What are some of the most anti-intuitive and interesting facts and theories in your specialty?

Hm. I used to work on prions. The sequence of the prion protein is highly conserved, that is, it didn't change much between species, evolutionary. That is usually a sign for a highly important functional protein. Yet, you can delete it with almost no ill effect in animal models. No idea why.
This is kind of similar to the number of toes in tetrapods. Tetrapods usually have five toes. Sometimes they have fewer, down to one. Aside from some of the very earliest tetrapods and aside from I think one or two exceptions involving flippers and some cases involving wrist bones instead of true increased digit number, they never have more than five digits. And yet polyploid mutations are very common, so it's not like mutations allowing six digits don't arise frequently. Why? Why is 5 always the max? Why does natural selection never favor 6 fingers or toes? There's no clearly obvious reason, it's very mysterious in my opinion.
What about prion diseases?
I didnt know prions were divide into species!!! I knew about different types. I guess I had them to closely associated with disease processes
I thought prions were a class of proteins
couldn't it be just a gene that was present very early and it just remained there, as part of that high percentage of functional as well as nonsense stuff that humans share with bananas?
When I was a kid reading about proteins (this was back in the early 2000s), it seemed to always be talked about as an almost-fringe hypothesis. Nowadays it seems to have found consensus.
Have prions been directly observed self-propogating yet?
Pretty much all rain that falls on earth, outside of the hottest tropical areas and some other unique circumstances, starts as snow high up in the clouds and melts on the way down. This is because A) even if the temperature is 100+°F (40+°C) the tops of most rain-producing clouds are well below freezing, and B) solid ice crystals grow much faster than liquid water droplets in the same humid environment. So a raindrop condensing from water vapor will take 10 to hundreds of times longer to form than a similar-sized snowflake, meaning that it outside of a few circumstances it takes far too long for rain to form just as pure water rather than a snowflake. This is known as the
This is also the method by which
Do snowflakes grow faster due to a higher ratio of surface area to volume?
When you get a warm rainshower in summer, how did the rain have enough time to warm up from below freezing?
I think I just saw this recently on one episode of QI (forgot which one), but I think they didn't mention the second point. Also, supercooled clouds are super cool.
Supercooled means at transition point between liquid and freezing?
Clouds never made sense to me. You say there is water droplets inside the cloud, but I don't see how they wouldn't just fall. I guess I need a physical chemistry class
In machine learning, I'd say that many people don't realize that neural networks can completely memorize a given dataset, fitting it with 100% accuracy even if that dataset is just absolute random noise. This came as a shock to many people in the field when Chiyuan Zhang published his famous [Understanding deep learning requires rethinking generalization] (
So NNs are fancy curve fitters?
Fascinating. Considering the weights of neural networks are often considered a "black box", how do we know how much an NN is memorizing and how much it is doing effective generalization?
This sounds like it could have applications in data compression, the sort where you compress once and either make lots of copies or store for a long time.
So they overfit the data so much that it has perfect interpolation but ahitty extrapolation?
Like it will always come up with a 100% accurate explanation, but that doesn't mean the explanation is good or is reasonable in general
I'd just like to address a lot of the misconceptions going around in this thread....
NNs are by nature not some magical tool that you can just wave over a problem and it's solved...
NNs get a lot of criticism because there are so many hyper parameters to optimize, and algorithms such as KNN do not have that problem (K Nearest Neighbours).
My supervisors have repeatedly stated that in a real world case, one must try and find the simplest solution, for example: If it is a linear problem apply linear regression, if it is a problem with more variables go for logistic regression. NNs are very much a black box and they are seen as a last resort.
NNs are amazing because they can take a massive amount of feature parameters and still find a solution (such as images) but they are not necessarily the best solution to a problem.
Are they learning new ways to learn?
Algae species could be more unrelated between them that humans and plants
There is a fight in the cancer field about whether non-inherited cancers (i.e. not cancers you get from genes/mutations you got from your parents) are caused by repeated mutations to a single cell, or dysregulation of the whole tissue environment.
This fight is between theories, the somatic mutation theory vs tissue organization field theory, has been bubbling for a few years. SMT is what I learned in college -- cancer comes from your cells getting mutated, usually several mutations are required, typically with mutations activating proto-oncogenes and deactivating tumor suppressor genes. TOFT says that cells want to proliferate and move around as their default, but don't because of 'tethers' or 'rules' that tissue/neighboring cells enforce -- telling cells not to proliferate and telling cells to say put -- and when those rules don't get enforced/obeyed for some reason a neoplasm forms.
Is there a reason that it wouldnt just be a mix of both?
Isn’t it known that cancer cells function very differently and show a couple of mutations at key points, or do I misremember that?
I work in the psychology of concepts, and outside of technical domains, virtually none of the concepts that we actually use (birds, tables, democracies...) have definitions that people use consistently.
To be more precise: outside of very specific circumstances, humans do not have a set of necessary and sufficient conditions that they check to determine if something falls under a particular concept. This is despite the urge to define all of our terms clearly at the beginning of a discussion.
Plato’s anything
I’m not sure I understand what you mean by this. Could you explain a bit more about what you mean?
"I may not be able to define it, but I know it when I see it" applies to more than just porn, then.
This is kind of why I always find the Chinese room argument ridiculous
I don't know if a lot of people know this, but if you take a beam of particles with spin aligned in the positive x-direction. Then you measure the spin in the z-axis and get half of the particles having spin in the positive z-direction and half in the negative. Then you measure the spin again in the x-axis and voila, you don't find that all of the particles have their spin aligned in the positive x-direction, but instead you find that half of the particles have spin in the positive x-direction and half in the negative x-direction.
et voila, I'll have to read more to understand this. thanks though
This is the principle behind quantum cryptography.
The Sun is the hardest place to send a spacecraft to in the whole solar system. Even though the Sun is at the bottom of a huge potential energy well, it is very tricky to lower a spacecraft's energy and angular momentum without the help of friction. This is one of the many reasons we won't ever use the Sun as a dumping ground for our trash. It would be easier to fling it out of the solar system.
If you aim the trash properly when you fling it out of the solar system, you can get its perihelion just so, and cause it to loop back around and dunk into the sun.
This is also easier than just shooting something right at the sun.
Is the logic behind not using the sun as a dumping ground that we might miss and catapult it back at ourselves or something else unintended? Because it doesn't seem reasonable to me that our hypothetical chip bag would gain enough momentum in its approach to the sun in order to punch through it and out the other side before it's vaporized and incorporated in the sun's normal plasma pools.
If you fired an object in the general vicinity of the sun, wouldn't the gravity capture it and spiral it into the sun after a couple revolutions?
Most things are never on fire, but fire can be on things lol. Down to a chemical level most objects have a temperature that it begins to release gases (smoke) and for all technical purposes it is the smoke that is on fire not the object itself. Mostly carbon based objects that is. There are some funky combustible liquids and solids that can light up them selves but that's another story
So what causes the smoke exactly
While software engineering knows how to make
What are some reasons it is done, despite being so expensive?
There's some hope that something like Idris will eventually be successful in industry.
Ah yes, seL4
Is it fair to say most software engineers wouldn't know how to make probably correct software? At best they could test every possible case, if all cases can be known.
One of my favorites from evolution: I believe that the Hippopotamus is more closely related to whales and dolphins, than to any living land animal!
And yet they can’t swim... how embarrassing for them at the family reunion
Computation is both incredible simple and incomprehensibly complex.
Computation can be made very simple. Lambda calculus is a syntax/formalism used widely for proving things about programs in computer science. The syntax is just 3 rules. Yet it's capable of describing every possible computation any other universal computer can do. In theory you could duplicate all of the internet by pen and paper using a syntax like lambda calc, it just would just take literal eons.
Computability is absolutely wild. The fact that just calculating the set of indices of Turing Machines for a given recursive function is an undecidable problem just sounds like complete nonsense at first. Then you have things like Kleene’s fixed-point theorems.
This also effects aircraft and balistics. A bullet will fly farther in humid air, and an aircraft will experience less lift
That really doesnt have anything to do with why clouds exist
Is that because warmer and therefore less dense air can take more humidity or does the humidity itself make the air lighter?
So why doesn’t fog just float up and away? Does it require a thin layer of cold air near the surface, with the cold increasing the density?
Not involved in the field any more, but did undergraduate real analysis.
There exist functions that are bounded, continuous everywhere, and differentiable nowhere.
One example (sorry for notation, the 'x' is a multiplication symbol not a variable, e is the constant from calculus although it can be replaced by other irrational numbers that aren't rational multiples of pi):
f(r) = sum from j = 0 to infinity of
0.5j x sin (r x ej )
So that is basically
f(r) = sin (r) + 1/2 sin (e r) + 1/4 sin (e2 r) + 1/8 sin (e3 r) + ......
Derivative is undefined everywhere, although this is continuous and is always strictly more than -2 and strictly less than +2.
It also takes every value in (-2,2) infinitely often.
I'm having trouble visualizing this. Is there a way to get wolfram alpha or something to graph that (or a related function)? Or a picture of any such function? Is it like a waveform with infinite frequency between (-2,2) and infinite amplitude?
The weierstrass function?
Write \* for multiplication. It will format itself to *
I have two since I have two areas of specialization, Urban Planning and GIS (geographic information science).
Widening roads, adding lanes, and other such attempts to alleviate traffic by increasing capacity actually has the opposite effect of encouraging additional use and exacerbating traffic problems. People who might otherwise find an alternate route around an area with existing traffic issues will instead end up using the newly "improved" road and eating up all that newly added capacity. Thus resulting in worsened traffic conditions as compared to before the "improvements" and significantly decreasing safety for both drivers and pedestrians alike.
Additionally, wider, straighter roads encourage drivers to speed because it affects the perception of speed. 35 mph on a narrower, windy-er road is perceived as much faster, and thus more dangerous than on a wide and straight road. And peoples' assessments of danger regarding how much they're "allowed" to speed is linked to their perception of speed.
Furthermore, straight and wide roads are perceived as safer in general and therefore lead to higher rates of distracted driving and people zoning out or falling asleep behind the wheel. Altogether, this makes wider, straighter roads less safe and more prone to traffic issues. The more "unsafe" a driver feels on a road, in regard to how much attention they feel that they need to pay to their speed and control of the vehicle, the safer it is for everyone.
In city/transportation planning, we have approaches to dealing with congestion and safety known as traffic-calming techniques. Things like narrowing lanes, reducing the number of lanes, making roads curvier or adding features to the road like medians, roundabouts, unusual lane changes, and so forth that force drivers to slow down and pay more attention.
2. TL:DR - The Earth is not a sphere, it actually more closely resembles a, "fucked up ball of Play-Doh." We only view it as spherical out of necessity for mapping.
So, the Earth is a sphere, right? An oblate spheroid if you want to get technical. We've all seen pictures from space of our beautiful blue marble. We've all been told as much in school. Well, what if I told you that everything you thought you knew about the shape of the Earth is wrong? Because it is! The Earth isn't really spherical at all. It only looks that way from space because of the shape of the magnetic field that surrounds our planet and holds its atmosphere in place.
I'm actuality, if you remove that field and the atmosphere and look only at the Earth's surface, it resembles what I like to call a, "fucked up ball of Play-Doh." Imagine forming the smoothest, most beautifully round ball of Play-Doh that you could possibly make. A model of the Earth that would make even Copernicus jealous. Now, take that perfectly round model of the Earth, hold it in your hands, wrap your grubby fingers around it, and squish it. Not too much to make it no longer approximately round but enough to ruin your beautifully, perfectly round ball of Play-Doh and leave it disfigured. Covered in peaks and valleys and no longer something that you could expect would roll well on the ground, or roll much at all. That's the true shape of the Earth. A fucked up, partially squished ball of Play-Doh.
This is because of the natural variability of the Earth's surface; its topography. From the highest mountain peaks to the deepest ocean trenches, and everything in between. The Earth is extremely non-uniform in its actual shape. Because of this, in order to map the world we have to create mathematical models, called geoids and ellipsoids, that approximate a "round" Earth. Without those models, it would be impossible to use coordinate systems and make maps. GPS as we know it would not function.
Also, without these models, we wouldn't be able to determine sea level because sea level is highly variable. Sea level in one place is not the same as in another. This is largely due to natural variability in gravity; the pull of gravity is not uniform all around the Earth. The reason that gravity on Earth lacks uniformity is due to the wide variability in mass and density around the Earth caused by the variability in topography. Areas with more mass, and thus higher density, will have higher gravity, and vice versa. In turn, this affects sea level across geography. Higher gravity results in lower sea level and vice versa. And this isn't even taking into account things like tidal forces and climate change.
The geoid model that I previously mentioned is the model that gives us Mean Sea Level (MSL). An approximation of an average sea level for the whole of the Earth. From the geoid, of which there is only ever one model in use at any point in time, although the model is updated every so often as geologic and geographic conditions change, we create ellipsoid models. There are many ellipsoid models in use at any point in time. They are more perfectly "round" than the geoid model and form the basis for all the various coordinate systems in existence.
Going even further, we have many variations of ellipsoids called datums which are localized to certain areas, North America for example, and which adjust the origin point, (0,0) in (X,Y) coordinate system speak, so that the model used for a coordinate system is as accurate as possible for a certain region. This is because as scale changes, as you look at and map larger or smaller areas of the Earth (i.e. as you zoom in and zoom out), the location of coordinates themselves change even though the location of the Earth's physical features at any given coordinate don't.
If your brain is hurting that's okay. I have a university education in this stuff, and I teach GIS as an adjunct professor, and this stuff always still blows even my own mind. But I never stop geeking out on it either!
Pictures to help visualize
*Edited for formatting, spelling, and grammar
*Edited to add image link
How is the earth not still approximately a sphere? The radius is about 8000 miles, the highest mountain only about 5, so everything should look close to flat I thought. I know it's also wider at the equator then through the prime meridian because of centripetal force, but the doesnt stretch enough to make much of a difference compared to 8000 miles
Does this mean that increasing capacity on a given road reduces traffic and accidents on surrounding roads? For example, if you want to make a neighborhood quieter and more pedestrian/child-friendly, should you increase the capacity of a nearby road?
Likewise, if you employ traffic-calming techniques on a congested road, does this mean nearby smaller roads become more congested?
If you could redesign a major city from the ground up today, how would modern urban planners prefer to lay out the roads and zoning (if the goal was to, say, maximize both safety and travel efficiency for a large and growing population)?
Living in a busy city, I’ve always thought of traffic as an economics equilibrium problem. Motor traffic is a function of the time taken to get your destination vs the utility of being in your own car (control/comfort/convenience) - removing a bottleneck reduces journey time therefore more people will drive until it reaches an equilibrium with the time/hassle of using public transport.
Those images do not show the shape of Earth at all.
Lighting everything on fire is good for the plants.
well for the future plants. but they'll need a while and some more help to regrow.
EDIT: I'm thinking about trees, forests with fauna living in them. if those burn, it's a big damage. I understand that fire can be functional in case of GRASS fields, but the comment above mine did not specify.
So invest in Australian agriculture now?
I am not a human evolution expert, but definitely an enthusiast, so this is kinda ELI5. I could talk about the myth of the caveman all day long, but here's a weird example. When we think of Neanderthals, we think big, brutish, grunting, hairy, gross cave people. This is partly because one of the first (poorly done) reconstructions used a bunch of old, broken bones with missing teeth. But the fact that there was an OLD, BROKEN Neanderthal meant the opposite of our caveman stereotype -- it suggests that they cared for their injured and elderly, not that they grunted and fought all day. Kind of counter-intuitive like the WWII airplane damage story. There's even evidence that Neanderthals used art, had religion, buried their dead, understood symbolism. #HomininsArePeopleToo
What is the Word War II airplane story?
This isn’t my specialty per se, but it’s related. Professional money managers as a group, on average, have worse performance than the market as a whole does on average.
Gasoline and any other flammable liquid don't actually catch on fire when in liquid form. It is the vapors from said liquid that inflame. The flamed vapor makes the liquid below heat up quickly and turn into vapor so fast that this process is almost instantaneous. That's why some flammable liquids don't "work" under certain temperatures. It is just not hot enough for the vapors to form and the process begin.
Quick experiment: fill a shot glass with some hard liquor and throw a match inside of it and the wet vodka will put the fire out. Now hold a lit match near the surface of the vodka and watch it burn your fingers off while you yell "Yeah! Science!"
I am in cognitive neuroscience:
The majority of perception is based on prediction, meaning your perception is formed before you process incoming sensory information, and that sensory information only serves to fine-tune the predicted percept. The axiom for catchphrase for this theory is "Perception is a controlled hallucination."
It's standard in automotive b2b edi to have “standards“ that are customized so much per customer that you can never use anything twice.
what is b2b edi?
Software development - adding more programmers to a project will often make they project take longer.
Hardly specific to software, is it?
Adding safety equipment to an airplane does not necessarily make it safer.
Adding safety features does not necessarily make things safer in general...in fact, sometimes it just adds more points of failure. There's a great podcast episode about this
For plasma/ion thrusters and rockets in general having a more fuel efficient engine (higher Isp) doesn't always mean that your spacecraft will be lighter.
In much of the world, your electric company doesn't own any power plants.
Also, preparation for solar flares and EMD pulses is a routine part of planning the power grid.
In patients without ADHD, Ritalin (an amphetamine derivative) acts as you would expect, being a powerful stimulant, producing a hyperactive and euphoric state.
In patients with ADHD, Ritalin has a
Higher color temperatures feel cooler and lower color temperatures feel warmer, visually.
Color temperature of a light is the temperature of a black body (sun) that has the most similar color.
Sadly, blue white lights are said to feel "cold" while red white lights are said to feel "warm".
The black body temperature of a blue white light is much higher (physically hotter) than a red white light.
That hot water freezes faster than cold water.
I'm an IT professional and have done most types of support and repair. An absolutely phenomenal amount of problems, ranging from physically damaged hardware to missing files to malware infestations to unwanted programs and more, are never the fault of the owner/operator. The theory is this: If a person doesn't know how to use a computer, how could they have done such things?
Im not specialised in space but
Getting into earth's orbit is more about moving fast horizontally than vertically (xkcd)
When water freezes it releases heat. Orange growers will spray their trees with water as a last ditch effort in freezing temperatures because the small amount of heat given off by the freezing water is better than nothing.
Worked in an industry where people spent a great deal of money hoping never to use the product.