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Saturday, December 4, 2021

How can 30-40 GPS satellites cover all of the world's GPS needs?

How can 30-40 GPS satellites cover all of the world's GPS needs?


How can 30-40 GPS satellites cover all of the world's GPS needs?

Posted: 03 Dec 2021 05:35 AM PST

So, I've always wondered how GPS satellites work (albeit I know the basics, I suppose) and yet I still cannot find an answer on google regarding my question. How can they cover so many signals, so many GPS-related needs with so few satellites? Do they not have a limit?

I mean, Elon is sending way more up just for satellite internet, if I am correct. Can someone please explain this to me?

Disclaimer: First ever post here, one of the first posts/threads I've ever made. Sorry if something isn't correct. Also wasn't sure about the flair, although I hope Engineering covers it. Didn't think Astronomy would fit, but idk. It's "multiple fields" of science.

And ~ thank you!

submitted by /u/PsyFiFungi
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Can our eyes feel temperature?

Posted: 03 Dec 2021 04:55 PM PST

I know this sounds dumb but I noticed today while it was near freezing that my eyes are the only part of my face that wasn't immediately or subsequently cold. Is this just because we blink a lot, or smaller blood vessels, or what?

submitted by /u/ElegantEpitome
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Why don't astronauts on the ISS wear lead-lined clothes to block the high radiation load?

Posted: 02 Dec 2021 07:11 PM PST

They're weightless up there, so the added heft shouldn't be a problem.

submitted by /u/gatfish
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Where is there more gravity? In the center or the surface of a planet?

Posted: 03 Dec 2021 09:08 AM PST

Why are rocket fuels like Hydrazine (N2H4) and other hypergols so toxic?

Posted: 03 Dec 2021 03:47 PM PST

So in my field of work occasionally we have some nasty chemicals around like N2H4 hydrazine. We always have a load of safety measures around it and I understand the hazards around pressurized systems, heat from reaction, containment etc but everyone always says it's incredibly toxic and carcinogenic.

My background is in physics and engineering, not biology and I've always been curious WHY it's so carcinogenic. What is it doing to your body that your body hates so much? It's it a burning damage that it causes your organs that are then damaged so much it can lead to cancer or is there more going on?

Thanks

Edit: just to clarify I'm curious as to the biological or chemical reactions that make Hydrazine dangerous to human bodies. I understand the hazards from a combustion/press system/explosion standpoint, and I know it's dangerous humans past that But why does inhaling some send you to the hospital? What is it doing to your body? I feel like there is more going on than just internal burning line you'd see with peroxide or simply caustic chemicals.

submitted by /u/Afireonthesnow
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Are all omicron cases directly linked back to a single case? Or could they have arisen independently?

Posted: 03 Dec 2021 01:24 PM PST

Basically the title- are different variants unique enough that they would have spread from one source, or could it be a "logical" mutation that could occur independently in different areas?

submitted by /u/jackwhite886
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Is there a difference in your level of immunity between getting COVID first and then the vaccine vs vaccine first and then exposure to COVID?

Posted: 03 Dec 2021 11:57 AM PST

TL/DR is there a difference between getting COVID and then the vaccine VS getting the vaccine and getting exposed to COVID in our immune response.

When it comes to post-infection immunity (Natural Immunity as it's so commonly called) I am a bit confused, as someone who has their two doses and will get their booster when eligible is it still possible for me to build a more robust defense by being exposed to the full virus despite being immunized?

As the mRNA vaccines aren't sterilizing does getting exposed to the live virus (but not getting sick) give my body enough opportunity to build a fuller picture immune response?

submitted by /u/TheRightMethod
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How do signals from our equipment on other planets make it through the earths core?

Posted: 03 Dec 2021 08:36 AM PST

Or do we wait to send signals and pictures back until the receiving side of the earth is facing the direction the signal is coming from?

submitted by /u/DoodiePootie
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Does repeated exposure to Covid increase the risk of a breakthrough infection?

Posted: 03 Dec 2021 03:57 PM PST

Is the risk of a breakthrough infection mostly systematical or statistical? So is there simply a subset of people who will not have adequate protection after being vaccinated, or would everybody get sick eventually if they were exposed often enough? I seem to remember that for different vaccines, it's mostly that some people just don't respond well, but I can't find anything to back this up.

submitted by /u/chaoschilip
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How does a dummy piston / balance piston work on a steam turbine?

Posted: 03 Dec 2021 02:30 PM PST

I'm trying to figure out how they reduce the axial thrust on the rotor.

submitted by /u/The-Keg-Man
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How does slingshotting around planets not break the laws of physics?

Posted: 03 Dec 2021 07:45 AM PST

Spaceships or probes supposedly use large gravitational bodies as a "slingshot" to build up speed, but... how? No matter the angle, you go towards it, and then you go away from it. How can you get more speed/energy out of this? By this logic, you could keep slingshotting around a handful of planets and keep going faster and faster forever, but this doesn't seem right at all. Can someone please explain?

submitted by /u/Jonnny
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Does the vaccine reduce transmission of the Delta variant?

Posted: 03 Dec 2021 05:52 AM PST

Are there any studies on the transmission of the delta variant and whether the Pfizer/Moderna vaccines reduce transmission?

submitted by /u/liberrimus_roob
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Why is the gender gap in life expectancy so low for some countries and so high for others?

Posted: 02 Dec 2021 08:59 PM PST

I was looking at the life expectancy for different countries for fun and noticed the gender gap differed quite a lot and doesn't even seem consistent across similar countries. (This is all 2018 data)

Nigeria has the smallest gap I could find: 1 year. Men and women live a pretty similar length there. But other high poverty countries have a much bigger gap. Egypt is 5 years. Ethiopia is 4.

Then we have more developed countries, with the smallest gap I could find being Sweden, with 4 years. Finland is 6.

Why is there such a wild difference even among similar countries?

submitted by /u/YayCookiesForever
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What impact would anti viral pills have on COVID recovery anti-bodies?

Posted: 03 Dec 2021 05:28 AM PST

Was talking to friends about news that Pfizer's anti viral pills wouldn't be negatively impacted by the new variants & got asked if these pills would stop your body from developing anti bodies that you'd normally get from a COVID recovery. So would you have to keep taking the pills every time you tested positive? Couldn't find anything online about it so figured I'd ask here & see if anyone here knew anything. Thanks for reading.

submitted by /u/NandoFlynn
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When it’s said that the mantle is fluid, how fluid are we talking here? What kind of texture is it?

Posted: 02 Dec 2021 02:06 PM PST

What devices detect and measure airborne particles?

Posted: 02 Dec 2021 08:57 PM PST

Additionally, what units do they measure in? And what is a range of possible measurements one might get for airborne pollen during spring?

submitted by /u/CrownedInFireflies
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How does GPS give turn by turn directions?

Posted: 03 Dec 2021 08:10 AM PST

I saw another question asking about GPS and it made me want to ask a question I've always wondered. How does GPS calculate a map with precise turn by turn directions, and expected arrival times?

I know the US military had GPS in the 90's which was a huge advantage in the Gulf War, but when the technology existed then did it have that capability?

submitted by /u/Lego_Eagle
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Thursday, December 2, 2021

AskScience AMA Series: We're here to answer your questions on living with the invisible symptoms of Multiple Sclerosis (MS), AUA!

AskScience AMA Series: We're here to answer your questions on living with the invisible symptoms of Multiple Sclerosis (MS), AUA!


AskScience AMA Series: We're here to answer your questions on living with the invisible symptoms of Multiple Sclerosis (MS), AUA!

Posted: 02 Dec 2021 04:01 AM PST

Multiple sclerosis is a complex disease that affects the central nervous system, including the brain, spinal cord, and optic nerve. Many of its symptoms are easily noticed, like gait, balance, tremor, and speech. But others are not visible to the naked eye - like fatigue, cognitive dysfunction, and pain - and make day-to-day life with the disease difficult to navigate for the more than two million people living with MS globally. Today from 11a - 2p ET (16-19 UT), Patricia Coyle, MD and Patricia Melville, RN join us to take your questions about the invisible symptoms and disease related to MS.

MS Team Meeting: The Impact of the Invisible Symptoms of MS is a new four-part video series featuring Coyle and Melville for The Journal of Clinical Psychiatry. Watch as they share an in-depth conversation with Lillian, a woman with MS for the past 30 years who shares a candid account of life with this disease.

Patricia K. Coyle, MD is the director of the MS Comprehensive Care Center and professor of neurology at Stony Brook Neurosciences Institute.

Patricia Melville, RN, NP-C, CCRC, MSCN is a supporting specialist at Stony Brook Neurosciences Institute.

Learn more about multiple sclerosis in the MS Clinical Resource Center.

PROOF: https://i.redd.it/1bgctzp8yt281.jpg

Username: /u/PsychiatristCNS

submitted by /u/AskScienceModerator
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What are the current COVID tests in use that are capable of determining the exact variant being detected as present? How do they do it?

Posted: 02 Dec 2021 01:18 AM PST

With the recent discovery of Omicron and it's apparent rapid transmission and positive identification across the globe, how do current COVID tests determine which variant is being detected as present? Which tests have this capability? I have only ever seen tests that detect the presence of a coronavirus, but not the exact variant.

If the Omicron variant was just discovered days ago in South Africa, how would tests already in use in Europe, USA and Asia be able to not only detect the presence of but also positively determine which variant was detected, especially when that variant was not known to exist until this week?

submitted by /u/Reddit-eur
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Where do common cold and flu infections come from?

Posted: 02 Dec 2021 05:16 AM PST

My question is about the human virome and wether you get get sick with a cold or flu without any human to human interaction (aka in isolation).

I know that, for example, staph bacteria is normally found on the skin of healthy individuals and then occasionally become pathogenic if they get into skin pores, or skin cuts or the person's immunity drops.

Does the same thing happen with viruses that cause the common cold or flu?

Are rhinoviruses for example normally found in healthy humans like staph bacteria is found on healthy skin? Do these viruses then become pathogenic due to drops in immune function? Or do all cases of common cold and flu infections come from viruses that a healthy human is exposed to from outside their body?

Thank you so much

submitted by /u/Flobber7
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Dear Astronomers / Physicists, could you help me understand tidally locked planets?

Posted: 02 Dec 2021 05:32 AM PST

I'm curious about tidally locked planets orbiting red dwarves, such as GJ 581g, and their potential for sustaining atmospheres or even life.

As one side of the planet is faced away at all times from its star, do the freezing temperatures that occur prohibit an atmosphere from forming?

Also, in regards to the red dwarves the planets must be orbiting so closely, is radiation due to closer proximity also a problem?

As many have taken the time during the epidemic to explore themselves a little more, I've decided to pick up science fiction writing. As a large part of the story is placed on a tidally locked planet, it's important to me to keep things realistic in a sense. Looking forward what you guys can educate me on.

submitted by /u/JollyBloke
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What SI units are used to measure the highest levels of ionizing radiation?

Posted: 02 Dec 2021 12:40 PM PST

Hi, everyone! So, I'm a volunteer firefighter with an interest in hazardous materials response. One of the aspects that I've always wondered about is the radiological side of things. I've done extensive research into nuclear disasters such as Chernobyl and Fukushima and have always pondered this question. I'd greatly appreciate it if someone could help me out.

submitted by /u/brandondsantos
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Does the expansion of the universe have any effect on the charge (or other properties) of various particles?

Posted: 02 Dec 2021 01:31 PM PST

Just a thought i had while listening to some informational videos

submitted by /u/JasontheFuzz
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How are virus RNA sequenced and what makes sure its accurate?

Posted: 02 Dec 2021 03:55 AM PST

What is the mechanism behind certain covid variants crowding others out?

Posted: 02 Dec 2021 01:40 PM PST

I often hear people talk about this as if one variant is displacing the efficacy of another to spread but I can't figure out why that would be.

My best guess is that this is a misnomer and one does not crowd out another, but instead previous ones taper off and new ones arrive. As those new ones peak it casts the impression that displacing others when in fact the two are on two different infection cycles.

submitted by /u/LiMoTaLe
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How much the COVID treatment improved ?

Posted: 02 Dec 2021 09:59 AM PST

I've seen a lot of news about vaccine development this year but almost none about how much we improved at curing it.

submitted by /u/Aleksandair
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How is it possible that we are running out of water?

Posted: 01 Dec 2021 07:17 PM PST

I imagine this is a common point of confusion. I am aware that only a small percentage of water on earth is freshwater, only a small percentage of that is liquid.

My question is - does the actual amount of fresh water on earth decrease? If not, how is it possible that we are running out? Where is it going?

submitted by /u/blue-ocean-event
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Did Whales always live in pods?

Posted: 01 Dec 2021 05:08 PM PST

Late in the book Moby Dick Ishmael tells the reader that whales only started living in pods as a defense mechanism after humans started hunting them. Is this true? I'm aware Moby Dick takes some liberties with actual science (such as claiming whales are a fish rather than a mammal) but I can't find any information confirming or debunking this particular claim.

submitted by /u/Additional-Metal-263
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Is there any reason to think that the total angular momentum of the visible universe is zero (or non-zero)?

Posted: 01 Dec 2021 01:54 PM PST

Would the opinion change if we consider everything, not only the part of the universe visible to us?

submitted by /u/taracus
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What prevents the vacuum of space from taking earths oxygen?

Posted: 01 Dec 2021 02:05 PM PST

For any (contiguous) territory, is it always possible draw a straight line that divides the territory into parts that are both equal in area and equal in population?

Posted: 01 Dec 2021 07:38 PM PST

The assertion was made at https://www.reddit.com/r/MapPorn/comments/r6jxsh/each_us_state_split_in_half_by_population/hmtqkqq/ that it is always possible to draw a straight line to divide a given contiguous territory into two parts that are both equal in area and equal in population.

For this purpose, assume that when I say "two parts", I don't mean "two parts that are also contiguous." So if I've got a crescent-shaped territory and my line ends up dividing the territory into a "middle" part and two non-contiguous bits that are the horns of the crescent, that line isn't invalid for that reason, if you follow me.

Is the conjecture true? Is it always possible to use a straight line to divide a contiguous territory into parts that are both equal-area and equal-population?

submitted by /u/spikebrennan
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Do the relative positions of stars in the Milky Way change as the galaxy rotates?

Posted: 01 Dec 2021 07:24 PM PST

For example, do they all move as if they are glued in place on a record on a record player, or do they move like items going down the drain, with the central stars revolving more rapidly than the peripheral stars?

submitted by /u/ERDRCR
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How did the shift from unicellular to multicellular life occur?

Posted: 01 Dec 2021 06:16 PM PST

To start off, I'd like to clarify that I'm not doubting the validity of evolution and natural selection. My question is more specific to how cellular life shifted from simple unicellular organisms to a group of cells like sponges, and even organised into tissues in more complex species.

submitted by /u/MazScientist
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Intuitive explanation for slot waveguides?

Intuitive explanation for slot waveguides?


Intuitive explanation for slot waveguides?

Posted: 01 Dec 2021 09:02 AM PST

Can someone help me with an intuitive explanation for optical slot waveguides, where the optical field is confined in a low index cladding slot between two higher index sections?

Basically I am having trouble conceptualizing the math directly into physical intuition - a strip waveguide makes sense since it's just continual refraction of light.

Is it a property of the slot waveguide that it must be sub-wavelength or near-wavelength? For example, obviously two macroscopic strip waveguides near each other do not confine the light inbetween them, and instead within themselves. Or perhaps this is more a property of the dimension of the high index material itself?

A resource would be useful - I read this link but section 2.2 wasn't super clear to me in terms of intuition https://www.intechopen.com/chapters/60221

Any help is appreciated!

submitted by /u/sikyon
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Wednesday, December 1, 2021

Why does earth rotate ?

Why does earth rotate ?


Why does earth rotate ?

Posted: 01 Dec 2021 10:10 AM PST

Why does earth rotate ?

submitted by /u/Zealousideal_Net5391
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Is weathering/erosion of rock by water more due to chemical or mechanical processes?

Posted: 01 Dec 2021 06:47 AM PST

I was reading this page: https://opengeology.org/textbook/5-weathering-erosion-and-sedimentary-rocks/

And while they indicate here that "chemical" weathering is the primary mechanism, wouldn't "mechanical" be the most significant factor? As in, moving/falling water would cause more weathering than still water over the same time period? And wouldn't faster moving water cause more weathering than slower moving water?

submitted by /u/dante662
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Do people respond to acronyms with the same part of their brain as their actual phrases?

Posted: 01 Dec 2021 07:39 AM PST

ALSO: Provided they understand both the phrase and the acronym, will a person respond to an acronym of a phrase and the actual phrase in the same way?

I was texting my friend about how it's weird that people find it easier to talk about the treatment of POWs over the treatment of prisoners of war. He responded a bit later that he had "fallen for it" and didn't really have a visceral response when he read "POWs" but did when he read "prisoners of war" in my text, even though afaik he knows what POW stands for.

I keep trying to find studies on how acronyms affect our thinking in situations like this but I mostly just find the list of abbreviations used in neuroscience with the way I'm searching :P can anyone help me out here?

The first question is more neuroscience but the second is more psychology so sorry if there's a way to add two flairs and I didn't realize it lol

submitted by /u/catfoodtime
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Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology

Posted: 01 Dec 2021 07:00 AM PST

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Economics, Political Science, Linguistics, Anthropology

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here. Ask away!

submitted by /u/AutoModerator
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Why are red blood cells safe from natural killer cells?

Posted: 01 Dec 2021 03:50 PM PST

I'm currently reading Philipp Dettmer's excellent book, Immune. In it, he explains that unlike other immune cells, natural killer cells identify infected/corrupt cells by (among other things) detecting the absence of MHC Class I molecules on the surface of the cell, which are normally in abundance on all healthy nucleated cells in the human body.

In a footnote, he explains that infected red blood cells are safe(r?) from NK cells because they don't have MHC Class I molecules anyway.

What's not explained (as far as I can tell; I haven't quite finished the book) is how the NK cell knows the absence of MHC I on a red blood cell is normal. Is there some other marker that says "I'm a red blood cell" or is there more to activating NK cells than the reduction of this molecule? Or can the NK cells simply not trigger apoptosis in red blood cells for some reason?

I'm not sure if I am missing something or my understanding is just fundamentally incorrect and I should go back and re-read a few chapters.

submitted by /u/Nacimota
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How to obtain energy gain or loss of chemical reactions?

Posted: 01 Dec 2021 04:56 AM PST

Chemical reactions either take or release energy.

So this "energy" must be on either the reactant or at the product side.

What specific chemistry concept is this?

I assume that I need specific computations for getting the energy of all reactants and products as well, how do I obtain this "energy" value as well?

what formulas and table values do I need to use?

submitted by /u/Caidelyn32
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Timeline of a viral infection of one cell?

Posted: 01 Dec 2021 04:24 PM PST

As I understand, a virus spike protein latches to the cell receptor. The viral RNA (or DNA, not sure) gets inside and starts instructing the cell to produce more viruse copies. Eventually, the cell bursts and releases the virus copies.

My question is how long does each step take? Is it super quick like 10 seconds or super long like 10 minutes or more?

submitted by /u/Gal-Gadonut
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Nasal Covid 19 vaccine?

Posted: 01 Dec 2021 03:23 PM PST

Are there nasal vaccines against in development in the USA?

submitted by /u/Suricata_906
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If Omicron spike protein changes wouldn’t it be harder for it to attach to nasal lining cell surface receptors?

Posted: 01 Dec 2021 12:11 AM PST

Can moles cause a landslide?

Posted: 01 Dec 2021 04:01 AM PST

So every once in a while I find their little tunnels when I wake up in the morning, I really do not mind them at all, I'm happy that they get to live in my big land, however I am wondering if there is a risk to the house I am living in.

It's a wood house, its stacked on concrete pillars, it's the size of a fairly big apartment, could moles dig enough tunnels below the house to eventually cause a cave in/landslide?

submitted by /u/tolstoyswager
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Why does South Africa do so much genetic sequencing of COVID viruses in comparison to other countries?

Posted: 30 Nov 2021 04:25 PM PST

What makes a virus more contagious and easier to transmit?

Posted: 01 Dec 2021 12:36 PM PST

We are hearing a lot about the COVID-19 variants. First, one of the dangerous properties of COVID-19 was how easily and quickly it spread, compared to others. Then we got the Delta variant and now Omicron. With each one the WHO and the CDC have said they are more easily transmitted than past versions of COVID-19.

What attributes actually make a virus more contagious and/or more easily spread than another?

submitted by /u/CheddarMonkey36
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What do astronomers mean when they talk about gases in the interstellar medium heated to millions of degrees? Would you experience this "heat" while moving through these gas clouds (i.e. will you get fried away into atomized dust)?

Posted: 30 Nov 2021 07:52 PM PST

For context, this wikipedia article on the Bullet Cluster has the following bit:

"The Bullet Cluster is one of the hottest-known clusters of galaxies. It provides an observable constraint for cosmological models, which may diverge at temperatures beyond their predicted critical cluster temperature.[1] Observed from Earth, the subcluster passed through the cluster center 150 million years ago, creating a "bow-shaped shock wave located near the right side of the cluster" formed as "70 million kelvin gas in the sub-cluster plowed through 100 million kelvin gas in the main cluster at a speed of about nearly 10 million km/h (6 million miles per hour)".[5][6][7] The bow shock radiation output is equivalent to the energy of 10 typical quasars."

submitted by /u/krngc3372
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Do we know how long ago epicanthic folds evolved?

Posted: 30 Nov 2021 07:27 PM PST

I know we are not sure why this trait appeared in people living in certain locations, but we have estimates of when it appeared?

submitted by /u/HomemPassaro
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How much power output is associated with the astrophysical jets of a neutron star/black hole? Is it comparable to the radiation output of a star?

Posted: 01 Dec 2021 02:40 AM PST

And is it possible, in theory, for an advanced civilization to harness this energy to generate power? What are some challenges that might arise if someone tried to do this (is it more feasible than building a dyson cloud/dyson sphere)?

I imagine that the strength of the aforementioned astrophysical jets depends on the size of the black hole/neutron star as well as what it's currently feeding on, and is therefore highly variable. However, if possible I would like to get a rough understanding of the power involved, to within a few orders of magnitude.

Thank you in advance.

submitted by /u/Different-Voice-8315
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How do T-Cells recognize a virus differently than Antibodies?

Posted: 30 Nov 2021 02:42 PM PST

I've seen some people indicate that cellular (T-Cell) immunity to Omicron may be preserved even if neutralizing antibodies are not. I would have thought the T-Cells "learn" the same pattern as the antibodies do by exposure to the spike proteins generated by your body in response to the vaccines. How does it work that T Cells can recognize a mutated virus more effectively than antibodies do?

submitted by /u/Matir
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Is mutational load increase in humans something we should be worried about?

Posted: 01 Dec 2021 01:47 AM PST

https://pubmed.ncbi.nlm.nih.gov/31424543/

Is there an unsustainable amount for humanity? If so, where is the threshold, and what would be the most noticeable consequences of passing it?

submitted by /u/Aquareon
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By how much has COVID reduced life expectancy?

Posted: 30 Nov 2021 05:36 PM PST

This question is based on two assumptions. If either is incorrect, please tell me.

First, to my knowledge COVID is a disease which causes no damage or negligible damage to the large majority of infected people but which causes catastrophic damage or death to a significant minority of infected. Since older people are the most likely to suffer these serious effects, using the impact on life expectancy could be a more useful statistic to indicate the effect the disease has had on public health on aggregate as opposed to raw numbers of infections and deaths.

Second, I am assuming that there is a general upwards trend in life expectancy as time goes by due to incremental improvements in medicine and public health when it comes to dealing with existing threats.

Since it appears that COVID is not going away, I assume that its emergence has had an impact on life expectancy in the long term. Would it be correct to say that this jas set the progress in life expectancy back? Could we calculate by how much? For example could we say that the negative impact of COVID has counteracted 5 years of gains in life expectancy for example?

Since new threats will inevitably appear, can we predict how life expectancy will change in future?

submitted by /u/DVC888
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How do refrigerators maintain temperature?

Posted: 30 Nov 2021 08:56 PM PST

So does the fridge measure the air temperature and work off that? That seems to not be a good measure given opening the door and the volumetric heat capacity of air vs. say water (and thus, say, milk) and other substances.

I have a small thermometer in my fridge that seems to go above 40 because I go in for some PB&J (and associated bread, of course) and a beverage here and there. I know I'm letting the cold out, but things are okay, so I assume the difference in heat capacitance makes things safe, and so that got me wondering about things. I wonder if it would make more sense to have a thermometer immersed in water and read that to know when things are off.

submitted by /u/ummaycoc
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