大家有無咩關於physics嘅問題但又無地方問

係互吸
個力冇大到可以改變左行星個軌跡
所以只會係ellipse orbit

即係行聲會圍住恆星公轉唔關恆星嘅引力事？

因為個大質量黑洞其實體積好細
而且佢附近有accretion disk射x ray
好難先睇到個黑洞

經典力學上嚟講兩舊嘢有mass佢哋之間就會有引力
modern physics上科學家嘗試用一種叫gravitons嘅粒子去解釋重力機制，不過暫時仲未成功搵到gravitons

只要有mass 就會有引力
至於係圍住黎轉/衝埋去/經過就走就睇本身個速度同佢地本身個mass既比例

關事
其實可以睇下Newton's law of gravitation, 假設而家講地球同太陽，咁m1同m2就係地球同太陽嘅重量，對地球同太陽嚟講佢地係互相吸引，大家食嘅重力都係咁多。但係點解係地球圍住太陽轉，呢個就關個質心事，簡單嚟講就係因為太陽重太多，地球拉唔郁佢。


質心
https://zh.wikipedia.org/wiki/%E8%B3%AA%E5%BF%83

個人嚟講係UG E&M, 啲maths令人絕望

可摸耳唔好浸左時空扭曲...

A value assigned to a system in thermodynamic equilibrium, such that when two systems, each in thermodynamic equilibrium, are put in thermal contact, heat flows from the higher temperature system to the lower temperature system (ie when the two systems are later no longer in thermal contact and each reach thermodynamic equilibrium again, the lower temperature system will have a higher temperature than before, and the higher temperature system will have a lower temperature than before)

*漏

點樣將rectangular Pipe/ Duct屈落Bernoulli's equation計flow/ heading

thermo d 定義好似無講過野咁

佢陳述左system under thermodynamics equilibrium 上存在一個well-order 非常重要

我覺得heat flow from the higher temperature system to the lower temperature system可以係second law講

Zeroth law 只講: If two systems, A and B, are separately in equilibrium with a third system C, then they are also in equilibrium with one another.
由le句statement得出可以定義"temperature"

不過唔同派physicist可能會有唔同approach去定義3條thermo law, 我覺得下面個approach好似好d

https://ocw.mit.edu/courses/physics/8-333-statistical-mechanics-i-statistical-mechanics-of-particles-fall-2013/lecture-notes/MIT8_333F13_Lec1.pdf

https://ocw.mit.edu/courses/physics/8-333-statistical-mechanics-i-statistical-mechanics-of-particles-fall-2013/lecture-notes/MIT8_333F13_Lec2.pdf

筆誤 係total order 唔係well order

Derivative of energy with respect to entropy

首先要講返：我講緊temperature 無講緊係zeroth定second黎
要討論temperature唔一定只係討論zeroth

然後講返單單用zeroth去定義溫度
Zeroth講緊thermodynamic equilibrium可以form equivalence class
每個class可以assign一個數比佢 - 廢話 無視equivalence class我都照樣可以arbitrarily assign啲數字比system
唔講個數字仲有咩其他特點 根本provide唔到一個useful temperature definition出黎

用equivalence class去assign temperature 係可以capture到equivalence relation 但只capture equivalence relation並唔一定useful 畢竟如果個system變少少 個temperature就唔連續咁跳黎跳去 點撚用呢個temperature

所以我覺得at least要capture埋total order同continuous先可以稱得上useful
當然可以話 喂咁唔夠useful喎 咁樣既temperature唔可以用黎具體計thermal efficiency喎
我會覺得呢個係scale問題 因為capture左total order之後 可以用strictly monotonic function去convert 做kelvin scale

所以其實我唔係咁中意用「可以建立溫度計」去描述zeroth 因為講到好似temperature唯一重要既係equivalence relation咁

係我離題
題外話，有人玩d bounded phase space 出 negative temperature咁temperature同order就應該唔係monotonic function?
利伸唔熟

離心力係咪唔存在

e&m 同multivariable calculus 搞到想放棄physics

真？

如果 entanglement 係spontaneous 既話 wormhole 係一個plausible 既hypothesis 黎架喎 any speed > photon speed 係要用到curved space time 黎solve?

技術上可以用negative beta做temperature既