limit but does have a lower limit, they may not understand why this is the case. Now, let’s examine this from a scientific standpoint, through the microscopic world, to analyze and explain why there is no upper limit to temperature, only a lower one.
To understand why temperature has no upper limit but does have a lower limit, we need to explore the microscopic world of matter. We know that matter is composed of smaller particles, and the movement of all tangible matter is essentially the movement of these particles. The change in temperature differential is also a form of particle motion. As temperature rises, the activity of particles increases, making them more energetic, and the activity of these particles can theoretically continue to increase indefinitely. In this context, it also means that temperature keeps rising with no upper limit. However, as temperature continues to drop, the activity of particles decreases; they move slower and become less active until they eventually stop moving entirely, reaching a state of thermal rest, which hits a limit—absolute zero.
No particle can be absolutely at rest, so temperature cannot reach absolute zero.
The motion of particles cannot be entirely at rest; motion is absolute, while rest is relative. No particle can be absolutely at rest, so temperature cannot reach absolute zero, but can only approach it infinitely. Of course, our current research and conclusions about temperature are based on the present level of scientific understanding; whether these findings and conclusions are entirely accurate remains a mystery.
Based on current scientific understanding, we can only conclude that there is no upper limit to temperature, and the only lower limit is absolute zero at -273.15 degrees. For now, this conclusion is valid and accurate. However, thousands of years from now, it will be difficult to say whether this remains true.
The definition of temperature is a human construct, and it is unknown whether the concept of temperature in the universe aligns with this definition. This aligns with our understanding of time, representing how we interpret the concept of time within the universe.
