Dark Energy (Wikipedia) Adding the cosmological constant to cosmology's standard FLRW metric leads to the Lambda-CDM model, which has been referred to as the "standard model" of cosmology because of its precise agreement with observations. Dark energy has been used as a crucial ingredient in a recent attempt to formulate a cyclic model for the universe.[8] Nature of dark energy[edit] Many things about the nature of dark energy remain matters of speculation. The evidence for dark energy is indirect but comes from three independent sources: Distance measurements and their relation to redshift, which suggest the universe has expanded more in the last half of its life.[9]The theoretical need for a type of additional energy that is not matter or dark matter to form our observationally flat universe (absence of any detectable global curvature).It can be inferred from measures of large scale wave-patterns of mass density in the universe. Effect of dark energy: a small constant negative pressure of vacuum[edit] .
MACS J0416.1-2403 From Wikipedia, the free encyclopedia Galaxy cluster in the constellation Eridanus MACS J0416.1-2403 or MACS0416 abbreviated, is a cluster of galaxies at a redshift of z=0.397 with a mass 160 trillion times the mass of the Sun inside 200 kpc (650 kly). Gallery[edit] MACS J0416.1-2403 contains a significant amount of dark matter, which leaves a detectable imprint in visible light by distorting the images of background galaxies.[11] Very massive cluster of galaxies, MACS0416.1-2403, located roughly 4 billion light-years away.[12] Galaxy cluster MACS J0416.1–2403 is one of six being studied by the Hubble Frontier Fields programme.[13] References[edit]
Bloxes: Modular Cardboard Adult-Sized Building Blocks Dynamic method From Wikipedia, the free encyclopedia The dynamic method is a procedure for the determination of the masses of asteroids. The procedure gets its name from its use of the Newtonian laws of the dynamics, or motion, of asteroids as they move around the Solar System. The procedure works by taking multiple position measurements to determine the gravitational deflection caused when two or more asteroids move past each other. Because the method relies on detecting the amount of gravitational deflection induced during an interaction, the procedure works best for objects which will produce a large deflection in their interactions with other objects. Mathematical analysis[edit] The simplest way to describe the deflection of the asteroids is in the case where one object is significantly more massive than the other. Here is the angle between the asymptotes of the hyperbolic orbit of the small object relative to the large one, and References[edit]
New transparent solar cells can be used on windows, smartphone screens (Science Alert) This new type of transparent solar cell can be used to cover windows, buildings or smartphone screens to produce solar energy. Named a transparent luminescent solar concentrator and developed by researchers in Michigan State University in the US, this material can be used to cover anything that has a flat, clear surface. Transparent solar cell technology has been attempted before, but the energy the cells produced was poor and the materials they were made out of were highly coloured. "No one wants to sit behind coloured glass,” said one of the researchers behind the technology, chemical engineer Richard Lunt, in a press release. "It makes for a very colourful environment, like working in a disco. We take an approach where we actually make the luminescent active layer itself transparent.” The new transparent solar cells are made from tiny organic molecules that absorb invisible wavelengths of sunlight such as ultraviolet and near infrared light.
Inflation (Wikipedia) Theory of rapid universe expansion In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe. Following the inflationary period, the universe continued to expand, but at a slower rate. The re-acceleration of this slowing expansion due to dark energy began after the universe was already over 7.7 billion years old (5.4 billion years ago).[1] Inflation theory was developed in the late 1970s and early 1980s, with notable contributions by several theoretical physicists, including Alexei Starobinsky at Landau Institute for Theoretical Physics, Alan Guth at Cornell University, and Andrei Linde at Lebedev Physical Institute. Cosmic inflation is the hypothesis that the very early universe expanded exponentially fast. Structure formation [edit] Magnetic-monopole problem While solving the monopole problem motivated the original hypothesis, not every cosmologist was impressed. Few inhomogeneities remain
Axion Hypothetical elementary particle An axion () is a hypothetical elementary particle originally postulated by the Peccei–Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics (QCD). If axions exist and have low mass within a specific range, they are of interest as a possible component of cold dark matter. History[edit] Strong CP problem[edit] Prediction[edit] Axion dark matter[edit] QCD effects produce an effective periodic potential in which the axion field moves. There are two distinct scenarios in which the axion field begins its evolution, depending on the following two conditions: Broadly speaking, one of the two possible scenarios outlined in the two following subsections occurs: Pre-inflationary scenario[edit] Post-inflationary scenario[edit] If at least one of the conditions (a) or (b) is violated, the axion field takes different values within patches that are initially out of causal contact, but that today populate the volume enclosed by our Hubble horizon.
How To Be A Little Gauss Return to my mathematics pages Go to my home page © Copyright 1997, Jim Loy [Imagine that you are in the audience at this lecture] There is a story about Carl Friedrich Gauss. Some people find that story hard to believe, even impossible. I think that you people can duplicate little Gauss's [2 feet tall] trick [doubt in the audience] . Nobody use your calculators, or even paper and pencil for a while. Here's the problem: We want to find X. What if we start at the other end: Do we get the same answer? That was your first hint, "Associative Law." Let's see, 100+99=199, +98=297, +. What if we add up the even numbers (that's 49 additions), then add up the odd numbers (that's 49 additions), and then add up the two totals? When we finally total them up, we get the same answer, right? How about: Does that help? [A couple people in the audience say that the columns all add up to 101] . [There is general agreement] . Right. How many 101s do we have? 50 x 101 [Some people say "5050"] . Addendum:
Dark flow A possible non-random component of the peculiar velocity of galaxy clusters In astrophysics, dark flow is a controversial hypothesis to explain certain non-random measurements of peculiar velocity of galaxy clusters. The actual measured velocity is the sum of the velocity predicted by Hubble's Law plus a possible small velocity flowing in a common direction. Very large scale correlated flow, called bulk flow is proposed in this model to be related to certain models of inflationary cosmology. The researchers had suggested that the motion may be a remnant of the influence of no-longer-visible regions of the universe prior to inflation. The results appeared in the October 20, 2008, issue of Astrophysical Journal Letters.[1][2][3][4] Location[edit] In a study from March 2010, Kashlinsky extended his work from 2008, by using the 5-year WMAP results rather than the 3-year results, and doubling the number of galaxy clusters observed from 700. Criticisms[edit] See also[edit] References[edit]
What’s New in 3D Printing? :: ChemViews Magazine 3D Printing is Coming to Our Lives! 3D printing is not a novelty, it is more than 20 years old. However, the first monograph on it has only just appeared [1]. I learned about it only recently, when this manufacturing technique made its way into chemistry [2,3]. Today, rapidly developing 3D printing offers numerous marketed applications. Figure 1. The article “Print me a Stradivarius” with a cover picture of a printed violin was published in The Economist two years ago [8, 9]. Figure 2. 3D-printed lampshade. © 3Dizingof.com (Designer: Dizingof) Contrary to “complex structures made in expensive and complex ways that come together in even more complex ways” [10], applying 3D printing consists of consecutive depositing of layers of an appropriate material and their subsequent fusion. Mary Gehl states that the 3D printing was patented in the late 1970s but no source has been given for this information [12]. The Process of 3D Printing and Its Advantages The advantages of 3D printing are:
Black Hole (Wikipedia) A black hole is defined as a region of spacetime from which gravity prevents anything, including light, from escaping.[1] The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole.[2] Around a black hole, there is a mathematically defined surface called an event horizon that marks the point of no return. The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics.[3][4] Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater. Objects whose gravity fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. History General relativity
Indirect detection of dark matter the lifetime of dark matter , as well as the annihilation rate. Dark matter interactions[edit] Indirect detection relies on the products of dark matter interactions. yrs) for large amounts of DM to be present today.[1] In fact, it seems that the abundance of DM has not changed significantly while the universe has been matter-dominated.[2] Using measurements of the CMB and other large scale structures, the lifetime of DM can be roughly constrained by s.[2] Thus, annihilating DM is the focus of most indirect searches. Annihilating dark matter[edit] An annihilation cross section on the order of is consistent with the measured cosmological density of DM.[2] Thus, the objects of indirect searches are the secondary products that are expected from the annihilation of two dark matter particles.[2] When observations of those secondary products reveal cross sections on the order of the expected for the cross section given above.[2] where Decaying dark matter[edit] , rather than keV and , with , where GeV).