Question

(a) You are standing at a site in northern California, when you feel the first effects of a major earthquake that started somewhere in the Los Angeles area. Briefly describe your motion, and what kind of wave is responsible for it. What is the next motion you experience?

(b) Why is the Moon receding from the Earth?

(c) Why did Venus lose its water? Briefly explain the mechanism.

(d) An astronomer reports that a gas giant planet has been discovered around another star, and that its density is similar to that of our own Jupiter.   Explain two kinds of observations that must have been done in order for the astronomer to have come to this conclusion.

(e) Going up in the Earth’s troposphere the temperature decreases whereas in the stratosphere the temperature increases with altitude. Explain why in both cases.

6. What happens to the wind patterns of planets like the Earth as we speed up their rotation? Why?
7. Jupiter and Saturn both radiate significantly more power than they receive from the Sun. The explanations are different, but have one thing in common. Elaborate.

Planets can be discovered by microlensing events. In a lensing geometry, what is being “lensed”, and how does this occur. Draw a simple diagram.

(i) Consider two SuperEarth planets that are identical in every way except that Planet A’s atmosphere consists of pure molecular hydrogen, and Planet B’s of pure atomic hydrogen. What is the ratio of the atmospheric temperature gradient in planet A compared to planet B in their tropospheres?

(j) How are the semi-major axes of our giant planets changing over billions of years? Why?

(k) An icy body in an approximately circular orbit out at 47 AU from the Sun has a gravitational interaction with another object in its vicinity. As a consequence its velocity is greatly reduced and it falls in towards the Sun where it will in due course be seen as a comet. Estimate the time it takes to fall in and become a typical comet in the Kuiper Belt (hint: what is range of Kuiper Belt objects in solar sysem?).

Answer 1

(a) push and pull motion is experience first like compression and rarefraction. This is due to P type seismic waves. Next we may experience verticle and horizontal motion of Earth's surface which will be due to S type waves.

(b) The energy losses in tidal friction causes the moon to move away from Earth. The Tidal friction is required to maintain the bulge and it dissipates the energy between Earth and the Moon as heat. This causes the moon to recede.

(c) water's constituent atoms are lost to space.

This happens when the Electric field in the solar winds enter the atmosphere and energise the ions enough to escape in space. This mechanism has caused the loss of water on the planet.

(e) The source of radiations that causes the temperature to rise comes either from Earth or from sun. The gas particles absorb the radiation emitted by earth and as the gas is dense below, the radiations are absorbed and as temperature decreases as we go higher in troposphere. For statosphere the radiations are coming from sun and gas particles absorb the radiation causing rise in the temperature, at higher altitude more dense gases to absorb the sun's radiations and increase the temperature further.

(a) wind direction is usually almost parallel to isobars due to Earth's rotation. Because the Earth rotates on its axis, air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere, if the Earth spun faster, the winds would be deflected further eastward in northern hemisphere and further westwards in southern hemisphere.