[flr (OP)]

Plank mass is 21.7651 micrograms.
Why is so big? For example the Planck length is extremely small.

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I am thinking at the Plank length as the minimum distance at which space can be thought; bellow Plank length probably there is no such thing as the distance between 2 points - but is that actually right??

What is then Plank mass and why is so big? Clearly we can conceive mass smaller than Plank mass, hence analogy with (my) understanding of Plank length won't work.

What is then the meaning of Plank mass?

[MikeS]

"The Planck mass is approximately the mass of the Planck particle, a hypothetical minuscule black hole whose Schwarzschild radius equals the Planck length."
http://en.wikipedia.org/wiki/Planck_mass

There's logic there I guess.

[imatfaal]

Plank mass is 21.7651 micrograms.
Why is so big? For example the Planck length is extremely small.

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I am thinking at the Plank length as the minimum distance at which space can be thought; bellow Plank length probably there is no such thing as the distance between 2 points - but is that actually right??

The planck length is not a limiting size due to any physical law - it is just the energy required to probe at that level is astronomical, and our ideas of the 4 forces no longer apply at those energies.    To make a particle accelerator that could accelerate something to high enough velocity to probe planck length scale we would need a version of the LHC about as round as the milkyway!

[lightarrow]

Plank mass is 21.7651 micrograms.
Why is so big? For example the Planck length is extremely small.

It's not so big: it's about 22!

In milligrams is even smaller: 0.022
In grams is even smaller: 0.000022
In kilograms is even smaller: 0.000000022
...

What I mean is that it's meaningless to say that the value of a constant with phisical dimensions is big or small; you can say this only with dimensionless constants, for example the fine-structure constant:
http://en.wikipedia.org/wiki/Fine-structure_constant