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Official page of #ScienceSunday and #ScienceEveryday (brought to you by Robby Bowles, Allison Sekuler, Rajini Rao, Chad Haney, Buddhini Samarasinghe, Aubrey Francisco, and Carissa Braun)
You have found the official page for #ScienceSunday (co-curated by Robby Bowles, Allison Sekuler, Rajini Rao, Chad HaneyBuddhini SamarasingheAubrey Francisco, and +Carissa Braun)! Post anything related to science and tag it with #ScienceSunday, +ScienceSunday, and each curator to ensure we see your post. If you are a photographer, post a science related image and explain why it relates to science to you - doesn't need to be too specific (science is all around us!). If you are not a photographer, simply post anything related to science - drawings, movies, songs, and text are all welcome. Regardless of the type of post, feel free to add your 2 cents into a discussion in the comments. We always have some great posts with amazing images, great science information, and a lot of interesting conversations, and we're looking forward to even more in the weeks to come. If you miss the "Sunday" in #ScienceSunday, feel free to tag with #ScienceEveryday - we try to monitor those posts as well.


Weekly SciTech

Here's your weekly science and technology digest courtesy of +Mark Bruce.

#ScienceSunday   #SciSunCB  
SciTech #ScienceSunday Digest - 09/2015.
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DNA nanotubes, Injected hydrogels, Super atomic bonds, Quicker multicore chips, DeepMind plays games, DNA minicircle applications, Optogenetic pain control, Superatom superconductors, 5G at 1Tbps, New agricultural tools. 

1. Self-Assembled DNA Nanotubes
Continuing the development and evolution of DNA origami techniques we saw the demonstration of a new method of directed DNA self-assembly to produce DNA nanotubes The new method adds modular block subunits iteratively, results in fewer errors, and by incorporating fluorescent tags the group were able to observe the addition of successive blocks to the nanotube. The prototype DNA nanotubes constructed with the technique reached about 20 units, or 450nm in length. I imagine such structures being used as atomically precise scaffolding in future. 

2. Drug Delivery via Injected Self-Healing Hydrogel
A new self-healing hydrogel comprised of a mesh of nanoparticles and polymer strands can be implanted into patients simply by injecting through a syringe Such gels might carry one or more drugs at a time that are released at a controlled rate over a defined period of time; the prototype performed successfully in mice and released both a hydrophobic and hydrophilic drug over several days. I’d also be interested to see if such a gel could be loaded with functional cells - either bacterial or modified versions of the patients own - and protect such cells from the immune system as they respond to the environment and produce useful biochemical factors.

3. Confirmation of Metastable Innershell Molecular States
Metastable Innershell Molecular States were a theoretical prediction of short-lived molecules formed by high-energy collisions and bound together by deep electrons in the inner, as opposed to outer, shell or orbital. Bond strengths for these short-lived molecules are up to 1,000 times stronger and lengths 100 times shorter than normal molecules, and their dissociation would produce high-energy X-rays New work seems to confirm that these entities do in fact exist Possible future applications include high intensity X-rays, advanced lithography, superexplosives, and inertial fusion.

4. Boosting the Speed of Muticore Chips
A new scheduling technique distributes data and computation throughout multicore chips with such efficiency that a test 64 core chip realised a computational speed increase of 46% and a power consumption decrease of 36% The advance addresses problems in communication and memory access in increasingly parallel systems by trying to co-locate data and the associated computation. That’s a pretty decent contribution; one piece of work from one team produces the equivalent of an additional full year of Moore’s Law type increases. 

5. Google DeepMind Learns to Play Many More Games
Originally demonstrating the ability to independently learn to play and master a couple of very simple computer games, the team behind Google-acquired DeepMind has successfully developed the system further to the point where it has now taught itself to play and master a much wider range of more complex 1980s Atari games The system, known as a deep Q-network, the result of the evolution of deep learning techniques, and running on a single GPU-equipped desktop computer achieved impressive results in the games. The team next hope to address requirements for sophisticated exploration and long-term planning, and plan to move onto games from the 1990s. 

6. Cancer Detection and Cell Manipulation with DNA Minicircles
DNA minicircles ( are short plasmid derivatives about 4,000 basepairs long able to function as transgenic elements to get DNA inside cells, but lack bacterial DNA and so less likely to be recognised as foreign, and can also be made to replicate or not (and degrade) in the host cell. By injecting into mice DNA minicircles (in a carrier), that encode a gene only active during embryonic development, and controlled by a promoter region that is only active during embryonic development and in most (all?) cancer cells (never in healthy adult cells), researchers have caused mice with cancer (but not those without) to express a protein that can be easily detected in blood within two days to diagnose the presence and approximate amount of cancer Other applications include producing fluorescent proteins to image cancer cells directly, using different elements able to respond & manipulate different cells behaviour in different ways, and ideally via oral delivery. 

7. Controlling Pain via Optogenetics
By shining specific wavelengths of light onto the anterior cingulate cortex of mice brains modified by optogenetics (certain neurons producing light-sensitive channel proteins) researchers were able to controllably stimulate inhibitory neurons to drastically reduce the experience of pain for the mice This was far more effective than electrode-based stimulation, which leads to activation of both inhibitory and excitatory neurons involved in these circuits. The group has also built up considerable expertise in near-infrared two-photon stimulation to allow deeper and more precise targeting and activation of optogenetically modified neurons. 

8. Superconductivity in Superatoms
Superatoms ( made of a homogenous cluster of aluminium have been found to form cooper-pairs and superconduct at a temperature of 100 Kelvin Contrast this to bulk aluminium, which superconducts at 1 Kelvin. Another impressive feat demonstrated by the group was the ability to construct superatoms with a defined number of atoms, from 32 all the way up to 95 atoms and to precisely probe the electron energy levels of each. The hope is that further research on other types of elemental superatoms might reveal far higher superconducting temperatures, always striving for room temperature, and fabricating tracks of connected superatoms on circuits might enable nanoscale superconducting paths for a range of applications. See also superatom crystals

9. 5G Cellphone Speeds of 1 Terabit per Second
New prototype wireless transmitters and receivers were demonstrated for future 5G networks that successfully facilitated data transfers of 1 terabit per second over a distance of 100m The group ultimately hope to bring the end-to-end latency of the system down below one millisecond. This compared to Ofcom, which hopes to have 5G networks offering 50 Gpbs across the UK by 2020. 

10. A Trio of Agricultural Developments
There were a few interesting agricultural projects this week. First, vertical farming continues to spring up around the world with a new facility next to a Wyoming parking lot called Vertical Harvest able to produce 37,000 pounds of greens, 4,400 pounds of herbs, and 44,000 pounds of tomatoes Second, we saw a new beehive design called the Flow Hive demonstrated that automatically extracts honey via tap without disturbing the bees Finally, new company Afforestt offers a new system for regrowing forests that can produce a mature forest in just ten years

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Convenient Conversions

+Richard Green gives us a helpful reminder that the scale you use does matter when decide to tell your family and friends how extremely cold (or hot) it is this weekend!

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A matter of scale

I'm not usually much of a fan of the Fahrenheit scale, but as this graphic illustrates, it does produce convenient numbers for the purposes of discussing the weather.

(Image credit unknown; Googling it produces many hits.)


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+Randall Lee Reetz I hope you are 1 in a billion, because you doesn't seem like a nice guy. But you did a pretty good job in showing what kind of people who are using F°. And know I'm proud to say that I'm using C°. 😊
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Alzheimer's Amplified

+E.E. Giorgi explains how gene amplification can give rise to the deadly amyloid plaques associated with Alzeimer's Disease in this #ScienceSunday  blog post.

A fascinating study the looks at one of the possible causes of Alzheimer's: not mutations, rather gene copy number... Did you know our brain is a genetic mosaic?

For +ScienceSunday with thanks to +Rajini Rao , +Buddhini Samarasinghe , +Allison Sekuler and +Robby Bowles 
I've tackled the problem of the missing heritability in the past, i.e. the fact that despite all the research on genetic studies and disease associations, we can explain only a small fraction of cancers and disorders. Today we know a lot more than what we knew back when the human genome project ...
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"Did you know our brain is a genetic mosaic?"
No I didn't - that's fascinating!
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SciTech Digest 15 Feb 2015
Thanks as always, +Mark Bruce for your #ScienceSunday  contribution.
SciTech #ScienceSunday Digest - 07/2015.
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CRISPR via light, Volume graphene production, Spot the robot, Printed DNA hydrogels, Implanted artificial organs, Printing via spinnerets, Scanadu tricorder, Prosthetic arms, Contact lens telescope, GMO apple approval. 

1. Light-Induced CRISPR for Custom Tissue Architectures 
By attaching light sensitive proteins from plants to a specific CRISPR sequence and to gene activation proteins a new controlled gene regulation system has been engineered that enables any desired gene to be switched on and off by simply shining light of a particular wavelength onto the cell The proof-of-concept showed a dish of cells expressing fluorescent proteins only on those areas that had been exposed to light. Future applications include light-induced control over the variable differentiation of stem cell cultures to facilitate better and more realistic tissue engineering, or even skin-based cell therapies that allow you to activate a particular pathway at will.

2. Towards Volume Production of Graphene
An alteration to conventional chemical vapour deposition techniques has resulted in a new method to enable the scalable production of graphene sheets The key insight was simply to grow the graphene on a copper oxide substrate; the process of removing or decoupling the graphene from this substrate preserves the graphene structure and properties and circumvents the risks of breakage or contamination. In related graphene fabrication news, 3D printing of complex 3D graphene-based structures is being facilitated by better graphene-loaded inks

3. Spot, by Boston Dynamics
Leading robotics company Boston Dynamics showed off a new mid-size quadruped robot weighing 160 lbs called Spot this week Smaller but faster and more agile than its big brother Big Dog, Spot is battery powered and actuated by hydraulics, and can recover quickly from even severe knocks - as can be seen in the embedded video and which will test your anthropomorphic tendencies. In other robotics news new flying drone designs prove almost indestructible in most situations

4. 3D Printed Self-Assembled Hydrogel Structures
Complementary DNA strands loaded into a gel enable the gel to carry live cells and be 3D printed into custom structures The complementary DNA self-assembles to impart the mechanical characteristics of the gel, which can be altered as needed by changing the sequence of DNA; this self-assembly obviates the need for high temperatures and so better facilitates the handling of live cells through a print nozzle for tissue engineering applications. In other biological self-assembly news the self-assembled protein coats some microbes use to protect themselves is offering insights for engineering artificial variants for a range of purposes

5. Artificial Organs in Implantable Capsules
Pancreatic precursor cells loaded into a flexible, biocompatible mesh capsule that blocks white blood cells but allows the passage of nutrients, oxygen, waste products, proteins, and secreted factors, successfully treats diabetes in animals for long periods of time and has already been implanted into one person to kick off clinical trials The device was developed by Viacyte and they aren’t the only group developing similar technologies; future work will improve the life of the device and create full differentiated islet cells rather than a mix. It’s fascinating to think how the function of artificial organs can be provided in this way, or even other custom biological functions perhaps; combined with the light-induced CRISPR you could have a subdermal patch that you switch on when needed to pump out some enzyme like alcohol dehydrogenase for example. 

6. Robotic Bio-Mimicking Spinnerets for Amazing 3D Printing
A new 3D printer demonstration combines a robotic arm and an innovative 3D printer that includes multiple dynamically moving print heads that each continuously extrude print filament in a system that mimics a spider’s spinnerets extruding silk fibres The machine can extrude or “print” custom 3D fibres or structures, suspended in space, on the go and results in fibres comprising an internal core fibre surrounded by three looping fibres that help convey structural strength and flexibility. Check out the video; it’s pretty amazing. Think of this attached to a mobile robot or mobile swarm of robots. 

7. Scanadu Personal Medical “Tricorder” Ships
Starting out as a successful Indiegogo crowd-funding project Scanadu has finally launched and shipped their Scout product, a small round device that is held to the forehead and very quickly sends readings to your smartphone with measurements of heart rate, temperature, blood pressure, oxygen level, and ECG Early users will help with real world calibration and testing and if the measurements are confirmed as accurate (an FDA submission is also in the works) then this would be a pretty powerful consumer device and one I’d definitely buy. They are also working on a “Scanaflo” product, intended to be a urine test kit for measuring  wide range of metabolic factors.

8. Prosthetic Arms by DARPA & OSRF
DARPA and its partners including the Open Source Robotics Foundation continue to develop advanced prosthetic arms and hands for amputees In a couple of recent demonstrations of the ongoing work we can see a man using a prosthetic arm to climb a rock wall, while other amputees use the prosthetic arms to pick grapes, spoon-feed themselves, “hand” objects between each other, pour drinks into glasses and other feats. The ultimate goal of the program is to create artificial limbs that behave like, are controlled like, and for the user feel like, a normal biological arm. 

9. Telescope in a Contact Lens
Another DARPA collaboration, this time with the EPFL, has resulted in the production of a new type of contact lens embedded with thin aluminium mirrors that, in conjunction with a pair of LCD glasses function as a telescopic lens Light passing through the LCD in one polarisation appears normal and conveys normal vision, but switch the LCD to produce a different polarisation that interacts with the contact lens and the result is telescopic magnification. Future work will improve the oxygen permeability of the lens for greater eye comfort and perhaps seek incorporate the switchable liquid crystal elements directly. 

10. Genetically Modified Apples Approved by Regulators
For the first time genetically engineered apples have been granted regulatory approval by the US Department of Agriculture The genetic modifications are pretty simple, and involve altering the activity levels of a particular gene / enzyme to ensure the apples will greatly resist browning when cut or dropped. I can only hope that this paves the way for greater varieties and greater numbers of different GM foods that convey a range of different nutritional benefits such as more vitamins, etc as opposed to the usual pesticide resistance that we usually see with staple crops. 

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DSCOVR: Deep Space Climate Observatory

+Ciro Villa updates us on an upcoming mission that will orbit between Earth and the sun. The spacecraft will observe and provide advanced warning of particles and magnetic fields emitted by the sun. While it was unable to be launched today, hopefully it'll be on its way to L1 tomorrow.

#ScienceSunday   #SciSunCB  
Journey to L1 Lagrange!

Introducing:  The Deep Space Climate Observatory

In a little bit more than 3 and 1/2 hours as of this writing, NASA in conjunction with the National Oceanic Space Administration (NOAA) will launch a very important satellite mission on-board of a SPACEX Falcon 9 Rocket.

This exciting mission will allow for the positioning of the Satellite at a very vintage point to be able to provide observations and advanced warning of particles and magnetic fields emitted by the sun (known as the solar wind) which can affect power grids, communications systems, and satellites close to Earth.

The mission profile calls for an initial parking orbit of close to 190 kilometers in Altitude.  Afterward the satellite fairing spacecraft will engage to travel to the vicinity of the L1 Sun - Earth Lagrange Point at a distance of approximately 1,241,000 Kilometers from Earth!  The L1 Lagrange point is located at about 1,500,000 Kilometers, this is more than four times the distance to the Moon!

The satellite is expected to reach the L1 Lagrange point after  110 days of space travel after launch!

Follow the live launch at -->
Also learn all about the mission at -->
Press kit here -->
Learn about the L1 point here -->

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Dust in the Wind
Thanks +Jonah Miller for an excellent follow up on BICEP2. For those who missed +Brian Koberlein's post about a year ago, look here.

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The BICEP2 Result Was Just Dust, and That’s Okay

(If you would like to read this post in blog form, you can do so here:

You may remember that about this time last year [1], there was a big hullabaloo because a research group from Harvard [2] claimed that they had discovered primordial gravitational waves using BICEP2, their telescope in the South Pole [3]. This was very exciting because, if true, the result would be extremely good evidence for a model of the early universe called cosmic inflation [4]. (Cosmic inflation is mostly accepted by the scientific community, but it has some philosophical problems and is thus still a little bit controversial [5]. The BICEP2 results would have ended the controversy once and for all.) Even better, the precise strength of the primordial gravitational waves measured by BICEP2 was much greater than anyone had expected, implying that there might be some exciting new things we could learn by studying them further.

Unfortunately, the BICEP2 team’s results were quickly called into question. A competing, space-based experiment, Planck [6], released some of their own data [7] indicating that what the BICEP2 team had observed was simply cosmic dust [8]. But the analysis wasn’t definitive [9]. The jury was still out.

The beautiful thing about science, though, is that scientists collaborate. The BICEP2 team and the Planck team got together, shared data, and worked through a joint analysis of their measurements. This analysis took several months, but it’s finally been released [10].

Now we know definitively. The BICEP2 measurement was indeed cosmic dust, not primordial gravitational waves. But the jury is still out on the existence of primordial gravitational waves. It’s just that, if they exist—I personally think they probably do—then they’re as weak as (or weaker than) we originally thought, not as strong as the BICEP2 measurement indicated.

But why did BICEP2 get such a strong false positive? How did their measurement go so wrong? Well, hold on to your hats, ladies and gentlemen, because I’m going to explain.

This is a follow up to my post from last March on the BICEP2 result (see: If you haven’t read that yet, I suggest you go check it out before continuing.

A Much-Too-Short Summary of Cosmic Inflation and the CMB

About 13.8 billion years ago, the universe was extremely hot, so hot that matter couldn’t form at all… it was just a chaotic soup of charged particles. Hot things (and accelerating charges) glow. And this hot soup was glowing incredibly brightly. As time passed, the universe expanded and cooled, but this glow remained, bathing all of time and space in light.

(The reason for why the universe was so hot in the first place depends on whether cosmic inflation is true. Either it’s because the Big Bang just happened or it’s because, after cosmic inflation, a particle called the inflaton dumped all of its energy into creating hot matter.)

Even today, the glow remains, filling the universe. As the universe expanded, the glow dimmed and its light changed colors (due to gravitational redshift, see:, until it became microwaves instead of visible or ultraviolet light. This ubiquitous glow is called the Cosmic Microwave Background [11], or CMB for short, and if you turn an old analogue TV to an unused channel, some of the static you hear is CMB radiation picked up by your TV antenna [12].

Since its discovery, the CMB has been one of our most powerful probes of cosmology. It lets us accurately measure how fast the universe is expanding [13], the relative amounts of normal stuff vs dark energy and dark matter [14], how the density of matter fluctuated in the early universe [15], how the Earth is moving with respect to the rest of the universe [16] and much more.

Measuring the CMB

One amazing thing about the CMB is that all of the light that reaches us is the same color, to an incredible degree. However, the color does fluctuate a little bit…in a special way that’s independent of position in the sky or direction. These tiny deviations from the norm are primarily what we’d like to measure.

So how does a measurement work? How can we measure something that’s literally everywhere? On Earth, we can see things in three dimensions because we have two eyes separated from each other. But on the scale of the CMB, which fills the entire universe, the whole Earth looks like a single eye–in other words, from our perspective, the sky is two-dimensional.

This means we observe all of the light from the CMB as if it were projected onto a spherical screen above our heads, as shown in Figure 2. Looking from the outside in, the result is something like Figure 3, which plots the wavelength of the light across the sky. (The differences in the wavelengths have been enhanced by about a factor of a million.)

Of course, although three-dimensional models are easiest to visualize, they’re not great to actually work with. So we usually map the CMB onto a flat surface, the same way we map the Earth. This is what gives rise to the famous “all-sky” maps like the one shown in Figure 4.

There’s a lot of information hidden in Figure 4 that you can’t see unless you do some serious math. In fact, you could learn almost everything I’ve told you so far just from looking at the CMB! And there’s more to learn as we make new and increasingly precise measurements.

Planck Vs. BICEP

It’s at this point that I need to provide a clarifying comparison. The images I just showed you were generated by the Planck satellite, which is a small satellite that lives just beyond the moon’s orbit. As Planck orbits the Earth (and as the Earth orbits the sun), it makes measurements of the CMB in small segments of the sky. Over the course of a year, it can build up a map of the CMB in the entire sky, as shown in Figures 3 and 4. (Planck also takes measurements of several different wavelengths of light and aggregates the data. This is important and I’ll get back to that.)

BICEP2 (shown in Figure 5),  on the other hand, is a single telescope near the South Pole. The BICEP2 people chose to measure a small patch of the sky extremely precisely and they only measured one wavelength of CMB light.

What Went Wrong?

If sending a satellite into space or pointing a telescope at the sky were all that was required to precisely measure the CMB, the BICEP2 team never would have mistaken dust for gravitational waves. So what went wrong?

Well, I told you that the fluctuations in the CMB are very very small. This means that they can be drowned out by the many other sources of microwaves in the universe. Jupiter, the sun,  black holes, pulsars, cosmic dust…tons of things produce microwaves. Collectively, all this other stuff is called foreground.

To screen out the foreground, cosmologists build an extremely detailed map of non-CMB sources of microwave radiation in they sky, called a mask, and subtract it from the map of microwave light that the instrument actually measured. After the subtraction, you get something like Figure 4. The mask used to remove known sources in the Milky Way is shown in Figure 6.

But mask-making is tricky business. To build a map, cosmologists use previous measurements of the sky and computer simulations. The Planck collaboration uses an additional trick: they can detect several different wavelengths of microwaves. The only microwave source that will look the same in every wavelength is the CMB, so by comparing the measurements in different wavelengths, Planck can remove unexpected sources of noise.

But BICEP2 only measured one wavelength of light, and this is what killed it. The computer models the BICEP2 people used to make a mask for their little corner of sky didn’t predict that it contained as much spinning cosmic dust as it does. Planck, with their multi-wavelength detector, wasn’t fooled in the same way.

(I should emphasize that the BICEP2 team’s mask was flawed. The team based their dust estimates on older measurements and made a mistake when estimating how much the radiation from the dust would change when you looked at a different color of light. But these are subtle errors, and having several colors of light to look at would have been a fail-safe against them.)

BICEP2 Didn’t Do Anything Wrong

It’s tempting to say that the BICEP2 collaboration failed in some way—their data analysis was poor, they designed their experiment badly, etc. But they couldn’t have known that this cosmic dust would have been a problem. It’s easy to see what to do in hindsight…not so much when you’re planning a multimillion-dollar project years (or even decades) in advance.

This is how science is done. We make a prediction, we design an experiment, we measure something in the world, and we invariably mess up. But by keeping our minds open to our own fallibility, we give ourselves the opportunity to try again and eventually get it right. That’s what happened here. BICEP2 reached an erroneous conclusion, took the opportunity to collaborate with Planck, and they figured it out.

That’s fantastic. That’s what I call science.

(Parenthetical note. There are other ways that the BICEP2 team deserves criticism. Before submitting their article to peer review, the team held a huge press conference and generated a lot of publicity. Given that the conclusion wasn’t yet vetted by the scientific community, this kind of behaviour can and probably did detract from the credibility of science in the public’s eye.)


Thanks to Alexandra Fresch for proof-reading and editing and thanks to Sara Simon for making sure I get the cosmology right.

Further Reading

1. If you’d like to read the joint Planck-BICEP2 press release, you can find it here. In the press release, there’s an link to the scientific paper that the two collaborations wrote together, which is currently undergoing peer review.

2. Planck periodically releases their measurements and statistical tools, including software, masks, and all-sky maps, to the scientific community at large. This is where I got the galaxy mask I showed. If you’d like to browse, you can find all the data and documentation explaining how to use it here.

3. If you’re very brave, you can read this review paper on how foregrounds are removed from CMB measurements. This article describes in great detail how masks are generated.

4. If you want to look at the CMB in its full spherical glory, Damien P. George created this webapp. It’s pretty awesome.

Related Reading

1. This article is a follow-up to my previous article on BICEP2, which you can find here.

2. If you’d like to know how we know that the universe is expanding, you might want to check out my article on exactly that.

If you’re confused about the Big Bang or this whole “inflation” thing, you might want to check out my three-part series on the early universe:

1. In the first article, I describe the evidence for the Big Bang.

2. In the second article, I describe problems with the Big Bang theory.

3. And in the third article, I describe cosmic inflation and how it fixes the problems we had with the Big Bang.


#Science #Cosmology #plancksatellite #bicep2 #astrophysics #ScienceEveryDay #scienceeveryday

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The Stern-Gerlach Experiment

Do subatomic particles behave like little magnets? Well, sort of. +Jonah Miller gives a great explanation of the Stern-Gerlach experiment and the quantum phenomenon of spin.

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Spin and the Stern-Gerlach Experiment

The word “quantum” means a single share or portion [1]. In quantum mechanics, this means that energy comes in discrete chunks, or quanta, rather than a continuous flow. But it also means that particles have other properties that are discrete in a way that’s deeply counterintuitive. Today. for +ScienceSunday I want to tell you about one such property, called spin, and the experiment that discovered it: the Stern-Gerlach experiment.

(Those who wish to see this post in blog form can find it here:

(The goal of the original experiment was actually to test something else. But it was revealed later, after the discovery of spin by Wolfgang Pauli, that this is in fact what Stern and Gerlach were measuring [2].)


The Stern-Gerlach experiment involves magnetic fields. So before I tell you about the experiment itself, I need to quickly review some of the properties of magnets.

As you probably remember, the north pole of a magnet is attracted to the south pole of other magnets and repelled from their north pole, and vice versa—a south pole is attracted to north poles and repelled by other south poles. In other words, opposites attract.

Suppose we generate a very strong magnetic field (say, with a very big magnet or with a solenoid [3]) and put a small magnet in the field, as shown in Figure 2. What happens to it? The north pole of the big magnet will attract the south pole of the small magnet, and the south pole of the big magnet will attract the north pole of the small magnet. Since the north and south pole of the big magnet are are equally strong, these attractions will be equal and opposite, and they’ll cancel each other out so that the little magnet feels no net force. As a result, it doesn’t move up or down—it just hovers in place.

Now suppose we create a big magnet whose north pole is more powerful than its south pole, as shown in Figure 3. (It’s not actually possible to make a magnet with a stronger north pole than south pole. However, we can create the same effect by using multiple smaller magnets.) What happens now?

To answer this question, we must understand that the strength of a magnetic force depends on the distance between the interacting poles; the closer the poles, the stronger the force. This means that the net force the little magnet feels depends on its orientation, as shown in Figure 4. If the south pole of the little magnet is close to the north pole of the big magnet, the little magnet will be pulled upwards. If, on the other hand, the north pole of the little magnet is close to the north pole of the big magnet, the little magnet will be pushed downwards. If the poles of the little magnet are the same distance from the poles of the big magnet, the little magnet will feel no force. And of course, anything in between is possible. A little magnet whose south pole is just barely closer to the big north pole will feel a weaker pull than a little magnet whose south pole is very close to the big north pole.

The Stern-Gerlach Experiment

The Stern-Gerlach experiment, performed by Otto Stern and Walther Gerlach, tested whether subatomic particles behaved like little magnets. To do this, Stern and Gerlach created a magnet with a bigger north pole than south, just like the one described above, and shot a beam of electrons with random orientations through the resulting magnetic field. If electrons behaved like little magnets, then the beam would be spread out by the magnetic field, as shown in Figure 5. Some electrons would be pulled upwards, some would be pushed downwards, and some wouldn’t change direction, depending on the orientations of the individual electrons. But if electrons didn’t behave like magnets, then none of them would be affected by the magnetic field, so they would all just fly straight through.

Surprisingly, although the electrons were affected by the magnet, they didn’t spread out as in Figure 5. Instead, the electrons split cleanly into two beams, as shown in Figure 6.

That’s very weird! It implies that electrons behave like little magnets, but only sort of. A magnet can be oriented any way it likes. But an electron can only have two orientations: either aligned with the big magnet or aligned against it. So the electron can travel up or down, but it can’t stay in between. This is a distinctly quantum phenomenon—the electrons behave like magnets fixed into a pair of discrete orientations, or states, as opposed to a continuum of possible orientations. An electron’s spin is what describes which of those two states it’s in.

Where Does Spin Come From?

I won’t discuss it in detail here, but we can understand spin as emerging from the structure of the underlying quantum field theory that describes the behavior of a given particle. For those of you who know the lingo, it has to do with whether the underlying field is a vector or scalar field, and how large that vector is. (Among other sources, see_ Quantum Field Theory in a Nutshell_ by Anthony Zee.)


The Stern-Gerlach experiment reveals a dramatic difference between the quantum world and the world we’re used to. It’s not possible for a particle to have any old orientation; it must be oriented either with the external magnetic field or against it.

But what if there is no external magnetic field? How is the particle oriented? Somehow the act of measuring the system changed how it behaves, or at least how we perceive it. These are questions that physicists struggled with in the early twentieth century as quantum mechanics was being discovered. Indeed, to some extent, physicists are still struggling with them.

In the next few weeks, I’ll address some of these issues. Next time, I will talk about an extension of the Stern-Gerlach experiment that helps us explore, if not answer, some of these questions.

Related Reading

This is only the latest in a number of articles that I’ve written about quantum mechanics. For example, I wrote a three-part introduction to the field:

1. In the first part, I describe some of the experiments that first revealed particle-wave duality:

2. In the second part, I use the Bohr Model of the atom to explain how packets of energy emerge from the wave nature of matter:

3. In the third part, I describe how we can interpret matter waves as probability waves:

More recently, I wrote a pair of posts exploring particle-wave duality.

1. In the first post, I describe how a particle can be constructed from a wave:

2. In the second post, I show how particles sometimes can’t exist:

I’ve also written a number of stand-alone articles on quantum mechanics:

1. Quantum mechanics uses complex numbers, so I wrote a short explanation of imaginary and complex numbers here:

2. I explain the Feynman path integral, which is a way of understanding quantum mechanics, here:

3. I use particle-wave duality and matter waves to explain quantum tunneling here:

4. I use quantum mechanics to describe how atoms form covalent bonds here:

Further Reading

Here are some additional resources on the Stern-Gerlach experment:

1. If you’d like to learn a bit about the history of the Stern-Gerlach experiment, try “Stern and Gerlach: How a Bad Cigar Helped Reorient Atomic Physics.” See:

2. One of the finest technical write-ups of the Stern-Gerlach experiment is in the opening chapter of Modern Quantum Mechanics by Sakurai. Excellent and detailed, but definitely not for the faint of heart. See:

3. There is a free textbook-like write-up of the Stern-Gerlach experiment by Jeremy Bernstein here:


Thanks as always to +Alexandra Fresch  for her line-editing.

Recently I’ve had a lot of discussions on G+  about the interpretation of quantum mechanics. (In particular, I’ve spent a lot of time talking to +Charles Filipponi  and +David R .) This article was partly inspired by those conversations. Thanks, guys!

The Winnower

I'm trying an experiment. I've cross-posted this post to the Winnower, which is an open-access academic journal. Recently, the Winnower reached out to me and suggested that I cross-post my blog posts there. If you're curious, please check it out and let me know what you think.  You can find the link here:



#ScienceSunday   #Science   #Physics   #QuantumMechanics   #HistoryOfPhysics  
+Allison Sekuler +Rajini Rao +Chad Haney +Buddhini Samarasinghe +Aubrey Francisco +Carissa Braun +Buddhini Samarasinghe 
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Weekly SciTech

Here's your weekly science and technology digest courtesy of +Mark Bruce.

#ScienceSunday   #SciSunCB  
SciTech #ScienceSunday Digest - 08/2015.
Permalink here:

Autonomous atom assembly, Auto face detection, Human epigenome map, DNA data storage, UberBlox modular tools, Ultrasound vs brain barrier, Strong limpet teeth, Measuring synaptic transmission, Early cancer tests, Silicon nanofiber batteries. 

1. Autonomous Assembly of Atoms into Nanostructures
NIST researchers have developed a new system that enables the computer-controlled autonomous assembly of individual atoms into precisely defined nanostructures on a copper surface using a scanning tunnelling microscope The system first scans the surface to determine the precise locations of the atoms available for assembly, calculates the coordinate transformations necessary to move the atoms to new locations, then instructs the STM tip to move the atoms as desired. As a possible application the group quote the production of tailored quantum states for information processing and nanophotonics.

2. Face Detection Algorithms at Human Performance Levels
Deep Sense Face Detector is a new face detection algorithm, built on a deep convolutional neural network, that is able to quickly and accurately spot human faces at any angle and orientation in an image, even when partially occluded Key applications of course include image search and robotics, particularly robotic interaction with humans. Such detection capabilities combined with ever-better face recognition capabilities provide a glimpse into the near-future capabilities we’ll have for searching for people through both personal images and surveillance footage. In related news software is being developed to determine where a video was shot based based on the scenery and ambient sound

3. First Human Epigenome Map
A map of the human epigenome has been generated for the first time, and in the process creating a valuable tool that embodies genomic epigenetic changes, their regulatory effects, and comparisons across a wide range of cell and tissue samples The data generated involved 150 billion sequencing reads and 3,174-fold coverage of the human genome and relied heavily on machine-learning algorithms to translate these massive datasets. The goal here is to understand the dynamic epigenetic code and how it might be manipulated; how it relates to cell and tissue specialisation and gives rise to various traits. 

4. Very Long Term Data Storage via DNA Encoding
Digital data can typically be encoded into DNA for short term applications. But by taking the digitally encoded DNA strands and encapsulating them in silica glass spheres measuring 150 nm researchers created a fossilised storage medium able to potentially preserve the digital information for a million years or more The information is retrieved by breaking down the glass with fluorine chemistry and sequencing the DNA found within, but the key enabling development was the addition and use of error-correction codes to handle the inevitable errors that are present. The proof-of-concept successfully stored and retrieved the Switzerland Federal Charter and an Archimedes text. 

5. UberBlox: Modular Components for Tools and Devices
UberBlox is a new modular construction set and prototyping system with a standard connection and locking mechanism between units and a variety of control systems for computer enabled automation of a wide variety of tools and devices UberBlox can be assembled into a range of devices including 3D printers, laser cutters, CNC millers and routers, manipulator arms, rovers, robots, and all compatible with Arduino, Raspberry Pi, and other systems. Modularity enables familiar standards, ease of use, lower costs, and faster evolution of designs; we just need to reach the point of creating something like an UberBlox that can create more UberBoxes.

6. Applications for Opening the Blood Brain Barrier with Ultrasound
Magnetic resonance imaging has previously been used to guide focused ultrasound to temporarily open the blood brain barrier to allow desired drugs to pass through. In a recent study this technique was used on the hippocampus of animal models of Alzheimers disease, and was found to assist with the reduction of plaques, increase neuronal plasticity, and improve cognition and spatial learning, and all without tissue damage or behavioural changes Early days but with such a relatively simple technique and promising animal results I’m thinking human tests will be good to see. 

7. Limpet Teeth: New Strongest Natural Material
Limpet teeth are made of geothite and recent tests suggest the fibrous structure of this material in limpet teeth may be the strongest known natural material Interestingly the strength of the limpet teeth was found to be somewhat scale-invariant, with the same relative strength over different length scales - a counter-intuitive finding given larger structures tend to have more defects and so less relative strength. Finding a synthetic process to mimic the fabrication of this material on a large scale would have obvious applications across a wide range of areas. 

8. Measuring Synaptic Transmission in Live Animals
For the first time the synaptic transmission between neurons in live animals has been recorded with the aid of optogenetics Using optogenetically engineered mice that produce neurons sensitive to certain wavelengths of light, researchers activated a subset of neurons in the sensory cortex with flashes of blue light while simultaneously using implanted microelectrodes to record electrical signals in neighbouring neurons, and used this to directly observe the activation of one neuron from another. Developing this technique the group showed that synaptic transmission differs depending on the type of neuron receiving the signal, and ultimately hope this can be used to build larger pictures of connectivity between other types of neuron across the brain. 

9. Developing Liquid Biopsies and Early Cancer Tests
A nice overview article gives an update of the rapid development of liquid biopsies and testing for early stage cancers via DNA sequencing a drop of blood from patients The technique, originally developed for testing a drop of a pregnant woman’s blood to sequence DNA determine whether her fetus has Down Syndrome, is now making big strides in testing for the presence of early stage cancers with numerous clinical studies underway. The benefits of such a technique being rolled out would have a profound impact on patients as the prognosis for early, pre-symptomatic, cancer detection is much better. The the rapidly declining cost of DNA sequencing strongly suggests that before too long we might all have a weekly or monthly sequencing test. 

10. Silicon Nanofibers Enable Better Batteries
I don’t often cover battery technologies because they’re announced all the time with usually little result. But this new paper-like material composed of a high-density matrix of silicon nanofibers as an anode for lithium-ion batteries looks quite promising Silicon can pack 10 times the electrical charge per unit weight compared to typical graphite electrodes in lithium-ion batteries and should enable similar-sized batteries with several times the storage capacity. Produced via electrospinning the new material solves existing problems of scalability and volume expansion. Multigram amounts were fabricated for prototyping and testing and the group next plans to fabricate a standard pouch-cell lithium-ion battery for testing with real devices. Doubling or quadrupling lithium-ion battery capacity impacts everything from smartphones to drones to electric vehicles. 

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A little information about water fleas
#ScienceSunday  co-curator +Carissa Braun drops a little science on us about water fleas. Read on about these microcrustaceans.

The Model Microcrustacean

Water fleas are crustaceans of the order Cladocera. In general, these creatures range in sizes of less than 0.5 mm to more than 6 mm with males generally being smaller. Within Cladocera are the planktonic crustaceans of the genus Daphnia which are characterized by their flattened leaf-like legs. Their bodies are enclosed by an uncalcified shell with either five or six limbs on the trunk. In the water they swim with a jumping-like behavior that earned the nickname of water fleas. 

Daphnia are microcrustaceans that can be found in most types of freshwater including permanent and temporary ponds, lakes, and slow moving streams. While mostly pelagic, some are found clinging to plants or browse in the bottom of shallow ponds. They are filter feeders, their prey the small, suspended particles in the water though they mostly consume planktonic algae. Their leaf-like legs are used to produce a water current to collect the particles. They mature fast and serve as an important source of food for fish and other aquatic organisms. There are more than 100 known species of Daphnia that have been studied for more than 250 years. It is a model organism and with good reason.

A model organism is a species that is used to study specific biological phenomena. They are often easy to maintain and breed within a laboratory, and due to being widely studied, have years of accumulated data. Some famous model organisms include house mice, fruit flies, and Escherichia coli. It is through the use of model organisms that phenomena such gene transfer, cell function, and the human disease state are known and explored. Different model organisms have different advantages and disadvantages, and where Daphnia excels is in the use for biomedical research.

Daphnia have a wide distribution in highly diverse habitats resulting in extensive phenotypic diversity. Their reproductive cycle is short, and they are easy to culture. While sexual reproduction can be induced environmentally, reproduction is normally clonal. The close relationship of crustacean and insects allows for a valuable outgroup for comparative genomic studies, an especially important factor when considering the number of model organisms available for understanding genome function and evolution is rapidly expanding in particular in the insect taxa. In short, Daphnia is a versatile model organism to investigate the fundamental mechanisms of inheritance and development, cellular function, physiological systems, immunity response, disease, macromolecular structure/function relationships, and the genetic basis of complex phenotypic traits.

More recently, Daphnia has been used in the field of ecotoxicology. This is looking at environmental change on the biological function. When looking specifically on the different stressors on gene expression with effects observed at a population level, Daphnia has been proven useful. While a more involved technique such as microarray can be used, the simple transparent nature of Daphnia allows for flexibility and other investigation such as conducting bioassays using other endpoints than death.

While they may be small, Daphnia play a large role in life. They are an important part of the food web and an important part of research. For a short-lived creature, their contributions are long lasting.

This is a significantly more detailed version of the blog post from Thursday (though I could have expanded more in certain sections), but the blog post on Thursday did include two pictures that I have not uploaded here if you are interested. The link is below.

For your #ScienceSunday , and in relation to that, check out this earlier post by +ScienceSunday for an incredibly close shot of Daphnia playing with volvox:

Sources and Further Reading
Introduction to Daphnia Biology (NCBI: website)
Model Organisms for Biomedical Research: Daphnia (NIH: website)
Model Organisms in the Study of Development and Disease (UCSD: pdf)
Molecular and Population Stress Responses in Daphnia magna (University of Reading: website)
Toxicology: Daphnia (Cornell: website)
Water fleas: Daphnia (Original Blog Post)
Water fleas prepared for trip to space (article/website)
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Just a little. I didn't want to drown anyone in science (kind of works). Thanks, Chad!
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Set the Controls for the Heart of the Sun

For #ScienceSunday  , here is a wonderful post that explains the cosmic radiation that filled the early universe. 

The Universe Is an Inside-Out Star

No, not really. But as we’ll see, it’s a useful analogy. Today for +ScienceSunday we’ll learn about sound waves in the sun and how, if we imagine that the universe is the sun but inside-out, these are the same as the sound waves that filled the early universe.

(If you would like to read this post in blog form see:

Sound Waves in the Sun

I’m sure you won’t be surprised when I say that the sun is a complicated beast. A nuclear furnace burning at tens of millions of degrees powers a burning ball of turbulent hydrogen gas and plasma. All sorts of crazy things happen in the sun. Magnetic fields reconnect and plasma flows on the surface, neutrinos fly out of the nuclear reaction in the core, et cetera. But let’s ignore all that for now. Let’s say that the sun is “just” a gigantic ball of superheated hydrogen gas.

But hydrogen gas is… well, a gas. And if something makes a noise, sound can travel through it. Moreover, how the sound travels,  and the frequencies that make up the sound, can tell us a lot about the interior of the sun. Fortunately for us, lots of things in the sun make sound. For example, if a bit of gas is hotter than its surroundings, it will create a pressure wave through the sun. And this pressure wave is nothing more than a sound wave.

But if we want to use these sound waves to understand the interior of the sun, we have to measure them. How on Earth do we measure sound in the sun?

Wiggles Beget Wiggles

Fortunately, we don’t need to measure the sound waves directly. All we need to do is measure the color of the light coming off the surface of the sun. A sound wave is just a fluctuation in the velocity of the particles that make up a gas. So, as a sound wave reaches the surface of the sun (called the photosphere), it will accelerate the atoms in that area. This in turn slightly changes the color of the light these atoms emit, thanks to something called the Doppler effect. (I’ve spoken about the Doppler effect before in the context of the expanding universe. See: Atoms moving toward us emit light that is more blue than it otherwise would be, while atoms moving away emit light that is more red. Since not all light coming from the sun is emitted at the surface, the change in the color of the sunlight that reaches us is small but measurable.

Therefore, all we have to do is look at the surface of the sun and measure the changes in the color of the light emitted from different points on the solar surface. These changes in color correspond to the peaks and troughs of a sound wave traveling through the sun. The scientific field that studies the sun’s interior using the color fluctuations on its surface goes by the awesome name of helioseismology.

The Universe

So what does all of this have to do with universe at large? Well, as I’ve remarked before, we know that the early universe was filled with an extremely hot plasma—so hot that atoms and molecules couldn’t form. And this plasma glowed incredibly brightly. As the universe expanded and cooled, atoms and molecules formed, but the glow remained. It still remains today in the form of a bath of microwave radiation filling the universe, which we call the cosmic microwave background, or CMB for short.

That’s one way to look at things. But there’s another way, too.

Looking Back in Time

The speed of light is finite. Indeed, it’s the speed limit of the universe. This means that the light from a star four lightyears away from us is four years old. In other words, when we look out into space, we look into the past. And greater distances take us further back in time.

As we peer away from Earth, things are mostly empty for a while. Stars and galaxies are incredibly far apart, after all. But eventually we peer far enough away, into the extreme past, that we see the hot plasma of the early universe. The plasma is opaque, though, so we can’t see inside it. What we can see is the point when the plasma cools enough for atoms to form. The distance at which we see this happen is called the surface of last scattering. The corresponding time in the history of the universe is called recombination.

Since we can’t see inside the plasma, it might seem impossible for us to learn what happened before recombination. But it’s plausible that the plasma fluctuated and moved… and maybe sound waves even traveled through it. Fortunately, we can measure that! The fluctuations in the pre-recombination plasma change the color of the light in the cosmic microwave background!

And now we’re at the punchline. One way to understand this is to imagine that the universe is an inside-out version of the sun, as shown in the figure. As we look away from the Earth, backwards in time, there’s empty space. Then we reach the surface of the universe-sun, which is nothing more than the surface of last scattering. Behind it is the plasma which makes up the interior of the universe-sun. The sound waves in the interior change how the atoms and molecules on the surface (the surface of last scattering) move and thus change the color of light that’s emitted and eventually reaches us!

And thus, by measuring the fluctuations in the CMB, we can measure the dynamics of the very early universe!

The Big Bang Wasn’t a Point

One thing I like about this analogy is that it takes the center of the sun, which is a single point, and smears it out so that it becomes the surface of a very large sphere, one with the same radius as the observable universe. I like this because it reverses a common misconception.

People usually imagine that the Big Bang, the beginning of the universe, was  a single point from which everything emerged. This is completely wrong. The beginning of the universe happened about fourteen billion years ago at every point in space. So, in our inside-out sun analogy, the smeared stellar center is the Big Bang.

(Of course, there may not have been a Big Bang if, for example, cosmic inflation is correct. But that’s a story for another time.)

Related Reading

What I described in this post is a weird and crazy way of looking at the cosmic microwave background. But I’ve discussed the more “standard” understanding of the CMB several times. Most recently, I described the nitty-gritty of how cosmologists measure the CMB and how this is related to the failed BICEP2 “primordial gravitational waves” measurement. See:

I also wrote a three-part series on the early universe:

1. In the first post, I describe how the cosmic microwave background helped convince scientists of the existence of the Big Bang:

2. In the second post, I describe some problems with the Big Bang theory:

3. Finally, in the third post, I describe how the model of cosmic inflation fixes the problems with the Big Bang:

Further Reading

1. This post is inspired by—and borrows heavily from—a scientific paper by Crowe, Moss, and Scott. It’s very readable, even for the layperson, so I recommend checking it out if you’re interested. You can read it for free at:

2. Astrophysicist +Brian Koberlein  has a beautiful (pun intended!) blog post on how we probe the interior of the sun, in which he describes helioseismology and some other techniques. You should definitely check it out:

3. There’s a nice piece in Scientific American on the CMB here:

+Robby Bowles +Rajini Rao +Allison Sekuler +Buddhini Samarasinghe +Aubrey Francisco +Carissa Braun 

#physics   #astrophysics   #cosmology   #helioseismology   #sound   #sun   #ScienceSunday  
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Tasks for the Threatened

Sections of land and sea are often set aside in an effort of conservation and with hopes of protecting threatened and endangered species, but as +Sam Andrews explains, it isn't always so easy and sometimes well intentions still fall short.

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Australia’s protected area network fails to adequately protect the world’s most threatened marine fishes

Australia has, compared to some other countries, a fairly extensive network of both marine and terrestrial protected areas.  On the marine side there is of course the Great Barrier Reef Marine Park and more recently the implementation of the Commonwealth Marine Reserve network.  The idea behind any marine protected area is to offer long term “conservation of nature with associated ecosystem services and cultural values”, so one would expect to see some effective protection going on in these areas…right?  Areas chosen, and cared for to ensure they offer conservation value, to do all we can to help keep species going that have suffered population declines because of our actions?  I’m sure many of you won’t be surprised to hear that this isn’t always the case.  Take a look at some of my previous posts – here, here, and here for example.  Unfortunately, as highlighted in a recent study by Karen Devitt, who was based at +Charles Darwin University, Australia’s protected areas are inadequate for protecting one of the world’s most threatened marine fishes – the sawfish.

There are 5 species of sawfish (Pristidae) in the world.  In a previous study focusing on sawfish (, +Nick Dulvy and fellow researchers reported that the group, which can occupy marine, brackish, and fresh water habitats at different stages in their life cycle, are probably “the world's most imperilled marine fishes”.  Three of the five species – smalltooth sawfish (Pristis pectinata), largetooth sawfish (Pristis pristis), and green sawfish (Pristis zijsron) are classified on the +IUCN, International Union for Conservation of Nature Red List as critically endangered.  The remaining two species – narrow sawfish (Anoxypristis cuspidate), and dwarf sawfish (Pristis clavata) are classified as endangered.   Out of the five species of sawfish, only the smalltooth is not found in Australian waters.  More so, northern Australia is home to “some of the few remaining viable sawfish populations” in the world.  Looking after these guys isn’t just important for the Australian population of sawfish, but for the global population of sawfish.  Northern Australia’s waters is in fact, globally significant.  If northern Australia’s populations decline, then the outlook is extremely bleak for these rather unusual looking fish.

One of the key steps Karen and fellow collaborators undertook was to accurately map the range of each of the sawfish species in Australia.  They had to do this themselves because only very coarse range maps had been produced from limited data.  Sounds silly doesn’t it – a seriously threatened species, and we don’t even really know where it lives.  Understanding ranges is (rather obviously) crucial for implementing effective protected areas for these guys.  After all, a protected area situated over very little or even none of their habitats is rather pointless.  The team managed to obtain a number of records of each species that they could confidently use in their analysis.  They also used the known habitat preference of each of the 4 species and maps of Australia’s land (for the freshwater habitats they use) and sea-scapes to figure out what the most likely ranges of these endangered critters are.  Of the 2,908 records of narrow sawfish, 741 records of green sawfish, 247 records of dwarf sawfish, and 470 of large sawfish, a total of 524 records were taken within a protected area.  The percentage of range protected was also low.  For their inland (freshwater) range, between ~9 and 17% had some protection designation attached.  Their marine ranges fared a little better – around 22 – 44% some protection.  

But there is something else to consider.  Not all protected areas afford equal protection.  The IUCN has a range of different categories for both terrestrial and marine protected areas.  In a marine context, at the upper end you have strong protection like areas you can’t extract things from – fishing and mining is banned.  At the lower ends you have sustainable use zones, which allow (hopefully) carefully managed activities to take place.  This can include things like fishing or mining.  When you are dealing with a species – or indeed a group of species like the sawfishes that are living in a very precarious position, ideally you want the protected areas to offer them the strongest protection possible.  Alas this is not so.  Karen and colleagues maps showed that most of the protected areas (terrestrial and marine) that covered the sawfishes ranges were sustainable use zones – zones in which activities known to be a direct threat to sawfish still take place.  What’s more, the team also note that the Commonwealth Marine Reserve network may not be all it is cracked up to be, with the current Australian Government, elected in 2013, suspending the management plans for the network.  In reality, the little protection the sawfish were supposed to be afforded by the network may be significantly eroded.   

There was one final issue that the team raised in their paper – that of connectivity.  It is becoming well understood by scientists (if not politicians) that marine protected areas cannot function as single isolated islands.  Many species undertake dispersal at some time or another – the larvae of sessile organisms can travel on currents to new settlement sites for example.  Some species – like sawfishes – can travel large distances, utilizing different habitats.  An effective marine protected area may very well need to be included inside a network, and that network needs to consider how critters move around, and how in reality seemingly disconnected sites are in fact connected.  Female largetooth and dwarf sawfish for example both pup in estuaries.  Their juveniles live in freshwater and riverine habitats.  It is only when they are older that they head out into the ocean.  These seemingly disparate but essential habitats for the sawfish (and indeed many other species) has not been considered in network design.  The urgency to consider connectivity is heightened by proposals to develop hydroelectric dams in northern Australia, something that has the potential to block migrations of these critters.  

In terms of size, Australia’s terrestrial and marine protected areas may be making advances in achieving targets set by the international community, but they are far from achieving any meaningful contribution towards species like sawfishes which so desperately need help. 

The paper which was published in Global Ecology and Conservation has been made open access.  You can have a read of it here

Image:  An x-ray of the small tooth sawfish (Pristis pectinate) taken by Sandra Raredon at the +Smithsonian, National Museum of Natural History.   You can see some other fantastic x-rays Sandra took, and read a how and why she did it over at the Smithsonian website here 

#marineconservation #marinescience #sciencesunday #marineprotectedarea #mpa #sawfish #openaccess
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Space Images from +Michael Interbartolo, 8 Feb 2015
Thanks for sharing #ScienceSunday  +Michael Interbartolo.

This Week In Cool Space Images Feb 6th 2015
Planck shows us the Milky Way
ESO looks into the Mouth of the Beast
Dawn Approached Ceres
Young Terraces on Mercury
HiRISE spots Curiosity from Orbit
Epimetheus looks so small by the rings of Saturn
3 Jovian moons parade across the gas giant's face
have a great weekend
#thisweekincoolspaceimages   #scienceeveryday  
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