नासामा नेपाली वैज्ञानिकको उपलब्धि: पृथ्वीको ताप मापनमा ठूलाे फड्को

दिनेश कार्की बोष्टन (अमेरिका) कार्तिक १३

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नवीनकुमार मालकार

पृथ्वीलाई निरन्तर अवलोकन गरिरहेका चार भूउपग्रहको ४० वर्षदेखिका तथ्यांकलाई प्रयोग गर्दै एक नेपाली वैज्ञानिकले पृथ्वीको तापमान नाप्ने नयाँ गणितिय ‛एल्गोरिदम’ विकास गरेका छन्।
नेशनल एरोनोटिक्सस एण्ड स्पेश एडमिनिस्ट्रेशन (नासा)को जेट प्रपल्सन ल्याबमा कार्यरत नेपाली वैज्ञानिक डा नवीनकुमार मालाकार नेतृत्वम अनुसन्धानकर्ताकाे एउटा समूहले भूउपग्रहबाट प्राप्त तस्विरका आधारमा एउटै गणितीय विधिबाट पृथ्वीका विभिन्न स्थानको ताप मापन गर्ने नयाँ ‘एल्गोरिदम’ विकास गरेको हो।
यससम्बन्धी अनुसन्धान निष्कर्षसहितको लेख ‛आइइइइ ट्रान्जाक्सन एण्ड जियो साइन्स एन्ड रिमोट सेन्सिङ सोसाइटीको′ जर्नलमा प्रकाशित भएको छ। यो अनुसन्धानमा मालकारसँगै ग्यालन सी हुले, सिमाेन जे हुक, केली लार्बे, माेनिका कुक र जाेन अार स्कट संलग्न छन्।
अहिलेसम्म फरक–फरक भूउपग्रहबाट प्राप्त तथ्यांकलाई छुट्टाछुट्टै हिसाब गरेर मान (भ्याल) पत्ता लगाइन्थ्यो। भौतिकशास्त्रका शोधकर्ता डा मालाकारले भने, ‛यो एल्गोरिदम पृथ्वीको तापमान जोडिएका तमाम विषयवस्तु अध्ययनमा विश्वव्यापी रुपमै प्रयोग हुनसक्छ। तापमान हिसाबकिताब गर्ने काममा यसले एकरुपता ल्याउनेछ।’

यसअघि पृथ्वी तापमापन अध्ययनमा अप्टिकल डाटा मात्र उपलब्ध हुने गरेकोमा यो शोधको सफलतापछि अब थर्मल डेटा प्रयोग गर्न सकिने भएको छ। ‘सतहमा मापन गरिएको डेटा र स्याटलाइटबाट लिइएको डेटा क्रस भ्यालिडेशन गर्दा मेल खान्छ’, उनी भन्छन्।
यो वैज्ञानिक शोधलेख प्रकाशित भएपछि वैज्ञानिक समुदायबाट राम्रो प्रतिक्रिया आएको डा मालाकार बताउँछन्।
जलावयु परिवर्तनदेखि खेतीबाली अनुसन्धानमा उपयोगीजलवायू परिवर्तनको प्रवृत्ति देखाउन यो एल्गोरिदम उपायेगी हुने मालाकारको विश्वास छ। विगत ४० वर्षमा कुन कालखण्डमा पृथ्वीको तापक्रम कसरी परिवर्तन भएको छ भन्ने तुलनात्मक अध्ययन पनि यसबाट गर्न सकिन्छ। भूसतहको तापक्रमलाई तापसँग सम्बन्धित महत्वपूर्ण विषयवस्तु जस्तैः शहरी जनसंख्यामा बढ्दो तापक्रम (हिट स्ट्रेस)को असर, भेक्टरजनित रोगहरुको अध्ययन आदिमा उपयोग हुनेछ। यसैगरी भूसतहको तापक्रमको दीर्घकालीन प्रवृत्ति आँकलन गर्न पनि यो विधि सहायक हुनेछ।
अनुसन्धानमा युनाइटेड स्टेट्स जियोलोजिकल सर्वे (यूएसजीएस)को चारवटा भूउपग्रह (ल्याण्डस्याट)को सहयोगमा सम्भव भएको हो। ती भूउपग्रहले पृथ्वीलाई १ सय मिटरको रिजोल्यूसनमा अवलोकन गरेका तस्विर तथ्यांकलाई अनुसन्धानमा उपयोग गरिएको छ।
भूउपग्रहरु नम्बर ४, नम्बर ५, नम्बर ७ र नम्बर ८ बाट प्राप्त तस्विरका तथ्यांकलाई मिहिन ढंगबाट विश्लेषण गरिएको डा.मालाकार बताउँछन्। यी भूउपग्रहहरु विभिन्न समयमा यूएसजिएसले प्रक्षेपण गरेका हुन्।
नम्बर ४, ५ भूउपग्रह सन् १९८२ मा प्रक्षेपित गरिएको थियो। नम्बर ७ सन १९९९ र ८ सन् २०१३ मा पृथ्वीको कक्षमा पठाइएको थियो।पृथ्वीका जीवन र जलवायुका लागि तापमान निकै सम्वेदनशील विषय हो। वनजंगल फडानीको निरीक्षण गर्न पनि मेरो अनुसन्धानले विकास गरेको विधि काम लाग्छ’, उनी भन्छन्, ‘किनभने जहाँ रुख काटियो त्यहाँको तापक्रम बढी देखिन्छ र रुखहरु भएको ठाउँमा स्वभाविक रुपले तापक्रम कम हुन्छ।’
मानवजनित क्रियाकलापले भूमण्डलीय पर्यावरणलाई कस्तो असर गरेको छ भन्ने विषयको सूक्ष्म अध्ययनको लागि पनि यो प्रविधि उपयोगी हुनेछ। डा मालाकारले विकसित गरेको विधि खेतीयोग्य जमिनको उर्बरता दर परिवर्तन छ कि छैन भनेर विश्लेषण गर्न पनि प्रयोग गर्न सकिनेछ।
‘बालीनालीको बिमा गर्ने ठूला बिमा कम्पनीहरुले पनि हाम्रो बिधिलाई उपयाेग गर्न सक्छन्। यो विधिले सिजनको अन्त्यमा कति उत्पादन हुन्छ भन्ने निक्र्योल गर्न सक्छ’, उनी भन्छन्।
‘ब्लाकहोल’ अनुसन्धानकर्ता
अहिले पृथ्वीको तापमान हिसाब गर्ने विधि पत्ता लगाएर ख्याति कमाइरहेका मालाकारले त्रिभुवन विश्वविद्यालयमा स्नातकोत्तर गर्दा भने ‘ब्ल्याकहोल’का शोधकर्ता हुन्। त्यतिबेला उनका गाइड अन्तर्राष्र्टिय ख्यातिप्राप्त भौतिकशास्त्री उदयराज खनाल थिए। विज्ञानमा जे अनुसन्धान गरे पनि त्यसले समाजलाई प्रभाव पार्ने खालको हुनुपर्छ भन्ने सोच त्यतिबेलै भएको उनी सुनाउँछन्। भन्छन्, ‛फिजिक्समा शोध गर्छु भन्ने थियो तर के गर्ने भनेर स्पस्ट मार्गचित्र मसँग थिएन।’
नेपालको त्रिभुवन विश्वविद्यालयबाट भौतिक विज्ञानमा स्नातकोत्तर गरेका उनले युनिभर्सिटी अफ न्यूयोर्क अल्बानीबाट सन् २०११ मा भौतिक शास्त्रमा विद्यावारिधि पूरा गरेका हुन्।
एकवर्ष यता उनी म्यासाच्यूसेट्सको उस्टर स्टेट युनिभर्सिटीमा भौतिक विज्ञानका सहायक प्राध्यापकको रुपमा कार्यरत छन्। त्यसअघि उनी पोष्ट डक्टारल शोध बैज्ञानिकको रुपमा नासाको जेट प्रपल्सन ल्याब, क्याल्टेक कयालिफोर्नीमा कार्यरत थिए। त्यहाँ उनले नासाकै भूउपग्रह मोडिस, भिआइआइआरएस लगायतका तथ्यांकबाट पृथ्वी भूसतहको तापक्रमबारे शोध गरेका थिए।
उच्चशिक्षा अध्ययनका लागि अमेरिका आउनुअघि मालाकार मध्य बानेश्वरस्थित हिमालयन ह्वाइटहाउस कलेजमा फिजिक्स पढाउँदथे। मकवानपुरको हेटौंडामा जन्मेका नबिन मालाकारले भुटनदेवी माविबाट एसएलसी गरेका हुन्। भुटनदेवी मावीका शिक्षकहरुको प्रेरणाकै कारण आफू भौतिक विज्ञानको शिक्षामा आकर्षित भएको उनी सुनाउँछन्।

प्रकाशित १३ कार्तिक २०७५, मंगलबार | 2018-10-30 10:51:36

 Publised on nepalkhabar.com

https://nepalkhabar.com/np/news/community/48450 

The research paper:

https://ieeexplore.ieee.org/abstract/document/8361068

An Operational Land Surface Temperature Product for Landsat Thermal Data: Methodology and Validation
Nabin K. Malakar ; Glynn C. Hulley ; Simon J. Hook ; Kelly Laraby ; Monica Cook ; John R. Schott

Preprint is available: https://www.researchgate.net/publication/325231273_An_Operational_Land_Surface_Temperature_Product_for_Landsat_Thermal_Data_Methodology_and_Validation

Importance Of Physics Education In Nepal: The Rising Nepal/Oct 27, 2018

Importance Of Physics Education In Nepal 

Dr. Rudra Aryal, 
Hunter Francoeur &
Dr. Nabin K Malakar

Physics, the Greek meaning of “nature”, is a science that plays a key role in the daily life of human societies. It is the study of matter, energy and their interactions. According to a statement adopted by the International Union of Pure and Applied Physics (IUPAP, 1999), “Physics is an international enterprise, which plays a key role in the future progress of humankind”. Physics plays a key role in the world and generates fundamental knowledge. The influence of physics leads to the transfer of old technologies to the development of new ones along with productivity in economies. The interdisciplinary nature of economic growth also relies on greater cooperation between physics and other sciences. Therefore, physics education is an essential part of an advanced society.

Impacts
The Institute of Physics (IOP), a London based leading scientific membership society working to advance physics for the benefit of all, have reported that Physics-based companies contribute to about nine percent of the UK’s economic output and employ millions of people. Moreover, physics-based industries have multiple impacts on a country’s economy. An IOP study established that for every dollar amount invested into the physics-based industry can contribute to more than twice the value to the economy as a whole. The range of applications goes from manufacturing, fuel, crude materials, electro-mechanical, through optical-communication industries. No fields remain untouched by the impacts of physics. A famous example of how physics can aid in boosting the economic growth of a country can be illustrated by the following anecdote. Around 1850, William Gladstone, a British statesman, asked Michael Faraday why electricity was valuable. Faraday answered, “One day, you may tax it.” Obviously, one cannot imagine a standing nation without electricity today. 
A better understanding of physics leads to a greater economic growth. Einstein’s formula of E= mc2 allowed us to harvest energy from the physical matter. When the first nuclear weapon was designed by Nuclear Physicist Robert Oppenheimer, during the Manhattan Project, it opened the door to understanding the strength of Physics in the modern society post the Second World War. This idea created the mantra that fields such as nuclear energy, pharmaceuticals, and space exploration could leapfrog a country out of its developing state and into the industrialized era. Study of physics is also perceived as the study of prosperity. 
According to the American Institute of Physics (AIP) 2016 reports, government-supported research, and development (R&D) in the United States is less than quarter fraction while more than two-thirds of the US R&D is supported by the business-funded venues. However, basic research is still mostly supported by the US Federal government through universities and higher educational institutions. If one were to analyze the sources of funding published by the National Science Foundation’s National Center for Science and Engineering, the total R&D funding is continually increasing past 500 billion dollars since the record began in 1953. The business-sponsored R&D has increased from less than 0.6 percent of GDP in the 1950s to about 2 percent in recent years. Clearly, as the economic and business growth takes place, the industry would be able to self-support the cutting edge research as indicated by the current trends in the developed nations.
The general desire of a country to jump forth into the industrialized stage can be accomplished through research in the cutting-edge topics. However, developing nations are not able to support or maintain these cutting-edge research endeavors. Physics in developing countries should rather focus on implementing technologies to aid the current situation, developing a basic level of science education to the public, and creating programs to involve science within the government. Once basic needs are met physics and science will be able to aid the country in many aspects of life.
The first area that developing countries need to focus on is making the government more open to physics and science as an institution. By putting forth an effort to increase the knowledge of such sciences in the policy level, they can be applied to many aspects of life such as agriculture, medicine, and even everyday necessities such as electricity. This can start simply by taking more value in science during education and creating a foundation for the younger generation to learn. 
The governments in developing countries should focus on the basic education of the general population in physics and science. This would be one major stepping stone towards achieving economic growth. On a global scale, eighty percent of the world’s population is located in developing countries but only twenty-eight percent of the world’s scientists come from these countries. During the colonization of many countries, education in science was limited to colonial elites who meant for their children to have higher access in countries such as the United Kingdom. Flash forward to the 1960’s and this practice was partly maintained, instead of colonial elites science education is mainly held for higher class citizens at the secondary level. 
Once the developing countries prepare a foundation of basic science education at home then the people who are knowledgeable in physics and science can travel to other countries to bring back ideas. According to the statistics survey published by American Institute of Physics (AIP) in 2014, about 50 percent of the Ph.D. students in the USA are comprised of international students. The proportion has been about 50/50 for the last two decades. We are familiar with the trend that many physicists from developing countries are going to the USA and other developed countries for their higher education in Physics, and sciences in general. For example, more than four hundred Nepali Physicists, about ten percent of total physicists of Nepal, have received their doctorate level education in Physics from the USA. The Condensed matter physics is the most popular field in the USA followed by the particle and astrophysics. 
According to an informal survey conducted by the Association of Nepali Physicists in America (ANPA), the condensed matter physics, and Atomic, molecular, and optical physics (AMO), Atmospheric Physics, Nuclear Physics are the most favorite topics among the physicist from the Nepali diaspora, also a good percentage are engaged into the cutting-edge Solar/photovoltaic research, biomedical physics. It is timely that the government of Nepal should connect the scientific diaspora for the transfer of knowledge to their country of origin. As an example, Physics-based projects can be used for the development for the simple things to make life at the ground level easier for the general population. Notably, there are various efforts at the personal levels in which spontaneous attempts being made to bring science to society.
Some of the examples could include, but not limited to creating water filtration systems, geological exploration, or improving agricultural and medical practices using state-of-the-art drone technologies that will greatly facilitate countries. An idea in emerging technologies for alternative energy such as solar, or windmill, although not simple or cheap to implement may start a snowball effect in bringing the country out of the developing state. After a thorough feasibility study, the energy can be used to power production plants, which can then be utilized to create machinery that can create a system of carbon-neutral roadways and distribute electricity to all villages. This will create tremendous bounds for the country and improve all aspects of life. This energy can also be utilized in other ways such as creating farming machinery or serving in remote hospitals for people who are suffering. On top of this, it will also stimulate the economy creating new jobs and a means of making income.
To sum up, Physics plays a key role in the world and generates fundamental knowledge. While it is a normality in many industrialized countries, it is severely lacking in the developing countries. Physics education programme should be implemented from the governmental level to improve education and provide incentives for physics and engineering based companies that can improve quality of life.

Workforce
Developing a strong physics program with the support of research, scholarships, and fellowships for undergraduate and graduate students can make a huge difference in the education of Nepal. Once an expert workforce has been created ideas for improving life can bring in. One simple idea such as this can help improve the manufacturing of goods and help create roadways and give energy access to millions who lack it. Physics should focus on areas that would be most rewarding to the immediate situation of the country.

Published: 27 Oct, 2018 
http://therisingnepal.org.np/news/26644 

Special Issue "Sustainability in the Mountains Region"

http://www.mdpi.com/journal/sustainability/special_issues/mountains_region

Mountains are a part of the global biodiversity repository, play a vital role in maintaining global ecosystems, while supporting millions of people. In the meantime, they are the most vulnerable ecosystems. Changes in the environment and economic priorities in past few decades have considerably influenced the livelihood and sustainability of mountains globally. The effects of changing climate and other socioeconomic factors on mountains can affect the densely populated and underdeveloped regions to an inconceivable scale. It is, therefore, important that we study the impacts of climate change, changes in economic priorities of the mountain residents, and increasing non-conventional values of mountain ecosystems and its inhabitants. Moreover, the factors affecting the sustainable livelihood of mountain inhabitants need to be carefully studied to assess the short and long-term impacts, and to develop a long-term strategy for improving the livelihood of the residents in the face of the changes.

This Special Issue will feature peer-reviewed papers from the international conference on “Mountains in the Changing World (MoChWo)”, to be held in Kathmandu, Nepal, on 1–2 October, 2016 (http://conference.kias.org.np). The conference and the Special Issue aim to provide a forum for international/national scholars, researchers, policy makers, and students with an opportunity to share their research findings and knowledge related to various aspects of mountains.  

The range of relevant topics include:

• Environmental, economic and social sustainability
• Land use and land cover monitoring, natural disaster and risk assessment
• Decision making and societal impacts, policy and management strategies for sustainable development
• Citizen science and trainings
• Remote sensing, and mapping of resources
• Data fusion, and data visualization relevant to sustainability issues
• Innovation in renewable and alternative energy
• Pesticide uses and sustainable agriculture
• Organic farming

We welcome papers from broadly defined topics that are relevant to the theme of the Special Issue.

Dr. Nabin K Malakar
Dr. Rajan Ghimire
Dr. Jhalendra Rijal
Dr. Pradeep Wagle
Guest Editors

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An Interview with Dr. Mike Abrams, #ASTER project leader @NASAJPL

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument has been flying in space on the Terra platform since its launch in 1999. Not bad for a satellite which had an expected lifespan of five-years. Hopefully it will continue into the foreseeable future. The instrument acquires images in visible, near infrared, and thermal infrared wavelengths (TIR). The spatial resolution range from 15 to 90 meters. ASTER spans +- 83 degree latitudes, and covers 99 percent of earth's landmass.  ASTER also produces one of the high resolution elevation dataset (30m).

Recently, NASA released the complete archive (2.95 million images) of Earth's thermal infrared images to the public with unlimited access. Previously, users could access ASTER's global digital topographic maps for free, however, other ASTER data products were available at nominal fee paid to Japan’s Ministry of Economy, Trade and Industry (METI).

ASTER has been used to study, map, and monitor the ever-changing surface of our planet Earth. Some of the products and application of ASTER data include surface mapping and monitoring of changes in surface properties such as glacial advance/retreat, volcanism, crop stress, cloud properties, wetlands, coral reef degradation, land surface temperature, surface geology, etc.

A good selection of ASTER images can be found on the ASTER web site, gallery pages:

http://asterweb.jpl.nasa.gov/gallerymap.asp

The dataset is available at:

http://asterweb.jpl.nasa.gov/data.asp

We stopped by the office of Dr. Mike Abrams, the project leader for ASTER science team at NASA JPL.

Here are 5 quick questions with him:

1. Please share your experience with the ASTER project.

I have been involved with the ASTER project since its inception in 1988 as part of NASA’s Earth Observing System (EOS) program. Working with my Japanese colleagues and traveling to Japan has been an enriching inter-cultural experience. Added to that is the satisfaction of the success of our 16-year joint mission

2. Why are the millions of ASTER images being made public?

In Japan, oversight of the ASTER project was transferred from one organization to another. The new operator is part of Japan’s National Science Institutes. Jointly, with NASA, the decision was made to eliminate charging for all ASTER data.

3. How can users get maximum use out of the ASTER data?

Natural color, full resolution JPEG images can be downloaded for all images in the archive. No sophisticated software is needed to view these images. (https://lta.cr.usgs.gov/terralook/home). To do more in-depth analyses, the digital data must be downloaded, then analyzed with GIS or image processing software.

4. What are the unique feature of ASTER? (Some examples of news for societal benefit.)

Our high resolution, global Digital Elevation Model (DEM) data set is unique. It is the only topographic data freely available to all users covering the land surface of the Earth at 30m resolution. We have a vigorous monitoring program of 1500+ active volcanoes, and 100,000+ glaciers, looking for time-dependent change. We also acquire many images for post-disaster mitigation, like damage from tsunamis.

5. Do you have favorite image(s) of ASTER?

See the interview with National Geographic: http://news.nationalgeographic.com/2016/04/160406-pictures-nasa-terra-aster-satellites-space-science/

A selfie with Dr. Abrams.

Note: I had an opportunity to be a co-author with him on the paper:
The ASTER Global Emissivity Dataset (ASTER GED): Mapping Earth's emissivity at 100 meter spatial scale, GC Hulley, SJ Hook, E Abbott, N Malakar, T Islam, M Abrams

Geophysical Research Letters 42 (DOI: 10.1002/2015GL065564)

http://onlinelibrary.wiley.com/doi/10.1002/2015GL065564/full 

Gravitational Waves and LIGO Experiment

One of the fascinating argument of Einsteins' theory of General Relativity can be simply illustrated by the foam-ball diagram. Where a heavy ball put on the surface would produce a curvature. Thereby generating the deformation so that if a lighter ball is rolling nearby, it would cause the ball to roll towards the bigger ball.

Similarly, if we imagine that the space-time that our universe resides is a giant surface in 4-dimension, then we can argue that things that have mass will cause that surface to bend. In other words, the matter will tell the spacetime where to bend while the spacetime curvature will then dictate how the mass will travel.  The more "heavy" the mass, the more bending. Ultimately, the  heavy "mass" or huge Energy, can cause a hole in the fabric of spacetime. That we call the black hole!

What is interesting is that we can imagine traveling from point A to B. If the amount of effort that is required is called as action, then naturally one tends to minimize the action. The most straightforward way to minimize the action in two dimension is a straight line! Now, if you were in four dimension, and wanted to go from point (need to call it a four-point as it has four co-ordinates) A to point B. Then naturally, it would be a "straight" line in 4D! However, the manifestation of the space and time makes it look like a curved line near the "heavy" masses. That's the reason behind the orbits of the planets. You may ask: but, aren't the planets coming back to the same positions after one planetary year? Yes, that is right in space. But in time, you moved one year's worth of journey! Think about it!

That means there is no force which is pulling things around. It is just the manifestation of the bending of the spacetime fabric.

When  masses accelerate, gravitational waves are produced. This can cause "ripples" in the space!

The LIGO experiment, (LIGO: The Laster Interferometer Gravitational-Wave Observatory) was designed in 1992. It is a large-scale physics experiment to detect gravitational waves. It consists of 4 km long tunnels in L-shape. LASER interferometry is used to detect any change in the fabric of space due to the gravitational wave. Interferometry go about finding changes in the distance between the points A and B by using the principle of superposition of the waves, by measuring the change in the fringes due to shifting of the reflecting mirrors for example.  This works because when two waves with the same wavelength/frequency meet, their fates are determined by the phase difference between the waves. The waves in phase will undergo constructive interference and the out-of-phase will undergo destructive interference [See this video: https://www.youtube.com/watch?v=J_xd9hUZ2AY More specifically this one : https://www.youtube.com/watch?v=oUytkiBwXvI]. 

In the case of LIGO experiment, the primary interferometers consist of mirrors suspended at each corners of the L-shaped vacuum tube (4km long). A LASER beam is used to monitor the interference patterns called fringes. When a gravitational wave passes through the interferometer site, the fabric of spacetime is affected. Since the instrument is L-shaped, one side will be stretched while the other side is compressed. This changes the phase of the reflecting waves causing the phase difference between the ends of the L-tube, and thus the wave should be detected!!! 

The LIGO has to detect the distortion of 10^(-18) m in space for the light that reflects off the 4-km long tunnel! This is the length less than one thousandth of the diameter of a proton (fm=10^-15). Moreover, since there are two LIGO experiment sites(46°27′18.52″N119°24′27.56″W and
30°33′46.42″N90°46′27.27″W), triangulation method can be used to find the source of the ripple!

Here is a nice video explaining the method

https://youtu.be/FXlg3cr-q44?t=1m20s

Now here comes the big news!

LIGO has detected the gravitational wave!!!

The authors claim that the signals came from two merging black holes, each about 30 times the mass of our sun, lying 1.3 billion light-years away.

The scientific paper is here:

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102

If you are interested in the press release,

https://mediaassets.caltech.edu/gwave#graphics

FYI: India is working on next LIGO experiment
https://www.ligo.caltech.edu/page/ligo-india

Also, it seems like Einstein had doubt about the Gravitational waves at some point
http://scitation.aip.org/content/aip/magazine/physicstoday/article/58/9/10.1063/1.2117822

One interesting presentation
https://www.youtube.com/watch?v=ajZojAwfEbs

Disclaimer: These are my personal notes. Please draw conclusions at your own risk.