Computer simulation of classical paths of electrons within a two-dimensional electron gas.¹ Transistors, the most common electronic devices, contain layered structures constraining the motion of electrons, so that they are free to move in the x-y plane but are completely confined in the z direction, forming a so-called two-dimensional electron gas (2DEG). The details of the electrons motion in a 2DEG flow were unknown until recently, when newly developed microscopy techniques made possible the observation of the actual electron paths. ²

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Instead of a smooth flow, unexpected chaotic channeling was observed, with continuous branching of classical paths reminiscent of familiar natural forms. It has been found through simulation that these patterns are not due to preferred-energy paths in the background, like for the path of a river on a valley, but to the cumulative chaotic effect of encountering random positive “bumps” in the atomic landscape.

1. Digital Artwork © Eric J. Heller, Resonance Fine Art [↩]
2. M. A.Topinka, B. J. LeRoy, R. M. Westervelt, S. E. J. Shaw, R. Fleischmann, E. J. Heller, K. D. Maranowski, A. C. Gossard, “Coherent Branched Flow in a Two-Dimensional Electron Gas“, Nature, 410, 183 (2001) [↩]

Optical microscope photographs of snow crystals.¹ Their characteristic 6-fold symmetry is related to the molecular structure of water, which stabilizes in hexagonal lattices at earth temperature and pressure.² Each crystal has about 10¹⁸ molecules of water, and its very specific shape is due to a complex dependence on temperature and humidity change, and to nonlinear diffusion leading to structural branching instabilities and dendritic patterns. Each snowflake registers a history of interactions with the environment, like “a hyeroglyph sent from the sky”.³

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1. © Kenneth G. Libbrecht (Caltech) [↩]
2. Water has several other possible solid phases, depending on pressure and temperature, with different crystal symmetry. Eg. ice-Ic forming at earth pressure and temperature lower than -80°C has cubic symmetry. [↩]
3. U. Nakaya, “Snow Crystals: Natural and Artificial”, Harvard University Press (1954) [↩]

Infrared-light composite filtered image of M104 Galaxy taken by Spitzer Space Telescope in june 2004. Galaxy M104 (”Sombrero galaxy”) is located in the Virgo cluster, at a distance of about 30 million light-years. Its giant ring of dust spans over 50000 light years. It is believed that a supermassive black hole of a billion solar masses is located at its center.

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1. © NASA/JPL-Caltech/R. Kennicutt (University of Arizona), and the SINGS Team [↩]

Three-dimensional map of the large-scale distribution of dark matter in the observable universe, from Hubble Space Telescope data (NASA, Jan 7, 2007). The map, determined by analysis of gravitational distortions of light coming from distant galaxies, reveals a network of filaments intersecting at the locations of normal matter in galaxy clusters. Clumping of dark matter appears more pronounced from right (distant regions in space and time) to left (nearest and recent regions).

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Dark matter is a theoretical form of matter currently observed only by its gravitational effects and representing in the standard cosmological model about 20% of the energy density of the universe. It was first postulated to explain some motions of galaxies and other cosmological data, and confirmed by gravitational lensing observations of the Bullet Cluster of galaxies in August 2006.

1. © NASA, ESA, R. Massey (Caltech) [↩]

Image of the Sun taken through the Earth, in “neutrino light”, at the Super-Kamiokande detector (Japan). The image has been obtained with a 503 days exposure, by registering neutrinos emitted from the solar core and detected in a 50 000-ton water pool located 1 km underground. At night, neutrinos were transparently traversing the whole earth before being registered in this image.

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A neutrino is an elementary matter particle of almost zero mass, only interacting through weak nuclear forces and gravity, leading to its unimpeded traveling through ordinary solid matter at almost the speed of light. During a rare interaction between a neutrino and an electron in the water, the electron is accelerated at a speed greater than the speed of light in water, producing a pulse of light -called Cherenkov radiation- similar to a supersonic boom. These pulses are detected by thousands of light amplifiers disposed everywhere on the pool surface.

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1. © R. Svoboda, K. Gordan [↩]
2. © Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo [↩]

The two “Antennae” spiral galaxies started colliding a few hundred million years ago (a short timescale compared to galaxies lifespans). During the collision, the stars pass right on by each other but, because of gravity, enormous tidal forces eject streams of stars on the sides, causing the two-tailed shape of the system. The gas clouds inside each galaxy also get compressed, giving birth to thousands of new stars clusters. The galaxies nuclei will ultimately merge into a single galaxy. A similar event will happen to our Milky Way galaxy, when it will collide with Andromeda in several billion years.

1. © NASA, Hubble Space Telescope, 2006 [↩]

View from Mars Victoria Crater taken by the Opportunity Rover (2006)¹. The sand is rich in reddish iron oxides, which are also suspended as dust in the CO₂ atmosphere, leading to pink-red light scattering. Water ice clouds move at ~10 meters per second and should lead to snowing in some areas.

1. Exaggerated color [↩]
2. © NASA [↩]

Discovery of the W particle at CERN proton-antiproton collider (1982)¹. The proton-antiproton collision creates a W particle which then decays into an high-energy electron, emitted at a wide angle from the beam (indicated by the arrow at the bottom-right) and an invisible neutrino whose presence is deduced by the missing energy of the electron.

1. C. Rubbia. Experimental observation of the intermediate vector bosons W⁺, W^- and Z⁰. Nobel lecture, 8 december 1984 [↩]
2. © CERN [↩]

Observation of the cosmic microwave background by COBE satellite (1990-1993).¹ The cosmic microwave background is a background light in the microwave spectrum (below the infrared), present across all the sky, which was emitted about 14 billion years ago when the universe first became transparent shortly after the big-bang. The irregularities show structure formation in the embryo universe.

1. Nobel Prize 2006 to John C Mather, George F Smoot [↩]
2. © NASA [↩]

Single neuron from the hippocampal region of the brain. Neuron body, axon, and dendritic tree are imaged by using the GFP gene, which express a fluorescent protein in the cell.

1. © Paul De Koninck, Université Laval, Canada [↩]