Home
Вход
Регистрация
Обучающий контент
Loading...
50 Years Later & Scientists Still Don't Know Why These Exist - Video học tiếng Anh
Практика аудирования
Практика аудирования
/
Video
/
SciShow
/
50 Years Later & Scientists Still Don't Know Why These Exist
50 Years Later & Scientists Still Don't Know Why These Exist
Выберите режим обучения:
Посмотреть субтитры
Выбрать слово
Переписать слово
Highlight:
3000 Oxford Words
4000 IELTS Words
5000 Oxford Words
3000 Common Words
1000 TOEIC Words
5000 TOEFL Words
Субтитры (112)
0:00
If you fly over the coastal dune belt of the Namib Desert in southwest Africa,
0:04
for hundreds of kilometers you’ll see almost nothing but sand.
0:08
But eventually, you’ll come across these: hundreds of thousands of bare circles surrounded by grass.
0:14
Like a tile mosaic in the middle of the desert.
0:16
It’s almost like someone, or some thing, made this elaborate pattern.
0:21
But what?
0:22
For more than 50 years, scientists have been trying to figure that out.
0:26
It’s probably not a mythical dragon with poison breath —
0:29
a story possibly cooked up by local tour guides and it’s definitely not aliens!
0:34
But how can a design this massive and precise show up without anyone…or anything…in charge?
0:41
And why are we suddenly finding more of them elsewhere?
0:45
[♪ INTRO]
0:48
Scientists have seen bare patches in grass before,
0:51
caused by termite mounds, gas leaks, things like that.
0:54
But nothing like the Namib’s fairy circles.
0:57
They only seem to form in this one sliver of
1:00
desert that gets between 50 and 100 millimeters of rain a year.
1:04
And along this sliver, hundreds of thousands of circles…ranging in size from 2 to 35 meters wide…
1:11
line up in a suspiciously organized pattern where each circle has about six neighbors.
1:18
Researchers started looking for scientific explanations back in the 1970s,
1:22
but for the first few decades, they came up empty.
1:25
One guy suggested that fairy circles were old, eroded termite mounds.
1:30
Another proposed they were caused by poisonous plants
1:32
that had died and released their poison into the soil.
1:35
Still more wondered if gases rising up from the Earth were killing off the grass.
1:40
But based on all the gathered evidence, there was no consensus for any of these ideas.
1:45
So scientists eventually came up with some fresh ones,
1:48
and by the 2010s, the search for an explanation became a full-on debate.
1:53
Science beef!
1:54
Science beef!
1:55
In 2013, one researcher thought he’d cracked it.
1:58
After studying hundreds of fairy circles, he found one thing they all had in common: sand termites.
2:04
These tiny insects build elaborate underground nests, and as they tunnel through the ground,
2:09
they eat the roots of freshly sprouted grasses.
2:12
By killing plants that would otherwise suck
2:14
up all the groundwater, termites create their own personal oasis.
2:18
The researcher also proposed they consistently munch on the grass roots
2:23
at the edge of the circle, widening the whole shape slowly over time.
2:27
Eventually, these termites run into neighboring nests, all doing the same thing.
2:33
And instead of battling, or merging into one megacolony, they all just stop expanding…leaving
2:40
a kind of Demilitarized Zone between them, and capping how big each circle can get.
2:45
So mystery solved, right?
2:47
Well, another camp of researchers wasn’t so sure.
2:50
Mainly because they didn’t find termite nests at all when they dug up some of these circles.
2:55
They mostly just found sand.
2:57
Plus, even if there were termites burrowed somewhere in there,
3:00
this camp of researchers just didn’t see why termites would only create
3:04
fairy circles in this narrow strip of the Namib Desert, since they lived all over it.
3:10
So instead, they put a new idea out there:
3:12
fairy circles arise naturally as plants compete for water.
3:16
The bare patches represent the spots where competition is the highest.
3:20
There’s not enough water to go around, and the grasses die off.
3:23
But wherever the grasses die, water can start pooling underground without roots sucking it up.
3:29
Meaning, eventually, a new reservoir can form…and maybe even attracts critters like
3:34
termites who also need some amount of water to survive.
3:37
This hypothesis explains both how you could get a whole field of fairy circles evenly spaced across
3:43
the desert, as well as why we only see them in this narrow strip of desert: there’s just
3:48
the right amount of rainfall to both form the reservoirs and force the grasses to compete.
3:54
But it also has its problems.
3:56
For instance, scientists in the termite camp pointed out the
3:59
grasses seem to die off during times when the soil is relatively moist,
4:04
not when it’s dry and competition for water would be the highest.
4:07
So which idea do you like better?
4:09
Termites or Plants?
4:10
Go ahead and think about it while we show you this ad to help keep the lights on:
4:14
This SciShow video is supported by DeleteMe, the hands-free subscription service that removes
4:20
your personal information from hundreds of data broker and people search sites.
4:25
DeleteMe is trusted by medical providers, judges,
4:28
podcasts hosts, and our executive producer, Nicole!
4:31
She signed up this year and said they’ve already reviewed over 900 records and begun removing them.
4:37
And by “they,” I mean real people available for custom requests and help when you need it.
4:43
They use their own tech and don’t outsource to third parties, so your data stays safe.
4:48
To sign up for their service, use the QR code on screen or go
4:52
to joindeleteme.com/SCISHOW and use the promo code SCISHOW at checkout.
4:59
You’ll get 20% off DeleteMe US consumer plans.
5:05
So researchers sparred over these ideas for years.
5:08
And then in 2017, one team wandered up to the controversy like, “Hey,
5:13
what if everyone’s kind of right?”
5:15
First, the team ran some simulations of termite colony interactions.
5:19
What happens when two expanding nests finally encroach on each other’s territory?
5:24
According to these simulations, the bigger colony usually wins and engulfs the smaller one.
5:30
But when two colonies are about the same size, they can hold out indefinitely,
5:35
and create that aforementioned Demilitarized Zone.
5:38
The end result is circles that look a whole lot like real-life fairy circles,
5:43
with tall grasses growing in the “I’m not touching you” zones where no termites are foraging.
5:49
While that sure sounds like a win for Team Termite, the group also found that
5:54
to really match Namib’s grass pattern, you need to factor in water competition, too.
5:59
That’s because all of the clumps of grass between the fairy circles also look a lot
6:03
like they do in a simulation of plants competing for water.
6:07
Alas, their 2017 paper has still not sealed the deal.
6:10
As of at least 2023, the termite team and the water competition team were still at it,
6:16
publishing contradicting papers, still trying to end the debate once and for all.
6:21
In the meantime, a new set of fairy circles entered the fray, 10,000 kilometers away.
6:26
In 2016, researchers reported on what appeared to be fairy circles in the Australian outback.
6:31
And despite forming on a completely different continent, they look almost
6:36
identical to the Namibian ones.
6:38
Suddenly, it seemed like fairy circles might not be so rare and special after all.
6:43
Then in 2023, a survey of the whole globe found hundreds of
6:48
patterns that looked like fairy circles spanning Africa, Asia, and Australia.
6:53
But while they all seem to show up in dry places, they have very different climates and ecosystems.
6:59
This suggests there’s no one cause for all of them.
7:02
So, the mystery of fairy circles is maybe even less solved than ever.
7:07
But here’s what we do know:
7:08
Whatever’s causing them, it’s probably a survival strategy: some way for
7:13
plants and animals to create a mini, stable ecosystem in the midst of a much harsher one.
7:18
And these tiny actions… termites munching through roots,
7:22
plants competing for water… get repeated over an entire landscape.
7:26
In the end, their simple mission creates a massive pattern that
7:30
almost looks like a deliberate work of art.
7:33
So while scientists argue amongst themselves, I’m just gonna take in nature’s beauty…and think
7:38
of what kind of pattern I’d draw if I were a dragon with poison breath… or an alien.
7:45
[♪ OUTRO]
