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明天賞雪記
2019/02/06 13:52:02瀏覽2563|回應39|推薦35

最近入夜轉涼,老婆晚飯後跟女友在 line 上聊天,爾後跟我說:「阿香說 680 沿途都是雪,明天你要陪我去賞雪」。

我想 680 出家門就到,不過就條高速公路,每天都在開,是要怎樣「賞雪」?於是問說雪要怎樣賞。她說,阿就慢慢開車,靜靜欣賞,有時停下來看啊。

我還是有點衲悶,問說,阿以前上大山滑雪不是滑了十幾年,還賞不夠嗎,現在要開車去公路賞雪?她說那是滑雪,和賞雪不一樣。

不敢再問,反正明天陪她開車「賞雪」就對。

老婆自有她的邏輯。就像晚餐前她問:「我有新鮮大蘿蔔可以燉湯。你想喝海帶蘿蔔湯、藥膳排骨湯、或是酸菜白肉湯」?我說藥膳排骨,她說:「Ok 好,我煮海帶蘿蔔排骨湯。等做好後你端半鍋過去對門,冬天喝熱湯最好了」。

既然朕意已決,還幹嘛問我?女人真是奇怪的動物。懷疑

( 在地生活北美 )
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【無★言】家喻戶曉的中國人 — 包青天
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2019/02/07 18:57

「既然朕意已決還幹嘛問我女人真是奇怪的動物。」

這沒什麼,只是隨時提醒一件事:「家事方面我是老大」,如此而已。

哈哈哈

GolfNut — 無心的邂逅(GolfNut) 於 2019-02-07 19:07 回覆:
無兄顯然西瓜偎大邊。Me no contest。

GolfNut — 無心的邂逅
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牛頓造訪,你不可能閱完
2019/02/07 17:10

如下

GolfNut — 無心的邂逅(GolfNut) 於 2019-02-08 11:18 回覆:

On the Origin of Gravity and the Laws of Newton

Erik Verlinde1

Institute for Theoretical Physics University of Amsterdam Valckenierstraat 65
1018 XE, Amsterdam
The Netherlands

Abstract

Starting from first principles and general assumptions Newton’s law of grav- itation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of ma- terial bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton’s law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.

e.p.verlinde@uva.nl

page1image8160

arXiv:1001.0785v1 [hep-th] 6 Jan 2010

1 Introduction

Of all forces of Nature gravity is clearly the most universal. Gravity influences and is influenced by everything that carries an energy, and is intimately connected with the structure of space-time. The universal nature of gravity is also demonstrated by the fact that its basic equations closely resemble the laws of thermodynamics and hydrodynamics2. So far, there has not been a clear explanation for this resemblance.

Gravity dominates at large distances, but is very weak at small scales. In fact, its basic laws have only been tested up to distances of the order of a millimeter. Gravity is also considerably harder to combine with quantum mechanics than all the other forces. The quest for unification of gravity with these other forces of Nature, at a microscopic level, may therefore not be the right approach. It is known to lead to many problems, paradoxes and puzzles. String theory has to a certain extent solved some of these, but not all. And we still have to figure out what the string theoretic solution teaches us.

Many physicists believe that gravity, and space-time geometry are emergent. Also string theory and its related developments have given several indications in this direc- tion. Particularly important clues come from the AdS/CFT, or more generally, the open/closed string correspondence. This correspondence leads to a duality between theories that contain gravity and those that don’t. It therfore provides evidence for the fact that gravity can emerge from a microscopic description that doesn’t know about its existence.

The universality of gravity suggests that its emergence should be understood from general principles that are independent of the specific details of the underlying micro- scopic theory. In this paper we will argue that the central notion needed to derive gravity is information. More precisely, it is the amount of information associated with matter and its location, in whatever form the microscopic theory likes to have it, mea- sured in terms of entropy. Changes in this entropy when matter is displaced leads to an entropic force, which as we will show takes the form of gravity. Its origin therefore lies in the tendency of the microscopic theory to maximize its entropy.

The most important assumption will be that the information associated with a part of space obeys the holographic principle [8, 9]. The strongest supporting evidence for the holographic principle comes from black hole physics [1, 3] and the AdS/CFT correspondence [10]. These theoretical developments indicate that at least part of the microscopic degrees of freedom can be represented holographically either on the boundary of space-time or on horizons.

The concept of holography appears to be much more general, however. For instance, in the AdS/CFT correspondence one can move the boundary inwards by exploiting a holographic version of the renormalization group. Similarly, in black hole physics there exist ideas that the information can be stored on stretched horizons. Furthermore, by thinking about accelerated observers, one can in principle locate holographic screens

2An incomplete list of references includes [1, 2, 3, 4, 5, 6, 7] 2

page2image25928

anywhere in space. In all these cases the emergence of the holographic direction is accompanied by redshifts, and related to some coarse graining procedure. If all these combined ideas are correct there should exist a general framework that describes how space emerges together with gravity.

Usually holography is studied in relativistic contexts. However, the gravitational force is also present in our daily non-relativistic world. The origin of gravity, whatever it is, should therefore also naturally explain why this force appears the way it does, and obeys Newton law of gravitation. In fact, when space is emergent, also the other laws of Newton have to be re-derived, because standard concepts like position, velocity, acceleration, mass and force are far from obvious. Hence, in such a setting the laws of mechanics have to appear alongside with space itself. Even a basic concept like inertia is not given, and needs to be explained again.

In this paper we present a holographic scenario for the emergence of space and address the origins of gravity and inertia, which are connected by the equivalence principle. Starting from first principles, using only space independent concepts like energy, entropy and temperature, it is shown that Newton’s laws appear naturally and practically unavoidably. Gravity is explained as an entropic force caused by a change in the amount of information associated with the positions of bodies of matter.

A crucial ingredient is that only a finite number of degrees of freedom are associated with a given spatial volume, as dictated by the holographic principle. The energy, that is equivalent to the matter, is distributed evenly over the degrees of freedom, and thus leads to a temperature. The product of the temperature and the change in entropy due to the displacement of matter is shown to be equal to the work done by the gravitational force. In this way Newton’s law of gravity emerges in a surprisingly simple fashion.

The holographic principle has not been easy to extract from the laws of Newton and Einstein, and is deeply hidden within them. Conversely, starting from holography, we find that these well known laws come out directly and unavoidably. By reversing the logic that lead people from the laws of gravity to holography, we will obtain a much sharper and even simpler picture of what gravity is. For instance, it clarifies why gravity allows an action at a distance even when there in no mediating force field.

The presented ideas are consistent with our knowledge of string theory, but if correct they should have important implications for this theory as well. In particular, the description of gravity as being due to the exchange of closed strings can no longer be valid. In fact, it appears that strings have to be emergent too.

We start in section 2 with an exposition of the concept of entropic force. Section 3 illustrates the main heuristic argument in a simple non relativistic setting. Its gen- eralization to arbitrary matter distributions is explained in section 4. In section 5 we extend these results to the relativistic case, and derive the Einstein equations. The conclusions are presented in section 7. 


GolfNut — 無心的邂逅
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新春心願
2019/02/07 15:51

年底前把西班牙文搞個通透,目標是:一、絕不花錢,二、對話無礙,三、說聽讀寫報紙程度。

日文只在日本通用,俄文只在俄國通用,法文只在法國通用,德文只在德國通用,拉美裔的共同語文全球多處通用 no?

現在星期三半夜 11:50。明天一早醒來開始。我一定要能出入中南美、西班牙、葡萄牙、義大利如入無人之境。Just watch me。

說講人家的語文不止是能力,更是一種尊重。西語?我想很久了。


GolfNut — 無心的邂逅
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新春心願
2019/02/07 11:01

老婆不是很喜歡我「殘而不廢」的志願,所以僅管每天一早拿根掃帚把前院打掃得一乾二淨她好像也沒多開心,我想她是希望我回到二三十歲,不曉得掃地爲何物的從前。

大過年新春心願:努力復健把換過的膝蓋弄好,不能滑雪至少可以陪她開車賞雪,不行跑步起碼走路正常。

我也是這輩子第一次啊!從沒開過刀的人哪裡會知道?個人的感覺是人工關節 seems to be working,只是因爲「外物」所以有點費勁。

Me not afraid。


ellen chou 雨僧 我弟小五
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2019/02/07 06:47
求其放心。
GolfNut — 無心的邂逅(GolfNut) 於 2019-02-08 02:33 回覆:
跟我交往吧

GolfNut — 無心的邂逅
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Nostalgia
2019/02/07 06:40

魚子醬的鄉愁:


GolfNut — 無心的邂逅
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高家小國寡民,每每船到橋頭自然直
2019/02/06 17:21

爲什麼 2016 年間子夜班機降落在巴賽隆納後有人來接到酒店?為什麼次日清晨有人車接到巴賽隆納 downtown?爲什麼再隔一天又有人前來接上港口大船、然後暢遊地中海?

我覺得自已好像一個笨蛋,沒怎樣人生旅途就順暢無比。魚子醬的運籌帷幄不是任何蘋果工程師可以比擬的。

敬禮!


GolfNut — 無心的邂逅
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Corazon 就是心
2019/02/06 16:26

Corazon 是什麼?

最近聽很多拉丁音樂,一直聽到 corazon 這字。趁買啤酒之便問顯然拉美裔的結帳員:「Corazon 是什麼?爲什麼我在西班牙樂曲裡一直聽到這個字」?

他不假思索告訴我說:「Corazon 就是心」。我眼淚差點沒掉下來。

不知道爲什麼,只曉得自己超不中用。

Corazon Espinado:


GolfNut — 無心的邂逅
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分崩離析、妻離子散,這個家如此這般也過來了
2019/02/06 14:49

講起滑雪...以前因爲「貪滑」,嫌他們三個慢,和我雪道又不一,每每自顧自在大山上奔放,心想老婆和兒女們在一起有伴沒關係。

後來才知道女兒、兒子也沒怎麼和魚子醬在一起,小孩子一溜煙就滑到不見人影,老婆每每自己一個人上上下下,沒有人知道她在哪裡。

後來更得知小五的女兒也沒怎麼照顧小二的弟弟,自己上山下海,放八歲的高小衲「如入無人之境」。一家四口分崩離析,真正妻離子散。

無論如何天黑前總有辦法一家四口(喜慶)團圓,只有一次高小衲 ended up 在醫務室(左小腿螺旋狀骨折),另一次小女入夜後才從山頂滑下 base,急哭了魚子醬都。

有人說美國家庭放任子女獨立冒險、立國精神云云,me tell you,很多時候是兒女別無選擇,更多時候是家長搞不清楚...

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