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Tuesday, September 5, 2017

I just looked at the sun with my eclipse glasses, and there are two black dots on the sun. What are those?

I just looked at the sun with my eclipse glasses, and there are two black dots on the sun. What are those?


I just looked at the sun with my eclipse glasses, and there are two black dots on the sun. What are those?

Posted: 04 Sep 2017 01:52 PM PDT

If you have your eclipse glasses, go look. Are they solar flares visible to the naked eye? Or are they planets?

submitted by /u/supaiderman
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Do animals know when a storm or hurricane is coming?

Posted: 04 Sep 2017 02:21 PM PDT

After going on vacation I was driving back to south Florida, about where the category 4 hurricane is supposed to hit and I realized that a whole lot of birds, a lot more than usual, we're moving north and since It's becoming colder everywhere I thought it should be the other way around where birds migrate south. Now with the hurricane looking like a very large threat, I figured that must be the reason for the birds fleeing.

Bonus question: if they can sense the hurricanes, why can't humans?

submitted by /u/jajsiehenso
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Why do hurricanes only hit eastern North America?

Posted: 04 Sep 2017 12:23 PM PDT

My question is mainly why eastern over western (California), but also I don't believe I've heard of hurricanes hitting anywhere else in the world either.

submitted by /u/SquanchyMelo
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What exactly is a laser composed of and what are the differences between different types of lasers?

Posted: 05 Sep 2017 02:29 AM PDT

I understand that lasers are light (focused?) and that's about it. Lasers fascinate me. You can buy a pointer at pretty much any corner shop and those are very fun to play with. What interests me more are those lasers that cause damage. The ones that cut through metal and can disintegrate fabric/paper. What is the difference between a basic laser pointer and a laser capable of cutting through six inches of metal like a knife through butter? Is it simply the intensity of the light? And if that's the case, through what means do we control the intensity? I apologise if this question seems overly basic but, generally speaking, I am not a man of science. Thank you in advance for your answers and I look forward to being educated further on the topic.

submitted by /u/ChosenNeravarrine
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What happens if a black hole is sucked in to another black hole?

Posted: 04 Sep 2017 11:19 PM PDT

What kind of impacts do nuclear tests have in general on nature?

Posted: 04 Sep 2017 01:52 PM PDT

What will happen to a piece of wood, placed in a "pot"with no oxygen and then placed over a fire?

Posted: 04 Sep 2017 03:18 PM PDT

also the same question but what if the "pot" was pressurised?

submitted by /u/Smoko854
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Why is there a Laser Gain Curve?

Posted: 04 Sep 2017 10:27 AM PDT

As we talk about a Laser and its active Medium, a figure like the one down below is often shown. I understood the basics of it but cannot think of a simple explanation why there is a gauss like gain curve above all passible frequency spikes.

I know one can say "the medium increases only those frequencies" but what principle is connected to this?

I also know that the curve does not always have to be gaussian but thats not the point of the question.

https://imgur.com/a/GwRNo

submitted by /u/Ic3Breaker
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Does the Pauli exclusion principle imply that there is a maximum possible density for any substance?

Posted: 04 Sep 2017 03:51 PM PDT

I.e. packed so tightly that it would be impossible to get any tighter without particles starting to occupy the same space? I know that under normal conditions, an atom is primarily made up of empty space between the nucleus and the electrons, so I'd imagine such a limit could only be reached in a black hole.

Are all black holes the same density? Or are black holes of a higher mass more dense? If some are more dense than others, do we have reason to believe that there is a limit to just how dense they can get?

submitted by /u/Lemonwizard
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What types of magnets are used in motors and generators?

Posted: 04 Sep 2017 08:54 PM PDT

For example, in wind turbines/electric cars. What are the advantages/disadvantages of different materials?

submitted by /u/JackA7X
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Do we have any idea what caused the Oh My God Particle to be moving so fast?

Posted: 04 Sep 2017 05:49 PM PDT

Chemistry: Molecule shape and electron geometries. Why isn't H2S linear?

Posted: 04 Sep 2017 02:02 PM PDT

I am a Chem 3 (organic chemistry) student so Im very familiar with chemistry. While studying I came across a simple question, "What is the molecular and electron geometries of H2S?" So I made the lewis diagram and realized that since Sulfur is in the same group as Oxygen and that I had drawn drawn a linear version of the water molecule. Then i thought, well what is different from Oxygen and Sulfer. Then i found that Sulfer actually has an electronegativity (e-neg) of 2.5 while oxygen has and e-neg of 3.5. after-which i realized that the difference between hydrogen and sulfur is 0.4 (marginally non-polar). And since linear is a non-polar structure i figured that "hey this must be why H2O is bent! it has a polar molecule from the difference in e-neg! this must be why the bent molecule forms!"-but I was wrong, the molecule is bent.

My question is why? No one else that ive seen has made a clear explanation as to why "the lone pairs push the bonding pairs away." in my mind, its just 4 electron pairs, and two of them just happen to have a proton attached to them. why does this molecule form a bent instead of a linear?!

If the answer is a theory or a scientific paper, please link it in your answers please!

submitted by /u/EpicPwn_343
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Has the discovery of a very large particular number ever refuted a widely believed conjecture in mathematics?

Posted: 04 Sep 2017 06:55 PM PDT

For example:

Goldbach's conjecture states that every even integer greater than two is the sum of two primes. Computer calculations have verified that this holds true for integers less than 4 x 1018 , but nevertheless a full proof has never been discovered.

Now, if we were to discover a single even integer greater than 4 x 1018 Goldbach's conjecture would be false. In the history of mathematics has something like this ever happened? Has a widely believed conjecture been rendered false due solely to the discovery a single large number that refutes it?

submitted by /u/only_bad_days
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Why Tsar Bomba - the most powerful bomb ever detonated - could have destroyed the Earth according to its creators?

Posted: 04 Sep 2017 11:27 AM PDT

According to the Russian physicists who created the bomb, the explosion could have started a self-sustaining nuclear reaction in the ocean, leading to the planet's destruction. How is that possible?

submitted by /u/EchoOne11
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How can we tell what path a hurricane will take days in advanced? How come we can't determine high probability paths for the hurricane further in advance?

Posted: 04 Sep 2017 02:05 PM PDT

I'm a dumb kid.

submitted by /u/The_Thrill17
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In a flood situation, what walls are holding up the water?

Posted: 04 Sep 2017 06:56 PM PDT

Are gas giants (up to 12 Jupiter masses) more likely around hot stars (O-A class) or cold stars (K, M, Brown Dwarf)?

Posted: 04 Sep 2017 10:03 AM PDT

I can't find reliable data on planetary likelihood per stellar class.

submitted by /u/MrJadexxxxxxx
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Why does clipping a sine wave create a square wave?

Posted: 04 Sep 2017 12:57 PM PDT

I understand why an infinite series of odd harmonics at proportional amplitudes and frequencies creates a square wave, and I understand the additive properties of waves.

I also understand why overdriving a sine wave through an amplifier/circuit cuts off the top and bottom of the wave, giving it a "square" appearance.

I guess I don't understand the reasoning the other way around. How and why does the fairly simple operation of clipping turn one sine wave into an infinite series of sine waves?

It may seem like I'm asking a question I've already answered, but that's not my intention, or maybe I'm not getting something.

Let's say you didn't offhand know the harmonics of a square wave. How could you derive them from the shape of a square wave?

Odd harmonics generate square/triangle waves. Why do square/triangle waves generate odd harmonics?

Does that make sense, or is the answer just, "dumb dumb, what about the transitive property don't you understand?"

submitted by /u/diamondbackmanhunter
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Monday, September 4, 2017

Is a single Elephant's skin cell bigger than a human's skin cell?

Is a single Elephant's skin cell bigger than a human's skin cell?


Is a single Elephant's skin cell bigger than a human's skin cell?

Posted: 03 Sep 2017 01:15 PM PDT

People built a "Z machine" on Earth that creates a temperature of 2 Billion Kelvin. How can this temperature be generated and why does this temperature not melt the entire facility that creates it?

Posted: 04 Sep 2017 02:37 AM PDT

For scale, this is approximately 100x hotter than the center of the sun.

Given that the sun only has an outside temperature of 5,500K and easily heats up Earth to 300K+ over a distance of 150 million kilometers, shouldn't a temperature of 2,000,000,000K on Earth itself cause severe damage of some kind?

submitted by /u/Linnun
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How soon after an organism 'dies' are all of its cells dead? its bacteria?

Posted: 03 Sep 2017 10:12 PM PDT

Let's say an organism dies instantaneously (no previous oxygen deprivation). How long would the cells continue to be alive despite the macro organism being considered dead? How long would the bacteria within and on the body last? How much of a time difference would it be, if any, between say an ant and a blue whale?

submitted by /u/zincinzincout
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What are the repercussions of detonating a nuclear bomb underground?

Posted: 03 Sep 2017 10:56 PM PDT

When the immune system damages the gut of a coeliac person who eats gluten, does the mechanism of action differ significantly from that of an allergy (igE+histamine+basophils)?

Posted: 04 Sep 2017 05:18 AM PDT

Coeliac's is often described as an "allergy", but people who've been educated in the field say it's "technically not an allergy and technically not autoimmune, though very similar to both". I'd like to better understand what this means.

Bonus question: Do allergies have something similar to "levels" like coeliac's? Or is it more like you're either allergic or non-allergic?

submitted by /u/katinla
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How does one measure the thickness of gold foil?

Posted: 04 Sep 2017 06:03 AM PDT

What, other than the tides, is noticeably affected by the moon's gravity?

Posted: 03 Sep 2017 01:46 PM PDT

Why does the deficiency of some vitamins like b12 can cause depression?

Posted: 03 Sep 2017 07:48 AM PDT

Cats can shake their head at a surprisingly rapid rate. How do they avoid whiplash and concussions while doing this?

Posted: 03 Sep 2017 04:20 PM PDT

What is the mechanism by which nuclear reactors produce energy?

Posted: 03 Sep 2017 09:24 PM PDT

To be more specific, I'm interested in what happens with the nuclear fuel and how the energetic reaction is sustained. I know that it uses fission (commonly U-235) to release the energy, as well as the basic idea of neutron moderation, and I'm aware of but not fully versed on the idea of fast and slow neutrons.

My questions include: * Is the reaction a self-sustaining chain reaction? That is, could it be considered at the precipice of criticality? * Followup, if It is NOT, then how is the reaction maintained? How do they provide enough neutrons for a sustained and fairly constant energy production? * How exactly are the decay products handled? How quickly do they accumulate? And what do they do to the energy output? (Also, if possible, the common and notable decay products would be awesome!) * How does "neutron moderation" occur, and what is the point of it? My picture of the reaction is of solid fissile fuel (i.e. like those diagrams you see explanation fission). Where does the moderator interact with the fuel?

I hope these questions make sense! My understanding of physics is analogous to that of a hobbyist astronomer, so explaining it at that level is ideal. However, I'm fairly content with getting into more mathematical sides of things if necessary. That said, these questions are more of the engineering side (which is the category where I'm placing it), so I'm hoping it will have more conceptual answers.

submitted by /u/Aethi
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How exactly can elements be changed into other elements by radiation?

Posted: 03 Sep 2017 03:17 PM PDT

If I remember correctly, the radiation of electrons can disturb and add/take away electrons from another element to change the element itself. If I were to do this to a big block of gold, could I possibly change this into a block of silver or even into a gas like oxygen?

submitted by /u/Bradleyharris88
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Could a neutron detector be used to verify underground nuclear tests?

Posted: 03 Sep 2017 11:53 AM PDT

If the symptoms of an illness are typically the body creating a hostile environment to get rid of the infection (runny nose, fever, etc.), what do viruses/bacteria actually do?

Posted: 03 Sep 2017 08:29 AM PDT

Or, what would an illness look like if our immune system didn't do all of those things to destroy the viruses/bacteria?

submitted by /u/mozrik
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How much of the fissionable materials (Uranium, Thorium) are in the Earth's core and how often does it combine into critical mass to explode?

Posted: 03 Sep 2017 10:25 AM PDT

How can waxing and waining gibbous phases of the moon look like they do?

Posted: 03 Sep 2017 03:22 PM PDT

The shadow the earth throws on the moon in those phases looks like the earth is a crescent instead of a sphere. I can't wrap my head around it. Can someone please explain.

pic of lunar phases

submitted by /u/I_want_fun
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Do trees effect the wind speed/potential wind damage of a hurricane?

Posted: 03 Sep 2017 03:35 PM PDT

With Hurricane Irma looming, I was wondering if living in a rural area with dense tree and brush coverage has any effect on the wind speed of the storm at ground level, and by extension could that reduced wind speed lessen the potential damage caused by the wind to homes in that area? Edit: of course, trees can fall and branches become projectiles, I'm more curious about wind damage only from a powerful major hurricane.

submitted by /u/DobbyDooDoo
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What is it exactly that energy boosting substances like caffeine and ginseng do to our body in order to provide an alert/energized state?

Posted: 03 Sep 2017 09:05 AM PDT

How is queen bee becoming a queen bee ? Is it natural or is it acquired ?

Posted: 03 Sep 2017 02:08 PM PDT

From the Light Side of the Moon, are there phases of the Earth?

Posted: 03 Sep 2017 06:28 PM PDT

What happens to the inside of planets as they age?

Posted: 03 Sep 2017 07:03 AM PDT

I was thinking about the Earth's core today and how they should, due to entropy, cool over time. However it will still be under enormous pressure. What happens to different planet's cores over time? Do they completely solidify? Similarly what will happen to gas giants as they age?

submitted by /u/SailingOnFishlessSea
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With regards to the Diving Reflex, can we hold our breath longer while underwater than we can on land?

Posted: 03 Sep 2017 07:48 AM PDT

Does Hurricane Harvey affect the weather for the rest of the United States? If so, how, and how far?

Posted: 03 Sep 2017 07:56 AM PDT

Sunday, September 3, 2017

Why do clothes feel crunchy when you air dry them, but soft out of the dryer?

Why do clothes feel crunchy when you air dry them, but soft out of the dryer?


Why do clothes feel crunchy when you air dry them, but soft out of the dryer?

Posted: 02 Sep 2017 04:57 PM PDT

Do animals like music? Or at the least, can they recognise the patterns, melodies etc. and react to them?

Posted: 02 Sep 2017 03:03 PM PDT

Why do some people outgrow allergies and some people develop them later in life? And why do some people never outgrow them?

Posted: 02 Sep 2017 05:11 PM PDT

Is there any way to determine the likelihood of whether someone will or won't outgrow their allergies? I feel like I can never find a solid answer to any of these questions.

submitted by /u/Lowfatmilksubstitute
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Did the construction of the Panama and Suez canals affect the ecology of the surrounding waters?

Posted: 02 Sep 2017 03:44 PM PDT

Despite the small overland distance, would connecting two very different bodies of water have a noticeable effect on the flora and fauna of the two regions?

submitted by /u/SpooningThemSoftly
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In light of recent events in North Korea, how do you set off a nuclear bomb underground without causing substantial damage above the blast site?

Posted: 03 Sep 2017 12:06 AM PDT

Reports saying that this was a hydrogen bomb and 10 times more powerful than anything ever previously tested and 5 times more powerful than the Nagasaki bomb which killed 70000 people almost instantly. How is there not like, y'know, a massive crater in the ground where it was or something?

submitted by /u/Farquad4000
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During a supernova, what amount of the star's matter is converted into energy?

Posted: 02 Sep 2017 10:56 PM PDT

It looks like during the lifetime of the sun, .034% of it's mass will be converted into energy via E=MC2. But what about a supernova? Perhaps we can use an A1 type as an example.

submitted by /u/Djerrid
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Can a star have more than one fusion core?

Posted: 02 Sep 2017 04:40 PM PDT

Other than supernova, could for example a blue supergiant/hypergiant have hotspots not in the center that cause fusion?

submitted by /u/UntamedOne
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How are parrots able to repeat and talk?

Posted: 02 Sep 2017 08:20 PM PDT

How are parrots able to memorize and repeat certain noises and words so well?

submitted by /u/stargazer547
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How does the Rfly drone based RFID system developed at MIT work?

Posted: 03 Sep 2017 05:57 AM PDT

The text in the article says:

The drones don't actually carry the RFID reader with them — Adib explains that this added weight basically caused the drone to crash — but rather, relays the signals emitted by the reader over larger distances. "You can take a single reader, whose range is limited to a few centimeters, and send the signal over exponentially larger distances."

So does this mean that the drones are just repeater/amplifiers? Does the reader have that much more bulk? What if two drones transmit the same reader signal and send back the RFID codes at the same time, are there multiple readers waiting for the signal? Do different drones operate on different frequencies?

submitted by /u/snarejunkie
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Is the Planck length constant or does it change as the universe expands?

Posted: 02 Sep 2017 02:31 PM PDT

Also, is space time pixelated by this length, or could you have overlapping of said pixels or lengths, where space-time is actually continuous?

Edit: The title should read "....could it possibly change..." as it might be theoretical.

submitted by /u/jstaylor01
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Does a satellite experience centrifugal force or centripetal force?

Posted: 02 Sep 2017 06:17 PM PDT

Does the quantity or quality of melanin in our skin change as we age?

Posted: 02 Sep 2017 05:17 PM PDT

Is there radiation associated with the creation of a charged particle?

Posted: 02 Sep 2017 06:20 PM PDT

I was studying for E&M and I noticed that radiation fields seem to be accompanied by a changing current somewhere. I then tried to figure out how to get radiation without a current this is the best I got. I know the question is kind of nonphysical since you can't just create a lone electron for example but supposing you could, does that release radiation? I'm assuming there's some delta function like object but I'm not sure.

I recognize that this is kind of a silly question but I wanted to procrastinate and nobody else is in the office with me.

submitted by /u/MarsOfDickstruction
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How does speakers make multiple frequency at once?

Posted: 02 Sep 2017 05:01 PM PDT

So I understand that a speaker oscillates to a specific frequency but how is possible for it to make a mixtures of highs and lows at once

submitted by /u/princehermit
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Why is a kettle so much more efficient than a saucepan at boiling water?

Posted: 02 Sep 2017 10:59 AM PDT

Can someone explain the comparative strength of household magnets?

Posted: 02 Sep 2017 06:18 PM PDT

I'm interested in making household (i.e., refrigerator) magnets as a craft project by gluing some gewgaw to a plain, ordinary magnet. The plasticky "magnet tape" is notoriously weak, and the hard black ones are too big, so I ended up with some neodymium magnets from the hardware store. After some reading, I am worried that these are too strong and may be difficult to remove from a refrigerator without tearing off the gewgaw. Internet research is just getting me a lot of industrial supply company FAQs and Wikipedia articles with tesla measurements. I don't even know what a tesla is a function of: mass of the magnet? area of the pole? something more esoteric? I would appreciate a quick-n-dirty guide comparing household magnet types in some sort of strength-for-size way. Thank you!

submitted by /u/SciviasKnows
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What determines the boiling and freezing points of a substance?

Posted: 02 Sep 2017 03:51 PM PDT

Is there a difference in sound quality when I use the volume control wheel (a variable resistor, I assume) on my headphones as opposed to changing the volume through software?

Posted: 02 Sep 2017 11:19 AM PDT

I understand that it would not necessarily be a noticeable difference; however, is one method of volume control superior in any way? Is it better leave the software volume at its maximum and lower the headphone control as needed, or vice-versa?

submitted by /u/Thundershock97
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Need help Understanding JFET's, Specifically how the depletion region is controlled and its relationship to drain current?

Posted: 02 Sep 2017 01:58 PM PDT

So we just started studying FET's in my Electronics circuits and device theory class, I have a basic understanding of how N-channel JFET's work.

I am having trouble wrapping my head around how the depletion region is affected by VDS/Drain current when VGS is set to 0V. I think the larger the drain current(ID) becomes the more free electrons are "pulled"(not sure if correct term) from the N-type making the depletion region have more positive ions. I am trying to understand what is physically happening in the depletion region when VGS=0 and ID increases.

I also want to understand the other side, Where ID is a function of VGS, How does applying a larger negative voltage make the depletion region larger and how does that effect the resistance of the N-channel.

What is the difference between the depletion region when VGS=0 and ID is at saturation compared with VGS= Some negative value and ID = some lower saturation current. What physically happens to the charges in the depletion region?

I can clarify if what I'm asking is unclear.

submitted by /u/eoin34
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Why do some things burn and some things melt?

Posted: 02 Sep 2017 11:05 AM PDT