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当不可移动物体遇上不可阻挡力量

Immovable Object vs. Unstoppable Force - Which Wins?

“不可移动物体”遇上“不可阻挡力量”会发生什么?
What happens if an immovableobject meets an unstoppable force?
这个问题在网上很火
Is a popular question on the internet.
当然了 相对论明确地告诉我们
Of course, relativity clearly tells us
根本就没有“不可移动物体”的存在
that there is no such thing as an immovable object
原因如下
– here’s why:
如果你认为某样东西是不可移动物体或者干脆拿你家的房子或者地球为例
If you pick any supposedly immovable object, or just something like your house
我都能让它动起来
or the earth, I can make it move.
只需要让它的一个参照物动起来
All I need to do is start to move relative to it,
比如我乘一架火箭升空
for example I might ride a rocket,
那么这时从我的角度来看 我没有动
and suddenly from my perspective, I’m not moving and the
是外面的地球在动
earth sails by outside.
物理定律的适用范围很广
The laws of physics make no preference
从不会只限于一种惯性参考系
for inertial frame of reference,
这时从我的角度看我确实没动
so from my perspective here, I do not stir,
所以说不可移动物体也是可以动的
and yet it’s clear: the immovable object moves!
因而在相对论里 “不可移动物体”不可能存在
So because of relativity,”immovable objects”cannot be. But what I think people normally
人们通常说的“不可移动物体”
MEAN by”immovable object” is something
我认为实际上是指施以推力而不动的物体
that if it’s not moving, you can’t make it start
所以“不可移动物体”实际上是“加速度不变物体”
moving by Pushing on it. So, not an immovableobject, but an”un-acceleratable” one.
根据牛顿第二定律
Using Newton’s second law, we know that an
物体的加速度等于
object’s acceleration is equal to the total force
该物体收到的合力F除以其质量m
on it divided by its mass ( though you’ve
“加速度不变物体”可以被看作是质量无穷大的物体
probably seen this as F=ma). So an”un-acceleratable”object would be an object with infinite mass;
因而无论其受到的合力F有多大
an object so massive that no matter how big the total force F is,
除以无穷大的质量m之后
when you divide F by
加速度a总会是0
m you always get zero.
当然 我们刚才也说了
Of course, as we’ve said,
一个物体加速度不变
not being able to accelerate an object doesn’t necessarily mean
并不代表它不可移动
that the object isn’t moving –
只是说你无法直接改变它的速度
it just means that you can’t directly change its speed – if
假如它没有动 那就一直不会动
it’s not moving, then it’ll stay not moving.
假如它以100英里的时速运动
And if it’s moving at 100 miles an hour, then
那它就会一直以100英里的时速运动
it’ll stay moving at 100 miles per hour. So,
接下来我们来看看“不可阻挡力量”
what about an unstoppable force? Well,
实际上自然界所有的基本力
all the fundamental forces in nature are actually
都是由粒子(如光子 胶子 引力子)
caused by particles ( like photons or gluons or gravitons )
与其他物体发生碰撞
that interact with an object
使得其动量发生改变引起的
and change its momentum –
阻挡这种力量的唯一方法就是根本不和粒子接触
the only way to NOT be affected by a force is to not interact
(就像电子不和胶子发生碰撞一样
with it at all ( like how electrons don’t interact
这也正是为什么电子和胶子不能用于生产核能的原因)
with gluons so they aren’t subject to the strong nuclear force).
即使光线是一种“不可阻挡力量”
Even light itself is an unstoppable force –
每一个光子
every photon that hits
都在一点点地改变你身体的动量
your body changes your momentum a tiny little bit,
而你对此无计可施
and there’s nothing you can do about
除非你完全不见光或者干脆变成透明的
it other than avoid light altogether or becometransparent.
所以其实所有的力都已经是“不可阻挡力量”了
So all forces are already unstoppable
但我想
but my impression is
“不可阻挡力量”并非真的指电磁力或万有引力一样的力
that the phrase” unstoppable force” isn’t really meant to imply anything
而是指那些不管怎样
about”forces” like electromagnetism or gravity,but rather, something that you cannot stop
你都无法让它停下来的力
from barreling down on you.
也就是指速度无法被推力改变的物体
That is, an objectwhose velocity cannot be changed by pushing
所以
on it. So,
如果我们说物体受到不可阻挡的力
IF by an unstoppable force we
也就是说物体在以不可改变的速度运动
mean an object moving at a speed that can never be changed,
或者说物体的加速度总会是0
then that means the object can not accelerate –
等一下 这个听起来有点耳熟
but wait a second, this sounds familiar!
回忆一下我们之前讲过的
Recalling what we learned earlier,
“不可阻挡力量”一定是“加速度不变物体”
an unstoppable force must be an un-acceleratable object!
那也就是说“不可阻挡力量”和“不可移动物体”本质上是相同的
And that means that an”unstoppableforce” and an”immovable object” are really
不过是采用了不同的参考系而已
just the same, viewed from different referenceframes! Now,
而因为无穷大的质量对应着无限的能量
since infinite mass requires infinite energy,
在已知的范畴里
we don’t know of anything
宇宙中根本不会有这样的物体
in the universe that behaves like this, not the least because
因为它会自动成为一个黑洞
it would automatically be a black
这个黑洞十分之大
hole so big that everything in the universe would
大到吞噬一切
already be inside of it.
但是现在我们暂且忽略万有引力的存在
But what if weignored gravity and imagined there WERE an
想象存在一个加速度不变物体
un-acceleratable object? Well,
那么就会有无限的免费能量出现
first it would be a source of infinite free power and would
我们就能
allow us to live
违背热力学定律 无忧无虑地活着
in a 100 % happy utopian society and break the second law of thermodynamics
并且很有可能打开时光旅行的大门(你可以做任何想做的)
and probably create portals and time travel,too (you can do a lot with infinite energy).
但更重要的是
But more importantly,
假如两个具有无穷大质量的无加速度物体相向运动
if two of these infinitely massive un-acceleratable objects were moving
并且发生碰撞
towards each other and collided,
而从定义来看
then since by definition it’s not possible for the velocity
两个物体的速度都不会改变
of either of them to change,
唯一的可能性就是它们会穿过对方
the only possibility is that they must pass right through each
互相不产生任何影响
other with no effect on each other at all.

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视频概述

从两个角度简述了物理中的一个概念,需要一定物理基础

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视频来源

https://www.youtube.com/watch?v=9eKc5kgPVrA

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