How 4 fundamental constants reveal minimum scales where physics ends: Planck scale

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0:00-3:36 How to create a universe
3:37-6:05 Most important constants
6:06-7:39 Derivation of Plank scale
7:40-11:44 Significance of Planck scale
11:45-13:46 Fine tuning & other speculations

How the Planck scale is derived from the most important fundamental constants in physics. This is where our physics ends. If you wanted to simulate the universe in a computer, you would need to enter about 26 fundamental constants.

15 of these are the rest masses of the fundamental particles of the standard model. 4 are the quark mixing parameters, required to describe the weak nuclear force. 4 are the neutrino mixing parameters. Cosmological constant describing the acceleration present in the universe’s expansion. fine structure constant which describes strength of the electromagnetic force, and the strong coupling constant – which defines the strength of the strong nuclear force.

But 4 are special fundamental constants apply to everything everywhere. The gravitational constant G - It can be thought of as the proportionality factor between the strength of gravity and the masses creating that gravity. It has units of length cubed divided by mass times time squared.

The speed of light, C is like a conversion factor between Mass and energy, or a conversion factor between the time dimension and the three spatial dimensions of our 4 dimensional universe.

Planck’s constant is the fundamental constant that sets the minimum scale of quantum phenomenon. It can be found in just about any quantum mechanics equations. It has units of mass times distance squared divided by time.

Boltzmann’s constant plays a role in determining the amount of vibrational energy contained in the atom related to temperature. It is just the definition of the energy contained in one degree Kelvin and has units of energy per degree.

Using just 3 constants, G, c, and h we can get many Planck scale limits. If we manipulate them mathematically, we get a length. which is the Planck length. It is the minimum length that would be meaningful in quantum mechanics. :

We also get time, which is the Planck time. It is the minimum time that can exist that would be meaningful in quantum physics.

We also get energy by rearranging some of these constants. This is the Planck energy- the maximum energy that could be contained in a cube that had a size of one Planck length.

We can convert this Planck energy into mass by using Einstein’s equation. This represents the maximum mass that a cube of one Planck length could have.

Since these numbers are ubiquitous in physics, physicists often just use what’s called natural units, and set these constants equal to one.

What is the significance of the Planck scale? The Planck length is the shortest length that means anything in the equations of quantum mechanics. This is not to say that something smaller doesn’t exist.

It is the smallest scale that we can theoretically probe with particle accelerators. If string theory is true, then the strings would be as small as the Planck length, and would also be the smallest size of the loops in loops quantum gravity.

Strings would vibrate at minimum time scales of the Planck time. The movement of the spin network in LQG would occur in increments of Planck time. Planck time is the time it takes for light to travel one Planck length.

We have no idea what occurred prior to this time, nor do we have a model for what could have occurred.

Using the word before may in fact be meaningless because time itself started at this point. This would be the true beginning of creation. What lies below the Planck scale? It could be a kind of quantum foam where gravity could fluctuate or be in superposition.

Could space-time be in superposition like other quantum phenomenon? Perhaps, but this would violate some of the current understanding of gravity.

Planck energy converted to Planck mass is really a lot of mass equivalent to energy in a tank of gasoline or petrol in your car.

Some people have used the precision of the constants to argue for fine tuning, that any slight variation would have resulted in conditions which could not have created matter, or life as we know it.
#planckscale
#arvinash
#wherephysicsends
Others say that, the universe isn’t all that fine tuned for life because almost all the volume of the universe supports no life. Life only occurs on a very limited volume of the universe, namely on very special planets that have just the right conditions.
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Speaking from 20 years of experience as a teacher, you, sir, are a magnificent one.

jworldwide
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I loved the “yes we won the cosmic lottery, but how many ticket did we have to buy?” closing line. Keep up the good work Arvin!

leovalenzuela
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“That’s coming up right now!”. I adore the way you say that with infectious enthusiasm.👌

GururajBN
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wanted to learn about fundamental constants, ended up with existential dread. still great vid!

AADJYT
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This man is a gem. I didn't score well in my Physics exam and I was sad. After watching this I'm better now. I want teacher like you in my college. They always talk about lagging behind in syllabus but actually don't care in explaining the topic intuitively.Thank you very much.

infinityverse
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Awesome. Now I know why Max Planck is regarded as the father of quantum physics/mechanics. The foundation he created in physics has done a tonne of good for humanity.

I love your videos, absolutely eductive

hamzavictor
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I really like the moving graphics where the math manipulations are carried out. Those are elegant and useful. It's nice seeing the units sliding around so you can pause and copy them down and not have to keep checking yourself when you do it on your own.

craigwall
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This is too important to make everyone wait!

matthewbrennan
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Me listening to Arvin Ash: Like me reading Scientific American as a freshman in high school. Now, a masters in EE and lots of study of science later, I can understand most of the articles in Scientific American. Back in high school, I was very interested but 90% of the article was beyond me.
So - thank you for giving me something to tackle. There were lots of details here I do not understand, but that just means there are many things to learn/investigate. I love your videos.

redmeatvegans
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I am not a physicist by no means but this is the most well rounded video I have seen on the question of quantum gravity. I think we do not fully understand the world we live in with two major theories in physics conflicting each other. Think we truly did win the cosmic lottery.

BrightChocolate
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"how many simulations did our overlords create?"
The people who made the simulation, silently observing: *yes*

ingenuity
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Mr. Ash, Very Impressive video. Packed so much information in just 13 mins. Hands down, one of the best videos I have seen all year. Thank you!

daveanderson
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Of all the many physics presentations I have seen this is the most understandable. It is the best!

viknumbers
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There very well may be universes where life is not possible, but they don't have anybody there to ask why.

MLB
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What an amazing video! So straight forward and easy to follow. I wish I had these resources when I was back in school 20 years ago. You are an amazing teacher Arvin. Keep 'em coming! 👊

asmeetp
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Blows my mind. Also blows my mind that I understand. Thanks Arvin Ash!

DavidTJames-yqdr
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and I'm subscribed!

SO many people, even experts in the field, misinterpret Planck length and time as being the shortest/smallest thing that can carry information and believe units smaller simply cannot exist, all because it's fundamental. But here it's described properly, possibly a first for the YouTube platform! Thank you so much this!

Eclipsed_Archon
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For everyone who involved making all this videos, you are making great content.👍👍👍👍👍👍

Alignforce
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It felt so satisfying when epsilon(naught) and mu(naught) determine the speed of light. It gives a vibe that everything is connected.

sam_bit
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I, for one, would like to thank our ant overlords for choosing these constants.

MagruderSpoots