Category Archives: Time definition | 時間定義

Deus ex machina 2

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天外救星 2

Towards the end of the 19th century, Friedrich Nietzsche criticized Euripides for making tragedy an optimistic genre via use of the device, and was highly skeptical of the “Greek cheerfulness”, prompting what he viewed as the plays’ “blissful delight in life”.

Nietzsche argues that the deus ex machina creates a false sense of consolation that ought not to be sought in phenomena.

— Wikipedia on Deus ex machina

2014.07.12 Saturday ACHK

Deus ex machina

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天外救星

Deus ex machina is a plot device whereby a seemingly unsolvable problem is suddenly and abruptly resolved by the contrived and unexpected intervention of some new event, character, ability or object. Depending on how it is done, it can be intended to move the story forward when the writer has “painted himself into a corner” and sees no other way out, to surprise the audience, to bring the tale to a happy ending, or as a comedic device.
  
Origin of the expression

The Latin phrase deus ex machina, from deus, meaning “a god”, ex, meaning “from”, and machina, meaning “a device, a scaffolding, an artifice”, is a calque from Greek ἀπὸ μηχανῆς θεός (apò mēkhanḗs theós), meaning “god from the machine”. Such a device was referred to by Horace in his Ars Poetica (lines 191–2), where he instructs poets that they should never resort to a “god from the machine” to resolve their plots “unless a difficulty worthy a god’s unraveling should happen”. He was referring to the conventions of Greek tragedy, where a machine is used to bring actors playing gods onto the stage. The machine could be either a crane (mechane) used to lower actors from above or a riser that brought actors up through a trapdoor.

Ancient usage

Aristotle criticized the device in his Poetics, where he argued that the resolution of a plot must arise internally, following from previous action of the play …

In modern literature

A deus ex machina is generally deemed undesirable in writing and often implies a lack of creativity on the part of the author. The reasons for this are that it does not pay due regard to the story’s internal logic (although it is sometimes deliberately used to do this) and is often so unlikely that it challenges suspension of disbelief, allowing the author to conclude the story with an unlikely, though perhaps more palatable, ending. Following Aristotle, Renaissance critics continued to view the deus ex machina as an inept plot device, …

— Wikipedia on Deus ex machina

2014.07.11 Friday ACHK

天外救星

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「天外救星」是意料外的、突然的、牽強的解圍角色、手段或事件，在虛構作品內，突然引入來為緊張情節或場面解圍。近似詞有「天降神兵」和「如有神助」等。

Deus ex machina

拉丁語片語Deus ex machina（英譯：God from the machine）翻譯自希臘語，意思是「機關跑出的神」，中文一般翻譯為「舞台機關送神」、「機械降神」、「機器神」、「解圍之神」等。

在古希臘戲劇，當劇情陷入膠着，困境難以解決時，突然出現擁有強大力量的神，將難題解決，令故事得以收拾。方法是利用起重機，或起升機的機關，將扮演神的演員，下降至舞台上。這種表演手法是人為的，製造出意料之外的劇情大逆轉。

現代批評

這種手法通常被評論家認為是，不高明的說書技巧，因為它破壞了故事的內在邏輯，縱使有時候會為了這個理由，而故意採用。繼亞里士多德之後，文藝復興時期評論家將其視為，一種迂拙的情節計策…

— 改編自維基百科

2014.07.10 Thursday ACHK

Time Reversal 2

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Lessons from the Light, 5.3

They found that T is indeed violated.

…

All perfectly fine and glorious. The pet peeve only comes up in the sub-headline of the SLAC press release: “Time’s quantum arrow has a preferred direction, new analysis shows.” Colorful language rather than precise statement, to be sure, but colorful language that is extremely misleading.

“Time’s arrow,” in the sense that the phrase is conventionally used (by the kind of folks who would conventionally use such a phrase), refers to the myriad ways in which the past is different from the future in our macroscopic experiential reality. Entropy increases with time; … This new measurement in the B meson system — indeed, the entire phenomenon of T violation — has absolutely nothing to do with that arrow of time.

The reason is pretty simple to understand. The arrow of time centers on the concept of irreversibility — things happen in one direction of time but not the other. You can scramble eggs, but not unscramble them, etc. That’s not at all what’s going on in the B mesons. The oscillations between different types of meson happen perfectly well in both directions of time, just with ever-so-slightly different rates.

…

The particle-physics processes in question, in other words, are perfectly reversible. Information is not lost over time; you can figure out exactly what the quantum state used to be by knowing what it is now. (It’s “unitary,” to use the jargon word.) That’s utterly different from the macroscopic arrow of time.

…

— Time-Reversal Violation Is Not the “Arrow of Time”

— Sean Carroll

2014.06.13 Friday ACHK

Time Reversal

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Lessons from the Light, 5.2

Note that among C, P, T, only T is an “antilinear operator” which means that

T | \lambda \psi \rangle = \lambda* T | \psi \rangle

including the asterisk which means complex conjugation (that’s the reason of the prefix, anti-). Various combinations of C, P, T are linear or antilinear depending on whether T is included.

Note that the complex conjugation is needed for the time reversal already in ordinary non-relativistic quantum mechanics because the complex conjugation is the only sensible way to change ( \exp(+ipx/\hbar) ) to ( \exp(-ipx/\hbar) ), i.e. to change the sign of the momentum p – and the velocity v = dx/dt – which is needed for particles to evolve backwards.

— BaBar directly measures time reversal violation

— Lubos Motl

2014.06.11 Wednesday ACHK

長頸豹 3

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尋找時間的定義 1.2

SICM, 3.2 | SICP, 2.2

這段改編自 2010 年 4 月 10 日的對話。

涉獵多門知識，即使對於「本行」的發展，也會有意想不到的幫助。

例如，我對「什麼是時間」這個物理問題，有極之大的興趣。我想像，如果我只閱讀和研究物理，可能窮一身的時間，也沒有寸進。

估不到，在大概 2006 年，我從一本電腦界的神作中，得到了靈感，開始對「時間定義」有一點理解。然後在今年（2010），再加上我在大學時代時，長期訓練得來的「語理分析」功力，我破解了，「時間」的大部分意思。

（安：你上星期也有提及過，那本電腦界的神作。）

又例如，如果一個人過身後，仍然以某種形式存在的話，究竟確實是以哪一種，或者怎麼樣的形式來存在呢？

從物理和電腦知識中，我得到了一些關鍵靈感。

「靈感」中的「靈」，其實就是解「靈活」、「靈通」，即是有大量和多類型的資料或消息來源。

— Me@2014.06.03

2014.06.03 Tuesday (c) All rights reserved by ACHK

Whole-part conflict

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paradox ~ mixing levels

Mixing levels is a problem of whole-part conflict.

“x = 1 – x” has no conflicts but “x = x – 1” does, because “x = x – 1” means “the whole is equal to a part“, which is logically impossible, according the definitions of the words “whole” and “part”. 

— Me@2012.10.26

2014.05.04 Sunday (c) All rights reserved by ACHK

回到過去 3

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Cumulative concept of time 20

你想回到過去，重新經歷年青時的生活。但是，你有沒有想過，「經歷」即是「走過」，又名「離開」。「經歷過去」，其實就即是「到達現在」。

（Me：那樣，如果我只是「回到過去」，但不「經歷過去」，我豈不是不會「失去青春」？）

無錯。但是，回到過去，但不經歷過去，即是停止時間。這個現象，學名叫做「英年早逝」。那不是好事。

但是，你亦不用灰心，因為，「經歷過去」或者「到達現在」，並不代表你「失去過去」。「現在」，就是「經歷了的過去」。「過去」，是「現在」的一部分。「過去的你」，是「現在的你」的一部分。你從來也沒有失去過，年青時候的自己。

正如，「使用金錢」的意思是，令它消失，從而換取其他，更有價值的東西。「使用金錢」而不開心，是因為你花太多的金錢，去買了一些，用處不大的東西。

同理，你覺得「失去」青春，是因為你沒有百分百地利用，當時的時光，去賺取最多的經驗，累積最多的財富，創造最多的作品。

— Me@2014-04-24 01:56:35 AM

2014.04.27 Sunday (c) All rights reserved by ACHK

The fifth floor

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回到過去 2 | 幼稚建築論 2 | Cumulative concept of time 19

The fifth floor cannot exist without the first 4 floors.

— Me@2012.10.24

That’s why time travel is logically impossible.

— Me@2014.04.17

If you remove the first 4 floors, the original fifth floor is not the “fifth” floor anymore. Instead, it would become the first floor.

— Me@2014.04.16

2014.04.17 Thursday (c) All rights reserved by ACHK

Energy

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Energy is the ability of causing change.

Change is related to time.

That’s why energy is related to time.

— Me@2012-10-22 01:45:17 PM

Application of Noether’s theorem allows physicists to gain powerful insights into any general theory in physics, by just analyzing the various transformations that would make the form of the laws involved invariant. For example:

  • the invariance of physical systems with respect to spatial translation (in other words, that the laws of physics do not vary with locations in space) gives the law of conservation of linear momentum;
  • invariance with respect to time translation gives the well-known law of conservation of energy

— Wikipedia on Noether’s theorem

2014.03.25 Tuesday (c) All rights reserved by ACHK

The Beginning of Time, 3.2

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Cumulative concept of time 1.3.2

The past is part of the future.

The first cause is the smallest part.

cause ~ component

The first cause is not a boundary, because there is no “before”.

The first cause is a physical limit, not a physical boundary.

The first cause is a logical boundary, not a physical one.

— Me@2012.10.17

— Me@2014.02.03

2014.02.03 Monday (c) All rights reserved by ACHK

回到過去

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Apology 3 | Punishment 4 | 以直報怨 4 | Regret 4

幼稚建築論, 時間旅行

— Me@2009.12.19

甲：我以前太幼稚了，犯了很錯誤。如果可以給我回到過去，我就能夠避免那些錯誤，不會再犯。

乙：但是，如果你真的「回到了過去」，你就不會有現在的記憶，即是沒有現在的資料。亦即是話，如果你真的「回到了過去」，你就不會知道那些是錯誤。你會再犯一次。

甲：為什麼「回到過去」時，我不能保存現在的記憶？

乙：如果「回到過去」後，你仍然有「現在」的記憶，那就不是「過去」，而是「現在」。

甲：如果「回到過去」就會失去現在的記憶，我就只會有當時的記憶。那樣，我「回到過去」後所經歷的，將不會跟原本的「過去」，有任何分別。那樣，「回到過去」和「沒有回到過去」，又有什麼分別呢？那樣，「回到過去」還有意思嗎？

乙：沒有分別，亦毫無意思。

你要記住，你現在的成熟，建基於以往的幼稚。

大部人的「後悔」，也是有害無益的，因為他們不斷企圖「回到過去」。結果連「現在」也一併失去。

甲：你的意思是，我要「活在當下」？

乙：「後悔」的真正意義，並不是「企圖回到過去」。
   
為一個錯誤而「後悔」，真正意義在於，對自己承諾，不會再犯那個錯誤。而「道歉」的真正用處，則是對別人承諾，不會再犯該個錯誤。

（對於一些犯了錯，既不懂後悔，亦不肯道歉的人，法律會施予懲罰。「懲罰」的真正意義，不在於「報復」。「懲罰」的真正意義，在於防止當事人繼續犯錯，以及防止其他人開始犯錯。）

對於一些不能避免的錯誤，你不用過份介懷。你只要避免所有，可以避免的錯誤，那就已經是，最理想的情況了。要「避免所有可以避免的錯誤」，唯有三個方法：

1. 不做風險過高的事情。

對於未知之事，如果依據常理，自己並不能承受，失敗的後果，例如會導致死亡，那就不要冒險。其他推理不能預測到的細節，你就緊守兩項原則：

2. 不要重犯自己的錯誤；

3. 不要重犯別人的錯誤。

如果你同時做到這三點，那就已經是，最理想的情況了。

— Me@2014.02.02

2014.02.02 Sunday (c) All rights reserved by ACHK