Illuminating Reality

Have you heard that the Universe is expanding? Edwin Hubble changed astronomy in the 1920s by discovering this, but did you also know that the expansion of the Universe is actually accelerating?  This was one of the biggest surprises in Cosmology back in 1998, leading to the discovery of the mysterious Dark Energy that makes up the vast majority of the energy density of the Universe.  Now to measure the expansion of the Universe, astronomers needed a way to accurately determine extreme distances.

One of the most effective ways to do this is to look at the apparent brightness of lights of a known magnitude.  Because light energy fades in a very predictable way (inverse square falloff), you can determine the distance accurately as long as you know the absolute brightness.  So try this thought experiment: if you went out on a deserted road at night and placed 100 watt light bulbs along the road every hundred meters, the closest lights would be the brightest and the farthest would be the dimmest - yet in reality they are all of the same absolute brightness.  If you stand next to each of them, they put out 100 watts of energy, but the light traveling from the farther ones loses energy, so it appears dimmer.  So by measuring the brightness of each light you could determine the distance because you know how bright it actually is and how bright it appears; essentially just by measuring the loss of energy over distance.

So how do we do this to measure the distance to stars?  As you can see in the image to the right, stars come in a wide variety of sizes and brightness (click to enlarge).  From the relatively cool, tiny Red Dwarf to the hottest, most massive blue Hypergiants, the brightness of stars varies considerably even amongst the same type.  With so much variation, it would be impossible to accurately use brightness to measure distance.  If only there was a class of bright object scattered throughout the Universe that always had the same brightness?  It turns out there is!

Read more…

Did you know that gravity is a bit of a mystery to scientists?  Given that we have space probes orbiting Saturn and Mars right now, you’d think it would be well understood, but the reality is it’s the most mysterious of the Four Fundamental Forces of Nature.   Mathematically it’s well understood and can be calculated with great precision, yet it’s so weak compared to the other forces, all of which are roughly comparable to each other.  How weak? Try – 10⁴⁰ weaker than the electromagnetic force, in other words:

0.00000000000000000000000000000000000000001 times as strong

Don’t believe me? Ever notice that you can pick up a paper clip with a refrigerator magnet, which is pretty weak, with relative ease?  The gravity from the entire mass of the Earth is being defeated by that little magnet, which seems so unintuitive and bizarre, doesn’t it?

The Four Fundamental Forces of Nature, according to the Standard Model, are Electromagnetism,  Strong Nuclear Force, Weak Nuclear Force and Gravity.  This isn’t speculation either – the Standard Model is one of the greatest achievements in Science, forming the backbone of modern physics and it works exceptionally well.

These forces interact with matter via carrier particles (aka bosons) and have a finite range to their interaction – except gravity.  To this day there is no known force carrier particle for gravity (they’ve been theoretically dubbed “gravitons”); it can’t be absorbed or shielded like the other forces; it has an unlimited range and it’s behavior is always attractive in nature; it’s somehow tied to the mass of objects in that it interacts with every particle that has mass.

Understanding gravity has been a long and storied endeavor, but it was Sir Issac Newton who made the first significant breakthrough when he published his Principa Mathematica in the 17th Century, wherein he described his universal law of gravitation.  His simple equation was highly accurate at calculating the motion of everything from objects falling out of a tree to the orbit of planets.  His work survived for two hundred years as the dominant theory of gravity until Einstein came along in 1905 and fundamentally changed the way we think of gravity.

Part of the problem was that there was no known mechanism for gravity.  It’s effects could be calculated, but it wasn’t clear how, for example, the Sun reach out to the Earth, across 93 million miles of empty space and tugged on it.  Einstein wondered if the Sun disappeared, how would the Earth know?  In other words, how did the force actually work to travel that distance?  Part of the problem it turns out was that we were thinking of Gravity in the same way we thought of the other known force at the time: electromagnetism.  Einstein radically overturned Newton by defining gravity not as a typical force but as curvature of space itself.  When Einstein published his Theory of Relativity ushered in a new age of physics, solving many of the outstanding problems of Newton’s theory – mainly that because gravity distorts space, the Sun reaches out to the Earth through that distortion to pull the Earth inward.

Einstein’s theory was confirmed  in many areas such as resolving the long standing anomaly with Mercury’s orbit that Newton’s theory couldn’t account for as well as the observed phenomenon of light being refracted by the mass of the Sun during a total eclipse.  Like any good theory, Einstein’s work makes lots of testable predictions that have been observed over the years, but around the same time he was getting lots of attention in the world, the world of atoms was slowly being revealed and it required a new kind of physics to describe.

Quantum Mechanics is to sub-atomic particles what General Relativity is to the orbit of planets.  It’s the physics that accurately models the way atoms and sub-atomic particles interact and has been tested to a high degree of accuracy as well.  There is a really big problem though: Quantum Mechanics does not jibe well with General Relativity.  Physicists tried using Einstein’s equations to model the interactions of molecules and atoms to find that as you get down to those very small scales, everything starts to fall apart and you get gravitational values of infinity (psst, that’s a sign there’s a problem with your theory).

So General Relativity is shown repeatedly to be correct on large scales and Quantum Mechanics is shown to be accurate the same way at the sub-atomic scale – what gives?  Gravity is messing things up in a big way or should I say our incomplete understanding of gravity is messing things up.  Finding an accurate quantum-scale model of gravity has been an elusive quest for physicists.  Some of the ongoing attempts include Loop Quantum Gravity*and String Theory, both of which are so theoretical that they currently can’t be tested in the first place.

This is why the Large Hadron Collider (LHC)  is particularly exciting to physicists.  It’s hoped that when it’s operating at full power, the LHC will be able to expose the innards of the sub-atomic world at an energy scale never before witnessed.  This could be the very device that detects gravitons, the theoretical force carrier for gravity or the Higgs boson which is theorized to give particles mass (remember, gravity is related to mass).  Exciting stuff!

So gravity remains a mystery for now; something we understand well enough to calculate its behavior extremely accurately, but mysterious enough that its mechanism remains elusive.

* Read Lee Smolin’s “Three Roads to Quantum Gravity” for an introduction to the theory…have aspirin handy.

The Large Hadron Collider (LHC) at CERN successfully collided two proton beams yesterday!  Yes, we are still here – the Earth hasn’t been destroyed by a black hole or created a rift in the space/time continuum.  This has been a long time coming, especially after the setbacks of the last year – first with a superconducting magnet failure and more recently with a mischievous bird dropping pieces of baguette in vulnerable areas.

That picture over there is part of the detection display at the  CMS experiment (click the image to see the full display).   Where those green lines converge in the center is the point of collision.  The green lines shooting out are tracks of unstable, charged pions as they fly to the detector strips in the device (the yellow rectangles).  The red and blue boxes show where the energy was detected and that’s key to these experiments.  At higher and higher energies, particle collisions tend to reveal their “guts” in more detail and the LHC will be operating at the highest energies we’ve ever collided particles with.

Exciting times ahead!

String Theory is one of the newest chapters in our attempt to develop a theoretical physics model of how the Universe works. It came about as the result of the incompatibility of General Relativity and Quantum Mechanics. Those two theories have proven exceptionally accurate but only within their domains. Einstein’s General Relativity supplanted Newton’s classical mechanics by describing space and time as an interwoven fabric that mass distorts and it has been proven over and over again to be correct, however when you start to apply it to the realm of the very small such as atoms and sub-atomic particles the theory completely falls apart. As early 20th Century scientists started to study atoms they discovered there was a new physics needed to describe their behavior – this lead to the development of Quantum Mechanics, which has also been shown to be exceptionally accurate at describing the tiny sub-atomic world, yet when you apply it to large scales it too falls apart. This incompatibility confounded physicists for several decades and the idea of a unified theory that worked on all scales seemed almost impossible.

Then String Theory came around as an attempt to try to merge the two together to a loose degree. The idea is rather elegant, describing the smallest sub-atomic bits as strings or loops of energy vibrating at different frequencies. These different frequencies describe different particles, so one type results in protons, the other in electrons, etc. Mathematically it solves lots of problems, but also creates a few bizarre ones. For example, for everything to resolve to describe the Universe we observe, String Theory suggests up to 11 higher dimensions – that’s quite a bit more than up-down, left-right, backward-forward(X, Y, Z) and time. But the biggest problem of all is that currently there is no way to test String Theory’s predictions and in science, being unable to do so is a non-starter. Nevertheless, many physicists are pouring their careers into making it all work, but if you thought Quantum Mechanics was difficult to wrap your anthropic brain around, check out this ultra-simplified description of String Theory in under two minutes. This video won a well deserved award in the scientific community…

Ethan Siegel has an interesting write up on Starts with a Bang where he answers the question:  what did the big bang sound like?  This is an interesting question because, naturally people assume the Big Bang was an explosion in space and explosions make sound, right?  The reality is the Big Bang was an explosion OF space and time, but also we know quite well that sounds doesn’t travel in a vacuum and therefore you can’t hear anything in space.  Or can you?

To answer this question you first have to ask:  what is sound?  Sound comes from changes in pressure as a wave moves through a medium (air or water for example).  This is how speakers work; compressing or stretching the air around them by using magnets to distort and vibrate a surface.  The higher the frequency, the higher the pitch but the human ear can only hear a certain frequency range, so it would have to remain within that spectrum for us to hear it.

So we know space is nearly a vacuum so the density of the medium is almost non-existent and therefore impossible to travel through.  For us to be able to hear sound in space we’d need the vacuum of space to become significantly more dense, similar to the air we breathe.  This may sound impossible, but it isn’t when you consider that the Big Bang shows us that if we go back in time we find the matter in the Universe in a much, much more dense state.  Go back far enough and you start to approach the density of air on Earth – but all around you!  So yes, we could hear the Big Bang at this point, but there would be the small problem of space being almost a billion degrees Fahrenheit versus the near Absolute Zero it is now.

How loud would it be? Check out Ethan’s blog…

It’s pretty obvious to me that the vast majority of folks out there in the public know very little about the Big Bang Theory and even less about Quantum Theory.  Don’t get me started on the New Age interpretations of the latter having anything to do with consciousness, but regardless both subjects are very important to Cosmologists these days.  Last week I came across this brilliant discussion in Australia that covers some interesting aspects of both Physics and Cosmology.  You can click through “chapters” of the video by selecting a subject, but overall the entire piece is quite illuminating.

A description of the talk:
The two towering achievements of modern physics are quantum theory and Einstein’s general theory of relativity. Together, they explain virtually everything about the world in which we live. But almost a century after their advent, most people haven’t the slightest clue what either is about. Radio astronomer, award-winning writer and broadcaster Marcus Chown talks to fellow stargazer Fred Watson about his book Quantum Theory Cannot Hurt You.

If you were to stop people on the street and ask them to name a famous equation, I suspect the most common answer you’d hear is Einstein’s Energy/Mass equation: E=mc² But as a follow up, I pretty much guarantee the majority of folks who will give you that answer won’t be able to explain what it means.  Do you know?  What is the meaning of arguably one of the most important and elegant equations in physics?

The equation itself is quite simple:  Energy (E) equals Mass (m) times the Speed of Light squared (c – a really, really big number).  What Einstein realized is that matter and energy are deeply intertwined and that you could convert one to the other and back again.  What the equation tells us numerically is that it only takes a little tiny bit of mass to generate huge amounts of energy as we see in atomic bombs.  Of course, atomic bombs aren’t exactly pure conversions of energy; for that you have to look at antimatter.  When matter, the stuff we see around us is made of, comes in contact with antimatter the two annihilate each other into a 100% conversion to energy, releasing those big numbers you get when you multiply even the tiniest amount of mass with the speed of light squared.  So yes, your keyboard is a potential nuclear bomb of a truly frightening scale.  But at the same time, understand that this is essentially what is happening deep in the core of the Sun, fusing hydrogen into helium and releasing energy in the process (and losing a tiny bit of mass because of that energy release).  That warmth you feel at the beach is the thermal radiation from the Sun’s conversion of mass to energy.  Not all bad, right?

So when you think of Einstein’s famous equation or someone asks you about it (hey, it happens to me sometimes), just remember that you are made of matter and because of that you have tremendous amounts of energy stored within and that simple equation tells us how much.

For more on this, check out Ethan Siegel’s new article in Seed Magazine…

http://seedmagazine.com/content/article/because_emc2/

Hurray!” say the scientists.  “Oh noes!” say the pseudo-scientists.

CERN has announced that the LHC (Large Hadron Collider) will be operational again come November after it’s year long shutdown caused by a nasty leak at start-up last year.  Along with this announcement is the news that during this next phase it’ll be running at collision energies of 7 TeV, rather than the 14 TeV the LHC was designed to generate.  This isn’t such a bad thing because it’s still in an energy range beyond what current colliders can achieve, but it’s still not the level that is expected to result in new discoveries.  So we will have to wait a while longer to find out about Supersymmetry, extra dimensions, or the Higgs Field.

Last year there was quite a lot of uninformed chatter about the LHC creating black holes that would gobble up the Earth or just criticism that the $6 billion cost was not worth it.  I’d really like people to think about that and understand where we’ve come from in the past in that regard.  Prior to the LHC, CERN was running the the Large Electron–Positron Collider (LEP) full tilt and generating so much data that a little old thing called the World Wide Web was developed to help scientists share the data.  It’s impossible to predict what kind of benefits will come from advanced physics research like this but already the LHC’s cutting edge superconducting magnet technology has peaked the interest of fusion power researchers.  If twenty years from now those researchers are able to create viable fusion power for the world, then the investment in the LHC will prove well worth it.