All posts by Debjyoti Bardhan

Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.

Scientists Create First Light Controlled Nano-Switch

The drive to make faster and faster computers just got a huge optical jump! University of Pennsylvania researchers have made a quantum leap in designing new-age gates for use in new age computers. These gates are controlled by light!

Computers of today are made out of gates that are switched on and off by electrical signals. The crucial speed involved in the switching speeds of these gates is the velocity at which electrons (or other charge carriers) travel inside the substrate that make up the gate. In other words, how fast you can switch a gate on and then off and then on again depends on how fast the electrons feel the changing electric field and travel back and forth. All of this can be greatly accelerated if we use light signals and not electric ones!

Light Switches!

So here is the first photonic switch, all made out of cadmium sulphide nanowires. The team of researchers consists of an associate professor Ritesh Agarwal and graduate student Brian Piccione, from the Department of Material Sciences, Pennsylvania University.

They are carrying forward their earlier research finding, when they found that cadmium sulphide (CdS) nanowires is the perfect substance on which to attempt such a thing. Cadmium sulphide exhibits very strong light-matter coupling. This simply means that there exist mechanisms within the substrate that can control the way light behaves within the material.

How they did it

What they did was cut a gap in a CdS nanowire. Light was then shone on one of the sections. This light is perfectly transmitted down the length of the nanowire. Now, the team shone another light on the second part of the nanowire. This, believe it or not, cuts off the light that was already going through the nanowire. This phenomenon is called destructive interference. So now, you have a gate which you can turn on or off by shining light on the second part. All you need to do, in principle, is to measure the intensity of light coming out the second part of the wire.

And that’s it!

This is a basic switch. With switches you can make gates. With gates you can design a computer.

One of the basic types of gates is the so called NAND (Not AND) gate. The NAND gate can be used to construct any other gate. A NAND gate returns a high signal (‘1’) if either or both of the inputs is zero, and zero if both inputs are one. The team has built such a device using two CdS nanowires.

The paper appears in Nature Nanoscience:

Forget Big Bang! The Universe Might Have Begun With Big Freeze

The Universe didn’t start off with a big bang, but a big whimper. Or so say four physicists from the University of Melbourne and RMIT. They compare the beginning of the Universe with that of freezing of water, indicating that the Universe underwent a rapid phase transition. Before you think this is the next big theory, all set to replace the Big Bang as the new standard cosmological theory, hold on!

Did the Universe just freeze out?

Crystallizing out the Universe

Lead researcher of the group, James Quach, says that the early Universe can be compared with a liquid – something which has no particular shape or form. This liquid froze, “crystallizing” into three spatial and one temporal (time) dimension. In a slightly more technical language, consider a crystal lattice forming as a result of some parameter – say temperature – varying from high to low. As the temperature lowers, the lower energy states of the crystal become more and more important. Quach and his group say that these low energy states form the spatial degrees of freedom of the Universe. They herald in a new theory called ‘quantum graphity’.

The stimulus behind the theory proposal is very simple: dissatisfaction. Physicists are unsure as to how the bang in the Big Bang happened. More precisely, the structure of space-time thought to exist at the time of the Big Bang requires a modern theory of quantum gravity. Basically, Einstein’s equations of general relativity and quantum mechanics cannot be reconciled and this creates the problem. Right now, we have no satisfactory theory of quantum gravity.

Do away with it, says the group. Imagine the Universe as a group of dynamical space-time blocks, like small crystalline blocks floating around in a liquid. As the temperature cools, the blocks coalesce and this gives rise to a bigger crystal, simulating the freezing out of space-time from an existing soup.


But what about anisotropy and the visible structure in the Universe? Here is where the water-freezing analogy comes in most handy. When water freezes into ice, cracks develop on the surface. Quach and team describe these cracks as some visible structure. Problem is that they aren’t sure what scale to look at and this scale varies all the way from the microscopic to the ultra macroscopic.

All of this sounds fine and dandy, except that this new model must explain or, better predict, the data seen by the various cosmological experiments. Right now, the group doesn’t seem to have the right scale in mind. More problems arise from asking the question where did the soup that crystallized come from?

The work appears in Physical Review D here:

Cliodynamics: Treating History As Science and Why That’s a Bad Idea

Often it has happened in the course of history and it might just repeat itself. Ironically. A beautiful idea it is, but like many before it, it might be completely wrong.

Cliodynamics is the name of this strange game, the game of detecting cycles in history and then using this data to predict the occurrence of similar events in the near future. Named after the Greek muse of history, Clio, and championed by a population dynamics expert at the University of Connecticut, Peter Turchin, Cliodynamics is fast making itself noticeable. Its claim of making future events predictable using the past events has drawn a small crop of believers and a larger group of dissidents. Fear not, it doesn’t use crystal balls; the choice of tools is limited to historical data and complex mathematics. The idea: find patterns in recurrent events and extrapolate into the future.

The endless loop

Where I stand

Personally, I belong to the dissident side. I don’t believe that it can work, but, just for the sake of convincing you, I’ll be the angel’s messenger rather than the devil’s advocate. Let me try, as hard as I can, to convince you that Cliodynamics is a genuinely scientific deal. I can always bash it up after that’s done!

The immediate question is how one can paint the whole tapestry of history – and what’s coming up – with such a broad brush! But that’s exactly what Cliodynamics is promising to cure. Right now, the reasons for collapse of large empires – pick one, say the Roman Empire – are all fuzzy. Various scenarios have been proposed. No one knows for sure. Cliodynamics wants to correct this vague outlook by introducing mathematical models backed up by solid data and then predictions ought to be made using this. History should be “predictive science”, says Peter Turchin, who was studying predator-prey problems in the wild, when he had an idea and turned his expertise in the area towards more sociological models.

On to the numbers

Turchin and a few advocates analyse the long-term trends in society using four parameters – population numbers, social structure, state strength and political instability. The dicey bit is to put proper numbers for these quantities. For abstract quantities like this, the definition is crucial, as that determines the measurement procedure. Often, however, a clear-cut definition is not available. Let’s just gloss over this point for the moment, being sure to return to it later on.

The general trend seems to be that a period of political instability, often accompanied by a period of violence, is preceded by a spell of increase in corruption and unpredictable political alliances or rise of unforeseen groups. While this is a broad trend, the challenge is to actually look into the details and come up with definitive correlations, positive or negative, between trends and the events.

But this is exactly how a historian is supposed to work – how is Turchin’s work different?

Endless Cycles of history

With the help of Sergey Nefedov of the Institute of History and Archeology, Yekaterinburg, Russia, Turchin found two independent cycles, which seem to define the course of history. One is called  the ‘Secular Cycle’ and the other one is the ‘father-and-son’ cycle.

Endless loops? (A Lorentz Attractor)

The Secular cycle lasts for a long time – sometimes as long as 200 to 300 years. Large empires grow, labour laws evolve, elitism escalates and political power transfers hands over this large timescales. Many events appear to be at play and each influences the outcome of history in their own way. Even religions can rise, fall and rise again according to the secular cycle.

The shorter cycle is the ‘father-son’ cycle, which lasts about 50-60 years, i.e. about two generations. An individual – the father – revolts against the working of the society or the class of which he is a member and the son bears the brunt of the backlash in a subdued fashion, relegated to the background by the thought that the opposing forces are too strong to fight back against.

Suspected: Insects Undergoing Some Kind of Photosynthesis

The gardener’s nightmare might be the entomologist’s goldmine. Among the most destructive of all insects are small sap-sucking critters, called Aphids. They are very populous, reproducing via both sexual and asexual means, and are difficult to eliminate using pesticides. Aphids are also colored insects. They generally have a green color, but can also acquire a red color as they can also synthesize red carotenoids (pigment proteins). They are the only animals known to be able to synthesize pigments.

Aphids (Photo Courtesy: University of California)

A process similar to photosynthesis

What wasn’t known was that aphids can actually use these pigments to metabolize using sunlight, much the same way that plants do! Yes, aphids can undergo a process similar to photosynthesis in plants, finds a group of researchers.

This startling finding is due to a group working under entomologist Alain Robichon at the Sophia Agrobiotech Institute in Sophia Antipolis, France. The group worked with green, orange and white aphids. White aphids are found where resources are scarce and they are almost completely devoid of pigments. Green aphids are found in places with cold temperatures, but still enough food to go around.

Counting ATP

The group measured the ATP levels in the aphid bodies. ATP is the ‘energy currency’ of the living organism – this is the molecule that is transferred between cells when an energy transfer has to occur. The results of the measurements were astounding: Carotenoid rich green aphids registered a much higher level than the white carotenoid-devoid ones, suggesting that the green pigment might be instrumental in providing another source of energy production.

Look at the two lines. They represent the optical density (OD), indicative of the ATP/metabolic activity of the pigment. Clearly the green pigment (represented by the solid black line) has higher absorption at all wavelengths.

Moreover, when the orange aphids – containing moderate amounts of carotenoids – were placed in sunlight, they showed intermediate levels of ATP. Interesting. Very interesting indeed.

Not the photosynthesis we know

One has to note that this ‘photosynthesis’ merely refers to the use of sunlight in order to gain energy. This doesn’t refer to the photosynthetic process that goes on in plants, which require the transfer of a positive charge from a water molecule, leading to the expulsion of oxygen (and thus we breathe!). Also, carbon dioxide has not been shown to be essential to the aphids version of the photosynthetic process.

The carotenoid molecules are placed about 0-40 micrometers deep under the cuticle, making them perfect to capture both the incident and the transmitted solar radiation.

Questions, questions

But questions remain – why should the aphids need to synthesize? As mentioned above, aphids in high food resource areas develop strong pigmentation and can also synthesize food for themselves. But doesn’t that defeat the very purpose? Why make when you already have food?

Both the mechanism and the necessity are unclear. These tiny critters had an unknown ace up their sleeves and there might be more.

The paper:

On Film: Picking the World’s Most Haunting Photos

There are images which speak a million words — or which simply shut you up. Some shake you to the core and some just leaves you with a feeling that you’ve never experienced before and perhaps never will again. Photography — that wordless medium of expression. Photography — that capture of a moment of reality that you might never have otherwise noticed. Photography — a medium that you’ll fall back on when words simply run out!

On the occasion of World Photography Day, I present a compilation of 14 photos that have presented to me a different facet of life, in either some obscure part of the world or somewhere quite familiar. The characters are supreme; the personal touch can warm your heart; the impersonal can horrify you; all of this will definitely imprint themselves on your mind.

Click on any of the photos to reveal a bigger version, alongwith a short description.

Inception in Real Life: Scientists Figure Out How To Hack The Human Brain

Even Nolan didn’t think it could be possible when he made Inception, but it turns out that researchers at Usenix Security conference have been speaking of using a computer interface to hack the brain! Yes, it might actually be possible to enter the brain and retrieve information that you’d prefer to keep secret. Like retrieving a combination key to a safe that your dying father might have given you and you have it stored somewhere in the subconscious.

Reading the Mind

The idea is simply this: have your brain mapped by sensors (here, an EEG or Electroencephalograph is used), which pick up crucial brain activity and then sophisticated software can help understand what it is that the brain is trying to do! These are called ‘brain-computer interfaces’ (or BCI’s) for obvious reasons.

These can actually help you mentally control your computer using specific thought patterns.

The BCI from Emotiv technologies.
Controlling a video game using BCI

Machine over Mind

What is interesting is how a computer can browse through your mental database and steal away some pieces of sensitive information. Security researchers from the Universities of Oxford and Geneva and University of California, Berkeley have developed a program to be used by the software that has only one purpose – finding information like home address, debit card PIN and date of birth. They found 28 willing participants, who didn’t know about the hacking (of course, otherwise the whole exercise is futile, right?) and tested this program on them. The success rate varied from a mere 10% to a respectable 40% for different fields of sensitive data.

The four experiments

The technique is a lot like hacking passwords. The key response tracked by the program is known as a P300 response – the brainwave activity that the brain undergoes when it recognizes something familiar, like a known face, own neighbourhood, own debit card PIN and so on! The peaks in the P300 activity were noted and the analysis of this data can give a very good indication of what the right answers are!

The P300 activity. Notice the black peak indicating a high for the target stimulus
The EEG results for a target and a non-target stimulus

Future thoughts – You might know them already!

Yes, cool, innovative and scary! Imagine the chaos which will ensue if the bank manager is kidnapped and crucial information is extracted from his brain using these kinds of hacking techniques. How can a big bank cope with that threat in the not-so-far future? What about the fear of malware – say you use the BCIs to control devices, but some pop-ups show you some random numbers and your P300 activity indicates that this might actually be your PIN? How do you protect yourself against that? The only viable option seems to be to not think about it, but then that is, believe it or not, the hardest thing to do!

Maybe, militarizing your subconscious is the only way to go. Don’t be scared to dream a bit bigger – and a bit weirder.

All pictures taken from the paper below.


LHC Experiment Sets Record For The Hottest Substance Ever Created!

The sky is no longer the limit — the limit lies deep within sub-atomic particles. After the glory of the Higgs discovery, the LHC has now set a record for obtaining the hottest temperature mankind has ever seen. The trick — make a hot enough quark-gluon plasma.

The ALICE detector

At the center of this achievement lies the less talked about detector ALICE (short for A Large Ion Collider Experiment). We get to hear about the CMS and ATLAS detectors, since these are dedicated to the Higgs boson search and its subsequent measurement. The ALICE detector is a heavy-ion detector. Heavy ions, i.e. ions with very high atomic numbers and weights, like Gold and Lead, are collided at high energies. The end products are then analysed.

What the hell is QGP?

The generic end product is quark-gluon plasma (QGP), a soup of quarks, which are building blocks of protons and neutrons, and the so-called gluon particles. This is regarded as another form of matter and this was indeed the state of the Universe just moments after the Big Bang! In QGP, matter behaves like a perfect fluid, with no drag or friction.

Numbers, just for the record

Now, for the record you need numbers. The earlier record was set again by a QGP factory called the Brookhaven National Laboratory and the temperature they attained was a whopping 4-trillion degrees!! That’s a 4 followed by 12 zeroes!

ALICE isn’t quite sure of its figures yet, but the energy to temperature conversion should indicate temperature of close to 5.5 trillion degrees! But the ALICE collaboration wants a few days in order figure out the actual numbers.

The ALICE experiment is colliding beams of lead ions, but the collision between unlike heavy ions is a likely possibility for the future. That will be important to know the dependence of the parameters of the resulting fireball on the geometry of the colliding particles.

Mystery of the Floating Pumice Island Solved!

It was really an underwater volcanic eruption, but then that was already known. What wasn’t known was which underwater vent it was that caused this huge pumice spread. Samples were taken from the unusual island and analysed. Now, a source has been identified.

We reported the news here:

The floating island of pumice.

One suspect ruled out, another implicated

Many volcanologists have suggested that an active seamount, the Monowai seamount, erupting along the Kermadec arc was responsible for the huge emission of the light rock. The problem is with the alibi – the island was reportedly spotted as early as 1st of August by an airline pilot, while Monowai erupted only on the 3rd of August. Ruling out time travel, the only logical explanation seems to be another source, a bit farther away.

The offender has been pinpointed as the Havre Seamount, says volcanologist Erik Klemetti, assistant professor of geosciences at Denison University. The data going into this analysis comprises pictures from the Moderate Resolution Imagine Spectrometer (MODIS) aboard the Terra and Aqua satellites and accurate depth mapping of the seabed. Ocean bathymetry, or seafloor topography, maps out the physical features of the seafloor. An erupting underwater volcano is like a new pimple on the face of the seafloor.

How they did it

The seafloor map revealed a volcanic plume and the MODIS images from the 19th of July revealed high ash content in the water and also some pumice in and around the Havre seamount. The MODIS thermal images from a day, taken at 10:50 PM, before revealed a lot of heat in the region, indicating that the volcano was erupting. The eruption was strong enough to breach the surface in under 12 hours, which means penetrating a column of water more than a kilometer in height.

The Havre seamount activity receded around the 21st of July, but, by then, it left off enough pumice residues to create the huge island that was seen.

First hand look

But people are still not satisfied. They want to view the Havre eruption first hand, after going down to the seafloor in a research vessel and photographing the area.

It has been speculated that such underwater vents spewing out pumice can be responsible for replenishing the pumice content in the coral reefs around the world.

Mysterious Island of Pumice Spotted on the South Pacific

Sheets of pumice forming a giant floating island have been spotted in the South Pacific. The size of the island is larger than the entire area of Israel. The whole island is 480 kilometers in length and about 50 kilometers in width. The New Zealand Royal Air Force spotted the floating pumice raft southwest of Raoul Island.

A screenshot from the youtube video uploaded by the NZ Air Force (see below) Courtesy: Youtube

Pumice and how it forms

Pumice is made from lava which cools off too fast. The trapped air pockets in the rocks makes it both porous and buoyant. An underwater volcano could’ve created this gigantic pumice island. A possible candidate is the Monowai seamount, along the Kermadec arc which has been active in recent times. The sheet reportedly looked like a giant floating icesheet.

Samples of the pumice float have been collected by at least two research groups, one of them being Australian government supported. These will help answer the question as to where these come from.

Here is a Youtube video uploaded by the New Zealand Royal Air Force:

How pumice is related to the very origin of life

Interestingly, pumice rocks and pumice sheets are not just an interesting artifact. They might be vital to life on the planet as we know it! Pumice rocks could’ve provided nice habitat for early Earth microbes. They could cling on these and populate themselves.

Further, chunks of pumice could’ve ferried animals across vast stretches of water, maybe hop islands! Remote islands could’ve been seeded like this, which then evolved uniquely, giving rise to insular populations of animals not seen anywhere else in the world. So pumice may have been the substrate on which life formed and also a mode of transport for developed life forms!

Yes, science does hold a lot more mysteries than dreamt of in your philosophy, my Horatio!

Plate Tectonics on Mars!

Mars is more similar to Earth than you might think! For one, Mars also has tectonic motion, says a UCLA scientist. Yes, there are tectonic plates on Mars that move, create huge gorges and also develop prominent fault lines, just like they do on Earth. But then, they are not as similar as a naïve generalization might suggest.

Prof. An Yin, professor of Earth and space sciences explains why:

Mars is at a primitive stage of plate tectonics. It gives us glimpse of how the early Earth may have looked and may help us understand how plate tectonics began on Earth.

Deeper and Longer than anything else!

At the center of his research, lies the huge canyon between two regions, called the Valles Marineris (Latin for “Valley of Mariner”, after the Mariner Mars craft). With vertical cliffs, jagged rocks and a length of nearly 2500 km – about 9 times that of the Grand Canyon here on Earth – this is clearly a geologic goldmine! How did it form?

The central part of the Valles Marineris (Courtesy: Google)

Yin argues that the forces at play are the familiar forces which generate steep cliffs here on Earth, namely the tectonic forces. The Valles Marineris, he argues, is actually a fault line and the forces have pushed up and submerged rocks, just like in Death Valley, California, which was also formed by tectonic action. And just for records of the superlatives, this is the deepest and longest canyon known in the Solar System.


The plates on Mars number just two, as compared to seven on Earth. They also move much slower than their terrestrial cousins. Mars being about half the size of Earth explains this slow motion – the initial ball of molten material was much more stable and there was less thermal energy to drive the whole process, which would’ve fragmented the crust even further. However, Yin thinks that the planet is on its way to becoming more fractured.

What About Mars-quakes?

Slow movement between plates and just one stable fault line means that Mars-quakes are way less frequent than earthquakes. The rate of movement hasn’t been ascertained – it’s just that it’s slow! Yin, who uses data obtained from the satellite images taken by the THermal Emission Imagine System (THEMIS) aboard the Mars Odyssey spacecraft and also from the High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO), thinks more data collected in the next year or so will help in answering these questions.

Prof. Yin’s paper is set to appear in the journal Lithosphere soon.