I read of one some years ago that contained (supposedly) the longest word in a palindromatic phrase. Of course, the phrase was pretty senseless, but here it is:
“Named undenominationally rebel, I rile Beryl? La, no! I tan. I’m, O Ned, nude, man!”
Apparently the speaker was having a conversation with Ned about how the speaker’s nude sunbathing upset Beryl, or something. Anyone got a word longer than 18 letters in a palindrome?
I came up with one that was my sig on here for a while, based on the Panama one. I think it kind of makes sense - you may not agree 
A man, a plan, a case of reviled Spam. Onward, go deliver a dare, vile dog! Draw no maps, deliver foes! A canal, Panama!
It may not be the longest or the shortest, but I think that “Ed, I saw Harpo Marx ram Oprah W. aside” provides the most interesting mental image.
Aha ha! Aa! Haha
For those finding lava and wasps after a long search.
The shortest one was the second one.
Adam: “Madam, I’m Adam”.
Eve (pointing to herself): “Eve”.
nadohS
sdrageR
The longest was once said to be Napoleons response if he could have won a battle before he went to Elba. His answer able was I ere I saw Elba.
Nah, “aa,” a form of lava.
“Yo, Bob - mug o’ gumbo, boy!”
Georges Pérec, who was very much into playing with words, also wrote an extremely long French palindrome. Can be read here (yup, the url is a palindrome too), and yeah, it’s also pretty much gibberish. Poetic gibberish with a meaning, but gibberish nonetheless.
More impressively, he wrote a full novel without using the letter “e” once, despite it being the most used letter in French (as in English, I believe)
Texts written without a specific letter called lipograms. Ernest Vincent Wright wrote a 50,000 word novel titled Gadsby in 1939 which also omitted the E.
My favorite palindromic sentence is Satan, oscillate my metallic sonatas. Meaningless, of course, but you have to admire one which has an average word length of over 6 letters/word.
My favorite palindrome found in a dictionary is gipsy’s pig, a slang term for the hedgehog. It can be found in the OED, although I forget if it’s under “pig” or “gipsy”.
My favorite long palindrome goes like this:
T. Eliot, top bard, notes putrid tang emanating, is sad. I’d assign it a name: "Gnat-dirt upset on drab pot toilet."
Ella Minnow Pea is a recent lipogram novel, with a thematic focus on pangrams (sentences using all the letters). Alphabetical Africa is another lipogrammatic novel.
The book Lid off a Daffodil collects some palindromes.
Palindromes in other languages, anyone?
ילד כותב בתוך דלי
Interestingly, La Disparition has been translated in several languages, including English. I wonder if the results are close in meaning to the original.
I read that one in Games Magazine, oh… 28 years ago? They also ran a contest to find palindromes made up only of symmetrical letters, i.e. AHIMOTUVWXY
Someone submitted a story about a man and his friend Mia who visit a Japanese car dealership. She finds herserf irritated by the cheap little “tatami” mats that decorate the place and he encourages her to throw one at one of the cars:
AIM A TOYOTA TATAMI MAT AT A TOYOTA, MIA
There can’t really be a “longest” palindrome without some other stipulations, like disallowing repetition. I guess you could have “longest palindrome someone has bothered to write down.”
I guess Atlas Shrugged is merely the first half of an as-yet uncompleted palindrome that ends with “…si? Oh, W.” Maybe Francisco lamenting Bush43?
I remember once seeing the following “palindrome” suggested as the world’s longest, seeing how it can be made arbitrarily long, although practically meaningless:
Take any string of letters or words. Reverse it, and put the two strings on either side of this:
<Original string> “sides reversed is” <Reversed string>
There is an indefinitely long internal palindrome that’s possible. It’s not meaningless, but is rather boring.
Consider the amino acid glycine. Its combinative form is glycyl-, so if you combine two glycines together, you get glycylglycine. That word has two internal 7-letter palindromes: one from the begining to the last G and the other from the first C to the last.
Combine three glycines and you get glycylglycylglycine, which has two 13-letter internal palindromes, again one from the begining to the last G and the other from the first C to the last.
Those of you familiar with organic chem can see where this is going. There’s no actual limit to the number of glycines that can be strung together, so there’s no limit to how long you can make these internal palindromes. Note they’ll all be of length 6N+1, where N+1 is the number of glycines in the chain.
Of course, in practice, organic chemists don’t write out the full name of these really long compounds. Somewhere around 5 or 6 they start to abbreviate them: gly[sub]6[/sub] or gly-gly-gly-gly-gly or something like that. However, that doesn’t mean that you can’t write them out fully. But as I said, it’s fairly boring.
Googling, I get two hits for glycylglycylglycylglycylglycylglycylglycine (gly[sub]7[/sub]) and none for anything longer.
