Can you see stars from the bottom of a well?

From the bottom of a 6-foot diameter well, at a depth of say 50 feet, the sky would subtend the same angle to the eye as a 1.5 inch diameter tube of length 1 foot held up to the eye. This is about the same size as the paper tube in American ' kitchen towel' paper. If you do this experiment in the daytime you will see that no stars come out by sighting through such a tube. So, by direct experiment with a similar geometry, the answer is no, you cannot see stars in the daytime at the bottom of a well.

As a caviat, Ken Tapping an astronomer at the NRC Herzberg Institute of Astrophysics notes: "If we were on the Moon's surface, where there is no atmosphere, we could simply shade out the Sun and the reflected glare from the ground and see the stars perfectly well. On the Earth, our atmosphere tends to scatter the sunlight, which is what makes the sky look blue. This blue is sufficiently bright that it is very difficult to see the stars through it, although on really clear days, in dark places such as the bottom of a well, where reflected light from things on the ground isn't reaching your eyes, it is sometimes possible to see a star or two."

Another answer, and far more complete, is given by David Hughes in the Quarterly Journal of the Royal Astron. Soc., 1983, vol. 24, pp 246-257.




Return to Ask the Astronomer