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贴图灌水、文学娱乐专区 » Paradox — The Tortoise and the Hare [Repost]
Printable Version  1,297 / 14
Floor1 ko20010214 Posted 2003-06-15 00:00
版主 Posts 1,628 Credits 7,296
The tortoise and the hare are having a race. The tortoise runs 10 meters first, and then the hare starts running. When the hare reaches the 10-meter point, the tortoise has moved a little farther ahead. When the hare reaches the tortoise's new position, the tortoise has again moved a little farther ahead. And so on. In this way, the hare can only get infinitely close, but can never pass the tortoise. This obviously does not match the facts. So where is the problem? According to this theory, for any two objects, if there is an initial displacement difference, the faster one can never catch up with the slower one. So where exactly is the mistake?

sorry, this isn't a logic puzzle, it's a paradox.


Floor2 西西 Posted 2003-06-15 00:00
初级用户 Posts 87 Credits 283
I give up, I can't make sense of the question.
Floor3 Wengier Posted 2003-06-15 00:00
系统支持 Posts 10,521 Credits 27,736
Oh, I get it now... This problem is in my math textbook!
Floor4 ko20010214 Posted 2003-06-15 00:00
版主 Posts 1,628 Credits 7,296
What do you understand? Tell us.
Floor5 Wengier Posted 2003-06-15 00:00
系统支持 Posts 10,521 Credits 27,736
The explanation given in the original English version of that problem is like this:

In the fifth century B.C., the Greek philosopher, Zeno of Elea, posed four problems, now known as Zeno's paradoxes. These problems wre intended to challenge some of the then-current ideas about space and time.

And then comes this problem.
Floor6 ko20010214 Posted 2003-06-15 00:00
版主 Posts 1,628 Credits 7,296
yes! But you still haven't told everyone what it is that you understood.
Floor7 nre Posted 2003-06-15 00:00
银牌会员 Posts 361 Credits 1,210
Because the finish point is always set by the tortoise. The hare can only pass an existing reference point, but that reference point is always being updated over time. For something that hasn't happened yet, the question of surpassing it can't exist, unless that hare can outrun time.
Floor8 如是大师 Posted 2003-06-15 00:00
元老会员 Posts 3,351 Credits 9,654 From 湖北
Exactly..
Floor9 nre Posted 2003-06-15 00:00
银牌会员 Posts 361 Credits 1,210
KO, don't forget to post the answer!!!
Floor10 yiyesong Posted 2003-06-16 00:00
元老会员 Posts 632 Credits 1,987
What nre said makes sense. The reason is that this problem doesn't take time into account, only position. For example, the hare reaches the tortoise's new position in one second, while the tortoise took a full minute, and by then who knows where the hare has already gone. So they are being compared over unequal times. Unless time doesn't exist.
Floor11 yiyesong Posted 2003-06-16 00:00
元老会员 Posts 632 Credits 1,987
Let me correct that a bit. It should be understood this way: within a certain specific time range, the hare cannot catch up with the tortoise. Because the problem is like this: when the hare gets infinitely close to the tortoise, time at that moment is also getting infinitely close to zero. In other words, time has come to a standstill.
For example, the hare takes 10 seconds to run the 10 meters that the tortoise got as a head start, and during that time the tortoise runs 1 meter. Then the hare takes 1 second to run that 1 meter, while the tortoise runs 0.1 meter; then the hare takes 0.1 second to run 0.1 meter, while the tortoise runs 0.01 meter; then the hare takes 0.01 second to run 0.01 meter, while the tortoise runs 0.001 meter.......
In that case, time starts getting infinitely close to zero. That is to say, within 11.111111....... seconds, the hare cannot catch up with the tortoise. But if it goes beyond that time, even by just a tiny bit, the hare passes the tortoise.
Floor12 boyachang Posted 2003-06-16 00:00
初级用户 Posts 35 Credits 195
It's just a limit problem!
Floor13 MYS Posted 2003-06-17 00:00
元老会员 Posts 1,637 Credits 5,170 From 广东佛山
This is a limit problem.
Floor14 boyachang Posted 2003-06-17 00:00
初级用户 Posts 35 Credits 195
10*(1+1/10+1/100+……)
Within the limit, the hare definitely can't catch up with the tortoise, but once past that limit, the hare can pass the tortoise.
Floor15 ko20010214 Posted 2003-06-17 00:00
版主 Posts 1,628 Credits 7,296
This is switching concepts.
It's swapping the concept of infinite space with the concept of infinite time...
A distance problem is a spatial problem.
Whether it can catch up or not is a time problem.
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