Talk by Jaydeep Mukherjee on Space-Time Telescopes

Note: I wrote this on my earlier blog hosted as I recovered the text from the WayBack Machine. This post appeared on December 09, 2010 as per the time stamp. I’m trying to collect here again all my old writings spread on various blogs.

Last week, it was my friend Srinivas who informed me that Jaydeep Mukherjee would be delivering a talk at Nehru Planetarium. I had missed his talk the last time although I had the chance to meet him at his home. The talk was held today at Nehru Centre. During his talk, Jaydeep dealt with some basic astrophysics, Einstein’s concept of Space-Time and about some of the current and future NASA-funded telescopes.

After a brief introduction by Planetarium Directior Piyush Pandey on the Astronomy Lecture Series and Dr. Jaydeep Mukherjee, the talk began in earnest. He began with the Big Bang and corrected that the Big Bang was not really an explosion, a common misconception created by the terminology used. He stressed on the point again and again throughout his talk and also in the Question and Answer session. He talks about the first light from 400,000 years after the Big Bang when the stars first began to appear and right upto the present epoch. He uses images from Hubble to demonstrate that we look back into time using a telescope and so really these are time machines.

He began the description of telescopes with the famous Hubble Space Telescope went on to the SWIFT telescope and WMAP. He then stayed a bit on Chandra X-Ray Telescope (perhaps because it was its 10th anniversary and Chandrasekhar’s birth centenary). He explained using two examples of a supernova remanant and a galaxy about how Chandra turned our understanding of the hidden mechanisms in these. For the supernova remnant, he selected the famous Crab Nebula which was seen as a supernovae in 1054 AD. His slide mentioned that the supernovae was seen by Chinese and European astronomers. Wikipedia says Arab instead of Europeans. He showed how observations from Chandra helped in understanding the remnant’s structure. For the galaxy, he took a recent example of a galactic cannibalism and explained how Chandra added another dimension to the picture and revealed the inner structure.

He then moved on to the James Webb Space Telescope, the Hubble-successor as it is famously known as. He explained how the funding scenario in the United States of America meant that the Telescope would be further delayed than the 2014 year he mentioned on his slide. He also explained why there could be cost overruns in the mission. His analogy involved the house redecoration and how a new item found during the process could add to the cost as the process evolved.

He then moved to space time and gave us a simplistic idea of what Space-Time was. He then followed it up with the Gravity Probe B mission. The mission wanted to try and test Einstein’s explanation of curving of space-time curve as gravity. They did this with very highly precise gyroscopes (which Jaydeep stressed took about 40 years in development) that tested narrow changes in angular position. This change in position would not be seen if we accept Newton’s concept of gravity. But, changing angles showed that Einstein’s explanation of gravity was correct. I have over-simplified it here for brevity. If you are curious, you can find out about this here.

He then introduced us to a second mission, LISA. The idea behind LISA is to check for gravitational waves. To shorten, Jaydeep’s slide which compared electromagnetic and gravitational waves, gravitational waves move masses and electromagnetic waves move charges. LISA hopes to detect this movement in masses. This effect is so small that there needs to be three spacecrafts spaced a 5 million kms from each other in a triangular formation if there is to be hope of detecting these waves. In the Question and Answer session, Jaydeep agreed that this area was also small but was defined by modern technological capabilities rather than anything else.

I enjoyed his talk thoroughly. In the Question and Answer session, a little girl on the same row as me asked an intelligent question: “How do you know that the light from the Sun travels to Earth in (approximately) 8 minutes and not in 6 or 7 minutes?” This question set a rather high bar of expectations for questions but I believe was not met by the adult members in the audience including me. Jaydeep had bought goodies from NASA (brochures on Chandra and what I think is a sort of NASA flag) which were for people who asked questions but the writer of this blog got one for just being there.

The evening ended while we were expecting the news of the launch of SpaceX’s Falcon launch vehicle. I boarded the bus when the Abort was called and the Falcon lifted off when I got off the bus!

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