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The scale of time in fields like astrophysics and geology never ceases to amaze me. When I saw freshly made, I thought it was recently created. Turns out it dro
by hiyer 5y ago
The scale of time in fields like astrophysics and geology never ceases to amaze me. When I saw freshly made, I thought it was recently created. Turns out it dropped on earth some time in the last 10 million years.
- dylan604 5y agoThis was my initial thoughts on reading the title as well. First thoughts were "what craft re-entered with that material" went to "oh, cosmologically recent".
- est31 5y agoOceanic plates are indeed quite young compared to the continental plates. Oceanic plates are made from heavier materials and subduct below the lighter continental plates, so they only live millions of years while the material making up continental plates lives billions.
- accrual 5y agoI sometimes wonder about interesting fossils and lifeforms we'll never know of, because they were subducted away before we ever had a chance to discover them.
- klodolph 5y agoI sometimes wonder if life evolved on exoplanets, complete with its own billions of years of fossil record, only to be obliterated when their star reaches the red giant phase.
- duxup 5y agoOr even on earth: https://en.m.wikipedia.org/wiki/Silurian_hypothesis https://en.m.wikipedia.org/wiki/Silurian_hypothesis Granted it is just a hypothesis but it is an interesting idea.
- andrewflnr 5y agoHell, I'm worried about fossils on Venus buried under kilometers of lava. That's actually pretty likely IMO.
- est31 5y agoNot just subduction but also erosion. Outside of dedicated digging efforts like deep mines or such, the fossils we find today are the ones close to the surface that are almost eroded and will be gone soon (on geologic timescales). There is a nice curious droid video on the topic whether a humans if they went extinct tomorrow, wouldn't create a fossil record similar to dinosaurs, simply because we've been on planet earth for a too short period. https://youtu.be/8xDK2LgSeyk https://youtu.be/8xDK2LgSeyk > What we have to remember is that they existed for over 165 million years, 3300 times longer than modern humans have been around and the number of creatures that lived in that time frame alone, not including very small insect-sized ones must be in the trillions. However, only a tiny number of those would have been in the right conditions to be quickly covered in sediment and then fossilized. Then millions of years later they happen to be exposed on the surface at just the right time before they are eroded away for us to find them. The latest estimate is that the total number of modern humans to have ever existed over the 50,000 years we have been around is about 107 billion. But 50,000 years is a very small slice of geological time and all of our 5000 years of recorded history would be a fraction of that, and the last 200 years or so since the industrial revolution, a tiny fraction of that again, maybe a razor-thin sliver of a darkened layer somewhere in the dozens of kilometers of limestone, siltstone, and shale of the future earth's crust. Depending on where we look, there are gaps covering millions of years in the fossil records, if we were to slip into one of those, we too would be lost in time.
- duxup 5y agoMaybe not just lifeforms, civilizations? https://en.m.wikipedia.org/wiki/Silurian_hypothesis https://en.m.wikipedia.org/wiki/Silurian_hypothesis
- pmichaud 5y agoI think this is a bit misleading. It's true that the average density of oceanic crust is greater than that of continental crust, making it less buoyant, but also continental crust is way thicker and overall more massive, which is a huge factor in causing oceanic crust to subduct in addition to the buoyancy factor.
- Haga 5y agoThere was a great scifi series by David Brin, were in One book a illegal settlement dumped all their garbage near a oceanic fault zone because these would swallow the evidence "quickly".
- MAGZine 5y agoAstronomy is a somewhat weird field in this in other respects. For example, astronomers frequently consider everything that isn't helium or hydrogen a "metal." They just have a very different take on some things, because their way of looking at the universe is different from how we look at earth.
- vagrantJin 5y agoThat strikes me as sbsurd. Sure, the table has mostly metals but there are a lot of gases.
- goldenkey 5y agoEverything's pretty much a plasma when it's burning at millions of degrees.
- matkoniecz 5y agoUniverse is more than 98% hydrogen and helium by mass, with all other being less than 2%. Maybe metal was not the best word for that, but having word for "all elements except hydrogen and helium" is useful in astronomy see https://en.wikipedia.org/wiki/Metallicity https://en.wikipedia.org/wiki/Metallicity
- rob74 5y agoOk, so, maybe they could have, you know, invented a new word? Or picked another one which isn't putting them at odds with the chemists?
- KingOfCoders 5y agoIf it works for them.
- ben0x539 5y agoAstrophysics was probably a thing before chemistry, so maybe the chemists ought to have picked a different word!
- misterremote 5y agoHaha, exactly me!
- deleted 5y ago[deleted]
- amelius 5y agoAstrophysics should invent their own terminology instead of repurposing ours.
- falcolas 5y agoThe same can (and has) been applied to every profession out there. Daemons, bugs, etc. Jargon will always exist.
- BitwiseFool 5y agoWhat's awe inspiring to me is the fact that life on Earth was single celled for around 3.5 Billion years.
- Bilal_io 5y agoYeah, I read "10" and my brain automatically filled in "days" until I read "millions of years"