Out Of Thin Air

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Out Of Thin Air

Stories about radical new spacedrives pop up surprisingly often. The latest eruption centers around the so-called EMDrive, and it has spread round the world – this link is from a New Zealand website. This gizmo claims to produce forward motion by bouncing microwaves around inside a metal container; warp drives have featured in other, equally far-fetched outbreaks.

Physics-wise, the EMDrive and the Warp Drive are as different as chalk and cheese, even if news reports mix them up. From the look of it, you could cobble together an EMDrive from the guts of a microwave oven in your home workshop, albeit a home workshop with welding and metalworking tools. By contrast, the warp drive springs from a recherché solution to Einstein's general relativity and needs "negative mass" to make it work; no-one has that sort of stuff in their garage.

EMDrives and warp drives do have one thing in common, though: even if you ignore the obvious impossibilities, technical accounts of both devices always seem to be self-contradictory. For the warp drive, there is a huge mismatch between the theory and the experiments that are supposed to test it. For the EMDrive there is indeed data, but the data does not match the predictions of the device's designers. This is normally a cause for concern, but last year's excitement took off before anyone noticed that the EMDrive still "worked" when supposedly crucial parts were removed. 

Scientists are naturally skeptical, but the degree to which we are skeptical depends on the circumstances. In the case of the EMDrive we should be very skeptical indeed (as Sean Carroll points out) as it appears to produce momentum out of thin air, something apparently forbidden by the theory used to design it. 

That said, an ounce of observation is worth a pound of theory. However, "thin air" is not just a figure of speech here. The effects attributed to the EMDrive are tiny, corresponding to forces far less than the weight of a flea, but large amounts of electrical power must be pumped into the apparatus to produce them. Power generates heat, heat leads to air currents, and these air currents could easily cause enough stray forces to explain the results. 

So the next step is to put an EMDrive in a vacuum chamber, and this is what set off the latest round of stories. The work is written up (although the not peer reviewed) and while the EMDrive produces a force in the latest experiments, the force remains when the microwaves are turned off. The EMDrive is supposed to work by bouncing microwaves around inside a fancy tin can, and again the observations do not match the predictions. However, the authors of the latest study prefer to say that it seems the "EMDrive got somehow charged and produced thrust which rather decays contrary to a simple switch off after power is removed [sic]". To me (and any other physicist I could ask) a far simpler explanation is that the device is still not completely isolated from its environment (since magnetic effects show up as well) and again does not work as predicted. But you won't get headlines from that. 

Beyond a lack of self-consistency, there is one more common factor between the warp drive and the EMDrive. That is NASA's tiny Eagleworks Laboratory, dedicated to investigating unusual propulsion systems. This is a great idea; we certainly expect NASA to be do cutting edge science. However, this lab has produced credulous analyses of both scenarios, and the kindest thing you can say about this situation is that optimism is winning over rigour. However, if "NASA scientists" weren't involved, the stories would be far less likely to make it into the mainstream media. 

Sadly, it seems that the device NASA really needs is a bullshit detector. And if they built one and shared it with the world's journalists we would really have something to celebrate. 


CODA: The title image is from Wikimedia – amazing what you can find if you look. And this blog by Corey Powell gives a lot of background information on the previous claims about the EMDrive.

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Electric Avenue

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Electric Avenue

Bikes, at the Aspen Center for Physics. Image: Richard Easther

Bikes, at the Aspen Center for Physics. Image: Richard Easther

Last month, I visited the Aspen Centre for Physics, on the outskirts of Aspen, Colorado. It is a wonderful place: they give you a desk, a wifi connection, time to think, and a bike to get around town.

Poster of Einstein, Image Richard Easther

Poster of Einstein, Image Richard Easther

It's no coincidence that, in the lobby of ones its buildings, the Center has a poster of Einstein on a bike. Einstein is often quoted as saying he got his best ideas on a bicycle. (Although if Einstein actually said all the things he is supposed to have said he must have been more talkative than most human beings.)

Officially, I was in Aspen to think about the Big Bang, but while I was there I also found myself mulling over the physics of cycling. Not the physics of why bikes stay up (although that is complex and certainly interesting), but how physics lets bikes be so good at what they do.

Pedestrians: Hadazbe tribespeople, returning from a hunt. Image: Wikimedia

Pedestrians: Hadazbe tribespeople, returning from a hunt. Image: Wikimedia

Physicists often look at the world in terms of energy. To a physicist, power is the rate at which a system uses energy, and we measure power in watts. A typical pedestrian in motion has an "output" of about 70 watts, similar to the energy emitted by an old-school incandescent light-bulb. (The 70 watts is the extra mechanical power delivered by your body when you get up and start walking.)

Image: Jolisa Gracewood

Image: Jolisa Gracewood

Typical urban cyclists use energy at roughly the same rate as pedestrians, but travel about three times faster. Or put another way, you can cover three times as much ground on a bike as you do on foot, for the same amount of effort.  Speeds vary, but 15 kilometres an hour is reasonable for an "upright" cyclist, whereas typical walking speeds are around 5 kilometres an hour. 

Tour de France riders. Image: Wikimedia

Tour de France riders. Image: Wikimedia

By contrast, Tour de France riders manage a sustained output of close to 300 watts, just over four times more effort than you need to move at a comfortable walking pace. Regular human beings can only maintain this level of activity for a minute or two before tiring. 

Windsock   Image: Wikimedia

Windsock   Image: Wikimedia

So when you're on a bike, where does the energy go? A cyclist traveling at a constant speed on flat ground must replace energy lost to friction and air resistance. The frictional forces acting on a bike (i.e. at the point of contact between the wheels and the ground, and in the chain and gears) increase in proportion to the cyclist's speed. But air resistance is worse: "drag" really is a drag. The faster you move, the more air you move through. And when you are moving quickly, you are stirring the air more vigorously. The combination of these two effects makes air resistance a double whammy for cyclists: doubling your speed, even on a still day, increases the air resistance by a factor of four.  And winds just make things worse -- even a gentle headwind can double the air resistance, boosting the energy cost of cycling. So you really feel a headwind on a bike. 

One Tree Hill, Auckland  Image: Wikimedia

One Tree Hill, Auckland  Image: Wikimedia

And let's not mention the hills... Except that in Auckland we really do have to talk about the hills. Ancient Rome may have been built on seven hills, but my city of Auckland is built around something like 40 (inactive!) volcanic cones. Auckland is not as vertiginous as parts of San Francisco, but it is decidedly lumpy when you get on a bike.

Tower crane   Image: Wikimedia

Tower crane   Image: Wikimedia

The problem with hills is that they turn your bike into a crane; you are not just moving horizontally, but you have to lift yourself and your bike to the top of the hill. And that costs energy.

Image: Richard Easther

Image: Richard Easther

It doesn't need to be a big hill. Even a gentle slope doubles the energy output of a cyclist; the "hill" in the picture above has a slope of 2%, but if you wish to keep moving at a steady 15 kilometres an hour, you would need to double your energy output to climb it on a bike. You can climb it more slowly (that's what gears are for) but if you want to keep moving more quickly than a pedestrian you have to work harder to climb the hills. Anyone who has ever got off their bike and pushed it up a hill knows that there is a point at which you might as well walk.

US Marines   Image: Wikimedia

US Marines   Image: Wikimedia

Given the hills and headwinds, riding to work may only be workable if you don't mind a workout on the way to work. So for many people hills and headwinds are what keep our bikes in the garage, rather than out on the road.

Electric bike (and Auckland harbour)  Image: Antoine Peters

Electric bike (and Auckland harbour)  Image: Antoine Peters

But if physics explains why cycling can be hard work, it also generates the solution: the electric bike. In New Zealand, the energy output of an electric bike is legally limited to 300 watts: any more and it is a motorbike, not a bike with a motor. But even this little motor is like having a Tour de France rider hidden in your hub, helping you up the hills.

The Flinstones Image: Hanna-Barbera

The Flinstones Image: Hanna-Barbera

This explains why no-one adds pedals to a car: while a little motor is a big help to a cyclist, even a small automobile engine can deliver up to 100,000 watts and no human being could contribute enough extra energy to make a difference to a car. (No-one told Fred Flintstone this.) But on an electric bike your legs can always make a useful contribution.   

Image: Universal Pictures

Image: Universal Pictures

The upshot is that an electric bike works the way bikes work in our dreams. On an e-bike, hills and headwinds don't slow us down, and the motor is small enough to make sure it still feels like you are riding a bike.

A cyclist's little helper?  Image: Wikimedia

A cyclist's little helper?  Image: Wikimedia

And while e-bikes can let anyone cycle like a crack athlete, you can still look our kids in the eye when you get home at the end of the day. 

Auckland traffic   Image: Youtube

Auckland traffic   Image: Youtube

There is a fair bit of excitement about electric cars, but when it comes down to it, they are still cars. They might reduce your carbon footprint, but they won't change your life – if you swapped all the regular cars on a traffic-clogged road with electric cars, it would still be clogged with cars. Whereas electric bikes let us live in ways that regular bikes (or cars) do not.  

Copenhagen street scene. Image: Wikimedia

Copenhagen street scene. Image: Wikimedia

We hear a lot about how cities like Auckland should be more like Amsterdam or Copenhagen. There are all sorts of barriers between us and that aspiration, but hills don't need to be one of them. 

Skypath proposal, Auckland Harbour Bridge  Image: http://www.skypath.org.nz

Skypath proposal, Auckland Harbour Bridge  Image: http://www.skypath.org.nz

Over the next few years, Auckland is going to get some stunning cycling infrastructure and my hunch is that electric bikes will help Aucklanders make the most of it. Bikes gave us a better way of getting around than walking, and electric bikes give us a better way of biking.

You don't have to be Einstein to understand this. Just get on an e-bike and take it for a ride. 


CODA: This blog is based on a Pecha Kucha presentation I gave in Auckland; you can watch it on video here. 

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Einstein's Magic Bag

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Einstein's Magic Bag

In 1915, Berlin was at the centre of an empire locked into a global war. But at least one resident of that city had his mind elsewhere: Albert Einstein was working to reconcile gravity with the theory of relativity he had invented a decade earlier. Einstein solved the problem by year's end, and in doing so he changed our understanding of space and time forever. 

For Newton, space and time are the stage upon which the play-of-the-world takes place. The actors – planets, stars, people, atoms, and even light itself – move in space, but space itself is fixed and unchanging. In Newton's universe, space tells us where things happen and time tells us when things happen but nothing happens to space or time; gravity reaches across space, but does not change space itself. 

In Einstein's universe, space is shaped by matter and that shape changes when matter changes its position. Einstein brings the wooden stage of Newtonian physics to life; space now responds as the actors move about. For a physicist, Einstein's understanding is as shocking and wonderful as a play in which the theatre springs to life and takes a speaking role in the drama.

Einstein welded space and time together into spacetime and showed that mass curves spacetime, and that gravity is encoded in this curvature. In Newton's universe, gravity drags the earth around the sun. In Einstein's universe the sun bends spacetime and the earth circles the sun by following the simplest path it can find though spacetime. 

This year marks the centenary of Einstein's breakthrough, his General Theory of Relativity. The mathematical expression of the theory, the Einstein field equations,  would fit on a postcard:

  The Einstein Field Equations: the left hand side depends on the shape of spacetime while the right-hand side tracks the distribution of energy and momentum. Or, as John Wheeler put it, space (the left hand side) tells matter how to move, while matter (the right hand side) tells space how to curve.  

 

The Einstein Field Equations: the left hand side depends on the shape of spacetime while the right-hand side tracks the distribution of energy and momentum. Or, as John Wheeler put it, space (the left hand side) tells matter how to move, while matter (the right hand side) tells space how to curve.  

But the Einstein equations are a magic bag: far bigger on the inside than they appear on the outside. One hundred years later physicists and mathematicians are still working to unpack this expression and to fit it to the rest of our knowledge about the universe. Einstein's new theory immediately solved a 100 year old riddle, explaining why Mercury's orbit around the sun did not quite match Newton's predictions. Within 10 years, the underpinnings of the Big Bang and the expanding universe tumbled out of the magic bag of General Relativity: the universe is not expanding because distant galaxies move through space; the galaxies move because space itself is expanding. "Expanding space" is an idea you can have only after General Relativity tells you that spacetime is dynamical, rather than fixed and static.

Beyond clearing up the niggling behaviour of Mercury, Einstein made two predictions, each of which is a test that General Relativity must pass. First, gravity bends the passage of light itself; second, clocks run more slowly in strong gravitational fields. The bending of starlight was detected in 1919, via the changing positions of stars near the sun during a total solar eclipse; the slowing of time was inferred from observations in the 1920s and spectacularly confirmed in 1959. (And understanding this phenomenon is key to getting the GPS system to work, believe it or not.)

And there is much, much more. In 1915, also Einstein showed that as large objects accelerate they generate waves in spacetime. One hundred years later these "gravitational waves" have never been directly observed, but Advanced LIGOthe first observatory that should be sensitive enough to find them, is being commissioned just in time for the theory's 100th birthday. 

  The LIGO gravitational wave detector - the strongest gravitational waves that we hope to observe will the move mirrors at each end of the "arms" by a distance that is a billion times smaller than the diameter of a typical atom.  

 

The LIGO gravitational wave detector - the strongest gravitational waves that we hope to observe will the move mirrors at each end of the "arms" by a distance that is a billion times smaller than the diameter of a typical atom.  

Likewise, a fully unified theory, a self-consistent quantum mechanical description of gravity alongside the other forces in nature is as elusive today as it was for Einstein, who searched in vain for such a model during the last two decades of his life.

So 100 years on, physicists are still unpacking the magic bag Einstein that discovered in 1915... 


kavlinew-757x467.jpg

At 8pm on Saturday May 30 in New York, the World Science Festival is holding an event Reality Since Einstein moderated by Brian Greene, bringing together some of the world's leading gravitational physicists to talk about our current understanding of gravity and the prospects for future progress.  A live-stream of the event will be shown on the Auckland campus (free, but please register) followed by a Q&A (hosted by me), and we will broadcast our Q&A on Periscope.tv (follow @reasther). The Auckland event begins at Noon on Sunday, May 31, New Zealand time. 

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Thinking Science

Thinking Science

On March 14 this year, thinkScience made its public debut at the Auckland Arts Festival with a day-long series of events within the Festival programme. Or, as our supporter and friend, Nat Torkington put it, thinkScience shipped its first product. The startup theme was apt, as the day began with panel discussions in the Festival's Spiegeltent, looking at how cities work; the natural, technological, and human networks they contain, and their ability to nurture new ideas. The panels brought together scientists and scholars Tim Hazeldine, Steve Pointing, Cather SimpsonShaun Hendy and Ella Henry, social entrepreneur Lillian Grace, and Vend's Vaughan Rowsell and Xero'Victoria Crone, all deftly steered by Jon Bridges. 

Aucklanders were promised that thinkScience would "Blow things up, blow things over and blow your mind!" and we made good on that commitment to an audience of 1,400 with Michelle Dickinson's Nanogirl show at the Town Hall. The show itself was spectacular and the explosions were, indeed, awesome. My day was made when one father told me that the best part of the show for him was watching his daughter watch Nanogirl on stage, and dream about what she might do with her life. 


Nanogirl - Live at the Town Hall


Outside in Aotea Square, Siouxsie Wiles and a band of helpers spent the afternoon running the Glowbooth, taking photographs of passers-by in the light of bioluminescent bacteria. 

Me, by bug-light...

Me, by bug-light...

And in the aptly named Vault of the adjacent Q Theatre, Siouxsie and seven artists created images on arrays of petri dishes, "painting" with the same bugs that power the Glowbooth. These evanescent works lived only as long as the bacteria themselves, providing a fertile medium for a playful interaction between art and science. 


Bioluminescent Art 


As an organisation, thinkScience is lucky enough to be nurtured and supported by the Auckland Arts Festival and its talented staff, especially Gareth Baston who wrangled explosions and petri dishes with equal panache. The event harnessed a dream team of New Zealand science communicators – Michelle Dickinson, Shaun Hendy and Siouxsie Wiles are all winners of the Prime Minister's Science Media Communication Prize – and was sponsored by the University of AucklandMBIE, Te Punaha Matatini, the MacDiarmid Institute, the Maurice Wilkins Centre and the Foundation North, previously the ASB Community Trust. Finally, an "angel investment" from Ian Kuperus of Tax Management NZ got us off to a flying start as we launched thinkScience. 

thinkScience grew out of a coffee-date I had with Auckland movers and shakers Victoria Carter and Robby Hickman just before Christmas in 2013thanks to connections made by Jolisa Gracewood. We have a slew of plans for the future, including building a bigger base of supporters (thinkScience is now a charitable trust, thanks to pro bono legal services from Buddle Findlay), and are committed to fostering public engagement with the science that lets us understand our world and to construct its future. Stay tuned.


Big Astro

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Big Astro

The advent of the web and social media have led to a huge outpouring of enthusiasm for science but almost all sciences have skeletons in their closet, some real and some imaginary. Physicists gave us the bomb, chemists cook up the chemicals they put in the food (yes, yes, and you cheerfully drink H-2-O and breathe O-2) and even if medical researchers have doubled our lifespan many will claim they are in thrall to Big Pharma and specialise in diseases of the rich, in addition to perpetrating more specific and chilling abuses. But astronomers often sail past earthly concerns. After all, what's not to like? Astronomy generates an endless stream of stories about strange planets, unlikely stars, and the birth of the universe, but nothing anyone can easily get upset about. 

Even journalists suspend their usual rules for astronomy and other good-news science stories. Copy approval, sending sources a draft of an article for commentary and correction, is anathema to journalists on a hard news story, but I am often sent drafts "to check the details" when I talk to the media about astronomy. So perhaps this is why astronomers have been caught flat-footed by the apparently sudden eruption of protest around the Thirty Metre Telescope, or TMT. The issue is not the $1.3 billion price tag but its location at the summit of Mauna Kea, the highest peak on Hawai`i's Big Island. The problem is that while Mauna Kea is a fantastic place for astronomy (a huge mountain rising out of the Pacific Ocean; the skies above it are stable and clear) it is also sacred to many native Hawai`ians. The issues are far from straightforward, but Buzzfeed (in its new incarnation as a purveyor of long-form news) and the Huffington Post have summaries of recent events and TMT consortium has put its own response to the controversy online. However, for some astronomers it has led to the discovery that they may not always be the good guys.

While we might wish it were otherwise, astronomy is not apolitical. Science communicators (myself included) wax eloquent about space exploration, but the space race was launched by Cold War competition. Nor is the politicisation of astronomy new. The British navigator, James Cook, set sail in the Endeavour from Plymouth in 1768 to observe the transit of Venus from Tahiti, as part of a campaign to determine the overall scale of the solar system. Cook carried additional sealed orders to be opened after the transit observations were complete, which told him to continue from Tahiti on a voyage of discovery into the Pacific; part of the larger competition between European powers to explore trade-routes and acquire outposts around the world. (By many accounts, the contents of those orders were well-known around London before he sailed.) And like a modern-day space programme, Cook's voyages were a simultaneous national investment in pure science, prestige and geopolitical leverage. [And Cook and Hawaii are tightly connected – he commanded the first European ships to make landfall in Hawai'i, and was killed in a skirmish there in 1778.]

New Zealand and Hawai`i are both parts of the Polynesian world. As a New Zealander, much of the language used by the Mauna Kea protestors is familiar from local debates. From a purely linguistic perspective maunga, which is mountain in Te Reo (as the Māori language is referred to in New Zealand English), is cognate to the Hawai`ian mauna. Hawai`ian and Māori both speak of their alienation from their traditional resources by the arrival of Europeans, and their deep connection to the land. In a formal setting, a person introducing themselves in Te Reo will open by listing their whakapapa or ancestry, along with their maunga, awa (river) and moana (sea), identifying themselves both with their genealogy and their specific point of origin. 

And worldviews really do differ. If you are an astronomer or astrophysicist it is not uncommon to hear enthusiastic talk about founding "colonies" on the Moon or Mars. Obviously, the "final frontier" is genuinely unpopulated, but it is worth reflecting that colonisation is not a happy word for many of our planet's inhabitants.

No group is monolithic, and many Hawai`ians are clearly excited about the construction of the TMT. However, it is tempting for astronomers and advocates for the TMT to listen to these Hawai`ian voices, and assume that the other side is being stirred up by a few malcontents. However, from the perspective of a European New Zealander (pākehā, in the local terminology) the concerns being raised about the TMT and the use of Mauna Kea for astronomy in Hawai`i closely match those heard in discussions about the ownership and use of natural landmarks in New Zealand. 

As an astrophysicist, I hope that the TMT will be built – it is an astonishing instrument, big enough to catch the the light from the first generation of stars to be born after the Big Bang, and sharp enough to make images of planets around other suns. However, I also hope that my community can do this without riding roughshod over a people who claim Mauna Kea as their own. Whether or not this this is possible with Mauna Kea I cannot say, but simply denying the validity of these concerns is not a promising start. 


Image: Visualisation of the TMT; tmt.org

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