了解宇宙是如何运行的（2010）

How the Universe Works S08E05

Part 8 Jan. 30, 2022, 2:58 p.m.

history of the universe.
在微观层面上的物理定律
On the microscopic level,
the laws of physics
是时间反转无变化
are time reversal invariant.
所以这个时间旅行的概念
And so this idea of time travel
actually appears
实际上出现在量子领域，至少在数学计算中是这样的
in the quantum realm at least in
the mathematical calculations.
如果量子领域的时间之箭能够在现实世界中
Narrator: If the quantum realm's
arrow of time runs forward
来回穿梭
and backwards in the real world,
量子粒子可以为斯蒂芬·霍金的派对
quantum particles
could offer a new route
提供一条新的路线
to stephen hawking's party.
但这可能不是一段舒适的旅程
But it might not be
a comfortable ride.
普莱特:如果量子时间旅行的想法是真的
Plait: If this idea of
quantum time travel is true,
那么你可以去史蒂芬·霍金的时间旅行派对
then you could go to
stephen hawking's
但你必须以一次一个亚原子粒子的方式
time travel party,
but you'd have to do it
去参加这个派对
one subatomic particle
at a time.
人体内的粒子
Narrator: There are more
particles in the human body
比地球上的沙粒还多
than grains of sand
on the earth.
所以把一个人安全地分解成亚原子粒子
So safely deconstructing someone
into subatomic particles
然后再重建它们，这是不可能的
and then rebuilding them
probably isn't going to happen.
但是量子粒子能为
But could quantum particles
不同时间旅行铺平道路吗？
pave the way to a different
kind of time travel?
我们每天都用量子粒子发送信息
We send information using
quantum particles every day.
电子在计算机内部携带信♥号♥♥
Electrons carry signals
inside your computer.
而光子将手♥机♥信♥号♥♥送入太空并带回
And photons carry cellphone
signals into space and back.
我们能否将信息编码到一组粒子中
Could we encode information
on to a set of particles
然后将它们发送回过去，也许是我们年轻时的自己？
and send them back in time,
perhaps to our younger selves?
如果你能及时发送信息
If you can just send
information back in time,
你肯定已经非常非常富有了
that could already make you
very, very rich.
只需在下周，把股市价格发回给我
Just go to next week,
send back stock market prices,
让我知道我们有一些事情要谈
and let me know we have
some stuff to talk about.
把信息传送到过去来改变现在
Narrator: Sending information
to the past to alter the present
是一个诱人的想法
is a tantalizing idea.
也许我们可以在2009年邀请科学家
Perhaps we could send invites
for professor hawking's party
参加霍金教授的派对
to scientists back in 2009.
但即使这是可能的，我们可能永远也无法知道
But even if that's possible,
we may never know
他们是否收到了信息
if they even got the message.
量子力学对此进行了逆转
Quantum mechanics
throws a monkey wrench into this
并表明也许过去可以分支成
and suggests that maybe the past
can branch
许多不同的未来
into many different futures.
普莱特:如果你有两个
Plait: If you have
an interaction between
亚原子粒子之间的相互作用
two subatomic particles
and there's a probability
有可能它会朝一个方向也有可能它会朝
it will go one way
and a probability it'll go
另一个方向，当我们观察它，它似乎只朝一个方向
another way, to us observing it,
it only seems to go one way,
但量子力学的解释说
but there's this interpretation
of quantum mechanics that says
[回音]它们都会发生
[echoing] they both happen.
你现在创造了两个宇宙
You've now created
two universes.
时间线分♥裂♥了
The timeline has split.
在量子世界里，发送一个粒子
Narrator: In the quantum world,
sending a particle,
邀请一个聚会，甚至是一辆德劳瑞恩车回到过去
invitations to a party,
or even a delorean back in time
都会创造一个新的时间线
could create a new timeline.
在新的时间轴里，霍金的派对
In the new timeline,
hawking's party
可能挤满了派对常客
might have been packed
with party goers,
但我们和史蒂芬·霍金
but we aren't part
of that timeline
都不在这个时间轴里
and neither is
our stephen hawking.
你不能通过时间旅行回到你自己的宇宙
You're not time travelling
back into your own universe
去改变事物
and changing things.
在那个时间点，你正在穿越到另一个宇宙
You're travelling to another
universe at that point of time
并从那里开始改变事物
and changing things
from there on forward.
如果你那时改变了什么也没关系
And it doesn't matter
if you change things then
因为在那个宇宙中，你出生的晚
because in that universe,
you don't get born later
不会回到过去去改变什么
to go back in time
to change things.
这发生在另一个宇宙
That happened
in another universe.
我知道这些东西很难理解
I know this stuff
is hard to understand.
也很难解释
It's hard to explain, too.
也许如果有无数个宇宙
Maybe if there are an infinite
number of universes,
就会有另一个版本的我能更好地理解它
there's an alternate version of
me that understands it better.
我希望他有更多的头发
I hope he has more hair.
现在，时间旅行还只是科幻小说
Narrator: For now, time travel
is still science fiction.
所以在我个人看来，没有东西会在时间上倒♥退♥
So in my personal view, nothing
is going to go backward in time,
粒子，信息，诸如此类的东西
particles, information,
anything like that.
有时候你会听到一些关于时间倒♥退♥的报道
Sometimes you hear reports of
something going backward in time
或者是一些未完成的事情
or being undone or whatever.
这其实只不过是倒放电影的
It's really nothing
more than a fancy version
花哨版本
of playing a movie backward.
但是也许有一天，科学家们会发现
Narrator: But perhaps someday
scientists will discover
一种奇异物质的来源来支撑虫洞
a source of exotic matter
to prop open a wormhole
或者找到一种方法来弯曲时空
or find a way to bend
spacetime back on itself.
你知道，永远不要说永远，因为我们现在认为的科学
You know, never say never
because what we consider science
在一个世纪前会被认为是科幻小说
now would have been considered
science fiction
或精神病以及疯子
or the lunatics
of a madman a century ago.
但我还是抱有一点希望
But I'm holding out
a little bit of hope.
因为非常聪明的人试图证明
Because very smart people
have tried to prove
这实际上是不可能的，但失败了
that it's actually impossible
and failed.
永远不要说不可能
You should never say never.
在这个过程中，也许我们会更多地了解
Narrator: And along the way,
maybe we'll learn a bit more
宇宙是如何运行的
about how the universe works.
布洛克:时间旅行当然更像是科幻小说
Bullock: Time travel is
definitely more science fiction
而不是科学事实，但是思考时间旅行
than science fact, but thinking
about time travel
并试图理解为什么它也许不可能是真的很有趣
and trying to understand
why it might not be possible
而且可以教会我们很多
is really interesting
and can teach us a lot about
关于宇宙本质的东西
the nature of our universe.
泰格马克:思考这个问题也很有趣
Tegmark: It's also really
fascinating to think about this
因为它迫使我们去解决
because it forces us to take on
some of the toughest
物理学中一些最难回答的问题
unanswered questions
in all of physics
并最终可能导致我们对现实的本质
and will ultimately probably