Welcome to my brain melt. Although physics was once one of my majors, I pursued the field of medicine. Passion for physics never went away. While trying to understand the nature of reality, I struggled with some concepts. Planck length was one of them.
Well if somebody say hands you a piece of a string or whatever and tells you that you cannot cut it any shorter, would you believe them?
“The Planck length is the scale at which classical ideas about gravity and space-time cease to be valid, and quantum effects dominate. This is the �quantum of length�, the smallest measurement of length with any meaning.
And roughly equal to 1.6 x 10-35 m or about 10-20 times the size of a proton.”
( source of text in quotation:physlink.com).
OKAY! INTERESTING! So in Newtonian physics, there is no length smaller than Planck length that can exist. BUT WHY, WHY WHY ?..
Are we saying that reality, as we know it, has a length limit..or the basic unit length of reality is the Planck length?
BEFORE WE GET THERE.... allow me to introduce something called ULTRAVIOLET CATASTROPHE. It is like a very interesting opening to this whole story. Okay here we glow...err go.
Things glow. You have seen a hot filament glow. Heat up a metal high enough and it glows. Lava glows. My first though was Olay regenerist but that’s not it. The temperature of the glowing object determines the color of the glow. Hmmm.
Sun’s surface temperature is about 5500 degrees centigrade.It glows in multiple colors that appear white to us. You emit a glow but in the infrared spectrum and that is due to your body temperature. I will glow strongly if you upvote my content.
Now understand th concept of a blackbody. Most object when hit with light, absorb some of it, reflect some of it and emit light. A blackbody does not reflect light. It only does the other 2 things. Now there were 2 guys, lord Rayleigh and his colleague James Jeans who tried to find out what colors a blackbody would emit at different temperatures. Their calculations suggested that a blackbody should emit infinite amounts of ultraviolet light. OBVIOUSLY SOMETHING HAS GONE WRONG. This is an impossibility and would go against established laws of physics such as conservation of energy.
This problem was termed ULTRAVIOLET CATASTROPHE.
We cordially welcome Max Planck now into this discussion. 🥁( drumroll).
As luck would have it, Max Planck was trying to figure out how heat flows from a hot object to a cold object. With his work he determined that a blackbody could only emit radiation in discrete quantities or quanta.
His work resolved the discrepancy described by the ultraviolet catastrophe. It also gave rise to quantum physics.
Planck showed that:
So it appears that first Planck discovered the PLANCK CONSTANT. He later also discovered that Planck constant can be used to define natural units like the Planck length.
A more detailed description of this including neutral units is for 2 kinds of smart people, physicists and mathematicians. The rest of people like you and I specializing in other fields, hang in there. I am trying to make this as convenient as possible.
There are 2 constants in general relativity G= gravitational constant and C= Speed of light
h, remember was the Planck constant.
“ The units of G are (distance * distance * distance) / (mass * time * time) The units of c are distance / time
The units of h are distance * distance * mass / time
Planck observed that there is only one way to combine these constants to obtain a distance:
Distance = square root (hG/cc*c)
The resulting distance is called the Planck length.“
It is a curious observation that Planck made: there is no other way these constants can be put together to get distance. This means that any theory using only these three fundamental constants to predict distance (as a theory of quantum gravity would have to) will give a distance that is this length multiplied by a numerical constant. This gives the Planck length its meaning, because physicists suspect that it is the distance at which the effects of quantum gravity will become apparent and may even be the smallest meaningful length that exists.
( source in quotes is from Physlink.com)
So now we have a very basic non mathematical understanding of how all this came about.
Now the existence of any 2 particles separated by a distance smaller than Planck length is not possible in the sense that can cannot be “seen” as separate particles at that distance. To observe anything at that level we will have to spend tremendous energy to the point that it will theoretically create a microscopic black hole and thus unobservable. The Planck length thus stands at the interface of quantum physics.
Does this suggest that reality is pixelated? Yes it does to a great degree although that can be argued. Scientists from Quantum gravity research labs also believe that reality is pixelated. ? Similar to a computer generated virtual reality.
Image source : google.
Long live and enjoy your pixels.
Ned