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non-gravitational physics familiar from STR, albeit only approximately. But overall spacetime is curved, and local inertial frames may tip, bend and twist as we move from one region to another. The structure of curved spacetime is encoded in the metric field tensor gab, with the curvature encoding gravity at the same t... |
the metric field, geometrized away. Since the spacetime structure encodes gravity and inertia, and in a Mach-heavy theory these phenomena should be completely determined by the relational distribution of matter (and relative motions), Einstein wished to see the metric as entirely determined by the distribution of matte... |
a partial-determination relation. We cannot go into the mathematical details necessary for a full discussion of the successes and failures of Mach-heavy in the GTR context. But one can see why the Machian interpretation Einstein hoped he could give to the curved spacetimes of his theory fails to be plausible, by consid... |
the first place, for our hovering rocket ship, if we are to attribute the gravity field it feels to matter, there has got to be all this other matter in the universe. But if we regard the rocket as a mere ‘test body’ (not itself substantially affecting the gravity present or absent in the universe), then we can note th... |
according to GTR, if we remove all the stars, galaxies, planets etc. from the world, the gravitational field does not disappear. On the contrary, it stays basically the same locally, and globally it takes the form of empty Minkowski spacetime, precisely the quasi-absolute structure Einstein was hoping to eliminate. Sol... |
matter (e.g., a rocket ship ejecting a stream of particles to push itself forward) are hard to come by, and in fact a realistic two-body exact solution has yet to be discovered. But numerical methods can be applied for many purposes, and physicists do not doubt that something like our accelerating rocket — in otherwise... |
according to the theory. We see clearly, then, that GTR fails to satisfy Einstein's own understanding of Mach's Principle, according to which, in the absence of matter, space itself should not be able to exist. A second example: GTR allows us to model a single rotating object in an otherwise empty universe (e.g., a neu... |
variety says that such rotation is impossible, since it can only be understood as rotation relative to some sort of absolute space. In the case of GTR, this is basically right: the rotation is best understood as rotation relative to a ‘background’ spacetime that is identical to the Minkowski spacetime of STR, only ‘cur... |
the region of the star. On the other hand, there is one charge of failure-to-relativize-motion sometimes leveled at GTR that is unfair. It is sometimes asserted that the simple fact that the metric field (or the connection it determines) distinguishes, at every location, motions that are ‘absolutely’ accelerated and/or... |
GTR fails to embody a folk-Leibniz style general relativity of motion (e.g. Earman (1989), ch. 5). We think this is incorrect, and leads to unfairly harsh judgments about confusion on Einstein's part. The local inertial structure encoded in the metric would not be ‘absolute’ in any meaningful sense, if that structure w... |
relationally specified matter-energy distribution. Einstein was not simply confused when he named his gravity theory. (Just what is to be understood by “the relationally specified matter-energy distribution” is a further, thorny issue, which we cannot enter into here.) GTR does not fulfill all the goals of Mach-heavy, ... |
(Einstein 1918). And yet … GTR comes tantalizingly close to achieving those goals, in certain striking ways. For one thing, GTR does predict Mach-heavy effects, known as ‘frame-dragging’: if we could model Mach's thick-walled bucket in GTR, it seems clear that it would pull the water slightly outward, and give it a sli... |
sense as the bucket (even if the big bucket's walls were not actually touching the water. While GTR does permit us to model a lone rotating object, if we model the object as a shell of mass (instead of a solid sphere) and let the size of the shell increase (to model the ‘sphere of the fixed stars’ we see |
around us), then as Brill & Cohen (1966) showed, the frame-dragging becomes complete inside the shell. In other words: our original Minkowski background structure effectively disappears, and inertia becomes wholly determined by the shell of matter, just as Mach posited was the case. This complete determination of inert... |
models, including the Friedman-Robertson-Walker-Lemâitre Big Bang models that best match observations of our universe. Finally, it is important to recognize that GTR is generally covariant in a very special sense: unlike all other prior theories (and unlike many subsequent quantum theories), it postulates no fixed ‘pri... |
Newtonian mechanics and STR, can be put into a generally covariant form. But when this is done, there are inevitably mathematical objects postulated as part of the formalism, whose role is to represent absolute elements of spacetime structure. What is unique about GTR is that it was the first, and is still the only ‘co... |
such absolute elements in its covariant equations. The spacetime structure in GTR, represented by the metric field (which determines the connection), is at least partly ‘shaped’ by the distribution of matter and energy. And in certain models of the theory, such as the Big Bang cosmological models, some authors have cla... |
local ‘gravitational field’ of Einstein's equivalence principle — are entirely fixed by the matter distribution throughout space and time, just as Mach-heavy requires (see, for example, Wheeler and Cuifollini 1995). Absolutists and relationists are thus left in a frustrating and perplexing quandary by GTR. Considering ... |
remain absolute, or nearly-totally-absolute, according to the theory. On the other hand, considering its most Mach-friendly models, which include all the models taken to be good candidates for representing the actual universe, we may be inclined to say: motion in our world is entirely relative; the inertial effects nor... |
of rotations and accelerations relative to the cosmic matter, just as Mach hoped. But even if we agree that motions in our world are in fact all relative in this sense, this does not automatically settle the traditional relationist/absolutist debate, much less the relationist/substantivalist debate. Many philosophers (... |
the Mach-friendly status of our spacetime, and argue nevertheless that we should understand that spacetime as a real thing, more like a substance than a mere ideal construct of the mind as Leibniz insisted. (Nerlich (1994) and Earman (1989), we suspect, would take this stance.) Some, though not all, attempts to convert... |
agree to a certain extent, we think that nevertheless there are a series of issues that have motivated thinkers again and again; indeed, those that we identified in the introduction. (One quick remark: Rynasiewicz is probably right that the issues cannot be expressed in formally precise terms, but that does not mean th... |
natural temptation for those who hold that there is ‘nothing but the relative positions and motions between bodies' (and more so for their readers) to add ‘and all such motions are equal’, thus denying the existence of true motion. However, arguably — perhaps surprisingly — no one we have discussed has unreservedly hel... |
considered motion ‘properly speaking’ to be privileged, Leibniz introduced ‘active force’ to ground motion (arguably in his mechanics as well as metaphysically), and Mach's view seems to be that the distribution of matter in the universe determines a preferred standard of inertial motion. (Again, in general relativity,... |
allow true motions if they offer an analysis of them in terms of the relations between bodies. Given this logical point, and given the historical ways thinkers have understood themselves, it seems unhelpful to characterize the issues in (i) as constituting an absolute-relative debate, hence our use of the term ‘true’ i... |
second question: (ii) is true motion definable in terms of relations or not? (Of course the answer depends on what kind of definitions will count, and absent an explicit definition — Descartes' proper motion for example — the issue is often taken to be that of whether true motions supervene on relations, as Newton's gl... |
It seems reasonable to call this issue that of whether motion is absolute or relative. Descartes and Mach are relationists about motion in this sense, while Newton is an absolutist. Leibniz is also an absolutist about motion in his metaphysics, and if our reading is correct, also about the interpretation of motion in t... |
Leibniz's views runs contrary to his customary identification as relationist-in-chief, but we will clarify his relationist credentials below. Finally, we have discussed (ii) in the context of relativity, first examining Maudlin's proposal that the embedding of a relationally-specified system in Minkowski spacetime is i... |
be held to satisfy the relational-definability question of (ii), but in any case it cannot be carried over to the context of general relativity theory. In the case of GTR we linked relational motion to the satisfaction of Mach's Principle, just as Einstein did in the early years of the theory. Despite some promising fe... |
of its models, we saw that Mach's Principle is not fully satisfied in GTR as a whole. We also noted that in the absence of absolute simultaneity, it becomes an open question what relations are to be permitted in the definition (or supervience base) — spacetime interval relations? Instantaneous spatial distances and vel... |
Barbour has argued that GTR is fully Machian, using a 3-d relational-configuration approach. See Barbour, Foster and Murchadha 2002.) The final issue is that of (iii) whether absolute motion is motion with respect to substantival space or not. Of course this is how Newton understood acceleration — as acceleration relat... |
motion for them is with respect to substantival Galilean spacetime (or rather, since they know Newtonian mechanics is false, they hold that this is the best interpretation of that theory). Leibniz denied that motion was relative to space itself, since he denied the reality of space; for him true motion was the possessi... |
(our adjective not his) about motion he was simultaneously a relationist about space: ‘space is merely relative’. Following Leibniz's lead we can call this debate the question of whether space is absolute or relative. The drawback of this name is that it suggests a separation between motion and space, which exists in L... |
no better description presents itself. Others who are absolutists about motion but relationists about space include Sklar (1974) and van Fraassen (1985); Sklar introduced a primitive quantity of acceleration, not supervenient on motions relative to anything at all, while van Fraassen let the laws themselves pick out th... |
proposals are successful; (even) stripped of Leibniz's Aristotelian packaging, can absolute quantities of motion ‘stand on their own feet’? And under what understanding of laws can they ground a standard of inertial motion? Huggett (2006) defends a similar position of absolutism about motion, but relationism about spac... |
is nothing to space but relations between bodies, but that absolute motions supervene — not on the relations at any one time — but on the entire history of relations. Works cited in text - Aristotle, 1984, The Complete Works of Aristotle: The Revised Oxford Translation, J. Barnes (ed.), Princeton: Princeton University ... |
a Dynamical Perspective, Oxford: Oxford University Press. - Descartes, R., 1983, Principles of Philosophy, R. P. Miller and V. R. Miller (trans.), Dordrecht, London: Reidel. - Dorling, J., 1978, “Did Einstein need General Relativity to solve the Problem of Space? Or had the Problem already been solved by Special Relati... |
4: 411-462. - Einstein, A., Lorentz, H. A., Minkowski, H. and Weyl, H., 1952, The Principle of Relativity. W. Perrett and G.B. Jeffery, trs. New York: Dover Books. - Föppl, A. “Über absolute und relative Bewegung,” Sitzungsberichte der Münchener Akad.. 35:383. - Friedländer, B. and J., 1896, Absolute und relative Beweg... |
Space-Time Theories: Relativistic Physics and Philosophy of Science, Princeton: Princeton University Press. - Garber, D., 1992, Descartes' Metaphysical Physics, Chicago: University of Chicago Press. - Garber, D. and J. B. Rauzy, 2004, “Leibniz on Body, Matter and Extension,” The Aristotelian Society: Supplementary Volu... |
G. Alexander (ed.), Manchester: Manchester University Press, 1956. - Lodge, P., 2003, “Leibniz on Relativity and the Motion of Bodies,” Philosophical Topics, 31: 277-308. - Mach, E., 1883, Die Mechanik in ihrer Entwickelung, historisch-kritisch dargestellt. 2nd edition. Leipzig: Brockhaus. English translation (6th edit... |
Cosmology Really Inconsistent?,” Philosophy of Science 62, no. 4. - Maudlin, T., 1993, “Buckets of Water and Waves of Space: Why Space-Time is Probably a Substance,” Philosophy of Science, 60:183-203. - Minkowski, H. (1908). “Space and time,” In Einstein, et al. (1952), pp. 75-91. - Nerlich, Graham, 1994, The Shape of ... |
C., 1870, Ueber die Principien der Galilei-Newton'schen Theorie. Leipzig: B. G. Teubner, 1870. - Newton, I., 2004, Newton: Philosophical Writings, A. Janiak (ed.), Cambridge: Cambridge University Press. - Newton, I. and I. B. Cohen, 1999, The Principia: Mathematical Principles of Natural Philosophy, I. B. Cohen and A. ... |
1995, “Mach's Principle before Einstein,” in J. Barbour and H. Pfister (eds.) Mach's Principle: From Newton's Bucket to Quantum Gravity: Einstein Studies, Vol. 6. Boston: Birkhäuser, pp.9-57. - Norton, J., 1993, “A Paradox in Newtonian Cosmology,” in M. Forbes , D. Hull and K. Okruhlik (eds.) PSA 1992: Proceedings of t... |
Vol. 2. East Lansing, MI: Philosophy of Science Association, pp. 412-20. - –––, 1992, “Einstein, Nordström and the Early Demise of Scalar, Lorentz-Covariant Theories of Gravitation,” Archive for History of Exact Sciences, 45: 17-94. - Pooley, O., 2002, the Reality of Spacetime, D.Phil thesis, Oxford University. - Ray, ... |
T., 2003, “Leibniz on Force and Absolute Motion,” Philosophy of Science, 70: 553-573. - Rynasiewicz, R., 1995, “By their Properties, Causes, and Effects: Newton's Scholium on Time, Space, Place, and Motion — I. The Text,” Studies in History and Philosophy of Science, 26: 133-153. - Sklar, L., 1974, Space, Time and Spac... |
2000, “Spacetime Models for the World,” Studies in History and Philosophy of Modern Physics, 31B: 171-186. - St. Andrews School of Mathematics and Statistics Index of Biographies - The Pittsburgh Phil-Sci Archive of pre-publication articles in philosophy of science - Ned Wright's Special Relativity tutorial - Andrew Ha... |
SAN FRANCISCO, Dec. 29, 2008 -- Facial expressions of emotion are hardwired into our genes, according to a study published today in the Journal of Personality and Social Psychology. The research suggests that facial expressions of emotion are innate rather than a product of cultural learning. The study is the first of ... |
individuals use the same facial expressions, producing the same facial muscle movements in response to specific emotional stimuli. The study also provides new insight into how humans manage emotional displays according to social context, suggesting that the ability to regulate emotional expressions is not learned throu... |
sighted and blind judo athletes at the 2004 Summer Olympics and Paralympic Games. More than 4,800 photographs were captured and analyzed, including images of athletes from 23 countries. "The statistical correlation between the facial expressions of sighted and blind individuals was almost perfect," Matsumoto said. "Thi... |
Matsumoto found that sighted and blind individuals manage their expressions of emotion in the same way according to social context. For example, because of the social nature of the Olympic medal ceremonies, 85 percent of silver medalists who lost their medal matches produced "social smiles" during the ceremony. Social ... |
Duchenne smiles, cause the eyes to twinkle and narrow and the cheeks to rise. "Losers pushed their lower lip up as if to control the emotion on their face and many produced social smiles," Matsumoto said. "Individuals blind from birth could not have learned to control their emotions in this way through visual learning ... |
It could be that our emotions, and the systems to regulate them, are vestiges of our evolutionary ancestry. It's possible that in response to negative emotions, humans have developed a system that closes the mouth so that they are prevented from yelling, biting or throwing insults." |
Feb. 8, 2006 Older Americans with high blood pressure and moderate to severe chronic kidney disease have a greater chance of developing heart disease than people with normal kidney function. This finding is one of three in a new paper published in the Feb. 7 issue of the Annals of |
Internal Medicine. The study also found these patients are at higher risk for developing heart disease than kidney failure (end stage renal disease). Lastly, it found for the first time that new types of drugs such as ACE inhibitors and calcium-channel blockers are no better than older type diuretic drugs, |
also called water pills, in preventing heart disease, and may be even less effective at preventing heart failure in patients with chronic kidney disease. Lead author of the study is Mahboob Rahman, M.D., M.S., of Case Western Reserve University School of Medicine, University Hospitals of Cleveland and the Louis Stokes |
Cleveland VA Medical Center. The study was sponsored by the National Heart Lung and Blood Institute and coordinated by the Clinical Trials Center at the University of Texas School of Public Health in Houston. The study looked at more than 31,000 men and women 55 years and older who have |
high blood pressure and one other risk factor of cardiovascular disease, such as diabetes. A blood test was used to determine kidney function and severity of disease. Patients with moderate chronic kidney disease had a 38 percent greater chance of developing heart disease and a 35 percent increase in overall |
cardiovascular disease (which includes heart disease, stroke, heart failure and others) than those with normal kidney function. In addition, patients with moderate to severe chronic kidney disease were twice as likely to develop heart disease than to experience kidney failure. Rahman said the researchers are not quite ... |
and severe kidney disease leads to greater risk in heart disease. "It may be related to other factors associated with renal failure, such as anemia or abnormalities of calcium or phosphorus metabolism, for example. We are participating in other ongoing studies to establish the connections," he said. The study also |
confirmed other earlier findings that diuretics are as effective as or better for preventing cardiovascular disease than newer drugs. "Overall, ACE inhibitors and diuretics were about equally likely to protect against heart attacks," said Rahman, "but diuretics seemed more effective at preventing other kinds of cardiov... |
and heart failure." Calcium-channel blockers were about equal in protecting against all cardiovascular disease, but diuretics were more effective at preventing heart failure. These results held for all participants regardless of kidney function. Rahman cautioned patients not to stop taking their medications after readi... |
their physicians. He added, "Exercise, maintaining optimal body weight, smoking avoidance, and maintaining low cholesterol levels -- these are all things that should be done with renewed emphasis in most patients with high blood pressure. Most patient with hypertension and chronic kidney disease will require multiple m... |
pressure. Our results demonstrate that the risk for cardiovascular disease is lower if one of the medications is a diuretic." He recommends patients who have high blood pressure talk to their doctors about measuring their kidney function to determine if they are suffering from chronic kidney disease. Other social bookm... |
and sharing tools: Note: Materials may be edited for content and length. For further information, please contact the source cited above. Note: If no author is given, the source is cited instead. |
Jan. 30, 2009 A new way of making LEDs could see household lighting bills reduced by up to 75% within five years. Gallium Nitride (GaN), a man-made semiconductor used to make LEDs (light emitting diodes), emits brilliant light but uses very little electricity. Until now high production costs have made |
GaN lighting too expensive for wide spread use in homes and offices. However the Cambridge University based Centre for Gallium Nitride has developed a new way of making GaN which could produce LEDs for a tenth of current prices. GaN, grown in labs on expensive sapphire wafers since the 1990s, |
can now be grown on silicon wafers. This lower cost method could mean cheap mass produced LEDs become widely available for lighting homes and offices in the next five years. Based on current results, GaN LED lights in every home and office could cut the proportion of UK electricity used |
for lights from 20% to 5%. That means we could close or not need to replace eight power stations. A GaN LED can burn for 100,000 hours so, on average, it only needs replacing after 60 years. And, unlike currently available energy-saving bulbs GaN LEDs do not contain mercury so |
disposal is less damaging to the environment. GaN LEDs also have the advantage of turning on instantly and being dimmable. Professor Colin Humphreys, lead scientist on the project said: “This could well be the holy grail in terms of providing our lighting needs for the future. We are very close |
to achieving highly efficient, low cost white LEDs that can take the place of both traditional and currently available low energy light bulbs. That won’t just be good news for the environment. It will also benefit consumers by cutting their electricity bills.” GaN LEDs, used to illuminate landmarks like Buckingham |
Palace and the Severn Bridge, are also appearing in camera flashes, mobile phones, torches, bicycle lights and interior bus, train and plane lighting. Parallel research is also being carried out into how GaN lights could mimic sunlight to help 3m people in the UK with Seasonal Affective Disorder (SAD). Ultraviolet |
rays made from GaN lighting could also aid water purification and disease control in developing countries, identify the spread of cancer tumours and help fight hospital ‘super bugs’. Funding was provided by the Engineering and Physical Sciences Research Council (EPSRC). About GaN LEDs A light-emitting diode (LED) is a ... |
diode that emits light when charged with electricity. LEDs are used for display and lighting in a whole range of electrical and electronic products. Although GaN was first produced over 30 years ago, it is only in the last ten years that GaN lighting has started to enter real-world applications. |
Currently, the brilliant light produced by GaN LEDs is blue or green in colour. A phosphor coating is applied to the LED to transform this into a more practical white light. GaN LEDs are currently grown on 2-inch sapphire. Manufacturers can get 9 times as many LEDs on a 6-inch |
silicon wafer than on a 2-inch sapphire wafer. In addition, edge effects are less, so the number of good LEDs is about 10 times higher. The processing costs for a 2-inch wafer are essentially the same as for a 6-inch wafer. A 6-inch silicon wafer is much cheaper to produce |
than a 2-inch sapphire wafer. Together these factors result in a cost reduction of about a factor of 10. Possible Future Applications - Cancer surgery. Currently, it is very difficult to detect exactly where a tumour ends. As a result, patients undergoing cancer surgery have to be kept under anaesthetic |
while cells are taken away for laboratory tests to see whether or not they are healthy. This may need to happen several times during an operation, prolonging the procedure extensively. But in the future, patients could be given harmless drugs that attach themselves to cancer cells, which can be distinguished |
when a blue GaN LED is shone on them. The tumour’s edge will be revealed, quickly and unmistakably, to the surgeon. - Water purification. GaN may revolutionise drinking water provision in developing countries. If aluminium is added to GaN then deep ultra-violet light can be produced and this kills all |
viruses and bacteria, so fitting such a GaN LED to the inside of a water pipe will instantly eradicate diseases, as well as killing mosquito larvae and other harmful organisms. - Hospital-acquired infections. Shining a ultra-violet GaN torch beam could kill viruses and bacteria, boosting the fight against MRSA and |
C Difficile. Simply shining a GaN torch at a hospital wall or trolley, for example, could kill any ‘superbugs’ lurking there. Other social bookmarking and sharing tools: The above story is reprinted from materials provided by Engineering and Physical Sciences Research Council (EPSRC). Note: Materials may be edited for ... |
Mar. 6, 2013 Boys are right-handed, girls are left ... Well at least this is true for sugar gliders (Petaurus breviceps) and grey short-tailed opossums (Monodelphis domestica), according to an article in BioMed Central’s open access journal BMC Evolutionary Biology that shows that handedness in marsupials is dependent ... |
the absence of a corpus collosum, the part of the brain which in placental mammals allows one half of the brain to communicate with the other. Many animals show a distinct preference for using one hand/paw/hoof over another. This is often related to posture – an animal is more likely to show manual laterality if it is ... |
the difficulty of the task, more complex tasks show a handed preference, or even with age. As an example of all three: crawling human babies show less hand preference than toddlers. Some species also show a distinct sex effect in handedness but among non-marsupial mammals this tendency is for left-handed males and righ... |
State University show that male quadruped marsupials, such as who walk on all fours, tend to be right-handed while the females are left-handed, especially as tasks became more difficult. Dr Yegor Malashichev from Saint Petersburg State University who led this study explained why they think this has evolved, “Marsupials... |
halves of the mammalian brain together. Reversed sex related handedness is an indication of how the marsupial brain has developed different ways of the two halves of the brain communicating in the absence of the corpus callosum.” Other social bookmarking and sharing tools: - Andrey Giljov, Karina Karenina, Yegor Malash... |
Web edition: March 4, 2013 Pregnant women taking DHA, an omega-3 fatty acid in fish oil, give birth to babies that score slightly better on several health measurements than those born to women who don’t take the supplement, a study has found. DHA, or docosahexaenoic acid, is a nutrient that promotes brain development (... |
University of Kansas Medical Center in Kansas City and her colleagues randomly assigned 350 women to take daily capsules of either a placebo or DHA starting midway through pregnancy. Babies born to the women who took DHA were slightly longer and heavier than the other babies and were less apt to spend time in the inten... |
preterm birth, defined as birth before the 37th week of gestation, didn’t differ substantially between the groups. But among preterm babies, those in the DHA group spent an average of nine days in the hospital compared with 41 days for those in the placebo group. While only one of 154 babies in the DHA group was born v... |
before 34 weeks’ gestation — seven of 147 babies to non-DHA mothers were born that early, Carlson and colleagues report in the April American Journal of Clinical Nutrition. S. E. Carlson et al. DHA supplementation and pregnancy outcomes. American Journal of Clinical Nutrition. April 2013, in press. doi: 10.3945/ajcn.11... |
Anthony Stocks, chairman and professor of anthropology at Idaho State University, responds: "The evolution of smiles is opaque and, as with many evolutionary accounts of social behavior, fraught with just-soism. Among human babies, however, the 'tooth-baring' smile is associated less with friendship than with fright--w... |
a non-toothy, not-so-broad-but-open-lipped smile is associated with pleasure in human infants. Somehow we seem to have taken the fright-threat sort of smile and extended it to strangers as a presumably friendly smile. Maybe it is not as innocent as it seems. "All cultures recognize a variety of mouth gestures as indexe... |
however, smiles come in many varieties, not all of them interpreted as friendly." Frank McAndrew, professor of psychology at Knox College in Galesburg, Ill., has done extensive research on facial expressions. He answers as follows: "Baring one's teeth is not always a threat. In primates, showing the teeth, especially t... |
human smile probably has evolved from that. "In the primate threat, the lips are curled back and the teeth are apart--you are ready to bite. But if the teeth are pressed together and the lips are relaxed, then clearly you are not prepared to do any damage. These displays are combined with other facial features, such as... |
with your eyes, to express a whole range of feelings. In a lot of human smiling, it is something you do in public, but it does not reflect true 'friendly' feelings--think of politicians smiling for photographers. "What is especially interesting is that you do not have to learn to do any of this--it is preprogrammed beh... |
blind never see anybody smile, but they show the same kinds of smiles under the same situations as sighted people." McAndrew suggests several books that will be of interest to readers seeking more information on this topic: 'Non-Verbal Communication.' Edited by R. A. Hinde. Cambridge University Press, 1972. 'Emotion: A... |
More 60-Second Science Plants can pull carbon dioxide, the planet-warming greenhouse gas, out of Earth’s atmosphere. But these aren’t the only living organisms that affect carbon dioxide levels, and thus global warming. Nope, I’m not talking about humans. Humble sea |
otters can also reduce greenhouse gases, by indirectly helping kelp plants. That finding is in the journal Frontiers in Ecology and the Environment. [Christopher C Wilmer et al., Do trophic cascades affect the storage and flux of atmospheric carbon? An |
analysis of sea otters and kelp forests] Researchers used 40 years of data to look at the effect of sea otter populations on kelp. Depending on the plant density, one square meter of kelp forest can absorb anywhere from tens |
to hundreds of grams of carbon per year. But when sea otters are around, kelp density is high and the plants can suck up more than 12 times as much carbon. That’s because otters nosh on kelp-eating sea urchins. In |
the mammals’ presence, the urchins hide away and feed on kelp detritus rather than living, carbon-absorbing plants. So climate researchers need to note that the herbivores that eat plants, and the predators that eat them, also have roles to play |
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