We need to understand first that Force can be categorized into two types. One is called tangential or collinear force. This component of the force is always along the direction of motion and changes speed of an object. It can change direction once the velocity of the object has become zero. Its NOT centripetal force. It can never make an object go in a plane or 3 D trajectory, as the motion is limited to only one dimension. The object can only go back and forth.
Now look at the other component. Its called a radial force. Its always perpendicular to the direction of motion. This force is called centripetal force, always. Note that its different from what we call central forces.
In consequence, both tangential and radial forces can be central. More…
What happens when some UV falls on biological molecules? (or any kind) some of these molecules like the wooden pole absorb the energy and there still remains energy which they can emit as visible light. So the UV light kicks the molecules and the molecules in turn emit visible light. This implies that the UV wavelength that the molecules absorbed energy at are very small compared to the wavelength at which they emit visible light. This is always the case.
When we say some materials are fluorescent it means they absorbed higher energy and emitted lower energy radiations of colorful light.
But this has a great deal of application apart from its theoretical interest. More…
Define an Hour Circle.
Its a bit tricky to define some astronomical parameters and not run into innocent looking misrepresentations of facts. One needs to cool his amber more times than there are parameters, then one gets a feel where and how to begin and give a good description.
Hour Circle is a GREAT Circle, on a celestial sphere ** that, at the same time, passes through one of the celestial poles. Hence it passes through both of the celestial poles*.
A great circle is a circle that passes on a sphere, so that its radius (or diameter) equals to the radius (or diameter ) of that sphere.
If the great circle goes through one of the poles (– so both poles as an imminent condition of this definition) its also called a meridian and this circles’s angular reference wrt one of all possible meridians is called a longitude angle, or simply longitude. 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) More…
2. Last year in a text book in Indian High School curriculum, I spotted and corrected with my students, the following:
Myth; there are only 3 quarks that have been detected or FOUND/confirmed so far, in nature.
Its based on a knowledge that was true more than 3 decades ago. All quarks, 6 of them, have been confirmed as hypothesized, the last of them was confirmed 2 decades ago. So there is really no reason why these facts should have been omitted from the text books that are updated every few years as such. Who are our experts?
3. During my freelance research, I have pointed out the following fact within last 3 or 2 years. A recurring myth in very advance texts of physics, concurrently followed in major and wide number of universities around the world, some of the finest texts in the field of particle physics and widely believed to be excellent, which they are nonetheless.
Myth; (particle life time and range of forces) A (force carrier) particle is long range if its mass is zero. Lifetime is the uncertainty that gives rise to an energy which is equivalenced through Einstein’s mass-energy relation and mass being zero, we have an infinite range as range is inversely proportional.
Fact; This is murky waters. Its a manipulation of sorts. Experimentally life times are quite arbitrary, while mass is supposedly fixed. Neutrino has a mean-life from 15 seconds to 10 billion seconds in order of magnitude .. I have hypothesized that’s possible, because it has such a high energy, and given it can’t lose this energy via any possible processes, it must live that long. More…
Result; now that photons are mass-less, their energy, momentum, speed, etc are no more variables, in the sense of arbitrariness. They are constants, taking only a few values, but constant in a given situation. But other particles have these properties; arbitrary. So electrons energy and momentum are not fixed, but arbitrary.
But as long as we are considering only elementary particles (that is, we are in a Quantum Zone) eg, electrons, protons, photons, and not nutmegs, soccer balls and airplanes and satellites there is another quantity that is of important consequence that is constant. Spin; whether a mass-less particle or not, spin has the same magnitude for them. that is spin is same for photon, its always 1. Spin for an electron is always 1/2. Spin for proton is always 1/2. Its for this reason photon is called a Boson**. Any thing with spin, 0, 1, 2, etc will be a Boson. Anything with spin 1/2, 3/2 etc will be called Fermion. More…