1
   

Paradoxes?

 
 
Reply Wed 30 Jan, 2008 02:00 pm
Arent these kinda weird?
and can someone come up with any?

I found a few just so you could get an idea.

Princess and the Crocodile

An Egyptian princess was walking beside a pool, when suddenly a crocodile appeared in front of her. The princess knew she was lost, but to her astonishment the crocodile spoke in a human voice and said:

I will ask you a question. If you give the right answer i will let you live. If the answer is wrong, i will drag you to my nest and eat you.

Seeing no way way out, the Princess bowed and bade him to ask the question.

The crocodile said: ""The question is: Will i drag you to my nest and eat you?"

Which answer did the princess give the crocodile?

If the princess answers "yes, you will eat me", what will the crocodile do?

1. If he eats her, the princess would have given the right answer, so he shouldnt eat her.
2. If he doesn't kill her the princess would have given the wrong answer and the crocodile would have to kill/eat her.

With this answer there would be a standstill. Either action of the crocodile would be wrong, contrary to his vow.

If the princess answers "no, you will not eat me.# what must the crocodile do?

1. he must let the princess go. she will have given the right answer.
2. he must eat the princess, for then she would have given the wrong answer.

Conclusion

It is a very stupid crocodile. he should have eaten the princess in the first place, and there would have been no confusion.

Hilbert's paradox of the Grand Hotel:

If a hotel with infinitely many rooms is full, it can still take in more guests.

Situation:

In a hotel with a finite number of rooms, it is clear that once it is full, no more guests can be accommodated. Now, imagine a hotel with an infinite number of rooms. One might assume that the same problem will arise when an infinite number of guests come along and all the rooms are occupied. However, in an infinite hotel, the situations "every room is occupied" and "no more guests can be accommodated" do not turn out to be equivalent. There is a way to solve the problem: if you move the guest occupying room 1 to room 2, the guest occupying room 2 to room 3, etc., you can fit the newcomer into room 1.

It is also possible to make room for a countably infinite number of new clients: just move the person occupying room 1 to room 2, occupying room 2 to room 4, occupying room 3 to room 6, and so on, and all the odd-numbered rooms will be free for the new guests.

Now imagine a countably infinite number of coaches arrive, each with a countably infinite number of passengers. Still, the hotel can accommodate them: first empty the odd numbered rooms as above, then put the first coach's load in rooms 3n for n = 1, 2, 3, ..., the second coach's load in rooms 5n for n = 1, 2, ... and so on; for coach number i we use the rooms pn where p is the i+1-th prime number. You can also solve the problem by looking at the license plate numbers on the coaches and the seat numbers for the passengers (if the seats are not numbered, number them). Regard the hotel as coach #0. Interleave the digits of the coach numbers and the seat numbers to get the room numbers for the guests. The guest in room number 1729 moves to room 01070209 (i.e, room 1,070,209. Leading zero added to clarify we take the first digit of the coach number first.) The passenger on seat 8234 of coach 56719 goes to room 5068721394 of the hotel.

Some find this state of affairs profoundly counterintuitive. The properties of infinite "collections of things" are quite different from those of ordinary "collections of things". In an ordinary hotel (with more than one room), the number of odd-numbered rooms is obviously smaller than the total number of rooms. However, in Hilbert's aptly named Grand Hotel, the "number" of odd-numbered rooms is as "large" as the total "number" of rooms. In mathematical terms, this would be expressed as follows: the cardinality of the subset containing the odd-numbered rooms is the same as the cardinality of the set of all rooms. In fact, infinite sets are characterized as sets that have proper subsets of the same cardinality. For countable sets, this cardinality is called \aleph_0 (aleph-null).

An even stranger story regarding this hotel shows that mathematical induction only works from an induction basis. No cigars may be brought into the hotel. Yet each of the guests (all rooms had guests at the time) got a cigar while in the hotel. How is this? The guest in Room 1 got a cigar from the guest in Room 2. The guest in Room 2 had previously received two cigars from the guest in Room 3. The guest in Room 3 had previously received three cigars from the guest in Room 4, etc. Each guest kept one cigar and passed the remainder to the guest in the next-lower-numbered room.

The cosmological argument

A number of defenders of the cosmological argument for the existence of God, such as Christian philosopher William Lane Craig, have attempted to use Hilbert's hotel as an argument for the physical impossibility of the existence of an actual infinity. Their argument is that, although there is nothing mathematically impossible about the existence of the hotel (or any other infinite object), intuitively (they claim) we know that no such hotel could ever actually exist in reality, and that this intuition is a specific case of the broader intuition that no actual infinite could exist. They argue that a temporal sequence receding infinitely into the past would constitute such an actual infinite.

However, the paradox of Hilbert's hotel involves not just an actual infinite, but also supertasks; it is unclear whether this claimed intuition is really the physical impossibility of an actual infinite, or merely the physical impossibility of a supertask. A causal chain receding infinitely into the past need not involve any supertasks. Thomas Aquinas' Summa Theologica is a well-known attempt to prove the existence of God through infinite regressions
  • Topic Stats
  • Top Replies
  • Link to this Topic
Type: Discussion • Score: 1 • Views: 348 • Replies: 1
No top replies

 
contrex
 
  1  
Reply Thu 31 Jan, 2008 01:39 am
Yes, there's a lot of cool stuff on Wikipedia.
0 Replies
 
 

 
  1. Forums
  2. » Paradoxes?
Copyright © 2024 MadLab, LLC :: Terms of Service :: Privacy Policy :: Page generated in 0.02 seconds on 05/06/2024 at 01:19:14