Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

science.org

Post reply on HN
Print view View original

11–20 of 102 posts

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#11

Post by desdenova »

gonzo41 wrote: post #9
ge96 wrote: post #2

Everytime I see these I think of lost gold.

Every time i see these I think about Spanish explorers who brought small pox over and caused these cities to collapse, only to return to Spain telling stories of jungle cities. Only to have the fleets turn up to dense jungle years later and fine nothing. But yeah, I also think about lost treasure and Indian Jones a lot with these stories.

Some of those ancient cities disappeared a lot earlier than Spain even existed, though.

People likely abandoned them for some unknown reason and moved to other locations, where they'd eventually get wiped out by the Spanish.

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#12

Post by defrost »

TulliusCicero wrote: post #6

How do the LIDARs work for this kind of thing? I always imagined that the light used wouldn't be able to penetrate objects that are opaque in the visible light spectrum.

If sunlight can reach the forest floor then so can LIDAR.

An airframe with a LIDAR device scatter shots a medium angle "spotlight" of pulses at high frequency downwards within an arc area of angles (straight down, a bit to the left, a bit to the right, a bit forward, etc.)

Of the tens of thousands of 'RAW' data points many reflect from top canopy leaf cover, many penetrate further, a lesser number reach the ground.

All the raw points are pipeline processed and the floor() of penetration is extracted from the fuzzy cloud that represents the canopy as a whole.

Ancient banks, levels, roads, et al show up where not eroded as per the image in the article.

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#13

Post by brabel »

desdenova wrote: post #11
gonzo41 wrote: post #9

Earlier quoted context omitted.

Every time i see these I think about Spanish explorers who brought small pox over and caused these cities to collapse, only to return to Spain telling stories of jungle cities. Only to have the fleets turn up to dense jungle years later and fine nothing. But yeah, I also think about lost treasure and Indian Jones a lot with these stories.

Some of those ancient cities disappeared a lot earlier than Spain even existed, though. People likely abandoned them for some unknown reason and moved to other locations, where they'd eventually get wiped out by the Spanish.

Exactly, and likely some of these cities were destroyed by rival kingdoms we don't even know existed, if written history in other regions is anything to go by.

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#14

Post by sampo »

TulliusCicero wrote: post #6

How do the LIDARs work for this kind of thing? I always imagined that the light used wouldn't be able to penetrate objects that are opaque in the visible light spectrum.

Here is a fisheye photo from the bottom of a rainforest. As you can see, some spots of sky are visible from the bottom. When you fly above the forest and LIDAR is looking down, similarly at some spots the LIDAR laser beams are able to hit all the way to the bottom at some spots through the canopy.

It's not a big fraction, but some of the laser beams are hitting the ground, and after data processing you filter them out and they five you the ground topography profile.

https://www.sciencephoto.com/media/972412/view/rainforest-ca...

Here is a side view that shows how the point cloud profile can look like. This is not from a rainforest but some other forest.

https://www.researchgate.net/figure/LiDAR-point-cloud-profil...

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#16

Post by coffeecantcode »

gonzo41 wrote: post #9
ge96 wrote: post #2

Everytime I see these I think of lost gold.

Every time i see these I think about Spanish explorers who brought small pox over and caused these cities to collapse, only to return to Spain telling stories of jungle cities. Only to have the fleets turn up to dense jungle years later and fine nothing. But yeah, I also think about lost treasure and Indian Jones a lot with these stories.

There’s proven to be massive amounts of rare earth metals used by the indigenous populations in that area at that time, so it’s only natural to imagine that finding “lost” or abandoned cities from around that time has the potential to uncover large amounts of rare metals as well, potentially even cities that explain the stories told of cities filled with gold. The original comment didn’t need a history lesson on the Spanish conquests.

Replies like yours belong on Reddit, what an insufferable outlook on life and history.

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#17

Post by ricardobeat »

rockskon wrote: post #10
ricardobeat wrote: post #5

Earlier quoted context omitted.

The previous common-sense belief was that the Amazon was never densely populated and had always been exactly like it is today, a dense forest with primitive tribes scattered hundreds of km apart. Twenty years ago, brazilian researchers who would mention this theory were considered a bit lunatic, at the “elvis isn’t dead” or “the US reads all the world’s email” level of conspiracy theories. So playing down these disco…

Read, parse for keywords to take action against - what's the difference?

The article makes its main point to dispute the “City” characterization and how this is “overblown”.

I can only assume trkaky posted in the same spirit of discrediting the news, which I find worth “taking action” against. It might be old news for people in the field, and not reported faithfully (as usual), but what’s the purpose of raining down on one of the most interesting archeological discoveries in the Americas?

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#18

Post by alexey-salmin »

tempodox wrote: post #8
ricardobeat wrote: post #5

Earlier quoted context omitted.

The previous common-sense belief was that the Amazon was never densely populated and had always been exactly like it is today, a dense forest with primitive tribes scattered hundreds of km apart. Twenty years ago, brazilian researchers who would mention this theory were considered a bit lunatic, at the “elvis isn’t dead” or “the US reads all the world’s email” level of conspiracy theories. So playing down these disco…

Agreed, but: > “the US reads all the world’s email” level of conspiracy theories Never say never.

Perhaps the parent comment is alluding to Elvis actually being not dead

Re: Laser mapping reveals oldest Amazonian cities, built 2500 years ago (2024)

#19

Post by lazide »

alexey-salmin wrote: post #18
tempodox wrote: post #8

Earlier quoted context omitted.

Agreed, but: > “the US reads all the world’s email” level of conspiracy theories Never say never.

Perhaps the parent comment is alluding to Elvis actually being not dead

He just went home (/s)
Post reply on HN