# (Largest we can see-Smallest we can see)/2=radius of Earth!

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Hi,

The midway point between the largest thing we can see (looking straight outward this is the radius of the visible universe) and the smallest thing we can see (an atom) comes out to equal exactly the radius of earth!

median(the radius of the visible universe, size of a carbon atom)=radius of earth

median(14,284,800,000,000,000,000m, 10-10m)= 20,518,481m

I think that's as weird as it is stupid, LOL!

Rusty

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An atom is not the smallest thing we can see, though. We can't see it really, we can observe it using instruments -- and if that's our criteria, then we should go smaller.

Inside the atom there's a nucleus which is MUCH smaller than the atom itself and electrons, which are even smaller.

If you don't go by what we "see" but what we know of to be the smallest length, that would be Planck Length.

~moo

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An atom is not the smallest thing we can see, though. We can't see it really, we can observe it using instruments -- and if that's our criteria, then we should go smaller.

Inside the atom there's a nucleus which is MUCH smaller than the atom itself and electrons, which are even smaller.

If you don't go by what we "see" but what we know of to be the smallest length, that would be Planck Length.

~moo

Hi mooeypoo,

No... I'm talking about actually 'see' using current technology. http://en.dogeno.us/2009/09/first-captured-image-of-electron-clouds-inside-one-atom/

Edit: I tried plugging in the size of the nucleus, protons, quarks/electrons, planck length/strings... nothing exciting.

Edit: How embarrassing!! My spread sheet has a huge error in it regarding the radius of the visible universe!

Edited by rrw4rusty

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The meaning of "see" gets kind of fuzzy down there, though. If you "see" the atom, you are seeing the shape of the electron cloud, so aren't you seeing the electrons? Really, aren't photons the only things you actually "see?" So the "smallest thing you can see" is just a photon of violet light, it being the shortest wavelength the human eye can detect. (And the biggest would just be photon of red light.) But are we limited to human eyes? I guess not, since you certainly can't see individual carbon atoms with the naked eye.

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Yeah, you can't get the median with only two numbers, can you? Also, isn't the radius of the observable universe 46.5 billion light years = 4.4 × 1026 meters?

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I assume he meant geometric mean rather than median.

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The meaning of "see" gets kind of fuzzy down there, though. If you "see" the atom, you are seeing the shape of the electron cloud, so aren't you seeing the electrons? Really, aren't photons the only things you actually "see?" So the "smallest thing you can see" is just a photon of violet light, it being the shortest wavelength the human eye can detect. (And the biggest would just be photon of red light.) But are we limited to human eyes? I guess not, since you certainly can't see individual carbon atoms with the naked eye.

How is a single photon visible then? Like when an LED power indicator light is made to pulse once, would that be a single photon?

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How is a single photon visible then? Like when an LED power indicator light is made to pulse once, would that be a single photon?

No, not by a large margin. One photon of visible light has about 2 electron Volts of energy. This represents more than 10^18 photon per second per Watt of power. Even light source emitting a nanoWatt of power is emitting a billion photons per second. If you're a meter away, that's still 10,000 photons per cm^2 of surface area. That's near the limit of what we can see with the naked eye (of order 1,000 photons/cm^ sec YMMV)

Single-photon detection is done with instrumentation.