# MIThenge

## Background

At two different times each year, the sun aligns with the Massachusetts Institute of Technology's (MIT) "Infinite Corridor," a hallway approximately 823 feet long. During these times, the sun can be seen down the entire length of the hallway.

I first became interested in this phenomenon after reading an article in Sky and Telescope magazine, ("Sun Worship in Cambridge," Nov. 2003) which contained a statement that Ken Olum had also predicted moon alignments with the Infinite Corridor, but "he wasn't telling". I couldn't stand not to know, so I repeated the calculations in my programming language Frink to predict both sun and moon crossings.

Since then, it has become apparent that the published azimuth of the corridor, used to make predictions, is not quite correct, and I have attempted to determine the actual azimuth of the corridor and provide more accurate predictions.

I believe that this is the only resource that makes sun and moon predictions, and that uses proper figures for the alignment of the corridor. I am always improving these predictions. If you observe, let me know!

## Sun Crossings

Below, I present sun predictions for 2007 and beyond, using the azimuth of 245.75 degrees as outlined above. I believe that these new figures are closer to being accurate. Note that the times stated are the best estimate for when the sun aligns with the center of the corridor.

The altitude and azimuth figures are for the center of the sun. The sun has a diameter of approximately 0.5 degrees, so it will extend approximately .25 degrees above and below this.

NOTE: You may want to re-run these calculations yourself, substituting up-to-date values of temperature and atmospheric pressure in the mithengecorridor.frink file for the specified dates. Atmospheric refraction has a significant effect on objects close to the horizon, and temperature and pressure affect this greatly. The values above are all corrected for atmospheric refraction, but the temperatures and pressures at which these were calculated may not match your day's weather!

### Sun Predictions

WARNING: This table uses the new azimuth figure of 245.75 degrees, based on several observations which contain a fair degree of uncertainty, but I believe these numbers are more accurate than the guess that the Infinite Corridor is parallel to the surveyed property line. Note that some newer photographs may give better azimuth predictions, but these predictions have proven to work for the sun and the moon. These predictions may be updated soon.

You may want to re-run these calculations yourself, or remind me to do it as we get very close to the dates below, substituting up-to-date values of temperature and atmospheric pressure in the mithengecorridor.frink file for the specified dates. Atmospheric refraction has a significant effect on objects close to the horizon, and temperature and pressure affect this greatly. The values above are all corrected for atmospheric refraction, but the temperatures and pressures at which these were calculated may not match your day's weather! Temperatures for the year 2014 on are predicted using average temperature readings for Cambridge at that time of day for that day of year, using a Fourier series curve match for historical temperatures in Cambridge. See the temperature calculations in the file cambridgetempFourier.frink.

DateJulian DayAltitude
(degrees)
Predicted
Temp (F)
January 2007
2007-01-28 04:51:42 PM EST2454129.4109034-0.0429Likely too low.
2007-01-29 04:50:44 PM EST2454130.41024220.2829
2007-01-30 04:49:45 PM EST2454131.40955960.6129Best day.
2007-01-31 04:48:45 PM EST2454132.40885620.9529Only bottom of sun may be visible at center crossing. More will be visible slightly later. View from left side of corridor.
November 2007
2007-11-10 04:18:54 PM EST2454415.38813491.0247Only bottom of sun may be visible at center crossing. More will be visible slightly later. View from left side of corridor.
2007-11-11 04:20:10 PM EST2454416.38901390.6846Best day.
2007-11-12 04:21:26 PM EST2454417.38989170.3546
2007-11-13 04:22:42 PM EST2454418.39076790.0346Probably too low. May be visible earlier.
January-February 2008
2008-01-28 04:51:55 PM EST2454494.4110566-0.1129Almost certainly too low.
2008-01-29 04:50:58 PM EST2454495.41040070.2029
2008-01-30 04:50:00 PM EST2454496.40972330.5329
2008-01-31 04:48:59 PM EST2454497.40902500.8629High crossing.
November 2008
2008-11-09 04:18:36 PM EST2454780.38792051.1147Only bottom of sun may be visible at center crossing. More will be visible slightly later. View from left side of corridor.
2008-11-10 04:19:52 PM EST2454781.38879980.7647
2008-11-11 04:21:08 PM EST2454782.38967790.4346
2008-11-12 04:22:23 PM EST2454783.39055450.1146
2008-11-13 04:23:39 PM EST2454784.3914291-0.2046Almost certainly too low.
January-February 2009
2009-01-27 04:51:26 PM EST2454859.41072-0.0929Almost certainly too low. [SVG]
2009-01-28 04:50:29 PM EST2454860.410070.2329Very low. May be visible earlier. [SVG]
2009-01-29 04:49:31 PM EST2454861.409400.5529Good altitude. [SVG]
2009-01-30 04:48:32 PM EST2454862.408710.8829Somewhat high. Will be visible slightly later. [SVG]
November 2009
2009-11-10 04:18:51 PM EST2455146.388100.9547Bottom half of sun visible at center crossing. [SVG]
2009-11-11 04:20:07 PM EST2455147.388980.6146Excellent altitude. [SVG]
2009-11-12 04:21:23 PM EST2455148.389850.2946Somewhat low. [SVG]
2009-11-13 04:22:38 PM EST2455149.39073-0.0346Almost certainly too low. [SVG]
January-February 2010
2010-01-27 04:51:38 PM EST2455224.41087-0.1629Almost certainly too low. [SVG]
2010-01-28 04:50:43 PM EST2455225.410220.1529Very low. May be visible slightly earlier. [SVG]
2010-01-29 04:49:45 PM EST2455226.409560.4729May disappear over horizon early. [SVG]
2010-01-30 04:48:46 PM EST2455227.408870.8029Good altitude. [SVG]
2010-01-31 04:47:45 PM EST2455228.408161.1529Very high. May be visible slightly later. [SVG]
November 2010
2010-11-10 04:18:33 PM EST2455511.387881.0447Very high. May be visible slightly later. [SVG]
2010-11-11 04:19:48 PM EST2455512.388760.6946Excellent altitude. [SVG]
2010-11-12 04:21:04 PM EST2455513.389640.3746Rather low. [SVG]
2010-11-13 04:22:20 PM EST2455514.390510.0546Very low. May be visible earlier from right-hand-side of corridor. [SVG]
2010-11-14 04:23:35 PM EST2455515.39138-0.2646Almost certainly too low. [SVG]
January 2011
2011-01-28 04:51:38 PM EST2455590.41086-0.0229 [SVG]
2011-01-29 04:50:41 PM EST2455591.410200.2929 [SVG]
2011-01-30 04:49:42 PM EST2455592.409520.6229 [SVG]
2011-01-31 04:48:41 PM EST2455593.408810.9629 [SVG]
November 2011
2011-11-10 04:18:56 PM EST2455876.388151.0247 [SVG]
2011-11-11 04:20:12 PM EST2455877.389030.6846 [SVG]
2011-11-12 04:21:27 PM EST2455878.389910.3546 [SVG]
2011-11-13 04:22:43 PM EST2455879.390780.0346 [SVG]
January 2012
2012-01-28 04:51:51 PM EST2455955.41101-0.0929 [SVG]
2012-01-29 04:50:54 PM EST2455956.410360.2229 [SVG]
2012-01-30 04:49:56 PM EST2455957.409680.5429 [SVG]
2012-01-31 04:48:55 PM EST2455958.408980.8829 [SVG]
November 2012
2012-11-09 04:18:37 PM EST2456241.387931.1047 [SVG]
2012-11-10 04:19:53 PM EST2456242.388810.7647 [SVG]
2012-11-11 04:21:09 PM EST2456243.389690.4346 [SVG]
2012-11-12 04:22:24 PM EST2456244.390570.1146 [SVG]
2012-11-13 04:23:40 PM EST2456245.39144-0.2046 [SVG]
January 2013
2013-01-27 04:52:04 PM EST2456320.41116-0.1729 [SVG]
2013-01-28 04:51:08 PM EST2456321.410510.1429 [SVG]
2013-01-29 04:50:10 PM EST2456322.409840.4629 [SVG]
2013-01-30 04:49:10 PM EST2456323.409150.8029 [SVG]
2013-01-31 04:48:08 PM EST2456324.408431.1529 [SVG]
November 2013
2013-11-10 04:19:34 PM EST2456607.388600.8447 [SVG]
2013-11-11 04:20:50 PM EST2456608.389470.5146 [SVG]
2013-11-12 04:22:06 PM EST2456609.390350.1846 [SVG]
2013-11-13 04:23:21 PM EST2456610.39122-0.1346 [SVG]
January 2014
2014-01-27 04:52:17 PM EST2456685.41131-0.2429 [SVG]
2014-01-28 04:51:21 PM EST2456686.410670.0729 [SVG]
2014-01-29 04:50:23 PM EST2456687.410000.3929 [SVG]
2014-01-30 04:49:24 PM EST2456688.409310.7229 [SVG]
2014-01-31 04:48:23 PM EST2456689.408601.0629 [SVG]
November 2014
2014-11-10 04:19:15 PM EST2456972.388380.9347 [SVG]
2014-11-11 04:20:31 PM EST2456973.389260.5946 [SVG]
2014-11-12 04:21:47 PM EST2456974.390130.2646 [SVG]
2014-11-13 04:23:03 PM EST2456975.39101-0.0546 [SVG]
January 2015
2015-01-28 04:51:35 PM EST2457051.41082-0.0129 [SVG]
2015-01-29 04:50:37 PM EST2457052.410160.3129 [SVG]
2015-01-30 04:49:38 PM EST2457053.409480.6429 [SVG]
2015-01-31 04:48:38 PM EST2457054.408770.9829 [SVG]
November 2015
2015-11-10 04:18:57 PM EST2457337.388161.0147 [SVG]
2015-11-11 04:20:13 PM EST2457338.389040.6746 [SVG]
2015-11-12 04:21:28 PM EST2457339.389920.3446 [SVG]
2015-11-13 04:22:44 PM EST2457340.390790.0246 [SVG]
January 2016
2016-01-28 04:51:48 PM EST2457416.41098-0.1040 [SVG]
2016-01-29 04:50:51 PM EST2457417.410320.2240 [SVG]
2016-01-30 04:49:53 PM EST2457418.409640.5539 [SVG]
2016-01-31 04:48:52 PM EST2457419.408950.8938 [SVG]
November 2016
2016-11-09 04:18:38 PM EST2457702.387951.1052 [SVG]
2016-11-10 04:19:54 PM EST2457703.388830.7551 [SVG]
2016-11-11 04:21:10 PM EST2457704.389700.4250 [SVG]
2016-11-12 04:22:26 PM EST2457705.390580.1048 [SVG]
2016-11-13 04:23:41 PM EST2457706.39145-0.2147 [SVG]
January 2017
2017-01-27 04:52:02 PM EST2457781.41114-0.1740 Note that an impossibly thin new moon crosses the corridor at 04:36:25 PM EST. [SVG]
2017-01-28 04:51:05 PM EST2457782.410480.1440 [SVG]
2017-01-29 04:50:07 PM EST2457783.409810.4640 [SVG]
2017-01-30 04:49:07 PM EST2457784.409120.8039 [SVG]
2017-01-31 04:48:05 PM EST2457785.408401.1538 [SVG]
November 2017
2017-11-10 04:19:36 PM EST2458068.388610.8352 [SVG]
2017-11-11 04:20:51 PM EST2458069.389490.4951 [SVG]
2017-11-12 04:22:07 PM EST2458070.390370.1750 [SVG]
2017-11-13 04:23:23 PM EST2458071.39124-0.1449 [SVG]
January 2018
2018-01-27 04:52:15 PM EST2458146.41129-0.2540Almost certainly too low. [SVG]
2018-01-28 04:51:19 PM EST2458147.410650.0640 [SVG]
2018-01-29 04:50:22 PM EST2458148.409980.3840 [SVG]
2018-01-30 04:49:22 PM EST2458149.409290.7239 [SVG]
2018-01-31 04:48:21 PM EST2458150.408581.0638 [SVG]
November 2018
2018-11-10 04:19:17 PM EST2458433.388400.9152 [SVG]
2018-11-11 04:20:33 PM EST2458434.389280.5751 [SVG]
2018-11-12 04:21:49 PM EST2458435.390150.2550 [SVG]
2018-11-13 04:23:04 PM EST2458436.39103-0.0649Very low. [SVG]
January 2019
2019-01-28 04:51:33 PM EST2458512.41081-0.0240Very low. [SVG]
2019-01-29 04:50:36 PM EST2458513.410140.3040 [SVG]
2019-01-30 04:49:37 PM EST2458514.409460.6339Probably the best day for observing. [SVG]
2019-01-31 04:48:36 PM EST2458515.408760.9838Probably the best day for photometric measurements of the sun's lower limb. Take good observations for me today, especially as the sun crosses the center of the corridor! [SVG]
November 2019
2019-11-10 04:18:59 PM EST2458798.388191.0052Probably the best day for photometric measurements of the sun's lower limb. Take good observations for me today, especially as the sun crosses the center of the corridor! [SVG]
2019-11-11 04:20:15 PM EST2458799.389070.6551Probably the best day for visual observation. [SVG]
2019-11-12 04:21:31 PM EST2458800.389940.3350 [SVG]
2019-11-13 04:22:46 PM EST2458801.390820.0148Very low. [SVG]
January 2020
2020-01-28 04:51:47 PM EST2458877.41097-0.0940Very low. [SVG]
2020-01-29 04:50:50 PM EST2458878.410310.2240Low. [SVG]
2020-01-30 04:49:52 PM EST2458879.409630.5539 [SVG]
2020-01-31 04:48:51 PM EST2458880.408930.8938 [SVG]
November 2020
2020-11-09 04:18:41 PM EST2459163.387971.0852 [SVG]
2020-11-10 04:19:56 PM EST2459164.388850.7451Probably the best day for visual observations. [SVG]
2020-11-11 04:21:12 PM EST2459165.389730.4050 [SVG]
2020-11-12 04:22:28 PM EST2459166.390610.0848Very low. [SVG]
2020-11-13 04:23:43 PM EST2459167.39148-0.2247certainly too low. [SVG]
January 2021
2021-01-27 04:52:01 PM EST2459242.41113-0.1740 [SVG]
2021-01-28 04:51:04 PM EST2459243.410470.1440 [SVG]
2021-01-29 04:50:06 PM EST2459244.409800.4740 [SVG]
2021-01-30 04:49:06 PM EST2459245.409110.8039 [SVG]
2021-01-31 04:48:04 PM EST2459246.408391.1638 [SVG]
November 2021
2021-11-09 04:18:22 PM EST2459528.387761.1652 [SVG]
2021-11-10 04:19:38 PM EST2459529.388640.8252 [SVG]
2021-11-11 04:20:54 PM EST2459530.389520.4851 [SVG]
2021-11-12 04:22:10 PM EST2459531.390400.1650 [SVG]
2021-11-13 04:23:25 PM EST2459532.39127-0.1549 [SVG]
January 2022
2022-01-27 04:52:14 PM EST2459607.41128-0.2540 [SVG]
2022-01-28 04:51:19 PM EST2459608.410640.0640 [SVG]
2022-01-29 04:50:21 PM EST2459609.409970.3940 [SVG]
2022-01-30 04:49:21 PM EST2459610.409280.7239 [SVG]
2022-01-31 04:48:20 PM EST2459611.408571.0738 [SVG]
November 2022
2022-11-10 04:19:20 PM EST2459894.388430.9052 [SVG]
2022-11-11 04:20:36 PM EST2459895.389310.5651 [SVG]
2022-11-12 04:21:52 PM EST2459896.390190.2350 [SVG]
2022-11-13 04:23:07 PM EST2459897.39106-0.0849 [SVG]
January 2023
2023-01-28 04:51:32 PM EST2459973.41080-0.0140 [SVG]
2023-01-29 04:50:35 PM EST2459974.410130.3140 [SVG]
2023-01-30 04:49:36 PM EST2459975.409450.6439 [SVG]
2023-01-31 04:48:35 PM EST2459976.408740.9838 [SVG]
November 2023
2023-11-10 04:19:02 PM EST2460259.388220.9852 [SVG]
2023-11-11 04:20:18 PM EST2460260.389100.6451 [SVG]
2023-11-12 04:21:33 PM EST2460261.389980.3150 [SVG]
2023-11-13 04:22:49 PM EST2460262.390850.0048 [SVG]
January 2024
2024-01-28 04:51:46 PM EST2460338.41095-0.0940 [SVG]
2024-01-29 04:50:49 PM EST2460339.410300.2340 [SVG]
2024-01-30 04:49:50 PM EST2460340.409620.5639 [SVG]
2024-01-31 04:48:50 PM EST2460341.408920.9038 [SVG]
November 2024
2024-11-09 04:18:43 PM EST2460624.388011.0752 [SVG]
2024-11-10 04:19:59 PM EST2460625.388890.7251 [SVG]
2024-11-11 04:21:15 PM EST2460626.389760.3950 [SVG]
2024-11-12 04:22:31 PM EST2460627.390640.0748 [SVG]
2024-11-13 04:23:46 PM EST2460628.39151-0.2447 [SVG]

## Moon Crossings

On August 27, 2007, using these predictions, a team successfully observed and photographed a moon alignment with the Infinite Corridor! We believe we were the first group to predict and observe a rare moon crossing! The moon was very reddish-orange and 98.5% illuminated at this time and the sky was dark (about 4:40 AM EDT). Even so, the moon was somewhat hard to see and would have been easy to miss (or not recognize!) by anyone not explicitly looking, leading us to believe that unintentional viewings of the moon are extremely rare and unlikely.

It was found that foliage also blocked the moon significantly. Lenny Foner noted, "I took some of my shots from the railing in Lobby 7 (yes, that far forward) and moving just a few inches in any given direction was enough to block/unblock the moon." Foliage is generally less of an issue during the winter sun crossings in November and January.

Lenny also noted that many of the people present "apparently...didn't even realize they were looking at the moon when they saw it, 'cause it was so red (and so broken-up by leaves)."

Below, I present moon predictions for several years, using the new azimuth figure. I believe that these new figures are closer to being accurate. Note that the times stated are the best estimate for when the moon aligns with the center of the corridor.

The altitude and azimuth figures are for the center of the moon. The moon has a diameter of approximately 0.5 degrees, so it will extend approximately .25 degrees above and below this.

NOTE: You may want to re-run these calculations yourself, or remind me to do it as we get very close to the dates below, substituting up-to-date values of temperature and atmospheric pressure in the mithengecorridor.frink file for the specified dates. Atmospheric refraction has a significant effect on objects close to the horizon, and temperature and pressure affect this greatly. The values above are all corrected for atmospheric refraction, but the temperatures and pressures at which these were calculated may not match your day's weather! Temperatures for the year 2014 on are predicted using average temperature readings for Cambridge at that time of day for that day of year, using a Fourier series curve match for historical temperatures in Cambridge. See the temperature calculations in the file cambridgetempFourier.frink.

For moon crossings, pay close attention to the time of day and the percent illumination of the moon! Crossings during a new moon will certainly not be visible. Crossings during daylight hours will be difficult to see. The background color of the corridor approximates the color of the sky at the time.

And please send me an e-mail if you observe, whether you see something or not!

### Moon Predictions

WARNING: This table uses the new azimuth figure of 245.75 degrees. based on several observations which contain a fair degree of uncertainty. Note that some newer photographs may give better azimuth predictions, but these predictions have proven to work for the sun and the moon. These predictions may be updated soon.

DateJulian DayAltitude
(degrees)
Percent
Illuminated
Predicted
Temp (F)
2004
2004-04-07 07:18:34 AM EDT2453102.97123130.8094.546
2004-04-14 02:09:01 PM EDT2453110.25626570.6822.948
2004-06-01 03:41:34 AM EDT2453157.82054090.8294.964
2004-07-05 08:41:32 AM EDT2453192.02884700.1986.673
2004-08-29 05:04:48 AM EDT2453246.87833760.4199.170
2004-11-18 10:41:13 PM EST2453328.65362880.0449.144
2005
2005-05-22 04:07:46 AM EDT2453512.83872740.5397.061
2005-05-29 11:05:43 AM EDT2453520.12897031.1059.963
2005-07-16 12:37:12 AM EDT2453567.6925011-0.2566.174
2005-12-26 12:31:10 PM EST2453731.22998271.0522.732
2006
2006-01-02 07:30:08 PM EST2453738.5209349-0.0611.830
2006-04-22 01:18:27 PM EDT2453848.22114830.3932.450
2006-07-13 07:53:08 AM EDT2453929.99523811.0592.374
2006-08-01 11:06:12 PM EDT2453949.62930730.4147.874
2006-09-06 04:16:52 AM EDT2453984.84505121.1596.968
2007
2007-01-12 11:08:39 AM EST2454113.17267381.1139.429High. (Was overcast this day.)
2007-07-03 08:12:13 AM EDT2454285.0084929-0.1190.572Almost certainly too low. [SVG]
2007-08-18 09:50:47 PM EDT2454331.57694410.1232.372Very low. May be visible earlier from further down the corridor. [SVG]
2007-08-27 04:40:50 AM EDT2454339.86169931.0598.570Rather high, but in dark hours. Nearly full moon. May be visible slightly later. Watch from left side of corridor, or further down corridor. Best prospect for 2007. [SVG]
2007-11-08 03:24:01 PM EST2454413.35001820.611.247Almost perfect new moon. Sun near moon. Likely impossible to see. [SVG]
2008
2008-01-29 09:55:32 AM EST2454495.12190290.6955.729Good altitude. Moon half full. Unfortunately in daylight hours. [SVG]
2008-03-24 07:30:26 AM EDT2454549.9794733-0.1993.041Almost certainly too low. [SVG]
2008-04-01 02:05:14 PM EDT2454558.25363570.1423.044Very low. Poor illumination. Daylight hours. [SVG]
2008-06-22 08:36:15 AM EDT2454640.02518270.3087.070Fairly low. Fairly full moon. In daylight hours. [SVG]
2008-09-03 08:33:24 PM EDT2454713.52320360.4718.469Good altitude. Poor illuminated fraction. Past nautical twilight, so dark enough. [SVG]
2008-09-12 03:09:57 AM EDT2454721.7985800-0.2589.766Almost certainly too low. [SVG]
2008-11-05 10:35:06 PM EST2454776.64937520.9149.948 Rather high. Half-full moon. In dark hours. Best prospect for 2008. [SVG]
2009
2009-04-18 12:39:50 PM EDT2454940.19432880.5539.549Good altitude. Not very full moon. Daylight hours. [SVG]
2009-07-01 12:38:55 AM EDT2455013.69369891.1567.772Very high. Reasonable fullness. Dark hours. May be visible from further down the corridor. [SVG]
2009-07-09 07:11:56 AM EDT2455021.96663160.6196.273Excellent altitude and illumination, but in daylight hours. Good daylight prospect. [SVG]
2009-08-24 09:19:29 PM EDT2455068.5552060-0.1726.271Almost certainly too low. [SVG]
2009-09-29 01:46:57 AM EDT2455103.74094190.5177.360Good altitude and pretty good illumination. Dark hours. Good prospect. [SVG]
2009-10-18 05:47:04 PM EDT2455123.4076870-0.210.753Certainly too low and perfect new moon. Don't bother. [SVG]
2009-12-19 07:14:57 PM EST2455185.51039050.2510.934Rather low and very poor illuminated fraction. [SVG]
2010
2010-01-08 11:21:26 AM EST2455205.18156-0.1437.130 [SVG]
2010-03-11 01:51:22 PM EST2455267.285680.2814.537 [SVG]
2010-05-25 03:06:06 AM EDT2455341.795911.3991.662 [SVG]
2010-06-01 09:19:32 AM EDT2455349.055240.0980.064 [SVG]
2010-07-26 05:51:00 AM EDT2455403.910421.3299.975 [SVG]
2010-08-14 09:45:11 PM EDT2455423.573051.2931.973 [SVG]
2010-08-22 03:54:13 AM EDT2455430.82932-0.2194.971 [SVG]
2010-10-08 06:11:40 PM EDT2455478.424781.382.157 [SVG]
2010-11-11 09:25:34 PM EST2455512.601090.1235.046 [SVG]
2010-12-02 01:40:17 PM EST2455533.277980.9810.939 [SVG]
2011
2011-01-05 05:52:52 PM EST2455567.453380.822.630 [SVG]
2011-02-22 08:17:03 AM EST2455615.053511.2976.033 [SVG]
2011-03-28 01:28:33 PM EDT2455649.228161.0828.542 [SVG]
2011-04-24 11:28:08 AM EDT2455676.14455-0.2454.951 [SVG]
2011-06-12 02:09:40 AM EDT2455724.756711.1083.767 [SVG]
2011-06-18 07:54:56 AM EDT2455730.996490.4091.869 [SVG]
2011-08-12 04:25:36 AM EDT2455785.851121.2297.873 [SVG]
2011-09-08 02:26:47 AM EDT2455812.76861-0.0484.167 [SVG]
2012
2012-01-22 04:21:34 PM EST2455949.389990.110.329 [SVG]
2012-02-13 09:28:51 AM EST2455971.103370.1662.631 [SVG]
2012-04-08 07:05:20 AM EDT2456025.96204-0.2295.946 [SVG]
2012-04-13 11:56:27 AM EDT2456031.164210.6447.847 [SVG]
2012-06-02 03:25:18 AM EDT2456080.80924-0.0293.164 [SVG]
2012-08-22 09:56:03 PM EDT2456162.580600.8633.271 [SVG]
2012-08-28 02:47:32 AM EDT2456167.78301-0.0187.370 [SVG]
2012-10-16 06:35:45 PM EDT2456217.441500.293.054 [SVG]
2012-11-17 08:22:34 PM EST2456249.557340.4923.345 [SVG]
2012-12-10 01:53:53 PM EST2456272.287420.639.736 [SVG]
2013
2013-01-11 04:44:56 PM EST2456304.406210.220.229 [SVG]
2013-02-03 10:31:19 AM EST2456327.146760.3449.430 [SVG]
2013-03-07 01:13:23 PM EST2456359.259300.9419.836 [SVG]
2013-04-03 12:11:56 PM EDT2456386.174950.1044.644 [SVG]
2013-04-26 06:00:15 AM EDT2456408.916851.2299.552 [SVG]
2013-05-28 08:48:51 AM EDT2456441.033931.1284.062 [SVG]
2013-06-20 02:22:28 AM EDT2456463.765611.3785.469 [SVG]
2013-07-22 05:12:44 AM EDT2456495.883840.9299.675 [SVG]
2013-08-13 11:00:59 PM EDT2456518.625691.0746.473 [SVG]
2013-10-07 07:50:01 PM EDT2456573.493080.2810.657 [SVG]
2013-10-11 11:39:06 PM EDT2456577.652160.7652.356 [SVG]
2013-11-07 08:36:58 PM EST2456604.56734-0.1326.048 [SVG]
2013-12-01 03:19:04 PM EST2456628.346580.082.040 [SVG]
2014
2014-01-01 05:04:57 PM EST2456659.42011-0.140.538 [SVG]
2014-01-25 11:42:28 AM EST2456683.196160.4834.431 [SVG]
2014-01-29 03:38:44 PM EST2456687.360241.341.936 [SVG]
2014-02-25 01:25:52 PM EST2456714.267970.0117.933 [SVG]
2014-03-21 09:27:58 AM EDT2456738.061100.1076.643 [SVG]
2014-04-17 07:19:18 AM EDT2456764.971740.9994.754 [SVG]
2014-04-21 11:05:30 AM EDT2456769.128831.1558.149 [SVG]
2014-05-18 09:03:05 AM EDT2456796.043810.1582.260 [SVG]
2014-06-11 03:50:14 AM EDT2456819.826560.6895.476 [SVG]
2014-07-12 05:32:44 AM EDT2456850.897740.1899.877 [SVG]
2014-08-05 12:17:51 AM EDT2456874.679070.9462.184 [SVG]
2014-09-01 11:08:25 PM EDT2456902.63085-0.2446.583 [SVG]
2014-09-05 01:55:45 AM EDT2456905.747060.4579.676 [SVG]
2014-09-28 09:02:10 PM EDT2456929.543180.5221.779 [SVG]
2014-10-01 11:48:56 PM EDT2456932.65899-0.2254.075 [SVG]
2014-10-25 06:55:28 PM EDT2456956.455201.314.659 [SVG]
2014-10-29 10:34:49 PM EDT2456960.607521.3938.866 [SVG]
2014-11-22 04:45:20 PM EST2456984.40649-0.120.346 [SVG]
2014-11-25 07:33:19 PM EST2456987.523140.4215.049 [SVG]
2014-12-19 02:27:32 PM EST2457011.310801.026.531 [SVG]
2015
2015-01-16 01:09:57 PM EST2457039.256920.0918.430 [SVG]
2015-01-19 04:02:05 PM EST2457042.376460.440.936 [SVG]
2015-02-12 10:54:17 AM EST2457066.162701.3945.031 [SVG]
2015-03-12 10:43:34 AM EDT2457094.113600.2161.942 [SVG]
2015-03-15 01:24:35 PM EDT2457097.225410.6928.940 [SVG]
2015-04-08 08:38:19 AM EDT2457121.026610.8285.045 [SVG]
2015-04-11 11:19:32 AM EDT2457124.138570.0255.843 [SVG]
2015-05-09 10:05:28 AM EDT2457152.087141.3670.356 [SVG]
2015-06-02 05:21:03 AM EDT2457175.889620.0899.873 [SVG]
2015-06-05 08:04:01 AM EDT2457179.002790.3890.568 [SVG]
2015-06-29 03:06:49 AM EDT2457202.796411.1390.880 [SVG]
2015-07-27 01:50:19 AM EDT2457230.743290.1779.082 [SVG]
2015-07-30 04:35:14 AM EDT2457233.857800.5798.276 [SVG]
2015-08-22 11:36:50 PM EDT2457257.650581.3053.585 [SVG]
2015-08-26 02:21:35 AM EDT2457260.76500-0.2483.578 [SVG]
2015-09-19 10:24:24 PM EDT2457285.600290.1837.278 [SVG]
2015-09-23 12:59:53 AM EDT2457288.708260.8269.374 [SVG]
2015-10-16 08:19:30 PM EDT2457312.513550.6914.566 [SVG]
2015-10-19 10:54:53 PM EDT2457315.621450.0742.366 [SVG]
2015-11-12 05:14:36 PM EST2457339.426811.281.552 [SVG]
2015-11-16 08:39:53 PM EST2457343.569371.2827.055 [SVG]
2015-12-10 04:02:56 PM EST2457367.377050.000.536 [SVG]
2015-12-13 06:39:22 PM EST2457370.485680.357.343 [SVG]
2016
2016-01-06 01:50:04 PM EST2457394.284770.9811.730 [SVG]
2016-02-03 12:32:15 PM EST2457422.230730.1426.030 [SVG]
2016-02-06 03:09:46 PM EST2457425.340120.574.235 [SVG]
2016-03-01 10:20:13 AM EST2457449.139041.0853.335 [SVG]
2016-03-04 12:57:25 PM EST2457452.24822-0.1923.134 [SVG]
2016-03-29 10:06:58 AM EDT2457477.08818-0.0570.044 [SVG]
2016-04-01 12:35:52 PM EDT2457480.191580.7239.245 [SVG]
2016-04-25 08:02:32 AM EDT2457504.001770.3190.352 [SVG]
2016-04-28 10:32:50 AM EDT2457507.10614-0.1165.952 [SVG]
2016-05-22 05:57:52 AM EDT2457530.915190.8399.666 [SVG]
2016-05-26 09:16:55 AM EDT2457535.053421.0079.761 [SVG]
2016-06-22 07:16:36 AM EDT2457561.969870.1295.773 [SVG]
2016-07-16 02:35:57 AM EDT2457585.774970.4686.383 [SVG]
2016-08-16 03:49:35 AM EDT2457616.826110.5094.873 [SVG]
2016-09-08 11:08:31 PM EDT2457640.630910.3746.681 [SVG]
2016-10-05 09:00:52 PM EDT2457667.542271.0521.574 [SVG]
2016-10-10 12:17:26 AM EDT2457671.678770.5960.169 [SVG]
2016-11-29 04:45:10 PM EST2457722.406370.100.341 [SVG]
2016-12-03 07:57:14 PM EST2457726.539750.7618.249 [SVG]
2016-12-26 02:38:32 PM EST2457749.318430.935.830 [SVG]
2016-12-30 05:57:31 PM EST2457753.45662-0.082.840 [SVG]
2017
2017-01-23 01:23:46 PM EST2457777.26651-0.1916.932 [SVG]
2017-01-27 04:36:25 PM EST2457781.400291.390.139Impossibly thin new moon, but the sun crosses the corridor at 04:52:02 PM EST. [SVG]
2017-02-19 11:13:10 AM EST2457804.175810.7242.035 [SVG]
2017-02-23 02:30:07 PM EST2457808.312590.338.738 [SVG]
2017-04-15 08:49:26 AM EDT2457859.034340.0383.851 [SVG]
2017-04-19 12:00:16 PM EDT2457863.166850.3047.747 [SVG]
2017-05-12 06:43:29 AM EDT2457885.946870.6497.763 [SVG]
2017-06-13 08:39:49 AM EDT2457918.027660.4986.167 [SVG]
2017-07-06 03:27:08 AM EDT2457940.81052-0.1192.580 [SVG]
2017-08-02 01:19:26 AM EDT2457967.721840.8773.884 [SVG]
2017-08-07 05:18:39 AM EDT2457972.887961.3099.973 [SVG]
2017-09-03 03:15:04 AM EDT2457999.802140.2190.874 [SVG]
2017-09-25 09:55:00 PM EDT2458022.579870.2431.378 [SVG]
2017-10-22 07:45:20 PM EDT2458049.489821.139.864 [SVG]
2017-10-27 11:46:20 PM EDT2458054.657180.1852.365 [SVG]
2017-12-16 03:27:22 PM EST2458104.352340.212.032 [SVG]
2017-12-21 07:24:04 PM EST2458109.516720.4012.044 [SVG]
2018
2018-01-12 01:21:15 PM EST2458131.264761.2716.033 [SVG]
2018-02-14 04:01:35 PM EST2458164.376101.321.042 [SVG]
2018-03-08 09:59:50 AM EST2458186.124890.4758.240 [SVG]
2018-03-13 02:59:40 PM EDT2458191.291440.1213.542 [SVG]
2018-05-07 11:32:42 AM EDT2458246.147710.0854.451 [SVG]
2018-05-29 05:24:08 AM EDT2458267.891760.6999.868 [SVG]
2018-07-01 08:09:02 AM EDT2458301.006280.4790.671 [SVG]
2018-08-19 12:02:21 AM EDT2458349.668310.7458.584 [SVG]
2018-09-21 02:46:13 AM EDT2458382.782100.3086.669 [SVG]
2018-10-12 08:37:33 PM EDT2458404.52608-0.2216.970 [SVG]
2018-11-08 05:21:37 PM EST2458431.431681.281.955 [SVG]
2018-11-14 10:19:39 PM EST2458437.638650.3645.656 [SVG]
2019
2019-01-02 02:02:36 PM EST2458486.293470.3710.129 [SVG]
2019-01-08 06:53:28 PM EST2458492.495470.847.645 [SVG]
2019-03-25 09:35:32 AM EDT2458568.066350.2675.445 [SVG]
2019-03-31 02:31:06 PM EDT2458574.271600.6018.544 [SVG]
2019-05-25 11:04:55 AM EDT2458629.128420.8360.159 [SVG]
2019-08-09 12:39:06 AM EDT2458704.69383-0.1765.683 [SVG]
2019-08-15 05:38:18 AM EDT2458710.901610.2299.973 [SVG]
2019-09-04 10:29:12 PM EDT2458731.603621.1139.283 [SVG]
2019-10-09 02:15:17 AM EDT2458765.760621.3681.864 [SVG]
2019-10-29 06:59:07 PM EDT2458786.457720.314.561 [SVG]
2019-12-23 02:28:24 PM EST2458841.311390.016.830 [SVG]
2019-12-29 07:47:43 PM EST2458847.53314-0.0914.441 [SVG]
2020
2020-02-22 04:19:16 PM EST2458902.388390.930.645 [SVG]
2020-05-14 11:59:14 AM EDT2458984.166140.3249.354 [SVG]
2020-07-08 08:28:18 AM EDT2459039.019660.8588.171 [SVG]
2020-07-29 12:53:40 AM EDT2459059.703940.0668.884 [SVG]
2020-09-28 03:02:20 AM EDT2459120.793290.3088.270 [SVG]
2020-10-18 07:23:32 PM EDT2459141.474680.007.062 [SVG]
2020-12-12 02:42:07 PM EST2459196.320920.365.033 [SVG]
2021
2021-02-11 05:03:04 PM EST2459257.41880-0.230.243 [SVG]
2021-03-04 09:17:31 AM EST2459278.095510.0866.635 [SVG]
2021-04-07 02:38:35 PM EDT2459312.276801.1517.546 [SVG]
2021-06-28 09:12:59 AM EDT2459394.050680.2581.969 [SVG]
2021-08-22 05:38:02 AM EDT2459448.901420.7899.872 [SVG]
2021-10-08 07:34:40 PM EDT2459496.482410.688.868 [SVG]
2021-11-11 11:16:44 PM EST2459530.678290.3357.158 [SVG]
2021-12-02 02:55:23 PM EST2459551.330130.903.438 [SVG]
2022
2022-01-26 11:27:00 AM EST2459606.185420.0737.730 [SVG]
2022-05-22 11:46:24 AM EDT2459722.157221.2151.559 [SVG]
2022-09-01 09:53:58 PM EDT2459824.57915-0.1531.983 [SVG]
2022-10-06 02:38:04 AM EDT2459858.77644-0.1884.367 [SVG]
2022-11-22 03:18:31 PM EST2459906.346190.761.741 [SVG]
2022-12-26 08:14:27 PM EST2459940.55171-0.1018.744 [SVG]
2023
2023-01-16 11:43:22 AM EST2459961.196790.4333.430 [SVG]
2023-02-19 04:35:15 PM EST2459995.39949-0.240.445 [SVG]
2023-04-08 07:22:35 AM EDT2460042.97402-0.2394.447 [SVG]
2023-04-15 02:03:44 PM EDT2460050.252600.3824.049 [SVG]
2023-07-06 08:39:21 AM EDT2460132.027330.6986.671 [SVG]
2023-08-22 10:15:53 PM EDT2460179.59437-0.1736.686 [SVG]
2023-08-30 05:02:08 AM EDT2460186.876480.7899.173 [SVG]
2023-10-24 01:29:11 AM EDT2460241.728611.3473.260 [SVG]
2024
2024-02-02 10:07:50 AM EST2460343.130441.2553.529 [SVG]
2024-03-08 03:25:17 PM EST2460378.350901.433.746 [SVG]
2024-04-24 05:45:54 AM EDT2460424.906880.9699.855 [SVG]
2024-05-29 10:56:00 AM EDT2460460.122230.3562.561 [SVG]
2024-09-07 08:50:39 PM EDT2460561.53517-0.0320.682 [SVG]
2024-11-28 02:27:36 PM EST2460643.310840.055.835 [SVG]

## Error Analysis and Surveying

The exact orientation of the Infinite Corridor is uncertain. Previous best estimates of its azimuth made the assumption that the Infinite Corridor was constructed parallel to the surveyed property line, at 245.47391075 degrees. I have many reasons to believe that this azimuth is not quite correct. A small error has a large effect on sun and moon alignments. An error of even a fraction of a degree means that the sun or moon will not be visible at all on predicted dates.

I also believe that, after looking at the corridor, that low crossings will be obscured by intervening objects and daylight moon crossings will be very low-contrast and hard to see.

During my presentation, of Frink at MIT, I promised to survey the corridor to get a better estimate of its azimuth, to hopefully improve the accuracy of these predictions. With the help of another presenter, Matthias Hürlemann, I did some GPS measurements of the azimuth of the corridor. These measurements still had a large potential error, but based on some historical anomalous sightings of the sun, I believed they were closer than the previous estimates.

During the previous year and a half, I had analyzed all of the historical observations and photographs of sun crossings that I could find. The main anomaly was a sighting and photograph by Professor Paul Schechter on 1998-02-02. If the date of this photograph is correct, the sun would certainly not be visible on this date if the original surveyed azimuth was correct. I performed further calculations based on other observations, and predicted that the actual azimuth of the corridor was higher than the published figure. My prediction was then approximately 246.2 degrees. (Warning: Note that this is not the current-best figure!)

Note that the above differences in the azimuth of the corridor translate into an approximately 2-day difference in the sun predictions. These also translate into about a 0.77 degree difference in the altitude of the sun on any given day. Since the doorway is only about 0.91 degrees tall, or less, this changes the days that the sun will be visible.

Keith Winstein and Ken Olum have produced an excellent web page on MIThenge, including a diagram indicating the impossibility of the anomalous 1998 photograph. (Link opens in new window.) The chart at the bottom of the page shows that the sun would never be visible if the original azimuth of the corridor was correct. However, those pages have not been updated for a long time, and use an incorrect azimuth figure.

Below are some updated measurements of the corridor based on several observations. It is rather difficult to measure the azimuth of the corridor to the necessary precision.

Unfortunately, I live very far away from MIT (in Colorado,) so I don't have the ability to make more measurements easily. I have attempted to recruit technically-minded observers to help refine the true azimuth of the corridor.

Further visual observations by Ken Olum and Keith Winstein and have improved the azimuth figures for the corridor. It is almost certain that the original published figures are incorrect. Measurements taken by Ken Olum during the January 2005 crossing, and his subsequent returns to the Infinite Corridor to measure constrictions and variations in the shape of the hallway gave measurements of 245.89 degrees and 245.79 degrees respectively. Note that these are higher than the previously-used figure by about .3 or .4 degrees. This is enough to cause at least a 1-day error in visibility predictions for the sun, and making the moon not visible on predicted days.

Frink programs used to reverse-engineer Ken Olum's sun observations into azimuth numbers are found here: Observation 1 | Observation 2

Lenny Foner made a fantastic series of GPS-based measurements with extended baselines (as long as about 1700 meters!) in November and December, 2006. The best of these readings give an azimuth figure of approximately 245.737 degrees. Note, however, that GPS readings give an error circle of about 2 meters at best, which is still enough to generate significant difficulties in observation.

For these reasons, I am using an average of several observations, 245.75 degrees, in my predictions below. Note that the "Ideal Observations" section below has some likely-better azimuth figures that were not used to make the predictions below. These will be corrected soon.

## Ideal Observations

The "Holy Grail" of observations that would give the highest precision is a photograph showing the sun or moon's disc clearly from within the corridor, and as far back in the corridor as is possible. The window "gratings" on the Massachusetts Avenue end of the corridor should be visible. If we have accurate timings of these photographs and know the camera's position in relation to objects in the corridor, then the corridor's azimuth can be measured to high accuracy, given the known position of the sun or moon at that time. Note that only the azimuth of the photograph is useful; the altitude of the object is highly sensitive to atmospheric refraction, especially this close to the horizon, and the amount of actual refraction present at that time is not known, so the azimuth (which is not highly sensitive to refraction) is far more useful.

Jim Leonard took some high-quality pictures of the sun's disk using a telephoto lens on January 29, 2007. One of these photographs was used to make a prediction of the true azimuth of the corridor, which gave an azimuth of 245.632 degrees. While the exact position of Jim's camera when he took this picture was slightly uncertain, there may be some residual error in this calculaton.

### Accurate Timing

Modern higher-end digital cameras timestamp their photographs and store timings and exposure information in their EXIF data, which I can extract to determine exactly when a picture was taken. Of course, camera clocks are not necessarily set correctly (and we've seen that cameras are off by seconds, or minutes, or hours.) Lenny Foner came up with the brilliant solution of photographing his GPS receiver's time display with each camera. This allows us to find the time offset between EXIF dates and true GPS-based time. Of course, it is crucial that the GPS receiver has been outside recently, and was able to download ephemeris data from the satellites and set its time properly!

Taking pictures of an atomic-synchronized clock with the camera is also very useful. Note that Android devices usually display time as "GPS time" which may be incorrect by up to 17 seconds relative to UTC or any local time system, so be careful before you use them as a timebase. Compare with a known good atomic clock or site like www.time.gov.

### Accurate Positioning

In order to use photographs to make useful predictions, we need to know the exact position in the corridor from where a picture is taken. Using another camera to take a picture of your tripod's position with reference to objects in the hall is very useful. These position measurements should be accurate to an inch or two, as larger uncertainties create significant errors in predictions.

### Photography Tips

The best photographs for measurement have come from large telephoto lenses. It is also crucial that you know your exact position in the corridor from where each picture was taken. Camera shake has also proven to be a large issue, especially for longer-exposure moon photos. Use a tripod and remote control or shutter release, or even use the automatic timer, as movement of the camera when you press the shutter release greatly affects the quality of images.

Bracket the exposure! It's incredibly hard to take useful photographs that show the disc of the sun and also show features in the corridor at the same time. If your camera supports automatic exposure bracketing, set it to bracket the exposure as widely as possible and take multiple exposures!

## Refraction

Atmospheric refraction is one of the hardest issues to deal with when calculating apparent positions of objects close to the horizon. The amount of refraction varies with the temperature and atmospheric pressure that day, making predictions in advance rather difficult. In addition, as anyone who has ever seen a mirage over a hot road can attest, even a small layer of different-temperature air anywhere between you and the horizon can cause a huge difference in refraction. Proper calculation of refraction involves integrating over all the layers of atmosphere, which is, of course, nearly impossible.

As a result, we need to use some known-imperfect refraction calculations and correct as much as possible for the predicted temperature and atmospheric pressure during those days. My prediction programs use my empirically-found Fourier series (read the comments, they're interesting) for average hourly temperatures for Cambridge, which predicts temperatures not just for the day, but for the hour of the day based on 30 years of historical data. As I get closer to the date of the events, I'll try to see if the predicted temperature will be anomalously high or low.

The refraction equations that I use are outlined in Astronomical Algorithms by Jean Meeus, equation 16.4. These are available in the sun.frink file as the function refractionAngle.

## Horizon Blockage

From photographs taken during recent sun crossings, it is clear that the horizon is blocked significantly and that low crossings will be impossible to see. Higher crossings are looking far more favorable for crossings. The third-floor corridor is obstructed above an altitude of about 1 degree, so the window for visibility is very narrow indeed!

## Programs Used

The following are the programs used to predict the alignments. They are written in a programming language of my own design, called Frink, which excels at this type of physical calculations:

• mithengemoon - Calculates moon alignments with MIT's Infinite Corridor.
• mithengesun - Calculates sun alignments with MIT's Infinite Corridor.
• mithengecorridor - Data for the alignment of MIT's Infinite corridor.
• cambridgetempFourier.frink - My Fourier-series-based curve to predict average Cambridge temperatures for any moment of the year.
• sun - A large library of high-precision astronomical functions for predicting the location of the sun, moon, sunrise, atmospheric refraction, and more.
• mithengeplanets - Yes, you can make your own predictions for planet alignments! Requires the planets high-precision library.
• mithengeSirius - Calculate alignments of the brightest star, Sirius, with the corridor. (It crosses the centerline at some time every day, but at an altitude of about 1.65 degrees.)

For more information, you can also read the transcript or watch a video of a talk I gave at MIT about Frink in which I also discuss MIThenge measurements.

You can also read an interview in the Boston Globe where I was interviewed about MIThenge. (You'll need to click the "single page" or "printer friendly" link, (sorry, direct links don't work) or even register, to see page 2 where I was mentioned.)

## One Surveying Methodology

I took the average of the measurements obtained using differential GPS (GPS + WAAS), from two different locations. These points were outside the building, extending the baseline to about 446 meters. I averaged about 300 GPS points from each location. Using Frink to average the points, the best average for the azimuth came to 246.243 degrees. (I was glad to see that this agreed with my predicted azimuth based on historical photos.) This is approximately 0.77 degrees higher (to the right, closer to north) than the property-line azimuth guess. Please note, however, that the error circle is quite high for these readings, and are probably less accurate than Ken Olum's visual observations, or Lenny Foner's much better subsequent GPS readings, or photographic observations. They're presented here as a historical artifact.

### Plot - Both Sites

The following is a plot of the surveyed points at both the east and west end. Note that this graph is not "square," that is, the latitudes and longitudes are not corrected to reflect the proper aspect ratio.

### Plot - East Side

The following is a plot of the surveyed points on the east side. Note that this graph is not "square," that is, the latitudes and longitudes are not corrected to reflect the proper aspect ratio.

### Plot - West Side

The following is a plot of the surveyed points on the west side. Note that this graph is not "square," that is, the latitudes and longitudes are not corrected to reflect the proper aspect ratio.