Solar System Studies & Exoplanets

• Do two planets collide each other ?
• How does the moon has an impact on the human brain ?
• Why do all planets, except pluto revolve around the sun in the same plane ?
• What are the constituents of the rings of Saturn ?
• Is there any possibility that a piece of rectangular cloth mounted on a staff flutters in outer space like it does on earth ? This question arises from the fact that certain conspiracy theorists have put up a website "NASA Mooned US" which states that the American landings on the moon were faked. The website shows a picture of an astronaut on the moon, standing next to the American flag, which appears to be fluttering. The fluttering of a flag in outer space seems highly improbable.
• It was a great curiosity when a magical view of the moon was seen. After shower, at Bhawanipatna, Orissa, the climate became cloudy and the moon was invisible. At around 9:00 PM, ring-shaped, yellowish bright cloud was noticed that covered the moon. When observed minutely, seven colours,like a rainbow, was seen beneath the bright cloud. But, the cloud disappeared soon. What could have happened in the sky, to produce these effects ?
• Why do planets revolve round the sun in an elliptical orbit and not in a circular orbit ? Why is the sun at the focus of an ellipse and not in the centre ?
• Can there be a stable revolving system with no mass at the centre like electron revolving in an atom without nucleus and earth revolving in the solar system without sun but any centre of gravity present at the sun's position. ?

Do two planets collide with each other ?(Saurabh Chakote)

It is very unlikely that two planets will collide with each other. The solar system has been around for five billion (500 crore) years and the planets long ago settled into a steady motion that is quite stable. Infact, a study of craters on the moon has shown that there are not even as many asteroid impacts as there used be.   Top

How does the moon has an impact on the human brain, if any ? (Saurabh Chakote)

The moon has no effect on human behaviour. There is no truth in the old sayings about people going mad because of the full moon nor do people turn into wolves. In general, anyone who says that celestial bodies have any influence on our lives, astrologers and their like are completely mistaken.   Top

Why do all planets other than pluto revolve around the sun in the same plane?
(Dimitra Atri)

In addition to all revolving in the same plane (ecliptic plane), almost all bodies in the solar system rotate in the same sense with the rotational plane close to the ecliptic plane. This is a general property of all such systems. This can be explained by postulating that the solar system evolved from a giant cloud. The sun condensed at the center while the planets were formed by random collisions at various distances from the sun. The up and down components of this motion tend to cancel leaving only that part which is in the plane of the rotation.   Top

What are the constituents of the rings of saturn ? (Rajesh)

The rings of saturn mainly are composed of small pieces of normal water ice. The size of particles vary from microns to several metres with a large number of them in centimetre range. Although they are broadly classified into A, B & C rings, each of these is a group of thousands of ringlets. If all the pieces are clumped together, they form a ball of size about 600 kms. Although, jupiter, uranus and neptune also have rings, the albedo of the particles of rings of saturn make them look bright. Thus they can be seen even through small telescopes.   Top

Is there any possibility that a piece of rectangular cloth mounted on a staff flutters in outer space like it does on earth ? This question arises from the fact that certain conspiracy theorists have put up a website "NASA Mooned US" which states that the American landings on the moon were faked. The website shows a picture of an astronaut on the moon, standing next to the American flag, which appears to be fluttering. The fluttering of a flag in outer space seems highly improbable. (Gopinath Subramanian)

Certainly, cloth in space will not flutter. However, I believe that the US flag on the moon was stiffened so that it would look like wind was blowing, I do not believe that there was ever a movie showing the flag really fluttering. Considering that there have been a total of 21 men on the moon and that there is a laser reflector which was set up on the moon which can be observed from the earth, I do not really understand why any one would doubt that men have landed on the moon.   Top

It was a great curiosity when a magical view of the moon was seen. After shower, at Bhawanipatna, Orissa, the climate became cloudy and the moon was invisible. At around 9:00 PM, ring-shaped, yellowish bright cloud was noticed that covered the moon. When observed minutely, seven colours, like a rainbow, was seen beneath the bright cloud. But, the cloud disappeared soon. What could have happened in the sky, to produce these effects ?

These are effects akin to the rainbow caused by clouds, which are thin enough to allow moon to be seen, thick enough to cause these colourful effects. These are called coronae, not to be mistaken for the corona of the sun seen during total solar eclipse. It is caused by the diffraction of light by the tiny drops of water. Diffraction is able to separate out the seven colours as well. Thus red colour is seen at the outer edge of the circle, while at the inner edge blue is seen. The size of the corona depends on the size of the cloud particles.   Top

Why do planets revolve round the sun in an elliptical orbit and not in a circular orbit ? Why is the sun at the focusof an ellipse and not in the centre ? (Nivedita)

The ellipticity of orbits is a consequence of Newton's famous inverse-square law of gravitiation, which states that the attractive force between two bodies is inversely proportional to the square of the distance between them and acts along the line joining the two bodies. The most general solution to the equations of motion of a body bound in a gravitational potential is an elliptical orbit, with the source (here: our Sun) at one of the two foci.

The trajectory of a free object that responds to the Sun's gravitation is hyperbolic. Bodies of lesser energy have decreasingly eccentric orbits. A body that is just free of the Sun's gravity has a parabolic orbit. At lesser energies, the bound orbit has elliptical shape. At the least possible energy at which a planet can orbit around the Sun, the orbit is circular. At lesser energies the orbiting body would spiral into the Sun!

The shape of an (elliptical) orbit can be characterized by the parameter called eccentricity, given by the ratio e = F/2a, where F = the distance between the two foci of the elliptical orbit and a = the ellipse's semi-major axis. For a circle, e = 0 and energy minimal.

Historically, Kepler (1571-1630) first observed that the orbits of planets around the Sun were elliptical, not circular, an observation now codified as Kepler's first law. Sir Isaac Newton (1643-1727) first explained Kepler's observations on planetary motion as a consequence of the gravitational force using the mathematical apparatus of calculus invented by him (and independently by Leibniz).

Can there be a stable revolving system with no mass at the centre like electron revolving in an atom without nucleus and earth revolving in the solar system without sun but any centre of gravity present at the sun's position.

There are two types of mass: gravitational (which produces gravitational attraction), and inertial (which determines how a body will respond to a force). According to Eintein's Equivalence Principle, these two masses are identical.

Therefore you cannot free a body from exerting gravitational attraction, without also depriving it of inertial mass. But without the latter,there's no way to tell how the body will respond to a force, and thus unnacceptable (to standard physics).

Hence, it is impossible to have an electron revolving around an inexistent nucleus, etc.   Top