Are we the only living thing in the entire universe?
The observable universe is about 90,000,000,000 light years in diameter.
There are at least 1,000,000,000 galaxies
Each with 100,000,000,000 to 1,000,000,000,000 stars.
Recently, we’ve learned that planets are very common too
And there are probably trillions and trillions of habitable planets in the universe
Which means there should be lot of opportunities for life to develop and exist, right?
But where is it?
Shouldn’t the universe be teeming with spaceships?
Let’s take a step back.
Even if there are aliens civilisations in other galaxies,
there is no way we’ll ever know about them.
Basically, everything outside of our direct galactic neighborhood,
the so called, "Local Group" is pretty much out of our reach forever,
because of the expension of the universe.
Even if we had really fast spaceships
it would literally take billions of years to reach these places,
travelling throught the emptiest areas in the universe.
So, let’s focus on the Milky Way.
The Milky Way is our own galaxy,
it consists of up to 4 hundred billions stars.
That’s a lot of stars, roughly 10 thousands for every grain of sand on earth.
There are about 20 billions sun-like stars in the Milky Way
and estimates suggest that a fivth of them have an earth-sized planet in its habitable zone,
the area with conditions that enable life to exist.
If only 0.1% of those planets harbored life, there would be 1 million planets with life in the Milky Way.
But wait, there’s more.
The Milky Way is about 13 billion years old. In the beginning, it would not have been a good place for life
因为爆炸频发 但10至20亿年后 第一批居民诞生了
because things exploded a lot, but after 1 to 2 billion years, the first habitable planets were born.
地球仅40亿年 因而在过去的时间里 其它行星衍生出生命
Earth is only 4 billions years old, so there have probably been trillions of chances for life to develop
on other planets in the past.
只要有一个 高度发达到能进行超文明旅游 我们也早该注意到了
If only a single one of them had developed into a space travelling super civilization we would have noticed by now.
What would such a civilization look like?
There are 3 categories.
A Type 1 civilization would be able to access the whole energy available on its planet.
In case you are wondering, we are currently around 0.73 on the scale
and we should reach Type 1 sometime in the couple hundred of years.
Type II would be a civilization capable of harnessing all of the energy of its home star.
This would require some serious science fiction, but it is doable in principle.
Concepts like the Dyson sphere, a giant complex surrounding the Sun would be conceivable.
Type III is the civilization that basically controls its whole galaxy and its energy
an alien race this advanced would probably be godlike to us.
但是 我们起初为什么认为 能看到这样的外星文明
But why should we be able to see such an alien civilization in the first place?
If we were to build generations of spaceships that could sustain a population for around one thousand years
we could colonize the galaxy in 2 million years.
这听起来很长 但请记住 银河系很大
Sounds like a long time, but remember, the Milky Way is huge.
So, if it takes a couple of million years to colonize the entire galaxy
and there are possibly millions if not billions of planets that sustain life in the Milky Way
也可能存在其它的生命形式 他们比我们存在的时间长得多 那么
and these other life forms have had considerably more time than we’ve had, then
where are all the aliens?
This is the Fermi Paradox, and nobody has an answer to it
But we do have some ideas.
Let’s talk about filters.
A filter in this context represents a barrier that is really hard for life to overcome.
They come in various degrees of scary.
One: There are Great Filters and we’ve passed them.
Maybe it is way harder for complex life to develop than we think.
The process allowing life to begin hasn’t yet been completely figured out
and the conditions required may be really complicated.
也许在很久之前 宇宙对生命更加苛刻 物质冷却下来 使复杂的生命体有生存可能性 还是不久前才有的事
Maybe in the past the Universe was way more hostile, and only recently things have cooled down to make complex life possible
这也意味着 我们很独特 不是第一批文明 至少也是第一批中之一
This would also mean that we may be unique, or at least one of the first, if not the first civilization in the entire Universe.
Two: There are Great Filters and they are ahead of us.
This one would be really really bad.
也许同我们一样水平的生命体在宇宙中到处都是 但当他们到达某刻时就被摧毁了 这一刻我们还没达到
Maybe life on our level exists everywhere in the Universe but it gets destroyed when it reaches a certain point, a point that lies ahead of us.
例如 未来的恐怖科技 激活后 就立马毁灭了整个行星
For example, awesome future technology exists, but when activated, it destroys the planet.
The last words of every advanced civilization would be
"This new device will solve all of our problems once I push this button."
如果这成为事实 那么人类的存在比起起点 更接近终点
If this is true, then we are closer to the end than to the beginning of human existence.
或者 存在着第三种古老文明 它监控着宇宙
Or maybe there is an ancient Type III civilization that monitors the Universe
一旦有文明足够先进 可能超越它时 它就灭了它 只要一丢丢的功夫
and once a civilization is advanced enough it gets eliminated, in an instant.
Maybe there is something out there that it would be better not to discover.
There is no way for us to know.
One final thought: maybe we are alone.
Right now, we have no evidence that there’s any life besides us.
Nothing. The Universe appears to be empty and dead.
No one sending us messages no one answering our calls.
We may be completely alone, trapped on a tiny moist mud ball in an eternal Universe.
吓傻你了没？ 没骗你的话 你反应过激点也没关系
Does that thought scare you? If it does, you are having the correct emotional reaction.
如果我们让这个星球上的生命死去 也许整个星球就再也没有生命了 生命会永远消失
If we let life on this planet die, perhaps there would be no life left in the Universe. Life would be gone, maybe forever.
如果这种假设成立 我们应该到恒星上去探险试试 成为第一个三类文明
If this is the case, we just have to venture to the stars and become the first Type III civilization
to keep the delicate flame of life existing and to spread it until the Universe breathes its final breath
and vanishes into oblivion.
The Universe is too beautiful not to be experienced by someone.
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