Yesterday, I received a call from Mr. X who asked for my assistance in fixing his time machine, which he suspected had been damaged during one of his adventures. Since an initial inspection revealed no superficial damage, I asked for materials from his diary of four of his travels to help me ascertain the issue.

Entry 1.

May 1890

Today I visited the newly constructed Eiffel Tower in Paris for the world fair. It is quite a marvelous structure and towers over the rest of the city. In fact, I believe that it has claimed the title of the world's tallest building. Inside, one may find all kinds of shops and restaurants. Marvelous!

Entry 2.

Mar 1928

Today, I may have accidentally changed history. I visited Alexander Fleming's lab two years before the discovery of penicillin, and when we took a lunch break, I mentioned that there was some mold on the bread in the cabinet. Upon hearing my words, he thoughtfully stared at the mold and appeared to be deep in thought.

Entry 3.

June 1911

Today, I witnessed the Tunguska meteor incident. From my vantage point, I saw a bright flash and a brief moment later, I heard a deafening roar which came accompanied by a vicious shaking of the ground. Although I was in no danger, I was nonetheless overcome by a rush of chill fear, as I witnessed the unstoppable force of nature.

Entry 4.

July 1911

Today, I once again visited the site of the Tunguska meteor incident. To my surprise, I could find no signs of the explosion and no sign that the disaster had happened. Impossible! Had I somehow irreparably damaged history? From a nearby town, I purchased a newspaper, and saw that the date is indeed July 12, 1911. What in the world has happened?

After admonishing Mr. X to take better care of preserving history, I told him that I would fix the time machine within a weeks time.

What was wrong with the machine?

Edit: It was brought to my attention that there was no crater from the explosion.

Edit: As a clarification, each entry represents one time that Mr. X travels back in time.


2 Answers 2


Partial Answer:

Event 1:

The opening of the Eiffel Tower was actually May 1889 during the world fair, which is 1 year before the date provided.

Event 2:

It was mentioned that he visited Fleming 2 years before the discovery of penicillin. However, it was discovered in 1928. So Mr. X was 2 years off.

Event 3:

The event actually happened in June of 1908. Mr. X's visit to the meteor is 3 years off.

Even 4:

This may be referring to "A Visitor from Heavenly Space", which appeared on July 12, 1908 in Sibirskaya Zhizn (Siberian Life) in the town of Tomsk (source).

Possible Solution:

My initial guess is the time machine represented the incorrect dates by an increasing number of years based on the times traveled. Except for the 4th date, which should have been 1907. It's quite possible the time machine reset itself every 4th attempt which might explain the date difference. One thing to note is that Russia (USSR) didn't use the Gregorian Calendar until 1918, they lost 13 days in February. I'm thinking this may perhaps be the reason for the incorrect date on the newspaper which may explain why the "event" hadn't happened yet.

  • $\begingroup$ Is it not simply that rot13(gur znpuvar vf ercbegvat gur pheerag qngr ol na rkgen lrne bss rnpu gvzr? Fb gur ynfg gvzr, ur guvaxf ur'f va avargrra ryrira ohg ur'f npghnyyl va avargrra bu frira, n lrne orsber gur rirag unccrarq)? (On a side note, every time I ever visit rot13.com I always copy the cleartext by mistake!!) $\endgroup$
    – Mohirl
    Nov 13, 2018 at 15:40
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    $\begingroup$ Ah! Fair point! $\endgroup$
    – Mohirl
    Nov 13, 2018 at 15:57
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    $\begingroup$ Your first sentence in the possible solution more or less has what I had in mind; @Mohirl also correctly mentions the rationale for the fourth event. rot13 (Rnpu gvzr ur geniryf onpx, znwbe riragf unccra fhpprffviryl bar lrne yngre va uvfgbel. Jura ur vf gurer va 1911, gur rirag jvyy unccra va n yvggyr yrff guna bar lrne. ) $\endgroup$
    – 1848
    Nov 14, 2018 at 8:20
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    $\begingroup$ This is all fine and dandy, but how on earth did that year appear on the newspaper? $\endgroup$
    – Bass
    Nov 14, 2018 at 8:52
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    $\begingroup$ Haha I guessed right (comment to other answer) :-) $\endgroup$ Nov 14, 2018 at 21:58

Possibility 1:

On his fourth trip, considering he thinks it should be 1911, and based on the behavior of the previous trips, then he should actually be in 1907, a year prior to the event. This would explain then why there is no sign of the event. The issue though is how the paper would still show 1911...

Possibility 2:

If he actually did go to 1911, then does Mr. X think that the Tunguska event actually happened in 1911 and not 1908? 3 years might be enough time for the damaged areas to recover and not show major signs of damage, at least to the likes he's expecting.

Alright, so I'm confused:

The Tunguska event occurred on June 30th 1908 and no impact crater has been found...


Why does his entry say June 1911? And why is he later looking for a crater?

Other Questions:

1. What year is Mr. X from?
2. Is he from the same universe? (if parallel universes etc)
3. Is there actually something wrong with the machine?

  • $\begingroup$ I have made an edit about the crater. Thanks for letting me know about that. Can't say too much about anything else :) $\endgroup$
    – 1848
    Nov 12, 2018 at 22:20
  • $\begingroup$ For your 'other question' #2, what if, instead of rot13(orvat zvfpnyvoengrq ol n lrne zber rnpu gvzr), it was actually rot13(nygrevat gur pnyraqne) somehow... which makes no sense of course, but time travel rarely does... $\endgroup$ Nov 13, 2018 at 0:47

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