The Smallest Length: Why Everything Breaks At The Planck Length

Quantum Gravity, Episode 1

Is there a smallest possible length? Is spacetime continuous like a smooth fabric, or is it made up of "atoms"?

The Planck Length is the smallest length at which our current laws of physics still work. How do we know this? Watch the video to find out why quantum mechanics and general relativity predict that any lengths smaller than the Planck Length are hidden behind black holes.

Thanks for watching, and I hope you enjoyed! Please like and subscribe for more videos on amazing ideas in physics.
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[jorisboons]

Thank you! I was wondering for a while why the planck length is the smallest length we can work with in physics. I read about it, watched some videos, but your video made me finally understand it. Great combination of explaining with words, mathematics and visualisation!

[VoightComp]

Years ago, I saw a program on PBS in which a physicist was explaining Planck measurements and he casually mentioned something about the formation of a black hole. I never really could grasp what that was all about. Now I have. Thank you.

[joethearcticfox]

This is the best explanation of Planck length I've ever heard. Excellent synthesis of the math and the concepts. Thank you!

[stephan]

Wow. Two of the most complicated concepts in physics, combined, and explained in very real world terms, in under 10 minutes. VERY well done!

[TheNarwhalAssassin]

Love the explanation, but there’s a slight issue. E=pc only applies to objects with a very low rest mass compared to their momentum, while E=mc^2 only applies to objects with a very low momentum compared to their rest mass. You can’t use both equations in the same derivation, since that implies m << p and p << m, which is contradictory. Instead you have to use the full equation E^2=m^2c^4 + p^2c^2. With the proper equation, I struggle to reach the same conclusion algebraically. Also, in currently accepted scientific theories, the Planck length doesn’t have any special meaning; it’s just a mathematical trick to make a unit system where a bunch of constants have values of 1, like c, G, and h.

[etienne]

One of th most underrated vid on yt.

Explaining 2 complex concepts in less than 20 min and without jargon or mathematical barriers...

Sometimes internet is worth it after all.

[blackxis]

Man this was amazing. I think this guy taught us something that a professor at MIT cannot do in a whole year. Excellent video. Keep it up

[ziff_]

I'm convinced this dude is an advanced life form from another planet. I can't even fathom what it would be like to be this smart.

[agschwend]

This is by far the best explanation for what the planck lenght is that I have seen. Fantastic! Thank you

[savagebolt]

Matt, I don't really comprehend all the math, but how you explain it leaves me speechless.
You have a gift for teaching.
I kinda got it, & I subbed too!

[gotayu]

Thank you, wonderful video. If I understand correctly, the Planck Length doesn't say it is the smallest possible space for sure but from this point most of our physics laws, formulas and theory don't work anymore

[matthewgordon]

I couldn't follow the math at all, but the explanation of Planck Length being related to the Schwarzchild Radius was very enlightening. We can't see things smaller than that because they would be a singularity. Wild.

[PrinceWilliam]

That was a very cool video and you did the maths in such a way where it doesn’t fell at all (or rather, entirely) intimidating. Thank you for taking the time to make this and make it understandable for those looking to greater their understanding of the quantum.

[carlowood]

Thank God for YouTubers who aren't afraid of formulas. I seriously HATE those idiots who apologize in advance for showing, as short as possible, a (simple) formula, immediately assuring the viewer "don't worry, this will be the last formula" and stating that they know that formulas are intimidating and scary and they won't do it again. Result: you learn NOTHING.

[aussietaipan]

This was awesome, I have always wondered about the smallest object and length and without the math it still makes sense to me, Well done.

[tradtke]

Great video. I wish people would not say "physics break down" about this sorta stuff, though. It misled me for a long time in relation to black holes/singularities.

It's not technically wrong. Physics- the science, what we know about how the universe works, yes that "breaks down" in these extreme situations.

But many people think, like I did, that this is saying the universe breaks and stops working and returns a blue screen of death. There's very little reason to believe that's the case. It's more likely that something predictable happens and it's governed by laws of physics, just ones we don't and possibly cant know.

To me, this difference was a rather profound one, and avoiding the language "physics breaks down" or at least explaining your use of the phrase would probably help others like me with this misconception.

[kinvert]

I never understood this before, but it was explained so clearly that around halfway through the video I was already predicting the end of it.

Thank you!

[mambe]

FINALLY a video that actually explains the planck length properly and concisely

[contessa.adella]

There is an intuitively simpler concept without the delta P and x maths stuff. 1) At very small scales below protons, there is no solid matter..it is all packets of energy 2) As the frequency of a photon (energy packet) rises, so does its energy, but the wavelength gets correspondingly shorter 3) You must reach a point where the high energy - mass equivalence fitted into the small wavelength reaches the Schwarzschild radius….Bingo! Blackhole and the photon drops out of existence. This gives a minimum wave length of Planck size…An over simplification of course and doesn’t account for Quantum effects..or Hawking Radiation…But it provides an imaginable mechanism. This is how I understood and calculated the minimum length back in my college days thirty years ago! I went in to realised crossing the smallest length (Planck) at the highest possible speed … C … provided a minimum length of possible time (10e-43s) or the Planck time interval. I was quite proud of these workings using pretty basic physics formulae since my maths algebra ability is poor and stuff like calculus is beyond me. This means the space around us is seething foam of holes. Like the safety net below a trapeze artist…anything bigger than the holes rolls around through space, but anything smaller pops through the holes and is gone. What happens to that missing energy is unclear…maybe it Hawking radiates immediately out as a new radiation? Or a quantum effect ‘deals’ with it…Beyond my knowledge cache.

[mpolier]

That was awesome ! Thank you so much. As a musician and social worker, I’m fascinated with quantum physics, but have no formal education on the subject. Your explanation of the Planck length may be the first I’ve understood enough to make ‘some sense’ out of the paradoxical world of quantum physics.