Can someone explain the first few moments of the big bang?

Question

what is weak force and strong force?

Answer 1

Well, conjecture is that the big bang occurred, and that for a brief time, the expansion was *faster* than the speed of light. In a very short amount of time, the universe went from a point the size of an atom to a volume of about the orbit of Mercury. The density of particles and the temperature in this mass was incredible - and, it was completely black... no photons had yet formed.

Answer 2

this may take a while, and im going to assume u know what protons and neutrons are.

first, lets start with the 4 forces:

electromagnetism - acts between any charged particles. like charges repel, opposite charges attract. its mediated by the photon.

gravity - all mass attracts other mass in a way that is proportional to the two masses, and inversely proportional to the distance. so the more massive the stronger gravity, the farther away the weaker the gravity. gravity is either the warping of space-time in the presence of mass, or the contraction of a spring-like structure of particles called gravitons.

strong nuclear force - protons and neutrons are made of particles called quarks, up quarks and down quarks to be specific. up quarks have a charge of +2/3 and down have a charge of -1/3. a proton has 2 up quarks and 1 down, giving it an overall positive charge. now, if electromagnetism was the only force at work, the proton should rip itself apart due to the repulsion between the 2 up quarks. the strong force is what holds the quarks in a proton together, and is indirectly responsible for holding the nucleus of all atoms together. it is mediated by a particle called the gluon.

weak nuclear force - this is a little harder to explain. before i start id better explain that the weak force is mediated by 3 particles, the W+, W-, and Z bosons. the weak force controls the decay of particles, specifically beta decay. ill give an example: a neutron emitting an electron and a neutrino, and turning into a proton. the actual equation is a down quark decaying into an up quark and a W- boson, which then decays into an electron and a neutrino. basically, the weak force controls that decay.

now it gets interesting:

quantum gravity - progress has been made in attempting to unify those 4 forces. at fairly high energies electromagnetism and the weak force unify to create the electroweak force. scientists hope that at even higher energies the electroweak force would merge with the strong force to create the electronuclear force. that is the goal of grand unified theories (GUT). other theories, called theories of everything (ToE) attempt to unify gravity with the electronuclear force, creating what scientists refer to as quantum gravity. how does this fit into the big bang?

directly after the big bang the four forces were unified in one super force, quantum gravity. after 10^-43 seconds (thats a decimal, followed by 43 zeros, and then a 1. very tiny) gravity split off from this force and there were 2 forces, gravity and the electronuclear force. 10^-36 seconds after the big bang the strong force splits off, now there is gravity, the strong force, and the electroweak force. 10^-12 seconds after the big bang the electromagnetic force and the weak force seperate, and we have the forces we do today.

after 10-6 seconds quarks and electrons are given mass via the higgs mechanism (too much to explain here, ask another question about that). a second after the big bang its cool enough for the strong force to bond quarks together to form hadrons, such as protons and neutrons. well skip some more technical stuff, like hadron and lepton epochs, and get to the important stuff. 3 - 20 minutes after the big bang atomic nuclei form in the process of fusion. 240,000 to 310,000 years after the big bang electrons begin to orbit nuclei, forming the first atoms. in that huge gap of time there was just a haze of particles to dense for light to escape.

and that is the long, yet shortened and simplified, version of the beginning of the universe to the formation of atoms.

Answer 3

Kindof funny how one can't just look it up.

Answer 4

Steven Weinberg can, here is his book.  It is rather technical, much about sub-atomic particles.  If you don't know what strong and weak forces are, you will be lost.

Answer 5

Wow.  I am presently reading books that take entire chapters to explain this to students who already have the physics prerequisites.

Like pages and pages.

And even then, it is not always clear or easy to understand.

The Strong Force is the force that keeps the quarks together.  It is mediated by a boson (a type of particle) called a gluon.  All hadrons (including protons and neutrons) are formed from the combinations of quarks, through the "color charge"  (a kind of charge that is neither electrical, nor magnetic, hence the need for a different name).

The Strong force only acts over a short range (approximately limited to the size of an atomic nucleus).

The weak force is... well, weaker (0.0000000000001 times the Strong Force).  It is mediated by the W and Z bosons.  It is responsible for the emission of a neutrino whenever a beta decay event occurs.

It is also, of course, responsible for the (very rare) absorption of neutrinos by some atomic nuclei, in detector.  Because the boson particles responsible for it are even more massive than the gluons, their range is even less:  neutrinos can pass through the inside of atomic nuclei and still be outside the range.

In the first seconds of the big bang, the average energy of each quantum correspond directly to the "temperature".  The biggest particles were created first and these would have been the bosons (Higgs?  Z, W , then gluons...)  All this within the first second.  Then, near the end of the first second, you get the heaviest quarks, then the other quarks (immediately caught together by the gluons) and the leptons (e.g., neutrinos and electrons).  Protons and neutrons would have been formed.

The pressure and temperature were still such that these particles were rammed together sufficiently to fuse into heavier nuclei.  Mostly hydrogen, deuterium helium, Lithium and a pinch of other stuff.  By the time we reach 3 minutes into the expansion, it is now too cold for anything else.  For the "metals" (including Carbon, Nitrogen Oxygen, etc.) we'll have to wait for the first generation of stars to process the lighter elements and fuse them, then reject the by-products back into the interstellar environment.

Answer 6

The weak force is used to change quark type. For example, an up quark can be turned into a down quark plus a W+ boson, which then decays into a positron and an electron-neutrino. This is an example of the weak force.

The strong force is a force which binds all quark types together, within the nucleus. The strong force between two quarks (a meson) increases as the distance between the quarks increases, like a spring- this is called quark confinement and means no lone quarks can escape.

In the (post-inflation) early stages of the big bang, the temperatures were hot enough that particles were energetic enough for the strong and electro-weak forces to become effectively the same (grand unified theory) force- this is still a theory.

The range of the strong and weak forces are limited by quark confinement and the large mass of the W and Z bosons, but at high enough temperatures these range restrictions are lifted- it is believed at at these temperatures, the forces act the same and can be unified, using two more force propagators with energies of about a thousand trillion GeV- these could have been present just after the big bang.

when the temperature dropped, these heavy force propoagators could no longer be produced in collisions, so the force interaction cross sections (effective force) at large ranges of the strong force were reduced, and the strong and electro-weak forces became distinguishable.

At even lower temperatures, below 100GeV, the weak force propagators could no longer be prouced, and the weak interactions began to rely on virtual W and Z bosons, which had severe range restrictions. This lead to a distinction between the electromagnetic force and the weak force.

Currently we have all three of these forces acting in their own ways, but it is believed that at high enough energies, they can be unified to act together like one single force.

Answer 7

Sorry Raymond, I meant to click the thumbs up but hit the down instead.  Good answer.