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Wednesday, September 19, 2018

Why is it that even when the wind blows warm, we feel cooler?

Why is it that even when the wind blows warm, we feel cooler?


Why is it that even when the wind blows warm, we feel cooler?

Posted: 18 Sep 2018 12:58 PM PDT

Another example: On a warm day, if somebody blows on your face your face gets cold/chill.

submitted by /u/fisnikhaj
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What is it about a curing process of meat, drying of fruit etc. that makes the food last longer and allow you to store it unrefrigerated?

Posted: 18 Sep 2018 09:41 PM PDT

Is there a minimal size a star can be?

Posted: 18 Sep 2018 05:18 PM PDT

I understand that stars can be massive. For example, VY Canis Majoris would fit inside Jupiter's orbit around our sun. But, what about small stars? Is there a minimal size they can be and still begin nuclear fusion?

(I hope I'm asking this clearly!)

Thanks, science!

submitted by /u/filthyheathenmonkey
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Where do all of the skeletons of marine life go?

Posted: 18 Sep 2018 06:47 PM PDT

You don't find too many skeletons of marine life on shore

submitted by /u/TyHag
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Are haplotype blocks never broken by recombination?

Posted: 19 Sep 2018 06:42 AM PDT

Even though there are recombination hotspots, I thought recombination is in general a random event.

​So what enables a haplotype block to survive recombination for generations? For example the average length of a haplotype is several kilobases long. That seems a bit long to survive random recombination.

​Or, if a haplotype block exists today, for how many generations can you trace it back before it is broken by recombination?

submitted by /u/lxl
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When archeologists are looking for Paleolithic/ Neolithic artifacts how can they be sure what they’ve found is an ace head for example, rather than a triangular rock?

Posted: 18 Sep 2018 07:04 PM PDT

I see examples of Stone Age artifacts like axe blades, arrowheads, etc but they just look like triangular rocks. How can an archeologist tell what is a Stone Age flint tool and what is a naturally occurring object?

submitted by /u/RSTLNE3MCAAV
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How did HIV/AIDS virus originate? Was there someone like patient zero?

Posted: 19 Sep 2018 04:32 AM PDT

HIV is transmitted sexually or blood transfusion or sharing needles so who was the first person carrying the HIV?Did the virus mutate from something else? If it did so, then will it mutate again and take an even more dangerous form like transmission via air?

submitted by /u/ChatsALot99
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How do laser thermometers detect temperatures of the surface they are pointed at?

Posted: 18 Sep 2018 03:20 PM PDT

Why do we get hiccups?

Posted: 18 Sep 2018 07:00 PM PDT

Do other stars have a 11 year sunspot cycle like our sun?

Posted: 18 Sep 2018 02:22 PM PDT

I was thinking about the Kepler and TESS astronomy missions; specifically, that they would have to differentiate between sun spots and transiting exoplanets. This made me wonder if enough data has been collected to research the sunspot cycle in other stars.

submitted by /u/zzzyx
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Why is it the instinct for young animals to play?

Posted: 18 Sep 2018 02:57 PM PDT

Why/How is this learned and why does it seemingly fade in all animals, humans included?

submitted by /u/GP_3
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Celestial bodies are constantly in motion, but named constellations have been around at least two millennia. What is the rate of change in position for these constellations to an observer on earth?

Posted: 18 Sep 2018 01:27 PM PDT

Also - how might they have looked different (if at all) 200 years ago? Is there any history of astronomers noticing this and drawing conclusions before the current model was popularized?

submitted by /u/cartoptauntaun
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Can Plasma be used as a lens to focus EM radiation?

Posted: 18 Sep 2018 01:40 PM PDT

Hey Everyone,

I was just watching a video on Star Wars hyper drive lore and it talks about a gamma ray source emitting though a wave guide into a fusion reactor. Obviously this is high concept Scifi, but it got me thinking...

If you were to take EM radiation and fire it through a spherical or lens shaped confined plasma, could it be used to focus or disperse the radiation and what would any fringe effects of some setup like this possibly be?

Love you all!

Edit: been thinking about it a little more and if the gamma ray waveguide acted almost like a projector through some hyperdimensional structure in the fusion reactor, could it maybe ripple spacetime?

submitted by /u/_paiggey
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How do iPad chargers allow more current than iPhone chargers?

Posted: 18 Sep 2018 05:50 PM PDT

The charger for an iPad allows 2100 mA (milliamps) of current. The charger for an iPhone only allows 1000 mA. This means if you plug your iPad into the charger for an iPhone it will charge much more slowly. My question is this: How are the chargers different?

I already understand part of this so I'll include that part in the question. The electricity from a wall outlet is about 110 volts of alternating current (at least in the U.S.). The charger converts that to 5 volts of direct current. (Anything powered by a USB port is 5 volts.) The device has electrical resistance which determines the current. For example, if the iPad's resistance is about 2.38 ohms then it would "draw" 2100 mA of power. When we say "draw" we really mean the device would allow that much current to pass through. If the iPhone charger is also pushing 5 volts and the resistance for the iPad doesn't change then the iPhone charger must be throttled in some way. I'm sure it's a safety measure to keep the charger from getting too hot, but how does that throttling work?

submitted by /u/Robots_with_Lasers
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How is yaw controlled in different types of helicopters?

Posted: 18 Sep 2018 01:26 PM PDT

So I think I understand how yaw is controlled in standard tail rotor helicopters and in coaxial rotor copters like the KA-50. Yaw is controlled by balancing torque with counter torque, or changing the balance of torque between two coaxial rotors.

What I'm having trouble understanding is yaw control in tandem rotors like the Chinook and in synchropters like the K-MAX.

According to Wikipedia tandem rotors control yaw by changing rotor pitch with each rotor on opposite sides, which creates opposite lateral motion at the front and back. In single rotor helicopters changing pitch on the left or right side creates lateral motion by causing the vehicle to roll, but since the Chinook can't roll in both directions at once, what force is causing the lateral motion that creates yaw?

Also according to Wikipedia, synchropters control yaw by raising the collective on a single rotor. I'm guessing this changes the balance of torque by making one set of rotors less aerodynamic, but wouldn't this also cause the whole vehicle to fly upwards, roll in one direction, or both?

Typed this on my phone during break at work so I apologise for typos/formatting.

submitted by /u/Slithtoves
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How do birds whistle and make discernable notes without lips or some other way of controlling pitch, like humans?

Posted: 18 Sep 2018 08:59 AM PDT

Are speedreading school legit or a hoax, howmany words per second can the brain actually read retaining all the information?

Posted: 18 Sep 2018 11:40 AM PDT

How will climate change affect the Pacific Northwest (US)?

Posted: 18 Sep 2018 04:13 PM PDT

It's always been a dream of mine to live in southern British Colombia CA or Northern Washington US, and I would like to know if there are any predictions for significant climate change regarding this region. Particularly; will the temperatures change? Will be there be less/more rainfall? Anything else? Thanks in advance!

submitted by /u/acaballeromusic
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Does having exercised in early life have an effect on losing weight later on?

Posted: 18 Sep 2018 10:04 AM PDT

Suppose there are two people at an equal level of fitness, but one has never done sports and the other has had lots of exercise in his youth. Does the person with experience in sports get fit faster?

submitted by /u/janneman66
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Tuesday, September 18, 2018

When staring into complete darkness do your eyes focus on infinity or are they unfocused?

When staring into complete darkness do your eyes focus on infinity or are they unfocused?


When staring into complete darkness do your eyes focus on infinity or are they unfocused?

Posted: 17 Sep 2018 07:54 AM PDT

Do Insects have a sleep schedule?

Posted: 17 Sep 2018 06:16 PM PDT

Is there a limit on how many stars could be in one solar system? Currently world building for a story, and wondering if a planet could realistically exist in a system more 3+ stars, and if so, what effects could that have on its climate and seasons.

Posted: 17 Sep 2018 08:01 PM PDT

What are objects with the ultra shiny centers and 4 cross like points I see in so many galaxy cluster photos? (See link)

Posted: 18 Sep 2018 01:42 AM PDT

What can we use bronze for today and why?

Posted: 17 Sep 2018 11:59 PM PDT

I was wondering what we use bronze for today and the reason for it. I cant seem to find a reason for using bronze in industrial and non-industrial purposes.

submitted by /u/Gronnsakspai
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To what extent does the pre-frontal cortex continue its development between the ages of 18-25?

Posted: 17 Sep 2018 09:42 PM PDT

If the PFC is not fully mature until a person's mid 20's, how much change is actually occurring from post-puberty to then?

I understand that further myelination or synaptic pruning in this region would alter it. However, is the overall development slowly coming to an end as a person ages? Or, is significant change still happening during those 7 years that can be observed?

submitted by /u/darkostwin
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How does the voltage of an output on an electronic device (such as an amplifier) not match the input voltage?

Posted: 17 Sep 2018 05:22 PM PDT

Does there have to be some trade-off between voltage (increase) and amperage (decrease) to maintain the same power? Is this possible? What characteristic determines how the electricity is manipulated to have different properties coming out than it did coming in?

submitted by /u/Raiderboy105
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1 Why do pressed/dried leaves retain most of their bright colors instead of turning brown?

Posted: 17 Sep 2018 11:05 PM PDT

I pick an especially colorful leaf each year to save from Autumn/Fall and they've always stayed the same color once dry.

Why do leaves keep their "autumn" patterns and colors if you put them between book pages or dry them upside-down, and not just die and turn brown? Why do all the leaves on the ground die and turn grey/brown before winter? Bacteria?

submitted by /u/kaanimas
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What physically happens to the body in a morphine overdose?

Posted: 17 Sep 2018 07:07 PM PDT

I know that its used in regulation to negate pain but what physically happens to a body when a large amount of morphine is given to kill someone.

submitted by /u/IneedathrowawayatJOB
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Is Dwarfism immediately recognizable at birth?

Posted: 17 Sep 2018 06:57 PM PDT

Can doctors immediately recognize an infant has dwarfism when it's born or does it take a while to begin to see the signs?

submitted by /u/ithappenedaweekago
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How do stars create extremely heavy elements after uranium?

Posted: 17 Sep 2018 04:16 PM PDT

I know that supernovas can create extremely heavy elements (up to uranium as far as I know), but how are the elements after that formed?

submitted by /u/Syndr1l
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How did scientists recreate the 1918 Influenza Virus?

Posted: 17 Sep 2018 01:50 PM PDT

I do not know if I've used the right flair, but the articles have put heavy emphasis on evolutionary biologists, so I figured this was a biology question.

I've been doing some research into the 1918 Influenza, and I've seen all sorts of stuff about the historical impact of the virus, but not a lot about the biological properties of the virus itself.

Some articles seem to suggest it was the H1N1 virus, while others say the H1N1 virus is a "distant relative" of the Spanish Influenza.

I have also read comparisons to the H1N1 and H5N1 viruses made by recreating the Spanish Influenza virus.

Which leads me to my question - how did scientists recreate the Spanish Influenza virus?

And is it the H1N1 virus? Or just a similar virus?

Thanks!

submitted by /u/Sparky_Shoes94
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Is the ground above mass graves such as the ones used during the holocaust more fertile?

Posted: 17 Sep 2018 09:54 AM PDT

What's the reason behind countries choosing different voltage standards?

Posted: 17 Sep 2018 10:35 AM PDT

For example, USA has 110/120 V while UK/India has 220/240 V. Is it a deliberate choice? or an after-effect of something else? Just realised that it is quite stark and was curious to know the reason.

Let me know if this is not a good enough question

submitted by /u/mag_ops
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Does eating lactose while lactose intolerant have cumulative negative effects?

Posted: 17 Sep 2018 07:32 AM PDT

Does the intolerance have long term effects, if the immediate symptoms are ignored?

submitted by /u/misscourtney
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After a while wearing glasses that invert things vertically vision your brain adjusts to compensate, would the same happen with hearing? Would it even be possible to test?

Posted: 17 Sep 2018 07:41 PM PDT

I remember watching a reading rainbow where Levar Burton wore special glasses and talked about how your brain switched things around. I think it was reading rainbow. The audio channels were switched on a game I was playing and I wondered if the same would happen eventually. I assume it would require more controlled conditions if it was even possible.

Edit: Ugh I messed up the title but I think you know what I mean.

submitted by /u/FindMeOnTheWall
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What would be the effect on a human body of the impact of an extremely energetic nucleus (100 EeV) from cosmic rays?

Posted: 17 Sep 2018 03:34 PM PDT

Reading on Wikipedia, I see there are particles arriving Earth with an energy of 100 EeV (about 16J, about the same energy as a mid powered air rifle) with a frequency of 1 event per square meter per century. Apparently, there are recorded events that reach 50J, equivalent of a baseball at 90 km/h (56 mph).

I understand that on the surface it arrives scattered as secondary radiation after hitting the atmospheric gasses, so there wouldn't much to notice, except for equipment to measure this sort of events.

But what would happen when an astronaut during an EVA (extra vehicular activity) happened to be hit by one of such particles? Would it be closer to radiation poisoning or to actually being hit by an object?

submitted by /u/Slackbeing
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How exactly does a smart meter know the difference between TV usage, AC usage and other?

Posted: 17 Sep 2018 11:09 AM PDT

My utility bill shows me a chart of energy usage based on device (AC, refrigerator, Always on and other). I'm curious how it can know what devices are using electricity and how accurate the information on my bill is.

submitted by /u/Tavaman
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Why is HIV /AIDS more prevalent among LGBTQ community?

Posted: 17 Sep 2018 11:23 PM PDT

I hope this is the appropriate sub for this question.

submitted by /u/bluewindowcurtains
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It seems just about everyone here is on some kind of antidepressant medication and the majority are American - so are Americans more depressed or do doctors in the USA over prescribe antidepressants? Or is the usage similar in other countries?

Posted: 17 Sep 2018 05:54 AM PDT

Does anyone know the statistics for certain drugs for multiple countries - for example medicine "A" has a 1 in 20 person usage rate in UK vs 1 in 11 for the USA?

Are people more likely to be prescribed something in a country with subsidized medicine or without?

submitted by /u/crikeyyafukindingo
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We vaccinate millions of dogs and cats for rabies at a relatively low cost. Why don't we routinely vaccinate people for rabies too?

Posted: 17 Sep 2018 08:29 AM PDT

How do you find an electron configuration and what do the group mean (s, d, p, f, etc.)?

Posted: 17 Sep 2018 02:49 PM PDT

Monday, September 17, 2018

[Physics] Pauli's exclusion principle states that no two fermions can occupy the same state, but how come it only seems to be relevant when the fermions are also really close?

[Physics] Pauli's exclusion principle states that no two fermions can occupy the same state, but how come it only seems to be relevant when the fermions are also really close?


[Physics] Pauli's exclusion principle states that no two fermions can occupy the same state, but how come it only seems to be relevant when the fermions are also really close?

Posted: 17 Sep 2018 05:26 AM PDT

In the derivations I've seen, Pauli's principle is -in principle - independent of the distance between the particles. And I can't wrap my head around why this doesn't seem to be the case in real life situations

submitted by /u/ElisaKristiansen
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How do our brains deciding which words to use when talking aloud?

Posted: 17 Sep 2018 06:02 AM PDT

I don't know about you guys, but when I talk aloud there's not a whole lot of planning going on upstairs. I'm not visualizing any words, yet coherent sentences come flowing out of my mouth. How does this happen? Who is calling the shots up there? This seems completely opposite to how I communicate through text, where I'm visualizing the words on my keyboard and screen as I think and type them out.

I feel like this Michael Scott quotes demonstrates this phenomenon best.

submitted by /u/TheRedTuke
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Why dont more people in the US get illnesses from mosquitoes even though the same mosquito may extract blood from several hosts?

Posted: 16 Sep 2018 05:01 PM PDT

If a mosquito extracts blood from a squirrel, and then gets blood from you, and then gets blood from some other person, and so on, wouldnt their be a prevalence of some kind of disease spreading from host to host?

submitted by /u/HuskoDoggo
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If I am standing on a beach at sea level, how far can I see into the horizon?

Posted: 16 Sep 2018 06:18 PM PDT

Assume it's a clear day with perfect visibility and you're looking out to sea?

Edit: I'm so bad at phrasing.

I was trying to ask how far away could you see the clouds

submitted by /u/Effendoor
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What is the relation between kVp and Dose?

Posted: 17 Sep 2018 06:13 AM PDT

Hello, I have a question in regards to medical x-ray imaging. I have heard mixed things and cannot figure out if using lower kVp will result in a higher or lower dose. I was always under the impression that higher energy x-rays are more harmful, however if the penetration of the beam increase with kVp then wouldn't the radiation absorbed in the patient also decrease? Also, does this mean that very high energy radiation essentially isn't harmful because it a travels through the patient? Any answers to this or kVp vs dose in general are appreciated.

submitted by /u/mr_charles96
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What is a quiescent active region on the sun?

Posted: 16 Sep 2018 07:39 PM PDT

I'm researching the coronal heating problem for a class, and I am confused about the term "quiescent active region". It shows up frequently in journal papers talking about nanoflares and Alfven waves.

submitted by /u/Joshbecker117
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How legitimate is the technology showcased in this Vice video that transforms CO2 into a carbon-neutral source of fuel for existing vehicles?

Posted: 16 Sep 2018 04:58 PM PDT

https://www.youtube.com/watch?v=Mb_8DJF6Hp0

If it sounds too good to be true, it probably is. But nevertheless, what's your opinion? Do you think this technology is legitimate? If it is, how likely / soon would it be implemented across the world to finally bring greenhouse gas emissions under control? This sounds like a huge turning point in the fight against climate change but I'm very skeptical.

submitted by /u/wirecats
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Why executable programs can't be reverse engineered to reveal their source codes?

Posted: 16 Sep 2018 10:43 AM PDT

It seems to me that compiling a source code and generating an executable is a deterministic process. Therefore, it may be ways to obtain the source reversing the process. Is there some kind of encryption involved?

submitted by /u/PolloWarrior
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How does getting the flu shot work if your bodys t cells remimber the virus, why get it every year?

Posted: 16 Sep 2018 08:09 AM PDT

So our body will remember a virus that has entered and been defeated . So then why is it we get the flu shot every year ? Do they just give you multiple flu virus strains ? Or is it a single virus strain every year. My guess is that they pick a strain that they think will be going around that year . Any answers are appreciated

submitted by /u/commandercody95
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Are big veins and a good blood circulation linked?

Posted: 16 Sep 2018 06:47 AM PDT

What are the theoretical limits of thermionic vacuum tube technology?

Posted: 16 Sep 2018 08:45 AM PDT

As we know, thermionic tubes were largely replaced by semiconductors in the mid-20th century, as the latter technology features a number of advantages, including cost, efficiency, reliability and size... Now suppose, for the sake of discussion, semiconductors were never discovered or invented, and we had to try and improve thermionic tube technology instead. Could thermionic tubes have been made significantly more reliable, and possibly even miniaturized? Is it theoretically possible to build something like a crude integrated circuit with lots of tiny tubes instead of transistors?

submitted by /u/MisterRzzzzz
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Why do objects appear smaller the further away they are?

Posted: 16 Sep 2018 08:31 AM PDT

[Biology] How does a decrease in entropy lead to an increased reaction rate in enzymes?

Posted: 16 Sep 2018 08:17 AM PDT

So there's a lot going on when enzymes catalyse reactions. Here's my current understanding: When an enzyme binds a substrate it releases energy when those bindings form. It also stabilizes the substrate and manipulates it's position and conformation to reach the transition state.
Now in the book the principles of biochemistry 5th edition by Moran it reads:

binding of a substrate near a catalytic active-site residue decreases the activation energy by reducing the entropy while increasing the effective concentrations of these two reactants.

So my question is how this loss in entropy lowers the activation energy. Does it have anything to do with Gibbs free energy or am I looking in the wrong direction?

submitted by /u/FoolishBiologist
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Can somebody explain how nitinol engine works?

Posted: 16 Sep 2018 07:54 AM PDT

How exactly does contraction and expansion of a wire makes wheels rotate?

submitted by /u/Let_me_tug_it
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When a star goes supernova amd collapses into a black hole, how much of thay star's mass becomes the black hole?

Posted: 16 Sep 2018 07:14 AM PDT

What are these beams (?) of I don't know what in the sunset?

Posted: 16 Sep 2018 07:07 AM PDT

https://imgur.com/gallery/WefHGA2

That's the link to a picture I took yesterday. I noticed that the sunset had... some kind of lines? Beams? Not sure what to call them, but hopefully you see what I mean. Could anyone tell me what those are and why they form? Does every sunset have these or is it just this one?

P.S. sorry I'm posting this the third time. I seem to have failed past two times, first by not making the title a question and second by not adding a flair lol

submitted by /u/Tomytomtom1
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Why do endorphins cause respiratory depression?

Posted: 16 Sep 2018 07:04 AM PDT

From my understanding, the body releases endorphins in dangerous situations (serious injury) to lessen the pain and to help us make sensible decisions. Besides that, I read that they cause respiratory depression, but why would your body want to suppress your breathing?

submitted by /u/F4hrenheit
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