Goal: To understand the history of the universe especially the beginning Objectives: 1)To learn about the beginning of the Big bang! 2)To explore the Big bang to recombination 3)To explore Recombination until start of galaxies 4)To explore the timeline of the start of Galaxies to us 5)To examine The future 6)To learn about The end of the universe

Big Bang! The big bang was the universe starting from roughly a point. We saw some of the evidence of why we know this to be the case. We didn’t give details on the first 380,000 years though. So, lets go back in time 13.7 billion years and see what the first 5 minutes of our universe were like.

The beginning of the Universe! Time starts with the Planck Era. This “Era” lasted for the first seconds of our universe’s life (temperature was about K). Imagine our entire universe in a region of space much smaller than a proton. Note all the universe is pure energy at this point. No mass or matter – just energy. What would this be like?

Planck Era The truth is we have no idea of what happened in the first moments of our universe. Our only way to guess is by examining quantum mechanics. Quantum says that there is always an uncertainty in position. So, if there is a shift in the position of energy (and gravity is an attraction of energy) then there is a shift in gravity. So, you can get slight clumping of energy even at the start of the universe! Other than that – your guess is as good as mine.

How did it start? Again, we have no idea. There are ideas out there such as string theory (now called M theory), multiverse theory, and a few others. You are welcome to believe whatever you want in this first seconds. (Thus the Big Bang model does not overthrow religion).

The GUT Era There are 4 fundamental forces in nature: Gravity Strong Force Weak Force Electromagnetic Force During the Planck Era we think these forces were all combined into 1. During the GUT Era gravity separated itself from the other 3 forces.

Reign of GUT GUT lasted until the temperature fell below K (the temperature range that the 3 forces stay merged). This Era lasted until seconds after the Big Bang. However, we do not know much else about this era. The one thing we do have an idea of is that at the end of this era the Strong force split from the GUT force. This split would have released a lot of energy – enough to greatly expand the universe!

Need for inflation When the key economic indicators – err wait, wrong inflation. There is a slight problem with the big bang as I have stated it so far. If we look out today we see two things about the universe: It is homogeneous and isotropic. Homogeneous means is that the universe is fairly smoothly distributed and it looks pretty much the same in all directions. Isotropic means that the universe is about the same temperature everywhere. This is a problem. Tiny fluxuations (as I have told it so far) should have created a LOT of structure to the universe – a lot more than we currently see.

What is inflation? Inflation was a brief period of time ( seconds) when the universe expanded at an insane rate. This smoothed out the universe as any perturbation would have been made a lot smaller. Regions of space the size of the nucleus of an atom would have been blown up to the size of our solar system in this short timeframe!

Electroweak Era Inflation occurred during the very first part of this era. Here the electromagnetic and weak forces were still combined. This era lasted for s (leaving the temperature of the universe at K). At the end all 4 forces separated.

Contents of Electroweak era During this period we don’t yet have elements. We do have elemental particles such as quarks, electrons, and photons. However at the temperature and density of the universe at this point they would quickly collide with other particles (and antiparticles) which would turn them back into energy. This has been tested in the lab! This is the first era of the universe we can actually test the conditions of.

The Particle Era In this era photons dominated as it was still very hot (a trillion degrees at the end). This era lasted until the universe was seconds old. The photons in this era started to build to strange forms of matter such as quarks. Unlike the era before the quarks were able to survive.

Matter! These quarks formed into protons and neutrons by the end of the era. The end of the era is when the temperature was too low to make protons from pure energy. Problem: In this period you should have equal #s of quarks and anti quarks, which means equal #s of protons and anti protons. However, today we see almost all regular matter and very little anti matter – how could this be?

Not equal It is likely that while close to balance the production of matter to antimatter was slightly unbalanced for whatever reason. If we examine the # of photons we can gain an insight into the difference. If matter/anti matter were exact we would have all photons. If there were twice as many protons and anti protons then there would be 2 photons (for each pair that collides) and 1 remaining proton for each set. In our universe photons outnumber protons by a billion to 1. Therefore, there were about 1 billion and 1 protons per 1 billion anti protons. This gives us the matter that we have still today.

Era of Nucleosynthesis Before this point the temperature was so high that if protons collided that they would destroy each other, and anything bigger than a single proton really didn’t stand a chance. Once the temperatures dipped below a trillion K this was no longer the case. You can now have fusion!

What can we form? We start with all Hydrogen. Some of this fuses into Helium because of the high temperatures and densities. However, many of this is broken back down due to the same reasons. The universe is expanding and cooling. This makes the rate of fusion slow quickly. The fusion process only lasts 5 minutes.

End of Nucleosynthesis After 5 minutes temperatures were still a billion degrees, but the densities are now too low for fusion and fusion shut off. So, what is the biggest atom we have at the end of this era? A) Oxygen B) Carbon C) Iron D) none of the above

No metals We get NO metals from this era! All the metals (including the ones in our bodies) were all formed in the cores of stars in the next 13.7 billion years. We are star stuff! The resulting breakdown is: Hydrogen (90% by #, 75% mass) Helium (10% by #, 25% by mass) Trace amounts of Deuterium and Lithium (maybe some very trace amounts of Boron and Beryllium). Nothing else!

Conclusion The universe has had a very interesting history – for what we can determine. However, there is still a lot we don’t understand (and a lot of problems unsolved that I have not mentioned). This is why cosmology is one of the hot topics in astronomy currently and probably will continue to be so for at least the next decade.