How have we figured out the Plank length of the universe?

[hsdrop]

how have we figured out plank length of the universe ?and know its that size ?

 

[Vanadium 50]

This makes no sense. It's like saying "have we figured out the radius of an apple for a skyscraper?".

 

[hsdrop]

lol sorry ok i know we have a Planck length i was wondering how we found it

 

[Vanadium 50]

Like we "found" the foot or the meter. We defined it.

 

[hsdrop]

hmmmm it always the easy questions that are the most difficult to answer,lol. i know we have a minimum length that we can mescher SA particles with i was just wondering how we came up with it or how we knew that it was the smallest light we can mescher by sorry for not being more chear with my question and thank you for replying

 

[Student100]

hmmmm it always the easy questions that are the most difficult to answer,lol. i know we have a minimum length that we can mescher SA particles with i was just wondering how we came up with it or how we knew that it was the smallest light we can mescher by sorry for not being more chear with my question and thank you for replying

Plank length was defined from several other physical constants. PL, versus lengths we can actually currently measure are several orders of magnitude apart. I think the last thing I read had the smallest length measured somewhere around 10^-18m. Which is incredibly small, but no where near PL at 10^-35m.

So PL has use in theory, but we don't have any way to currently measure lengths that small. It would also be wrong to say it is the minimum length that can be measured - we can't yet test that experimentally.

 

[Algr]

Like we "found" the foot or the meter. We defined it.

I don't think we did.

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.

 

[Student100]

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.

The quote seems like gobblygook. There is no current physical significance of PL, and no way to actually test what happens when you measure lengths that small. For all we know QG could very well require other physical constants than c, G, $\hbar$. Plank just happened to define this length a certain way.

I don't think it correct to say

This is the "quantum of length" the smallest measurement of length with any meaning

Without experiments, no physics. Just half-blind speculation.

 

[Vanadium 50]

The quote seems like gobblygook.

For good reason.

Planck units have no mystical power. The Planck charge is 11.7 electron charges. The Planck resistance is 30 ohms. Nothing magic happens there. It's probably true that quantum gravity becomes important at a scale of perhaps 10 or 20 Planck lengths, but that's just a statement about the relative sizes of h, c and G.

 

[Algr]

The Planck charge is 11.7 electron charges. The Planck resistance is 30 ohms.

The Planck flavor is Blueberry Fudge. The Planck address is 1325 Maple st. But that doesn't invalidate EVERYTHING Max Planck did.

BTW, Some of the formatting was lost in that quote (Those are supposed to be exponents, not ranges.) Let's see if this works:

https://wikimedia.org/api/rest_v1/media/math/render/svg/41c085ebc8add3aad57122d5d1487068b21154bd

 

[hsdrop]

The Planck flavor is Blueberry Fudge. The Planck address is 1325 Maple st. But that doesn't invalidate EVERYTHING Max Planck did.

BTW, Some of the formatting was lost in that quote (Those are supposed to be exponents, not ranges.) Let's see if this works:

[PLAIN]https://wikimedia.org/api/rest_v1/media/math/render/svg/41c085ebc8add3aad57122d5d1487068b21154bd[/QUOTE]
hay you have his phone number I want to call him up and ask how "small" he really is

 

[Fervent Freyja]

hay you have his phone number I want to call him up and ask how "small" he really is

What is that supposed to mean? Are you implying that Max Planck had a small member? That is a horrible joke (though telling).

 

[DrClaude]

There is a very good Insight on the subject of the Planck length:

https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/

 

[OCR]

how have we figured out plank length...

I want to call him up and ask how "small" he really is

Well, now you've done it !...

You're on Max's "really, really bad" list... he's likely to whop you on the head with a big board .... lol

See... he doesn't look very happy about being made sport of....

https://en.wikipedia.org/wiki/Max_Planck​