I guess it's possible
But I think to confirm for sure, they should really be checking the fossil records for evidence of the superpowers that these sharks developed.
A gigantic supernova explosion may have triggered mass extinctions for creatures living in Earth’s prehistoric oceans some 2.6 million years ago, according to new research published in Astrobiology. Marine animals like the megalodon, a fearsome shark around 10.5 meters (34 ft) long and with huge jaws full of sharp, pointy …
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I thought water was supposed to be an excellent protector against radiation? So was there something special about this particular radiation event (or were the levels just so high) that they negated the protective qualities of the water?
If this was a mass extinction of land animals I'd believe it in a second, but under water, hmmm. The figure I've found online is that you halve the level of radiation for every 7cm of water it passes through. To kill off underwater creatures that dont need to surface (like whales and dolphins), that must have been one hell of a radiation event, wouldnt it?
High energy muons are remarkably slippery and can pass a kilometer of water without to much trouble. The same thing applies to the ability to pass through a human, megalodon or whale though so I have no clue about how much energy are dumped into a nearby dna molecule when the muon zips by.
I think we can safely ignore the neutrinos though as you have to be inside the surface of the star to recieve a lethal dose of neutrino radiation from the supernova and unless the megalodons were surfing on the stars hitchhikers guide to the galaxy style they were probably not in any danger in that regard.!
See https://what-if.xkcd.com/73/ for the reference on lethal dose of neutrinos from supernovas.
" A lot of stuff eats the plankton and stuff that lives on sunlight. Kill that and it's a world of hurt."
Yeah. like, just as one example, the planet dies off completely. Kill the plankton (something humans are trying very hard to do right now) and the oxygen goes. No O2, no animals. No animals, no little monkey things with antelope thigh bones roaming the plains down in Africa.
There are baleen whales around today. The plankton *never* got wiped out or those wouldn't be here.
And, just as a thing, anything that kills off the plankton would have wiped out the *land* plants, too.
The planet would have been reduced to roaches, politicians and other lower lifeforms.
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There's more than one kind of radiation, with very different penetrating properties; in this case muons, which are massive and very penetrating, are produced by the interaction of cosmic rays with matter.
Incidentally whales and dolphins are sea creatures which do need to surface, to breathe!
"The radiation wouldn't need to go far through water. If iron-60 is dropping into the water and getting into the food chain, it would then emit the radiation whenever an atom decays - getting whatever happens to be local at that point."
Very nice, but a lot of people here are overlooking the minor detail that most living organisms and especially the somewhat larger ones have red blood with hemoglobin, which derives its characteristic colour and oxygen transporting abilities from the embedded iron atom. Thus most of these organisms are quite efficient in taking in any iron available, including radioactive iron-60. This will quickly accumulate in larger predators, so they are killed slowly from within by their own, radioactive blood.
To quote again:
"it would then emit the radiation whenever an atom decays - getting whatever happens to be local at that point."
Local at that point is somewhere in the animal, with a bit of bad luck in the bone marrow or the equivalent organ sharks use for creating red blood cells, which is an environment with lots of quickly dividing cells.
The paper suggests muon radiation affecting animals in shallow (or surface) waters. A muon carries a hell of a punch so it can penetrate into the water and then cause damage to cells. The bigger the animal, the bigger the risk of developing something nasty.
This might explain an oddity of the Pliocene-Pleistocene megafauna extinction; it doesn't appear to involve a collapse of the bottom of the food chain - microfauna and flora don't seem to go to the wall as they did say in the KPg event; instead this extinction disproportionately affects large animals.
There was a paper published in 2002 that pointed out a group of OB supergiants would have passed relatively close to the Earth. Had one of those exploded at the right/wrong time it would have had an effect on the Earth.
Narciso Benítez, Jesús Maíz-Apellániz, and Matilde Canelles et al. (2002). "Evidence for Nearby Supernova Explosions".
I thought water was supposed to be an excellent protector against radiation?
I had to look it up as I couldn't remember, but "secondary muons generated by cosmic rays hitting the atmosphere can penetrate to the Earth's surface, and even into deep mines." For the length of time the Earth was purportedly showered with an intensified amount of this radiation, it would have been difficult and unlikely for large animals to avoid exposure.
So if you have a 2% chance of dying from cancer it would rise to a whopping 3%? On no!
That's 50% increase for something the size of a human. Since you only need to get cancer in one cell, and it then spreads, if something is irradiating you, the larger cross-section you have, the higher the chance of one cell getting hit. Megaladons were quite large (60 feet, 130 linguine, or 2 double-decker buses) so would have been affected much much more than a human. Larger animals also tend to breed slower than smaller ones. There would have been a cut-off point in size, where that 2% would become high enough to kill things off faster than they breed, which would cause extinction.
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So another possible one-off event to add to the tally on whether intelligent life is common or not.
Our universe itself keeps on expanding and expanding,
In all of the directions it can whiz;
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there's intelligent life somewhere out in space,
'Cause there's bugger all down here on Earth!
Such scenario shouldn't have caused a very lethal extinction outside water? Also, shouldn't we spot some SN remains nearby, especially if it was a whole chain? Maybe a small black hole without gas around can be hard to identify (unless it perturbs something around), but a neutron star could have some chances to be identified as a pulsar, and a close pulsar with its beams directed towards us could not be nice as well.
Also, OB stars to be exploded only 2.6M years ago should have formed far later than Sun. Larger stars don't usually form earlier, when there's more mass available? Or something else started the formation of a group of star later (another SN impact wave?)
There's an apparent terrestrial megafauna extinction at around the same time as in the oceans. However, terrestrial fossils are much rarer than those in the oceans and they tend to be less well constrained in terms of date in part because suitable microfauna and microfloral fossils aren't as common on land.
The Pliocene-Pleistocene is also problematic because the climate was turning towards a glacial epoch and a lot of the uppermost Pliocene terrestrial deposits were either eroded or extensively reworked by advancing ice sheets. There's still some dispute over the exact boundary between the two in many parts of the world as there is no clear boundary.
Anyone know the lifetime of a visible neutron star? I rather suspect it will have cooled below the visible spectrum long ago. And of course, we don't know where to look.
As for the formation date - yep, an OB star has a life measured in mere tens of millions of years, so it couldn't have formed at the same time as the Sun. However, it's important to remember that whilst all stars orbit the centre of the Milky Way, they do not follow parallel orbits and are constantly rising and falling through the central plane of the galaxy. Our neighbourhood supernovae could be a long way away by now.
One proposal is that the killer might lie in a group of stars called the Scorpius–Centaurus Association which is between 380 and 470 light years away and is dominated by large, hot stars. Though other candidates are probably out there.
Anyone know the lifetime of a visible neutron star? I rather suspect it will have cooled below the visible spectrum long ago.
If they behave (thermally at least) like a white dwarf, then they will be extremely hot and cool down very slowly, effectively being a stellar core only able to lose heat by radiation. It's more likely that they would be difficult to spot visually because of their extremely small diameter (~20km) rather than because of their lack of inherent brightness.