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Comment by OnleMeMeMe | Hacker News Reader

Always love

https://en.wikipedia.org/wiki/List_of_common_misconceptions

Beside chastity belts my favorite is the myth of the flat earth.

Learning the truth about many of those misconceptions even before discovering the whole list is what ultimately broke my trust in mainstream opinion. The whole time since I left high school has been a period of systematic unlearning of all the bullshit I've been taught - by teachers, friends, families and talking heads. Just how the hell is an adult supposed to live if every other day they discover another thing they thought is obvious is actually wrong? This is one of those things that really pisses me off about reality.

Buck up! I think of it as, zeroing in on truth. Historically we had approximations and good guesses. Now we're in an unprecedented period of discovery and science. Of course we have a lot to unlearn!

That's definitely a good way of looking at it, but still, most of those misconceptions aren't lack of knowledge; it's people presenting bullshit to other people as facts of nature. It's not that we had to discover how, say, microwave oven works - we obviously knew that before the first one ever hit the market! Someone somewhere just invented an explanation and it spread, and most people don't bother to even think twice if it makes sense.

My favorite wrong fact was the simple model of friction we were taught - that force was proportional to surface area and weight. In middle school we were given force gauges and wood blocks. Pull them stacked or linked and graph the force vs weight X area. I got a weird curve. Looking around, I saw everybody else fudging their data to make a straight line. Confusing.

Decades later I heard on the radio "The traditional model of friction has been proven incorrect for many materials" and I thought, I knew that in middle school.

I think you may have misunderstood something here. The high school static fiction model is:

  frictional force = normal force X coefficient of friction

i.e. frictional force is independent of surface area according to this model.

What are the units of that coefficient? Per square? And are we talking force or pressure. Hm.

The experiment used blocks with hook-and-eye screws. You dragged them across the surface linked in a chain, then again stacked, in twos and threes. The result came out nothing like a linear relationship.

The coefficient has no unity. It's N/N. And we are talking about force, not pressure.

By an ideal linear friction, you should have measured the same force on all experiments. But reality is way more complex, and sometimes the ideal model won't give you even a first order approximation.

Your teacher shouldn't have used wood blocks (unless he wanted to make a point), metal ones would give better results.

I'm sorry you've got totally the wrong end of the concept here.

Check out https://en.wikipedia.org/wiki/Friction#Dry_friction

You might enjoy "The Structure of Scientific Revolutions". It argues convincing against the idea that we have not been zeroing in on truth. Our understanding is better then it used to be, but it's not because we're been steadily progressing. It's because we occasionally throw everything out and start over through a "paradigm shift". This book coined that phrase.

I've had to unlearn and relearn chemistry like 7 times now (since quantum chemistry finally makes accurate quantitative predictions, I'll trust it for now...)

I know you can't teach third graders quantum mechanics, but I wish they at least wouldn't have taught me wrong stuff that became ingrained into my mind at an early age.

Almost 20 years later, I distinctly remember my high school physics teacher standing at the front of the class on the first day and saying "Remember this: everything you will learn from me this year is wrong."

> It is rarely necessary to wait 24 hours before filing a missing person report; in instances where there is evidence of violence or of an unusual absence, law enforcement agencies in the United States often stress the importance of beginning an investigation promptly. The UK government website says explicitly in large type "You don't have to wait 24 hours before contacting the police".

Saw this myth repeated on one of those John Walsh type cop shows the other day.

Anyone who believes microwaves cook things from the inside out has never tried to microwave a frozen burrito / pizza pop.

? Cut a thick piece of meat that's been microwaved. You see complex red/brown variation, because microwaves penetrate. Its not all cooked from the inside, but its different from a conventional heat oven in that there's some cooking from the inside.

Its easy to write sophomoric puff pieces about how we had it all wrong. Just assume an Aristotelian posture of black/white 'facts' and show its actually grey. Voila!

As stated in the wikipedia article, the microwaves penetrate to a depth of about 1cm (give or take, depending on the food). So, in a sense, it can be argued that the microwaves heat from inside, though in reality, not very far inside.

The trouble is that microwaves work mostly by heating liquid water. Ice is not liquid water and absorbs microwaves relatively poorly. The already melted parts tend to heat up faster while the still frozen parts heat up very little. This, in addition to the limited penetration, is how you wind up with food that is napalm hot on the outside and still frozen in the middle. If you are trying to defrost something or cook it from frozen, you are much better off using a lower power setting. The peak power output is actually the same, but it gets turned on and off (you can hear it cycling) so that the warm areas of the food have more time to transfer some of that heat to the still cold areas through good old fashioned conduction. Incidentally, this is the same reason that the instructions for many pre-made items tell you to let them sit for 1 or 2 minutes before taking it out of the microwave.

(Some?) Panasonic microwaves claim to be able to lower microwave power linearly without the on/off power cycling. I'm mildly curious if their marketing claims of superior cooking hold up.

http://www.panasonic.com/in/consumer/home-appliances-learn/t...

Indeed, and they seem to make a difference: http://thesweethome.com/reviews/best-microwave/

Wait a second. The Wikipedia page first says that microwave do not cook from the inside out because the microwaves do not penetrate beyond 1 cm. but then it says that microwaves really cook by oscillating the magnetic field which jostles around dipoles like the water in food.

So does the magnetic field only penetrate very close to the skin, or are all the water molecules inside the food being excited, resulting in the food being cooked indeed from the inside?

On the other hand you really can get severe burns from the filling of a microwaved jelly donut even if the dough part is cool enough to hold. It's true the microwaves don't heat "from the inside out", but it's also true microwaves heat some materials dramatically better than others.

This was interesting read, thanks!

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