How long does it take for a subverting tectonic plate to be totally recycled? | AskScience Blog

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Thursday, December 12, 2019

How long does it take for a subverting tectonic plate to be totally recycled?

How long does it take for a subverting tectonic plate to be totally recycled?


How long does it take for a subverting tectonic plate to be totally recycled?

Posted: 12 Dec 2019 02:39 AM PST

How long until a tectonic plate completes a full cycle? From when the newest crust emerges on one end all the way to being subverted on the other. It would obviously be different for each plate, so feel free to give specific example(s).

submitted by /u/Brandwins
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Is the International Space Station's orbit altered by the weight of new supply deliveries?

Posted: 11 Dec 2019 10:55 PM PST

I read that the ISS receives several tons of supplies at each delivery. Does this change the momentum or overall energy, or otherwise do anything to the object's orbit, and does its path need to be adjusted or boosted somehow to compensate for the additional mass?

submitted by /u/OnCommence17
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What exactly makes something feel itchy?

Posted: 11 Dec 2019 04:19 PM PST

What causes something to feel itchy and what does an itch mean?

submitted by /u/joshuapjacob
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Are Blue Whales actually the biggest ever?

Posted: 11 Dec 2019 08:38 PM PST

We are taught that blue whales are the largest mammals/vertebrates to ever exist. Isn't this unlikely considering our lack of seabed fossil evidence?

submitted by /u/conanmagnuson
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Does candle wax have a "wax memory" (noticeable viseoelastic creep)?

Posted: 11 Dec 2019 05:53 PM PST

Today I was asked if I was aware that I should let a candle completely burn to the edge of the glass jar the first time to maintain an even burn throughout the remainder of the candles. Up until then I hardly noticed my habit of burning a candle with adequate time to melt the full width of the wax. Basically, I liked the candle more visually with minimal wasted wax clinging to the sides of a container so whenever I'd burn a candle I would attempt to burn the candle to the edge of the glass. I had never really thought of it any further that that.

They explained to me that he was always told it was due to the wax being easier to melt after it had already been melted once. I accepted this and asked if we could find out the name of types of matter with this property, after all this must have been an observed phenomena before and would likely share this trait with other forms of matter. We begun some routine searches of differing combinations of words like; wax, candle, melt, remelt. They were a bit strange at first, mostly directing us to candle sellers and DIY candle instructions detailing the importance of the first burn and the original pouring temperature and leading us to ideas like wax memory.

After further refinements to our searches we began ask more questions than we would find answers. With most of our searches turning up less than scientific sources (though not necessarily incorrect or science-skeptic) I started to get really curious about the physics behind some of these clearly well known patterns in candle burning. It was clear that correctly burning a candle could prevent excessive edge wax or create a desired tunnel in a candle without a jar. It also became resoundingly clear that environment, wax material, wick size, and quite a few other elements were at play and were almost as important as length of burn time and the first few burns.

It seems to me that after the candle was burned the first time, if it was inadequate to complete the burn, a "tunnel" could be formed creating a buffer then preventing radiant heat from reaching the edges of the wax. This would obviously reduce heat on the glass which could then radiate the lower heat to the cool air around it further reducing the potential heating of the dreaded edge wax. The creation of a tunnel deep enough to block radiant heat would naturally dig itself deeper as it's own walls prevented heat from escaping and allowing newly melted wax to fall below instead of heating outwardly. This might be desired in candles without containers, but a smaller wick could achieve that as well.

This might stand in contrast to there being a true "memory" present in the matter comprising many candle waxes. The memory idea seems more likely to be observational bias on the parts of people who have are burning candles in consistent ways leading to certain patterns in the wax shape. Those patterns are often self encouraging which explains why it's easy to intentionally mold a new candle into a desired state, so easy to accidentally misshape a candle early on, and so tough to reverse the trend once begun.

After a few hours of diving down this rabbit hole for no other reason than candles are neat, I am honestly left with a few questions. Is there actually any truth to the first burn is the most important line of reasoning? Or is it just a result of successive similar inefficient or efficient burns that creates tunnels and edge wax, leading to a nearly irreversible state after a few repeated similar burns? Something about non-viseoelastic creep I can almost understand, and why am I not studying for my final next week instead?

submitted by /u/Wtantis
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What exactly is momentum and how does it differ from kinetic energy?

Posted: 11 Dec 2019 11:35 PM PST

I've always been confused as to why Momentum = mass x velocity, but KE= 1/2 x mv2 because to me they seem to describe pretty much the same thing. What's the reason for this and what exactly is momentum and KE?

submitted by /u/EtecaEteca
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Is there a good way to quantify how "random" a given method of shuffling cards is?

Posted: 11 Dec 2019 12:45 PM PST

I used to shuffle cards the normal way, split it in half and then recombine, but then I realized: the topmost cards in the deck still stay mostly on top, and the bottommost cards still stay mostly on the bottom, so you're not really getting a completely random distribution, no matter how many times you shuffle the deck.

What I do now is split the deck IN THREE, like, say, A, B, and C, with B (the middle portion) being about as big as A and C combined... and then I take portions A and C and stick them together BACKWARDS, so now we have a deck portion CA and a deck portion B, and then I shuffle CA and B together like you would any two halves of a deck.

Is there any even better simple way to REALLY randomize the order of cards in my deck? Is there any way to quantify how random a shuffling method is?

Like, I was thinking, how accurately could you guess the position of any card in a deck, say, three shuffles down? With the traditional cut-in-half-and-interpolate method, you don't really have a good chance at guessing any of the middle cards' future positions, but with the top and bottom few cards you can basically predict they'll stay approximately where they are, moving a bit deeper into the deck as you go along. With MY method, you'd have much more trouble guessing even the outliers!

could anybody point me in the right direction to learn any more about this topic or anything? I know a few mathematicians but none of us are on speaking terms rn so I'd love some help from you sweet people

submitted by /u/biggerbluejay
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At this point in time, are we able to simulate nuclear bomb tests by a computer with similar accuracy to a real life test? If so, are these test done as frequently as in the Cold War?

Posted: 11 Dec 2019 11:09 PM PST

Why do liver cells have varied cell cycles and is this why you can do a partial liver transplant?

Posted: 11 Dec 2019 07:30 PM PST

I was doing some research for an intro cell bio class and was looking into the cell cycle of a hepatocyte and while researching I found that the cell cycle usually takes roughly a year to go through it's cycle but could take up to 22 hours if need be. Why does this particular type of cell do this, do other cells in the body have this same variability in reproduction of the cell (without being cancer) and is this why you can do a partial liver transplant and it will grow into a full liver?

submitted by /u/jacknolan329
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What is the difference between a 'perforating' gunshot wound and a 'penetrating' gunshot wound?

Posted: 11 Dec 2019 06:24 PM PST

Forensic pathology is an interest of mine, and I've seen dozens of autopsy reports and death certificates, but one thing I never got a clear answer on was the title question.

An example is Kurt Cobain. Washington State autopsy reports are not public record, but I've seen the death certificate. "Cause of death: contact perforating shotgun wound to head (mouth)"

By all indications, the man who discovered his body thought it was a mannequin until he saw blood leading from the ear into a pool under the upper body. Kurt used light gauge ammunition. "Birdshot", as they call it. Generally not enough to blow the top of someone's head off, like 12 gauge buckshot probably would.

Does that mean a 'perforating' wound is one that doesn't exit the body, and a 'penetrating' wound is one that goes through and through, leaving an exit wound?

I apologise for the ranting post, but for close to 20 years now, Kurt Cobain's autopsy report has been my "white whale", and it's personal to me. I thought I'd ask people more knowledgeable than myself to fill in some blanks I'll probably never get the chance to know directly.

Thanks.

submitted by /u/chaosperfect
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In fluorescence the emission wavelength is lower energy than the excitation wavelength. Where does the extra energy go?

Posted: 11 Dec 2019 01:15 PM PST

Does it just turn into kinetic energy?

submitted by /u/fleemfleemfleemfleem
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Do scientists compensate for the movement of Earth and the Milky Way when they measure the red and blue shift of other objects in the universe? How can they know that the measurements are correct, if the reference point is also moving?

Posted: 11 Dec 2019 07:11 AM PST

How did early chemists determine that chemical elements were chemically indivisible, and their respective atomic weights? How did they determine that common stable substances were not elements?

Posted: 11 Dec 2019 04:50 AM PST

What prevents full on recovery of limb function?

Posted: 11 Dec 2019 05:34 AM PST

Let's say a soldier is hit by shrapnel. A dozen pieces cut through his arm, cutting tendons, blood vessels, and fracturing bones. He is airlifted back and the arm is saved. Yet, his arm is slower, weaker, and sometimes throbs painfully. Why?

submitted by /u/Accelerator231
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Are there any atoms that can form either cations or anions depending on the molecule?

Posted: 11 Dec 2019 06:38 AM PST

Like for example can O be either O2- or O2+? Or can all atoms form either only cations or anions?

submitted by /u/submarinekid
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