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Category Archives: Q&A

Questions and answers with students

What if? [Q&A]

I had previously mentioned a technique called order-of-magnitude estimation that scientists of all stripes find extraordinarily useful, and Atul of Canara College asked me what that meant. One of the most important characteristics of doing science is that scientists look to work on problems that can be solved. There is no point in wasting years […]

But what is the Universe expanding into? [Q&A]

It is probably the most common question astronomers encounter: “Fine, you say that the Universe is expanding. OK, I buy that. But what is it expanding into?” There is really no good way to answer this because the correct answer, that it is not expanding into anything, that there is no outside to the Universe, […]

10000 Hours

People sometimes ask me, why is doing a PhD considered so hard? Why does it take years? The first rule of success is that there is no short cut. As Malcolm Gladwell points out in Outliers, successful people got that way by really working their butts off. He suggests 10000 hours of work as the […]

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 […]

far sight [Q&A]

When it comes to telescopes, a question that astronomers get asked with some regularity is, how far does it see? Abraham Lincoln was once supposedly asked how long his legs were, to which he is said to have answered, “long enough to reach the ground.” Same here. How far can the Hubble see? Far enough […]

Greenhouse Effect [Q&A]

Sahiba, a middle-schooler from New Jersey, asks what is the greenhouse effect and how does it work? We hear a lot about the greenhouse effect nowadays because of the global climate change that is happening, and the tendency is for people to think that this is something new that humans are causing and must be […]

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 […]

Nearest Galaxy [Q&A]

We had a Science Day at Cambridge recently and the SAO ran an Open House where people could come and ask questions of astronomers. One question that came up repeatedly was, what is the galaxy that is nearest to us? It depends on how you define the term. If you are looking for a galaxy […]

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, […]

Dark Energy [Q&A]

Karthik asks, what is Dark Energy? To put it succinctly: I don’t know. At this point, it is just a name given to something that we don’t really understand. We know from looking at the brightness of Type Ia supernovae (which have very predictable intensities, so their apparent brightness is a good tracker of distance) […]