Drive by science

[Ari]

Phlogiston!
In the 1700s the prevailing theory was that things had some substance or property called Phlogiston which is what burned. Objects lost Phlogiston to the air when burned and others like plants could absorb it back from the air to become combustible. Wood for example was considered part ash and part Phlogiston.

Ironically they did discover 'oxygen' but considered it dephlogistonated air which had the ability to pull phlogiston from the air and thus burn for longer. One of the nails in the coffin came when nitrogen was isolated as the main component of air and it turned out to be inert. Another was that some metals gain mass when burned, which couldn't be explained easily with phlogiston especially since by that time it was considered a physical thing which had mass and not just an ethereal property.

[JoeP]

That completion figure, which goes up to 100%, is that saying that there can't be any more elements?

[JoeP]

Originally Posted by JoeP

That completion figure, which goes up to 100%, is that saying that there can't be any more elements?

That's a good point JoeP. In fact it isn't known whether there are more elements, but there's no good reason why there shouldn't be.

See Further periodic table extensions at Wikipedia.

[Kamilah Hauptmann]

So. Joepium up next?

[JoeP]

There are other ways of laying out the periodic table ...

[JoeP]

Originally Posted by Kamilah Hauptmann

So. Joepium up next?

Joepium is reserved for element 666.

[But]

This "discovery" business is ambiguous, especially in a time where you had a mishmash of ideas and all sorts of different ways you could interpret the results of experiments. The discovery of oxygen can be dated up to 170 years earlier than given here (Sendivogius and John Mayow among others).

[ceptimus]

I think the dates on the graphic I linked to are when a substance, which we now know to be an element, was first isolated.

So the elements that exist in pure form on Earth naturally - such as gold, sulphur (near volcanos), carbon (diamonds), and iron (meteorites) are classed as ancient discoveries - even though the ancients didn't really have the modern concept of an element.

There are other things the ancients isolated that we now know to be compounds - such as common salt (sodium chloride) - and if that had turned out to be an element that would be classed as an ancient discovery too.

Regarding Oxygen, as Ari said, until Lavoisier and Dalton figured it out and isolated it, scientists had a pretty good concept of something needed for combustion and life - but they had the notion of a combustible component being present in things that would burn, and they called that component phlogiston. So when you burned a fuel, its phlogiston part was given off and what was left behind (ash) was called the dephlogisticated part. It made a sort of sense as the ash usually weighs much less than the original fuel - and things that burned leaving virtually no ash were thought to consist of almost pure phlogiston.

It was when chemists were trying to isolate and weigh phlogiston, and for greater accuracy taking the trouble to also catch and weigh the smoke and gases as well as the ash, that they found phlogiston had a negative weight and then realized that their theory was wrong and the idea of Oxygen was born.

Those old chemists weren't so stupid. People guessed the wrong way about electric charge too, and we've stuck with the (wrong) notion - we still say electric current flows through a wire from positive to negative even though we now know that it's actually negatively charged electrons that are flowing in the opposite direction.

[Ari]

Originally Posted by JoeP

That completion figure, which goes up to 100%, is that saying that there can't be any more elements?

Kinda.
Labs are bumping up against distances of forces when making new elements. The electrically repulsive protons only stick together because at those close distances the strong force is much stronger than the electromagnetic force. Neutrons act as a kind of extra glue adding some more strong force but no charge. At a certain size though the nucleus is going to be too big for the strong force to hold everything together and it's going to blow itself apart.

There's been a conjecture for awhile that there's an 'island of stability' out there somewhere where forces once again counteract each other at a massive nucleus size, but so far there's no evidence it exists.

It does mean at a certain point we will end up with 'artificial' elements, ones that can only form because they are being actively forced and held together by some outside apparatus. Even now there are elements that we've made but aren't considered elements because they existed for so short of a time that no tests or readings could be done. However the last stable element was quite a few elements ago and virtually everything getting added to the end exists only in unstable isotope form.

This is all not the end though, as this is only one of the many periodic tables we assume exist out there with other configurations.

[But]

Originally Posted by ceptimus

Regarding Oxygen, as Ari said, until Lavoisier and Dalton figured it out and isolated it, scientists had a pretty good concept of something needed for combustion and life - but they had the notion of a combustible component being present in things that would burn, and they called that component phlogiston.

But that's not so wrong either - often it is present in the combustible material, in a form like nitrate, which both Sendivogius and Mayow identified as a source of the very specific substance they were talking about and which was oxygen. They were almost certainly aware of the fact that gunpowder burns without air.

[Ari]

Originally Posted by ceptimus

People guessed the wrong way about electric charge too, and we've stuck with the (wrong) notion - we still say electric current flows through a wire from positive to negative even though we now know that it's actually negatively charged electrons that are flowing in the opposite direction.

Indeed, Phlogiston still persists in a way when we say "oxidation" as if combustion is a physical object instead of an interaction between molecules. Oxidization being the process of giving up an electron to another chemical, happens all the time with other things that aren't oxygen.

We still use old naming conventions, combustion is a redox reaction, which at one point specifically meant something was reduced in weight by losing oxygen and oxidation where something gained oxygen. We know now it's about the process of electron transfer and that oxygen is just the most commonly violent electron thief and burning is the result of that thievery but both combustion and redox reactions happen with other chemicals.

(This also starts to explain why water is likely to form in chemical reactions, oxygen sees hydrogen as a spare electron carrier that can be easily pushed around.)

[BrotherMan]

Originally Posted by Kamilah Hauptmann

So. Joepium up next?

[Ari]

How does a whip break the sound barrier? Find out through slow motion shockwave imaging.

How does a whip break the sound barrier? (Slow...

[The Lone Ranger]

Related to the above, many of the large sauropod dinosaurs such as Apatosaurus and Diplodocus had very long tails that tapered to very thin tips. For a long time, why their tails would be so extraordinarily long was a mystery.

Diplodocus longus displaying its very long tail.

Recent research suggests that some sauropod species, at least, could use their tails as whips to deter would-be predators. The question then becomes: "Could they actually create sonic booms with their tail tips?". Even if the tail tips didn't move that fast, given how the displacement wave would accelerate as it moved down the length of a sauropod's tapered tail (for the same reason that the wave accelerates as it moves down the length of a whip), the tail tip would have been moving very fast when a sauropod lashed its tail. Fast enough that if a sauropod could land a hit on an attacking theropod such as Allosaurus, the tail tip would probably be capable of cutting through skin and muscle, causing serious injuries.

Computer modeling has suggested that species such as Apatosaurus louisae were, in fact, capable of lashing the tail like a whip and accelerating the tip to supersonic speed -- and thus, creating a sonic boom.

Tests with scale models have confirmed this. So yes, some sauropod dinosaurs were apparently capable of using their tails as whips to deter predators.

A scale model of an Apatosaurus louisae tail, demonstrating that if the animal lashed its tail, the tip could reach supersonic speed.

Neat!

[JoeP]

That is awesome.

[ceptimus]

When you crack a whip, it puts a lot of stress on the tip - which tends to wear out and break pretty quickly. If you're trying to get a loud crack from a whip, the tip is fitted with a 'popper' or 'cracker' which is usually a bit of string with the ends frayed out into separate strands - these delicate items suffer even more than a plain leather whip tip, and often you see threads falling off with each crack.

I wonder what the dinosaurs had on the tips of their tails? Maybe some fairly fast growing stiff hairs or feathers, so they could make nice loud cracks - the hairs or feathers would suffer inevitable damage with each crack, but that wouldn't matter too much as they would quickly regrow.

Shorter tails wouldn't be able to produce a supersonic crack, so there must have been some evolutionary advantage for tails growing longer anyway. Once the tails evolved to the point where they could be cracked, that must have conferred a survival advantage on the individuals that could do it and then the species' tails would continue to evolve to make them easier to crack and to produce ever louder more impressive cracks.

Baby dinosaurs wouldn't be able to crack their (shorter) tails, and I guess it was a significant right of passage into adulthood when an individual dinosaur grew large enough to produce its first crack.

[The Lone Ranger]

Yup. It's generally thought that the long tails were used to defend themselves against predators, but certainly, evolution couldn't have predicted that if you just made the tail long enough, it would be possible to crack it like a whip.

The hypothesis is that even if the tail tips didn't get anywhere close to the speed of sound, they'd still move fast enough to be effective weapons. As such, selection pressure for increasing tail length would be due to longer tails being more effective weapons.

Of course, even if it were possible for them to create sonic booms with their tail tips, that doesn't mean that they typically -- or ever -- did so. After all, the tail would still be an effective weapon even if the tip never broke the sound barrier.


Alternately, the tails may have been used in dominance displays -- to impress rivals or potential mates, for example. Either way, a longer tail might be more impressive to a rival or to a would-be mate (due to runaway sexual selection, if nothing else), explaining why they grew to such great lengths.


Interestingly, about half of all the long-tailed sauropod fossils that have been found have damaged vertebrae in the distal portion of the tail. These are likely injuries from lashing their tails, where the stress in the distal tail region damaged the smaller, more delicate vertebrae there. This suggests that if these animals could use their tails as whips, they probably put their full effort into it only when sorely pressed, as doing so came with a significant risk of injury.

[JoeP]

Originally Posted by The Lone Ranger

Either way, a longer tail might be more impressive to a rival or to a would-be mate (due to runaway sexual selection, if nothing else), explaining why they grew to such great lengths.

...

This suggests that if these animals could use their tails as whips, they probably put their full effort into it only when sorely pressed, as doing so came with a significant risk of injury.

Or when very horny.

[Kamilah Hauptmann]

"Mine's bigger." -since 161 million BCE.

[JoeP]

New Horizons: Nasa probe survives flyby of Ultima Thule - BBC News

The New Horizons probe has passed 2014 MU69 also known as Ultima Thule, which now becomes the furthest body in the Solar System to have been visited by a manmade probe. The probe was travelling at 51,500 km/h and is about 6 light-hours away from Earth.

Pictures will be sent back over the next 20 months about 1,000 bits per second.

[Kamilah Hauptmann]

Because I know deep down in my salted caramel heart that every last one of you needs more of a Twitter firehose in your lives, here is a feed of climate scientists who Tweet.

@KHayhoe/scientists who do climate on Twitter

[JoeP]

:halfthanks:

[Kamilah Hauptmann]

[ceptimus]

Nasa's New Horizons: 'Snowman' shape of distant Ultima Thule revealed - BBC News

[JoeP]

Originally Posted by JoeP

New Horizons: Nasa probe survives flyby of Ultima Thule - BBC News

The New Horizons probe has passed 2014 MU69 also known as Ultima Thule, which now becomes the furthest body in the Solar System to have been visited by a manmade probe. The probe was travelling at 51,500 km/h and is about 6 light-hours away from Earth.

Pictures will be sent back over the next 20 months about 1,000 bits per second.

It's a snowman!



So it's both spherical and a binary object, the theories floated beforehand: a contact binary. It could have been like this for 4 billion years, not changing very much given the low temperatures, low radiation and low probability of impacts out there.

Nasa's New Horizons: 'Snowman' shape of distant Ultima Thule revealed - BBC News