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Tag Archives: physics

carbon dating [Q&A]

A student from Bhandarkar’s College asks, what is radio-carbon dating? There is an isotope of Carbon, 14C, that is radioactive. Chemically, there is a certain probability that it is included in living tissue and the relative proportions are maintained during the life of the organism (be it plant or animal). After the organism dies, the […]

superluminal expansion [Q&A]

Atul of Canara College asks, is it true that the Universe is expanding at a speed greater than light speed? And if so, does that not conflict with Relativity? Yes, but no. And no. Yes, the Universe is expanding, but there is no single speed that characterizes that expansion. However, two objects separated by a […]

plasma rocket [Q&A]

A student from Bhandarkar’s College asks, what are plasma rockets? Sounds like something out of science fiction, but they are real. In 1998, NASA launched a technology proving mission called Deep Space 1 that was powered by ionized Xenon atoms. In a rocket, propulsion is provided by expelling mass at high momentum in one direction, […]

what do physicists do? [Q&A]

Atul, who wants to be a theoretical physicist, wants to know what exactly is it that they do? Do they sit and derive things all the time? Do they teach? How do they go about their work? Theorists, yes, in general sit behind their desk either with a pencil and paper, or in front of […]

the reach of black holes [Q&A]

Gautham of Poornaprajna College wonders what keeps black holes from disrupting the stability of the Universe and gobbling up everything? It is a misconception to think that black holes are somehow more “powerful” at gravitational attraction than other objects. Black holes have mass, and they continue to obey the inverse square law at large distances. […]

the 4th dimension [Q&A]

Gautham of Poornaprajna College asks, what is the definition of time in 4-dimensional space? Typically, when people speak of the 4th dimension, they are talking of a spatial dimension. Any point in the 3-D space we are used to can be represented by 3 coordinates, say (x,y,z), with unit vectors all perpendicular to each other. […]

the erstwhile solar neutrino problem [Q&A]

Yoshita of Poornaprajna College asks, what is the solar neutrino problem? A byproduct of the nuclear fusion reactions in the core of the Sun are neutrinos. Because neutrinos don’t react with much, they escape from the core as soon as they are formed. The number of neutrinos produced is a very sensitive indicator of the […]

Universal rotation [Q&A]

This question came from a group — why is it that everything we know of seems to rotate, is it because the Universe as a whole is rotating? Can we infer anything about the Universe’s rotation from the fact that everything seems to rotate? Not really. Suppose you begin with a Universe that is filled […]

Higher Education [Q&A]

Atul from Canara College asks what is the typical career path that will lead to a Ph.D. in Astronomy from an American, Canadian, or British University? I am not familiar with how the British system works, but in the USA (and to a large extent in Canada), you need to demonstrate an aptitude for the […]

lookback time [Q&A]

Rakshit of Vidyodaya Public School asks, is it true that the farther we see into space, we are seeing further back in time? Yes, because of the limit imposed by the speed of light. When we see something now, we see the photons that were emitted by the object and that took some time getting […]