Something just occurs to me. We often do stuff so that we could get some pleasure remembering it. We don’t have to do stuff that are too hard. Thats what makes us human. Thinking about it thats how we invented… Read More ›
To budding astronomers.
A difference between true velocity and proper velocity. Proper velocity (proper motion) is the motion of a star apparent to the center-of-mass of the solar system. That is, how fast any object (a star) is moving wrt the sun’s position. (in terms of its center-of-mass)
So if a star is close to sun, its true velocity might be as much as it is, but proper velocity can be larger. Proper velocities are often larger when stars are closer, an useful fact in Astronomy.
(How proper velocity is eg useful in Astronomy, should be a good essay type question in Indian University exams, in the course of astronomy, but rather its more useful to remove essay type questions from Exams of University and such essay should be written by students as blogs, and the best blogs can be rewarded, Change should be brought to our education system by innovative thinking and not just by lecturing on outdated spiritual discourses)
Take a chicken tikka stick. (you have seen them right? a few pieces of raw chicken is pierced into a stick)
Now ask yourself the question. How to get it minimally and maximally heated up by the fire from sun. If its minimally heated its winter and if its maximally heated its summer.
Now there are 3 primary parameters that influence the situation. One is called distance from the oven that sun is. Two any change that can be made to this distance is governed by two parameter. one when along a particular direction when we look at the oven how far it is? That distance can be changed a lot due to relative motion of earth and sun. Lets say therefore we will hold the chicken stick quite straight so it goes as straight as we stand on a given location on earth. Thats called a perpendicular in some poor mathematicians dictionary.
Yes it is indeed winter but you wouldn’t know until the sun sets when suddenly there is a cool feeling. The day weather is still not very cool. The abrasiveness is caused by the direct glares and flares from sun which are instantly cut off when sun sets and the equilibrium conditions are felt. Plus remember that the seasons are not due to the distance of earth from sun, between maximum and minimum, the earth varies its distance only by 3.4%. The season are due to what are called the “obliquity of ecliptic” that is; The inclination of earth in its Orbital Plane of sun (maxm; 23.44 degree).
During a variation of inclination of earth the sun also changes its relative distance from above a point on earth, causing what we call as season. In scientific terms we say seasons are effected due to equinoxes and sub-solar points or solstices. All together there are 4 of these points for a place on earth per year. SO any point on earth will have 2 equinoxes and 2 solstices.