What's the "middle" size ?

[Guest]

I was wondering, what's the middle size, between the smallest thing known and the biggest one ?

For example, is it bigger or smaller than a human's size ? Are human being rather "small" or rather "big" compared to the other thing in the universe ?

If anyone know I would be curious to get the answer

[selden]

There is such a large difference in size between the smallest possible things and the largest possible, that there's no one answer.

I'd suggest exploring
http://microcosm.web.cern.ch/microcosm/P10/english/welcome.html

.

[julesstoop]

If we think in a linear way (so not in powers of n), we are defenitely small. The difference between almost zero (the smallest) and 180 cm is defintely a lot smaller than the differnce between 180 cm's and the size of the universe.
:P

[Matt McIrvin]

I remember reading the Scientific American book adapted from Charles and Ray Eames' "Powers of Ten" films, and noticing that the pictures ran out at 10^-18 m (distances covered by quarks dancing inside a proton) on the small side, but went up to something like 10^25 m on the large side (a billion light years-- today we'd probably want to draw one picture more and include the results of the great redshift surveys, at what will probably be the largest order of distance magnitude ever directly accessible to observation, because of the finite age of the universe and the speed of light). Going by that, we'd be a few powers of ten closer to the small frontier than the large.

On the other hand, the position of the small frontier is open to revision and quibbling as well; the pictures run out as much because of the inadequacy of pictures in a quantum world as the inadequacy of human knowledge. A wavelength of 10^-18 m corresponds to an energy on the order of 2 GeV, which is just the rest mass of a couple of protons. Modern particle accelerators can accelerate particles up into the TeV range and often study interactions with center-of-mass energies of hundreds of GeV, so you could argue that 10^-20 or 10^-21 m would be more accurate today.

I should also say that no nonzero size for electrons or quarks has ever been detected: if they're something other than point particles, it's yet to be determined.

And, of course, people routinely theorize about distance scales insanely smaller than 10^-21 m: string theorists and quantum-gravity people suspect that the whole concept of "length" breaks down around 10^-35 m, and like to speculate about what happens at that point. But, then again, quantum cosmologists like to think about scales way bigger than the observable universe, as well.

[Guest]

Thank you for your interesting answers. I realize now that my question was a bit naive !

This "powers of Ten" movie looks interesting. I think we could do a cel script to show the same thing than in the movie but.. in Celestia ! (of course not for the very small, but from 10^5 to 10^25... What do you think ?

[julesstoop]

If we use a space ship model we could go all the way from about 30 centimeters.

[t00fri]

Thank you for your interesting answers. I realize now that my question was a bit naive !

This "powers of Ten" movie looks interesting. I think we could do a cel script to show the same thing than in the movie but.. in Celestia ! (of course not for the very small, but from 10^5 to 10^25... What do you think ?

When you consider the average of size-scales in the Universe, then implicitly you are viewing the size-scale as a stochastic variable that is distributed in Nature according to some probability distribution:

Code: Select all

< x > = integral_0^infinity {dx x P(x)},

with

integral_0^infinity {dx P(x)} =1,


where P(x) is the normalized probability distribution and x denotes the size scales occuring in Nature. For simplicity, I assumed a continuous distribution.

The whole issue boils then down to guessing that distribution...Independence from that distribution only occurs in limiting statistical situations that don't seem to be met in your case.

Also, please note that I carefully distinguish sizes from size-scales! The size-scales set the scale for the various interactions that we know in Nature (strong, weak +_ electro-magnetic interactions & gravitation). The actual sizes of objects then arise as predictions of the theory describing those interactions, in terms of the respective size-scales.

Bye Fridger

[Guest]

Thank you for your interesting answers. I realize now that my question was a bit naive !

This "powers of Ten" movie looks interesting. I think we could do a cel script to show the same thing than in the movie but.. in Celestia ! (of course not for the very small, but from 10^5 to 10^25... What do you think ?

there it is: http://celestiamotherlode.net/creators/ ... svon10.zip