Time Travel, Truth and the Color Of My Shirt.

Have you ever played “truth and lies?” It’s an icebreaker game where you make three statements – two are supposed to be true, and one false. It helps people in a group to get to know each other, and see how well they already do.

Well, next time you play, you might like to bend it into a mind-twisting IQ puzzle.

Here’s my answers for a recent game of truth and lies. It was played over the internet, so there was no way for people to see what color shirt I was wearing. I said:

1. My second statement is true, or my shirt is green.
2. My third statement is true, and my shirt is blue.
3. My first statement is false, or my shirt is not red.

Can you figure out the color of my shirt? If you think you can, post the answer here.

Now, time machines: a few weeks ago, I posed you this puzzle:

Ten years ago, in 2004, you got a letter. The letter told you that your future self, from 2014, sent you a message via time machine. The catch? The message was just a single English word. That’s all your future self, from 2014, was allowed to send.

Now, it’s 2014, you are standing in the offices of Temporal Telegrams, preparing to compose your message. One English word. Choose carefully!

What single word will you send your past self from 2004, to have the maximum possible positive impact on your life?

The problem is, there’s not much you can communicate in a single word. You want to tell yourself to buy Apple shares? You could say “Apple”, but how sure are you that you’d know you meant the company, not the fruit, or that you were supposed to buy shares? Even potentially mind-changing advice such as “marry her” or “take the job” (or don’t!) is hard to compact into a single word.

Or is it?

Here’s my solution:

• When I learn, in 2004, that Temporal Telegrams exists, and that I’m going to use them 10 years later, I buy myself a dictionary and a safe.
• Then, I carefully number each word in the dictionary, except the last (let’s say that’s ‘zymurgy’).
• Next, I write a long, long essay. Several pages. Guesses about what stocks to buy, or mistakes I imagine I might make, and want to avoid. Speculations about what things to not worry about, or pay careful attention to.
• Then, I visit the office of Temporal Telegrams, and collect my letter from myself in 2014 – the single word.
• I bring the letter home, and look it up the word in the dictionary.

Let’s pause here, and flash forward to 2014. I’m about to send a word to myself. Before I visit Temporal Telegrams to send that single word, here’s what I do:

• First, I write a long essay, explaining what I should do to make my life from 2004 to 2014 awesome in every way. Stocks to buy, obviously. Mistakes to avoid. Things to warn friends about or recommend they do. Advice not to worry about some things, or pay careful attention to others.
• Now, I’m only allowed to send back a single word. Fortunately, though, I have a safe I bought in 2004. I open it. There, I find a dictionary, with every word numbered, and a letter written by me in 2004.
• I lay out my 2014 essay and my 2004 essay side by side. Then, I start to compare them, letter by letter.
• If the essays are identical, I write ‘zymurgy’ on a piece of paper, and bring it to Temporal Telegrams.
• Perhaps more likely, the essays will differ at some point. Let’s say they differ at the 23rd letter. Then, I look up in my dictionary which word is the 23rd word, and write that instead.

All right, let’s flash back again to 2004.

• I visit the office of Temporal Telegrams, and collect the single word I sent from 2014 to 2004.
• I look up the word in the dictionary, and find out the number I’ve assigned to that word.
• If, say, the number is 23, I know I have to change the 23rd letter in my essay. I change it in a systematic way, A to B, B to C, etc. Z to a space. Cycle through the various punctuation symbols and back to A. Then, I continue the essay, keeping the first 22 letters, but changing the rest.
• On the other hand, perhaps the word is zymurgy. Then, my future self has sent me a clear message – my essay is exactly what I would have written in the future.
• I seal up the modified essay, and the numbered dictionary, in the safe.

In this way, My single word from the future becomes a message about the correctness of an entire essay’s worth of text. I don’t have to sen back the word ‘Apple’. The word ‘Zymurgy’ is enough to tell me, in 2004, that my guess “buy Apple shares now, sell when Steve Jobs dies” is 100% on the mark – along with the rest of my life-changing essay.

But what if it doesn’t say zymurgy? That’s impossible, since it would lead to a paradox – if the 23rd letter of the two essays were not the same, I would have changed it.

So, the restriction to a single word is not a real restriction at all. Even if the message sent through Temporal Telegrams was a single “Yes/No”, that would be enough to transmit an unlimited amount of information from the future to the past.

Food for thought!