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Saturday, May 9, 2020

why high-speed wind feels colder?

why high-speed wind feels colder?


why high-speed wind feels colder?

Posted: 09 May 2020 06:00 AM PDT

why high-speed wind feels colder?

submitted by /u/SomeGuy10004
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Is there a fundamental and consistent difference between fields that follow the inverse-square law and fields that follow the inverse-cube law?

Posted: 09 May 2020 06:06 AM PDT

Inverse-square: gravity, electrostatics, etc.

Inverse-cube: magnetic

submitted by /u/barnabyg2
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Did dinosaurs shed their skins in big patches like modern lizards and snakes?

Posted: 08 May 2020 01:38 PM PDT

Can Lorentz transformations be written as a matrix transformation?

Posted: 09 May 2020 07:33 AM PDT

So I was looking at some videos online which show how a matrix transformation would look like from a vector perspective, and it reminded me of another video which showed how a coordinate system would transform under the Lorentz transformations.

So my question is can this be done? If so then wouldn't it be more compact to write it that way?

submitted by /u/dark_bits
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Alpha centauri apparently has 3 suns orbiting each other. I understand how 2 objects can orbit without colliding, but how can 3 do that?

Posted: 08 May 2020 05:34 PM PDT

Are the phases of the moon the same throughout the world?

Posted: 08 May 2020 09:45 PM PDT

Are the phases of the moon the same throughput the world? For example if there is a full moon where I live will there also be a full moon the same night on the other side of the world?

submitted by /u/JMDStow
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Do black holes cores emit photons that just can’t escape to the surface?

Posted: 08 May 2020 06:34 PM PDT

Can a gas giant have a solid core?

Posted: 09 May 2020 03:43 AM PDT

Could the core of a gas giant be solid like a rocky planet? Could someone theoretically "walk" on it if they had a space suit that kept them from getting obliterated (for argument's sake)?

submitted by /u/OutsideSpring
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When you make a pinhole camera with a large hole, the resulting image becomes blurry. How do our eyes maintain a sharp image in the dark, when our pupils drastically expand?

Posted: 08 May 2020 07:06 PM PDT

How are video games “ported” to other consoles and PC?

Posted: 08 May 2020 02:55 PM PDT

When a video game is "ported" from one system to another, say PC to Playstation, how difficult is this process? Is the entire game rewritten in the code that each system reads? Or does a PlayStation interpret the same kind of programs/code that a PC interprets?

submitted by /u/Bad_Jimbob
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I have an over the air TV antenna. Why do things like microwaves, air mattress pumps and trucks driving by mess with it?

Posted: 08 May 2020 07:03 PM PDT

I've been living with my mama these past two months and she has one of those antennas. Wondering how these things affect them and if we can do anything to help with it.

Sorry if I picked the wrong flair, but I made my best guess.

submitted by /u/tahitianhashish
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Why is it when people are paralyzed from a spinal injury, their internal organs (lungs, heart etc.) can still move?

Posted: 08 May 2020 06:40 PM PDT

It is not uncommon to hear someone was paralyzed from a spine injury, so is it possible for your essential organs(like the heart) to also be paralyzed?

submitted by /u/mero1519
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Is there a size limit to phagocytosis?

Posted: 08 May 2020 05:51 PM PDT

My understanding is that antigen presenting cells phagocytosis a pathogen and are leftover with antigens. What if it's a big parasite or cancer cell thats too big how do they get the antigens to present to start a adaptive response.

submitted by /u/XS905
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Do cats have long term memories?

Posted: 08 May 2020 10:04 AM PDT

I'm wondering what we know about the ability of our feline friends to remember things long term. In particular, do cats remember events, people, other cats from years past? I understand that if kittens are separated at the normal time (about three months of age) they tend to forget their litter mates and don't respond in any particular way if the meet as older cats, but once they're adults does that change? Say if you have two cats for several years, and one leaves or dies, does the other one tend to remember the lost one long term or do the memories fade after a period of time. So I guess my question is if cat's form long term event memory is comparable to ours or not.

submitted by /u/cugamer
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For your lips, how do your cells know when to go from being regular skin cells to being lip cells? And then lip cells to mouth cells?

Posted: 08 May 2020 09:43 AM PDT

Like going from your chin and working up, you have skin cells. Then all of the sudden it's your lip. Is there a hard line where cells stop being skin cells and start being lip cells? Are there some 50/50 cells that are part lip and part chin as the skin moves from being chin skin to lip skin?

submitted by /u/offspringer
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Can you improve your visual acuity?

Posted: 08 May 2020 12:06 PM PDT

Hello, I am a bit lost in learning about eyes and glasses.

First, I'm farsightness and astigmatism. My glasses prescription is: Right Eye: +3.50 Sphere - -0.75 Cylinder - 166 Axis Left Eye: +4.00 Sphere - -1.50 Cylinder - 170 Axis

The plus sphere corrects farsightness only and cylinder/axis corrects astigmatism, right?

Now, my visual acuity for both my eyes are around 20/70. For a distance of 1.30m between my 30 inches TV computer (1080p) and my eyes, I have difficulty reading characters less than 20-25 font size depending of the font and contrast. It is unfortunate especially when playing some games that involves a lot of dialogue or and text. I have Usher Syndrome which includes Retinis Pigmentosa, I can see fine in my central vision and some parts of my peripheral vision. It is also why if I get closer to my screen, I will be able to read small characters but won't be able to see the whole screen because of my poor peripheral vision.

Now, my questions are: Can you possibly have 20/20 while wearing farsightness/astigmatism glasses?

I just noticed that I unconsciously strain my eyes almost all the times while wearing glasses and when I realized about it, I try to fully relax my eyes and noticed that the focus became 20% blur especially on the near. (Less bluer than when taking off glasses of course) It doesn't even give me headache or anything. Is this a bad sign, does that means, I must get a new prescription? From what I understand, glasses prevents eyes strain at all.

Could not wearing glasses that corrects farsightness (Just wearing glasses that corrects astigmatism) and try to not strain my eyes.(Seeing blur all the times) improve my visual acuity and making the focus less blur over time? (I considered about traveling without glasses, no near focus involved most of the time)

And finally, I'm wondering if retinis pigmentosa does also affect visual acuity.

Thanks!

submitted by /u/Cupnoddleismyfetish
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A billiard ball colliding off a mirror loses momentum and thus energy. If a photon reflects off a mirror, does it lose momentum, energy, and thus shift to a higher wavelength?

Posted: 08 May 2020 10:15 AM PDT

Friday, May 8, 2020

Do rainbows contain light frequencies that we cannot see? Are there infrared and radio waves on top of red and ultraviolet and x-rays below violet in rainbow?

Do rainbows contain light frequencies that we cannot see? Are there infrared and radio waves on top of red and ultraviolet and x-rays below violet in rainbow?


Do rainbows contain light frequencies that we cannot see? Are there infrared and radio waves on top of red and ultraviolet and x-rays below violet in rainbow?

Posted: 08 May 2020 07:13 AM PDT

If I put a refrigerator in a room with the lid open, does the room get warmer, cooler, or stay the same?

Posted: 08 May 2020 07:23 AM PDT

Why does brown sugar harden, and how come putting a slice of bread in a container of hard brown sugar soften it?

Posted: 08 May 2020 07:44 AM PDT

I'm a materials scientist, so from a crystallographic point of view I'd imagine the sugar, when exposed to air, crystalizes in such a way that locks and prevents movement between sugar grains. If this is true, why would the crystals form when exposed to air from a scientific perspective? Additionally, what function does putting a slice of bread inside hardened brown sugar serve? Does it absorb moisture thus allowing sugar crystal movement again?

submitted by /u/Fin_Olesa
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If scientists are unsure about COVID-19 antibodies providing long-term immunity and preventing re-infection, why should we hope for anything different from a vaccine?

Posted: 07 May 2020 05:41 PM PDT

To be clear, I'm not anti-vaccination. I'm very much pro. But if the idea behind a vaccine is that the antibodies will provide immunity, but that we don't have evidence that these antibodies are doing that, then why are we so confident a vaccine is the answer?

submitted by /u/cshake93
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Why high end audio equipment tend to have higher impedance?

Posted: 07 May 2020 11:58 PM PDT

I just got myself a Shure SM58 as a mic which has an impedance of 300 Ohms compared to the 150 of my previous, lower end microphone. Same goes with headphones with some high end models going in the range of 200/300 Ohms while common earbuds sit at around 30 Ohms. The basic principle across all of those devices is the same, being magnetic induction so why higher impedance is preferred for good audio quality? Does the fact that by increasing resistance the inductance (which complex impedance varies with frequency) is less important so the response at the various frequencies is more constant? I'm a physics undergrad so you can go pretty deep with technical explanation if you want, I hope to be able to understand it.

submitted by /u/R3NTZ_
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Can the blood plasma extracted from a person of one blood type be given to someone of a different blood type?

Posted: 08 May 2020 12:38 AM PDT

So there's some hope of giving blood plasma from COVID19 recoverers to those that are infected and high risk of death. Would donor and recipient of the plasma have to be of the same blood type? Or does the separation process remove that requirement?

submitted by /u/PickUpYourFries
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How does the coronavirus/COVID19 test detect the presence of the virus?

Posted: 08 May 2020 08:15 AM PDT

I tagged chemistry because I guess it would be to do with that?

To elaborate, what is actually done with the sample to find the virus? Is it like just put in a computer and it detects... something? Or do you put the sample in a solution and then it goes purple for positive and a bluer purple for negative? I'm just curious about the process and how it works after the initial swab that we see from the side of being tested.

Hope this doesn't violate any rules, and isn't too broad a question, and I'm sorry if the flair's wrong.

submitted by /u/Greaseball01
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Political Science Question. Since universal healthcare is such a dividing topic, why can’t states just do it on an individual state level due to federalism?

Posted: 08 May 2020 04:57 AM PDT

I was thinking, just like how legal marijuana was unfathomable a decade ago but thanks to individual states trying it out it's now slowly spreading across the country. Why can't the same be done with single payer healthcare?

Isn't that why states have these rights? So they can act as testing grounds for ideas?

Thanks

submitted by /u/Tattoomyvagina
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Do all psychoactive drugs work by either being an agonist or antagonist for certain neurotransmitters?

Posted: 07 May 2020 05:56 PM PDT

Why are some scars permanent? Why do they last longer than your other skin cells?

Posted: 07 May 2020 03:30 PM PDT

Why don't scars just slough off over time like your skin? What about them makes them more permanent?

submitted by /u/selesnyandruid
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Why is the moon covered in so many craters but the Earth isnt?

Posted: 07 May 2020 02:26 PM PDT

Why does the Earth have seemingly so few large craters unlike the moon? Weren't they created at the same time? And technically, since the moon is smaller shouldn't it have a lesser chance of being hit? Or were the craters on the moon not created my meteorites?

submitted by /u/ppaannggwwiinn
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Do animals feign death intentionally or is it uncontrollable reflex from a threat?

Posted: 07 May 2020 04:48 PM PDT

I saw a popular and funny video of a snake faking death by turning upside down. When the person with camera turn it back over it continuously turn back upside down over and over. It seemed like the snake could have quickly scurried into bushes to get away, but it's just kept turn upside down over and over again.

Can animals control this behavior or is it a reflex that they can't control?

submitted by /u/wiserone29
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How does algae cells assimilate phosphorus?

Posted: 07 May 2020 05:39 PM PDT

I was wondering how plant cells take in phosphorus. For an example when phosphorus from fertilizer gets into a nearby lake. Then the algae take in the nutrients, and can create blooms of algae. How exactly does the the phosphorus get into the cell through the cell membrane. I have tried to find pictures, but I can't seem to find any. Thank you in advance!

submitted by /u/ScienceNature
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How does the liver know the appropriate enzymes to secrete to break down food?

Posted: 07 May 2020 12:44 PM PDT

Green peppers are hollow. How does the air get inside? Also, what would be the evolutionary advantage of being hollow like that?

Posted: 07 May 2020 02:28 PM PDT

Did the chromatophores of the chameleon and octopus evolve in parallel, or do they derive from a common ancestor?

Posted: 07 May 2020 03:15 PM PDT

How are tectonic plates mapped?

Posted: 07 May 2020 12:59 PM PDT

I was just reading this post about volcanoes and it got me thinking- how do we know where the boundaries of the tectonic plates are? How precisely can we know the boundaries?

submitted by /u/Orpheus91
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How can poliovirus and other pathogens lead to permanent conditions if the bodies adaptive immune system is still functioning?

Posted: 07 May 2020 11:50 AM PDT

What makes different parts of the brain carry out functions?

Posted: 07 May 2020 05:15 PM PDT

I have been searching on the internet but can't seem to find any explanation to why distinct areas from the brain ,like lobes for instance, carry out tasks that don't have anything to do with each other if they are all made up by the same nervous tissue. Are chemical receptors the key to what each area is responsible for, is it the architecture, or is it something else?

submitted by /u/Michael_Arter
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Why can't you untoast toast, or unburn wood?

Posted: 07 May 2020 08:36 PM PDT

Thursday, May 7, 2020

Can my 7 year old ask you about tornadoes?

Can my 7 year old ask you about tornadoes?


Can my 7 year old ask you about tornadoes?

Posted: 07 May 2020 09:57 AM PDT

So my son has high functioning autism and he is obsessed with tornados. He is 7 and constantly pesters his mom and myself with questions. I know the basics but I am hoping that the more knowledgeable of you can provide more correct answers that I can simplify for him. And any other super cool facts wold be super appreciated!

Tornados:

  1. How do tornadoes create a vortex?
  2. How are their winds so strong?
  3. How do tornadoes form their eye?
  4. Is the center of the tornado the strongest part?
  5. How do tornadoes crush items that it sucks up?
submitted by /u/Captainj321
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Can my 7 year old ask you questions about volcanoes?

Posted: 07 May 2020 09:55 AM PDT

So my son has high functioning autism and he is obsessed with volcanos. He is 7 and constantly pesters his mom and myself with questions. I know the basics but I am hoping that the more knowledgeable of you can provide more correct answers that I can simplify for him. And any other super cool facts wold be super appreciated!

Volcanoes:

  1. How do volcanoes blast off their tops?
  2. How do volcanoes form rocks?
  3. How do volcanoes form/receive lava?
  4. How much force does a volcano produce when erupting?
submitted by /u/Captainj321
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Why is frame-dragging limited by the speed of light?

Posted: 06 May 2020 06:27 PM PDT

One of the explanations I've seen for why black holes can't spin faster than c (at the event horizon) is that this would cause objects to be frame-dragged (frame-drug?) at superluminal speeds as seen by a distant observer. But frame-dragging is the warping of space, and as we see with the cosmological expansion of space and theoretical technologies like an Alcubierre drive, space itself isn't prohibited from moving faster than light relative to other areas of space and carrying matter along with it.

submitted by /u/KingSupernova
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How does the earth's axial tilt influence climate? If it is more tilted, is the overall climate at the poles warmer?

Posted: 07 May 2020 08:59 AM PDT

I read that greater tilt in Earth's axis balances solar radiation over a greater surface area. Does this mean that if earth's tilt is greater, the north pole would be cooler? I thought that if the earth was more tilted the northern latitudes would be warmer since more ice would melt during the summer. Is this wrong? I'm not sure since then wouldn't more ice form during the winter too? I know that melting ice can lead to a cascading effect where more sunlight gets absorbed (the reverse for forming ice). Which process would be stronger, in this case?

submitted by /u/MegaFatcat100
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Theoretically, would a significant (sci-fi significant) change in the density of rock etc of a planet and its layers be able to create significant gravitational differences in different places around a planet? (Providing the rock has different densities in different places)

Posted: 07 May 2020 05:40 AM PDT

I'm currently theorizing some ideas for a story I'm planning on writing and I wanted to get the communities opinion on this, if I'm even in the correct ballpark! (This is all theoretical so aside from the impossibility of this forming naturally I wanted to query if it's possible theoretically)

If the density of material in 1km2 (from the surface to the core of a planet) were (x) times more dense than in another would there be a number significant enough that gravity would be 2x or even 5x stronger?

If not is there a way that this could occur on paper that would make any scientific sense for significant localised gravitational differences across a planet's surface? (Kind of like how earth has super small differences in gravity but much stronger and with more defined borders of strength)

submitted by /u/PuddleofExistential
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Why are superconductors used as thick bundles if they have 0 resistance anyway?

Posted: 06 May 2020 01:23 PM PDT

In machines such as ITER I see thick bundles of superconductors. The only reason I know would be to increase cross section to lower resistance and thus allow more current at the available voltage. But resistance is 0 anyway, why does it need to be thick?

submitted by /u/AStove
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How does the sun provide vitamin D?

Posted: 06 May 2020 02:52 PM PDT

I read a little about what uv rays do to cholesterol, but I don't understand why we'd need the sun to "produce" vitamin D. If someone could explain the whole phenomenon a little bit more I'd appreciate.

submitted by /u/Girlsolano
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What is the difference between magnetic and electric fields?

Posted: 06 May 2020 01:00 PM PDT

What exactly is the difference between magnetic and electric fields? I've got the impression it's basically the same thing accept electric fields are produced only by electricity and magnetic fields are produced by magnets (and electricity?). Could someone just explain it simply, preferably without using too complicated sciency words! Thanks.

submitted by /u/13245768900
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Why don't all gas pipe flows end up at sonic speed?

Posted: 06 May 2020 01:58 PM PDT

According to the 1D models of compressible fluid flow, the effects of pipe wall friction and the effects of heat addition from the environment both drive a flow toward Mach 1 (i.e. the speed of sound). Whether the flow starts of supersonic (M > 1) or subsonic (M < 1), the M = 1 condition is the maximum entropy point. Wall friction will actually cause a subsonic flow of gas through a pipe to accelerate up to M = 1 (I still have difficulty wrapping my head around this). So why then don't we find that all gaseous flows through a pipe ultimately end up with sonic flow velocities?

I also do not understand what happens after the flow reaches M = 1. The textbooks I've read just say "if there is still pipe length left or heat addition past the point of M = 1, then the inlet conditions must spontaneously change such that the flow reaches M = 1 at the end of the pipe." But they do not explain what these changes are or what mechanism enforces them. What if I am controlling the inlet conditions to be, say, a certain pressure? Then what happens at the end of a rough walled pipe if the flow reaches M = 1 in the middle?

TL;DR: Entropy is maximized when a compressible fluid flow velocity through a pipe reaches the speed of sound. So why aren't all our natural gas pipelines carrying gas at the speed of sound?

submitted by /u/Bellgard
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How is the accuracy of a COVID-19 test determined (virus and antibody alike)?

Posted: 06 May 2020 02:32 PM PDT

So from my understanding, to determine the accuracy of a test, you have to rule out false negatives as well as false positives. False negatives should be easy as they can just test on people who have (or in case of an antibody test, already had) the disease. However, due to the large amount of asymptomatic infections, I can't wrap my mind around on how they'd determine those. If they test someone who didn't have symptoms and it tests positive, how do they know if they really had COVID-19 or if it's just a false positive? Are there other ways to determine this without testing people?

submitted by /u/SirAnducar
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How is air regulated on the ISS? What concentrations of oxygen and other airs are used?

Posted: 06 May 2020 10:45 AM PDT

I was wondering how air the astronauts breath is regulated and made. Is the oxygen 21% like it is on Earth? Is there nitrogen? Other trace airs? I assume there's CO2 as they need to breath out. Anyway thanks in advance.

submitted by /u/emirra1979
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Magma is molten rock under a planet's surface. Lava is molten rock that comes up through a volcano. Is there a technical/specific name for molten rock that originated on the surface, like a planet that hasn't cooled or the rock that melts from an asteroid impact?

Posted: 06 May 2020 09:37 AM PDT

Can an unvaccinated dog who is shedding the rabies virus through saliva get vaccinated for the first time and not develop symptoms?

Posted: 06 May 2020 03:39 PM PDT

I have tried googling this question and haven't found an answer. I wasn't sure if this was the right subreddit, but figured I would ask. Thanks!

submitted by /u/alaskandaisy
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