bright light, a time machine and sun glasses

I've seen two episodes of the new version of Cosmos so far.  I was going to wait a bit longer before commenting, but something came up.

 

It is remarkable to see a show on current science on an American TV network during prime time.  Finding the right level for something like this is approximately difficult.  I have a few criticisms, but I'm not the intended audience.  What really matters is what pre-teens think. Everyone I know who went on to the Ph.D. level was hooked at an early age - Neil deGrasse Tyson likes to say he was called by Nature.  The original Cosmos inspired a generation of scientists, hopefully this will do the same.

 

So far I'm mostly happy.  I find Neil a superb communicator and Ann Druyan to have good storytelling instincts honed in the original series.   The evolution of the eye in the second episode was particularly well done and hopefully should spark a few imaginations.   I wasn't as happy with some of the animations of the solar system, but bringing in the excitement about Europa seems exactly right.  

 

Unfortunately the Big Bang was presented as an explosion ...  like so many other shows, books and textbooks.  Inflation is briefly mentioned, but there was a lot of artistic license to make the story flow.  Perhaps it would be overwhelming to go into modern cosmology ...  there are limits to how much you should present ... but oh what a story!

 

That brings me to why I'm writing this.  Last Monday something rather dramatic was announced.  If I was to list discoveries in physics and astrophysics since I was an undergrad, this will be in the top three or four if confirmed.  

 

I started hearing about it via twitter the Friday before.  

BICEP2 is announcing something big at CfA.  

Over the weekend rumors were spreading over the 'net - twitter, blog speculation, emails.  By Sunday afternoon it was clear I had to be in a place with others who are dying of curiosity. 

r  strong and > 0.1,

Just enough to excite the folks who have been following this over the years.  Was there finally a breakthrough and, if so, how big?  Then, almost out of the blue, a result.   BICEP2 was a very difficult experiment that people thought would take many more years of improvement and analysis before delivering a result - a result that would be the whisperings of Nature rather than what many hoped for. I was having a difficult time focusing on Cosmos - something much better than Christmas may be just around the corner after all.

 

I woke up at 3:30a too excited to stay in bed and check for emails as well as my twitter feed.  An email from a friend of a friend who would have direct knowledge said r = 0.20 ^+0.07 _-0.05 in the subject line and  "5 sigma" followed by an exclamation mark and a smiley emoticon in the body.  The stunning kind of message that takes your breath away.  I decided I needed to watch a feed of the announcement with others at Princeton and sent an email backing out of a conference call.  

 

Most of you are probably wondering what is going on and why I was more excited about it than confirmation of the Higgs field and so much else.   To get there we need a time machine and sun glasses ...

 

By the late 1970s some fundamental physics was coming together to explain pieces of the early history of the Universe.  It became possible to probe down to the first few minutes after the Big Bang and a good deal of the evolution from that period was also coming together.  Theories of earlier periods were being advanced and tested in particle accelerators - an indirect probe of the extremely high temperatures found in the early Universe.  Particle physics had become linked with astrophysics and cosmology.

 

Interesting conjectures about the very early evolution soon after the Big Bang emerged.  Physicists would extrapolate the results of General Relativity backwards and try and square that with Quantum Mechanics, but it was mixing oil and water.  The two extremely successful theories were limited to their own non-overlapping domains.  A hope existed, and continues, that there is a deeper theory. Hope isn't enough - Nature doesn't respect human desires.

 

In 1979 Alan Guth was working on  problems with models explaining why the Universe is so uniform and why it appears to keep expanding rather than collapsing in a big crunch.  He came up with this amazingly wacky notion he called inflation.  In the tiniest amount of time - beginning about 10^-36 seconds after the Big Bang and ending at around 10^-33 seconds -  the Universe inflates dramatically.  Distances between points expand at a speed far greater than the speed of light.  The Universe is not expanding into some existing space, but creating new space on its own out of nothing. The size of doubles, doubles again, again and so on for over 80 times - the size has increased by about 10³⁰ times.

 

This neatly solved several puzzles and the physics made sense. It struck many as being beautiful - but it was just a candidate.  A viable theory needs to make predictions that can be tested.  It turns out this one did just that.

 

A year earlier Arno Penzias and Robert Wilson were sprinkled with the Swedish holy water for their 1964 discovery of the Cosmic Microwave Background (CMB).  As the early Universe  expanded and it cooled. When it was a couple of minutes old it was so hot that regular matter was in the form of elementary particles and some simple atomic nuclei (helium and a bit of lithium).  It was far too hot for electrons to stay attached to the nuclei forming a plasma.   Light traveling in a hot dense plasma like this bounces off the electrons rather than just traveling through, so the Universe was opaque.  Expansion and cooling continued and finally, after about 380,000 years, it had cooled to a mere 3,000°K and electrons began to become attached to nuclei.  The first full fledged atoms formed.  Since light mostly passes through atoms the Universe finally became transparent and the first light we are capable of detecting filled started to travel through space.

 

Inflation predicted strong  gravity waves - ripples in spacetime itself.  Einstein had predicted these should occur when a mass accelerates, but gravity is an extremely weak force and gravity waves have eluded detection.  The inflating Universe was an extremely concentrated huge mass.  The waves would be  strong and would cause the plasma to jiggle.  These jiggles would manifest themselves in the motion and distribution of plasma that made up the Universe.

 

time to find a time machine and sunglasses

 

We can see this event with a time machine called a telescope.  Since the speed of light is constant you are looking at earlier times when you look at the sky.  A star 1,000 light years away left that star a millennia ago.  The first light from 380,000 years ago is distributed everywhere in the sky as the entire Universe is expanding.   We see this with special telescopes that are sensitive to light with much longer wavelengths than humans can see.

 

When light is reflected from a surface it can acquire a polarization.  Think of light as a two dimensional wave.  You can build a filter that will only let light that waves in one plane pass  - a wave at right angles will be blocked.  Polaroid sunglasses do just that.  You can put one lens on top of another and, by rotating it 90°, shut off the light passing through them.  They are very handy for cutting out glare caused by light bouncing off of flat surfaces like car hoods and water - just make sure they favor light that is vertically polarized.

 

As the Universe became transparent light bounced off electrons for the last time.  During that last bounce they were polarized - the type of polarization depended on the motion of the electron during the last bounce.  And so it was as they traveled through time and space, some of them end their journey on Earth.  The polarization pattern is a fossil and is communicating information from the period of inflation when the gravitational waves were generated.

 

Astrophysicists have been studying the nature of the CMB since its discovery and techniques have vastly improved.   We've learned a lot - including the age of the universe to two places after the decimal point.  Recovering the polarization signal from the primordial gravity waves was going to be a huge challenge - many thought a long shot, but several experiments took up the challenge.

 

Two major types of polarization are detected by such experiments.  The signature of gravity waves turns out to be sort of a twirl referred to as B-mode polarization.   I mentioned being excited by the value of r.  Think of r as the strength of the twirly polarization signal.  The most optimistic theories predicted about 0.1 - a level that should just be detectable by BICEP2 with luck.  But a surprise - Nature may be showing off something much stronger - a gift of sorts!

 

A stunning result like this is in need of confirmation.  Fortunately a few other experiments are various stages of data taking and analysis. so we should know in a year or two. 

 

I've glossed over so much.  The experiment is beautiful as is the apparatus.  The crowd was electric with excitement even though the video link broke under the load of a large worldwide audience. We followed tweets from the lecture hall.  I doubt the USA/Russia hockey match in the Lake Placid Olympics came close to matching the electric excitement in the room.   This is my tweet when I finally was composed enough to say anything...

 

If confirmed several theories bite the dust, a few are advanced and many new ideas will emerge.  Already there is a set of interesting new questions and potentially a new way of sorting out the very early times much more directly than ever before.  

 

The fundamental sciences are under attack in the US with funding dropping in many areas.  Congress is asking that only work that will directly benefit America in the near future be funded.  Scientists often point out the fruits of discovery - some of them from the discoveries themselves and many from newly invented apparatus and techniques -   but these things take time and trust.  At this point it is difficult for me to recommend that a young American go into the natural sciences.  Of course many will have a passion and just do it anyway and hooray for them:-)

 

Science goes beyond its role as a fundamental technology driver and that's what the passionate young scientist feels.  There are always questions that suggest new questions and searches.  How far back in time can you see? For 50 years we thought that was to the first light - 380,000 yrs ago.  All of a sudden we have a direct window back to a period about 10^-35 seconds after time and space came about.  Breathtaking, eh?

 

Asking questions of Nature - the learning and exploring - is a quintessentially human act and beautiful like art, music or poetry.    Richard Feynman said it well in his unique style:

 

Physics is like sex: sure, it may give some practical results, but that's not why we do it.

__________

 

I purposely left out footnotes this time and have glossed over a lot of physics and history hoping that it is understandable.    If you want deeper information on this or inflation I can point you to some great sources and I'm delighted to talk about it.  I'm sure questions come up - like why was this done at the South Pole (several reasons, but two big ones).

 

For a bit of insight into how physicists (and presumably many other scientists) play...  You  try to understand a bit of the underlying idea by playing around with some of the basic equations and see how they work out.  Sloppiness is the rule - you usually aren't looking for accuracy - so factors like  are often ignored.  Units are often picked to make mental calculations easier - in physics Planck's constant is frequently set equal to the speed of light and both are set equal to one.  I did my own back-of-the-envelope for a lot of this.  John Preskill posted his with some annotation.  I wouldn't expect anyone who doesn't have a bit of graduate level physics to follow this, but it shows off the idea.

 

__________

 

Recipe corner

Avocados are cheap and good these days.  This was a bit of guesswork that turned out well..

 

Avocado 'Mayo'

 

Ingredients

 

° 2 avocados

° 1 tbl white vinegar

° lemon juice - about half a medium lemon

° bit of onion powder (a "bit" is probably about 1/8 tsp)

° bit of garlic powder 

° fine sea salt to taste

 

Technique

 

° mash everything in a bowl using a fork - add the salt to taste.  You can use a food processor too

° use it soon after making - if you refrigerate it, warp it with plastic warp to minimize air contact.

 

 

 

 

 

Comments

[Jean Russell]

I love warping it with plastic warp. <3 can you do a future post on how you warp? This must be a physics thing.

[Jheri]

This helps a lot Steve. I read a few accounts that were too confusing and simplistic. I have a few questions burning. Can you explain why this twirling B-mode polarization is that way? Do only gravity waves cause that? Can you explain inflation to someone like me? What is currently meant by the Big Bang? An account in the paper here said the Big Bang was a “singularity” - what is that and is that correct?

[steve]

Good questions Jheri.

I can probably explain inflation with a bit of hand waving, but some of the reasoning as well as the result are very counter intuitive. You have to start out with the fact that a gravitation field has negative energy and the total energy of the Univere is very small and may even be zero. Strange concepts that cause conceptual difficulties. It is much easier for those with a good bit of quantum mechanics and general relativity under their belts. If you want to talk about it off line, let's give it a whirl.

The twirly polarization signal is probably only produced by an interaction between the gravity waves and the electromagnetic field. It has to do with the nature of the gravitational field and a property called spin, which is a bit abstract. But the bottom line is this is the only explanation that makes sense and the theoretical prediction is observed n Nature.

The term singularity doesn't have any scientific meaning. When you wind time backwards and extrapolate to the beginning of the Universe, you get zero size and infinite energy density at the moment of the Big Bang. This is unphysical and there is good evidence for something else - the stuff that seeded inflation. So if someone uses the term 'singularity' it is likely they aren't a physicist or astrophysicist.

It sort of makes sense to refer to the inflationary period as a huge hot explosion, except the explosion isn't expanding into space, but rather it is a pure expansion that is *creating* space. The distances between objects are expanding extremely rapidly - much faster than the speed of light. The objects themselves are not moving ... just the space between them is growing exponentially.

Real science is much more interesting that the best fiction human minds can dream up. Nature can be really weird by our standards:-)