Planets, orbits

Speculation about life on other planets probably began when humans discovered that the Earth Is not unique. We know that several other planets of the solar system bear at least some resemblance to our own. Why, then, should there not be life on Mars, or Venus, or perhaps on undiscovered Earthlike planets orbiting some other star ... 

Outside our own solar system, might there be planetary environments where life flourishes hi recent years, astronomers have discovered planets orbiting stars other than our own. Whether or not these planets support life is still impossible to say. Nevertheless, the more we discover about the variety of the universe, the more likely it becomes that we are not alone. 

Like Rutherford, he pictured the atom as a tiny nucleus with an electron moving around it like a planet orbiting the sun. Bohr,... 

The number of known extrasolar planets grows monthly the first discovery was made on October 1, 1995, by Michael Mayor and Didier Queloz from the University of Geneva, who found a planet orbiting around the sun-like star 51 Pegasus. 

Planets orbiting their own local star outside our solar system... 

Another well-defined configuration of the classical three body Coulomb problem with unambiguous quantum correspondence is the collinear antisymmetric stretch configuration, where the electrons are located on opposite sides of the nucleus. In contrast to the frozen planet orbit, the antisymmetric stretch is unstable in the axial direction (G.S. Ezra et.al., 1991 P. Schlagheck et.al., 2003), with the two electrons colliding with the nucleus in a perfectly alternating way (Fig. 3 (left)). Hence, already the one dimensional treatment accounts for the dominant classical decay channel of this configuration. As for the frozen planet, there are doubly excited states of helium associated to the periodic orbit of the ASC as illustrated in Fig. 3 (left). 

Our chemical experiences suggest that differential equations seem to be something stable, and by that we mean that, if there is a small change in one of the conditions, either initial concentrations or rate constants, we expect small changes in the outcomes as well. The classical example for a stable system is our solar system of planets orbiting the sun. Their trajectories are defined by their masses and initial location and velocity, all of which are the initial parameters of a relatively simple system of differential equations. As we all know, the system is very stable and we can predict the trajectories with an incredible precision, e.g. the eclipses and even the returns of comets. For a long time, humanity believed that the whole universe behaves in a similarly predictable way, of course much more complex but still essentially predictable. Descartes was the first to formally propose such a point of view. 

The detection of light from an extrasolar planet was reported by A. C. Cameron, K. Horne, A. Penny, and D. James, Probable Detection of Starlight Reflected from the Giant Planet Orbiting t Bootis , Nature, 402 (1999), 751. 

Bohr s planetary model of the atom, in which electrons orbit the nucleus much like planets orbit the sun, is a graphical representation that helps us understand how electrons can possess only certain quantities of energy. 

Was this youT answeT An orbit is a distinct path followed by an object in its revolution around another object. In Bohr s planetary model of the atom, he proposed an analogy between electrons orbiting the atomic nucleus and planets orbiting the sun. 

With the particlelike nature of energy and the wavelike nature of matter now established, let s return to the problem of atomic structure. Several models of atomic structure were proposed in the late nineteenth and early twentieth centuries. A model proposed in 1914 by the Danish physicist Niels Bohr (1885-1962), for example, described the hydrogen atom as a nucleus with an electron circling around it, much as a planet orbits the sun. Furthermore, said Bohr, only certain specific orbits corresponding to certain specific energy levels for the electron are available. The Bohr model was extremely important historically because of its conclusion that electrons have only specific energy levels available to them, but the model fails for atoms with more than one electron. 

Figure 3.2 In this Bohr model of a nitrogen atom, electrons orbit the nucleus much like planets orbit the Sun. The electrons are located in shells that increase in energy as their distance from the nucleus increases. In a nitrogen atom, there are two electrons in the first shell and five electrons in the second shell.

The nucleus of an atom contains the heavier subatomic particles - the protons and the neutrons. The electrons, the lightest of the sub atomic particles, move around the nucleus at great distances from the nucleus relative to their size. They move very fast in electron energy levels very much as the planets orbit the Sun. 

Bohr model, the energy levels are called orbits. The way electrons move along fixed orbits around the nucleus of an atom is similar to the way the planets orbit the Sun. This is the original, somewhat primitive model for the atom. The Bohr model works well for very simple atoms, but is no longer used in more complex chemistry. 

Figure 2.2 The Bohr atom was proposed by Niels Bohr. He believed that electrons moved around the nucleus similar to the way planets orbit the Sun.

It has been known since 1772 that the planets orbit the sun at non-random distances, specified, in astronomical units1, by the Titius-Bode law ... 

A specific wave function solution is called an orbital. The different orbitals define different energies and distributions for the different electrons. The name orbital goes back to earlier theories where the electron was thought to orbit the nucleus in the way that planets orbit the sun. It seems to apply more to an electron seen as a particle, and orbitals of electrons thought of as particles and wave functions of electrons thought of as waves are really two different ways of looking at the same thing. Each different orbital has its own individual quantum numbers, , , and mg. 

When Kepler began the major work for which he became known, the structure of the solar system was a hot topic of intellectual and emotional debate. In accord with Copernicus, Kepler believed that the planets revolved around the Sun—an unpopular opinion in 1600. The prevailing and orthodox view was that the motionless Earth occupied the privileged central position in the universe with the Sun and planets orbiting around it. 

In the sixteenth century, Copernicus proposed that the earth and planets orbited the Sun. At the time one of the arguments proposed against the Copemican view was that there should be a heliocentric parallax if the Sun was indeed the center of the solar system. At the time no such parallaxes had been observed. Copernicus countered rather simply by stating that the stars were much farther away than anyone had ever imagined, so the parallax was too small to observe. When astronomers finally managed to measure a parallax, it turned out that Copernicus was right. 

When the idea of atoms being made up of a positive nucleus surrounded by negative electrons was first put forward, the idea was that the electrons orbited the nucleus just as planets orbit the Sun. Just as the force of gravity keeps the planets in their orbits and keeps them from flying off into space, so the force of attraction between the positive nucleus and the negative electrons keeps them in their orbits. 

According to Rutherford s model of the atom, electrons orbit the nucleus just as planets orbit the sun. 

This question is obviously unanswerable in the present state of our knowledge. In any case, itis not for the biologist to answer. All that can be said is that the present direction of astronomical research favors multiplicity rather than uniqueness. It is already known that planetary systems are far from rare. It is true that only large planets orbiting close to their sun have been detected so far, but this is because of technical limitations that may well be overcome by the advances of tomorrow. The existence of earth-like planets is not excluded it is seen as likely by many experts. 

---