The point you are replying to is that stainless steel is unnecessary, because 'normal' steel will ast more than 1000 years in the conditions described.
4,356 karma · joined April 24, 2012
We were repeatedly banned from playing "Stretch". 2 players stand facing each other with their feet together. They take turns throwing a knife into the ground, and their opponent must move the closest foot sideways so that it is in-line with the knife. If the knife doesn't stick in the ground the opponent puts their feet back together. First person to fall over loses.
I'm sure everyone had their own rules, and this was not that long ago (surely!) in Australia.
I am not an actuary, but I have done a lot of actuarial work in a small insurance company, and the work included
- pricing (are we under of over charging for this product?)
- reinsurance (analysis so we can get a good price, as well as making sure what we sell remains within our reinsurance coverage)
- portfolio monitoring (performance/profitability/etc)
- risk aggregation (do we have too much exposure to a single risk or type of risk)
- loss forecasting (primarily for reserving, but also for a 'true' indication of performance, as claims experience is necessarily very laggy)
- product development (for example, what does a travel insurance product look like in a COVID world? What can we reasonably offer and how do we assess the pricing/reinsurance/risk appetite)
Moreover, none of these tasks required nor employed any memorised formulas. You either use a model someone else built, or build one yourself, and then analyse and test as much data as you can so that you can provide good advice. Importantly you have to be able to show exactly how you produced that advice, and be ready to justify every single choice you made while doing so. A large part of the actuarial training seems to be ways of working and thinking that enable this (at least this is my impression from the actuaries I work with).
There are actuaries who just calculate '"Solvency II" formulas for "quarter end"', but there are also actuaries developing advanced risk models for catastrophic weather events using large data sets and machine learning, or shutting down products because the market has shifted and it's no longer viable. In every insurance company I've worked at, actuaries are some of the most influential and respected people there, and do very interesting work (along with some really mind-numbing work!).
The typical solution, which is in the context of relighting a liquid fueled rocket that is coasting in microgravity, is to use some other engine to push the fuel in one direction, providing enough initial ullage to light the main engine after which the thrust from the main engine provides the rest.
For refueling it is normally assumed that the target and resupplier are stationary when docked, or at least not accelerating to their next set of orbital parameters; they are station-keeping. The typical solution doesn't work there, so there is research to be done on just how the refueling will work in practice.
Here in Australia we held back from giving certain vaccines (the mRNA vaccines we have available here) to some demographics when the virus was suppressed here, until the risk from a new outbreak meant it was safer to get the vaccine than not. The adenovirus vaccine we have available was not held back in the same way.
The contention in this discussion, I think, is that we haven't established an absolute yardstick for an 'impeccable safety record'.
You rightly point out the adverse effects we're seeing from these new vaccines, and that they appear more frequent than adverse effects from past vaccines, but that doesn't make them significantly less safe.
Suppose we have an old vaccine that has adverse effects 1% of the time (this would be terrible, but still), and a new vaccine that has twice as many adverse effects. The old vaccine would be 99% safe and the new vaccine 98% safe - quite similar (though still terrible)!
When we start talking about the actual rate of excess adverse effects for the covid vaccines it's on the order of 10 per million doses [0]. Even if this is 10 times worse than old vaccines we're talking about vaccines that are 99.9999% safe vs 99.999% safe.
Based on the evidence we have these vaccines are extremely safe, and I would feel comfortable accepting the 'impeccable safety record' label even though I probably wouldn't choose it myself.
[0] https://www.health.gov.au/sites/default/files/documents/2021...
Is your position the rational position for them to take?
What is the motivation for your position?
The follow up was saying "the covid vaccine doesn't have a perfect safety record therefore it's not really impeccable is it!" while not comparing to other safe vaccines at all.
You can't use a broad definition in the original claim and then try and use a narrow definition when refuting counter claims.
Why do you expect this, and do you think it's a reasonable expectation? Do you shrug off flu vaccines because they're only effective for a year or so? (I understand the difference between reduction in efficacy over time against a single strain vs against new variations)
> While I'm vaccinated, I have not signed up for an endless stream of "boosters" every 6 months or so. Probably I'll be declared "unvaccinated" with a straight face and excluded from society in the not-so-far future.
I don't understand this point of view at all. Do you only take the first pill in a course of antibiotics? Why wouldn't you follow the vaccine schedule that offers the best overall protection, and best reduction in total risk, that we're aware of and is available to you?
The ecosystem impact is still super important to understand, but it's reasonable to think that other mosquitos, or similar insects, could fill the niche left behind.
This argument does not apply to the original example and it's an odd argument to make.
The biggest downside to using 'φ' over 'phi' is how hard the first is to type on most keyboards, and how it might be harder to google (although I just tested and copy+paste+search gives me the right answer immediately).
I'm a fan of reducing jargon, but this is a very standard symbol and I like its use in a codebase - especially one targeted at people studying mathematics.
I'm not sure if there has been much discussion on the topic here, but it's something I would definitely like to see changed.
At least there is no provision in the contract that I can't talk about provisions in the contract...
We use the label 'number' to refer to a broad swathe of mathematical objects, objects that are different but also so similar they often appear interchangeable (for example counting numbers and fractions).
In the formal mathematical sense, a specific type of number is a group of objects which have been defined to have specific properties. I'm going to leave object and property as defined in the usual sense, I think most people have a good idea about what those are and not sure I can add anything to them.
There are no rules as to what properties you are allowed to give to objects, nor what group of objects you want to include, but generally if you are learning about some specific thing it's because people find them useful or interesting; the definitions we have for different types of numbers are the ones we have found useful or interesting.
Remember that the different types of number appear very similar. It is common to build a 'hierarchy' of differnt types of numbers, where we start with a simple type of number and then add new properties and objects when we find limitations we don't want.
The first type of number in this hierarchy are the natural numbers (sometimes called counting numbers). The most common properties defined for these today are called the Peano axioms [0]. There are quite a few of them, and the history of how we came to the formalisation is very interesting (a lot of it is about avoiding inconsistencies/contradictions) but the key ideas are:
- there is a natural number called 0
- every natural number has a successor, which is also a natural number - we can write S(n) is the successor of n
Most of the other axioms define what it means for two natural numbers to be equal (=).
Just having these objects isn't particularly useful, we typically want to do things like add, multiply, and compare numbers. To do that we include some operations: addition (+), multiplication (*), and total ordering(<=).
These are defined as, taking a, b, c as natural numbers:
- a + 0 = a
- a + S(b) = S(a + b) (this is recursive, so if we define 1 as 1:=S(0) then we have 1+1 = 1+S(0) = S(1+0) = S(1))
- a * 0 = 0
- a * S(b) = a + (a * b)
- a <= b if (and only if) there exists some c such that a + c = b
Importantly, using these definitions, we can say that the natural numbers are closed under addition and multiplication; whenever you add or multiply two natural numbers together you get another natural number.
To continue building the hierarchy we notice that there are operations we would like to do but are not possible for every natural number (please note I am skipping over the formalisations from hereon and talking about the motivation for different types of numbers).
We notice that if we can add two numbers together we should be able to subtract them again. If a + b = c, then c - b = a. However (for example) 0 - 1 is not a natural number. So we extend the natural numbers to the integers, such that the integers are closed under subtraction.
If we can multiply it makes sense to try and divide, but 2 / 3 is not an integer so we extend integers to the rationals (ratios of integers) which are closed under division. We add an object called 2/3 so that now when we can say 2 / 3 = 2/3.
The next step in the hierarchy is a bit more complex. We notice that we can define a subset of rational numbers that all meet a certain criteria, for example all rational numbers that are less than 2. We call 2 an upper bound of that subset. Notice that 2 is a rational number, and that there are no rational numbers smaller than 2 that are also an upper bound of our subset - 2 is the least upper bound. Define a new subset, where we say a rational number x is in the subset if x * x < 2. We can easily see that 2 is an upper bound for this set, but so is the rational number 1.5, and 1.42, and 1.415. In fact, there is no least upper bound for this set that is a rational number. We extend the rational numbers to include a least upper bound for every subset of rationals, and we call this the real numbers. The real numbers have a lot of nice properties, most notably they are complete under the normal ordering, which essentially means that there are no gaps.
The reals don't have everything though! We notice that we can create polynomial equations, like x * x - 1 = 0 and that sometimes these can be solved (in this case x = 1 or x = -1 solves the equation) and in other cases they can't. For example, there are no real numbers that are the solution to the equation x * x + 1 = 0. We can extend the real numbers to the complex numbers by adding a new object called i, which has the property i * i = -1. A complex number has the form a + b * i, where a and b are real numbers. The complex numbers are called algebraically closed, and there is a really nice result that shows that all polynomials have solutions in the complex numbers.
The hierarchy actually keeps going, but hopefully you can see that numbers are just objects with properties that behave in useful and interesting ways under different operations. The formal definitions we have today have been refined over a long period of time to avoid contradictions and other issues, but there is nothing stopping you from making up your own numbers with their own properties. If they are useful or interesting other people will probably use them too!
> Maybe resort colonies are not fun to write about. Actually... Star Trek TNG has a bunch of episodes about Risa, which is a whole fricking fully climate-controlled resort planet.
I think one was more about the fact that entire planets are "just" colonies: farming, mining, or resort. It's far more likely that it's a planet with lots of different things going on.
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More generally, I think each item can be categorised by what type of shortcut is being taken by authors of huge universes.
- This physical problem will be easily solved by technology
- Yes this system is complex, let's not worry about the details
- It's easier to treat an entire planet like a single town, as our protaginist's journey becomes easily relatable to other story forms we are familiar with
I think audiences are ok with shortcuts a lot of the time, and often the really glaring holes in a world aren't even obvious unless pointed out (like his example where there is no law enforcement, but also no one underage in the bar).
Some things are just not believeable at all, and by reaching for a shortcut to make the story relatable introduces huge conceptual issues. So for example, it's fine to think that there may be some technological advancement that means spaceships don't have to worry about orbital mechanics, but if there is then that technology would be used everywhere as it's essentially vast amounts of energy or gravity generation.
Scifi in the near future gets to borrow the complexity of our world. So things like black mirror can ask "what would happen if we had a social credit score" and explore that in a very complex environment that it gets mostly for free.
The more alien your setting the less you can borrow from your audience's own experience. If you introduce some 'magic' (cryosleep, faster than light travel, fast travel between planets, etc) it is your responsibility to explain why it is only used for the one specific plot device you want it used for. This is one of the reasons why world building is hard, and even worse when you have hundreds of worlds to build. It's easier to just pretend the universe is made up of little towns that correspond directly to stereotypes from whatever culture you are from.
The consensus seems to be that it's legal in many places, however a dangerous lane change is always illegal and changing lanes in an intersection is almost always dangerous.
[0] https://www.reddit.com/r/NoStupidQuestions/comments/25kbg3/i...
The investigation you reference stems from previous versions of the softawre.
The broader context can't be ignored when discussing the new software, but it's reasonable to point to progress as demonstration that the chosen technology path is a viable one.
The cameras they have sent are quite good and can take 'true colour' images.
From the raw images they can be coloured as if a human was standing on Mars, but more often are coloured as if that part of Mars was on Earth. The reason for this is so that scientists can use their Earth-adjusted eyes to study the images - you want minerals in the photo to look familiar to the Earth scientist.
Perhaps the most effective thing a person can spend their time on is pointing people along paths likely to lead to success, and guiding them away from dead ends.
This work is slow, and a lot of the progress seems to be driven by the Google Summer of Code program (sort of like open source interns), so I suspect it will be a while before all the shell scripts are rewritten.
I think I agree with the rest of what you have said.
Can confirm it's been great so far - interesting content and the right length for a weekly newsletter.
This part might not be entirely accurate due to a lack of image data around takeoff and landing. I had to make my best guess from reference video taken by the Perseverance rover on a previous flight. That landing was a little rough and showed some bounce, so I recreated that.
Something similar is the Archibald Prize's 'Packing Room Prize'.
The award is chosen by the gallery staff who receive, unpack and hang the entries, with 52 per cent of the vote given to head packer Brett Cuthbertson. [0]
It's almost as prestigious as winning the main prize!
[0] https://www.broadsheet.com.au/national/art-and-design/articl...
The game could have multiple levels of 'border closure'; Australia has relaxed border restrictions over the course of the pandemic.
That statement, that the upper airstream flows faster because it has to meet up with the lower airstream, is wrong and easy to disprove experimentally.
So, putting aside that specific statement, re-read the post you're replying to.
The airstream above the aerofoil does travel faster, and there is a lower pressure region there (commensurate with the effect described by Bernoulli), and it turns out that this is a valid way to model the forces involved just as it is valid to model them as a redirection of the airstream.
Helicopters and planes are both pushing down on air to generate lift. The lift generated has to be equal or greater to the weight for the aircraft to fly.
Thrust can mean many things (at least colloquially). As discussed in the quora you linked, a helicopter will have a defined power to weight ratio that allows it to fly (maintain level flight) in its 'normal' flight envelope. There are a number of things the pilot can do that causes the aircraft to 'push down harder' on the air. One of these is flying close to the ground (the ground effect) which is sort of like pushing against the ground as well as the air, and another is by moving horizontally (usually forwards, like a plane, causing transational lift). Both of these allow the aircraft to maintain height while using less power than if it was hovering, but to do so it is still generating enough lift to counteract gravity.
Rocket engineering uses an immense amount of both modelling and physical testing. No-one says "Well I've got the Tsiolkovsky rocket equation, so let's go to the moon!"
I'm not even sure what the bar of 'understanding' is here - the fact that we have iterated and improved on powered flight as much as we have necessarily means that we understand it on a deep level, let alone the fact that we can create excellent models that predict what will happen to a wing in different situations.
At what point would you say we do understand flight?
If a plane isn't producing more lift than weight it will fall, just like a helicopter. Planes work by pushing a wing through the air, helicopters by spinning it. In both cases the wing has to push down enough air to keep the aircraft in flight.