Little Bang, Big Boom!

During the first half of the twentieth century, two theories of our cosmic origin were gaining popularity among scientists.  The first theory, originally proposed by Fred Hoyle, was that of a steady state universe: one that had always existed and would forever exist, unchanged.  The other theory was first proposed by Georges Lemaître who called his idea the "hypothesis of the primeval atom."  Using results of Einstein's newly developed theory of relativity,  Lemaître suggested that the universe was born as the result of a singular, highly explosive moment when time began.  Ironically, the latter theory was named by Hoyle, who jokingly made reference to the "big bang" during a radio interview in the 1940's.  The name stuck, and we now know the Big Bang theory to be the prevailing cosmological model today.  Sorry if I spoiled it for you, but today's refined model of the theory is no longer in contention (by the scientific community, at least).  Let me show you why.


Understandably, the origin of the universe became a popular scientific endeavor.  It was three gifted theoreticians, George Gamow, Ralph Alpher, and Robert Herman, who discovered a critical consequence of the big bang model of cosmology: that if such an explosion had taken place, there should a faint afterglow of thermal radiation still detectable today due to a temperature they pegged at about 9 or 10 Kelvin.  


The next big thing happened in the 1960's when two Bell Labs physicists, Arno Penzias and Robert Wilson, attempted to map hydrogen emissions within our own solar system.  Since emissions would be faint, it was necessary that any background noise be eliminated from their equipment.  After painstakingly trying to remove a constant background hiss, the gentlemen concluded it was simply a condition of the sky itself, since it appeared equally in all directions.  It was only after discourse with other physicists that the pair realized they had found the elusive relic radiation called the Cosmic Microwave Background Radiation (CMBR).  So, not only did they mistakenly discover the the key to an explosive moment at the beginning of time, the pair also accidentally won the Nobel Prize in 1978. #Prettysweetdealforthosetwo.


The Cosmic Microwave Background was, perhaps, the discovery that catapulted modern cosmology into a precision science.  Now having collected data from more than a few missions (COBE, WMAP, and, most recently, Planck, to name a few) cosmologists have been able to begin building an understanding our cosmic origins.




Let's paint a picture of the infant universe:

In early theories of the big bang, it was believed that the distribution of matter and energy should be chunky.  This makes sense, right?  Explosions we see on earth are chaotic and result in a non-uniform distribution of mass.  The problem is, pictures of the CMB show us a relatively isotropic universe. 


See?

Image from WMAP

Okay, so there are a few cold spots, but the universe is just too uniform to be explained by a single burst.  The solution: inflation.  We now believe that the universe was born in a smaller bang and then experienced an intense period of expansion we call inflation.  I think it's important to mention that the physics under which our universe exists today may not have dictated the instant of our birth.  I say instant because everything, the bang and the beginning of inflation until its end, quite literally happened in a blink of an eye.  Here's a timeline:

I found this here. 

In my human perception of time, I estimate that inflation lasted about one fiftieth of an instant, and it was likely the most intense sub instant our universe has ever seen.  This is why I propose we rename the big bang theory Little Bang, Big Boom!.  Who's in?!


Getting back to it: this altered theory describes the pretty picture imaged by WMAP.  It was the initial (little) bang that spread out matter and energy ever so slightly, while the second (big) boom effectively distributed the material into the relatively homogeneous universe we see today.  Ta da!


Anyway, the above visual doesn't show it, but it was really hot back then.  It also fails to show you the ingredients of quark soup.  Let me tell you:  

• Separation of the weak nuclear and electromagnetic forces.
• Antimatter/matter annihilation -- leaving more matter .  Obviously (look around you). 

That completes my understanding of the first second ever.

Now here's the part we care about in the current second:

As the universe continued to expand, it cooled to a temperature (3000 K) that would finally allow nucleosynthesis to happen.  This means that all those excess electrons which had roamed free for a second would combine with those free protons to form hydrogen.  We call this recombination.  Although the name would imply otherwise, this was actually the first time this process had ever happened (in this universe...).   These indivisibles (atoms were named by Democritus, you know) are important because suddenly photons could travel through swarms of them without getting stuck or absorbed.  The fog had lifted.  Literally.  The universe was opaque until recombination took place.  Consequently, CMBR is the earliest light we can detect.  


Don't feel left out; you can see it too!  In fact you probably already have.  You know when your television loses signal and the screen becomes all fuzzy?  Well, some small percentage of that snow is actually the CMB.  

I mentioned a few missions that have played key roles in our understanding of this remnant light.  The first was the COsmic Background Explorer (COBE).  The driving force behind this project was John Mather.  He, along with another key player, George Smoot, actually won the 2006 Nobel Prize in Physics for their roles in examining the cosmic microwave background.  The mission launched in 1989 and after only nine minutes of observation, COBE had registered a perfect blackbody spectrum corresponding to a temperature 2.7 degrees above absolute zero.  This explains why we detect the CMBR in the microwave region of the spectrum: the lower the temperature, the longer the peak wavelength of the spectrum.  

COBE meant a lot for cosmology because one experimental aspect (led by Smoot) sought to map the slight fluctuations in the temperature of the background.  Smoot's hypothesis was that should these anisotropies exist, studying them could help us understand the formation of stars and galaxies by illustrating where matter began to aggregate. If matter were to accumulate, it would only be a matter of time before gravity would take over to form the systems we study today.  We think these ripples are cosmological keys, and, since COBE was actually only precise enough to measure the larger fluctuations, we have continued to study these anisotropies with better technology and greater depth.  


In the late nineties an instrument called BOOMERANG flew around Antarctica on the back of a stratospheric balloon.  Its mission was to map a much smaller portion of the sky with great precision.  Another fun balloon mission was MAXIMA which, like BOOMERANG, explored a much smaller angular range than COBE.  


Next came the Wilkinson Microwave Anisotropy Probe.  Believe it or not, you know WMAP.  This is the mission from which we get the age of our universe: 13.7 billion years.  WMAP is also responsible for telling us the geometry of space: it's Euclidean.  That is to say, as far as we can see space is flat.  Clearly the Wilkinson Microwave Anisotropy Probe was a fantastically successful instrument, and I think Science magazine sums it up nicely,  "lingering doubts about the existence of dark energy and the composition of the universe dissolved when the WMAP satellite took the most detailed picture ever of the cosmic microwave background (CMB)." - Science Magazine 2003, "Breakthrough of the Year" article.  

The most recent exploration of the CMB is the Planck mission, a European Space Agency project (with many partners, like NASA) that launched in March 2009.  This probe, now retired, sits at the second la grange point about 930,000 miles away (so, like us, it orbits the sun).  You can read a little about Planck's discoveries here, although they've only just begun sifting through all the data the instrument delivered.  


Our little world and the universe are so intertwined in ways we don't even know (or sometimes acknowledge).  I think its incredible that humans, who've only been around for a few thousand years, can actually study 13.7 billion years into the past and appreciate its importance.