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Young students are always attracted by the night sky. The fact that light from any object in the sky takes some finite time to reach us is very fascinating. While this confirms that no instantaneous communication is possible, it is also allowing us to see how things were looking in the past. Unlike other physics experiments, astronomical observations are restricted to very few basic measurements like flux, shape of objects, line and continuum spectrum, polarization and time-variability of all these quantities. We are still able to get lot more information from these basic set of observations, thanks to high precession measurements interpreted in the framework of some standard physical models (like using Newton’s law for measurements related to motion under gravity and Hubble expansion to measure distances to objects based on Doppler shifts, etc.). As our ability to compute physical quantities and measure them accurately increases, we are able to ask and answer more and more fundamental questions related to our universe.
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