What did Earth look like X million years ago? | Hacker News Reader

What did Earth look like X million years ago?

dinosaurpictures.org

423 pointsrport75 comments

Previously: https://news.ycombinator.com/item?id=17286770

Has a bunch of comments by the author.

That's pretty cool.

I have two suggestions, if the developer is seeing this:

- Mark the North and South poles. For someone unfamiliar with the past continental layouts, it's easy to get a bit disoriented . I would find a location on the globe, jump back in time, rotate the globe a bit to look around, then jump further back in time and then start to get disoriented as to where on earth the details I'm looking at are. Yes, you can figure it out, but I think it could be made much easier to do.

- Have a checkbox for overlaying the outlines of the present-day continents (in their present-day positions) over the globe. This would also help the user to orient what they're looking at.

It would also be really useful if night could be turned off, and if the gimbal lock rotation issues (I'm guessing) could be avoided (with quaternions?).

> - Mark the North and South poles.

I find it easy to tell where the poles are - that's where the cloud texture gets visibly broken :).

Looks like development has been pretty dry. https://github.com/typpo/ancient-earth The repo does not contain the texture maps but you can run an instance locally

Last week I was in the field digging dinosaurs in Montana, when one of the dig leaders mentioned there was no grass back then, just lots of ferns, because grass hadn't evolved yet.

It kind of blew my mind that for most of dinosaurs, there was just a lot of leafs and ferns.

Here's some pictures for context (https://imgur.com/a/rE5wwc4), when you're out where most dino bones are found, you forget that it may have been a lush landscape of riverbeds approaching the ocean coastline, or that it may have been a dry arid desert landscape like in the land before time movies. Regardless, it's odd to imagine all of it, with no grass.

Lots of mosses though? I imagine more primitive vegetation filled that role.

Dunno! I think most larger dinosaurs then needed larger sources of energy. Look at the teeth of an ankylosaur or most ceratopsians - they're designed to chomp and scissor through large leafy kale.

Adapted, not designed.

Can anyone just dig? I’d love to join the journey for a week or two.

There wasn't even grass in South Africa until humans brought it there. Surprised me too.

Really? It doesn't seem to be true: http://rstb.royalsocietypublishing.org/content/371/1696/2015... talks about grasslands in South Africa 1-2 million years ago, well before humans existed.

OK, it seems I misunderstood because I don't know much about grass. It seems there was some grass there a long time ago, but there is also a lot of "alien grass" that was introduced to the Cape region by humans. The alien grass is considered invasive and outcompetes the natural vegetation there which is called fynbos.

400 million years ago, there were no trees. But there were giant mushroom forests https://www.smithsonianmag.com/smart-news/long-before-trees-...

Do you have a blog post with more photos/context? It can be an interesting submission, specially if you can answer the comments.

Not only that, but grass has a special kind of photosynthesis that can survive in a lower CO2 atmosphere than other kinds of plants. Believe it or not, one of the long term hazards for life is too little CO2 for photosynthesis, below 100 ppm. The long term driver of CO2 is geology: weathering of rocks and formation of limestone in the deep ocean remove CO2; subduction zone volcanos return it to the atmosphere. Biosphere carbon is less than one percent of geologic carbon. When the Earth cools down too much to continue plate tectonics in a billion years or so, there will be too little volcanic carbon returned to the atmosphere. Plants and algae will die and so will all animals that eat them. Only chemeotrophic microbes will remain.

Sentient life could halt this process by burning limestone to release carbon. This is how cement is made.

When I was a kid I had a wonderful collection of magazines called "Prehistoric Zoobooks." https://www.google.com/search?q=prehistoric+zoobooks&client=... Each one in the series described an era of life on Earth from the beginning to now, with fantastic illustrations. I used to read them from beginning to end over and over again. I really want to find something similar for my kids ideally with modern reconstructions, but can't find anything comparable. Any recommendations?

I recall this series as well (in a dark green plastic case?), and the closest experience I’ve come across as an adult has continuously been the Smithsonian Natural History museum. Every era is captured in a different exhibit.

Somewhere outside the Schwarzschild radius of every black hole is a region in which the path of incoming photons is 'bent' 180 degrees and they are sent back roughly in the direction from which they came.

In my mind this means that some infinitesimally small portion of the photons that fall on the earth every day were reflected from the earth ~50K years ago and sent in the direction of the black hole at the center of the Milky Way.

I sometimes wonder if we could build a telescope large enough to resolve these photons into an image of the earth from that time. This would likely require 5,000 years of technological development and construction, but it does seem like it's physically possible. (Maybe there's too much dust or distortion or background noise to actually pick out the signal, dunno)

We couldn't go back XXX million years, but maybe XX thousand?

I have followed the same idea regarding radio waves. Would it be possible to travel far enough out to receive radio or TV broadcasts from WWII? Presumably all that information in the form of waves is still out there (assuming it hasn't been too distorted by inference, or far too small of an amplitude).

No, because you can't catch up with radio waves since they are going the speed of light.

But using OP's idea, they could be reflected back at the earth, such that 2018 - 1942 = 2 x numLightYears away from the scattering object. I agree, you wouldn't be able to go "in front of the waves" but you might be able to go to a point in space where they'd eventually arrive through scattering. I think it's very unlikely anyways since the solid angle for them to be reflected right back at a certain point is super small.

Very unlikely indeed. I wish I was smart enough to do the math but I'm sure it's more difficult than resolving a planet 50k light years away. Probably more like resolving a planet in another galaxy.

I fixed the typo, the factor of a half should have been on the other side of the equation. To actually calculate a realistic probability would require more work; farther objects would imply higher attenuation, etc.

It's late so I'm a bit too lazy to find the paper I remember, but this is the generalized form of that concept: https://thetechreader.com/tech/it-is-scientifically-possible...

I think that signal strength would decrease along the lines of the inverse square, so after you're some distance out, depending on the initial signal strength you'd find it had decayed to a level indistinguishable from background noise.

I think.

The problem is the wavelength of light puts a hard limit on angular resolution, its the same reason why a spy satellite cannot read your newspaper, or microscopes can not see atoms, its physically impossible.

https://en.wikipedia.org/wiki/Angular_resolution

It is my understanding that you can mitigate this to an extent by making larger scopes or employing techniques like interferometry. I haven't found an absolute 'hard limit', only a limit based on the size of the resolving device.

I'm generally a moron in this area though so I'm certainly missing large swaths of information.

On the other hand, earth is a finite sized object, and so are photons, so there are only so many photons to work with no matter how large your detector.

[I agree.]

I'm too lazy to try the calculations now, but if the nearest black hole is 2800 ly away, I guess the size of lens to resolve a dinosaur have to be much bigger than the solar system. Probably a few light-year [calculation needed]. Does the lens reach Proxima Centaury? Does the lens collapse and form another black hole?

Also, the black holes are big, but they are more far away than big, so the angular size of the area that does some interesting lens effect is very small. Then even if you have a giant lens and collect all the light that the black hole has blended (more than 90° or something), you will get a extremely dim image. But photons are discrete, and visible photons have a minimal energy, so the image will be composed of a very small amount of dots, and not something smooth where you can see anything.

You have to wonder what is possible when you see articles like this one when you collect enough data: https://news.ycombinator.com/item?id=17692447

Most black holes, especially ones at the heart of galaxies, are surrounded by huge clouds of dust and gas, and their own accretion disks. Also even for a bare black hole, it's gravity field won't be perfectly uniform to any image would be hugely distorted (like a lens made of poor quality uneven glass). On top of that as photons transit through the gravity field, even if that was perfectly uniform photons on slightly different paths would have their wavelengths stretched different amounts causing diffraction smearing the image. Finally the light path would have to be pretty close to the black hole to slingshot all the way round it, so the gravitational gradient is going to be very steep, meaning all of these effects are going to be very severe. In reality, even for a bare nonrotating black hole (much worse effects if it's rotating), which isn't really a thing as far as we know, the resulting signal is unlikely to be distinguishable from random noise.

The earth will have moved from its original position, so you'd probably need to catch photons that were shot off on 'paths' that will intersect your future position, which may not necessarily be photons that were 180-degree reversed.

Previous discussion from 2 months ago:

https://news.ycombinator.com/item?id=17286770 (59 comments, some from the author)

I had no idea flowers evolved so late. The first flowers were 100 million years after the first dinosaurs!

The majority of flora we see now also evolved very late. The dinosaurs probably saw and fed on Conifers, Cycadophytes and Ferns. Grass and Modern leafed flora evolved much later.

You can see what forests might have looked like 100mm years ago by going to New Zealand, which split off from the Australian landmass about that long ago.

The native flora consists of a lot of ferns, and almost entirely evergreen plants. Flowers are uncommon and primitive, most plants are pollinated and spread by birds. The only native grasses are tussocks.

Head down to Curio Bay and see the remains of a forest from 180mya, too.

There are studies that suggests grass existed around 100 million years ago though, https://www.ncbi.nlm.nih.gov/pubmed/16293759

Interesting. I will have to go down the rabbit hole again I think.. A lot of new and interesting stuff comes out of the Gondwana exiled regions, which is great!

Awesome! It's great to see India move northward between 50m and 35m years ago, and smash into the Eurasian body, creating what is now the Himalayan range.

Here's a curious question, India merged into Eurasia ~40 million years ago, Dinosaurs became extinct around 66 million years ago. When dinosaurs were around India was still an island. We know for sure about the presence of Dinosaurs in ancient India through fossils records https://en.wikipedia.org/wiki/Rajasaurus . So how did the dinosaurs populate an isolated island? Or did they evolve independently of each other in different islands?

First dinosaurs appeared as early as 230 million years ago, when what later became India was a part of the huge continent:

http://dinosaurpictures.org/ancient-earth#240

India became "an island" continent only almost 100 million years later than that.

If you go back to 200 million years you'll see India firmly attached and it broke away ~150 million years ago, Dinosaurs are ~240 million years old.

Like another commentator mentioned, dinosaur started appearing ~230m years ago. If you go back ~200m years, you'll see that India, Africa and the Americas are all fused together into a supercontinent.

The preminent hypothesis for the end of the dinosaurs before the Alverezes found the meteoric Iridium layer 40 years ago was large volcanos in India poisoned the planets ecosystem.

Some geologists hold that dino extinction was caused by multiple factors including a meteor, volcanos, and a preceding general decline of the genus.

The creator himself had posted this earlier at HN. https://news.ycombinator.com/item?id=17286770

I’ve always been fascinated by the animals from the era of megafauna, specifically the Pleistocene. Wikipedia is a great start, but details like paintings, behavior, etc are a bit more scarce.

Does anyone have any recommendations for good resources that are approachable for non-scientists?

Some megafauna examples:

Megaloceros, the giant deer who had antlers 12 feet wide- https://en.m.wikipedia.org/wiki/Irish_elk

Arctotherium, the largest bear and potentially the largest land carnivore, ever - https://en.m.wikipedia.org/wiki/Arctotherium

Titanis, one of the largest carnivorous terror birds - https://en.m.wikipedia.org/wiki/Titanis

Megatherium, the giant, elephant sized sloth that dug gigantic burrows - https://en.m.wikipedia.org/wiki/Megatherium

Thylacoleo carnifex, the marsupial lion, and largest carnivorous marsupial in Australia - https://en.m.wikipedia.org/wiki/Marsupial_lion

Camelops, a family of camels native to North America - https://en.m.wikipedia.org/wiki/Camelops

Thylacosmilus, a Metatherian (similar to marsupial), Sabre toothed carnivore from South America - https://en.m.wikipedia.org/wiki/Thylacosmilus

This actually answered a question I had wondered about - in the North West of Scotland there are mountains made of a distinct sandstone - Torridonian (named after the sea loch). I remember reading that the material that created this sandstone came from the erosion of mountains to the North West (where the Atlantic is now).

I looked up Scotland and 750 million years ago and there is a range of mountains to the North West. :-)

Incidentally, one of the cool things about the North West of Scotland is that the original landscape that was buried by the sandstone has been exposed in places.

Edit: I also seen to remember reading that the Brownstone buildings of New York are actually made from the same stone deposited on areas that ended up on the other side of the Atlantic when it split.

It would be cool if this could show what the Earth would look like in the future too.

Topically, I see Britain had everything sorted 150 million years ago while the rest of Europe was in a right heap.

First thing I noticed as well. Joking aside: Any ideas why this is so? It's not that the British Islands elevation is so extreme.

No idea, it surprised me too.

The British Isles are away from the plate edges where most disruptive geologic activity occurs (earthquakes, volcanoes, subduction, etc). The rest of Europe is along the edges of the plate and was geologically active. If you look at North West Brazil you can see very little happens for over 240 million years (away from plate edge) while Oceania has been very active for the last 100+ million years (and is still very active).

If you look at the ocean while you go back in time you can see large swaths that have very little detail. This is because that rock has been geologically recycled and is no longer part of the geologic record.

Brilliant, although it would be excellent if the transitions between the times was animation.

Perhaps the time could be represented as a video. Draw a video frame to a canvas and use as a texture for the sphere. As the time is updated just play forward or backward to a video point and the texture would update.

You have to love the giant black dot on the yucatan when you set it to the extinction of the dinosaurs.

Nice catch. That dot is surprisingly small to have caused so much hoopla, but I guess it makes sense when you think about it.

The first time I read (in school) about an asteroid hitting the Gulf of Mexico and causing the extinction of the dinosaurs, I looked at a map and sure enough the Gulf of Mexico looked like a big round hole where the asteroid must have hit.

Later I realized that the dinosaur-killing crater is much smaller and buried and hidden at the edge of the Gulf of Mexico. I also learned that the Gulf of Mexico was formed to due plate tectonics, not due to an impact. What an odd coincidence that the dinosaur-killing asteroid hit a location on the Earth that looks just like a huge crater, but isn't a crater at all.

Are polar ice caps that rare of an event for the Earth? I only see them at 600 (N & S), 450 (S), 300 (S), 35 (S) and 20 (S) Mya.

Has anyone made a large-format map (or better yet: globe) across which one can scroll to past geographic and political maps?

Absolutely no idea, but I'd love to see this if so.

There are numerous specialised atlases and globes. I've never run across a generalised mapping engine and dataset like this.

Wikipedia / Wikimedia have a number of map sets, that might be a place to start your search.

Great question.

Here's one: http://geacron.com I'm sure I saw another one recently with a better GUI but I can't seem to find it again.

I think so! The "Magic Planet" is a digital projection globe that can display all sorts of different datasets. I've been more interested in its planetary science, astronomy, and geology applications, but I believe they've got lots of political, cultural, and economic visualizations as well.

http://globalimagination.com/

Is it not possible to zoom? It becomes un-viewable when I do?

Would be cool to have "snowball earth" pop up there around 700mya.

Love the left-right arrow key shortcuts here.

Africa 90m years before was splitted into two giant pieces, and then merged into one piece ??

How do we know the geography of so long ago?

Plate tectonics and Continental drift ??

And geochemistry.

The geochemistry goes without saying.

And palaeontology.

There may be tens of thousand of research papers behind each map shown in the OP. It is like solving a puzzle. At location X, Scientist A finds some clues in plate tectonics, Scientist B finds something in geochemistry, and Scientist C finds something in fossil records. Then they piece them together and if these stories all tell the same thing without a serious conflict, you can construct a point on that map. Now imagine doing this for thousands of different regions involving several generations of scientists, you get nice maps like these.

This Wikipedia page would be a nice read: https://en.wikipedia.org/wiki/History_of_Earth.

Magnetic striping on the sea floor [https://en.wikipedia.org/wiki/Plate_tectonics#Magnetic_strip...] is probably our best clue. It's the piece of evidence that sealed plate tectonic's place as the dominant theory.

Plates which are separating let molten rock from the mantle up, where it cools hardens. Any rock which can be magnetised (iron) is aligned with the Earth's magnetic field when molten, and gets fixed that way. The magnetic field swaps every 10,000 years or so [https://en.wikipedia.org/wiki/Geomagnetic_reversal], so you get a stripey effect.

Working our more precised dates for the magnetic swaps is a matter of slow and painstaking correlation with other bits of evidence: dating of radioactive elements, tree rings, rock layers, the temperature of the Earth, composition of gas bubbles trapped in rock and ice.

Paleomagnetism measurement of the magnetic field direction in a rock gives the latitude of a the rock when it formed. The magnetic fields are horizontal at the equator and vertical at the poles, thereby giving latitude of the rock when is cooled from volcanic hardening or the last metamorphic squeeze. And there is a magnetic imprint when sediments settle too.

Latitude when combined with geometric constraints of seafloor strips and correlated trans-ocean rock formations build the overall picture.

In addition the oldest seafloor is 220 million years old or 5% of Earths lifetime. Paleomag measurements go back ten times longer.

Those are fun and interesting corrections, thank you.

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