In an interview, a few candidates appeared for a software engineering position.
This girl had an impressive resume with decent education skills. She had mentioned astronomy as a hobby, which got attention.
Disclaimer—I have absolutely zero knowledge about Astronomy.
Me: Astronomy! Looks interesting. Can you approximately deduce the speed at which the Earth circles around the Sun?
She: Never done it before. Let me think.
After a while
She: We
know that lightrays take approximately 8 minutes to reach Earth from
the sun. Using this information, we can approximately calculate the
distance between the Earth and the sun.
Me: Okay?
She: The
speed of light is approximately 0.3M kms per second, that makes the
distance as 144M kms. Although the Earth revolves in an elliptical
orbit, however, for the sake of simplicity I will assume that Earth
revolves in a circle, hence the distance it covers in a year is 2[math]\pi[/math]r which is approx 904M kms.
Me: Okay
She: One year has 31M seconds so the speed is 904 [math]\div[/math] 31 = 29 kms/sec.
Me: Looks good enough. Let me Google the actual speed.
Wow! It is 30 kms / sec. Great!
She: With this information we can also find the radius, mass and density of the sun…..
Me: ok, ok, ok. Lets stop here and move to other questions
The
amazing part was that using the most elementary Physics and Mathematics
(8th Grade) she was able to deduce lot of things. This is a great
example of presence of mind.
She went ahead to become a great programmer and filed many patents.
Edit 1 - Adding accurate information [1] for the readers
It takes sunlight an average of 8 minutes and 20 seconds to travel from the Sun to the Earth
Speed of light c = 0.2997 M Km/sec
The
average distance between the Earth and the Sun is 149.60 million km,
and one complete orbit takes 365.242 days , during which time Earth has
traveled 940 million km.
Edit 2 - Lot
of readers have asked how we can calculate mass, radius and density of
the sun. Here are the initial thoughts, although an expert can be more
helpful.
Mass - Using law of universal gravitation [2] and centripetal force [3], we know the omega from above.
Radius - Using simple trigonometry [4]
Density - Mass / Volume
Footnotes
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