Placeholder Image

字幕列表 影片播放

  • All of the systems, beliefs, emotions, and experiences that we call life

  • are taking place on a tiny rock floating through space.

  • During our time here, we've discovered that our rock is one of the only

  • ones that has all the conditions necessary for sustaining life.

  • What we can't figure out for sure is what

  • spark brought together all the conditions that led us into existence.

  • This is WHAT IF, and here's what would happen if life didn't originate on Earth.

  • The earliest signs of life on Earth are molecules that are so complex

  • that some scientists say that it's unlikely they could've just popped up here.

  • So what if they formed somewhere else in space first, and then traveled to our planet?

  • How would they get here?

  • No one knows for sure how or where life on Earth started,

  • but there are plenty of conflicting scientific theories out there.

  • To better understand them, let's start with something that we can all agree on.

  • Earth is about 4.5 billion years old,

  • and some of the earliest fossils we've found are about 3.7 billion years old;

  • so we know that life started at some point in between,

  • and that's where things start to get complicated.

  • Some of the earliest evidence for life on Earth

  • contains a complex molecule called Ribonucleic acid, or RNA.

  • RNA is made up of thousands of smaller molecules

  • that are connected in a particular pattern,

  • and it was one of the driving forces behind life on Earth.

  • But the big question that divides the scientific community is: where did RNA come from?

  • Well, one option is that it came from outer space;

  • and no, we don't mean by way of advanced aliens planting their seeds,

  • although that would make for an interesting video...

  • Anyways, what we're talking about is called panspermia:

  • the idea that living organisms or genetic materials

  • could've been transported to Earth through some sort of natural phenomenon,

  • like an asteroid.

  • It might sound crazy, but it's actually plausible.

  • In 2012, Danish scientists found

  • the building blocks of RNA in a star system 400 light years away,

  • proving that the compounds necessary to forge life on Earth could be created in space.

  • But then how did they end up on Earth?

  • Well, there are two main theories, and both involve asteroids.

  • Number one: an asteroid could've brought these genetic materials to Earth

  • by crashing into its surface.

  • Or number two: an asteroid could've crashed into Mars,

  • hit a spot that contained microorganisms,

  • and sent the debris into space, which eventually found its way to Earth.

  • Both of these instances have happened before,

  • and research shows that some lifeforms

  • like bacteria and fungus could definitely survive the trip to our planet.

  • But some scientists remain skeptical;

  • choosing to believe that life on Earth was sparked by natural phenomena like lightning

  • or good old-fashioned chemical reactions.

  • So even if panspermia doesn't turn out to be our true origin story,

  • it doesn't mean that asteroids aren't spreading life to any of the other

  • billions of planets out there right now,

  • laying the ground work for future civilizations like ours.

  • But that's a topic for another WHAT IF.

All of the systems, beliefs, emotions, and experiences that we call life


單字即點即查 點擊單字可以查詢單字解釋

B1 中級

如果生命不是起源於地球呢? (What If Life Didn’t Originate on Earth?)

  • 3 0
    林宜悉 發佈於 2021 年 01 月 14 日