Science myths
These are stories about Science: the myths of our time. The myth
has an important role in the society : these stories have made Science
a part of the collective consciousness.Let's be honest:the true appreciation
of scientific ideas requires hard work; there is no royal way to Science.
But these stories,that can be appreciated by anyone,may help to make
Science an integral part of our culture.
Archimedes was a near relation of Hieron the King of
Syracuse. He said the famous sentence:GIVE ME A PLACE TO STAND AND I
WILL MOVE THE EARTH
meaning that with a proper lever he could move any load.He demonstrated
this
by moving alone a big ship.
But the most famous story about Archimedes is how he was able to
demonstrate
to Hieron that a goldsmith had replaced some of the gold in a
commissioned
crown with cheaper silver. He put into a bowl filled with water to the
brim
a weight of silver and then a weight of gold equal to the crown.
He measured how much water was spilled in the two cases, then he put
the crown and found that the water collected in this case was between
the
two previous measures.
This solution occurred when he stepped into his bath and caused it
to overflow.So delighted was Archimedes with his solution that he leaped
from his bath and ran through the streets of Syracuse crying "Eureka!"
Where does the apparently infinite energy from the Sun and other stars come
from? What is the fuel of the stellar engine? Hans Bethe(Physics Nobel Prize 1967[10]) explained
that the energy came from the fusion of four hydrogen atoms into a helium atom.
The missing mass is converted in the flow of energy coming from the Sun.
In fact,when a mass of hydrogen enough big forms in the sky, the gravity in
the core will become so strong that the "engine" ignites and the star starts
producing energy.This is the same principle of the H bomb, where the function
of the gravity in a star is taken from a A-bomb that exploding, will compress
the Hydrogen core enough starting the fusion reaction.
The Big Bang is ,of course, the starting of the Universe from a single
point in space around 15 billions of years ago(but at the beginning
space and time don't themselves exist). Black holes are created when
a star with enough matter ends its nuclear fuel and collapses unto itself
becoming a single point in space. In some way the forming of a black hole
is like a Big Bang in reverse. The two terms have made two rather abstruse
scientific concepts immensely popular.
The Big Bang model was put forward by belgian
astronomer Georges Lemaitre to explain
why galaxies seem to travel away from our galaxy with a speed directly
proportional to distance. If you reverse this motion in time you come to
the obvious conclusion that the whole Universe has started sometime in
the past with a great explosion that is still continuing . Lemaitre
said that everything started from a primeval atom. This model
somewhat reminds the Genesis description of the world creation by
God. What is ironic is that Lemaitre was indeed a roman catholic priest
who, of course, knew very well the biblical story. The idea wasn't well
received by other scientists. The term "Big Bang" itself was coined by
the most important adversary: Fred Hoyle , to mock Lemaitre. Lemaitre
had his revenge
a few years later when the discovery of the "Cosmic Background
Radiation"
definitively proved his hypothesis. This radiation is the remnant heat
of the
initial explotion and can be found everywhere. Just to understand , it
was
like finding the ashes from a camp fire. Not only it
proved the initial explosion, but from its temperature an approximate
time of this "Fiat Lux" instant was computed.
The Universe is Infinite and contains an infinite number
of worlds and these are all inhabited by intelligent beings. This was
the idea that hit Giordano
Bruno in a time when the Earth was considered the center of the World .
We can't say that Bruno was a scientist but this single idea and the
fact
that he probably was burned at the stake for it has made him a martyr of
Science.
It was well known at the beginning of XX century, since
many years, that atoms behaved like radio stations.
They transmitted only on a fixed set of frequencies. The only difference
was that
the electromagnetic waves used to transmit were in the visible spectrum.
To turn an atom in a radio station you have to heat the material
containing the atom: then you will
see some colors caracteristic of the element (this is how fireworks
work). This behaviour is so reliable that
these same frequencies can be found in the light of stars (in this case
like
small black lines, because they are due to the atoms in the stellar
atmosphere
absorbing the light in the same frequencies where they transmit).
When the young Bohr started to study this phenomenon, he had some
additional
information available. Atoms had a very small nucleus in the center
surrounded
by a cloud of electrons. He had the following surprising intuition:
nucleus =
the sun, electrons = the planets rotating around the sun. The electrons
move in fixed trajectories. When light hits the atom, it is absorbed
only if its energy
(and frequency) is such that it can raise the electron to an higher
trajectory. The same light is emitted when the electron returns to the
previous trajectory. The intuition was right but the complete
explanation of the strange atom behaviour came only ten years later and
required the development on a entirely new physics : the quantum
mechanics.
What happens when a star has burnt all its supply of hydrogen? As Chandrasekhar,
a physicist winner of the 1983 Nobel prize[10]
discovered, it
all depends on the size.With a size below the Chandrasekhar limit the
star
will collapse becoming a white dwarf. Just imagine the Sun becoming
small like
Earth and also getting colder and colder:not very interesting. With a
mass bigger than 1.44 that of the Sun(this is the Chandrasekhar limit)
something incredible happens.
The star will literally blow up its gaseous envelope with a supernova
explosion
and the core of the star will collapse to the center becoming something
so compressed that a few kilometers of radius contain all the star
material.
This is the neutron star that usually is spinning very fast and can be
dectected
from Earth as a pulsar:a kind of cosmic clock. But the really fantastic
thing
happens with sizes even bigger: in this case the supernova remains will
collapse
in a Black Hole:all the mass confined in a single point!
Well,Columbus wasn't the first to believe that Earth is round.
The greek Eratosthenes,more than 16 centuries before, assuming that Earth was
round made a surprisingly accurate
estimate of the earth's circumference!
To know more [8]
E=mc2 is the unique mathematical expression of a physical law
entered in the collective consciousness.In a explosive way, when the first
atomic bomb exploded in 1945 transforming few grams of matter in a blast
that destroyed a city.Einstein wasn't part of the project Manhattan
that built the bomb although a letter written by him to the Usa president
perhaps had some influence on the start of the project. Instead the famous
formula was the result of the so called special relativity theory
created by Einstein at the beginning of the century. Then Einstein wasn't
thinking about atomic bombs but only about the curious fact that the light
speed (the c in the formula is the light's speed) was the same
no matter how fast you were moving.
Building an atomic bomb is extremely simple if you have enough Uranium of the
"right type". You put it toghether until at some "critical quantity" it explodes.
This is the "chain reaction". Enrico Fermi did know well the theory, but
until someone tried it , this was only a theory. Altough the atomic bomb
was built in Los Alamos and other centers with huge expenses of resources, its
feasibility was demonstrated by a simple experiment carried out by Fermi
and a group of other scientists in a squash court of the University of Chicago. They assembled toghether
enough uranium that could start the chain reaction.In order not to be
blown away by a sudden explosion, but to control it, he used a lot
of graphite and some cadmium rods that could be used to have a fast
control by inserting them among the uranium.
Fermi was in fact able to start the chain reaction and to control it
(not obvious).The famous sentence was a code to inform about the
success of the experiment .
During a discussion with other physicists on the possibility of extra-terrestrial
intelligent life, Fermi made this famous remark. There are billions of galaxies,
each galaxy has billions of stars like our Sun. So there should be billions
of planets like Earth where intelligent life could have developed.
Where are these extraterrestrial intelligent beings? Why we don't have
any proof of their existence? Why they don't contact us?
It is true that distances in the Universe are very big and make communications
and space travel almost impossible. But you can assume that, as the science
progresses , more and more extrasolar planets should be contacted by an
extraterrestrial intelligence. So what is the solution of the Fermi
paradox? It is possible that all life forms after some level of intelligence
destroy themselves before they can reach their neighbors?
"And yet it (Earth) does move" .
Almost certainly Galileo never said this famous sentence.
Galileo Galilei published his Dialogue on the two chief world systems
in Florence in 1632 with the Church approvation. But shortly after the publication
he was summoned by the Holy Office to Rome. He was condemned and forced to a
abjure of his theory. During these events Galileo was over sixty years old
and in bad health conditions. He made no opposition at all to the Church tribunal.
To know more:[4]
Luigi Galvani was an Italian physician . Dissecting a
frog with a metal scalpel he noticed a movement in the dead frog legs.
His conclusions were that the frog had some sort of inner electricity.
His contemporary physicist Alessandro Volta
understood instead what was really going on. It was the scalpel to have
generated an electric current in the frog's leg nerve thus generating
the movement. Following his intuition he started experimenting with
metals
without frogs, thus discovering that it was enough to use two different
metals
to produce a (very small) current. To increase the current produced he
put
many metal discs in a pile alternating zinc with silver thus building
the first electric battery.
According to the classical Physics , electrons,
being attracted by the nucleus of the atom, should fall inside it and so
all matter should collapse.
Heisenberg was the first to explain why this doesn't happen and the
matter is
solid. The answer was in his famous indetermination principle that can
be "explained" in this way.
The electrons have a kind of "vibration" that increases as we force them
in a smaller space and the nucleus is so small that there is no way to
force them there
unless we use a very big force.
It is as if we have a few people around in a room : they will move
around doing
something. If the room get smaller the same people will move more and
more and
this creates a kind of pression that forbids at some point to the room
to became smaller.This jitter motion of electrons is sometime called
zitterbewegung and arises from attempting to localize the particle or from interaction of the particle with potential(a force).
Scientific discoveries are made in dreams? Kekulé was trying to
understand what was the form of the benzene molecule: he had a dream about
a snake biting its queue. After the dream he solved the puzzle:the six
carbon atoms formed an hexagon thus a closed form like the snake of the
dream.
Leonardo da Vinci (1452-1514)famous Italian Renaissance artist and engineer.
He left notebooks full of drawings of engines. Many of these engines were
built only centuries after his death.Before the birth of modern science he
shows through his writings a spirit of scientific inquiry well ahead of his
time.
To know more:[9]
Edward Lorenz was trying to model the weather with a
simple set of equations. The program was run on a computer and in one
of the runs he wrote by mistake
a number with three decimal places instead of six.To his greatest
surprise
the results were completely different.He has discovered in fact
deterninistic
chaos: i.e. there are phenomena, like weather, that are impossible to
forecast
not because are complex(this is the case of dice throwing) but because a
tiny change of the initial conditions can change completely the final
outcome.
In 1871 the physicist James Clerck Maxwell proposed the
following thought experiment. Put a trapdoor on the
wall separating two compartments in a box.
The box is filled with gas molecules. There are molecules going at all speeds.
If we could separate fast molecules in a compartment we would end with a hot
gas on one side and a cold gas on the other side. Maxwell proposed to put
an intelligent device on the trapdoor (the famous demon) that would decide
for each molecule hitting the door if the door should be opened or not.
To know more:[7]
As soon as man invented numbers, he started to put them in tables. Doing so
he would discover that some phenomena would repeat themselves again and again.
Perhaps the first table was the Calendar. The fact that comets return
periodically was also discovered by Halley from a table of comet observations.
But of course the most famous table is the one by Mendeleev. He was able
with his table to discover three new elements. Only with the discovery of
quantum mechanics and with the Pauli principle there was at last
a complete explanation of why the elements would form such ordered table.
The last tables in Science were the tables of elementary particles. By thinking
about them the quark was discovered. The quarks themselves with
the so called leptons form another table up to now unexplained.
Looking an apple falling from a tree,Newton asked himself why the Moon doesn't
fall toward the Earth like an apple.
The Nobel prize started at the beginning of this century
created from Alfred
Nobel ,the inventor of dynamite. Among scientists only mathematicians
don't
receive the prize. The story goes that,when Alfred started the prize,
the
mathematician that most likely would receive the first Nobel, was
Mittag-Leffler also from Sweden ,the lover of Mrs. Nobel. This has been
proven to be a legend.
[5],[11]
The building of the bomb is an extrahordinary story. Thousands of scientists
working toghether in a remote place in the New Mexico mountains.
Physicist Robert Oppenheimer was in charge of all these scientists (among
them many Nobel laureates)
that formed the Manhattan Project.
The first test in the desert and then this mushroom of fire.It was
July 15, 1945 and the world would never be the same.
At the level of basic components matter is very simple.
Electrons are all perfect twins, all absolutely equal. The same is for
other elementary constituents
of matter and radiation. Pauli asked himself: can we put two particles
in the
same place?The answer he found was that it depends... Electrons have to
stay
all in different places:they form the solid matter of everyday life.
Instead
other particles like light photons prefer to stay in the same place!(In
fact
a laser is just a bunch of photons staying all in the same place).
The first kind of particles are called fermions, the other ,the
gregarious ones, bosons. Looking in more details in the fermions,
the solitary ones, Pauli discovered that two or more electrons can stay
in the same place only if they have some other quantity which is different.
These quantities are called in scientific jargon quantum numbers.
So,if we look for example at the 92 electrons in the Uranium atoms, they
have all different quantum numbers. So the Pauli exclusion principle:
explains the Mendeleev's table.
A cat is placed in a closed box together with a radioactive material,a Geiger counter
and a device that,once we have the first atom disintegration, will break
a bottle with a poisonous gas(prussic acid). We know that there is a 50% of
probability that an atom of the substance will disintegrate in the next
hour. Before the observer opens the
box after an hour to see what happened, the atom is described in quantum mechanics by saying that
it is a mixture of the decayed and undecayed states.(This
superposition is the way we describe quantum systems.) But what about
the cat? Should we say that,before we open the box,also the cat is a mixture
of the dead and the alive states?
This paradox was exposed by Schrödinger to Einstein in a letter written
in 1935.
To know more:[6]
Related material on Internet:
- Moldy Oldies
- Archimedes home page
- Albert Einstein Online
- Galileo Galilei in the History of Science Museum in Florence
- Urban Legends Archive
- Playing
with Schroedinger's cat
- What is a maxwellian demon
- Eratosthenes experiment
- Yahoo:Leonardo
- Nobel prizes
- Why is there no Nobel Prize in Mathematics?
Other interesting links:
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