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Friday, June 23, 2017

The recent fire in London was traced to an electrical fault in a fridge freezer. How can you trace with such accuracy what was the single appliance that caused it?

The recent fire in London was traced to an electrical fault in a fridge freezer. How can you trace with such accuracy what was the single appliance that caused it?


The recent fire in London was traced to an electrical fault in a fridge freezer. How can you trace with such accuracy what was the single appliance that caused it?

Posted: 23 Jun 2017 05:16 AM PDT

In Earth travel, we use North, South, East, and West, plus altitude for three-dimensional travel. Since those are all relative to the Earth, what do they use for space travel?

Posted: 22 Jun 2017 06:56 AM PDT

Why are humans so diverse and unique in appearance to the point where none of us look the same compared to other animal species where all individuals look the same?

Posted: 23 Jun 2017 06:35 AM PDT

People can vary so much in looks regarding eye/hair/skin colour, height, bone structure, build, to the point where everyone who has ever existed has a unique "look". Some animals are like that too to a certain degree, like cats and dogs.

For many other species of animals though all the individuals in a population look the same, like idk elephants, crows, sharks...how come they have little or no diversity in appearance?

submitted by /u/Krahz
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What do blind people see when they dream? Assuming they were blind from birth.

Posted: 23 Jun 2017 06:28 AM PDT

Is the calculation of the atoms in the observable universe being 10 to the eightieth power accurate?

Posted: 23 Jun 2017 01:40 AM PDT

Why do astronomers think a collision caused Uranus' extreme tilt yet it's moons are also tilted?

Posted: 22 Jun 2017 04:05 PM PDT

Tilted, as in spinning in the same axis relative to our Sun. Yet it's moons have the same axis as Uranus, so collisions did all that? Sounds unlikely.

submitted by /u/Sciex
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Can the spontaneous fission of Uranium 238 emit neutrons capable to fission Uranium 235 in the same solid matrix?

Posted: 23 Jun 2017 06:37 AM PDT

Is it possible for a planet to have at least two moons orbiting it in opposite directions? If yes, what would be the effects if it somehow happened to Earth?

Posted: 22 Jun 2017 11:59 PM PDT

At what point in time do we stop seeing wolf fossils near humans and start seeing "dog" fossils associated with humans?

Posted: 23 Jun 2017 07:32 AM PDT

Did dogs also go through intermediaries to transition between wolf and dog? Ie, we have H. erectus before H. sapien. Or are modern dog and modern wolves too similar ro be classified differently?

submitted by /u/Mizz_Wright
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How do cars with adaptive cruise controls deal with the 'noise' of other vehicles on the same road potentially using similar or identical radar or lidar based systems?

Posted: 22 Jun 2017 06:59 PM PDT

I was thinking of a scenario where two vehicles in adjacent lanes (which could potentially be of the exact same make) are both using adaptive cruise control to maintain a fixed distance from the vehicle in front. There must be systems that allow each vehicle to differentiate the radar reflections of the proceeding vehicle in their lane and not be confused by the adjacent vehicle. I'm curious as to what those systems are specifically.

submitted by /u/a_lowman
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How do scientists determine which two elements to use when synthesizing new elements?

Posted: 22 Jun 2017 09:52 PM PDT

For example, Oganesson was synthesized using Californium and Calcium (98+20=118). However, another lab using Krypton and Lead (36+82=118) tried and failed to produce Ognesson. My question is, why were those specific elements chosen? I know their atomic numbers have to add to 118, but why not use Iron and Uranium? (92+26=118) Two Praseodymiums? (59+59=118) And why did Krypton and Lead fail, even though their numbers add up? Thanks in advance.

submitted by /u/DoomCrystal
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Will copper hot pipes or an iron boiler rust first?

Posted: 23 Jun 2017 02:44 AM PDT

How do fast-acting anti-anxiety pills like Xanax work compared to drugs like buspirone, which work to change your neurochemistry more permanently over time?

Posted: 22 Jun 2017 07:26 PM PDT

I'm mostly looking for the neurochemistry aspects of it. Like, why do some drugs only perform for a short amount of time while others you have to take continually and they gradually suppress symptoms?

submitted by /u/frottingotter
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How does the primary coil impedance change due to the eddy current?

Posted: 23 Jun 2017 03:50 AM PDT

This question is based on one of the common methods of Non-Destructive Testing ( NDT ), called Eddy Current Testing.

In this method, they use a primary coil with an AC voltage supply to it. This AC current produces a changing magnetic field in the primary coil ( Call it excitation field ). When the primary coil is brought near the component to be tested, the changing excitation field induces circular eddy currents in the surface of the component. This eddy current in turn produces a magnetic field in such a way as to oppose the changing excitation flux. The reduction in the resultant field strength will change the coil impedance. But how? Isn't the primary coil impedance only dependent on R ( resistance ), L ( inductance ) and w ( angular frequency of the AC voltage source ) ?

submitted by /u/Jactly
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What does wind look like on an atomic level?

Posted: 22 Jun 2017 02:24 PM PDT

What makes AC current better suited than DC current for certain applications, and vice-versa?

Posted: 22 Jun 2017 01:28 PM PDT

I work as an electrical assembler and have been wondering this for a while now. Why is it that high-power applications like servos and VFDs seem to be exclusively 240V+ AC, while small things like sensors seem to be exclusively 24V DC?

submitted by /u/twodeepfouryou
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Are there events that are in the future in every frame of reference?

Posted: 23 Jun 2017 03:04 AM PDT

The relativity of simultaneity shows that there's no "present": there's a causal past, a causal future, here-now, and "elsewhere", as this animation handily depicts. It depicts that the faster a frame of reference moves relative to another, things that are in the causal future become the present (or past) of things in another frame's here-now.

This obviously leads to the worrying conclusion that everything in the future has already happened in another frame of reference. Is that so? Is this true mathematically, in general relativity? Is this true observationally, that there are objects moving at such high speeds relative to another object, that one object's entire causal future is "visible" from another object's here-now? I assume events that are farther in the future than the diameter of the universe cannot be observed from within the universe, but is that so? Is there any group of events that is in the future in every frame of reference?

What are some "canonical" books/papers that deal with the subject on a physics undergrad-postgrad level?

edit

  • Event C is arbitrarily far in the causal future of event A in frame of reference O (this order of events is absolute and is the same in all frames of reference)
  • Event B is simultaneous with event A in frame of reference P (this order of events is relative)
  • Is there, for any group of events A, B, and C, a frame of reference where B and C are simultaneous?

If so, then any event in the future could be said to have already happened. If not, what is the group of events that are not simultaneous with B in any frame of reference?

submitted by /u/12mo
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Why are Birds sub-grouped under Reptiles and not in their own unique standalone class like Amphibians?

Posted: 22 Jun 2017 05:13 PM PDT

Why did some social mammals evolve into patriarchal groups and others into matriarchal groups?

Posted: 22 Jun 2017 09:04 AM PDT

Specifically looking for an answer outside of the context of human culture. For example, elephants, meerkats, lions, and killer whales all live in matriarchies - why did they evolve this way while many other mammals evolved in patriarchies?

submitted by /u/marsupial23
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Thursday, June 22, 2017

Why does sunburnt skin remain hot to the touch even days after the burn has occurred?

Why does sunburnt skin remain hot to the touch even days after the burn has occurred?


Why does sunburnt skin remain hot to the touch even days after the burn has occurred?

Posted: 21 Jun 2017 04:13 PM PDT

When we drain oil from wells. Does it make a empty pocket?

Posted: 21 Jun 2017 07:02 PM PDT

How do spiders choose a location for their web?

Posted: 21 Jun 2017 07:09 PM PDT

So this is a multi-part question, I suppose. First time posting here and asking you guys about something.

  1. Whenever it is that spiders are grown and ready to set up shop, spin a web and wait for dinner (the species that do hunt this way), how does it choose the location? How does it know where the ideal place is to collect food?

  2. How far do they travel to seek out such a place, if they do "seek" out certain places. Do they just drop a web whenever and wherever they are hungry? Move on when they get bored to a new place?

  3. Going through some things in the bottom of the closet, stuff that gets moved on occasion, a couple times a month maybe. Inside a shoebox (and similar places) there are usually some tiny, tiny spiders with their homes set up. Is there really a steady food supply in there, tucked away, door shut? Obviously I know there is tiny food for them galore, but really, in my closet?

submitted by /u/supersayanssj3
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[Physics] How does gravity work on a torus world?

Posted: 22 Jun 2017 04:27 AM PDT

Hey so I've been thinking about this for a while and would like a definitive answer.

If I lived on a torus planet where the cross-section of the torus was the diameter of the earth and the hole in the middle of the torus was around the distance from the earth to the moon. Assuming the torus is not rotating so no artificial gravity. Where would gravity pull me towards? My slightly educated guess would be the center of mass of the torus.

If this is the case then my follow up question would be, if gravity is weaker over distance, could I increase the size of this torus to the point where I would no longer be pulled to the centre?

submitted by /u/HymirTheDarkOne
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If the ocean level was high enough, there would be zero coastline. If the ocean dried up completely, there would also be zero coastline. At what approximate ocean depth would there be maximum possible coastline?

Posted: 21 Jun 2017 08:40 PM PDT

Why do UV stamps and UV paint show up under blacklight, but not under sunlight?

Posted: 22 Jun 2017 07:06 AM PDT

If the sun emits UV light, why can a blacklight with a UV bulb illuminate things that the sun can't? Is it just a question of strength or concentration of light waves?

submitted by /u/danceswithlesbians
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Why is the imaginary number defined as i^2 = -1, rather than i = sqrt(-1)?

Posted: 22 Jun 2017 04:47 AM PDT

In case of i2 = -1, there are two possible outcomes for i. So why wouldn't you just define i?

submitted by /u/JustReadingAndVoting
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What is this red line on the left side of the Sun?

Posted: 22 Jun 2017 07:09 AM PDT

Does having AIDS reduce allergy symptoms?

Posted: 21 Jun 2017 12:08 PM PDT

I know that allergies are caused by your immune system targeting harmless molecules. I also know that AIDS destroys your immune system. Would having AIDS prevent your immune system from attacking harmless molecules?

submitted by /u/lukego7
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If an ant was the same size as a tiger, would still be able to lift 20 times its own weight?

Posted: 21 Jun 2017 07:53 PM PDT

So if glass is made from sand, and sand is made from rocks, then how come we can see through glass but not rocks/sand?

Posted: 22 Jun 2017 04:15 AM PDT

Why don't wireless phone chargers mess up the rest of the phone's circuitry?

Posted: 21 Jun 2017 06:31 PM PDT

I understand Gauss's law and the inductive charging process but I don't get why that doesn't make the rest of the phone go berserk.

submitted by /u/shaneahc
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Why aren't man made satellites and the ISS destroyed by the Roche limit?

Posted: 22 Jun 2017 01:47 AM PDT

What is the viability of personal spacecraft?

Posted: 22 Jun 2017 12:56 AM PDT

And what things would such a craft need to account for short trips in space, say to the moon?

submitted by /u/Iconoclast_DotA
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Do other planets experience earthquakes too? If so, how do we know and how different are their magnitudes relative to Earth's?

Posted: 21 Jun 2017 11:01 PM PDT

If they don't have earthquakes, then why not?

submitted by /u/BenjiBubbles
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How does a down quark turn into an up quark in neutron decay?

Posted: 21 Jun 2017 11:53 PM PDT

I had thought that an electron was a quark-antiquark pair, but apparently this isn't so. So neutron decay starts with a neutron (udd), and in the end, there's a proton (uud) and two leptons. Are up and down quarks, then, not fundamentally different things? Are 'upness' and 'downness' just different quantum states of something quarky?

submitted by /u/SurprisedPotato
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Why does the multiverse theory have an infinite number of universes?

Posted: 21 Jun 2017 12:27 PM PDT

Every time I see the multiverse theory mentioned on TV, movies, books, comics, etc. they have the same basic concept of infinite universes, some very like ours, some very different.

While the idea that there are different universes with different laws of physics sits fine with me, the concept of there being one universe exactly like mine but I'm made of corn, in another the only difference is I have a different colour shirt on, etc. seems ridiculous.

Why does the theory have 'infinite' rather than many universes?

submitted by /u/PermanentSubstitute
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In what cases it would be more meaningful to take the harmonic average or the geometric average instead of the arithmetic average?

Posted: 21 Jun 2017 03:43 PM PDT

If I woke up 3000 years ago, would it be realistically possible to create electricity in a usable form?

Posted: 21 Jun 2017 12:18 PM PDT

I frequently have dreams where I wake up in the past and am completely useless, and so I'm wondering if it would actually be possible to create modern technology without any support structure in place.

I know the basics for creating electricity: A magnet, some conductive wire, and something for the electricity to work on, but would it be possible to create a powerful enough magnet from scratch? How would I go about making copper wire before copper wire is a thing?

Could I create my own light bulb?

submitted by /u/RadBadTad
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Why does cold water feel, or seem to feel, so much colder than cold air? Why does 50°F water seem so much colder than 50°F air?

Posted: 21 Jun 2017 12:29 PM PDT

I can walk outside in a pair of shorts and a t-shirt when its 50°F outside just fine, but when I get in 50°F water, I feel like I'm going to die.

Thanks gang.

submitted by /u/Norskee0
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Wednesday, June 21, 2017

If all the polar ice caps melted, would the ocean become less salty?

If all the polar ice caps melted, would the ocean become less salty?


If all the polar ice caps melted, would the ocean become less salty?

Posted: 21 Jun 2017 02:54 AM PDT

Is there a tidal effect on our atmosphere?

Posted: 21 Jun 2017 12:50 AM PDT

So I understand that the sun and moon's gravity creates a tidal effect on the oceans of our planets, but do they cause a similar effect on our atmosphere? Or is it not dense enough?

submitted by /u/lli32
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Do animals with high body fat, like seals or bears, suffer higher rates of heart disease than other animals?

Posted: 21 Jun 2017 05:34 AM PDT

Are all spiderwebs chemically identical?

Posted: 21 Jun 2017 06:25 AM PDT

Do spiders of different species create different chemicals to use in their webs?

submitted by /u/NotSuspicious_
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If there's no blood supply to cartilage, how come glucosamine or chondroitin is "good for joints"? How do minerals/vitamins/hormones even get to cartilage cells without blood flow?

Posted: 20 Jun 2017 08:33 PM PDT

How do astronomers determine the radius of the moon?

Posted: 21 Jun 2017 05:55 AM PDT

Do Prime numbers change with base?

Posted: 21 Jun 2017 05:13 AM PDT

E.G., we use Base-10, but would there be different prime numbres in base 12? 20? 99?

submitted by /u/CMDR-FusionCor3
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Is the density of the materials that makes up Neutron stars and White dwarves a result of the properties of the material, or the gravitational feilds in which the materials reside?

Posted: 21 Jun 2017 06:35 AM PDT

Also, what would happen if said material was placed in a low gravity situation, such as on earth?

submitted by /u/Redeye1999
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How can the same protein isoform (PrPSc) cause so many different diseases?

Posted: 21 Jun 2017 06:35 AM PDT

Everywhere I read about prionic diseases, it always talk about the PrPSc protein, making a distinction between it and its isoform PrPC.

But I imagine that not all PrPSc are the same, since they exhibit some differences in terms of symptoms, incubation period... But I can't seem to find what exactly is the difference between the prions that cause each disease.

submitted by /u/TridentBoy
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How do they build highways in loose sand?

Posted: 21 Jun 2017 04:20 AM PDT

My question is basically only what is in the title, I am trying to find out how paved roads in the desert are made. Normally, constructors lay down a subbase on the subgrade (which in this case is sand) then a base course over that and then the pavement. The subgrade is supposed to hold the whole weight of the road, how do they solve this in the desert?

submitted by /u/Jacareadam
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How is the amount of semen expelled during ejaculation determined by our bodies?

Posted: 21 Jun 2017 07:16 AM PDT

This might be an idiotic question, but do things really fall at the same rate?

Posted: 21 Jun 2017 01:02 AM PDT

If F=G(M1*M2/d2) then objects don't actually fall at the same rate, right?

It's just that any experimental observation we've done on Earth shows that they do because M2 being the mass of Earth is so large that comparing different M1s is kind of irrelevant?

submitted by /u/dcrico20
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How hot is a nuclear meltdown? Are there materials like tungsten which could stay solid indefinitely?

Posted: 20 Jun 2017 04:47 PM PDT

Assuming that pressure isn't an issue would a large tungsten(or similar) vessel be able to contain a meltdown, or is a nuclear meltdown hot enough to melt pretty much anything?

submitted by /u/pi_rocks
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What causes phone's GPS to drift?

Posted: 21 Jun 2017 04:52 AM PDT

I currently have an iPhone 6, but this question is probably general for all modern phones.

What causes GPS drift (phone thinks it is somewhere and then somewhere else meters away, then somewhere else) and how can it be created by placing the phone in a specific location (like a box made out of something that doesn't disable the signal, only weakens it).

More info: Mainly asking for Pokemon Go, but interested in GPS technology too.

submitted by /u/webs2slow4me
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How do different aged organs effect receipients of organ transplants?

Posted: 20 Jun 2017 09:51 AM PDT

For instance, if a 20 year old patient received a kidney from a 60 year old donor, by the time the patient was 60, that would be a 100 year old kidney! Is there reason to think that the kidney would "stop" working at a certain age, regardless of the patient's age?

Or, in reverse, if for example, a 75 year old received a kidney from a 20 year old, would their body be shocked at how relatively healthy this one particular organ was? Even if the rest of their body was relatively healthy, the body would have slowed down compared to a 20 year old!

Do hospitals try to match organs by age in addition to blood type, etc?

submitted by /u/bandroid887
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How does light get pulled back into a black hole?

Posted: 21 Jun 2017 07:07 AM PDT

Say I was standing inside account black holes event horizon holding a laser pointer. If I turned it on and pointed out outwards perpendicular to the event horizon, how does the light get pulled back into the black hole?

The photons coming out of the laser would need to accelerate towards the black hole which means that their velocity would decrease to less than c. My understanding is that light always travels at c in a vacuum, so how is it possible for the photons' velocities to decrease?

I think I might be confusing how photons behave with how ordinary matter behaves, but I'm not an expert..

submitted by /u/StupidQuestionsAcnt
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How does your body know when to stop adding more blood after you donate or lose blood in an accident?

Posted: 21 Jun 2017 06:46 AM PDT

Will you burn more energy trying to keep yourself warm (in a cold environment) or try to cool yourself down (in a hot environment)?

Posted: 20 Jun 2017 11:05 PM PDT

Would it ever be possible for humans to have gold-colored eyes (like cats, owls, wolves, bald eagles, etc.)?

Posted: 20 Jun 2017 05:06 PM PDT

I am wondering if it would ever be possible, through a genetic-engineering perspective, for humans to have the gold-colored eyes that other animals have. Let's say you have a futuristic culture in which designer babies are the norm, and diseases have been all-but-eradicated in this better "breed" of human which has resulted through generations of careful genetic selection. If these futuristic peoples have the ability to pick and choose certain phenotypes for their children, isn't there some way for a gold eye color to come about (as it would be an alluring and desirable trait)? Can we not simply "inject" the pigments from other animals exhibiting golden eyes into human eyes, or splice the genes from these animals into human DNA to allow for this to be a new genotype able to be passed on from parent-to-parent?

Please help... I've done tons of research but can't seem to find the answer anywhere. I need to know if this is possible for a novel I am writing.

submitted by /u/ShowMeTheNugget
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What would it look like inside a star?

Posted: 21 Jun 2017 02:46 AM PDT

So, incredible heat and pressure and magnetic forces from the fusion, but how much fusion actually goes on at a time? Stars last billions of years, so all their material clearly doesn't undergo fusion at once.

We know what a fusion explosion looks like on earth, but what does it look like in a star? How long does it expand before it runs into other fusion explosions? How many fusion explosions are there in any given, say, square kilometer of space per minute? 1? 1 million?

submitted by /u/naciketass
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Why is a halogen more electronegative than it's halide?

Posted: 21 Jun 2017 02:28 AM PDT

I tried asking my chemistry teacher why Cl2 was more electronegative than Cl- but wasnt able to understand her explanation. Help would be appreciated!

submitted by /u/ow2n
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Since children are growing and constantly have dividing cells, why do they have lower cancer rates than adults (who are not growing)?

Posted: 20 Jun 2017 02:57 PM PDT

Are cursive characters unique to modern times, or were there forms of cursive used by earlier civilizations?

Posted: 21 Jun 2017 01:53 AM PDT