Luca Turin

What is important about all this is that the social behaviour of atoms – the branch of science known as chemistry -depends largely on how many atoms there are in the outer orbit. It is as if atoms are more comfortable with filled orbits, and are constantly searching for partners to swap electrons and achieve peace. For example, if one atom has seven electrons in its outer circle, it behaves like a collector trying to fill that yawning gap on its shelf and snaps up any electron around.

Alex Vilenkin

The fireball then continues to expand by inertia, but now it consists of normal matter, its gravity is attractive, and the expansion gradually slows down. The decay of the antigravity material marks the end of inflation and plays the role of the big bang in this theory.
The beauty of the idea was that in a single shot inflation explained why the universe is so big, why it is expanding, and why it was so hot at the beginning. A huge expanding universe was produced from almost nothing. All that was needed was a microscopic chunk of repulsive gravity material. Guth admitted he did not know where the initial chunk came from, but that detail could be worked out later. "It's often said that you cannot get something for nothing," he said, "but the universe may be the ultimate free lunch."

S. Braun, P. Ronzheimer, M. Schreiber, S. S. Hodgman, T. Rom, I. Bloch, U. Schneider

In cold regions on earth, negative temperatures on the Fahrenheit or Celsius scale can often occur in winter; in physics, however, they were so far impossible. On the absolute temperature scale that is used by physicists and also called Kelvin scale, one cannot go below zero – at least not in the sense of getting colder than zero Kelvin. According to the physical meaning of temperature, the temperature of a gas is determined by the chaotic movement of its particles – the colder the gas, the slower the particles. At zero Kelvin (-460°F or -273°C) the particles stop moving and all disorder disappears. Thus, nothing can be colder than absolute zero on the Kelvin scale. Physicists of the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics in Garching have now created an atomic gas in the lab that has nonetheless negative Kelvin values. These negative absolute temperatures lead to several striking consequences: Although the atoms in the gas attract each other and give rise to a negative pressure, the gas does not collapse – a behavior that is also postulated for dark energy in cosmology. Also supposedly impossible heat engines can be realized with the help of negative absolute temperatures, such as an engine with a thermodynamic efficiency above 100%.

Wikipedia

Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modelling them as vibrations of tiny supersymmetric strings.
General relativity typically deals with situations involving large mass objects in fairly large regions of spacetime whereas quantum mechanics is generally reserved for scenarios at the atomic scale (small spacetime regions). The two are very rarely used together, and the most common case in which they are combined is in the study of black holes. Having “peak density”, or the maximum amount of matter possible in a space, and very small area, the two must be used in synchrony in order to predict conditions in such places; yet, when used together, the equations fall apart, spitting out impossible answers, such as imaginary distances and less than one dimension.
The major problem with their congruence is that, at Planck scale (a fundamental small unit of length) lengths, general relativity predicts a smooth, flowing surface, while quantum mechanics predicts a random, warped surface, neither of which are anywhere near compatible. Superstring theory resolves this issue, replacing the classical idea of point particles with loops. These loops have an average diameter of the Planck length (about 10−33 cm), with extremely small variances, which completely ignores the quantum mechanical predictions of Planck-scale length dimensional warping.
Singularities are avoided because the observed consequences of “Big Crunches” never reach zero size. In fact, should the universe begin a “big crunch” sort of process, string theory dictates that the universe could never be smaller than the size of a string, at which point it would actually begin expanding.

吉野輝雄

昭和62年に当時の建設省に山崎川が「ふるさとの川モデル河川」に指定された。それを受け、中流域の護岸の修理・橋のかけなおしとともに、住民と山崎川の距離を縮めるために川と川全体が整備しなおされている。鯉を放流し、川の片方の道を遊歩道にし、公園の前に階段を設け川に降りられるようにした。これらの工事のために、桜の木を切り工事が終わるとそこに若い木を植えている。護岸の表面をコンクリートから岩にかえ一般的な都市河川よりも自然の川らしく化粧直しした。しかしながら、このような変身は自然のようにみえて全く自然から程遠いものになっていることを意味している。人間が計画してそのとおりになることを義務づけられた川は本当に自然の川になれるだろうか。

安田喜憲

日本列島の植生の変遷

Susan L. Woodward

Biomes are the major regional groupings of plants and animals discernible at a global scale. Their distribution patterns are strongly correlated with regional climate patterns and identified according to the climax vegetation type. However, a biome is composed not only of the climax vegetation, but also of associated successional communities, persistent subclimax communities, fauna, and soils.
The biome concept embraces the idea of community, of interaction among vegetation, animal populations, and soil. A biome (also called a biotic area) may be defined as a major region of distinctive plant and animal groups well adapted to the physical environment of its distribution area.

Norbert Rosing

Mike Weasner, R-Laurraine Tutihasi

J. Bristol Foster

This table from Foster’s paper (Evolution of Mammals on Islands, Nature, April 1964) shows relative sizes of island-dwelling mammal species and subspecies as compared with their presumed mainland relatives.

National Geographic Education

Europeans visited and colonized remote islands beginning in the 1500s. They sometimes caused harm. For example, they brought devastating diseases unknown to islanders, who had no resistance to them. Many island people perished from diseases such as measles.
On their ships, Europeans also brought animals—including cats, dogs, rats, snakes, and goats. These invasive species preyed on native island plants and animals. They also took over native species’ niches and destroyed the natural ecological balance of the islands.
Since the days of the early explorers, islands have been important as places for ships to take on supplies and for their crews to rest. Later, islands became part of ocean trade routes, linking distant parts of the world. Islands became particularly important to seafaring thieves known as pirates.
Like stepping stones, islands have helped people migrate over vast expanses of ocean from one continent to another.
Today, millions of people live on islands all over the world. Some even own them—islands are available for purchase just like any other piece of real estate.

Central Park Conservancy

Plantsurfer

Mimulus flower photographed in visible light (left) and ultraviolet light (right) showing a nectar guide visible to bees but not to humans.
Under ultraviolet, the flowers have a darker center, where the nectaries are located, and often specific patterns upon the petals as well.

Reuters

Italian white truffles

i. Bologna, Via Nicola Sardi, 4 - 14030 Rocchetta Tanaro (Asti), Italia

Bill Ingalls

Tengyo Kura

週末を森の中で過ごした。一緒にいたラトビア人の女の子が、夜、森の中で地面を探り探り、色んなものを見つけて見せてくれた。風と、木々の揺れる音だけが響く中、「森の中には自然界の本当に美しいものがたくさんある。でもそれは待っててもだめ、こうして自分で見つけなくちゃね」と言ってくれた。

(素敵なエピソードですね。ノルウェーの森、ラトビアの森、どこか違いますか？)
ノルウェーでトナカイが食べる苔を探したけど、こっちでは見つからなかった。。でも、もしかしたら生えてる森もあるかもしれません。きっと生きている森はどこも暖かくて厳しくて、冷たくて恐いところかもしれません。

David K. Lync, Bernard H. Soffer

The solar spectrum peaks in the green part of the spectrum, right? Wrong! It only peaks in the green when plotted in wavelength units. It peaks in the nearinfrared when plotted in frequency units.
Many people believe that the solar spectrum and the color sensitivity of the eye both peak at around 0.5 μm (500 nm) in the green. The notion is sometimes stated even more strongly, i.e., that evolution has produced a human eye whose color sensitivity has been optimized to match the solar emission spectrum. But this apparent wavelength coincidence between the solar spectrum and the eyes’ sensitivity is an artifact resulting from the units in which the solar spectrum is plotted. Comparing irradiance to sensitivity is like comparing apples to oranges: they are fundamentally different quantities and their shapes and peaks should not be likened to one another although they can legitimately be multiplied together.

Michael Schirber

The sky is blue — physicists tell us — because blue light in the sun’s rays bends more than red light. But this extra bending, or scattering, applies just as much to violet light, so it is reasonable to ask why the sky isn’t purple.
The answer, explained fully for the first time in a new scientific paper, is in the eye of the beholder.
“The traditional way that people teach this subject is that sunlight is scattered — more so for shorter wavelengths than for longer ones,” says Glenn Smith, an engineering professor at Georgia Tech. “The other half of the explanation is usually left out: how your eye perceives this spectrum.”
While writing a physics textbook some years ago, Smith noticed that physiology usually gets short shrift, even though the spectrum of skylight — when analyzed — is about equal parts violet and blue.
Smith has written an article for the July issue of the American Journal of Physics that puts the physics of light together with the physiology of human vision.
“This is nothing that people who work with eyes haven’t known for a long time,” Smith told LiveScience. “I just had not seen it all in one place before.”
The physics behind seeing blue skies
The physical explanation for the blueness of the sky is attributed to the work of Lord Rayleigh in the 19th century.
As a common prism reveals, sunlight is made of all the colors of the rainbow. When light from the sun enters Earth’s atmosphere, it is scattered, or deflected, by molecules in the atmosphere — primarily nitrogen and oxygen.
Shorter wavelengths (blue and violet) are scattered more than longer wavelengths (red and yellow). So as we look in a direction of the sky away from the sun, we see those wavelengths that are bent the most.
The light of day is actually a complex spectrum of many different wavelengths, but it is dominated by light with wavelengths between 400 nanometers (violet) and 450 nanometers (blue). A nanometer is 1 billionth of a meter.
How the eye sees color
The human eye is sensitive to light between roughly 380 and 740 nanometers. On a typical retina, there are 10 million rods for sensing low light levels and 5 million cones for detecting color.
Each cone contains pigments that restrict the range of wavelengths that the cone responds to. There are three varieties of cones for long, medium and short wavelengths.
“You need all three of them to see color correctly,” Smith explained.
The peak response for the long cones is at 570 nanometers (yellow), medium at 543 nanometers (green), and short at 442 nanometers (between violet and blue). But the three cones are sensitive over broad, overlapping wavelength ranges, which means two different spectra can cause the same response in a set of various cones.
A good example of this is yellow. There is a certain narrow range of wavelengths that we might call “pure” yellow (or another for “pure” blue, and so on). However, the same set of cones that reacts to a light of pure yellow also responds to the superposition of pure red and pure green light.
The sky’s light plays tricks
Two spectra that have the same cone response are called metamers. Smith stressed that this only concerns the neural signal coming out of the eye — long before any processing by the brain.
“In previous research, people excised cones from the eyes of dead people and measured the response to different spectra,” he said.
The same “trick” that makes red and green turn into yellow is happening in the sky. But in this case, the sky’s combination of violet and blue elicits the same cone response as pure blue plus white light, which is an equal mixture of all the colors.
“Your eye can’t tell the difference between that complex spectrum and one that is a mixture of pure blue and white,” Smith said.
In other animals, the sky color is undoubtedly different. Outside of humans and some other primates, most animals have only two types of cones instead of three (dichromatic vs. trichromatic).
Honeybees and some birds see at ultraviolet wavelengths that are invisible to humans.

Prism

RGB (Blue) type of explanations and images
Rainbow (Violet) type of explanations and images

Ruth Netting

The light from the Sun looks white. But it is really made up of all the colors of the rainbow. All light travels in a straight line unless something gets in the way to: reflect it (like a mirror); bend it (like a prism); or scatter it (like molecules of the gases in the atmosphere).
Sunlight reaches Earth’s atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth’s atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.