Does it have something to do with how when you have one bucket of sand and one bucket of water and you mix them you only have one bucket of wet sand, not two?
Yes! wonderful! Though it is hard to think of turning alcohol into 'wet' alcohol, so I prefer explaining it like this:
If you have a measuring cylinder and fill it with pebbles up to 50ml, then fill it with sand, the sand flows in between the pebbles and so for a while the reading of 50ml doesn't change.
While water and alcohol both look the same, they differ by quite a bit in terms of size and shape, so when you pour water onto alcohol, some of it manages to get "in between" just as the sand went in between the pebbles.
50ml+50ml=96ml
Edit: This is why you end up with a bucket of wet sand. The water goes in between the sand. Also, this is why when you pour milk into tea, you use more milk than you'd have expected to fill up the mug.
... Yep. That's my contribution to the thread. Sheldon's Doppler costume. Umm... "Woo, science!"?
Sadly, I would kill him just to make me remember the worst year and a half I had in my life (While having aproved the signature in the second test out of 3 at the end somewhat fixed ^^!)
Edit: This is why you end up with a bucket of wet sand. The water goes in between the sand. Also, this is why when you pour milk into tea, you use more milk than you'd have expected to fill up the mug.
I remember reading a metaphor about how you should organise your time.
First you put the big things you have to do, they're the big pebbles, in a mug (that's your agenda).
With these few big things in there, you add smaller pebbles for the smaller things you have to do.
Then you can add sand for the more trivial thing you have to do, which will just fit in between/around the others.
And finally, you put water in it, which means you need to remember to grab a drink with your friends.
But if you manage your time but starting with the small things, well then the big pebbles won't all fit in the mug where the sand already is.
But once you've set time for the big, important things, you'll have lots of time left for the rest.
Well, that's not really science, but it uses the scientific thing you mentioned :P
Sadly, I would kill him just to make me remember the worst year and a half I had in my life (While having aproved the signature in the second test out of 3 at the end somewhat fixed ^^!)
So you're the engineer who built the crossbow that killed Sheldon!
I finished writing up the history of Earth. I think it's more or less correct. I used Wikipedia for my fact checking, and inferred some things. It came out kind of long.
The current eon, the Phanerozoic, meaning "abundant life" or "life appears", I think, began 542 million years ago, when animals evolved shells and bones, which made it a lot easier to find their fossils when these things were being defined.
The Phanerozoic is divided into three eras, the Paleozoic, the Mesozoic, and the Cenozoic. They can be described as the age of fish, the age of reptiles, and the age of mammals respectively, which is sort of accurate. I forgot where I read those descriptions, though.
The Paleozoic, which means "ancient life", is divided into six periods. Almost all of them are named after places, mostly in Britain. I usually think of the first three as being before animals came on land and the second three as being after, although that's only true for animals with backbones.
The first period of the Paleozoic was the Cambrian, which lasted from 542 million years ago to to 488 million years ago. Lots of stuff evolved at the start of the Cambrian, including early chordates (animals with backbones), early arthropods (bugs and crustaceans), and early molluscs. The chordates were mostly fish, and the arthropods were mostly trilobites, which were probably the first animals to evolve eyes. And there were jellyfish and a bunch of different varieties of worm, but they're not very interesting. All this happened in the ocean. Not much was happening on land. I think there were a few bacteria. The sudden emergence of all these different kinds of life is called the Cambrian explosion, because it happened so suddenly.
The next period was the Ordovician, and it lasted from 488 to 444 million years ago. I know two things about the Ordovician: a lot of the planet was covered in warm shallow seas, and that this was when sea scorpions evolved. Sea scorpions were arthropods, but they weren't really related to modern scorpions. They were large predators that lived in water; one was the size of a crocodile and was the biggest arthropod of all time.
The reason that things can't grow beyond a certain size is that their weight goes up by the cube of their size, but things strengthening them, like muscles, go up by the square of their size. So if it was four times as heavy, it would only be twice as strong, for example. And if it was three times as strong, it would be nine times as heavy. This is why ants can easily lift their own weight and humans can't. It's called the square-cube law. But sea scorpions lived underwater, so weight wasn't as much of a problem for them. That's also while giant squid and whales can get so big now.
The Ordovician ended with a few extinction events that, taken together, were worse than the extinction that killed the dinosaurs. They were probably caused by an ice age, but some people think it was a gamma ray burst - a flash of gamma rays, which is the deadliest kind of radiation, from a distant exploding star. All the observed gamma ray bursts so far have happened outside our galaxy, but if one happened nearby today, it would be... really bad.
Anyway, the next period was the Silurian. It lasted from 444 to 416 million years ago, and is the period when life really started to invade the land. The first land dwelling plants appeared about 425 million years ago, and arthropods, including the relatives of spiders and centipedes, probably appeared on land at about the same time. No vertebrates yet, though.
The Devonian period (416 to 359 million years ago) was when fish evolved legs and left the water, which happened about 397 million years ago, about halfway through the period. Once they started living partly on land, they weren't fish anymore, they were amphibians. They still had to return to water to lay their eggs, though. Also of note: Giant fungi. They were called Prototaxites, and they grew up to 8 metres (26 feet) tall.
The first trees also evolved during this period, creating the first forests. There was another mass extinction at the end of the Devonian, which mostly affected life in the ocean. It's not clear how it happened, but this is when trilobites began to decline after dominating the oceans for hundreds of millions of years.
The Carboniferous period (359 to 299 million years ago) is kind of underrated, in my opinion. Forests spread over most of the land, except for the land at the south pole, which was covered in ice at the time, kind of like now. Since coal comes from dead trees, a lot of coal is found in Carboniferous rocks; the word Carboniferous means coal-bearing. The forests converted a lot of carbon dioxide in the atmosphere to oxygen, raising the oxygen levels to more than one and a half times what they are today. Instead of killing things horribly like in the oxygen catastrophe, it just made giant bugs possible. Arthropods before and after are small because their method of breathing isn't very efficient, meaning that they can't exert themselves as much as we can. I think. Because there was more oxygen in the air, arthropods could to transport more air around their bodies with less effort, making it possible for them to grow bigger. Winged insects evolved during the Carboniferous, and some got especially big, with one species of griffinfly, Meganeura, having a wingspan of up to 75 centimetres, or 2.33 feet. Griffinflies were basically giant dragonflies, and they were probably the birds of this period. There were also giant centipedes that were 2.6 metres (8.5 feet) in length, giant scorpions that reached up to 1 metre (3.3 feet) and giant cockroach ancestors which were about three centimetres (1.2 inches). The last one doesn't sound like much compared to the others, but it's still far too big for a cockroach. But at least ants hadn't evolved yet, and what was thought to be a giant spider turned out to be a sea scorpion that looked like a spider.
During the Carboniferous, some amphibians evolved the ability to lay hard shelled eggs on land, and became reptiles and synapsids, which are like reptiles except they eventually evolved into mammals. The biggest difference between synapsids and reptiles is their teeth. Reptiles have teeth that are identical to each other, and synapsids had different teeth in different parts of their mouth, like mammals do. Other amphibians became successful predators resembling crocodiles. Pangea, the supercontinent made from every major landmass on Earth, also formed during the Carboniferous.
Oxygen levels were back down by the next period, the Permian (299 to 251 million years ago), though they were still higher than they are today. The larger giant bugs died out, but the cockroaches got a bit bigger. The reptiles and synapsids began to dominate as land animals, mostly replacing the amphibians. The Dimetrodon, an animal commonly mistaken for a dinosaur, actually lived in the Permian. Dimetrodons were synapsids, so they weren't even closely related to dinosaurs, which were reptiles, and they're most well known for having sails on their backs, which probably evolved to help warm them up.
The most significant thing about the Permian is the mass extinction that happened at the end of it, which is informally known as the Great Dying. It was much worse than any other extinction currently known, and killed off just about every land animal with a backbone except for a piglike synapsid, Lystrosaurus. Other land vertebrates did survive, or there wouldn't be any reptiles or amphibians today, but Lystrosaurus dominated to an amazing extent. It was devastating to the ocean as well, killing off the remaining trilobites, and even affected the insects, which is unusual. It's not clear what caused it, but I like the theory that trapped underwater methane was released into the atmosphere, causing global warming and reducing the amount of oxygen in the air and water, both choking and baking everything. Or it was a gamma ray burst again. There's lots of theories about it.
And that was the end of the Paleozoic era. The next one was the Mesozoic, which is the one with the dinosaurs. It's only divided into three periods, the Triassic, the Jurassic, and Cretaceous, as it was quite a bit shorter than the Paleozoic.
The Triassic lasted from 251 million years ago to 200 million years ago, and its name refers to the three different layers of rock from the Triassic, or something. I'm not really sure about that. Unlike the later periods of the Mesozoic, the Triassic was quite dry. Life was also less diverse than usual during the first half of the period. It took a long time to recover from the mass extinction at the end of the Permian, much longer than it did from any of the others. Dinosaurs evolved about halfway through the Triassic, but they didn't dominate. Mammals evolved a few million years later, and stayed small and nocturnal. Pterosaurs, the flying reptiles often mistaken for dinosaurs, also evolved in the Triassic.
The Triassic ended with another mass extinction, but it wasn't as bad as the one that started it. It hit synapsids, amphibians, and some kinds of non dinosaur reptiles hard, allowing the dinosaurs to evolve into the roles that the other animals left behind.
The Jurassic period (200 to 146 million years ago) was when the dinosaurs really started to dominate. Pangea began to break up, and the climate was a lot wetter. These things were probably partly related - it's usually drier in the middle of a continent than on the coast. This is the period where the long necked dinosaurs like Apatosaurus and Diplodocus did the best. This is also when Stegosaurus, my favourite dinosaur when I was seven, was around. Some groups of Ocean dwellingreptiles often mistaken for dinosaurs also evolved in Jurassic. Near the end of the period, some of the smaller dinosaurs- the t-rex shaped ones- evolved feathers, and some of them evolved into birds. Most carnivorous dinosaurs from then on probably either had feathers, or had ancestors who had feathers.
The Cretaceous period lasted from 146 to 66 (I'm rounding up here, it's really 65.5) million years ago, and means "chalky". It was a lot like the Jurassic, but it lasted for eighty million years and had less giant long necked dinosaurs who laughed at the square-cube law. Most of the well known dinosaurs and animals mistaken for dinosaurs lived in the Cretaceous, including Tyrannosaurus rex and Triceratops, which even lived at the same time (right before all the dinosaurs went extinct) and the same place (North America, where all the most famous dinosaurs seem to be from. Probably not a coincidence). Flowers evolved during the Cretaceous, which led to flying insects becoming more diverse to take advantage of them. The earliest flowers probably smelled like rotting meat.
A couple of million years before the end of the Cretaceous, there was a series of volcanic eruptions which choked the air with poisonous gas, which was not good for the animals, but they probably would've been fine eventually, if a giant rock hadn't slammed into the Earth at the end of the period. This caused a fireball and shockwave that killed nearby life instantly, and threw up enough dirt to block out the sun for a year, and to keep it dim for a few years after that. Without the sun, the plants died, without the plants, the herbivores died, and without the herbivores, the carnivores died. Some omnivorous and insectivore animals like mammals and birds survived. So did some water dwelling reptiles, like crocodiles and turtles.
The current era is the Cenozoic era, meaning new life. It's much shorter than the other two. It's quite a bit shorter than the Cretaceous alone. It's divided into three peroids, the Paleogene, the Neogene, and the Quaternary. I think. The definitions shift around a lot. These periods are divided into seven epochs between them, which I think get more use than the periods, but I don't want to describe all those. I haven't done a lot of research on the Cenozoic, but let's see what I remember.
The Paleogene period, which lasted from 66 to 23 million years ago, is when the continents really started looking like flooded versions of themselves. The sea level was higher because there was no ice at the poles. Mammals, which were, at the start of the period, small rodent-like creatures, evolved into a lot of different forms, including recognisable ancestors of just about every mammal alive today. Grass evolved during this time, unless it evolved in the Cretaceous. It's not clear. Antarctica drifted so far to the south that it started to be permanently frozen, creating a current around the continent that sped up the freezing process.
The Neogene lasted from 23 to 2.5 million years ago. I don't have a lot to say about it. Mammals continued to evolve, starting to look like they do now. The climate cooled down some more. Towards the end, South America became attached to North America, allowing the animals to cross over and resulting in some extinctions, especially in South America. Never say that humans are the only animals that mess up their environments.
The Quaternary period started 2.5 million years ago, and isn't on the timeline I posted earlier because its place in palaeontology was being redefined when I made it. So its current classification is fairly new. A couple of important things happened at the start of the Quaternary: an ice age started, the first since the Permian, and early humans evolved, although human ancestors diverged from chimpanzee ancestors about five million years ago. Since more water was locked in ice, sea levels were lower, and all the major landmasses of the world were connected, except for Australia, which is why Australian wildlife is so different from the rest of the world. The climate cycled between almost a third of the land being covered by ice, and only the poles being covered by ice, but both are considered an ice age. Early on, life was more or less the same as it is now, but with more giant animals.
Modern humans evolved in Africa about 200,000 years ago, and spread all over the world, reaching Australia by 40,000 years ago, and America by 14,500 years ago. It was around this time that a lot of the giant animals became extinct, maybe from hunting, or another rock. Then the glaciers receded to the poles again, giving humans the chance to develop agriculture and then the Internet. And then now happened.
The only thing that really startled me is when you say dinosaurs were reptiles. I remember in primary school how the big mistake not to make was saying dinosaurs were reptiles... Did that change?
Also, I like how you go from agriculture to the Internet :P But I guess it did happen that fast.
The only thing that really startled me is when you say dinosaurs were reptiles. I remember in primary school how the big mistake not to make was saying dinosaurs were reptiles... Did that change?
Also, I like how you go from agriculture to the Internet :P But I guess it did happen that fast.
It really did, at the pace I was going.
Dinosaurs were definitely reptiles, and as far as I can tell, were always considered reptiles. Maybe you're thinking of lizards? Dinosaurs weren't lizards.
Actually, modern birds are considered dinosaurs by... someone with authority, I guess, and they're not reptiles.
Dinosaurs were definitely reptiles, and as far as I can tell, were always considered reptiles. Maybe you're thinking of lizards? Dinosaurs weren't lizards.
Actually, modern birds are considered dinosaurs by... someone with authority, I guess, and they're not reptiles.
Isn't the word Dinosaur derived from latin meaning Monstrous Lizard. I guess the Lizard part could mean reptiles also, not knowing whether the Romans had a word specifically for Reptile. Though from this I would say that the person calling birds Dinosaurs would be entirely incorrect.
Well, I might be totally wrong on that since I'm basic it on memories from close to 20 years ago, but I remember something about dinosaurs being something different that doesn't exist anymore, and that they weren't reptiles because they weren't cold-blooded, or something similar.
I definitely don't think I'm mixing it up with lizards, I mean of course they're not lizards, they don't look like lizards at all to begin with, so I don't see why we'd be told specifically to avoid confusing them for lizards.
According to whatdino, they are a sort of reptile. The name means terrible lizard, but the name is WRONG. Curious little thing to think about: how do they know what colour each dinosaur was?
Curious little thing to think about: how do they know what colour each dinosaur was?
I've wondered about that, and my conclusion was: they don't.
I mean, if they didn't even know until recently that some of them were covered in feathers, I can't imagine they'd know what colour they were.
I've wondered about that, and my conclusion was: they don't.
I mean, if they didn't even know until recently that some of them were covered in feathers, I can't imagine they'd know what colour they were.
True, but we can take reasonable guesses. For example, they'd probably want to blend in with the environment, so shades of green are likely in foresty areas.
Yeah, I'm assuming they weren't pink with green stars on them. I assumed that shades of greens and browns are usually used because they just make the most sense, as you said, to blend in the environment and stuff.
Although I'm not sure they would all have needed to camouflage, either.
It IS awesome, but feathers are conserved for longer than skin, right? So it doesn't seem that they'll be able to figure out skin colour in the same way.
As far as I'm aware, they guess at the colours by a strange process of second-guessing evolution. Those that were vicious and lived by scaring other dinosaurs away would have evolved equally striking and bright colours. Those that were slow moving and lived defensively would have been camouflaged. Something like that anyway
As far as I'm aware, they guess at the colours by a strange process of second-guessing evolution. Those that were vicious and lived by scaring other dinosaurs away would have evolved equally striking and bright colours. Those that were slow moving and lived defensively would have been camouflaged. Something like that anyway
Are you trying to suggest dinosaurs weren't all pearlescent green with go faster stripes, I sure hope you aren't!
Oh my no, I'm just suggesting that, if that is the case (which it probably is), there would also have been pearlescent green forests with go faster stripes.
The colors in Hubble images, which are assigned for various reasons, aren't always what we'd see if we were able to visit the imaged objects in a spacecraft. We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye.
So maybe it's more a case of the clouds in the Hubble image being "painted" in the style of the master classical artists.
It's undeniable that classical paintings, especially those based on Shakespeare or Greek myth, do use that coloring and tone (?) in their work, though.
For example, the clouds and smoke in the background. Not just the intensely-lit, sunset ones:
In other news, the Mars rover Spirit is hibernating.
The article says "Spirit skipped a planned communication session on March 30"... they make it sound like Spirit went out the night before, had a few too many beers, woke up in the morning with a raging hangover and thought "Screw you, NASA!" before going back to sleep.
Reminds me of this xkcd comic that breaks my heart... poor Spirit.
I saw that. It was always odd to me that elements 116 and 118 were already synthesized, but element 117 wasn't. Well, that's fixed.
The interesting thing is that the seventh period of the table is now full. Element 118 is equivalent to a noble gas. Any new elements from this point on will have new shell levels (and starting after element 120, a completely new shell, the g-block).
A topic that hasn't got a reply in two hours is not dead.
And the link you posted was awesome. I'm especially interested in what discoveries like this mean for the possibility of life on other planets. I'm hoping that life on Mars will be discovered soon. That asteroid from 1996 that people were excited about because it looked like it had bacteria fossils was re-examined last year, and now they think that the formations really are bacteria fossils, even though they're a lot smaller than terrestrial bacteria. Wikipedia link.
Oh man: scientists discover first multicellular life that doesn't need oxygen.
I don't see why that's a big deal. Everyone always talks about how life forms couldn't exist in X place (different planets, underwater, etc.) because there's no oxygen or whatever else there. In my opinion, that doesn't mean that life can't exist there, it just means that our life can't exist there.
But we don't know if that kind of life could exist or evolve naturally, which is why discoveries like these are important.
I agree, though. It's ridiculous to say that life can't exist on other planets because humans wouldn't have evolved there. Of course life is fined tuned to Earth. That's the whole point of natural selection.
I don't see why that's a big deal. Everyone always talks about how life forms couldn't exist in X place (different planets, underwater, etc.) because there's no oxygen or whatever else there.
It's a big deal because it proves how short-sighted such people are...
I agree completely. Extreme temperatures and pressures, lack of oxygen, water etc. does not preclude the possibility of life, it just means that the types of life we are familiar with couldn't live there. Given the variety and number of extremophile species just here on Earth should indicate that life could possibly exist at almost any place where there's energy available.
It sounds amazing (and a tad dangerous in future applications), but it's not really as huge an advance as it's made out to be. We were already replacing genes with that from other animals (e-coli and the human insulin gene fro example), and we could form DNA stands. This is merely combining the two and taking it to the next level . It's a significant step, but theres still along way to go, like entirely synthetic life (from chemicals).
Comments
Yes! wonderful! Though it is hard to think of turning alcohol into 'wet' alcohol, so I prefer explaining it like this:
If you have a measuring cylinder and fill it with pebbles up to 50ml, then fill it with sand, the sand flows in between the pebbles and so for a while the reading of 50ml doesn't change.
While water and alcohol both look the same, they differ by quite a bit in terms of size and shape, so when you pour water onto alcohol, some of it manages to get "in between" just as the sand went in between the pebbles.
50ml+50ml=96ml
Edit: This is why you end up with a bucket of wet sand. The water goes in between the sand. Also, this is why when you pour milk into tea, you use more milk than you'd have expected to fill up the mug.
Yeah, just joking about my being out of my element in this thread.
Sadly, I would kill him just to make me remember the worst year and a half I had in my life (While having aproved the signature in the second test out of 3 at the end somewhat fixed ^^!)
I remember reading a metaphor about how you should organise your time.
First you put the big things you have to do, they're the big pebbles, in a mug (that's your agenda).
With these few big things in there, you add smaller pebbles for the smaller things you have to do.
Then you can add sand for the more trivial thing you have to do, which will just fit in between/around the others.
And finally, you put water in it, which means you need to remember to grab a drink with your friends.
But if you manage your time but starting with the small things, well then the big pebbles won't all fit in the mug where the sand already is.
But once you've set time for the big, important things, you'll have lots of time left for the rest.
Well, that's not really science, but it uses the scientific thing you mentioned :P
I can quote this show all day.
(First post here)
The current eon, the Phanerozoic, meaning "abundant life" or "life appears", I think, began 542 million years ago, when animals evolved shells and bones, which made it a lot easier to find their fossils when these things were being defined.
The Phanerozoic is divided into three eras, the Paleozoic, the Mesozoic, and the Cenozoic. They can be described as the age of fish, the age of reptiles, and the age of mammals respectively, which is sort of accurate. I forgot where I read those descriptions, though.
The Paleozoic, which means "ancient life", is divided into six periods. Almost all of them are named after places, mostly in Britain. I usually think of the first three as being before animals came on land and the second three as being after, although that's only true for animals with backbones.
The first period of the Paleozoic was the Cambrian, which lasted from 542 million years ago to to 488 million years ago. Lots of stuff evolved at the start of the Cambrian, including early chordates (animals with backbones), early arthropods (bugs and crustaceans), and early molluscs. The chordates were mostly fish, and the arthropods were mostly trilobites, which were probably the first animals to evolve eyes. And there were jellyfish and a bunch of different varieties of worm, but they're not very interesting. All this happened in the ocean. Not much was happening on land. I think there were a few bacteria. The sudden emergence of all these different kinds of life is called the Cambrian explosion, because it happened so suddenly.
The next period was the Ordovician, and it lasted from 488 to 444 million years ago. I know two things about the Ordovician: a lot of the planet was covered in warm shallow seas, and that this was when sea scorpions evolved. Sea scorpions were arthropods, but they weren't really related to modern scorpions. They were large predators that lived in water; one was the size of a crocodile and was the biggest arthropod of all time.
The reason that things can't grow beyond a certain size is that their weight goes up by the cube of their size, but things strengthening them, like muscles, go up by the square of their size. So if it was four times as heavy, it would only be twice as strong, for example. And if it was three times as strong, it would be nine times as heavy. This is why ants can easily lift their own weight and humans can't. It's called the square-cube law. But sea scorpions lived underwater, so weight wasn't as much of a problem for them. That's also while giant squid and whales can get so big now.
The Ordovician ended with a few extinction events that, taken together, were worse than the extinction that killed the dinosaurs. They were probably caused by an ice age, but some people think it was a gamma ray burst - a flash of gamma rays, which is the deadliest kind of radiation, from a distant exploding star. All the observed gamma ray bursts so far have happened outside our galaxy, but if one happened nearby today, it would be... really bad.
Anyway, the next period was the Silurian. It lasted from 444 to 416 million years ago, and is the period when life really started to invade the land. The first land dwelling plants appeared about 425 million years ago, and arthropods, including the relatives of spiders and centipedes, probably appeared on land at about the same time. No vertebrates yet, though.
The Devonian period (416 to 359 million years ago) was when fish evolved legs and left the water, which happened about 397 million years ago, about halfway through the period. Once they started living partly on land, they weren't fish anymore, they were amphibians. They still had to return to water to lay their eggs, though. Also of note: Giant fungi. They were called Prototaxites, and they grew up to 8 metres (26 feet) tall.
The first trees also evolved during this period, creating the first forests. There was another mass extinction at the end of the Devonian, which mostly affected life in the ocean. It's not clear how it happened, but this is when trilobites began to decline after dominating the oceans for hundreds of millions of years.
The Carboniferous period (359 to 299 million years ago) is kind of underrated, in my opinion. Forests spread over most of the land, except for the land at the south pole, which was covered in ice at the time, kind of like now. Since coal comes from dead trees, a lot of coal is found in Carboniferous rocks; the word Carboniferous means coal-bearing. The forests converted a lot of carbon dioxide in the atmosphere to oxygen, raising the oxygen levels to more than one and a half times what they are today. Instead of killing things horribly like in the oxygen catastrophe, it just made giant bugs possible. Arthropods before and after are small because their method of breathing isn't very efficient, meaning that they can't exert themselves as much as we can. I think. Because there was more oxygen in the air, arthropods could to transport more air around their bodies with less effort, making it possible for them to grow bigger. Winged insects evolved during the Carboniferous, and some got especially big, with one species of griffinfly, Meganeura, having a wingspan of up to 75 centimetres, or 2.33 feet. Griffinflies were basically giant dragonflies, and they were probably the birds of this period. There were also giant centipedes that were 2.6 metres (8.5 feet) in length, giant scorpions that reached up to 1 metre (3.3 feet) and giant cockroach ancestors which were about three centimetres (1.2 inches). The last one doesn't sound like much compared to the others, but it's still far too big for a cockroach. But at least ants hadn't evolved yet, and what was thought to be a giant spider turned out to be a sea scorpion that looked like a spider.
During the Carboniferous, some amphibians evolved the ability to lay hard shelled eggs on land, and became reptiles and synapsids, which are like reptiles except they eventually evolved into mammals. The biggest difference between synapsids and reptiles is their teeth. Reptiles have teeth that are identical to each other, and synapsids had different teeth in different parts of their mouth, like mammals do. Other amphibians became successful predators resembling crocodiles. Pangea, the supercontinent made from every major landmass on Earth, also formed during the Carboniferous.
Oxygen levels were back down by the next period, the Permian (299 to 251 million years ago), though they were still higher than they are today. The larger giant bugs died out, but the cockroaches got a bit bigger. The reptiles and synapsids began to dominate as land animals, mostly replacing the amphibians. The Dimetrodon, an animal commonly mistaken for a dinosaur, actually lived in the Permian. Dimetrodons were synapsids, so they weren't even closely related to dinosaurs, which were reptiles, and they're most well known for having sails on their backs, which probably evolved to help warm them up.
The most significant thing about the Permian is the mass extinction that happened at the end of it, which is informally known as the Great Dying. It was much worse than any other extinction currently known, and killed off just about every land animal with a backbone except for a piglike synapsid, Lystrosaurus. Other land vertebrates did survive, or there wouldn't be any reptiles or amphibians today, but Lystrosaurus dominated to an amazing extent. It was devastating to the ocean as well, killing off the remaining trilobites, and even affected the insects, which is unusual. It's not clear what caused it, but I like the theory that trapped underwater methane was released into the atmosphere, causing global warming and reducing the amount of oxygen in the air and water, both choking and baking everything. Or it was a gamma ray burst again. There's lots of theories about it.
And that was the end of the Paleozoic era. The next one was the Mesozoic, which is the one with the dinosaurs. It's only divided into three periods, the Triassic, the Jurassic, and Cretaceous, as it was quite a bit shorter than the Paleozoic.
The Triassic lasted from 251 million years ago to 200 million years ago, and its name refers to the three different layers of rock from the Triassic, or something. I'm not really sure about that. Unlike the later periods of the Mesozoic, the Triassic was quite dry. Life was also less diverse than usual during the first half of the period. It took a long time to recover from the mass extinction at the end of the Permian, much longer than it did from any of the others. Dinosaurs evolved about halfway through the Triassic, but they didn't dominate. Mammals evolved a few million years later, and stayed small and nocturnal. Pterosaurs, the flying reptiles often mistaken for dinosaurs, also evolved in the Triassic.
The Triassic ended with another mass extinction, but it wasn't as bad as the one that started it. It hit synapsids, amphibians, and some kinds of non dinosaur reptiles hard, allowing the dinosaurs to evolve into the roles that the other animals left behind.
The Jurassic period (200 to 146 million years ago) was when the dinosaurs really started to dominate. Pangea began to break up, and the climate was a lot wetter. These things were probably partly related - it's usually drier in the middle of a continent than on the coast. This is the period where the long necked dinosaurs like Apatosaurus and Diplodocus did the best. This is also when Stegosaurus, my favourite dinosaur when I was seven, was around. Some groups of Ocean dwelling reptiles often mistaken for dinosaurs also evolved in Jurassic. Near the end of the period, some of the smaller dinosaurs- the t-rex shaped ones- evolved feathers, and some of them evolved into birds. Most carnivorous dinosaurs from then on probably either had feathers, or had ancestors who had feathers.
The Cretaceous period lasted from 146 to 66 (I'm rounding up here, it's really 65.5) million years ago, and means "chalky". It was a lot like the Jurassic, but it lasted for eighty million years and had less giant long necked dinosaurs who laughed at the square-cube law. Most of the well known dinosaurs and animals mistaken for dinosaurs lived in the Cretaceous, including Tyrannosaurus rex and Triceratops, which even lived at the same time (right before all the dinosaurs went extinct) and the same place (North America, where all the most famous dinosaurs seem to be from. Probably not a coincidence). Flowers evolved during the Cretaceous, which led to flying insects becoming more diverse to take advantage of them. The earliest flowers probably smelled like rotting meat.
A couple of million years before the end of the Cretaceous, there was a series of volcanic eruptions which choked the air with poisonous gas, which was not good for the animals, but they probably would've been fine eventually, if a giant rock hadn't slammed into the Earth at the end of the period. This caused a fireball and shockwave that killed nearby life instantly, and threw up enough dirt to block out the sun for a year, and to keep it dim for a few years after that. Without the sun, the plants died, without the plants, the herbivores died, and without the herbivores, the carnivores died. Some omnivorous and insectivore animals like mammals and birds survived. So did some water dwelling reptiles, like crocodiles and turtles.
The current era is the Cenozoic era, meaning new life. It's much shorter than the other two. It's quite a bit shorter than the Cretaceous alone. It's divided into three peroids, the Paleogene, the Neogene, and the Quaternary. I think. The definitions shift around a lot. These periods are divided into seven epochs between them, which I think get more use than the periods, but I don't want to describe all those. I haven't done a lot of research on the Cenozoic, but let's see what I remember.
The Paleogene period, which lasted from 66 to 23 million years ago, is when the continents really started looking like flooded versions of themselves. The sea level was higher because there was no ice at the poles. Mammals, which were, at the start of the period, small rodent-like creatures, evolved into a lot of different forms, including recognisable ancestors of just about every mammal alive today. Grass evolved during this time, unless it evolved in the Cretaceous. It's not clear. Antarctica drifted so far to the south that it started to be permanently frozen, creating a current around the continent that sped up the freezing process.
The Neogene lasted from 23 to 2.5 million years ago. I don't have a lot to say about it. Mammals continued to evolve, starting to look like they do now. The climate cooled down some more. Towards the end, South America became attached to North America, allowing the animals to cross over and resulting in some extinctions, especially in South America. Never say that humans are the only animals that mess up their environments.
The Quaternary period started 2.5 million years ago, and isn't on the timeline I posted earlier because its place in palaeontology was being redefined when I made it. So its current classification is fairly new. A couple of important things happened at the start of the Quaternary: an ice age started, the first since the Permian, and early humans evolved, although human ancestors diverged from chimpanzee ancestors about five million years ago. Since more water was locked in ice, sea levels were lower, and all the major landmasses of the world were connected, except for Australia, which is why Australian wildlife is so different from the rest of the world. The climate cycled between almost a third of the land being covered by ice, and only the poles being covered by ice, but both are considered an ice age. Early on, life was more or less the same as it is now, but with more giant animals.
Modern humans evolved in Africa about 200,000 years ago, and spread all over the world, reaching Australia by 40,000 years ago, and America by 14,500 years ago. It was around this time that a lot of the giant animals became extinct, maybe from hunting, or another rock. Then the glaciers receded to the poles again, giving humans the chance to develop agriculture and then the Internet. And then now happened.
Also, I like how you go from agriculture to the Internet :P But I guess it did happen that fast.
Dinosaurs were definitely reptiles, and as far as I can tell, were always considered reptiles. Maybe you're thinking of lizards? Dinosaurs weren't lizards.
Actually, modern birds are considered dinosaurs by... someone with authority, I guess, and they're not reptiles.
Isn't the word Dinosaur derived from latin meaning Monstrous Lizard. I guess the Lizard part could mean reptiles also, not knowing whether the Romans had a word specifically for Reptile. Though from this I would say that the person calling birds Dinosaurs would be entirely incorrect.
I definitely don't think I'm mixing it up with lizards, I mean of course they're not lizards, they don't look like lizards at all to begin with, so I don't see why we'd be told specifically to avoid confusing them for lizards.
According to whatdino, they are a sort of reptile. The name means terrible lizard, but the name is WRONG. Curious little thing to think about: how do they know what colour each dinosaur was?
I've wondered about that, and my conclusion was: they don't.
I mean, if they didn't even know until recently that some of them were covered in feathers, I can't imagine they'd know what colour they were.
True, but we can take reasonable guesses. For example, they'd probably want to blend in with the environment, so shades of green are likely in foresty areas.
Although I'm not sure they would all have needed to camouflage, either.
And this thing that I said earlier on the thread is relevant now:
Are you trying to suggest dinosaurs weren't all pearlescent green with go faster stripes, I sure hope you aren't!
The meaning of colour in Hubble images
So maybe it's more a case of the clouds in the Hubble image being "painted" in the style of the master classical artists.
It is a gorgeous picture though.
Thanks for that link. I liked it!
It's undeniable that classical paintings, especially those based on Shakespeare or Greek myth, do use that coloring and tone (?) in their work, though.
For example, the clouds and smoke in the background. Not just the intensely-lit, sunset ones:
In other news, the Mars rover Spirit is hibernating. Mo-fo robots fallin' asleep. They gonna be reproducing next and then it's Terminator 2.
The article says "Spirit skipped a planned communication session on March 30"... they make it sound like Spirit went out the night before, had a few too many beers, woke up in the morning with a raging hangover and thought "Screw you, NASA!" before going back to sleep.
Reminds me of this xkcd comic that breaks my heart... poor Spirit.
The interesting thing is that the seventh period of the table is now full. Element 118 is equivalent to a noble gas. Any new elements from this point on will have new shell levels (and starting after element 120, a completely new shell, the g-block).
This is troubling.
And the link you posted was awesome. I'm especially interested in what discoveries like this mean for the possibility of life on other planets. I'm hoping that life on Mars will be discovered soon. That asteroid from 1996 that people were excited about because it looked like it had bacteria fossils was re-examined last year, and now they think that the formations really are bacteria fossils, even though they're a lot smaller than terrestrial bacteria. Wikipedia link.
I don't see why that's a big deal. Everyone always talks about how life forms couldn't exist in X place (different planets, underwater, etc.) because there's no oxygen or whatever else there. In my opinion, that doesn't mean that life can't exist there, it just means that our life can't exist there.
I agree, though. It's ridiculous to say that life can't exist on other planets because humans wouldn't have evolved there. Of course life is fined tuned to Earth. That's the whole point of natural selection.
I agree completely. Extreme temperatures and pressures, lack of oxygen, water etc. does not preclude the possibility of life, it just means that the types of life we are familiar with couldn't live there. Given the variety and number of extremophile species just here on Earth should indicate that life could possibly exist at almost any place where there's energy available.
It sounds amazing (and a tad dangerous in future applications), but it's not really as huge an advance as it's made out to be. We were already replacing genes with that from other animals (e-coli and the human insulin gene fro example), and we could form DNA stands. This is merely combining the two and taking it to the next level . It's a significant step, but theres still along way to go, like entirely synthetic life (from chemicals).