Le Big Bang et Plus Loin
Est-ce que quelqu’un a joué avec les lois de la nature ?
Les Theories de l’Origin de l’Univers
• “Theories” Theleogiques:– La Mythologie Grec ( le Chaos)– L’Hinduism ( Le Sommeil Cosmique des
dieux– Le Mythe Chinois de la creation
(Pangu)– La Bible (creation en 7 jours par Dieu)
• Scientific Theories:– La Creation Continuelle– La Theorie du Big Bang – le plus
accepté
Big “Bang”
• En Realité il n’y avait pas de “bang”• En verité, les galaxies ne se pas en train
de s’écarté• La Realité: l’éspace fait une expansion!
– Quand il y plus d’éspace entre les galaxies, il s’éloignent les un des autres
– Analogie: comme des points de crayon sur un ballon gonflé
• Isaiah 45:12– …I have stretched out the heavens...– C’est le seul document ancien qui mention
un Univers en expansion.
Evidence for the Big Bang
• Theory predicts an expanding universe– Confirm by Red Shift (Doppler effect) in
spectrum
• Theory predicts cosmic background radiation– Background radiation was discovered
in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery
Et plus loin?• La Theorie du Big Bang explique comment
l’Univers a débuté mais nous laisse avec beaucoup de questions pas répondu:
• L’Espace, le Temps et la Matière ont tous été créer par le Big Bang– Avant le bang, il n y avait pas de temps, ni éspace, ni
matière– Mais la Physique n’a pas répondu a la question
“Qu’est-ce qui avait avant le Big Bang”• Si j’éntends un petit bang, je pose la question
“Qui ou quoi l’a fait”– Dabbord “Qui ou quoi a causé le Big Bang” ?
• Autres facteurs determine comment l’Univers va developé:– Montant de mattière dans l’Univers– Properties physiques de la mattiere– La puissance des forces fundamentales
Forces Fundamentales en Physique
• Force Gravitationelle– Attractive force between objects with mass– Weakest, long range
• Force Electromagnetique– Attractive and repulsive
– Long range, 1039 times stronger than gravity
• Force Nucleaire Faible – Cause neutrons to decade into a protons– Range <10-17 m, 1028 times stronger than gravity
• Force Nucleaire Fort – Hold the nucleus together– Range <10-15 m, 1041 times stronger than gravity
• Law of Gravity:
– M = mass of one object– m = mass of second object– G = 6.67 x 10-11 Nm2/kg2
– r = distance between the objects
Gravitational Force
• Coulomb Law:
– Strength of EM-force determines how strongly electrons in an atom are held in orbit
Electro-Magnetic Force
proton electron
Nuclear Weak-force
• Repelling force that cause beta-decay
neutron proton
electron (beta-particle)
The strength of the nuclear weak-force determines how fast neutrons are converted into protons and electrons
anti-neutrino
• Hold nucleus together by overcoming the repelling protons in nucleus:
– Strength of the nuclear strong-force determines how fast nuclear reactions will proceed
Nuclear Strong-force
neutron
neutronproton
proton
Thinkering with the Force...
• Fact:– The fundamental forces in nature have strength that is
determined by a number of physical constants– For example: gravitational constant in the Law of
Gravity, Coulumb constant in the Electro-magnetic force
• Question: what would happen to the Universe if the values of these physical constant were changed ?
• Say, what would happen if the gravitational (or some other) constant would be off a little bit ?– We would surely weight a bit more on Earth…BUT...– Physicists did NOT expect earth-shattering
consequences…
Precondition for Life
• Stars of the right type for sustaining life supportable planets only can occur during a certain range of ages for the universe.– stars of the right type only can form for a narrow
range of values of the gravitational constant
• Living cells consists of light and heavy elements (Hydrogen, Carbon, Oxygen, and metals such as Iron, Copper, ect)– To make both light and heavy elements, the strengths
of the fundamental forces must lie within a very narrow range of values
• Many many other preconditions exists…
Amazing Findings...
• Brandon Carter presented his ideas about the “anthropic principle” in 1973 in Poland during the 500th birthday of Copernicus
• The anthropic principle states that– All the seemingly arbitrary and unrelated constants in
physics have one strange thing in common – these are precisely the value you need if you want to have a universe capable of sustaining life
• Astronomer Fred Hoyle once said:– A commonsense interpretation of the facts suggests that a
SUPERINTELLECT has MONKEYED with physics . . . and that there are no blind forces worth speaking about in nature.
– And Fred Hoyle was an..Atheist
The strength of the Gravitational force
• If gravitational force was made a bit stronger, stars will be more massive and burn more violently and unstable:– More harmful radiation to life – deadly to life…
• If gravitational force was made a bit weaker, stars are too light and do not become super-novae:– Element heavier than iron are only formed when
stars explode as a super-novae; no life possible without them…
• If the electro-magnetic force is slightly weaker:– Too weak to hold electrons in orbits about nuclei– Universe will consists of loose protons and electrons,
no atoms, and thus no life will be possible
• If the electro-magnetic force is slightly stronger:– atom could not "share" an electron orbit with other
atoms– No chemical reactions possible and no life
The strength of the EM-force
proton electron
Strength of the Nuclear Weak-force
• If Nuclear Weak-force is made a bit stronger:– neutrons would decay more readily, and there would
be little to no neutrons left– Neutrons are necessary to form heavier elements used
in living cells – no neutrons, no heavy elements, no life.
• If Nuclear Weak-force is made a bit weaker:– Plenty of neutrons will be available – Stars can use neutrons to burn most or all of the
hydrogen into helium (and subsequently to heavy elements)
– But little or no hydrogen will be left… no hydrogen, no water, and no life…
Strength of the Nuclear Strong-force
• If Nuclear Strong-force is made a bit stronger:– Nuclear reactions will be very efficient (fast)– Most or all hydrogen will be converted to Helium and
then on into Iron– No hydrogen, no water, and thus, no life possible…
• If Nuclear Strong-force is made a bit weaker:– Force is too weak to overcome electro-magnetic
repulsion of protons in nuclei– multi-proton nuclei would not hold together– No carbon or oxygen, no proteins, no water, and thus
no life possible…
That’s just the beginning...
• Many more amazing “coincidences” that make life possible have been discovered– The composition of our sun is just right, the distance
of the Earth to the sun is just right, the size of the Earth is just right, the orbit of the Earth is just right, the size of our moon is just right and even the giant planets (Jupiter) are just right for life on Earth…
• Other amazing “coincidences” makes it possible for the stars and galaxies to form
A coincidence at nuclear scale
• The following is an account of a series of amazing “coincidences” in nature that dazed an atheist astronomer and many others
• I have to take you into nuclear Physics
• Brace for the ride – please ask questions if you don’t understand something
• Electrons can only occupy a number of specific orbits around the nucleus – each orbit represents a certain energy level
• So also, nucleus of atoms can occupy a number of specific energy levels
• In a nuclear reaction, the Law of Conservation of Energy must hold:
Nuclear Reaction
Kinetic + nuclear energy before =Kinetic + nuclear energy after
• When nuclei collide, they form a new nucleus:
• If the energy level of the new nucleus is very different from one of its natural energy state, the new nucleus is unstable and will decompose (radio-activity):
Nuclear Reaction 2
Nuclear Resonance
• If sum total of kinetic and nuclear energy before and after are very close to each other, the nuclear reaction will proceed very rapidly– In such case, we say there is “Nuclear Resonance”
• Resonance between atomic nuclei depends on:– Structure of the nuclei involved– Temperature under which the nuclear reaction takes place
• Resonance between atomic nuclei are extremely rare in nature.
• Matter are converted into energy in stars through a number of nuclear reactions
• The three primary nuclear reactions (after these, the star is almost burned up) are:
– Proton-proton cycle– Helium fusion– Carbon cycle
Nuclear Reaction in Stars
• The proton-proton cycle will burn Hydrogen into Helium (first phase of star development)
• When all Hydrogen are burned, phase 2 kicks in…
Proton-proton cycle
• After all the Hydrogen is converted to Helium, the star converts Helium to…. What ?
• Here we have a major problem...• When two Helium nuclei are fused into
Beryllium-8, the resulting Beryllium-8 isotope is highly unstable– Beryllium-8 has a half life of 10-16 seconds !!!
Helium Fusion
Helium
HeliumBeryllium-8
< 0.0000000000000001 sec
According to the physics of Beryllium-8, stars cannot burn Helium
A Stellar Mystery
• Dilemma:– According to the physical properties of Beryllium-8,
stars cannot burn beyond Helium– Yet, Helium is being converted in Carbon in stars all
the time
• First proposed solution: Triple collisionHelium
Helium
Helium
Carbon-12
Triple collisions are extremely rare and the rarity cannot explain the abundance of carbon
Ed Salpeter’s solution...
• Faced with the dilemma that stars convert Helium into Carbon at great rate, and no plausible explanation for this process, the astrophysicist Ed Salpeter proposed the following solution in 1952:
Helium
HeliumBeryllium-8
Helium
Carbon-12BUT Beryllium is extremely unstable
Fred Hoyle’s insight
• Fred Hoyle realized that the only way that Salpeter’s solution can produce Carbon at the rate that is happening in stars is:
Helium
HeliumBeryllium-8
Nuclear resonance !!!(Very fast reaction)
Helium
Carbon-12Problem: there is no known energy levelof the Carbon-12 nucleus that is nearthe sum total energy values of He and Be
Fred Hoyle’s wild guess
• So Fred Hoyle hypothesized (guessed) that there must be such a natural energy level of the Carbon-12 nucleus
• Hoyle calculated the temperature inside a large star to be about 100 million degrees
• and worked out how much kinetic energy this would give to the particles rushing around in the star's atmosphere.
• Knowing the masses of both beryllium-8 and Helium, his hypothesis predicted that there must be an excited state at an energy of 7.6 million electron volts in the nucleus Carbon-12…
• I did tell you that nuclei resonance was rare… everyone was skeptical about Hoyle’s prediction...
• A team at Cal. Tech. led by Willy Fowler (later a Nobel Prize winner) began the search for the mysterious resonant state in carbon-12, and discovered it - just 4 percent above Hoyle's prediction !!!
• We are not out of the wood yet... Heavier elements must be formed – specifically:
– You want to form Oxygen (necessary for life !)– But you want to keep some Carbon (also necessary
for life)
Yet another amazing coincidence...
Carbon-12
Helium
Oxygen-16
A missed resonance
• In order to have this nuclear reaction going:
– You need a natural energy level of Oxygen-16 close to the sum total of the energy levels of Carbon-12 and Helium
– But not too close - if the level is too close, most or all Carbon-12 will be converted, so you want this energy level to be off a bit
Carbon-12
Helium
Oxygen-16
Another “coincidence”• Well…they did find that resonance level of
Oxygen-16 and it did miss the resonance level to slow the production of Oxygen-16
• These two coincidences caused atheist atronomer Fred Hoyle to comment:
– If you wanted to produce carbon and oxygen in roughly equal quantities by stellar nucleosynthesis, these are the two basic levels you would have to fix, and your fixing would have to be just about where these levels are actually found to be....
– A commonsense interpretation of the facts suggests that a SUPERINTELLECT has MONKEYED with physics . . . and that there are no blind forces worth speaking about in nature
Flatness-oldness problem
• The following incredibly precise tweaking of the Universe is known as the Flatness-oldness problem
• The amount of matter created in the Big Bang has a profound impact on how the Universe will develop– Matter attract and will pull the Universe back together
towards one point– There is a critical amount where the attraction will halt
the expansion and the Universe will slow down and stop expanding
– If the total mass in the Universe is less than critical, the Universe will keep expanding
– If the total mass in the Universe is more than critical, the Universe will stop expanding and contract (Big Crunch)
• Suppose X represents the critical mass of the Universe, what do you think that the total of mass of the Universe is ?
• There are so many possible values to pick from for the total mass of the Universe– An does it matter how much mass there is in the
Universe ?? (You will be amazed by the results)
Place your bet...
0 X
Some results from Theoretic Physics
Interpretations of the results• IF the density of the matter after 1 nsec from the Big
Bang is equal to 447,225,917,218,507,401,284,017 mg/cc, the Universe would have collapsed by now.
• IF the density of the matter after 1 nsec from the Big Bang is equal to 447,225,917,218,507,401,284,015 mg/cc, the Universe expands so rapidly that galaxies and stars cannot form.
• To get the (flat) Universe in which we (probably) live in, the density of the matter after 1 nsec from the Big Bang must be equal to 447,225,917,218,507,401,284,016 mg/cc – not one gm more nor one gm less
• No wonder than many scientists believe that, the Universe was designed
And there is much more...
• There are many more examples of coincidences in nature without which life could not have developed
• Science has coined a term to describe these strange “coincidences”: Anthropic Principle (The Universe is “destined” to support (human) life)
• For more examples:– http://cheungpc.mathcs.emory.edu
(Not) The End
(just out of time…)
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