Facebook Twitter

This undated image provided by the journal Science a picokeystone, extracted from an aerogel tile from the Stardust interstellar dust collector. Scientists said seven microscopic particles collected by NASA's comet-chasing spacecraft, Stardust, appear to. Espace Toutes les photos de l'espace, frontière de l'infini.

This undated image provided by the journal Science a picokeystone, extracted from an aerogel tile from the Stardust interstellar dust collector. Scientists said seven microscopic particles collected by NASA's comet-chasing spacecraft, Stardust, appear to

Vista galleria:Espace 1 - 16 di 30. Special relativity. Special relativity implies a wide range of consequences, which have been experimentally verified,[2] including length contraction, time dilation, relativistic mass, mass–energy equivalence, a universal speed limit, and relativity of simultaneity.

Special relativity

It has replaced the conventional notion of an absolute universal time with the notion of a time that is dependent on reference frame and spatial position. Rather than an invariant time interval between two events, there is an invariant spacetime interval. Relativistic Doppler effect. Diagram 1.

Relativistic Doppler effect

A source of light waves moving to the right, relative to observers, with velocity 0.7c. The frequency is higher for observers on the right, and lower for observers on the left. The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity. Maxwell's equations. Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits.

Maxwell's equations

These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents. Kennedy–Thorndike experiment. Figure 1.

Kennedy–Thorndike experiment

The Kennedy–Thorndike experiment Improved variants of the Kennedy–Thorndike experiment have been conducted using optical cavities or Lunar Laser Ranging. Ives–Stilwell experiment. Ives–Stilwell experiment (1938).

Ives–Stilwell experiment

"Canal rays" (a mixture of mostly H2+ and H3+ ions) were accelerated through perforated plates charged from 6,788 to 18,350 volts. The beam and its reflected image were simultaneously observed with the aid of a concave mirror offset 7° from the beam.[1] (The offset in this illustration is exaggerated.) The Ives–Stilwell experiment tested the contribution of relativistic time dilation to the Doppler shift of light.[1][2] The result was in agreement with the formula for the transverse Doppler effect, and was the first direct, quantitative confirmation of the time dilation factor.

Since then, many Ives–Stilwell type experiments have been performed with increased precision. Together with the Michelson–Morley and Kennedy–Thorndike experiments, it forms one of the fundamental tests of special relativity theory.[3] Other tests confirming the relativistic Doppler effect, are the Mössbauer rotor experiment and modern Ives–Stilwell experiments. Michelson–Morley experiment. Figure 1.

Michelson–Morley experiment

Michelson and Morley's interferometric setup, mounted on a stone slab and floating in a pool of mercury. The Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University in Cleveland, Ohio.[1] It attempted to detect the relative motion of matter through the stationary luminiferous aether ("aether wind"). The negative results are generally considered to be the first strong evidence against the then prevalent aether theory, and initiated a line of research that eventually led to special relativity, in which the stationary aether concept has no role.

[A 1] The experiment has been referred to as "the moving-off point for the theoretical aspects of the Second Scientific Revolution". [A 2] Cahier physique - physics workbook. PART I click here (from Copernicus to Newton) movie to watch: greatest discoveries in Astronomy from discovery channel (42 minutes)Willam Herschel He gave up music for astronomy.

cahier physique - physics workbook

Time dilation of moving particles. Relation between the Lorentz factor γ and the time dilation of moving clocks.

Time dilation of moving particles

Time dilation of moving particles as predicted by special relativity can be measured in particle lifetime experiments. According to special relativity, the rate of clock C traveling between two synchronized laboratory clocks A and B is slowed with respect to the laboratory clock rates. This effect is called time dilation. Since any periodic process can be considered a clock, also the lifetimes of unstable particles such as muons must be affected, so that moving muons should have a longer lifetime than resting ones.

Variations of experiments that actually confirmed this effect took place in the atmosphere or in particle accelerators. Biologist warn of early stages of Earth's sixth mass extinction event -- ScienceDaily. The planet's current biodiversity, the product of 3.5 billion years of evolutionary trial and error, is the highest in the history of life.

Biologist warn of early stages of Earth's sixth mass extinction event -- ScienceDaily

But it may be reaching a tipping point. In a new review of scientific literature and analysis of data published in Science, an international team of scientists cautions that the loss and decline of animals is contributing to what appears to be the early days of the planet's sixth mass biological extinction event. Lists of unsolved problems. Why Probability in Quantum Mechanics is Given by the Wave Function Squared. One of the most profound and mysterious principles in all of physics is the Born Rule, named after Max Born. In quantum mechanics, particles don’t have classical properties like “position” or “momentum”; rather, there is a wave function that assigns a (complex) number, called the “amplitude,” to each possible measurement outcome. The Born Rule is then very simple: it says that the probability of obtaining any possible measurement outcome is equal to the square of the corresponding amplitude.

(The wave function is just the set of all the amplitudes.) Library - Google Search. History of writing. The history of writing is primarily the development of expressing language by letters or other marks[1] and also the study and description of these developments. In the history of how systems of representation of language through graphic means have evolved in different human civilizations, more complete writing systems were preceded by proto-writing, systems of ideographic and/or early mnemonic symbols.

True writing, in which the content of a linguistic utterance is encoded so that another reader can reconstruct, with a fair degree of accuracy, the exact utterance written down[A 1] is a later development. It is distinguished from proto-writing which typically avoids encoding grammatical words and affixes, making it more difficult or impossible to reconstruct the exact meaning intended by the writer unless a great deal of context is already known in advance.

Why study things? - An introduction to material culture. Why study things? Or put another way, what can we learn from objects that we can’t find out from the reading of texts? There’s no simple answer to these questions but, as we shall discover in the course of this unit, there’s no getting around the ubiquity of things. This unit is an adapted extract from the Open University course Making sense of things: an introduction to material culture (A151)23 [Tip: hold Ctrl and click a link to open it in a new tab. Oulipo. Oulipo (French pronunciation: ​[ulipo], short for French: Ouvroir de littérature potentielle; roughly translated: "workshop of potential literature") is a loose gathering of (mainly) French-speaking writers and mathematicians which seeks to create works using constrained writing techniques. It was founded in 1960 by Raymond Queneau and François Le Lionnais. Other notable members have included novelists Georges Perec and Italo Calvino, poets Oskar Pastior, Jean Lescure and poet/mathematician Jacques Roubaud.


How Your Brain Can Control Time | Memory, Emotions, & Decisions. If Buonomano turns out to be right, he will have explained only our fastest time telling, because after half a second, the brain’s ripples dissipate. On the scale of seconds to hours, the brain must use some other strategy. Warren Meck of Duke University argues that the brain measures long stretches of time by producing pulses.

But the brain does not then count the pulses in the way a clock does. Instead, Meck suspects, it does something more elegant. It listens to the pulses as if they were music. Optische Täuschungen - SPIEGEL ONLINE - Nachrichten. Panspermia. Near-Earth object. Humanzee. Pleiades. Schiefer. Erinyen. Proper motion. Universal Time. List of common misconceptions. William James Sidis. Seclusion. Ancient astronauts. Out-of-place artifact.