SEE THE BEAUTIFUL NATURE
Friday, March 25, 2011
Monday, March 21, 2011
Saturday, March 19, 2011
Galaxies Nature
“Most of the mass in galaxies does not exist in the form of stars but in a halo of dark matter (matter different from the hydrogen and heavier elements of which we and the stars are made). There is a substantial literature on the elegant idea that dark matter controls the size of the central black hole, but Kormendy and Bender show that this cannot be so. The nearby bulgeless spiral galaxy M101 (figure above) illustrates the situation: if M101 has a central black hole, its mass must be tiny relative to that of the black holes of other spirals with similar dark-matter haloes. There are roughly equal numbers of nearby large galaxies with and without bulges. For example, the galaxy next to ours, M31, has a prominent bulge and a black-hole mass close to 100 million solar masses, whereas our Galaxy, which has a similar dark-matter halo, is bulgeless, and the black-hole mass is only a few per cent of that in M31.
Friday, March 18, 2011
Stars Nature
Stars - An Overview
The Nature of Stars
Our Sun is an average star. Like all stars, it is a large sphere of gas held together by gravity. Stars generate heat and light through nuclear fusion. This process combines hydrogen that was already present in the Universe at early times into helium. In more massive stars, further fusion reactions convert the helium into carbon, then oxygen, then silicon. Everything we see is made from the elements created in massive stars, including our own bodies. Stars are huge factories producing the materials that make up the Universe we see around us today.
Sizes of Stars
Our Sun is approximately 1.4 million km in diameter, but its size will change throughout its lifetime as it evolves. We can only compare stellar sizes at similar evolutionary stages.
White Dwarf stars can be one thousand times smaller than our Sun, whilst Red Giant stars can be over one hundred times larger. That means that stellar sizes cover a range of (approximately) 1,400 km to 1,400,000,000 km in diameter.
Thursday, March 17, 2011
Tuesday, March 15, 2011
Monday, March 14, 2011
Sunday, March 13, 2011
Tuesday, March 8, 2011
THE NATURE OF SPACE
THE PHYSICAL NATURE OF SPACE
Even at best it is a difficult task to convey a clear understanding of a basically new scientific concept. Regardless of how simple the concept itself may be, or how explicitly it may be set forth by its originator, the human mind is so constituted that it refuses to look at the new idea in the simple and direct light in which it is presented, and instead creates wholly unnecessary difficulties by insisting on placing the innovation within the context of previous thought, rather than viewing it in its own setting. As Freeman J. Dyson recently observed,
The reason why new concepts in any branch of science are hard to grasp is always the same; contemporary scientists try to picture the new concept in terms of ideas which existed before.
There is no easy way of overcoming this obstacle and creating a more favorable climate for unbiased consideration of the nature and merits of the innovation. About the most that one can do is to define the new concept clearly: to explain specifically just what it is, where it is introduced into the previously existing system of thought, how it differs from previous patterns of thinking, and above all, to make it clear that however strange this concept may seem to first acquaintance, it is nevertheless logical and rational. Before taking up any questions of detail, therefore, I want to make a few comments of this kind about the new ideas that I am introducing.
The basic innovation in my new theoretical system, the Reciprocal System, as I call it, is a new concept of the nature of space and time which has emerged from a long and intensive study of basic physical processes. In present-day thought, a location in space is generally conceived as an entity that can be described by means of Cartesian coordinates. Of course, we cannot see a location in space, but we can see an object which may occupy such a location and we apply the coordinates to the object. If this object remains in the same spatial location its coordinates, according to the usual concept of space, are considered to remain unchanged. It should be realized, however, that this generally accepted concept of spatial localization is not something that has been derived from physical observation or measurement; it is a geometrical concept—purely a human investigation—and there is no assurance that it has any physical meaning or that it corresponds to anything that exists in the physical universe.
For example, if a physical object existing in physical space has no independent motion of its own and must therefore remain stationary with respect to that physical space, we have no assurance whatever that its geometrical coordinates will remain constant. It is normally taken for granted that such will be the case, and it must be conceded that established habits of thought make it rather difficult to visualize anything different. Einstein, for instance, says that it took him seven years of study and reflection to see this matter in a clear light and to realize that a physical location might not necessarily be capable of representation by a fixed geometrical coordinate system. After coming to this realization, however, he recognized its importance and he eventually utilized it as the basis of his General Theory. In that theory the coordinate system of reference is just as impermanent and subject to modification as the measurements with respect to the reference system are in the Special Theory. As explained by Moller in his textbook on Relativity,
the spatial and temporal coordinates thus lose every physical significance; they simply represent a certain arbitrary, but unambiguous, numbering of the physical events.
Sunday, March 6, 2011
TRAVELING NATURE: MOON NATURE
TRAVELING NATURE: MOON NATURE: "MoonDespite centuries of study through increasingly powerful telescopes, the Moon really only began to reveal its secrets during the ..."
MOON NATURE
Moon
Despite centuries of study through increasingly powerful telescopes, the Moon really only began to reveal its secrets during the Apollo landings in the 1960s and 1970s.
Scientists studying rocks returned by theastronauts believe the Moon was formed about 4.6 billion years ago when a planet-sized object smashed into the early Earth and sprayed molten rock into orbit around the battered planet. It is thought these orbiting fragments slowly came together to form the Moon.
Photo: The Moon taken by the Apollo 17astronauts (NASA)
The Moon is Earth's only natural satellite[nb 4] and the fifth largest satellite in the Solar System. It is the largest natural satellite in the Solar System relative to the size of its primary (though Charon, which orbits dwarf planet Pluto, is proportionally larger), a quarter the diameter of Earth and 1/81 its mass. The Moon is the second densest satellite after Io. It is in synchronous rotation with Earth, always showing the same face; the near side is marked with dark volcanic maria among the bright ancient crustal highlands and prominent impact craters. It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a similar reflectance to coal. Its prominence in the sky and its regular cycle of phases have since ancient times made the Moon an important cultural influence on language, the calendar, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun, allowing it to cover the Sun nearly precisely in total solar eclipses.
The Moon is the only celestial body on which humans have landed. While the Soviet Union's Luna programme was the first to reach the Moon with unmanned spacecraft in 1959, the United States' NASA Apollo program achieved the only manned missions to date, beginning with the first manned lunar orbiting mission by Apollo 8 in 1968, and six manned lunar landings between 1969 and 1972—the first being Apollo 11 in 1969. These missions returned over 380 kg of lunar rocks, which have been used to develop a detailed geological understanding of the Moon's origins (it is thought to have formed some 4.5 billion years ago in a giant impact event involving Earth), the formation of its internal structure, and its subsequent history.
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