Rising sun shines through tunnel for Brunel's birthday

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Rising sun shines through tunnel for Brunel's birthday

Postby johnthefireman » Mon Apr 10, 2017 10:59 pm

Light at the end of the tunnel: sun shines for Brunel's birthday

Rail staff confirm legend that rising sun shines through Box tunnel in Bath on birthday of Isambard Kingdom Brunel
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Re: Rising sun shines through tunnel for Brunel's birthday

Postby philipmartin » Tue Apr 11, 2017 5:07 am

Whe I saw the reference to the rising sun, I thought that we were in Japan again. https://www.youtube.com/watch?v=QOEhviiX3vA


http://youtu.be/vpzwzQfUegk


http://youtu.be/GykzgCsynrc



The last video doesn't have anything to do with Box Tunnel, but is an interesting Eurostar presentation.
http://youtu.be/VP0OZdz-0IY


Here's an excerpt from the Wiki Box Tunnel article, which treats the rising sun phenomenon, (if indeed it does rise every day as has been alleged here.)

"Brunel's birthday[edit]
It was first reported in 1842[6] that twice a year the sun shines through the tunnel. At some point it has been assumed that Brunel deliberately aligned the tunnel so that the rising sun is visible through it on his birthday each year, April 9. This is not the case. Actual dates on which the sun has been seen to be visible from the western portal are 5 April 1992 and 5 September 1985 (the time approximately 06:34 on both occasions).
Angus Buchanan (2002, p. 269) writes:
"The alignment of the Box Tunnel has been the subject of serious discussion in the New Civil Engineer and elsewhere. I am grateful to my friend James Richard for making calculations which convinced me that the alignment on 9 April would permit the sun to be visible through the tunnel soon after dawn on a fine day.
"On the other hand, it has been asserted that it is impossible to guarantee the effect on a particular calendar day, because the angle at which the sun rises on a given date varies slightly with the cycle of leap years.[7][page needed] However, the sun subtends an angle of about half a degree, which is more than the year-to-year variation and more than the field of view through the tunnel, so it quite possibly seems to fill the tunnel every year. It is also asserted that Brunel failed to account for atmospheric refraction, and the effect is visible a few days too early.[8]
"Buchanan (p. 226) concludes:
…I have found no documentary evidence for the often-repeated story that Brunel aligned the Box Tunnel so that the rising sun shone through it on his birthday, even though careful examination shows that it could indeed do so, and it is certainly a good story.
" A mathematical exploration of the possibility of the phenomenon occurring on Brunel's birthday has been undertaken by C.P. Atkins.[9] Atkins concludes that, taking atmospheric refraction into account:
…full illumination [of the tunnel profile] can occur on April 7 in three (non-Leap) years out of four, whereas in a Leap-Year this should occur on April 6. …partial illumination is not possible on April 8, let alone the significant April 9.
The author suggests that reports of the sun shining through Box Tunnel on April 9, or even on April 15 and 16, as reported by "the local head ganger … suggests some reflection effect and is, in itself, worthy of further investigation".

"The sun rises in alignment to the entrance to Box Tunnel, Bath, UK on 9 April, 2017
On Sunday April 9th 2017 with fine weather and the railway closed for electrification work and station upgrades at Bath Spa a team from the GWR franchise tested the theory, finding that the sunrise did not shine fully through the tunnel, [10]. However images released at the time show that the sun is remarkably well aligned to the tunnel. [11]

Photo and caption from Wiki. "The sun rises in alignment to the entrance to Box Tunnel, Bath, UK on 9 April, 2017"
Attachments
GWR_BoxTunnel_05.jpg
Last edited by philipmartin on Tue Apr 11, 2017 11:31 am, edited 11 times in total.
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Re: Rising sun shines through tunnel for Brunel's birthday

Postby george matthews » Tue Apr 11, 2017 5:26 am

philipmartin wrote:Whe I saw the reference to the rising sun, I thought that we were in Japan again. https://www.youtube.com/watch?v=QOEhviiX3vA

The sun also rises here - every day, not just on Brunel's birthday.
Is it possible to check this story? I rather doubt that the tunnel alignment was deliberate, but research would have to look through Brunel's papers to see if there is any sign he regarded his birth date with importance. I suspect it was a pure accident.
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Re: Rising sun shines through tunnel for Brunel's birthday

Postby David Benton » Tue Apr 11, 2017 5:41 am

the sun would be at the same angle at the corresponding day in the Autumn. still the legend doesn't say it shines through only on his birthday. I would say engineers of the day were very aware of the angles of the sun, so it is entirely possible.
Most legends have some basis of fact behind them, usually exaggerated or twisted. Its certainly a nice to think it may be true.
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