Around 75% of all plant and mammal species were made extinct by the "K-Pg extinction event" that happened 66 million years ago. Very few large animal species (Wikipedia gives a maximum mass of 25kg) survived - some crocodiles and turtles being the exceptions.

While we tend to think of extinction events as being sudden and immediate (which they are on evolutionary or geological scales), the K-Pg extinction event is thought to have lasted anywhere from a few years to 10,000 years, before things stabilised (similar to the mass-extinction event the Earth is currently going through; hard to notice on a day-to-day basis or year-to-year, but definitely noticeable over thousands of years). A meteor didn't just crash and kill and the dinosaurs - a meteor crashed and caused massive, long-term changes to global climates and ecosystems that lasted thousands of years, and most large animal species didn't survive.

In terms of what happened, the main thing was anywhere up to 2 years of global darkness caused by all the dust and other matter thrown up into the sky by the initial crash. This would have killed off a huge chunk of plant life (which requires photosynthesis to live), as well as likely making things colder. Without plants, animals that lived off plants would gradually die off, and without them animals that lived off other animals would slowly die off - including the big super-predators and super-herbivores like the larger dinosaurs (who would have needed to eat a lot of stuff). Many individuals would survive for a while, maybe some generations, but over time the species wouldn't, as not enough would be around to maintain a stable population.

On top of that, you have a huge chunk of weird minerals and materials being thrown up into the atmosphere, to settle across the globe, some of which would be toxic to some animals and plants. There's also a good chance that some of these minerals settled into the oceans, significantly increasing the acidity of the oceans, making them uninhabitable for a lot of plants and animals, and generally messing up the world's water supply.

Things that survived were generally things with the ability to survive long periods without food (like crocodiles), things that lived off detritus (all the dead plant and animal matter caused by the destruction) like worms, snails and insects, and the smaller animals that lived off them (like the surviving birds and mammals).

And as the dust settled (both figuratively and literally) there was an explosion of diversity in life - with so many evolutionary niches now opened up, mammals in particular flourished, evolving in all sorts of new ways (including getting larger and smarter).

Some dinosaurs did survive. We just don't generally call them dinosaurs any more, but birds.

You can say "there is no solution." But that's boring.

Mathematicians don't like being told they cannot do something. Instead they try to come up with new rules or new definitions to do whatever it is there isn't already a rule for. And those rules can be anything, but generally we look for consistency (those new rules should complement or add on to existing rules), usefulness (the new rules should help us do something we couldn't do before), and interesting consequences (things that make us go "ooh, that's neat").

And the more useful, interesting and neat those rules are, the more likely they are to be used by other mathematicians, and adopted as standard.

With complex numbers, we take all our usual rules for numbers and throw in one more; there exists some number(s) i such that i^2 = -1. It is consistent with all our existing rules, and turns out to be really useful in a bunch of areas of maths and science (and leads to some really interesting results).

i isn't impossible. It doesn't appear on a standard number line, but that's not a huge problem. The number line is an interesting and useful tool, but not the end point of numbers. Interestingly the first mathematical paper to use something like a modern number line was published about the same time Newton was publishing his Principia Mathematica; there weren't number lines when Newton was learning maths. Number lines are fairly modern.

Some classical Greek mathematicians had a very different way of looking at numbers, seeing them more as a lose collection of concepts, with fractions being connections between the different concepts (so 1/2 was a connection between 1 and 2). This did cause them problems, though, when it came to irrational numbers...

Others are saying that they're circular, which they kind of are, but only in 2D. Rainbows are cones, with you at the point (and the centre of the cone lining up with your eyes and the Sun).

When you look at a rainbow, you're seeing light being reflected through water droplets that are somewhere in that cone. So it could be that two parts of the rainbow you see that are right next to each other are from water droplets miles apart, if some are much closer and some much further away.

The reason why they are cones involves a bit of physics and a bunch of geometry. Essentially the light from the Sun hits the raindrops and gets scattered out in all directions at an angle of about 40 degrees (that is just a 2D slice, imagine it being rotated around). So the scattered light comes out in a cone from each raindrop, and by geometry and symmetry, the light from a bunch of different raindrops that hits any given point (i.e. your eyes) forms a cone of itself.

Firstly, thinking of gravity as a force is a fairly decent way of understanding it. The model breaks down in some situations, but is not bad most of the time. Gravity as a force is a helpful lie, which is why we teach it.

The GR way of looking at gravity is as curvature in spacetime. Essentially the presence of energy/mass squishes space and time together around it, meaning that there is "more space per space" close to a massive object, and "less time per time" (time passes slower).

One way of thinking about falling is that this effect twists an object's time direction a bit into its space directions. The object falling is sitting where it is doing its normal thing, staying still and going forwards through time at 1 second per second. But from an outside perspective it is going forward through time at a bit less than 1 second per second, and is also moving downwards a bit, because its "forward through time" direction is an outsider's "forward through time and a bit down" direction [disclaimer; this isn't quite how the maths works, but is a helpful analogy].

A more massive object has more of a twisting effect on spacetime, so this is a bigger deal for more massive objects. It's also a bigger deal closer to massive objects than further away; acceleration due to gravity is about 9.81 metres per second-squared near the surface of Earth, but it drops the higher up you get. It is about 90% of that on the International Space Station, for example.

I'm not entirely sure what you are saying about accelerations of objects. It is possible to mimic the effect of gravity by being in an accelerating reference frame - that is kind of what a g-force is (which is not due to gravity, and not a force - great naming there, guys!). But in that case we're simulating the effects of gravity - depending on the acceleration we can vary the fake-gravity's strength.

> let's say I was traveling in a car going 120 mph and I wanted to decelerate to 90 mph. This would take four times as much energy than going from 30 mph to 0.

> But let's say there were two cars traveling at 120 mph. The car next to me decelerates to 90 mph, but I'm still going 120. From my point of view, the car next to me just started going 30 mph in the opposite direction. Why would this require 4 times as much energy than if both cars were just stationary, and the car next to me actually started going 30 mph in the opposite direction?

This is a really fascinating question. And the answer takes a bit of thinking about, but you've already got the basics of it.

In classical mechanics (pre-20th century) energy is a mathematical tool that is useful in figuring out how things interact. It corresponds to how much something has been forced. The more it has been forced, the more energy it has gained. Because forces are symmetric (Newton's Third Law) the more one thing has been forced, the more other things have forced things; so we can factor this into energy. If one thing has been forced and so gained "been forced stuff" (energy) we can say that the things that forced it have lost "been forced stuff." We get conservation of energy!

If energy is conserved that can be really useful for understanding situations. Rather than having to worry about all the forces and interactions going on at each moment in some system, we can look at the energy at the start, look at the energy at the end, and you can get a great idea of what is happening.

Anyway. The important thing to note about this is that it is a maths thing; helpful, but has limitations. One of the big ones is that it depends on our frame of reference (which is what you've noticed). It isn't absolute, but relative. But that's Ok as we're only ever looking at how it changes, and it just means we have to be careful about switching between reference frames when doing energy calculations (but we should be doing that anyway).

So let's look at your situation.

Your car is going at 120mph. It want to decelerate to 90mph. That would involve losing more energy than you'd have to lose to decelerate from 90mph to 60mph, and 4 times as much energy as it would take for you to decelerate from 30mph to 0mph. But this is all from a reference frame fixed with the ground.

From your point of view, though, you're at rest. You're not changing speed, so no need for any change in energy at all! Of course, you're in a non-inertial reference frame, so the maths gets a bit weird, but this is a good indication that something weird is going on.

So let's look at another point of view. Some car that was travelling at the same speed as you before you started slowing down.

From their point of view you were going at 0mph, then sped up to 30mph (backwards), then sped up further to 60mph and eventually up to 120mph. From their point of view you have gained energy! This is getting really weird...

The big thing we're missing is that energy is being transferred; if something is gaining or losing energy, something else must be losing or gaining it. We're only looking at half the problem.

Let's massively oversimplify the problem and assume that as you slow down you are dumping energy into the Earth. Conservation of momentum tells us that as you slow down the Earth must speed up. So from our "with the ground" frame of reference, the Earth will be gaining energy as you lose energy.

But from the other car's point of view, as you "speed up" the Earth will "slow down," so as you gain energy, the Earth loses energy. Which is what we expect.

The maths gets a bit messy (and we have to worry about whole systems for conservation of momentum and conservation of energy) but it all works out in the end. Provided we do everything (including measuring distances and forces) from the just one reference frame. The calculations will be different and give us different changes in energy, depending on which reference frame we use, but we will get the same overall result for how things move.

Oddly enough, this is kind of how E = mc^2 was first derived; by looking at how energy changes work when viewed from different reference frames. Einstein's paper on it is only a couple of pages and is a simple thought experiment.

They can and do (although not quite in that way).

The main problem with it is that it devalues the currency. Money has no inherent value, so usually the effect of printing a load of money (or creating it on paper) is to decrease how much existing money is worth.

Simplifying a lot, the amount of actual worth or value stays the same (as nothing of actual has been created and no work has been done), but there are more dollars around, each dollar must be worth a bit less. And this leads to inflation which isn't necessarily a bad thing, but can be pretty disastrous if it gets out of control.

Yes... is that a problem?

Worth noting that the far-left Russian Government ended up spiralling into an authoritarian nightmare that killed a lot more people. Part of the problem with far-left politics is that if you don't have the support of the population you need to introduce all new power structures to force your lack of power structures on the people. And then you open the doors to all sorts of corruption and evil.

"Left" and "right" are fairly vague terms, used to split people into convenient political groupings. They are the continental-European versions, compared with the more British/American "progressive," "liberal" and "conservative" terms. They are all a bit vague due to the different political landscapes in different countries and at different times, and the terms (particularly "liberal") can have very different meanings in different places.

Roughly speaking, and generalising horribly:

• left-leaning people/progressives feel that power structures and social hierarchies are a bad thing, and that the role of society (via government) should be to remove them,

• right-leaning people/conservatives feel that power structures and social hierarchies are a good thing, and that the role of society (via government) should be to protect them.

• centrists/liberals may feel either way about power structures and social hierarchies, but don't think the government should interfere.

Then you have groups like anarchists and libertarians, and a few others, who tend to line up somewhere with the above but might disagree on the specifics.

With both left and right you get "centre-" "hard-" and "far-" etc. depending on how extreme they take their views. Far-right people and governments tend to be in favour of use of direct force to impose power structures (to the extremes of the 1930s-40s German Government which systematically killed millions of people who didn't fit in their ideal society), while far-left people and governments can do the same to abolish power structures (e.g. the 1920s Russian Government which killed a lot of nobility and religious leaders who were part of the existing power structures).

"Left" and "right" is mostly relative, though. A "left-wing" group in one country might have similar views to a "right-wing" group in another country, depending on where the "centre" is.

> I'll just add that Marx lived in the mid-1800s, in Germany,

Worth noting that in his 20s he was exiled from Prussia at the request of the Russian monarchy (for his articles critical of them), lived in Paris from 1843-1845 until the Prussian Government got him expelled from France and had his radial German-language (but Paris-based) newspaper shut down. He lived in Brussels until 1848, when he was expelled on allegations that he had helped fund Belgian workers planning a revolution, and he bounced between a post-revolution France and Cologne, until he was kicked out of both, moving to London in 1849, aged 30, where he lived until his death.

Marx's most famous works (Das Kapital and The Communist Manifesto) were both written in London.

Science isn't a perfect process; it is done by people, and people make mistakes. Things go wrong, people miss things, or they just get really unlucky.

Replication helps control for that.

You get a different set of people to do the same experiment in the same way, and you should get the same result. If you do, that's a good sign. If not, that's a problem and something that should be looked into.

Ideally then you get a different set of people do the same experiment in a slightly different way. And then a different experiment that measures the same thing, and so on. Lots of replication, all aimed at controlling for things people didn't think about or didn't spot.

Now you could get just one team to do this, over a long period of time, and include it all in a single study, but that is kind of inefficient. Better to do each study separately, then you can publish them individually and other people can have a chance to look at it as well. Plus it is generally a good idea to get a second person or team to work on something.

In a perfect science world you never stop experimenting on something. You never treat it as fully settled, you keep testing your idea until you disprove it, keep trying to find new ways to poke at it and experiment on it.

The Royal Navy usually has a ship or two hanging around the Caribbean, both to provide military support to the dozen British Overseas Territories in the region that the UK is responsible for defending, and to provide support (including search and rescue) to the various Commonwealth Realms and Republics, and other countries that the UK still has strong ties to (there is often a destroyer or amphibious assault vessel in the area during hurricane season).

The article says this took place near Dominican Republic, as part of a join operation with the US Coast Guard. The Dominican Republic is between Puerto Rico (part of the US) and the Turks and Caicos Islands (a British Overseas Territory), so it may be that the US Coast Guard began a pursuit in their waters and asked the British ship to help out.