Let’s Go to Mars!

Dreams of colonizing Mars (and beyond) came into the spotlight this week when the Defense Advanced Research Projects Agency (DARPA) announced their 100-year Starship Study.  The study, a joint effort between DARPA and NASA Ames Research Center, will evaluate the feasibility of colonizing Mars and possibly (eventually) even other solar systems.  This announcement has come with concrete proposals including plans to introduce synthetic life for terraforming, build robots that can be launched from Mars’s moons, develop one-way missions to send a few humans to settle permanently on Mars, and of course,

Astronomers find ET habitability, but only for the biological.

The Search for Extra Terrestrial Intelligence, or SETI, has made a business of looking for signs of intelligence in the universe.  Recent data from a team of astronomers at UC Santa Cruz and the Carnegie Institute for Science have given SETI a promising place to focus their attention: Gliese-581 g, a planet 20 light-years away, in the ‘habitable zone’ around the red dwarf star Gliese-581.  Many factors determine whether a planet is habitable or not, ranging from the obvious variables, such as distance to the star and the star’s luminosity, to the less obvious variables, such as whether or not the planet has a large enough moon to keep its rotation stable or a giant neighbor (such as Jupiter) to sweep away dangerous incoming asteroids.

This discovery, made with the help of the new Kepler spacecraft, suggests that Gliese-581g may have the right conditions for liquid water, considered by many exobiologists (or astrobiologists: those who theorize about extra-terrestrial life) to be essential for life.

However, some have argued that since it’s not life but intelligence that we’re really after, the habitable zone may be the wrong place to look.

Fundamental Constant Varies by Space, Not Time

Photo by NASA/ESA

It has long been thought that the universe is spatially symmetric with respect to its fundamental physical properties.  Cosmologists relying on data from different regions of the sky (collected from different hemispheres or during different seasons) have always arrived at similar conclusions about the general features of the universe.  But new research indicates the universe might not be so symmetric after all.

A group of astrophysicists

The Difference Between Math and Physics

Recent headlines boast that string theory is finally testable.  If true, this would mark a significant turning point for the speculative theory.  Touted as a potential TOE, or theory of everything, string theory attempts to unite general relativity (our best theory of the very large) and quantum mechanics (our best theory of the very small).  The theory has been around for decades, but has yet to make a single, testable prediction.  The problem lies in the fact that string theory has so many independent constants, it can accommodate almost any empirical data.

Until now, argues Michael Duff of Imperial College, London.  According to a PhysOrg report, the insight came when Duff attended a “conference in Tasmania where a colleague was presenting the mathematical formulae that describe quantum entanglement: ‘I suddenly recognised his formulae as similar to some I had developed a few years earlier while using string theory to describe black holes. When I returned to the UK I checked my notebooks

Another Failure of A Priori Physics

It is an all-too-familiar phenomenon in philosophy: something that seems undeniably true turns out to be false.  For example, philosophers used to believe that space has Euclidean structure and that we can discern this structure from an armchair.  But then Einstein demonstrated that an entirely different structure is not only possible but (almost certainly) actual.  Some philosophers, such as George Bealer, think that since actual physics can never expand the realm of possibility, these examples show that our pre-theoretical intuitions about physical possibility were flawed all along.

Now another example of something that exists despite seeming a priori to be physically impossible: auxetic materials.  These puzzling substances don’t get thinner when they are stretched,

Is there ANYTHING we can’t explain with thermodynamics?

Philosophers David Albert and Barry Loewer have long argued that thermodynamics (or, more broadly, statistical mechanics) can explain the direction of time, the regularities of the special sciences, our memories, and our ability to control the future and not the past.  As if this weren’t enough, a recent article in the New York Times reports that Dutch physicist Erik Verlinde thinks thermodynamics can explain gravity too!

According to his paper, if we accept the holographic principle (very roughly: that the spatial dimensions of the universe emerge from its boundary conditions) popular among string theorists, then the motions of bodies through that emergent space

The Origin of Quantum Interpretation

There is a new book I’d like to read: Quantum: Einstein, Bohr, and the Great Debate about the Nature of Reality, by Manjit Kumar.  The book is a non-technical account of the discoveries and arguments that led to the Theory of Quantum Mechanics we rely on today.  According to Graham Farmelo’s review of Quantum in the New York Times last month, the book is full of interesting anecdotes about the physicists, their ideas and their disagreements.

Early quantum mechanics is often portrayed as a battlefield from which Bohr emerges victorious while Einstein recedes into the background.  Bohr’s view is now taught to almost every undergraduate physics major and philosophers routinely refer to his view as the ‘Standard Interpretation’.  However,