I can’t remember where and I can’t give a cite, but I once read that the Great Pyramid of Khufu had a shaft aligned parallel to the celestial pole, and that from the bottom of this shaft one could see the North Star (Alpha Draconis in Khufu’s time) even in the daytime. From what I can remember of the passage, its gist was apparently that this was a legend from ancient times, and for whatever reason no recent visitors to the Pyramid had verified this.
Has anyone else heard of this?
Yep, I was told this as absolute fact as a child.
Snopes has addressed the matter. Bloody Aristotle again.
j
I can attest you can’t do it from a just-sunken 300m mineshaft…the sky is distinguished as a bright spot, not a black hole.
I’m pretty sure former Doper Bad Astronomer addressed this in his book…yep, ch. 11. There are maybe 5 or 6 objects you might be able to see this way, Polaris* isn’t* one of them, nor whatever was the Polestar when the Pyramids were built…
nm
I’ve seen Jupiter in daylight, so these 5 or 6 objects might be The Sun, The Moon, Venus, Jupiter, Mars? and…the ISS? Mercury is probably too close to the Sun to ever be seen in daytime, I think, despite being as bright as Mars (when Mars is at its brightest).
He excluded the sun. it was Sirius and, if being very generous, Canopus.
Ah yes. These were experimental results from 1946, I now see. Sirius could possibly be visible under these circumstances.
The ever reliable Grant Hutchison points out that the amount of scattering from the sky is also dependent on the distance of the scattering molecules from the eye; so if you were at the bottom of a well 40km deep, there would be little or no blue light scattered that would reach your eye.
Of course a 40km pit would be improbably deep- and the blue light from the stars would be scattered away as well, making them invisible anyway.
The question has already been answered, but I just wanted to point out that, although human eyes can’t see (almost all) stars during the daytime, this isn’t true of optical measuring devices. it’s possible to distinguish stars even through all the scattered sunlight that makes up our blue sky. This isn’t just a curiosity – you can use such stellar markers for daytime celestial navigation
[insert solar eclipse joke here]
Which it will be this summer. I’ve seen Venus, Jupiter, and Mars in the daylight (even if it was technically less than half an hour before sunset), and Mars should be easy peasy (even brighter than Jupiter which is also at opposition right now).
Well, there’d be 40km of air in a column above you, which would do some scattering, especially given how dense it’d be at the bottom, there - not that I think 40km would be very safe - you’d be dead from barotrauma or suchlike- just the basic atmospheric pressure equation gives me a pressure of 2975.7 kPa - or close to 30 times atmospheric pressure.
30 atmospheres shouldn’t kill you - it’s only the same as diving to about 1,000ft underwater, which is inside the scuba deep-diving record.
Although I suppose nitrogen narcosis would, if you didn’t have breathing equipment.
Oh, it’s not just the nitrogen that’ll kill ya. Those deep divers use hypoxic gas mixtures for a reason.
IIRC, there was no pole star at the time the pyramids was built. The celestial pole was midway between the stars that form the bottom of the Little Dipper.
Well, within a few degrees then. IIRC Polaris is about 1.5° from the pole.
Sent from my SM-G950U using Tapatalk
If you fall down a well you might see stars anywhere you look.
No, it was actually fairly far from the Little Dipper at that time. Here is a chart of the axial precession over time. The pyramids were mostly built between 3000 and 2000 BC. Thuban is the star that was quite close to the pole in 3000 BC, and it was close enough for that role for about 600 years on either side of that date.
Right now, about half that. It’s moving toward the pole, or rather the pole is moving toward it, but is almost at its closest approach. I’m not sure exactly when it’ll be closest, but it will be fairly shortly, as in the next 30 years or so.
The well/stars thing is featured in Haruki Murakami’s novel “The Wind-Up Bird Chronicle,” although the book is partly a sort of magical realism so maybe Murakami used the device while knowing it wasn’t true.
If someone built a 40 km tall chimney and you stood inside it looking up, you’d probably see a dark patch of night sky even in the daytime, because the vast majority of the air above your head would not be scattering daylight. If there happened to be a star passing directly overhead, you’d see it for the brief moment of time when the chimney was perfectly aligned with the star. How fast it would happen depends on the width of the chimney divided by its height. For a 40 km tall chimney with an inner diameter of 40 m, you’d see a patch of sky about .001 radians across, about 0.141 degrees. If you’re at 30 degrees latitude, stars overhead would cross that distance in about 39 seconds.
