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Falling through Matter
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Question:
I am a biology student at the University of Washington and I have
three questions which have been puzzling me for some time. 1. If I press my
hand down upon a table, why does not it fall through? Does it have to do with
molecules colliding or electrostatic interactions? What if I could shrink
an object so that it could fit in the "spaces" between atoms? Would it then
fall through? Textbooks illustrate atoms as solid spheres for ease I have been
told. There are suppose to be electron "clouds" around the nucleus. If so
how come these spaces are not seen? 2. How does electricity work? So what if
there are a bunch of electrons moving and generating a current? How does t
this translate into something that powers my toaster? 3. How do laundry
dryer sheets prevent static "cling"? I would really appreciate any
answers. Thanks.
Replies:
I can try to answer first two questions.
1. When you try to press your hand upon the table, the electron
clouds of atoms in your hands interact with electrons of atoms
in the table. There is a law of nature which prevents two electrons
from being in the same state, it is known as the Pauli exclusion
principle. For this reason, the electron clouds of different
atoms repel each other and it takes a lot of energy to overcome
this force. Atoms are incessantly vibrating and colliding with
one another, so the "space" between them is not "empty" in the
usual sense.
2. When electrons move through simple gadgets like a toaster or
an electric bulb, the work is being done by the heat generated
from collisions of electrons with nuclei in the filament. For
more complicated equipment, various other laws of atomic and
material science are used to produce the end result. For example
there are things like a diode which will let current pass in only
one direction. A combination of such elements produces the result
you see.
jasjeet s bagla
As Jasjeet says, in spite of atoms being mostly "empty space",
it takes an awful lot of energy to squish atoms together
closer than they would normally like to be, because to do
that means distorting the shape of those electron 'clouds',
and electrons really HATE that... in fact, the energy unit
usually used to describe distortion of electron orbitals
is the electron-Volt (the energy gained by an electron in
an electric potential with a one volt drop). Translated into
ordinary temperature terms, one electron Volt is equivalent to
about 11,000 degrees C. You would have to be pressing your hand
REAL hard to generate temperatures that high (and you would probably
do structural damage to the table first...)
I also do not know how those dryer sheets work... I assume they
act in some way that removes any charge accumulation on materials
they come in contact with, so perhaps they can conduct electricity
reasonably well? But that is just a guess!
Arthur Smith
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Update: June 2012
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