Back in early May, I interviewed experts on dispersants and oil spill clean up and wrote “Out of Sight: BP’s dispersants are toxic — but not as toxic as dispersed oil.”

Chemically dispersing oil spills “solves the political problem of visible oil but not the environmental problem,” Robert Brulle, a 20-year Coast Guard veteran and an affiliate professor of public health at Drexel University, told me. These dispersants “do not actually reduce the total amount of oil entering the environment,” as a 2005 National Academy of Sciences report on the subject put it.  Nobody has any idea what will be the impact of massive exposure to these toxic chemicals on organisms that live on the bottom or feed off the bottom of the ocean.

In short: out of sight, out of mind. But not out of the body of marine life.

The dispersants seem to have done their job — and keeping oil off sensitive coastal habitats is a very good thing.  But some in the media seem to have confused not seeing oil with not being harmed by it.

In fact, as Science reports, “Oil Contamination of Crab Larvae Could Be Widespread“:

Researchers have found droplets of oil inside crab larvae in the Gulf of Mexico. Although preliminary, the findings represent the first sign of hydrocarbons from the Deepwater Horizon well entering the food web.

Wonk Room’s Brad Johnson has more on the premature declaration of “Mission Accomplished”:

In a contrarian take today, Time Magazine’s Michael Grunwald wrote a preemptive post-mortem impact of BP’s Deepwater Horizon disaster, saying that it “does not seem to be inflicting severe environmental damage. Grunwald believes that Rush Limbaugh “has a point” because the right-wing radio host spent weeks dismissing the disaster. New York Times reporters Justin Gillis and Campbell Robertson wrote that the “oil slick in the Gulf of Mexico appears to be dissolving far more rapidly than anyone expected.” The Associated Press’s John Carey believes “the oil slicks that once spread across thousands of miles of the Gulf of Mexico have largely disappeared.” The narrative of the disappearing disaster has been promoted by Politico’s Mike Allen and the Drudge Report.

Meanwhile, the oil blowout has been contained but not killed, oil continues to wash ashore, and the haphazard scientific effort to understand the 100-day disaster is hobbled by BP’s interference and governmental lassitude. It’s fair to point out, as Grunwald does, that the oil disaster’s impact on Louisiana’s shoreline is likely to be meaningless if the marshlands continue to disappear. Fringe rumors of global eco-collapse — never promoted by major environmental groups — continue to be as baseless as the nonsense spouted by conservative activists, media, and politicians on behalf of the oil industry.

However, the only honest take on the BP disaster right now is that this is a calamity, the true scope of which will take years to discover, with many impacts impossible to ever know. No one knows how badly this disaster will affect the dying marshlands of Louisiana. No one knows how badly the toxic oil plumes will affect the spawning grounds of the bluefin tuna, the feeding grounds of the threatened Gulf sturgeon, or the future of the endangered Kemp’s ridley sea turtles, whose corpses have been found at 15 times the historical rate this summer. No one knows what the long-term physical and mental health impacts will be on the tens of thousands of cleanup workers.

Moreover, it is undoubtedly premature to announce that the vast oil slick has largely disappeared from the ocean’s surface. Thick oil, vast slicks, and tar balls continue to wash ashore along Louisiana’s coastline. Satellite imagery from July 27 and 28 — as the stories of disappearing oil were being filed — show a vast region still discolored by slicks and sheen, little diminished from previous weeks:

At the Gulf Restoration Network, Matthew Preusch reports that scientists like George Crozier, executive director of the University of South Alabama’s Dauphin Island Sea Lab, are deeply concerned about the undersea dispersed oil:

“A lot of our eggs and larvae are in the top 100 meters, so as this cloud of toxins spreads upward, we’re making an assumption that its killing all of them,” he said. “I absolutely hate the use of dispersants at depth. I think that was the most huge of mistake in the process of containment.”  Last week, a group of prominent marine researchers released a statement calling for the end of the use of dispersants in the Gulf, saying, “Corexit dispersants, in combination with crude oil, pose grave health risks to marine life and human health.”

This article was originally posted on Climate Progress

by Richard Obousy

Physicist Richard Obousy here takes a look at an intriguing new paper by Mike McCulloch, a researcher at the University of Exeter. In addition to his work in theoretical physics and warp drive possibilities, Obousy is current project leader and primary propulsion design lead for Project Icarus, a joint venture between the British Interplanetary Society and the Tau Zero Foundation to re-think the original Project Daedalus starship design. In the review below, Obousy places McCulloch’s work on the Pioneer anomaly in the context of current thinking on dark matter, dark energy and the nature of mass. Does the Higgs field explain inertial mass, or are there alternatives? Read on.

Few areas of research have garnered as much attention from both the public and scientific communities as those of dark energy and dark matter – and for good reason. Both terms stem from observations of the physical universe that, simply put, don’t belong within the well-understood framework of known physics. Another phenomenon discovered in the nineties concerns an anomalous acceleration of the Pioneer probes. These ostensibly unrelated observations may, in fact, be connected to each other by an intriguing line of research currently being investigated by Mike McCulloch, a researcher at the University of Exeter. Before exploring McCulloch’s research, a brief review of dark energy, dark matter, and the anomalous Pioneer acceleration will be presented.

Dark matter is a proposal put forward to explain the observations first made by Zwicky in 1933 that galaxies were too energetic to be held together by observable matter. Zwicky originally proposed the existence of an unseen form of baryonic matter that provided the necessary gravitational force to hold the galaxies together. Due to constraints imposed by modern cosmology, the idea has evolved to assume this form of matter is non-baryonic (not made of quarks); however, the fundamental idea has remained unchanged. After decades of searching for dark matter, none has been directly detected, but a number of experiments are ongoing.

Dark energy stems from the truly astounding observation made originally by Riese and Perlmutter in the late 90′s that the rate of cosmological expansion, long thought to be either static or decelerating, is actually accelerating. For this to be happening, it is commonly believed that the universe is filled with a ubiquitous and exotic negative pressure field that drives the accelerated expansion. Although we can give this energy a name, and predict what it will do, dark energy as a ‘real’ physical field has never actually been measured in the lab, and today, dark energy remains somewhat of an enigma.

As if dark energy and dark matter haven’t dealt theoreticians enough of a blow, cracks began to appear in our understanding of gravity due to the observation made by Anderson et al in 1996 that both Pioneer 10 and 11 are experiencing an anomalous acceleration of 8.74±1.33×10^-10 m/s² directed approximately towards the sun. It is precisely this anomaly that is studied by Mike McCulloch in his recent publication in Europhysics Letters called Minimum Accelerations from Quantized Inertia (reference below). McCulloch’s work addresses the Pioneer anomaly, and within the framework of his model, one could perhaps come to a deeper understanding of dark matter and dark energy thanks to a novel idea known as MOND, or Modified Newtonian Gravity.

The basic idea that McCulloch explores is the nature of mass, and the possibility that inertial mass, in fact, changes slightly under certain conditions. It has been known since the time of Newton that all bodies attract all other bodies in the universe with a force that is proportional to their mass. This type of mass is what is known as gravitational mass. It is also known that when one applies a force to an object, it accelerates at a magnitude that is proportional to its mass. This type of mass is known as inertial mass. It is commonly assumed that gravitational and inertial mass are identical, and this has been verified by our highest precision instruments to date.

The fundamental nature of inertial mass is not precisely known and is an issue that has been pondered at least since the time of Mach. Recent efforts to codify inertial mass into the Standard Model (SM) of particle physics have resulted in the famous Higgs field, which is a ubiquitous field that bestows mass upon matter via a process known as spontaneous symmetry breaking. Although the Higgs field has not been experimentally detected, many physicists are confident that it will be found at the Large Hadron Collider.

Despite the widespread acceptance in the existence of the Higgs field, there have been alternative attempts to uncover the nature of inertial mass. One paper, Inertia as a Zero Point Lorentz Force, written in 1994 by Rueda, Puthoff and Haisch (RPH), represents a stalwart effort to model inertia as a back-reaction of matter to the quantum vacuum similar to the Unruh field. Despite not gaining widespread acceptance in the theoretical community, the paper galvanized interest in the possibility that the quantum vacuum and inertial mass may be related. The basic premise of the paper was that matter, modeled as a ‘Parton’, interacts with the quantum vacuum in such a way that any acceleration generates a Lorentz-type back-reaction to the vacuum which manifests itself macroscopically as a resistance to acceleration or, more simply, as inertial mass.

The RPH paper was not the first to suggest that accelerated matter is effected by the quantum vacuum. In 1976, Unruh showed that a body undergoing an acceleration in the vacuum sees a thermal radiation of temperature T that is related to its acceleration. Wien’s displacement law tells us that, for a given temperature, there will be a dominant wavelength which, via the Unruh effect, is inversely proportional to the acceleration – namely, as the acceleration gets smaller, the radiation wavelength gets bigger. As the acceleration decreases, this wavelength reaches a limiting value: the wavelength of the observable universe. Milgrom, in 1994, speculated that at this point, there would be a ‘break in the response to the vacuum’ and the Unruh radiation would be unobservable. He further speculated that this could have an effect on inertial mass. Herein lies the crux of this line of thinking – that matter’s response to the vacuum is what generates inertia.

McCulloch further develops the idea of Milgrom by allowing for a more natural development in the Unruh radiation spectrum. In the original idea by Milgrom, only the dominant wavelength was considered. McCulloch, however, develops what he calls a Hubble-Scale Casimir effect, where a range of wavelengths are allowed based on the boundary conditions of the size of the observable universe.

“The new assumption is that this Unruh radiation is subject to a Hubble-scale Casimir effect. This means that only Unruh wavelengths that fit exactly into twice the Hubble scale (harmonics with nodes at the boundaries) are allowed, so that a greater proportion of longer Unruh waves are disallowed, reducing inertia in a new, more gradual, way for low accelerations.”

Using this model, McCulloch is able to develop an equation which illustrates the modification of inertial mass for low accelerations. Put in simpler terms, as the Pioneer probes depart our solar system they experience a force due to the gravitational attraction of the sun. This force generates an acceleration which, due to its extremely small value, modifies the inertial mass of the pioneer probe. Because of this modification, the Pioneer probes, seemingly now less massive, feel a greater acceleration due to the sun than that predicted by Newtonian mechanics, creating the anomalously large acceleration.

How does this all relate to dark energy and dark matter? The answer is in the relationship between certain natural scales that occur in physics. The basic building block is the scale that characterizes the cosmological constant. We call this scale R and it is the distance scale over which the cosmological constant curves the universe. R is about 10 billion light years and is 10⁴⁰ times the size of an atomic nucleus – the scale where the standard model of particle physics is applicable). R is also 10⁶⁰ times the Planck scale – the scale at which we believe in GUT’s (Grand Unified Theories), where all the forces in nature behave identically. It is therefore pragmatic to wonder whether this scale R might be indicative of some new physics.

Hints at new physics at the scale R manifest themselves in the cosmic microwave background (CMB) – thermal radiation left over from the Big Bang. This radiation has been cooling as the universe expands, and is now at a fairly uniform temperature of 2.7 degrees Kelvin. Fluctuations in this temperature exist to a level of a few parts per 100,000, and the patterns of these fluctuations provide us with clues to the physics of the early universe.

Analysis of the temperature fluctuations over the last decades illustrate how much energy is contained in this radiation as a function of wavelength. It appears that the CMB is dominated by a single large peak, followed by a number of smaller peaks. It also appears that there is very little energy in the longest wavelength. This data can be interpreted as indicative of a ‘cutoff’, above which the thermal modes are less excited. What is particularly remarkable is that this cutoff occurs on a scale R which we associate with the cosmological constant.

This cutoff is somewhat puzzling from the perspective of inflation theory, which was developed by Alan Guth of MIT and, originally, by Alexei Starobinsky of the Landau Institute for Theoretical Physics in Moscow. According to the theory of inflation, the early and rapid expansion of the universe created huge regions of the cosmos with relatively uniform properties. This region is thought to be much larger than the observable universe. The cutoff indicates that, at the scale R, inflation stopped just at the point where it created a region as large as we now currently observe. If, in fact, inflation ‘switched off’ just at the point where it created the cosmos as large as we currently observe, then some physical mechanism must have been responsible for selecting this unique time to stop. This seems incredibly improbable, since nothing in the physics of inflation says anything about scales on the order of 10 billion light years.

Said another way, if inflation produced a largely uniform universe, then it likely produced uniformity on scales much larger than we observe. Thus, the patterns produced by inflation, the small fluctuations, should be visible beyond the present size of the universe. Instead – what the data indicate is that these fluctuations stop above the scale R.

Another indication that new physics may occur at scales on the order of R is an apparent asymmetry in the distribution of hot and cold spots in the CMB dubbed the ‘Axis of Evil’. This observation was first made in 2005 by Kate Land and Joao Magueijo of Imperial College London. A number of independent studies have confirmed this apparent alignment of anisotropies in the CMB.

There are additional phenomena associated with the scale R that are worth discussing. One way we can explore R is to combine it with additional constants of nature. An interesting place to start is to combine it with the speed of light, c, to give us R/c. Dimensionally, R/c gives us a time, and that time corresponds to the present age of the universe. Taking the reciprocal of this, c/R, gives a frequency, a profoundly low ‘note’ which has completed one oscillation in the entire lifetime of the universe.

Going one step further, we can explore c²/R which, dimensionally, gives us the units of acceleration. Remarkably, this number is the acceleration produced by the cosmological constant. This is the same acceleration that we currently believe dark energy is responsible for and is on the order of 10^-10 m/s. This also happens to be the roughly the same anomalous acceleration that the Pioneer probes are currently experiencing!

The c²/R also crops up when we examine rotational velocity of orbiting stars in galaxies. Recall that stars are seen to rotate at a velocity that would, according to Newtonian Mechanics, be too fast for them to be held in a stable orbit. The contemporary fix for this problem is to introduce dark matter. This is not the only fix, however. For spiral galaxies, in which stars move in circular orbits, anomalous velocities (orbital velocities that, according to Newtonian Mechanics, should not be possible) are only apparent beyond a certain orbit. Within this ‘special’ orbital distance Newtonian gravity works perfectly. Because stars move in a circular orbit they experience an angular acceleration which is related to their velocity (a=v²/r). The breakdown of Newtonian gravity occurring at this ‘special’ orbital distance occurs when the stars are rotating with an angular acceleration of 1.2×10^-10 m/s², almost identical to the scale c²/R. This is thoroughly fascinating, and this string of relationships which appear to be related to the scale R represent tantalizing hints at physics beyond what is currently studied and practiced within the mainstream academic community.

Today, nobody knows for certain what this new physics is (if it really is new physics), and nobody has written down a theory codifying its behavior. Mike McCulloch, however, is arguably helping to increase momentum within this curious and remarkable area of research.

The paper is McCulloch, “Minimum accelerations from quantised inertia,” Europhysics Letters Vol. 90, No. 2 (20 May, 2010). An abstract is available, with full text here. The paper by Rueda, Haisch and Puthoff is “Inertia as a Zero Point Lorentz Force,” Physical Review A, Vol 49, No 2 (February 1994), pp.678-694.

This article was originally posted on Centauri Dreams

Is it possible to imagine people powering their cellular phone or music/video device while jogging on a sunny day?

A University of Southern California team has produced flexible transparent carbon atom films that may have great potential for a new breed of solar cells.

In a paper recently published in the journal ACS Nano, researchers stated that organic photovoltaic (OPV) cells have been proposed as a way to create low cost energy due to their ease of manufacture, light weight, and compatibility with flexible substrates.

This work shows that graphene, an extremely conductive and highly transparent form of carbon consisting of atoms-thick sheets of carbon atoms, has high possibility to fill this role.

While graphene’s existence has been known for many years, it has only been studied extensively since 2004 because of the impossibility of manufacturing it in high quality and quantity.

The Study

The University of southern California team has produced graphene/polymer sheets ranging in sizes approximately 150 square centimeters that in turn can be used to create dense arrays of flexible organic photovoltaic (OPV) cells.

These organic photovoltaic (OPV) devices convert solar radiation to electricity, although not as efficiently as silicon cells.

The power provided by sunlight on a sunny day is approximately 1,000 watts per meter square, for every 1,000 watts of sunlight that hits a square meter area of the standard silicon solar cell, 14 watts of electricity will be generated, Organic solar cells are less efficient; their conversion rate for that same 1,000 watts of sunlight in the graphene-based solar cell could be only 1.3 watts.

Benefits of OPV

But what graphene organic photovoltaic (OPV) lack in efficiency, can potentially be compensated by its lower price and, greater physical flexibility.

Researchers think that it may eventually be possible to cover with inexpensive solar cell layers extensive areas like newspapers, magazines or power generating clothing.

In the meanwhile Prof. Ruoff and his colleagues of the mechanical engineering department at the University of Texas at Austin, are studying the basic science in the development of graphene-based ultracapacitors for usage in electronics and other fields.

Batteries vs Ultracapacitors

Prof. Ruoff says batteries are relatively slow, they can store energy but require sometime to charge up, and then they distribute energy slowly, over time.

Ultracapacitors can be charged quickly, within seconds, and discharge in a short time, but, right now, they’re not able to store very much electrical energy.

The introduction of stable and less expensive ultracapacitors could be a key step in using wind or solar-generated power, specially if researchers can discover methods to enable capacitors to store energy longer, that is not yet possible.

Current Potential Usage

Even with their current storage capacity, the graphene devices could provide quick energy when needed in certain situations on the ecological way.

They could be used, as an example, to absorb the heat generated in braking an automobile or train, and store it for a short time, and use it for the electrical needs of the vehicle (i.e. starting the car or acceleration).

About the writer – Sophia H. Walker writes for the solar panel battery charger blog, her personal hobby site focused on tips to help individuals save energy using solar power for small devices.

This article was originally posted on Natural Environment.

Robert Forward’s Indistinguishable from Magic is a genial and absorbing read, a collection of essays and fiction illustrating some of the scientist’s most memorable ideas. And while gigantic lightsails driven by laser beam to other stars always come to mind when Forward’s name is mentioned, it’s fascinating to page through his thoughts on antimatter, black holes and time machines. Long a Forward admirer, I was pleased to see that another of the concepts discussed in this book recently made an appearance at this month’s solar sail conference in Brooklyn.

‘Statites’ are a Forward construct, a word he coined to describe a spacecraft that uses a solar sail to hover over a region rather than orbiting the Earth. Let Forward describe what he calls a ‘technique for hanging things in the sky’:

…I have the patent on it — U.S. Patent 5,183,225 “Statite: Spacecraft That Utilizes Light Pressure and Method of Use”… The unique concept described in the patent is to attach a television broadcast or weather surveillance spacecraft to a large highly reflective lightsail, and place the spacecraft over the polar regions of the Earth with the sail tilted so the light pressure from the sunlight reflecting off the lightsail is exactly equal and opposite to the gravity pull of the Earth.

You can see where Forward is going with this. This is a solar sail that isn’t designed for transport but for station-keeping, and it offers options that other kinds of satellite do not. But maybe satellite is the wrong word:

With the gravity pull nullified, the spacecraft will just hover over the polar region, while the Earth spins around underneath it. Since the spacecraft is not in orbit around the Earth, it is technically not a satellite, so I coined the generic term ‘statite’ or ‘-stat’ to describe any sort of non-orbiting spacecraft (such as a ‘weatherstat’ or ‘videostat’ or ‘datastat’).

Forward always noted that he had made no money from his patent, but said he didn’t want to make the mistake Arthur C. Clarke did when he failed to obtain a patent on his idea of the geosynchronous communications satellite. In a short story included in Indistinguishable from Magic called ‘Race to the Pole,’ Forward writes about a statite called the ‘Hovering Hawke’ that uses a kilometers wide square lightsail to support a powerful broadcast satellite. Such a ‘polesitter’ would, by Forward’s calculations, need to be too distant to serve as a communications satellite, but direct broadcast or weather surveillance would be robust applications.

Just how distant would a polesitter have to be? In this passage from the story, a scientist explains the difficulty a statite would experience maintaining a stable position as the Earth’s seasons change:

“The control problem of keeping the [statite] balanced over the pole is very tricky, especially during the summer season of that hemisphere when the polar axis is over on the sunlit side of the Earth. That’s why ‘pole-sitters’ have to be placed so far away from the Earth. If they get any closer than 250 Earth radii, they become unstable during the summer.”

Forward’s patent ran out in February of this year, but his idea is beginning to gain traction. At the Second International Symposium on Solar Sailing, which ended just last week, Colin McInnes described what Forward called ‘displaced orbits’ that would allow geosynchronous telecommunications satellites to be deployed to the north or south of the Earth’s equator. Working with graduate student Shahid Baig, McInnes (University of Strathclyde) has published a new paper that shows the viability of displaced orbits. Says McInnes:

“Satellites generally follow Keplerian Orbits, named after Johannes Kepler – the scientist who helped us understand orbital motion 400 years ago. Once it’s launched, an unpowered satellite will ‘glide’ along a natural Keplerian orbit. However, we have devised families of closed, non-Keplerian orbits, which do not obey the usual laws of orbital motion. Families of these orbits circle the Earth every 24 hours, but are displaced north or south of the Earth’s equator. The pressure from sunlight reflecting off a solar sail can push the satellite above or below geostationary orbit, while also displacing the centre of the orbit behind the Earth slightly, away from the Sun.”

Image: Analog‘s December, 1990 issue contained an article by Robert Forward describing the ‘polesitter’ concept, one of many innovative ideas the scientist introduced to a broad audience. Credit: Condé Nast.

No, we’re not in ‘polesitter’ range, not yet, anyway. But these displaced orbits would allow solar sails — McInnes is interested in hybrid sails complemented by electric propulsion systems — to be displaced between 10 and 50 kilometers from the equator. As we continue our work with solar sails, finding ways to make them robust enough to handle polar stationary orbits seems like a reasonable expectation. Another Forward concept thus moves into sharper definition. I can only imagine how much the late Dr. Forward would have enjoyed sitting in on the relevant session at the solar sail conference, and reading the McInnes paper.

The paper is Baig and McInnes, “Light-Levitated Geostationary Cylindrical Orbits are Feasible,” Journal of Guidance, Control and Dynamics, Vol. 33, No. 3 (2010), pp. 782-793 (preprint). You’ll also enjoy reading the non-fiction piece Robert Forward wrote for Analog. It’s “Polesitters,” published in Analog Science Fiction/Science Fact Vol. 110, No. 13 (December, 1990), pp. 88-94.

This article was originally posted on Centauri Dreams

Powered with Intel’s Core i7 processor and 1GB of NVIDIA graphics goodness this 15.6” laptop ops for the polarising 3D effect and comes bundled with a fetching pair of the cheaper polarised frames. The 3D effect comes from the TriDef software we saw on Lenovo’s recently released IdeaPad Y560d 3D laptop, it converts the 2D images on the go into a 3D image, that when fired through a polarised screen into your Joe 90s the image “comes to life”. The laptop is also capable of HD quality sound and has the option for a Blu-Ray drive.

We have no details on the exact date of release or price but LG have also gone on to say they’re planning a plethora of 3D gadgets, including monitors for PC gaming and even 200” projectors with 3D capabilities.

Post from: Mighty Gadget – Gadget and Technology Blog

LG on the 3D Laptop Bandwagon

Tags: 3D, 3D Laptop, Core i7, LG, LG R590, NVIDIA

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This article was originally posted on Mighty Gadget

My friend Paul Marlier has a pretty fun gig at the Children’s Museum of Pittsburgh. His job as a workshop specialist is to come up with new ways to teach science to children (and their parents!). Recently, he took a few minutes to explain his latest prototype, which is a set of wooden blocks with electronics on them that museum visitors can connect up in any way they like. The idea is that they can learn by trying out different things to see what happens. The blocks themselves are nothing more than squares of plywood with different components stuck to them, and finishing nails for binding posts that can be connected to using alligator clips. To run the activity, he sets them out on the table without instructions, and participants are invited to hook things up and see what happens.

Paul explained that he chose this simple design over commercial products because he wanted to emphasize that these are just parts that anyone could find and put together. So far, the blocks have met with great success, with some interesting results. His favorite moment of discovery was when an inquisitive child hooked a motor up to a battery, through a speaker- the result was an amplified version of the noise that the motor makes when running!

He’s certainly not the first person to construct a setup like this, however I like the homebrew way in which it is made. I’m also a huge fan of the radically different switches that all do basically the same thing.

Have you ever built something similar? Have any tips for how to improve the design, or suggestions for cool components to include? There are more photos of the setup in my Flickr stream.

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This article was originally posted on Make

We’re learning a lot more about how planets interact with each other gravitationally. ‘Resonance’ is the operative term here. When planets are locked in a 2:1 orbital resonance, the outer planet orbits the host star once for every two orbits of the inner planet. A 3:2 resonance occurs when the outer planet orbits the star twice for every three orbits of the inner planet.

Resonance (technically ‘mean motion resonance’) prevents close encounters between planets and provides long-term orbital stability. And if the 2:1 resonance is the most common pattern, it’s also true that things can change when planets migrate to different parts of their system. John Johnson (Caltech) describes the result of fast inner migration:

“Planets tend to get stuck in the 2:1. It’s like a really big pothole. But if a planet is moving very fast it can pass over a 2:1. As it moves in closer, the next step is a 5:3, then a 3:2, and then a 4:3.”

Johnson’s work on resonance has born fruit in a new paper in which he and his colleagues discuss the discovery of two solar systems where gas giants in relative proximity to each other have become locked into resonance. Studying the matter helps us understand how solar systems evolve, as planets farther out in the protoplanetary disk migrate inwards, causing gravitational disturbances that can only become stable in orbital resonance.

Studying the star 24 Sextantis, some 244 light years from Earth, using radial velocity methods, the researchers have found two gas giants separated by about 0.75 AU, roughly 113 million kilometers. You can contrast this with the spacing between the largest planets in our system. Jupiter and Saturn are never closer than 531 million kilometers. The planets orbit the star with periods of 455 days and 910 days and are locked in a 2:1 orbital resonance.

A second gas giant pairing occurs around the star HD 200964, some 223 light years from Earth. Here the distance between the two gas giants can close to 0.35 AU (53 million kilometers). Johnson likens the latter pairing to that of Titan and Hyperion, two Saturnian moons, which also show a 4:3 resonance, but notes that the planets orbiting HD 200964 interact far more strongly, each being 20,000 times more massive than the combined mass of Titan and Hyperion. The planets in this system have orbital periods of 630 and 830 days respectively. Johnson adds:

“This is the tightest system that’s ever been discovered, and we’re at a loss to explain why this happened. This is the latest in a long line of strange discoveries about extrasolar planets, and it shows that exoplanets continuously have this ability to surprise us. Each time we think we can explain them, something else comes along.”

Gravitational interactions in this environment are quite powerful. This Caltech news release notes that the gravitational tug between HD 200964’s two planets is 3 million times greater than the gravitational force between Earth and Mars, 700 times larger than that between the Earth and the Moon, and 4 times larger than the pull of the Sun on the Earth.

As to the history of these worlds, the paper on this work notes their current positions and their likely changes over time:

In both the 24 Sex and HD 200964 systems, the planets reside well within the so-called snow line, beyond which volatiles in the protoplanetary disk can condense to provide the raw materials for protoplanetary core growth. For a pre-main-sequence, 1.5 M [solar mass] star the snow line is located beyond 2-3 AU… It is therefore likely that the planets around 24 Sex and HD 200964 formed at larger semimajor axes and subsequently experienced inward orbital migration.

Both of these stars are massive and dying, subgiants that have evolved off the main sequence and have run out of hydrogen for nuclear fusion. The eventual fate of such stars is to become a red giant, but neither of the stars has progressed that far. While red giants are problematic for radial velocity methods because their pulsations mask the spectral shifts that would reveal orbiting planets, subgiants have not expanded to that point and planet hunting remains possible. In fact, using the Keck Subgiants Planet Survey, Johnson and team are learning a great deal about such systems:

“Right now, we’re monitoring 450 of these massive stars, and we are finding swarms of planets. Around these stars, we are seeing three to four times more planets out to a distance of about 3 AU — the distance of our asteroid belt — than we see around main-sequence stars. Stellar mass has a huge influence on frequency of planet occurrence, because the amount of raw material available to build planets scales with the mass of the star.”

The paper is Johnson et al., “Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextan[t]is and HD 200964,” accepted for publication in The Astronomical Journal (abstract).

This article was originally posted on Centauri Dreams

In this paper, Broecker correctly predicted “that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide”, and that “by early in the next century [carbon dioxide] will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years”. He predicted an overall 20th Century global warming of 0.8ºC due to CO₂ and worried about the consequences for agriculture and sea level.


Global temperature up to June 2010 according to the NASA GISS data. Grey line is the 12-month running average, red dots are annual-mean values. The thick red line is a non-linear trend line. Broecker of course did not have these data available, not even up to 1975, since this global compilation was only put together in the late 1970s (Hansen et al. 1981). He had to rely on more limited meteorological data.

To those who even today claim that global warming is not predictable, the anniversary of Broecker’s paper is a reminder that global warming was actually predicted before it became evident in the global temperature records over a decade later (when Jim Hansen in 1988 famously stated that “global warming is here”).

Broecker is one of the great climatologists of the 20th Century: few would match his record of 400 scientific papers, a full sixty of which have over 100 citations each! Interestingly, his “global warming” paper is not amongst those highly-cited ones, with “only” 79 citations to date. Broecker is most famous for his extensive work on paleoclimate and ocean geochemistry.

It is very instructive to see how Broecker arrived at his predictions back in 1975 – not least because even today, many lay people incorrectly assume that we attribute global warming to CO₂ basically because temperature and CO₂ levels have both gone up and thus correlate. Broecker came to his prediction at a time when CO₂ had been going up but temperatures had been going down for decades – but Broecker (like most other climate scientists at the time, and today) understood the basic physics of the issue.

Basically his prediction involved just three simple steps that in essence are still used today.

Step 1: Predict future emissions

Broecker simply assumed a growth in fossil fuel CO₂ emissions of 3% per year from 1975 onwards. With that, he arrived at cumulative fossil CO₂ emissions of 1.67 trillion tons by the year 2010 (see his Table 1). Not bad: the actual emissions turned out to be about 1.3 trillion tons (Canadell et al, PNAS 2007 – estimate extended to 2010 by me).

A shortcoming, from the modern point of view, is that Broecker did not include other anthropogenic greenhouse gases or aerosol particles in his calculations. He does however discuss aerosols, which he calls “dust”. In fact, the first sentence of the abstract (quoted above) in full starts with an if-statement:

If man-made dust is unimportant as a major cause of climate change, then a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide.

That is a nod to the discussion about aerosol-induced cooling in the early 1970s. Broecker rightly writes:

It is difficult to determine the significance of the next most important climatic effect induced by man, “dust”, because of uncertainties with regard to the amount, the optical properties and the distribution of man-made particles,

citing a number of papers by Steve Schneider and others. Because he cannot quantify it, he leaves out this effect. Here luck was on Broecker’s side: the warming by other greenhouse gases and the cooling by aerosols largely cancel today, so considering only CO₂ leads to almost the same radiative forcing as considering all anthropogenic effects on climate (see IPCC AR4, Fig. SPM.2).

Table 1 of Broecker (1975)

Step 2: Predict future concentrations

To go from the amount of CO₂ emitted to the actual increase in the atmosphere, one needs to know what fraction of the emissions remains in the air: the “airborne fraction”. Broecker simply assumed, based on past data of emissions and CO₂ concentrations (Keeling’s Mauna Loa curve), that the airborne fraction is a constant 50%. I.e., about half of our fossil fuel emissions accumulates in the atmosphere. That is still a good assumption today, if you look at the observed CO₂ increase as fraction of fossil fuel emissions. Broecker calculated that about 35% of the emissions is taken up by the ocean and the other 15% by the biosphere (again not far from modern values, see Canadell et al.). On this basis he argued that if the ocean is the main sink, the airborne fraction would remain almost constant for the decades to come (his calculations extend to the year 2010).

Thus, with a 3% increase in emissions per year and 50% of that remaining airborne, it is easy to compute the increase in CO₂ concentrations. He obtains an increase from 295 to 403 ppm from 1900 to 2010. The actual value in 2010 is 390 ppm, a little lower than Broecker estimated because his forecast cumulative emissions were a little too high.

Step 3: Compute the global temperature response

Now we come to the temperature response to increased CO₂ concentration. Broecker writes:

The response of the global temperature to the atmospheric CO₂ content is not linear. As the CO₂ content of the atmosphere rises, the absorption of infrared radiation will “saturate” over an ever greater portion of the band. Rasool and Schneider point out that the temperature increases as the logarithm of the atmospheric CO2 concentration.

Based on this logarithmic relationship (still valid today) Broecker assumes a climate sensitivity of 0.3ºC warming for each 10% increase in CO2 concentration, which amounts to 2.2ºC warming for CO₂ doubling. This is based on early calculations by Manabe and Wetherald. Broecker writes:

Although surprises may yet be in store for us when larger computers and better knowledge of cloud physics allow the next stage of modeling to be accomplished, the magnitude of the CO₂ effect has probably been pinned down to within a factor of 2 to 4.

The AR4 gives the uncertainty range of climate sensitivity as 2-4.5ºC warming for CO₂ doubling, so there still is about a factor of 2 uncertainty and Broecker used a value near the very low end of this uncertainty range. Modern estimates are not only based on model calculations but also on paleoclimatic and modern data; the AR4 lists 13 studies that constrain climate sensitivity in its table 9.3.

In Broecker’s paper the warming calculated with the help of climate sensitivity happens instantaneously. Today we know that the climate system responds with a time lag due to ocean thermal inertia. By neglecting this, Broecker overestimated the warming at any given time; accounting for thermal inertia would have reduced his warming estimate by about a third (see AR4 Fig. SPM.5). But again he was lucky: picking ~2ºC rather than the more likely ~3ºC climate sensitivity compensates roughly for this, so his 20th-Century warming of 0.8ºC is almost spot on (the actual estimate being closer to 0.7ºC, see Fig. above). (A modern version of this back-of-envelope warming calculation is found e.g. in our book Our Threatened Oceans, p.82.)

Natural Variability

Broecker was not the first to predict CO₂-induced warming. In 1965, an expert report to US President Lyndon B. Johnson had warned: “By the year 2000, the increase in carbon dioxide will be close to 25%. This may be sufficient to produce measurable and perhaps marked changes in climate.” And in 1972, a more specific prediction similar to Broecker’s was published by the eminent atmospheric scientist J.S. Sawyer in Nature (for a history in a nutshell, see my newspaper column here).

The innovation of Broecker’s article – apart from introducing the term “global warming” – was in combining estimates of CO₂ warming with natural variability. His main thesis was that a natural climatic cooling

has, over the last three decades, more than compensated for the warming effect produced by the CO₂ [....] The present natural cooling will, however, bottom out during the next decade or so. Once this happens, the CO₂ effect will tend to become a significant factor and by the first decade of the next century we may experience global temperatures warmer than any in the last 1000 years.

The latter turned out to be correct. The idea that the small cooling from the 1940s to 1970s is due to natural variability still cannot be ruled out, although more likely this is a smaller part of the explanation and the cooling is primarily due to the “dust” neglected by Broecker, i.e. due to the rise of anthropogenic aerosol pollution (Taylor and Penner, 1994). However, the way Broecker estimated and even predicted natural variability has not stood the test of time. He used data from the Camp Century ice core in Greenland, arguing that these “may give a picture of the natural fluctuations in global temperature over the last 1000 years”. Ironically, Broecker’s own later work on Atlantic ocean circulation changes showed that Greenland is likely even less representative of global temperature changes than most other places on Earth, it being strongly affected by variability in ocean heat transport (see our recent post on the Younger Dryas, or Broecker’s latest book The Great Ocean Conveyor). However, Broecker was right to conclude that the buildup of CO₂ would sooner or later overwhelm such natural climate variations.

Overall, Broecker’s paper (together with that of Sawyer) shows that valid predictions of global warming were published in the 1970s in the top journals Science and Nature, and warming has been proceeding almost exactly as predicted for at least 35 years now. Some important aspects were not understood back then, like the role of greenhouse gases other than CO₂, of aerosol particles and of ocean heat storage. That the predictions were almost spot-on involved an element of luck, since the neglected processes do not all affect the result in the same direction but partly cancel. Nevertheless, the basic fact that rising CO₂ would cause a “pronounced global warming”, as Broecker put it, was well understood in the 1970s. In a 1979 TV interview, Steve Schneider rightly described this as a consensus amongst experts, with controversy remaining about the exact magnitude and effects.

Reference
BROECKER WS, 1975: CLIMATIC CHANGE – ARE WE ON BRINK OF A PRONOUNCED GLOBAL WARMING?
SCIENCE Volume 189, Pages 460-463.

This article was originally posted on Real Climate

Time travel holds such perennial fascination that even though its relationship with interstellar issues is slim, I can’t resist reporting on new ideas about it. John Cramer’s time experiments seem stuck in limbo, but now we have new work from Seth Lloyd (MIT) and colleagues about one way out of the paradoxes time travel seemingly creates. The ‘grandfather paradox,’ returning to the past to kill your own grandfather and thus causing your future self not to exist, seems inevitable if we grant the existence of what are called ‘closed timelike curves’ (CTCs), the paths through spacetime that would let a time traveler interact with his or her self in the past.

Ways Around Paradox

Lloyd’s team gets past that problem by describing a particular version of closed timelike curves formed with what is called ‘post-selection.’ The idea is to describe these CTCs in terms of quantum mechanics, starting with the assumption that time travel is a communications channel from the future to the past. Is there, then, a quantum communication channel to the past? The researchers consider quantum teleportation, in which a quantum measurement combined with classical communication lets quantum states be transported between sender and receiver.

The paper then applies quantum teleportation to timelike curves with postselection (P-CTCs):

We show that if quantum teleportation is combined with post-selection, then the result is a quantum channel to the past. The entanglement occurs between the forward- and backward-going parts of the curve, and post-selection replaces the quantum measurement and obviates the need for classical communication, allowing time travel to take place. The resulting theory allows a description both of the quantum mechanics of general relativistic closed timelike curves, and of Wheeler-like quantum time travel in ordinary spacetime.

As best I can untangle this (and we’ll deal with Wheeler in a moment), the post-selection idea means that time travel paradoxes are ruled out. Try to perform the event causing the paradox and something will happen to make the action fail. Moreover, although this theory of post-selection in timelike curves was created to deal with quantum mechanics in CTCs following the principles of general relativity, the authors think it extends to other contexts. Quantum theory that allows entanglement, in other words, seems to allow time travel even when no spacetime closed timelike curve exists.

Tunneling Through Time

Lloyd’s team says this quantum time travel can be thought of as ‘a kind of quantum tunneling backwards in time, which can take place even in the absence of a classical path from future to past.’ That’s a helpful thought, given that the extreme distortions of spacetime required by more traditional time travel thinking in a relativistic context are all but impossible to create.

Interestingly, there already exists a growing literature on entanglement and projection in the development of timelike curves, all described briefly in this paper. But the authors are particularly careful to note John Wheeler’s ideas impinging on quantum time travel, ideas that Richard Feynman described in his Nobel Prize lecture. This is worth repeating:

‘I received a telephone call one day at the graduate college at Princeton from Professor Wheeler, in which he said, “Feynman, I know why all electrons have the same charge and the same mass.”
“Why?”
“Because, they are all the same electron!”
And, then he explained on the telephone, “Suppose that the world lines which we were ordinarily considering before in time and space – instead of only going up in time were a tremendous knot, and then, when we cut through the knot, by the plane corresponding to a fixed time, we would see many, many world lines and that would represent many electrons, except for one thing. If in one section this is an ordinary electron world line, in the section in which it reversed itself and is coming back from the future we have the wrong sign to the proper time – to the proper four velocities – and that’s equivalent to changing the sign of the charge, and, therefore, that part of a path would act like a positron.”’

And now we’re really in Wonderland. Post-selection accepts only particular results, meaning that the only states that can be teleported via quantum entanglement are those that are consistent with the world we know. Time travel in this guise is necessarily consistent with our reality and forbids any actions that would create paradoxes. The authors put it this way: “…although any quantum theory of time travel quantum mechanics is likely to yield strange and counter-intuitive results, P-CTCs appear to be less pathological. They are based on a different self-consistent condition that states that self-contradictory events do not happen…”

Ratcheting Up Improbabilities

In an article on this work in Science News, Laura Sanders takes note of the fact that ruling out paradoxes means that unlikely events may happen with greater frequency:

“If you make a slight change in the initial conditions, the paradoxical situation won’t happen. That looks like a good thing, but what it means is that if you’re very near the paradoxical condition, then slight differences will be extremely amplified,” says Charles Bennett of IBM’s Watson Research Center in Yorktown Heights, N.Y.

For instance, a bullet-maker would be inordinately more likely to produce a defective bullet if that very bullet was going to be used later to kill a time traveler’s grandfather, or the gun would misfire, or “some little quantum fluctuation has to whisk the bullet away at the last moment,” Lloyd says. In this version of time travel, the grandfather, he says, is “a tough guy to kill.”

So we have no paradoxes but we seem to be distorting probability, a very strange result but maybe a bit less strange than the paradoxes we’ve avoided. Time travel makes for eerily seductive fiction — who would not wonder about traveling into the past to see loved ones again, or to remedy some unintentional wrong — and judging from the number of emails I received pointing me to this paper, the idea is as compelling now as it has ever been. I hadn’t realized how far back time travel has resonated in history, but the paper notes an account in the Hindu epic called the Mahabarata in which King Revaita visits the Brahma’s palace, stays for only a few days, and returns to Earth only to find that many eons have passed in his absence.

This is more or less the idea behind the creaky science fiction story “Out Around Rigel” (Astounding Stories, December 1931), in which Robert H. Wilson imagines the first journey to another star and uses the event as a way to teach Einsteinian special relativity (the first time this was done in science fiction, to my knowledge). The crew returns to find a thousand years have passed during their six-month journey. But this is a time travel account from the standpoint of relativistic spacetime. Quantum mechanics, in this paper’s estimate, might give us options other than that one-way ticket to the future.

How post-selection would work in quantum mechanics has yet to be determined, but the authors discuss the possibility of testing their theory experimentally by using quantum teleportation. Can people ever hope to take a journey into their own past with a self-consistent, non-paradoxical outcome? Science fiction writers will want to mull over the findings of this thorny, mind-bending paper and especially note the extensive literature treating entanglement and projection in the creation of closed timelike curves.

The paper is Lloyd et al., “The quantum mechanics of time travel through post-selected teleportation,” available as a preprint. Be aware as well of Lloyd et al., “Closed timelike curves via post-selection: theory and experimental demonstration” (preprint). This story on Physorg.com also discusses Lloyd’s work and ponders non-linearity in quantum mechanics.

This article was originally posted on Centauri Dreams

With more attention now being focused on possible missions to an asteroid, we should keep in mind that DLR, the German Aerospace Center, has been looking into an asteroid mission via solar sail for some time now. One 2006 paper from DLR’s Institute of Space Simulation pondered a 70-meter sail for use in a projected mission to the Near-Earth Object 1996FG3 within ten years of launch. It’s an interesting notion, one that would involve the sail hovering over the NEA hemisphere opposite to the Sun, deploying a lander and return capsule.

DLR has been into serious sail studies for some time now, as the photo below attests. It’s a 1999 shot of the ground deployment of a square solar sail 20 meters to the side. As you can see, this is a square sail made up of four triangular sail segments, an exercise that could readily lead to a sail deployment in space if the European Space Agency opts for funding such a mission. Just what ESA has in mind for such technology was the subject of a presentation at the just concluded Second International Symposium on Solar Sailing in Brooklyn.

Image: DLR’s deployed solar sail, seen at the Center’s facility in Cologne. Credit: DLR.

I’m looking at the paper on “The 3-Step DLR-ESA Gossamer Road to Solar Sailing,” available in the proceedings of the conference, and enjoying the ‘gossamer road’ metaphor that is so reminiscent of the fabled Silk Road, that network of trade routes that took its name from the Chinese silk trade and reached across Asia to the Mediterannean, Europe and north Africa. Maybe the ‘gossamer road’ is an indicator of enthusiasm at DLR and ESA for renewing sail work, for late last year the two agreed on the road map to solar sailing presented here.

Three consecutive steps define the roadmap:

• Gossamer-1: A 5-meter square solar sail launched as a deployment demonstrator to a 320 kilometer Earth orbit. Documentation of the deployment is to be handled by two onboard cameras (which inevitably calls up the images of the IKAROS sail deployment, similarly tracked). This demonstrator mission would be launched in 2013.
• Gossamer-2: A 20-meter square sail launched to a 500 kilometer Earth orbit. Here the idea is to test orbit and attitude control of a sail built out of thinner materials than the 7.5 µm Kapton used in Gossamer-1. Launch in 2014.
• Gossamer-3: A 50m x 50m solar sail launched to a 10,000 kilometer Earth orbit, with testing of orbit and attitude control and, as with the earlier missions, documentation by onboard cameras. An acceleration > 0.1 mm/s² is sufficient for the sailcraft to leave the Earth’s gravitational field after a period of about 100 days.

As you see, the gossamer missions build into growing layers of complexity and, because of limited budgets and a tight time schedule, tap the technologies and materials already developed in earlier DLR and ESA sail work. The paper notes that DLR has already done extensive work not only on sail materials but on the boom technology that supports the sail.

Also supporting the Gossamer project is a Light Pressure Measurement Facility (LPMF) set up by the DLR Institute for Space Systems in Bremen and Berlin. This is a key issue, because the reflectivity of the sail materials determines the efficiency of the propulsion achieved, and a variety of processes during a mission can cause that reflectivity to degrade. DLR is also setting up a Complex Irradiation Facility, now being commissioned, to examine the effects of the solar wind and electromagnetic radiation on sail materials. The trick here is to extrapolate from short-period degradation caused by high intensity bombardment in the facility to the longer, slower processes that a sail will experience in the space environment.

It’s interesting to see that so much recent sail technology has revolved around CubeSats, miniaturized satellites weighing no more than one kilogram that typically work with off-the-shelf electronics. CubeSats were developed as a way for universities to become involved in space exploration, but their small size and inexpensive components make them ideal for experimentation of all kinds. These ‘nano-satellites’ play a role in the NanoSail-D and the Planetary Society’s Lightsail-1 projects as well as DLR’s Gossamer program, allowing early risks to be spread over a number of low cost missions. It’s satisfying to think that IKAROS will soon be joined by other experiments shaking out a future workhorse propulsion system.

The asteroid mission referenced above is discussed in Dachwald et al., “Multiple rendezvous and sample return missions to near-Earth objects using solar sailcraft,” Acta Astronautica 59 (2006), pp. 768-776.

This article was originally posted on Centauri Dreams