Constellations are younger than continents

[antognini]

There is an interesting theory about the Pleiades star cluster [1]. The Pleiades are somewhat unique in that they are a prominent feature of the sky and close to the celestial equator. Because of that, they are visible to every population on Earth, and every culture has developed a story around them.

Around 2/3 of cultures have a story in which there are seven things (seven sisters, seven boys, seven chickens, and so forth.). The other 1/3 of cultures have a story in which there are six things. And a surprising number of them have a story in which there were originally seven, but one got lost (like in the Greek myth of Electra).

The interesting thing is that two of the stars in the cluster are quite close together and can't be distinguished by eye. A pair of astronomers looked at the proper motions of the stars in the cluster and figured out that tens of thousands of years ago these two stars were far enough apart that they could have been distinguished by eye. So it seems that early humans recognized the Pleiades as having seven stars and this persisted in the myths of most cultures for tens of thousands of years, even when the seventh star was no longer visible.

[1]: https://arxiv.org/abs/2101.09170

[Amezarak]

Although I like the idea, there's no reason to posit the preservation of the myth of a lost star for tens of thousands of years. People can still see all Seven Sisters under the right conditions, and the right conditions were probably much more prevalent back before the insane degree of light and air pollution that exists today.

https://skyandtelescope.org/astronomy-news/many-pleiades-can...

[calamari4065]

This is one of my favorite stories.

One of the best parts is the legend of the seven sisters in Australian aboriginal tradition.

Theory goes that the legend far, far predates first contact with Europeans, so it must have come with the first aboriginal settlers when they sailed from Africa. Which would make it one of (if not the) oldest stories in history.

[globular-toast]

I don't know. When I look at Pleiades I can see how you could see 5 (the brightest ones) or 8-9 (the best brightest ones), but not 6 or 7.

[tsimionescu]

That's a cute idea, but it's extremely unlikely to be true. If nothing else, the human fascination with 7 is a much more likely explanation, especially since 6 is nowhere near as important a number in this way (1,2,3 and 7 are much more common in myths and fairytales).

[bjackman]

Also: Polaris (the north star) is younger than sharks.

(This one is less interesting as an overall observation about timescales though. Polaris is just quite a young star and sharks are quite and old life form).

[kibwen]

Polaris as the north star is younger than the Roman Empire!

Because of the precession of the Earth's axis, Polaris didn't become the north star until about 500 AD. To the ancient Egyptians, Thuban was the north star. When humans were first discovering agriculture 12,000 years ago, Vega was the north star.

Wikipedia has a great table showing the cycle of north stars: https://en.m.wikipedia.org/wiki/Pole_star#Precession_of_the_...

[Sharlin]

As the article implies, all the brightest stars in Orion are younger than hominids. Indeed they formed around the time when the last common ancestor of humans and chimpanzees lived.

[vasco]

Trees are also younger than sharks.

[throwup238]

Another fun fact: very early humans (Australopithecus) coexisted with megalodons, giant dinosaur sharks that could swallow a hairless ape whole.

[Nition]

Sharks go back more than 3% of the way to the beginning of the universe.

[mock-possum]

The rings of Saturn are also (probably) younger than sharks!

[p-o]

These kind of facts always blow my mind. For instance, the Sun orbits the milky way once every 212m years.

That means that if the sun existed from the big bang to now, it would have only done ~63 complete revolutions around Sagittarius A*. If you account for the Milky Way's creation, that number gets even lower. I'm no expert, so maybe this makes sense to someone who knows more about this, but it definitively feel weird to me.

[mihaitodor]

I wondered the same thing and I asked Sean Carroll about it [1]. He didn’t go into much detail, but here is his answer:

> I guess my only insight is, I'm not sure why you relate the number of revolutions that the Milky Way has made to its complex and symmetric structure. The spiral arms that you see in a galaxy like the Milky Way do not rigidly rotate with it, they are more like... This is complicated, but they are more like regions where star formation is going on, and therefore the galaxy is brighter rather than regions where there's more density or anything like that. So if you're worrying how the spiral structure forms. It can form pretty easily in one or two revolutions, I don't see why it would take even 68, much less, but need more than that.

[1] https://www.preposterousuniverse.com/podcast/2023/10/09/ama-...

[gattr]

Another fun fact: there are more trees on Earth (3×10¹²) [1] than stars in the Milky Way (1-4×10¹¹).

[1] "Mapping tree density at a global scale" https://www.nature.com/articles/nature14967

[defaultcompany]

Agreed. Another surprising one to me is that the earth itself has been around for about 1/3 the age of the universe. I always assumed that the timescale of the universe was vastly longer than the life of the earth.

[k7sune]

Wow it’s amazing that we could somehow time the orbit period.

[nickdothutton]

There is a nice simulation of constellations changing over time in one of the episodes of Sagan’s Cosmos, where he explains parallax and some of the other important phenomena.

[aebtebeten]

H A Rey The Stars (1952) had a nice series of cartoons depicting a caveman, a grey-flannel-suit man, and a futuristic man all looking at their respective versions of the big dipper.

The Barbers' When They Severed Earth From Sky (2004) hypothesises that the various kingship changes in heaven of several ancient mythologies correspond to the precession of the solstices and equinoxes through the zodiac. Eg, for Greek mythology, they give:

    Head God    Summer    Spring
    CHAOS       Libra     Cancer
              ~6480 BC
    OURANOS     Virgo     Gemini
              ~4320 BC
    KRONOS      Leo       Taurus
              ~2160 BC
    ZEUS        Cancer    Aries            
                

along with parallel tables for Babylonian, Hittite, Phoenician, and Norse mythologies, and reference a different work which should give Germanic, Finnic, Iranian, Indian, and Chinese mythological shifts.

According to this hypothesis, when the fall equinox moved into Virgo and Saturn and Jupiter came into conjunction with Pisces in 6 BC, many ancients took it as marking the advent of a new Kingdom of Heaven ruling a New Age, making them more susceptible to picking up new religions emanating from the middle east around that time, eg Mithraism.

Does Virgil, writing ca 40 BC, predict the New Age? [Fourth Eclogue 4-10]

> Now is come the last age of Cumaean song; the great line of the centuries begins anew. Now the Virgin returns, the reign of Saturn returns; now a new generation descends from heaven on high. Only do you, pure Lucina, smile on the birth of the child, under whom the iron brood shall at last cease and a golden race spring up throughout the world!

(but note that by this counting the "Age of Aquarius" wouldn't be due to start until ca 2160; rather far off in human lifetimes from the 1960s)

[whartung]

I actually remember a couple of diagrams in a science book way back in elementary school, so we’re talking 70s here, showing the Big Dipper today and what it would look like in 50,000 years.

It was a kind of weird feeling as a young boy “seeing” change to something considered so static, and all the deeper considerations from that.

[__MatrixMan__]

I was surprised to learn that Pangaea is believed to have formed and broke up at least five times so far.

[knorker]

Another one: dinosaurs existed on the other side of the galaxy.

The galaxy has revolved about half a revolution since then.

[Tommstein]

The Milky Way is also moving through space. So they actually existed way out in intergalactic space (probably).

[Rhaomi]

https://www.theonion.com/darling-i-will-give-you-the-moon-an...

[NKosmatos]

This article brought back memories of when I was playing around with astronomy simulation software like Redshift by Maris Multimedia.

I started searching for it, and as it usually goes with HN stories, I ended up on their new/modern version of it over at: https://redshiftsky.com

A brief history of their famous titles (check also aviation) is over at: http://archaic.maris.com/content/indexe5cc.html

Older versions of Redshift can be downloaded/found over at the Internet Archive:

https://archive.org/details/redshift_202204

https://archive.org/details/redshift2

https://archive.org/details/Redshift_3_Maris_Multimedia_1998

[asystole]

There’s also the FLOSS Stellarium: http://stellarium.org/

[runsWphotons]

How accurately could we predict when betelgeuse will go? What are the CIs?

[MengerSponge]

Literally any moment in the next 10000 years. The probability distribution (afaict) is pretty flat, and either 1000, 10000, or 1000000 years long.

[geuis]

Part of the problem is that direct observations of supernovas is small and indirect. We have small numbers of recorded occurrences to judge from.

[rini17]

Animation from GAIA data: https://www.esa.int/ESA_Multimedia/Videos/2020/12/Gaia_s_ste...

[vardump]

Humanity might one day spread to all over the galaxy by hitchhiking passing stars.

Well, assuming we don't self-annihilate ourselves at some point. Or be destroyed by some cataclysm.

I guess we'd better spread to as many locations in the solar system as, err, humanly possible.

[perlgeek]

Communication across interstellar space would be super slow, because the speed of light is so slow compared to the distances, like, at least several years for a single one-way message.

This makes it likely that if we ever do settle multiple stars, culture and language will diverge pretty strongly across the different settlements, potentially making other, distant humans our worst potential enemies.

[kybernetikos]

I think the constellations through the ages chart make it clear that orion has been recognisable long enough to see continents change and will be recognisable for a long time to come.

[bleuarff]

The article goes on to say these stars are very young at ~10My, which is about the smallest time scale at which you might notice some change on continents'aspect. So you're probably technically right, but by a very thin margin.

[layer8]

Did you read the article? The stars in Orion are only between 6 and 12 million years old, and the continents already looked almost the same as today in that time frame. Furthermore, they are types of stars that won't live very long, at most 20 million more years. Betelgeuse will go supernova within just the next 100,000 years. The Orion stars will see a little bit of continental movement over their lifetime, but not "rise and fall".

[FergusArgyll]

Life in West Virginia is younger than the mountains but older than the trees

[ggsp]

Isn’t life everywhere older than the trees?

[rpmisms]

Here's a yule-flavored reminder that Denver's talking about Western Virginia, since that's where the Blue Ridge mountains are.

He'd also never been here, so he might have just been wrong.

[krisoft]

Also, not to mention that constellations are a human made construct. It is like how day night cycles are natural, and have existed before us, but calling every seventh cycle “monday” is not.

The stars and their appearance on the sky is natural like the day-night cycles, while how they are grouped together and what they are called is human made. (And different civilisations had wildly differing opinions on how this should be done.)

[nine_k]

No matter how one would choose to group stars in the sky, the point is that their relative angular closeness varies faster than that of continents on our planet.

[hinkley]

I wonder when we started telling stories about them though. There’s not much to do once the sun sets, prior to the invention of the oil lamp.

Unfortunately Orion is still older than most hominids. I can imagine a new constellation triggering the “need” for new stories, but only after language developed.

And while I strongly believe we will continue to push back the beginnings of Man, and of civilization, we are probably past the inflection point. I suspect we aren’t likely to quadruple the origin dates for our species. Which is what you’d need to have a plausible story about oral traditions affected by Orion sprouting a new star.

[nullindividual]

Wouldn’t Saturday be the seventh cycle, given it is the end of the week?

[yunohn]

I would argue that as a result of circadian rhythms, the Lunar calendar atleast makes more sense than the Gregorian one.