- How writing technology shaped classical thinking
- TESS discovers its third new planet, with longest orbit yet
- Tackling greenhouse gases
Posted: 07 Jan 2019 09:00 PM PST
The Roman poet Lucretius' epic work "De rerum natura," or "On the Nature of Things," is the oldest surviving scientific treatise written in Latin. Composed around 55 B.C.E., the text is a lengthy piece of contrarianism. Lucreutius was in the Epicurean school of philosophy: He wanted an account of the world rooted in earthly matter, rather than explanations based on the Gods and religion.
Among other things, Lucretius believed in atomism, the idea that the world and cosmos consisted of minute pieces of matter, rather than four essential elements. To explain this point, Lucretius asked readers to think of bits of matter as being like letters of the alphabet. Indeed, both atoms and letters are called "elementa" in Latin — probably derived from the grouping of L,M, and N in the alphabet.
To learn these elements of writing, students would copy out tables of letters and syllables, which Lucretius thought also served as a model for understanding the world, since matter and letters could be rearranged in parallel ways. For instance, Lucretius wrote, wood could be turned into fire by adding a little heat, while the word for wood, "lingum," could be turned into the world for fire, "ignes," by altering a few letters.
Students taking this analogy to heart would thus learn "the combinatory potential of nature and language," says Stephanie Frampton, an associate professor of literature at MIT, in a new book on writing in the Roman world.
Moreover, Frampton emphasizes, the fact that students were learning all this specifically through writing exercises is a significant and underappreciated point in our understanding of ancient Rome: Writing, and the tools of writing, helped shape the Roman world.
"Everyone says the ancients are really into spoken and performed poetry, and don't care about the written word," Frampton says. "But look at Lucretius, who's the first person writing a scientific text in Latin — the way that he explains his scientific insight is through this metaphor founded upon the written word."
Frampton explores this and other connections between writing and Roman society in her new work, "Empire of Letters," published last week by Oxford University Press.
The book is a history of technology itself, as Frampton examines the particulars of Roman books — which often existed as scrolls back then — and their evolution over time. But a central focus of the work is how those technologies influenced how the Romans "thought about thought," as she says.
Moreover, as Frampton notes, she is studying the history of Romans as "literate creatures," which means studying the tools of writing used not just in completed works, but in education, too. The letter tables detailed by Lucretius are just one example of this. Romans also learned to read and write using wax tablets that they could wipe clean after exercises.
The need to wipe such tablets clean drove the Roman emphasis on learning the art of memory — including the "memory palace" method, which uses visualized locations for items to remember them, and which is still around today. For this reason Cicero, among other Roman writers, called memory and writing "most similar, though in a different medium."
As Frampton writes in the book, such tablets also produced "an intimate and complex relationship with memory" in the Roman world, and meant that "memory was a fundamental part of literary composition."
Tablets also became a common Roman metaphor for how our brains work: They thought "the mind is like a wax tablet where you can write and erase and rewrite," Frampton says. Understanding this kind of relationship between technology and the intellect, she thinks, helps us get that much closer to life as the Romans lived it.
"I think it's analagous to early computing," Frampton says. "The way we talk about the mind now is that it's a computer. … We think about the computer in the same way that [intellectuals] in Rome were thinking about writing on wax tablets."
As Frampton discusses in the book, she believes the Romans did produce a number of physical innovations to the typical scroll-based back of the classic world, including changes in layout, format, coloring pigments, and possibly even book covers and the materials used as scroll handles, including ivory.
"The Romans were engineers, that's [one thing] they were famous for," Frampton says. "They are quite interesting and innovative in material culture."
Looking beyond "Empire of Letters" itself, Frampton will co-teach an MIT undergraduate course in 2019, "Making Books," that looks at the history of the book and gets students to use old technologies to produce books as they were once made. While that course has previously focused on printing-press technology, Frampton will help students go back even further in time, to the days of the scroll and codex, if they wish. All these reading devices, after all, were important innovations in their day.
"I'm working on old media," Frampton says, "But those old media were once new."
Posted: 07 Jan 2019 02:14 PM PST
NASA's Transiting Exoplanet Survey Satellite, TESS, has discovered a third small planet outside our solar system, scientists announced this week at the annual American Astronomical Society meeting in Seattle.
The new planet, named HD 21749b, orbits a bright, nearby dwarf star about 53 light years away, in the constellation Reticulum, and appears to have the longest orbital period of the three planets so far identified by TESS. HD 21749b journeys around its star in a relatively leisurely 36 days, compared to the two other planets — Pi Mensae b, a "super-Earth" with a 6.3-day orbit, and LHS 3844b, a rocky world that speeds around its star in just 11 hours. All three planets were discovered in the first three months of TESS observations.
The surface of the new planet is likely around 300 degrees Fahrenheit — relatively cool, given its proximity to its star, which is almost as bright as the sun.
"It's the coolest small planet that we know of around a star this bright," says Diana Dragomir, a postdoc in MIT's Kavli Institute for Astrophysics and Space Research, who led the new discovery. "We know a lot about atmospheres of hot planets, but because it's very hard to find small planets that orbit farther from their stars, and are therefore cooler, we haven't been able to learn much about these smaller, cooler planets. But here we were lucky, and caught this one, and can now study it in more detail."
The planet is about three times the size of Earth, which puts it in the category of a "sub-Neptune." Surprisingly, it is also a whopping 23 times as massive as the Earth. But it is unlikely that the planet is rocky and therefore habitable; it's more likely made of gas, of a kind that is much more dense than the atmospheres of either Neptune or Uranus.
"We think this planet wouldn't be as gaseous as Neptune or Uranus, which are mostly hydrogen and really puffy," Dragomir says. "The planet likely has a density of water, or a thick atmosphere."
Serendipitously, the researchers have also detected evidence of a second planet, though not yet confirmed, in the same planetary system, with a shorter, 7.8-day orbit. If it is confirmed as a planet, it could be the first Earth-sized planet discovered by TESS.
In addition to presenting their results at the AAS meeting, the researchers have submitted a paper to Astrophysical Journal Letters.
Since it launched in April 2018, TESS, an MIT-led mission, has been monitoring the sky, sector by sector, for momentary dips in the light of about 200,000 nearby stars. Such dips likely represent a planet passing in front of that star.
The satellite trains its four onboard cameras on each sector for 27 days, taking in light from the stars in that particular segment before shifting to view the next one. Over its two-year mission, TESS will survey nearly the entire sky by monitoring and piecing together overlapping slices of the night sky. The satellite will spend the first year surveying the sky in the Southern Hemisphere, before swiveling around to take in the Northern Hemisphere sky.
The mission has released to the public all the data TESS has collected so far from the first three of the 13 sectors that it will monitor in the southern sky. For their new analysis, the researchers looked through this data, collected between July 25 and Oct. 14.
Within the sector 1 data, Dragomir identified a single transit, or dip, in the light from the star HD 21749. As the satellite only collects data from a sector for 27 days, it's difficult to identify planets with orbits longer than that time period; by the time a planet passes around again, the satellite may have shifted to view another slice of the sky.
To complicate matters, the star itself is relatively active, and Dragomir wasn't sure if the single transit she spotted was a result of a passing planet or a blip in stellar activity. So she consulted a second dataset, collected by the High Accuracy Radial velocity Planet Searcher, or HARPS, a high-precision spectrograph installed on a large ground-based telescope in Chile, which identifies exoplanets by their gravitational tug on their host stars.
"They had looked at this star system a decade ago and never announced anything because they weren't sure if they were looking at a planet versus the activity of the star," Dragomir says. "But we had this one transit, and knew something was there."
When the researchers looked through the HARPS data, they discovered a repeating signal emanating from HD 21749 every 36 days. From this, they estimated that, if they indeed had seen a transit in the TESS data from sector 1, then another transit should appear 36 days later, in data from sector 3. When that data became publicly available, a momentary glitch created a gap in the data just at the time when Dragomir expected the second transit to occur.
"Because there was an interruption in data around that time, we initially didn't see a second transit, and were pretty disappointed," Dragomir recalls. "But we re-extracted the data and zoomed in to look more carefully, and found what looked like the end of a transit."
She and her colleagues compared the pattern to the first full transit they had originally discovered, and found a near perfect match — an indication that the planet passed again in front of its star, in a 36-day orbit.
"There was quite some detective work involved, and the right people were there at the right time," Dragomir says. "But we were lucky and we caught the signals, and they were really clear."
They also used data from the Planet Finder Spectrograph, an instrument installed on the Magellan Telescope in Chile, to further validate their findings and constrain the planet's mass and orbit.
Once TESS has completed its two-year monitoring of the entire sky, the science team has committed to delivering information on 50 small planets less than four times the size of Earth to the astronomy community for further follow-up, either with ground-based telescopes or the future James Webb Space Telescope.
"We've confirmed three planets so far, and there are so many more that are just waiting for telescope and people time to be confirmed," Dragomir says. "So it's going really well, and TESS is already helping us to learn about the diversity of these small planets."
TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by Goddard. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA's Ames Research Center in California's Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes, and observatories worldwide are participants in the mission.
Posted: 07 Jan 2019 09:05 AM PST
The images are ubiquitous: A coastal town decimated by another powerful hurricane, satellite images showing shrinking polar ice caps, a school of dead fish floating on the surface of warming waters, swaths of land burnt by an out-of-control wildfire. These dire portrayals share a common thread — they offer tangible evidence that climate change is affecting every corner of the globe.
According to NASA, Earth's surface temperature has risen 0.9 degrees Celsius since the dawn of the Industrial Revolution. Researchers agree that the rise in temperatures has one primary culprit: increased greenhouse gas emissions.
Greenhouse gases like carbon dioxide, nitrous oxide, and methane all trap heat in our atmosphere, making them directly responsible for climate change. The occurrence of these gases in our atmosphere has increased exponentially since the late 1800s due to growth in fossil fuels use across the energy, manufacturing, and transportation industries.
A report from the U.N. Intergovernmental Panel on Climate Change (IPCC), released on Oct. 8, 2018 warned that if the Earth's temperature rises greater than 1.5 C, the effects would be catastrophic. Entire ecosystems could be lost, sea levels would be higher, and extreme weather events would become even more common. According to the IPCC, avoiding this scenario "would require rapid, far-reaching and unprecedented changes in all aspects of society," including a 45 percent decrease in carbon dioxide levels by 2030.
Researchers across MIT are working on a myriad of technologies that reduce greenhouse gas emissions across every industry. Many faculty are looking at sustainable energy. Associate Professor Tonio Buonassisi and his team in the Photovoltaic Research Lab hope to harness the power of the sun, while Professor Alexander Slocum has conducted research in making offshore wind turbines more efficient and economically viable.
In addition to exploring sustainable forms of energy that do not require fossil fuels, a number of faculty members in MIT's Department of Mechanical Engineering are turning to technologies that store, capture, convert, and minimize greenhouse gas emissions using very different approaches.
Improving energy storage with ceramics
For renewable energy technologies like concentrated solar power (CSP) to make sense economically, storage is crucial. Since the sun isn't always shining, solar energy needs to be somehow stored for later use. But CSP plants are currently limited by their steel-based infrastructure.
"Improving energy storage is a critical issue that presents one of the biggest technological hurdles toward minimizing greenhouse gas emissions," explains Asegun Henry, the Noyce Career Development Professor and associate professor of mechanical engineering.
An expert in heat transfer, Henry has turned to an unlikely class of materials to help increase the efficiency of thermal storage: ceramics.
Currently, CSP plants are limited by the temperature at which they can store heat. Thermal energy from the solar power is currently stored in liquid salt. This liquid salt can't exceed a temperature of 565 C since the steel pipes they flow through will get corroded.
"There has been a ubiquitous assumption that if you're going to build anything with flowing liquid, the pipes and pumps have to be out of metal," says Henry. "We essentially questioned that assumption."
Henry and his team, which recently moved from Georgia Tech, have developed a ceramic pump that allows liquid to flow at much higher temperatures. In January 2017, he was entered into the Guinness Book of World Record for the "highest operating temperature liquid pump." The pump was able to circulate molten tin between 1,200 C and 1,400 C.
"The pump now gives us the ability to make an all-ceramic infrastructure for CSP plants, allowing us to flow and control liquid metal," Henry adds.
Rather than use liquid salt, CSP plants can now store energy in metals, like molten tin, which have a higher temperature range and won't corrode the carefully chosen ceramics. This opens up new avenues for energy storage and generation. "We are trying to turn up the temperature so hot that our ability to turn heat back into electricity gives us options," Henry explains.
One such option, would be to store electricity as glowing white hot heat like that of a light bulb filament. This heat can then be turned into electricity by converting the white glow using photovoltaics — creating a completely greenhouse gas free energy storage system.
"This system can't work if the pipes are temperature limited and have a short lifetime," adds Henry. "That's where we come in, we now have the materials that can make things work at crazy high temperatures."
Henry's record-breaking pump's ability to minimize greenhouse gas emissions goes beyond altering the infrastructure of solar plants. He also hopes to use the pump to change the way hydrogen is produced.
Hydrogen, which is used to make fertilizer, is created by reacting methane with water, producing carbon dioxide. Henry is researching an entirely new hydrogen production method which would involve heating tin hot enough to split methane directly and create hydrogen, without introducing other chemicals or making carbon dioxide. Rather than emit carbon dioxide, solid carbon particles would form and float on the surface of the liquid. This solid carbon is something that could then be sold for a number or purposes.
Converting pollutants into valuable materials
Capturing greenhouse gases and turning them into something useful is a goal shared by Betar Gallant, assistant professor of mechanical engineering.
The Paris Agreement, which seeks to minimize greenhouse gas emissions on a global scale, stated that participating countries need to consider every greenhouse gas, even those emitted in small quantities. These include fluorinated gases like sulfur hexafluoride and nitrogen trifluoride. Many of these gases are used in semiconductor manufacturing and metallurgical processes like magnesium production.
Fluorinated gases have up to 23,000 times the global warming potential of carbon dioxide and have lifetimes in the thousands of years. "Once we emit these fluorinated gases, they are virtually indestructible," says Gallant.
With no current regulations on these gases, their release could have lasting impact on our ability to curtail global warming. After the ratification of the Paris Agreement, Gallant saw a window of opportunity to use her background in electrochemistry to capture and convert these harmful pollutants.
"I'm looking at mechanisms and reactions to activate and convert harmful pollutants into either benign storable materials or something that can be recycled and used in a less harmful way," she explains.
Her first target: fluorinated gases. Using voltage and currents along with chemistry, she and her team looked into accessing a new reaction space. Gallant created two systems based on the reaction between these fluorinated gases and lithium. The result was a solid cathode that can be used in batteries.
"We identified one reaction for each of those two fluorinated gases, but we will keep working on that to figure out how these reactions can be modified to handle industrial-scale capture and large volumes of materials," she adds.
Gallant recently used a similar approach for capturing and converting carbon dioxide emissions into carbon cathodes.
In a recent study, Gallant first treated carbon dioxide in a liquid amine solution. This prompted a reaction that created a new ion-containing liquid phase, which fortuitously could also be used as an electrolyte. The electrolyte was then used to assemble a battery along with lithium metal and carbon. By discharging the electrolyte, the carbon dioxide could be converted into a solid carbonate while delivering a power output at about three volts.
As the battery continuously discharges, it eats up all the carbon dioxide and constantly converts it into a solid carbonate that can be stored, removed, or even charged back to the liquid electrolyte for operation as a rechargeable battery. This process has the potential for reducing greenhouse gas emissions and adding economic value by creating a new usable product.
The next step for Gallant is taking the understandings of these reactions and actually designing a system that can be used in industry to capture and convert greenhouse gases.
"Engineers in this field have the know-how to design more efficient devices that either capture or convert greenhouse gas emissions before they get released into the environment," she adds. "We started by building the chemical and electrochemical technology first, but we're really looking forward to pivoting next to the larger scale and seeing how to engineer these reactions into a practical device."
Closing the carbon cycle
Designing systems that capture carbon dioxide and convert it back to something useful has been a driving force in Ahmed Ghoniem's research over the past 15 years. "I have spent my entire career on the environmental impact of energy and power production," says Ghoniem, the Ronald C. Crane Professor of Mechanical Engineering.
Since the turn of the 21st century, his focus shifted from criteria pollutants, which were successfully curbed, to carbon dioxide emissions. The quickest solution would be to stop using fossil fuels. But Ghoniem acknowledges with 80 percent of energy production worldwide coming from fossil fuels, that's not an option: "The big problem really is, how do we continue using fossil fuels without releasing so much carbon dioxide in the environment?"
In recent years, he has worked on methods for capturing carbon dioxide from power plants for underground storage, and more recently for recycling some of the captured carbon dioxide into useful products, like fuels and chemicals. The end goal is to develop systems that efficiently and economically remove carbon dioxide from fossil fuel combustion while producing power.
"My idea is to close the carbon cycle so you can convert carbon dioxide emitted during power production back into fuel and chemicals," he explains. Solar and other carbon-free energy sources would power the reuse process, making it a closed loop system with no net emissions.
In the first step, Ghoniem's system separates oxygen from air, so fuel can burn in pure oxygen — a process known as oxy-combustion. When this is done, the plant emits pure carbon dioxide that can be captured for storage or reuse. To do this, Ghoniem says, "We've developed ceramic membranes, chemical looping reactors, and catalysts technology, that allow us to do this efficiently."
Using alternative sources of heat, such as solar energy, the reactor temperature is raised to just shy of 1,000 C to drive the separation of oxygen. The membranes Ghoniem's group are developing allow pure oxygen to pass through. The source of this oxygen is air in oxy-combustion applications. When recycled carbon dioxide is used instead of air, the process reduces carbon dioxide to carbon monoxide that can be used as fuel or to create new hydrocarbon fuels or chemicals, like ethanol which is mixed gasoline to fuel cars. Ghoniem's team also found that if water is used instead of air, it is reduced to hydrogen, another clean fuel.
The next step for Ghoniem's team is scaling up the membrane reactors they've developed from something that is successful in the lab, to something that could be used in industry.
Manufacturing, human behavior, and the so-called "re-bound" effect
While Henry, Gallant, Ghoniem, and a number of other MIT researchers are developing capture and reuse technologies to minimize greenhouse gas emissions, Professor Timothy Gutowski is approaching climate change from a completely different angle: the economics of manufacturing.
Gutowski understands manufacturing. He has worked on both the industry and academic side of manufacturing, was the director of MIT's Laboratory for Manufacturing and Productivity for a decade, and currently leads the Environmentally Benign Manufacturing research group at MIT. His primary research focus is assessing the environmental impact of manufacturing.
"If you analyze the global manufacturing sector, you see that the making of materials is globally bigger than making products in terms of energy usage and total carbon emitted, " Gutowski says.
As economies grow, the need for material increases, further contributing to greenhouse gas emissions. To assess the carbon footprint of a product from material production through to disposal, engineers have turned to life-cycle assessments (LCA). These LCAs suggest ways to boost efficiency and decrease environmental impact. But, according to Gutowski, the approach many engineers take in assessing a product's life-cycle is flawed.
"Many LCAs ignore real human behavior and the economics associated with increased efficiency," Gutowski says.
For example, LED light bulbs save a tremendous amount of energy and money compared to incandescent light bulbs. Rather than use these savings to conserve energy, many use these savings as a rationale to increase the number of light bulbs they use. Sports stadiums in particular capitalize on the cost savings offered by LED light bulbs to wrap entire fields in LED screens. In economics, this phenomenon is known as the "rebound effect."
"When you improve efficiency, the engineer may imagine that the device will be used in the exact same way as before and resources will be conserved," explains Gutowski. But this increase in efficiency often results in an increase in production.
Another example of the rebound effect can be found in airplanes. Using composite materials to build aircrafts instead of using heavier aluminum can make airplanes lighter, thereby saving fuel. Rather than utilize this potential savings in fuel economy to minimize the impact on the environment, however, companies have many other options. They can use this potential weight savings to add other features to the airplane. These could include, increasing the number of seats, adding entertainment equipment, or carrying more fuel to increase the length of the journey. In the end, there are cases were the composites airplane actually weighs more than the original aluminum airplane.
"Companies often don't think 'I'm going to save fuel'; they think about ways they can economically take advantage of increased efficiency," Gutowski.
Gutowski is working across disciplines and fields to develop a better understanding of how engineers can improve life cycle assessment by taking economics and human behavior into account.
"The goal is to implement policies so engineers can continue to make improvements in efficiency, but these improvements actually result in a benefit to society and reduce greenhouse gas emissions," he explains.
A global problem
"Remember, global warming is a global problem," says Ghoniem. "No one country can solve it by itself, we must do it together."
In September 2019, the U.N. Climate Summit will convene and challenge nations across the world to throw their political and economic weight behind solving climate change. On a smaller scale, MIT is doing its part to minimize its environmental impact.
Last spring, Gutowski and Julie Newman, director of sustainability at MIT, co-taught a new class entitled 2.S999 (Solving for Carbon Neutrality at MIT). Teams of students proposed realistic scenarios for how MIT can achieve carbon neutrality. "The students were doing real work on finding ways MIT can keep our carbon down," recalls Gutowski.
Whether it's a team of students in class 2.S999 or the upcoming U.N. Climate Summit, finding ways to minimize greenhouse gas emissions and curtail climate change is a global responsibility.
"Unless we all agree to work on it, invest resources to develop and scale solutions, and collectively implement these solutions, we will have to live with the negative consequences," Ghoniem says.
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