Hsueh MF et al. Analysis of “old” proteins unmasks dynamic gradient of cartilage turnover in human limbs. Science Advances, October 2019.

Humans may not be able to regrow amputated limbs, but a recent study showed that damaged cartilage may regrow through a process similar to that of animals such as salamanders and zebrafish. Scientists collected 18 specimens of joint tissue from the hips, knees, or ankles of patients who underwent surgery. They then placed the tissue in a mass spectrometer and measured the age of the cartilage proteins in the sample. These analyses showed that the age of cartilage largely depended on where it resided in the body. Cartilage in ankles is young, middle-aged in the knee, and old in the hips. This correlation between the age of human cartilage and its location in the body suggests that limb repair occurs in humans in a similar fashion to certain animals in which tissue regeneration takes place at the furthest tips such as the ends of legs or tails. This finding also helps to explain why injuries to people’s knees and, especially, hips take a long time to recover and often develop into arthritis, while ankle injuries heal quicker and less often become severely arthritic. The researchers further identified the molecules that are instrumental in the regulation of this region-specific regeneration process. They are called microRNAs and, not surprisingly, are present at very high levels in animals that are known for limb, fin, or tail repair including salamanders, zebrafish, and lizards. Scientists believe that these regulator microRNAs can be utilized in the regeneration of degenerated cartilage of an arthritic joint to reverse arthritis. Regeneration of part or all of an injured human limb may even be possible by finding components salamanders have and we don’t. Finally, it is also possible that this could be a fundamental mechanism of repair that could be applied to many tissues, not just cartilage, which might open up many new avenues in the regenerative medicine.

The universe might have many Earth-like exoplanets

Doyle AE et al. Oxygen fugacities of extrasolar rocks: Evidence for an Earth-like geochemistry of exoplanets. Science, October 2019.

New astrophysical and geochemical evidence suggests that Earth may not be that unique, and Earth-like planets may be common in the universe. All of the planets in our solar system orbit around the Sun. Planets that orbit around other stars are called exoplanets.  The first exoplanets were discovered in the early 1990s. Since then, thousands of exoplanets have been revealed with over 4,000 confirmed and a further 4,495 potential candidates. There have been major efforts to narrow down the exoplanets that may have properties similar to Earth with conditions suitable for life. This includes being a rocky planet that is not too hot or cold so that liquid water can exist. When searching for exoplanets that are similar to Earth, astronomers typically look for worlds in orbit around a type of star called a red dwarf or an M-dwarf. These types of stars are somewhat similar to our sun and make up about 70% of the stars in our galaxy. However, a new study shows that rocky exoplanets in orbit around a different type of star, a white dwarf, can have interiors that are surprisingly similar to our planet. White dwarf stars are dense remains of normal stars that have exhausted their nuclear fuel. These stars are typically composed of light elements such as hydrogen and helium, but in some cases they attract heavier elements such as magnesium, iron, and oxygen in their atmospheres due to their extreme gravity. These heavy elements are thought to be introduced when a rocky exoplanet crashes into a star, which gives astronomers evidence of what the exoplanets were like before they were destroyed. In this recent study, scientists looked at six white dwarfs located 200 to 665 light-years from Earth and rocks from the planets that once orbited it. Their analyses showed that five out of the six white dwarfs had sucked up fragments whose chemical composition is similar to rocks on Earth, Venus, and Mars. While the conditions suitable for life depend upon many additional factors, this study points towards the idea that many rocky planets are likely very familiar in terms of their general composition and, therefore, structure and behavior. This study also made a substantial leap forward in being able to make inferences for bodies outside of our own solar system and indicates that it is very likely that there are truly Earth analogs out there.

Artificial leaf points to a sustainable path to carbon-neutral fuels

Andrei V et al. Bias-free solar syngas production by integrating a molecular cobalt catalyst with perovskite–BiVO4 tandems. Nature Materials, October 2019.

An artificial leaf from which a “clean” fuel alternative to petrol could be produced has been developed. Synthetic gas can be obtained from the lead by using only sunlight, carbon dioxide, and water.

Synthetic gas, also called syngas, is typically a mixture of carbon monoxide and hydrogen. It is largely produced by exposing fossil fuels such as coal or natural gas to high temperature steam and pressure, and the process releases carbon dioxide. Syngas is broadly used in a wide range of commodities including fuels, plastics, and fertilizers. While the utilization of fossil fuels has enabled large-scale industrial development in human history, the burning of fossil fuels is the largest source of emissions of carbon dioxide, which is one of the greenhouse gases that contributes to global warming. For decades scientists have been trying to discover new ways to produce syngas in order to close the global carbon cycle and to establish a sustainable chemical and fuel industry. In a recent study, researchers got inspired by leaves. These perfect little machines use sunlight to convert carbon dioxide and water into fuel for plants through photosynthesis. An artificial leaf has been designed to have two light absorbers, similar to the molecules in plants that harvest sunlight, and a catalyst made from the naturally abundant element cobalt. When the leaf is immersed in water, one light absorber uses the catalyst to produce oxygen and the other one carries out the chemical reaction that reduces carbon dioxide and water into carbon monoxide and hydrogen, thus forming the syngas mixture. The scientists are now searching for ways to use their technology to produce a sustainable liquid syngas that could serve as an alternative to petrol. Although major efforts to generate renewable energy sources are being made, the development of synthetic petrol is critical as electricity can currently fulfill about 25% of our total global energy demand. There is a huge demand for liquid fuels to power heavy transport, shipping, and aviation sustainably.

“It is He who created the night and the day, and the sun and the moon; all (the celestial bodies) swim along, each in its orbit with its own motion.”  (Quran 21:33)

Almost everyone – depending on his or her age, experience, and education level – is aware of certain facts about nature. We know that the Sun rises in the east and sets in the west; water boils at 100 centigrade; humans have five basic senses; birds can find their way back after migrating thousands of miles; and many more. Likewise, laws of thermodynamics, laws of motion, universal law of gravitation, and laws of planetary motion are among the many tools scientists use to explain how nature and the universe work. In the same context, whether or not we are conscious of it, there is this ubiquitous fact of “revolving, rotating, and circling” in the universe in relation to science, religion, and culture. From the Milky Way, sun, planets, and moons to human eyes, circling is everywhere in the universe. Also, it’s imprinted everywhere in the natural world. Giving examples from scientific, spiritual, and social life, this article aims to inquire the “revolving, rotating, and circling” phenomenon to see if it has any implications for humanity.

Rotation of planets

Earth is one of the eight planets in our solar system, all of which orbit the sun, a giant burning star. We know from astronomy that the sun can fit more than one million Earths inside it. Throughout human history, stargazers have realized that all these planets move in a systematic way. The planets orbit due to the immense gravitational pull generated by the sun. Even though the rate may change, each planet rotates around the sun and on its own axis, an imaginary line running through the center of every planet. Also, there are more than one hundred terrestrial, gas, and dwarf moons that revolve around the planets. Every planet, except Mercury and Venus has at least one moon. For example, the Earth has only one Moon (Luna) which orbits around Earth every 29 days; on the other hand, Jupiter has at least 67 moons such as Ganymede, Callisto, and Europa in orbit around it. In addition, our solar system is swarming with different types of bodies (e.g. comets, meteors, asteroids, and space dust) that rotate around the sun along with Earth. Furthermore, it is believed that the Sun is one of about 200 billion stars (maybe more) just in our galaxy, the Milky Way. Galaxies move and gravitationally pull each other, and they do so while rotating around a center. That is, nothing is truly at rest. (1)

Orbiting an atom

In the 1920s, scientists of quantum mechanics discovered that an atom acts like a small solar system. While planets circle elliptically around the sun, electrons rotate around the atom’s nucleus in diffuse, cloud-like waves; these are known as orbitals since they tell us only the probability of detecting the electron at various places within the atom (Choe 2004). These orbitals can blend together to constitute a clump-like “wave packet” that includes the electrons and does rotate around the nucleus. It looks like this quantum phenomenon seems to support rotation in the universe. (2)

The circulation of blood

Doubtless, the heart is one of the most vital and fascinating organs in the human body. It incessantly pumps fresh blood with necessary nutrients throughout the body so that we can survive. Even though it is as big as your fist, it works like a powerhouse by expanding and contracting 100,000 times each day, pumping approximately five quarts of blood per minute, around 2,000 gallons every day. While the heart beats, it pumps blood through blood vessels in the circulatory system to every area of the human body, which takes about 20 seconds to circulate all over the vascular system. It is reported that the blood travels approximately 12,000 miles per day – nearly half the distance of the Equator (24,902 miles). Blood circulation is vital and fundamental to human life: it not only transfers fresh oxygen and nutrients to organs, but also carries away waste such as carbon dioxide from the organs, which is necessary to maintain a healthy life. (3, 4)

Five stages in the human life cycle

Similar to the cycle of four seasons (spring, summer, fall, and winter) in a year, the human life cycle has five or six different stages (Birth, infancy, childhood, adolescence, and adulthood). Human life begins as a single tiny cell, not bigger than a mustard seed, in a mother’s womb. After nine months, circa 40 weeks of pregnancy, the mother gives birth to a newborn. During the first year of infancy, the baby is entirely dependent on the parents’ care, but babies develop very quickly to independency. Childhood includes a period from age 4 to 13, when children learn to eat with utensils, dress and undress without assistance, make friends, play with other kids, and other things. Adolescence is the when a child develops into an adult, when teenagers undergo a rapid transformation of their bodies known as puberty. After the age 20, the human body reaches peak fitness and fertility by stopping development and growth. As we age in adulthood, it takes our body a longer time to repair itself and we become less efficient in many skills. (5)

Circling and prayer

It looks like that this one important pillar of Islam reminds us of the spinning motion in the universe, atoms, the circulatory system, and the life cycle. According to Islamic scholars, millions of pilgrims circulating the Holy Ka’ba in Mecca represents the deep reverence in Oneness of Almighty God. It is believed that these seven compulsory circumambulations of the Ka’ba (the most sacred site in Islam) include individual and social meanings like solidarity and maintaining unity. One explanation as to why Muslims circle the Holy Ka’ba seven times, is the Qur’anic verse that describes the sky above as of seven layers:

“The seven heavens and the earth and whatever is in them exalt Him. And there is not a thing except that it exalts [God] by His praise, but you do not understand their [way of] exalting. Indeed, He is ever Forbearing and Forgiving” (Al-Isra17:44).

It is known in Islam that the spiritual part of the human being includes seven different souls known as nafs. Therefore, every circumambulation of the Holy Ka’ba is meant to move from one spiritual level to the next in order to reach and complete the final expectation to turn our self (nafs) from meat and bone into a more delicate, sensitive, and loving form of soul, one even superior to the Angels. This act of circling the House of God, the Holy Ka’ba, shows how man is sincerely, spiritually, and lovingly attached to the divine.

Conclusion

The planets circle the sun, electrons circle the nucleus in an atom, blood circles the human body, pilgrims circumambulate Holy Ka’ba, and seasons and life cycles circle. There are many more examples of circling in the universe. Even though we cannot see all of them with the naked eye, the entire cosmos, ranging from invisible particles to the moons, planets, stars, and galaxies, are in rotation. Remember that all these rotations happen in accordance with the laws that govern the nature. There is no free choice in any of it.

People are members of this infinite universe, and, unlike planets, electrons, flowers, and cells, they can reason and decide, since we are blessed with free will. As Muslims circumambulate the House of God, this pulling motion between the Ka’ba and pilgrims escalates divine love by changing spiritual dimensions in a way similar to moths flying and circling a light source. Without doubt, a visit to the House of God is an obligatory and praised pillar of Islam, but I believe that the Merciful God wants us also to circle many other divine values and social qualities to deserve His love, mercy, and grace. As long as we circumambulate these highly valued vital qualities such as prayer, selflessness, charity, affection, forgiveness, respect, love, truth, compassion, modesty, patience, and all other good qualities, they will pull us closer both to each other and to Almighty God. Ignoring circling these divine and social qualities would be as if Earth left its orbit.

References

• https://spaceplace.nasa.gov/review/dr-marc-space/solar-systems-in-galaxy.html
• “A Tiny Solar System After All,” April 7, 2004. Rev. Focus13, 15. https://physics.aps.org/story/v13/st15
• “Amazing Heart Facts” in Arkansas Heart Hospital. https://www.arheart.com/heart-health/amazing-heart-facts/
• Jody Braverman, “The Human Life Cycle Stages” www.livestrong.com
• “Growing Older,” in Dorling Kindersley, findout!

Dark matter, the mysterious unseen mass, and dark energy, the universe’s mysterious force, comprise the rest of the unknown universe. We still know very little about dark energy and dark matter. Dozens of institutes and thousands of scientists have organized international collaborations in search of both. In fact, scientists hope the biggest energy particle collider [1], the Large Hadron Collider (LHC) in Geneva, will help solve the puzzles of dark energy and dark matter.

            It is common for people to ask, how did the universe begin? After decades of observing and measuring, today the majority of scientists explain the beginning of the universe via the Big Bang theory. Two astronomers, Arno Penzias and Robert Wilson, established the Big Bang theory of cosmology by observing the cosmic background of radiation [2]. According to their theory, everything in the universe was contained in one single mass and there was no space or time. Everything started with the explosion of this extremely dense and hot mass. This explosion was not like an explosion into an empty space; rather space itself began with this explosion.

The idea that led scientists to the Big Bang came from observing the universe’s expansion. Edwin P. Hubble found that almost all galaxies are moving away from the center of the universe [3]. He did so by measuring the light from these galaxies to determine their velocities. This proved that the universe was not static, but was instead expanding. After scientists realized that the universe is expanding, they thought that there must be a beginning to this expansion. Then, using the speed of this expansion, they calculated the life of the universe. Through this, they were able to show that the universe has a beginning. Today, almost every scientist agrees with the Big Bang, and they can support it with scientific evidence.

The idea of the universe, let alone an expanding universe, can be pretty incomprehensible. Let me make it a bit more comprehensible. Think about a balloon. There are two spots marked on this balloon. When you inflate the balloon, you’ll see how these two spots are moving away from each other. The balloon is the universe and the two spots are matter in that universe. This example shows how matter “rides” the expanding universe.

Until about 20 years ago, most scientists thought that the expansion of the universe was getting slower. In 1998, observations of the Type la supernovae revealed the existence of dark energy. Dark energy, scientists found, was one way to measure the expansion rate of the universe over time. This discovery was proof for the universe expanding at an increasing rate. Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess have been awarded the Shaw Prize in Astronomy in 2006 [4] and Nobel Prize in Physics in 2011 [5] for their breakthrough study on this topic. But though scientists know the universe is expanding faster and faster, no one yet knows why.

Let’s go back to the beginning of the universe and see how everything was induced into a perfect order. At the beginning, when the Big Bang (BB) occurred, one might think that this came with chaos and disorder. The perfect design of the universe came from that mess.

If we could get precise information all the way back to the Big Bang, it would help us to solve many outstanding mysteries. Unfortunately, we are unable to gather this information because the cosmos, in its infancy, was foggy and full of light rays. After about 300,000 years, the universe became transparent and many particles fell away; the furthest distance we can see across space is 13.7 billion light years, which is when the universe became transparent.

Cosmic Microwave Background (CMB) was formed almost 380,000 years after the BB. That is the cosmic background radiation, or thermal radiation, and it is believed to be a leftover from the BB. The CMB is the source of the oldest light in the universe and it represents the kernel of stars and planets.

In the early stages of this CMB time, elementary particles were formed. These particles acquired mass while passing through the Higgs field and interacting with the Higgs boson [1]. These particles are mainly divided into two categories: fermions and bosons. Fermions are the most fundamental particles, known as quarks and leptons. The quarks and leptons are further divided into six flavors and corresponding antiparticles. Bosons are photon, gluon, W-Z bosons, and graviton. They carry forces, included the four main forces in the universe – electromagnetic, strong, weak, and gravitational.

The basic building blocks of matter are two composite particles, baryons and mesons, which are formed by the combination of quarks. Baryons are made of three quarks, such as protons (two up and one down quarks) and neutrons (two down and one up quarks), of the atomic nuclei. Mesons are usually found in cosmic rays and are composed of quark-antiquark pairs. Today, more than 200 subatomic particles have been discovered at sophisticated particle accelerator laboratories. Most of them are composite particles, composed of other fundamental particles.

After the creation of these elementary particles, stars, galaxies, and planets were formed, step-by-step.

First stars: 200,000,000 years after Big Bang
According to the results of NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), the first stars were formed 200 million years after the BB. The clumps of matter were brought together with the gravitational force and they grew like a growing snowball until they have enough energy to start nuclear fusion process, which is the main process behind the shiny stars up in the sky.
First Galaxies: 1,000,000,000 years after Big Bang

1.6 million galaxies have been identified according to the location of the Milky Way Galaxy by The 2 Micron All-Sky Survey (2 MASS). Figure 1.1 is a computer-generated map of our surrounding universe by the 2 MASS, which shows nearly 50,000 galaxies near our galaxy, Milky Way (2 MASS/ J. Carpenter, R. Hurt & T. H. Jarrett).

The Milky Way, which includes our solar system, began to form 5 billion years after the BB. There are approximately three hundred billion stars in our galaxy, and there are estimated to be 100 billion galaxies in the universe. Scientists do not know the structure and features of these galaxies. But then, they don’t even know everything about our galaxy.

How big are objects in the Milky Way? Everyone knows about the moon and the Earth, as well as the other planets in our solar system. The largest star in the Milky Way is VY Canis Majoris, a Red hyper-giant. It has a diameter of 280 million km, which is so big that an airplane flying at 900 km per hour would need 1100 years to circle the star. There are approximately 200 billion stars in Milk Way alone and the sun is only one of them.

When thinking about all the space in our universe, it makes the order of our own solar system and galaxy seem quite extraordinary.

A solar system in general consists of a star at the center and rotating astronomical objects (planets, moons, etc.) around that star. In our solar system, the object in the center is the sun and everything orbits around it. There are eight planets including the earth and their natural satellites orbiting the sun. So far, 3946 comets, many asteroids, and thousands of near-earth objects and minor planets have been discovered [6] around the sun. The sun is attracting all these objects with the gravitational force and they counter this attraction by means of their centrifugal force. These forces are balanced and keep the objects in their orbits. All of these are formed and located perfectly with a magnificent balance. How does this kind of order form from a disorder spontaneously?

References:

[1]       Kara, Cihan, "Will CERN Reveal the Origin of the Universe or Cause the End," The Fountain Magazine, Issue 92, 2013.
[2]       The Large Horn Antenna and the Discovery of Cosmic Microwave Background Radiation,             https://www.aps.org/programs/outreach/history/historicsites/penziaswilson.cfm
[3]       Hubble Space Telescope,             https://www.spacetelescope.org/about/history/the_man_behind_the_name/
[4]       The Shaw Prize in Astronomy in 2006,         http://www.shawprize.org/en/shaw.php?tmp=3&twoid=51
[5]       The Nobel Prize in Physics 2011,      https://www.nobelprize.org/nobel_prizes/physics/laureates/2011/
[6]       The Minor Planet Center: http://www.minorplanetcenter.net/

Takagi R. et al. Bioengineering a 3D integumentary organ system from iPS cells using an in vivo transplantation model. Science Advances, April 2016.

Skin is the human body’s largest organ, weighing 3.6 kg and having a total area of 2 m2. It acts as a waterproof shield against extreme temperatures, harmful chemicals, and infectious agents. Once skin is damaged beyond the ability of the body’s self-repair mechanisms, re-generation of patient-specific skin cells in lab conditions could be an essential tool used for successful skin grafts. Although there have been many methods developed to generate skin cells in lab conditions, none of these approaches gave rise to functional skin cells, complete with hair follicles and exocrine glands. In a recent study, scientists demonstrated the first lab-grown skin that contains hair follicles and sweat glands, making this skin akin to biological skin. Using a special cocktail of chemicals, scientists were able to first convert gum cells from mice into undifferentiated stem cells, then they directed these stem cells into mouse skin cells. Next, they grafted the artificial skin cells onto genetically modified hairless mice. The grafted skin cells ended up maturing into skin cells capable of growing hair, excreting oil, and connecting with the nerve and muscle cells of the test animals. Although these experiments were conducted only on mice, it still represents a leap of sophistication in the development of artificial skin. In the future, researchers hope that this technique will have applications for patients with serious burns, scars, or alopecia, and it could potentially be an alternative to animal testing for chemical products.

More Friends, Less Pain

Johnson KVA & Robin IM. Pain tolerance predicts human social network size. Scientific Reports, April 2016.

According to a recent study, people with large groups of friends have higher pain thresholds. In this study, scientists focused on the chemical endorphin, a major regulator of the brain’s pain and pleasure circuitry. Although these two senses seem like opposites, both are fundamentally reward behaviors, since we search for things that give us pleasure and avoid painful stimuli. Endorphins not only make us feel good, but also act as a pain reliever – one that is even stronger than morphine. Endorphins have also been shown to build and maintain social bonds. Scientists hypothesized that if endorphins help social bonding, people with more friends would have a higher endorphin count – and thus, a higher pain threshold. The research team recruited 101 adults, aged between 18 and 34, and asked them to fill out a social network questionnaire, which asked how many people they contacted on a weekly or monthly basis. Next, researchers tested the participants’ pain tolerances through the wall sit test, in which participants had to squat against a wall with their knees at a 90 degree angle and to hold the pose as long as possible. Interestingly, those with larger social networks showed significantly higher thresholds to pain. This study is one of many studies that linked social behavior and physical fitness. There has been a lot of evidence that suggests having an active social life and a bigger circle of friends can prevent depression, contribute to successful aging, and promote longevity. Our social lives are as critical to our overall health as our diets and exercise habits.

Three Potentially Habitable Planets Discovered

Gillon M et al. Temperate Earth-sized planets transiting a nearby ultracool dwarf star. Nature, May 2016.

The search for life on Earth-like planets beyond our solar system has been very active, thanks to new high-precision instruments and advanced analysis techniques. Scientists have discovered hundreds of terrestrial worlds over the past few years, including some that are the right distance from their host stars to contain liquid water. Astronomers have been investigating these habitable planets, and one research group, using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) at the La Silla Observatory in Chile’s Atacama Desert, recently discovered three Earth-like planets orbiting an ultracool dwarf star just 40 light-years from Earth. The planetary system is named TRAPPIST-1 and the three planets are designated TRAPPIST-1b, c, and d. These three planets orbit very close to the star, at 1-3% of the distance that Earth lies from the sun. A year on them passes in only 1.5-4.5 Earth days. They have sizes and temperatures similar to those of Venus and Earth, and are the most promising candidates found so far in the search for life outside our solar system. Scientists are already excited about further studying these planets in greater detail. They plan to use the Hubble space telescope to investigate whether the planets have their own atmospheres or not. If they do, analysis of the presence and proportions of water, carbon dioxide, and ozone in their atmospheres will shed light on the real possibility of “life” on these planets.

Wright DJ et al. Three planets orbiting Wolf 1061. Astrophysical Journal Letters, December 2015.

Astronomers from Australia have discovered the closest potentially habitable planet outside our solar system. They named it Wolf 1061c. It is four times the mass of Earth and only 14 light years away (126 trillion kilometers). The closest exoplanet discovered so far was Gliese 667c, which is 22 light years from earth. Wolf 1061c is located in the constellation Ophiucus and is one of three planets that orbit around a red dwarf star, Wolf 1061. Scientists find this discovery particularly exciting, because all three planets have low enough mass to have potentially solid rocky surfaces, unlike gaseous planets, such as Neptune. The one orbiting closest to Wolf 1061 would be too hot and the furthest one would be too cold. But the one in the middle, Wolf 1061c, is potentially optimum for generating temperatures just right for the formation of liquid water and, ultimately, life. Red dwarfs are known to be very active with X-ray bursts and super flares, which doom the possibility of any life. However, Wolf 1061 seems to be a quiet star, and very similar to our sun. The next challenge for scientists is to develop a method to study the atmosphere of Wolf 1061c to conclusively say whether it is conducive to life.

Most cancers are found to be avoidable

Wu S. et al. Substantial contribution of extrinsic risk factors to cancer development. Nature, December 2015.

It has been long recognized that cancer is caused by a mix of factors, including genes, lifestyle, and environment. However, the relative contributions of each factors have never been settled. A recent study found that the risk of developing most cancers is more correlated to lifestyle and environmental factors than genes and DNA mutations. The biggest risk factors are diet, sun exposure, UV radiation, tobacco, alcohol, the human papilloma virus, and hepatitis B and C. They make up between 70% and 90% of several types of cancer, including lung, colorectal, skin, and cervical. Researchers particularly focused on people who move from a low-risk cancer area to a high-risk cancer area, and found that migrated people soon developed diseases at significant rates consistent with new risky environments. They also analyzed a comprehensive set of specific mutations associated with certain cancers. Ultraviolet light, for example, creates a signature of mutations in DNA. When cross-compared, spontaneous mutations during cell division rarely reaches the frequencies of producing cancer mutations, even in tissues with high rates of cell division. In almost all cases, the research team found that some exposure to environmental factors would be needed to trigger the disease. So if you smoke or are overweight or tan for hours under the sun, you dramatically increase your odds getting cancer. You can do a lot to reduce your cancer risk; you can’t just blame “bad genes” for getting sick.

Mutant mosquitos to stop malaria

Gantz VM et al. Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Anopheles stephensi. PNAS, December 2015.

The tiny mosquito is one of the deadliest weapons in human history. Malaria is thought to be the oldest and deadliest disease. Despite intense efforts at treatment and eradication, it still is a reason for the death of approximately half a million people per year. So researchers have changed their tactics and tried to treat mosquitos instead of humans. Researchers used the revolutionary gene-editing technique CRISPR-Cas9 and generated a new breed of malaria with two genetic modifications. The first modified gene released antibodies against the malarial parasite and rendered its host immune to the parasite. The second modified gene, called “the gene drive,” would copy and paste the malaria-resistant genes into another mosquito, when mated. This two-gene system has the potential to spread malaria resistance across a wild population in just 10 generations – in other words, a single summer. Experts think that further research is needed before conducting a field trial. One potential problem would be to create a “hole” in the eco-system by changing the balance of malaria-carrying mosquito species. However, since the approach does not kill mosquitos rather make them resistant to the parasites, only a small amount of ecological damages are expected.

Our sun is a single star system, but using new technology, scientists are discovering double – and even triple! – star systems

The planets of the sun revolve around a single star, just like the planets in many systems. Revolving around a single star is the general principle, but scientists have recently discovered planets that revolve around two stars, without causing any irregularities. Planets that revolve around two stars are accepted as a new class of planets and according to calculations their numbers in the Milky Way galaxy are estimated to reach at least ten million.

How can this be possible? A planet traveling around two stars enters the gravitational field of each star during its motion, and its velocity and orbit constantly changes.

If stars can shade (eclipse) each other, it is possible for one planet to shade one or two stars. When this event takes place, the planet and stars orbit on the same plane. This intersection on the same orbital plane means that the planet and star have passed in front of each other; we can measure this due to a reduction in the amount of light emitted by the star. If the distance between the two stars is too long, these stars act as if they are isolated from each other. In that moment, the planet that is moving on one of the star’s orbits does not feel the effect of the other star. These are called S-type planets and dozens of them have been discovered in the last decade.

Interesting events take place when stars get close to each other. In such cases, the time required for stars to make a complete revolution around each other is described in days or weeks. The ability of a planet to move in “braided pathways”^[1] that will allow a stable orbit around two stars that are so close to each other cannot be a coincidental event without fine adjustments.

S-type systems are only one type of double-star systems. In P-type systems, the planet revolves around the two stars simultaneously. For this type of planet to travel in a stable orbit, the orbital distance from the stars must be longer than a critical distance. If it is closer than this critical distance, the planet’s orbit becomes progressively unstable, and it is either pulled towards one of the two stars and collides, or gets thrown into outer space. This critical distance is 2/3 of the star’s magnitude.

In a system of a single star and planet, the transit of the planet occurs as if the light makes a periodic movement, such as when a light house rotates around itself. These passes allow us to detect stars. Double-star planet systems are another example of this. It is not easy to estimate the movement of an object consisting of three elements. In a single-star system, the star’s movements are stable; thus, it is easy to estimate the movement of a planet. Yet in a double-star system, the distance between the two stars is much shorter than their distances to the planet; for this reason, these stars revolve at a higher speed around each other than the planet revolves around them. This means that the planet’s rotation is difficult to predict.

As a result, the planetary movement of a double-star system will not be periodical; different than that of a single-star system, the time of transit passes will vary according to the relative motion of the planet to the star. If the planet and the star it revolves around are moving in the same direction, the transit pass time will be longer; but if the star is located at the other half portion of the orbit and traveling in the opposite direction, the transit passing time will be much shorter.

The Kepler spacecraft and telescope that NASA launched in March 2009 is designed for detecting planets that cause reductions in the light of stars when they are passing in front of them. Today, more than two thousand twin star systems that display eclipses have been discovered. Two planets that revolve around stars eclipsing each other every 7.5 days were discovered and called the Kepler-47 system. Along with these double star systems, a triple-star system has been discovered through the Kepler telescope; the properties of this system are extraordinary.

Among these, planet Kepler-47b of the inner region completes its voyage around its stars in less than 50 days. In addition, this planet, which is not visible directly, is predicted to be a very hot planet. Since a foggy layer inhibiting its visualization is found to have formed as the result of methane gas combusting in its hot atmosphere. Kepler-47b, which is three times bigger than the Earth’s radius, is the smallest planet among those that have been discovered in two-star systems.

The planet Kepler-47c of the outer region completes its one full tour around its twin stars in 303 days and it moves in a region that is described as the habitable zone in the Milky Way galaxy. There can be liquid water present on the surface of a planet in the habitable zone. However, just being in this zone does not totally mean that the place is suitable for life. Kepler-47c is predicted to be slightly bigger than Neptune and to have an atmosphere composed of thin and bright water-vapor cloud.

Reference

William F. Welsh, Laurance R. Doyle, “Worlds with Two Suns,” Scientific American, October 2013, pp. 40-47.

S- And P- type planets traveling around two stars

Kepler-47c exists in the habitable zone and liquid water is predicted to be present on its surface.

A representative image of the Kepler 16a/b based on acquired data.

^[1] The Qur’anic verse “By the heaven full of braided pathways, surely you are in contradicting views”(Adh-Dhariyat, 51:7-8) sounds like pointing to this phenomenon.

a

She began to question religious thought under the influence of philosophy she studied when she was eighteen. She searched for answers but failed to convince herself. Since her grandmother taught her to be “honest” all the time, she decided to end her connection with the church, stating, “I do not have the faith and I still continue to go to church; this is not right.”

One day, in the library of the Sorbonne University, she encountered a half page text describing the views of Rumi written by Dr. Muhammad Iqbal. She grew confused after reading the article. Either Rumi or the Greek philosophy which she had been reading up until that time was correct. She looked for publications regarding Rumi to investigate the matter comprehensively. But she failed to find any record related to the topic in the entire library. She read Muhammad Iqbal’s book called The Reconstruction of Religious Thought in Islam in English, expecting she could reach the opinions of Rumi through him. She found many answers to her questions in this book. She became a Muslim in 1954, as a result of this enlightenment, and changed her name to Hawwa.

Hawwa was very impressed with the collections of Rumi, accepting him as a guide. She translated almost all of his and Iqbal’s works into French. She worked ten years to translate Rumi’s magnum opus the Mathnawi. She became the reason for many French intellectuals to discover and grow closer to Islam by her translations, radio speeches, and lectures. She made many visits to Turkey and attended Rumi programs.

In a live broadcast, Ms Hawwa gave the following long answer to questions such as, “Why did you choose Islam? What have you found in Rumi? Why Turkey and not another Islamic country?”

The Western media happens to have launched an attack against the religion of Islam. When you listen to French or German televisions and radios, you would hear awful statements regarding the Islamic religion. You would hear that Islam is about violence, jihad, fanaticism, etc. Despite these continuous attacks, there are scores of people in Western countries adopting Islam. I know many people who have accepted Islam in France, England, Germany, and Spain.

According to the data I have obtained from French authorities, many of the converts are intellectual people. They were seeking something and they found what they were searching and longing for in Islam. It is because their interpretations on creation and existence were not addressing these feelings anymore and also materialism disappointed them completely.

I have discovered a very different Islam than the one taught at the school or university, or depicted on newspapers and televisions. I am proud to say that the work of Rumi I last translated took ten years. This is an extraordinary book. In my opinion, the West was thirsty for spirituality. I also think this is very significant for our era. I go to Konya every year and love it there since it is the town of Rumi. I feel as if I am from Konya when I am there. I also love Turkey very much; since it represents my acquaintance with Islam, I am very happy there and I feel like a Turk. I found a religion in the Mathnawi that rejects radical religious ways, strict rulings, fanaticism, and conservative approaches; a religion which is entirely sincere, tolerant, and suitable to my beliefs.

The need for spirituality in our time is not satisfied. But I also do not think that humans can quench this by withdrawing from social life. In addition, scientific developments have demonstrated such an amazing universe. What is extraordinary of Rumi (which is not my reason for adopting Islam) is his projection and this impresses people, especially a young generation who has a passion for science. Consider that Rumi tells, ‘If you split an atom, you will find a solar system.’ He speaks of planets orbiting inside and outside of us, but also warns us to be careful. Since when these atoms open their mouths, they can eject a fire that can destroy the whole world. As seen, he talks about the dangers of the atomic bomb in the thirteenth century. It mentions the presence of nine planets, whereas modern science only proved this in the 1930s. Previously, seven planets were believed to exist. Number eight was found by a French researcher in the 1840s, and the ninth was discovered by an American scientist in 1930. However, Rumi already knew that there were nine planets back in his era. While the sun was believed to orbit earth in the West, Rumi tells that earth, like other planets, is a small planet that revolves around the sun. He also mentions other extraordinary things.

I often receive frequent phone calls, usually from intellectuals, even professors, authors, and journalists, and they tell me that, ‘Do you know Madam, I have accepted Islam and this was possible via Rumi.’

I now have translated all of his books including, ‘Majales-e Sab’a (Seven Sessions), Fihi Ma Fihi (In It What’s in It).’ The most important one is the Mathnawi. I am truly happy. Furthermore, I think that the time is very suitable for the publication of such works. This is because our world is being devastated by wars, conflicts, hatred, and aggression. However, Rumi’s works are full of love, peace, and tolerance, which are essential messages for today. True Islam is a universal religion with a perfect message of tolerance. The teachings of the prophets before Prophet Muhammad, peace be upon him, are accepted as valid. Therefore, Islam provides satisfying answers to people seeking clearer, universal and general answers compared to their own religions. Yet I am repeating once more that conversions are totally different from each other. For instance, I know people who adopted Islam suddenly. These people experienced something, saw something, and joined Islam. Some people like me, however, adopted Islam after doing many investigations, passing through many stages, completing PhD work on Islamic philosophy, but the goal as a result is the same. Spain was Muslim for 800 years; right next to it was France, and Spain was decidedly more advanced, intellectual, and civilized than France and the rest of Northern Europe.

I only assess the situation with a Western point of view and I do not mention either Turkey or Arabia. I am talking about the West. I am talking about such a tolerance in Spain, where ministers were Jewish, doctors were Christian, and Caliphs were Muslim. In this country governed by Muslims, business was advancing much faster than other countries. This was a great threat to Christian countries, kingdoms, and the Papacy. As you know, in order to get rid of something disturbing, it must be put down. The West did that. It started imperialism wars by putting down Islam. They expanded their propaganda and misinformation campaigns against Islam. For example if you ask someone in the street, ‘What do you think of Buddhism?’ They would answer, ‘I do not know,’ but when it is about, ‘the religion of Islam,’ they would reply with phrases such as, ‘Ah, yes, marrying four women, keeping them at home, having a tent.’ As you see, there is a type of partial lack of information present, there are clichés found on televisions and in newspapers; concrete symbols exist and all of these distort Islam entirely.

Today Islam is not known very well and people have gotten completely inaccurate ideas. Unfortunately, I think that these arise from failing to generate the necessary image about Islam by Muslim countries. In addition, the misinformation planted as the result of the wars of imperialism contributed to this. Unfortunately there are fractions observed among Muslim countries and this hinders the solutions needed for this and many other issues. Muslims have the same Book, the Prophet and his tradition, culture, and the Qur’anic language, which is Arabic. Yet these countries fight frequently and do not pay attention to this common heritage. In my opinion, the main reason for Westerners not to accept Islam is the lack of unity among Muslims. In fact, this is a separate issue. Islam as a religion should not be adopted through political and social reasons, but through the point of views and paradigms that it brings to the Creator, life, humans, and the universe.

In order to describe Islam as is, it is essential to read Rumi, Ibn Arabi, and briefly, the works of all the great Islamic thinkers. People get very surprised. The other day, I went to the doctor; they are very educated people. His wife, who called me in the evening, asked me ‘what are you doing now?’ I told her that I had just completed the translation of the Mathnawi. She asked what that was. I then told her that the Mathnawi mentions nuclear break down, the atomic bomb. They did not believe. As you see, people do not know the main reason of scientific developments in the middle ages.

The first medical school was established by Arabs in France. The greatest doctor of the era was in Spain. There were many successful scientists who were very ahead of their times, but nobody is aware of this. While I was doing my doctorate on Islamic philosophy at the Sorbonne University, I discovered Islam, but while studying at the university before starting my doctorate on Rumi, nobody taught us about Muslim thinkers. They were teaching German, English, Latin, and Greek philosophers.

There is a long way to go, so much to do. Now there are intellectuals who love and embrace Islam. These people should announce what lies at the essence of Islam to the world.

In her will, written to her spiritual stepson, Prof. Dr. Abdullah Ozturk, Ms Hawwa asked to be buried near the tomb of Rumi, in Konya. After she walked to the horizon of her soul on July 24, 1999, Dr. Ozturk went to great efforts to fulfill this will and she was buried at the Ucler Graveyard, near the tomb of Rumi, on December 17, 2008, exactly the time of “Seb-i Arus” the wedding day, as Rumi described death.

Astronomers have discovered a planet with the longest known orbital period. Exoplanet Kepler-421b has been identified through the Kepler observatory, a space-based telescope. It circles its star once every 704 days. More than 1800 exoplanets have been discovered so far, but compared to Kepler-421b, those had much shorter orbital periods, like a few weeks or even a few days. The host star for Kepler-421b is much like the sun, but it is little bit smaller and relatively cooler. With an orbital distance of 177 million kilometers, Kepler-421b gets about one-fourth the light from the host star as the Earth receives from the sun, which makes the exoplanet as cold as -100 °C. The unusual orbit places Kepler-421b beyond the “snow line,” which is accepted as the dividing line between rocky and gaseous planets. Outside of the snow line, water condenses into ice grains that stick together to build planets known as “gas giants.” Since gas giant planets are very close to their stars, theorists believe that many exoplanets migrate inward early in their history. However, Kepler-421b is the first example of why such migration may not be necessary.

Sunflowers’ internal clock

Plants are known to grow toward the sun to maximize the amount of energy they absorb. Sunflowers (Helianthus annuus) show the most fascinating behavior during summer, when they follow the sun as it rises in the east every morning and sets in the west every evening. In a recent study, scientists challenged the obvious explanation for this plant’s behavior: are flowers solely responding to sunlight or are there other unknown mechanisms at work? They designed a clever yet simple experiment where they grew sunflowers in chambers with a fixed overhead light that was continuously on. Surprisingly, for several days, the sunflowers under constant light kept moving as if the sun were rising in the east and setting in the west. This unexpected result suggests that sunflowers were not responding only to the direction of the light but also to an internal biological clock. Furthermore, they discovered that sunflowers bend when one side of the stem grows faster than the other. For example, the west side of the stem seems to grow faster to bend the plant towards the east in the morning. Scientists now hope to understand how an internal biological clock in sunflowers has the opposite effects on opposite sides of the stem. Sunflowers are not the only plants performing this diurnal dance; other agriculturally important crops such as soybeans and cotton exhibit the very same behavior. Solar tracking is known to boost plant yield and discovering the mechanisms of how plants track the sunlight might have important implications for improving global agricultural yields.

Friends linked by genes

It is a common observation that close friends look alike. Even centuries ago, Plato noted the tendency that good friends usually have similar appearances. Recently, a group of geneticists took this idea even further and suggest that people on average tend to choose friends who are genetically similar. The study provided convincing evidence that we have more DNA sequences in common with the people we pick as friends than we do with strangers in the same population. Researchers performed a genome-wide analysis of approximately 1.5 million markers of gene variations from 1,932 subjects of the Framingham Heart Study, which is one of the most comprehensive genetic databases. They identified 1300 pairs of non-relative friends and compared their genetic information to each other. The analyses showed that friends share similar genetic variations (around 1% genomewide), to the degree that it is as if they have the same great-great-great-grandparent – in other words, as if they were fourth cousins. Notably, friend pairs seem to have the greatest similarity in the genes that are responsible for a sense of smell and they show the most difference in immunity-related genes. Friendship entails spending a lot of time together and looking out for each other. Odors are strong behavioral cues in human psychology and people with similar olfactory preferences might like to prefer living or hanging out in similar environments. Likewise, it is potentially a big advantage that friends don’t get infected from the same microbes at the same times, so that one of them can take care of the other. As much as these anthropological implications are merely speculations with many caveats – and despite there being many obvious social, ethnical, and cultural factors that help determine friendships – the genetic basis of friendship and other social interactions may hold answers to at least some of the mysteries of human behavior.

A planet that revolves around another star outside our solar system is called an Exoplanet or Extra solar planet. Ongoing studies involving this field are carried out via simultaneous ground and space based missions and observations. Scientists are searching a small portion of the Milky Way galaxy, approximately 3000 light years away, by using ground and space telescopes, along with various other astronomic methods (1). Despite all this technology, the observation area is too big when compared to the size of the object of interest.

It has been calculated that the Milky Way, a disc shaped galaxy, consists of 200 billion stars spread over a diameter of nearly 100,000 light years and a thickness of 1000 light years. When we consider the amount of stars in a single galaxy, and the fact that there are between a hundred billion and one trillion galaxies in the universe, the number of possible exoplanets is likely much larger than those we currently know of.

Classification of exoplanets

Exoplanets are classified according to their physical, chemical, and other characteristics, along with their diameter and mass: Jupiter like; greater than Jupiter; Earth like; greater than Earth

Classifications according to surface and atmospheric temperatures are as follows: Hotter than Jupiter; colder than Neptune; colder than Jupiter; small blue dots or twin Earths.

The presences of free-floating planets which have lost their parent stars because of different formation processes or other factors have also been discovered.

One of the common features of the exoplanets currently discovered is their short distance to the star they revolve around, which is usually less than half the distance between the Earth and the Sun. The known exoplanets are also defined by their faster revolutions in much shorter periods. Therefore, larger planets that are closer to their stars can be observed easily. When these planets are passing in front of their stars, a decrease in the brightness of the star is detected via spectrometers (Figure 1).

Figure 1. Passing of a planet in front of a star and a spectrum of this event.

Radial velocity, one of the methods used to discover exoplanets, relies on the observations of a star’s kinetic fluctuations. The proximity and size of a revolving planet leads to slight changes in location and velocity of a host star. As a result of this, the star gets closer to earth and then becomes more distant, which is observed as the Doppler shift of spectral line color waves. 75 % of all known planets have been discovered using this method (Figure 2).

Figure 2. Doppler shift – radial velocity

Earth-like planets or habitable places

In an official NASA report in December 2011, the discovery of an Earth-like planet was announced for the first time. This planet, named Kepler 22b, is 600 light years away and remains the most similar one to Earth among the known heavenly bodies. The distance of Kepler 22b to its star shows a high possibility for the presence of a habitable zone.

So what does this mean?

Earth is such a special home for us humans that everything here has been assigned to serve us with delicate calculations. Factors such as the Earth’s mass, gravity, distance to the Sun, rotational and revolution velocity, chemistry, thickness of the atmosphere, magnetic shield, hydrosphere/land ratio, ecological balances, and average temperature are all perfect for biological life.

Earth revolves in such a region and position that a majority of the planetary water is in a liquid state and is not ice or vapor.Thedistance of the habitable zone to our Sun is between 135,000,000 – 225,000,000 km. Earth revolves at a 150,000,000 km distance to the Sun. The value of a habitable zone for each planet depends on the diameter, mass, heat and radiation strength of the host star. In other words, aside from the similarity of an exoplanet to Earth, a classification of its host star with in terms of size and age is also important.

Kepler 22b owns the title as the first planet to match the criteria above with its following features:

• Has a radius 2.4 times bigger than Earth
• Revolution time is 290 days (365 for Earth)
• 15% closer to its star compared to the Earth-Sun distance
• The size and surface temperature of Kepler 22b’s host star is very similar to that of the Sun’s
• The surface temperature of the planet is 22 C
• The size of the habitable zone for Kepler 22bis 133,500,000 – 240,000,000 km (Figure 3).

Figure 3. Comparison of the solar systems of Kepler 22b and Earth.

Aside from these similarities, it is noteworthy to report the problems that scientists encountered regarding Kepler 22b:

• The unknown presence of water on the surface
• No information on the gaseous contents of the atmosphere.
• The gravitational force is 2.5 times greater than on Earth.
• Rocks constitute the surface instead of soil.

The hardest part is that Kepler 22bremains 600 light years away from us. This means it would take us 11 billions years to get there with today’s fastest spacecrafts. Who knows when we will be able to decrease this time with the advent of superior technology.

What do religious scholar say about life in outer space?

Among His manifest signs is the creation of the heavens and the earth, and that He has dispersed in both of them living creatures. And He has full power to gather them together when He wills. (Ash-Shura 42:29)

While interpreting the Qur’anic verse above, Fethullah Gülen notes the following:

“Since the earliest times, this verse has been taken as a proof for the view that there are living creatures, whether resembling human beings or not, in the places other than the earth. This view may be true. The second part of the verse, ‘He has full power to gather them together when He wills,’ has been understood that these creatures and human beings will possibly come together either in this world or in that of the other creatures. … there may be earth-like globes in the heaven where creatures resembling earthly ones live.” (Gülen 2012, 272-273)

“Perhaps people will not be able to reach those places individually or as a whole generation, but this can be achieved by mankind as a species. In other words, when the Divine Will manifests itself in that direction, humans here can encounter those other life forms.” (Gülen 2007, 232)

This commentary reflects what Bediuzzaman Said Nursi had said decades ago:

“The earth, although much smaller than other heavenly bodies, is so densely inhabited by living creatures that even its grossest and most rotten parts are full of living things, such as micro-organisms. This shows that those infinite firmaments, with their numerous stars and constellations, are inhabited by conscious, living beings …” (Nursi 2010, 530-531) 29th Word, First Aim, First Fundamental)

Nebiyev is a professor of physics in Azerbaijan.

References

• http://kepler.nasa.gov/
• http://planetquest.jpl.nasa.gov/
• http://en.wikipedia.org/wiki/Habitable_zone
• Gülen, M. Fethullah. 2007. Kendi iklimimiz, Istanbul, Nil Yayinlari.
• Gülen. M. Fethullah. 2012. Reflections on the Qur’an: Commentaries on Selected Verses, NJ: Tughra Books.
• Nursi, Bediuzzaman Said. 2010. The Words, (29th Word) NJ: The Light, Inc.
• Chris Kitchin Exoplanets: Finding, Exploring, and Understanding Alien Worlds- (www.springer.com/series/6960)-2012
• Mercy, G., P. Butler et al. 2005. “Observed Properties of Exoplanets: Masses, Orbits, and Metallicitie”.. Progress of Theoretical Physics Supplement, Vol. 158, No. 24-42.

Every human being asks the question “why,” though at different levels, to explain the unexplained. It follows a pattern of questions, like “Why did the financial crisis in the U.S. happen in August 2008?” “Why did the space shuttle Challenger explode?” “Why did the terrorists commit the September 11 attacks?” In statistical terms, such unexpected events are named “outliers,” however, they are part of the system and among the components constituting the overall system’s complex behavior. Thus, they need to be part of the explanation in order for the explanation to be complete. We are naturally tempted to come up with universal explanations of the complexity behind these major events so that we can be ready when a similar thing happens again. Though simple mathematical equations or relationships relate to us better and provide a universal explanation, they are typically practical only when the outliers are excluded from the system behavior. Statistics help us greatly in quantifying and characterizing the outliers, especially in the form of probabilistic expressions, such as “there is a 30% chance of a hurricane next week.”

Understanding the complexity around us involves the development of a model that is simple enough for us to comprehend but yet universal enough to capture most of the dynamics of the complexity. The simpler and the more universal the model, the more powerful it is. The universality of a model, however, is hindered by the potential inability to capture something unexpected. The tradeoff between simplicity and universality exists in all modeling efforts; and the models finding the delicate balance in this tradeoff are the most effective ones. A simple mathematical relationship known as “the power law” has been used extensively to characterize and model various natural and social phenomena.

What is the Power Law?

The “power law” does not refer to a misconception that “whoever has power will rule,” but rather it refers to a particular way of characterizing dependency between two quantities. When the number or frequency of an object or event varies as a power of some attribute of that object (e.g., its size), the number or frequency is said to follow a power law. In more general terms, there exists a power law relationship between x and y if y is growing or reducing polynomially when x is growing linearly (y _͌ x^–α). Mathematically speaking, this means that the relationship between y and x is mainly characterized by the exponent -a. An exponent is simply shorthand for multiplying that number of identical factors. So, 4³ is the same as 4x4x4; that is three identical factors of 4. As shown in Figure 1, a quantity with an exponent has three components: the base, the exponent, and the coefficient. So, for 4³, the base is 4, the exponent is 3, and the coefficient is an implicit 1.

Figure 1: Description of an exponent in a power law relationship.

Figure 2: Sample power law relationships between x and y, where y = x^–α.

The power law relationships are traditionally expressed with a negative exponent, which simply means the inverse of the quantity. That is, y _͌ x^–α is equivalent to y _͌ 1/x^α. For example, when a is 2, y will reduce from 1/4 (i.e. 0.25) to 1/9 (i.e. ~0.11) if x grows from 2 to 3. Likewise, when a is 0.5, y will reduce from 1/2 (i.e. 0.5) to 1/3 (i.e. 0.33) if x grows from 4 to 9. For those who enjoy graphs, Figure 2 illustrates these mathematical relationships in linear and logarithmic scales.

Power law on different scales: Atoms to planets

To start with, gravitation, acoustics, electrostatics, and light and electromagnetic radiation, all exhibit a form of power law in that physical quantity or strength that is inversely proportional to the square of the distance, which corresponds to a power exponent of 2. [1] Gravitational force between two particles, the electrostatic force of attraction between two electrically charged particles, the intensity of sound signals coming from a source, and finally the intensity of light or electromagnetic field coming from a source all follow a power law with respect to the distance.

What makes the power law relationships more interesting is their independence from scale or size of the measures being related to each other. This is why we sometimes call power law relationships as “scale-free” relationships or “scale-invariance.” For example, the gravitational force between two spherical particles decays with a power exponent of 2 regardless of the sizes of the particles though the actual force is certainly dependent on the particle sizes. So, the particles can be at nano scales (e.g. a group of atoms) or macro scales (e.g. a planet), but the relationship stays the same!

Power law in frequency: Wealth, terror, and earthquakes

A common usage of power law relationships has been to model and understand frequency of a varying measure. A power law typically very well represents the distribution of wealth in a society. [2] According to a recent study, the distribution of wealth in China during the years 2003–2005 follows a power law with an exponent ranging from 1.758 to 2.285. If we consider an average exponent of 2 for Chinese wealth distribution, this means that if there are 1 million Chinese people who owned $1000 there were 1000 that owned $1M. Thus, the power law essentially expresses how skewed the distribution of a frequency is (see Figure 2). The larger the power exponent, the more skewed the distribution. In this case, a larger power exponent means a more imbalanced wealth distribution while a power exponent of 1 refers to an evenly distributed wealth.

Many other social patterns exhibit power law. A recent study showed that it exists even in terror events! The number of casualties per insurgent event and the number of insurgent events per day follow a power law. [3] Historical data for the last two centuries show further that the number of casualties per war or a terror attack follows a power law distribution. What is even more interesting is that the number of casualties and the number of attacks within an insurgent conflict both follow power law. That is, when only a particular conflict between two countries or ethnic groups is considered, the number of casualties per insurgent event and the number of insurgent events per day follow the power law. This suggests a “self-similar” pattern. Likewise, traffic measurements for many systems show power law distributions of size. For instance, if one observes the data traffic on an Internet connection and counts the number of bytes being transmitted per hour over that connection, a power law distribution of the count of bytes will emerge. Further, if this counting is done per minute instead of per hour, a similar distribution will still emerge – again showing a self-similar pattern. [4]

The power law has been observed in several natural phenomena as well. The frequency of earthquake magnitudes follows a power law. [5] This refers to the intuitive notion that the number of earthquakes with small magnitudes (which humans do not even feel) is much larger than the number of earthquakes with large magnitudes, (which can kill many humans). Small earthquakes are the norm while large ones the outliers. However, without the outliers, there is no power law distribution! Thus, the power law distribution of a quantity comes with an interesting observation: If a quantity is indeed following a power law distribution, then the likelihood of an outlier event increases as the time goes by without an outlier event. This is why geoscientists would make comments like “The region X is due for a major earthquake!” indicating that the region X has not been receiving a major earthquake (i.e. an outlier) for several years. The issue, though, is determining the threshold for an outlier is typically ambiguous and may require many years of measurements and data, which may be impractical.

Power law in growth: Rich get richer

Growth of systems also exhibit power law in various ways. Social growth follows power law due to the well-known “rich get richer” rule, which refers to the intuition that “important” people in the society attract more of the attention of newcomers. This dynamic situation is observed, for example, in the growth of the Internet. Several studies [6] showed that the connections between Internet Service Providers (ISPs) (e.g., AOL, Yahoo!, AT&T, Sprint) follow a power law distribution in that the number of connections per ISP (which shows how well an ISP is connected to the rest of the world) is represented by power law. In other words, there are few ISPs with many connections to other ISPs while most ISPs have a few connections to the others. This is believed to be due to the “rich get richer” rule since an existing ISP with many connections is more likely to gain the business of a new ISP who is joining to the Internet. So, it is somewhat an economic pattern too.

If economics (or the money) is taken out of the picture, social growth still exhibits power law. Online social networks such as Facebook, LinkedIn, and Flickr are clearly following a power law distribution. It is found that the power exponents are in the range of 2.5 to 3.7, indicating a highly imbalanced social growth pattern where few people are at the “center” of the social network with hundreds or thousands of friends, and many people have only one or two friends. [7] Again, the typical explanation for this growth pattern has been the “rich get richer” rule, but “richness” refers to the number of existing friends in this context rather than money.

Physical growth shows power law too in many ways. For instance, roughness of a growing surface as time goes by follows a power law distribution with an exponent ranging between 0 and 1 where an exponent of 0 refers to a smooth growth and 1 refers to a stiff growth. The surface roughness is measured by the variance of heights of surface locations. [8]

Does it really exist? Why does it exist?

Verifying existence of a power law distribution is not easy and requires enough number of samples to show the “tail” of the distribution. The tail of the distribution refers to the samples with large (or rare) values. For example, for the power law distributions in Figure 2, the portion of the distribution when x is greater than 10 (i.e. x>10) roughly corresponds to the “tail.” The tail corresponds to the rare samples. Though statistical theory calls those rare samples “outliers,” the distribution will not be a power law distribution without them. They are strictly parts of pieces that constitute a power law relationship, and observing them typically requires long periods or large numbers of measurements. Due to this difficulty, the existence of the power law is questioned for many real systems. Most of the time, claims of the existence of the power law typically come with an error factor indicating the confidence of the claim. The bottom-line is to observe trends in the samples and thus establish sufficient confidence (e.g., more than 95%) that the power law distribution does exist in the samples.

For those systems with clear exhibition of power law, the root causes of it have been of high interest. The “rich get richer” rule is intuitively one of the root causes, and it is intuitively a natural dynamic to get attracted by a rich member rather than a poor one. Growth certainly naturally follows the “rich get richer” rule, but we have system components slowing their growth, flattening, and then deteriorating. So, not everything is growing, and actually, we have as many things deteriorating as growing. For instance, participants join or leave the Internet or the social networks, and likewise, people join (i.e. birth) or leave (i.e. death) society. How does the power law stay in such systems then?

Due to the “rich get richer” intuition, the power law is considered to be the signature of “self-organization.” The fact that so many natural or synthetic systems are exhibiting this signature deserves the question: “Is it really self-organization?” Maintaining a global power law distribution for a system requires either (i) every member joining or leaving the system according to the “rich get richer” rule and having global knowledge of the whole system or (ii) somebody who knows everything about the system and gives explicit direct orders to each member when they are joining or leaving. Which one is more likely?

Murat Yuksel is an Assistant Professor at the CSE Department of The University of Nevada – Reno (UNR), Reno, NV.

References

[1] Wikipedia, “Inverse-square law,” http://en.wikipedia.org/wiki/Inverse-square_law

[2] M. A. Santos, R. Coelho, G. Hegyi, Z. Néda, and J. Ramasco. 2007. “Wealth distribution in modern and medieval societies,” The European Physical Journal, Volume 143, Number 1, pages 81-85.

[3] J. C. Bohorquez, S. Gourley, A. R. Dixon, M. Spagat, and N. F. Johnson. 2009. “Common ecology quantifies human insurgency,” Nature, Volume 462, December, pages 911-914.

[4] T. Karagiannis, M. Molle, and M. Faloutsos. 2004. “Long-Range Dependence: Ten Years of Internet Traffic Modeling,” IEEE Internet Computing, September/October, pages 57-64.

[5] T. Lay and T. Wallace. 1995. Modern Global Seismology, Academic Press, San Diego, CA.

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