What is the Planck time?

Max Plank may be relatively unknown, but he should not be. After all he is considered to be the Father of Quantum Mechanics. The relationship of the ratios of Plank's measures of mass, energy, and length are known, as the Planck Constant, are at the foundation of Quantum Mechanics, and were earth-shaking, though not recognized as such, at the time. Although Einstein knew its value, since he and Planck shared their work, and developed some of the same theories simultaneously. However, the article says that until the 1950's Planck time was considered too insignificant to be relevant!

This article is a bit technical in places but can be read skimming over difficult parts, to understand Planck's place in the history of modern science. And it tells about a current better understanding of quantum gravity as the first force of the four to emerge after the expansion of the universe started.

The following part of the article, near the end, is what is so fascinating, and highly pertinent to current research:

"Because the Planck time is so impractically small, it was largely ignored by scientists prior to the 1950s, according to K. A. Tomilin of the Moscow Institute for the History of Science and Technology. At best it was considered an interesting curiosity with no real physical significance. Then, when physicists started looking for a “theory of everything” that would encompass both gravity and quantum mechanics, they realized that the Planck time might have enormous significance after all.

The key lies in the fact that the Planck time, along with the other Planck units, incorporates both the gravitational constant G and Planck’s constant h, which is central to quantum theory. Inadvertently, back in 1899, Planck had come up with a formula that straddled both halves of modern physics, long before anyone had started looking for such a connection."
[. . .]
"In the universe we see today, there are four fundamental forces: gravity, electromagnetism and the strong and weak nuclear forces. But as we look backward in time through the first moments after the Big Bang, the universe becomes so hot and dense that these forces gradually merge into each other. It all happened very quickly; from ten microseconds onward, the four forces looked just as they do today. Before that, however, there was no distinction between the electromagnetic and weak forces – and prior to 10^-36 seconds, these were joined by the strong force as well.

At this point, gravity was still a separate force – and based on current theories, we can’t look back any further in time than this. But it’s widely believed that, given a better understanding of quantum gravity, we’d find that prior to the Planck time gravity was also merged into the other forces. It was only at the Planck time, around 5 × 10^-44 seconds after the Big Bang, that gravity became the separate force we see today."