Re: Planck length and Planck time

[Maurice Barnhill <mvb@UDEL.EDU>]

Since, as far as I can tell, no one else has answered this one, I'll
give it a crack.  I have taught some of this material, but done no
research on it, so I have waited to see if anyone else would tackle it.

   The Planck mass Mp is the mass whose Compton wavelength h-bar/(Mp c)
is equal to the radius of a black hole with the same mass.  It is the
only available fundamental mass scale for gravitational effects, but at
the same time represents that mass where doing gravity without including
quantum mechanics becomes intolerably suspicious.  The Planck length is
the Compton wavelength associated with the Planck mass, and the Planck
time is the time that it takes light to travel one Planck length.
Again, these are the only length and time that can be constructed out of
the gravitational constant G and the constants h-bar and c.


A Rusli wrote:
> Dear friends,                   30 May 1999
>
> I have wondered for quite a time, how the Planck length and the Planck
> time, related to the beginning of the Universe (I guess), are defined. I
> have seen somewhere their definition in terms of other fundamental
> constants, however I missed the reason behind those definitions.
>
> I hope somebody can enlighten me on this. Thank you.
>
> I would also say a very belated "thank you very much" for several
> explanations on the April Fool's Day Mr Litre.
>
> A Rusli
> Physics Department, Institut Teknologi Bandung
> Indonesia

--
Maurice Barnhill, mvb@udel.edu
http://www.physics.udel.edu/~barnhill/
Physics Dept., University of Delaware, Newark, DE 19716