What is your favorite paradox?

https://www.reddit.com/r/AskReddit/comments/hg1uax/what_is_your_favorite_paradox/

created by [deleted] on 26/06/2020 at 05:35 UTC

4394 upvotes, 64 top-level comments (showing 25)

Comments

Comment by Xaxos92 at 26/06/2020 at 06:58 UTC

5482 upvotes, 7 direct replies

No one goes there because it's crowded.

Comment by [deleted] at 26/06/2020 at 06:21 UTC

4946 upvotes, 7 direct replies

Entry level position requiring 5+ years of experience.

Comment by kylfra at 26/06/2020 at 09:01 UTC

2002 upvotes, 9 direct replies

The bootstrap paradox. Imagine you know all of Elvis’ music and every single thing about him so you go back in time to see him only to find he doesn’t exist so you play his music and the you become Elvis. He was never original but it’s still a stable paradox.

Comment by BurpYoshi at 26/06/2020 at 11:00 UTC

1076 upvotes, 2 direct replies

This thread has taught me that a lot of people wrongly think a difficult question to answer is a paradox.

Comment by wearekinetic at 26/06/2020 at 05:45 UTC

2298 upvotes, 9 direct replies

I hate myself, but I think I’m better than everyone.

Comment by izackthegreat at 26/06/2020 at 09:45 UTC

1755 upvotes, 9 direct replies

Time travel. If time travel was possible, then presumably someone from the future would have already gone back in time to change the past. Therefore, when someone says they, for example, would have stopped Hitler, they actually wouldn't because someone already would have made that correction in time. Instead, that must have been, unfortunately, the best possible outcome out of all possible outcomes. Either that or time travel just isn't possible which seems significantly more likely.

Comment by SafetyDanceInMyPants at 26/06/2020 at 11:50 UTC

931 upvotes, 4 direct replies

There's a lake down near my parents house with one lovely dock sitting out on one side, and another lovely dock sitting out on the other side. Probably those two.

Comment by Zeta42 at 26/06/2020 at 06:37 UTC

3117 upvotes, 9 direct replies

Theseus' ship.

You take a ship and replace every single part in it with a new one. Is it still the same ship? If not, at what point does it stop being the ship you knew? Also, if you take all the parts you replaced and build another ship with them, is it the original ship?

Comment by bomber665_ko at 26/06/2020 at 06:00 UTC

6257 upvotes, 10 direct replies

If you ask Rick Astley for his copy of the movie Up, he cannot give it to you as he will never give you up. However, in doing so he lets you down. Thus creating the Astley Paradox

Comment by Shrumboy114 at 26/06/2020 at 05:37 UTC

907 upvotes, 2 direct replies

Trust me when I say this, trust no one.

Comment by Cleverbird at 26/06/2020 at 08:48 UTC

589 upvotes, 7 direct replies

The Fermi Paradox is one of my all time favorites!

The Fermi paradox, named after Italian-American physicist Enrico Fermi, is the apparent contradiction between the lack of evidence for extraterrestrial civilizations and various high estimates for their probability (such as some optimistic estimates for the Drake equation).

The following are some of the facts that together serve to highlight the apparent contradiction:

There are billions of stars in the Milky Way similar to the Sun.
With high probability, some of these stars have Earth-like planets.
Many of these stars, and hence their planets, are much older than the sun. If the Earth is typical, some may have developed intelligent life long ago.
Some of these civilizations may have developed interstellar travel, a step humans are investigating now.
Even at the slow pace of currently envisioned interstellar travel, the Milky Way galaxy could be completely traversed in a few million years.
And since many of the stars similar to the Sun are billions of years older, the Earth should have already been visited by extraterrestrial civilizations, or at least their probes.
However, there is no convincing evidence that this has happened.

Kurzgesagt did a great breakdown on this paradox

Comment by [deleted] at 26/06/2020 at 05:36 UTC*

735 upvotes, 7 direct replies

[removed]

Comment by Jim3001 at 26/06/2020 at 14:56 UTC

138 upvotes, 3 direct replies

There is a time travel paradox that involves a door.

So you have a field and there is a free standing door. You are the guard you watch from side on. The door only lets people move 24 hours. Go in one way and it's 24 hours into the future. Go in the other and it 24 hours into the past.

One day you see a guy come out into the past. But unlike most people he doesn't leave. He stays in the field near the door. Then, precisely 24 hours after he arrives, he goes into the door.

The paradox is this man's existence. To the casual observer he only exists for the 24 hours between exit and entrance.

Comment by flyingsaucerinvasion at 26/06/2020 at 06:13 UTC

540 upvotes, 5 direct replies

If you send an object into a time loop, (go back in time and give it to yourself). What is the age of the object? Infinite? Zero?

Comment by L_Flavour at 26/06/2020 at 15:13 UTC

91 upvotes, 2 direct replies

Gabriel's horn / Torricelli's trumpet

It's a (infinitely long) 3 dimensional object, of which the shape can be created by rotating the graph of f(x) = 1/x for x > 1, and should look something like this[1].

1: https://upload.wikimedia.org/wikipedia/commons/thumb/8/89/GabrielHorn.png/1280px-GabrielHorn.png

The paradox is that this object has an infinitely large surface area, but a finite volume. So no amount of paint would be enough to paint the whole thing, but you can still fill the whole trumpet by pouring a finite amount of paint into it.

Comment by NeutralityTsar at 26/06/2020 at 06:44 UTC

585 upvotes, 3 direct replies

The coastline paradox![1] I like geography and fractals, so it's the perfect paradox for me.

1: https://www.youtube.com/watch?v=kFjq8PX6F7I

Comment by leomonster at 26/06/2020 at 06:09 UTC

1230 upvotes, 4 direct replies

The human brain paradox.

You see, our brains are so complex that we can't fully understand how they work. If they were simpler, we totally could. Except that if our brains were simpler, we'd be more stupid, and still unable to fully understand our own brains.

Comment by [deleted] at 26/06/2020 at 09:24 UTC

393 upvotes, 8 direct replies

The paradox of omnipotent God. God can't make a rock too heavy he can't lift... Or he can make a rock too heavy he can't lift. Either way there's some he can't do.

Comment by obeyyourbrain at 26/06/2020 at 05:48 UTC

678 upvotes, 6 direct replies

The Paradox of Tolerance."In order to maintain a tolerant society, the society must be intolerant of intolerance."

Comment by [deleted] at 26/06/2020 at 05:41 UTC

267 upvotes, 3 direct replies

[removed]

Comment by artsy-potat0 at 26/06/2020 at 06:54 UTC

271 upvotes, 4 direct replies

Nothing is impossible.

If nothing is impossible it’s possible for something to be impossible

Comment by Hardyminardi at 26/06/2020 at 07:51 UTC

375 upvotes, 2 direct replies

Pinocchio, "my nose is just about to grow."

Comment by DrNameGame at 26/06/2020 at 15:05 UTC

77 upvotes, 3 direct replies

A time traveler goes into a book store and purchases a copy of Shakespeare’s Hamlet. The time traveler goes back in time and shows Hamlet to Shakespeare. Shakespeare loves it so much that he copy’s it word for word and passes it off as his own work. Hamlet becomes so popular that it is spread throughout the world and millions of copies are made. One of these copies ends up in book store and is purchased by the time traveler. Who wrote Hamlet?