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Tuesday, June 6, 2017

How common is general anesthesia in dental practice?

How common is general anesthesia in dental practice?


How common is general anesthesia in dental practice?

Posted: 06 Jun 2017 01:07 AM PDT

Regional anesthesia is used the most in my area despite the difficulty of the dental procedure (pulling wisdom teeth for example). General anesthesia is the last option and barely suggested.
So how common is general anesthesia in dental practice in other countries?

submitted by /u/zulzulfie
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Are there video algorithms to significantly enhance detail from low quality RAW video source material?

Posted: 06 Jun 2017 04:20 AM PDT

Everybody knows the stupid TV trope, where an investigator tells his hacker friend "ENHANCE!", and seconds later the reflection of a face is seen in the eyeball of a person recorded at 640x320. And we all know that digital video does not work like that.

But let's say the source material is an analog film reel, or a feed from a cheap security camera that happened to write uncompressed RAW images to disk at 30fps.

This makes the problem not much different from how the human eye works. The retina is actually pretty low-res, but because of ultra fast eye movements (saccades) and oversampling in the brain, our field of vision has remarkable resolution.

Is there an algorithm that treats RAW source material as "highest compression possible", and can display it "decompressed" - in much greater detail?

Because while each frame is noisy and grainy, the data visible in each frame is also recorded in many, many consecutive images after the first. Can those subsequent images be used to carry out some type of oversampling in order to reduce noise and gain pixel resolution digitally? Are there algorithms that automatically correct for perspective changes in panning shots? Are there algorithms that can take moving objects into account - like the face of a person walking through the frame, that repeatedly looks straight into the camera and then looks away again?

I know how compression works in codecs like MPEG4, and I know what I'm asking is more complicated (time scales longer than a few frames require a complete 3D model of the scene) - but in theory, the information available in the low quality RAW footage and high quality MPEG4 footage is not so different, right?

So what are those algorithms called? What field studies things like that?

submitted by /u/pbmonster
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For people in areas with no access to clean water, do they live with constant parasite/bacterial infestations or do their immune systems become adept at clearing them?

Posted: 06 Jun 2017 06:24 AM PDT

Just got back from my second trip to Haiti. Got Giardia...again. It had me thinking, for the people that live where I went they are obviously exposed to the cysts on a daily basis. Are they living with the parasite and e coli infections all day every day? Or do their body's immune systems become adept at fighting off the parasites and e coli so that infestations can no longer occur?

Follow up question: I read that Giardia cysts can last for months, are cold resistant, and resistant to chlorination and UV disinfectants. That being said, when I go to the bathroom, how is our wastewater treatment eliminating the cysts? Or am I just flushing my problem down to someone else later on?

submitted by /u/MangoManchild
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Can two consecutive frames from a camera be exactly the same?

Posted: 05 Jun 2017 04:09 PM PDT

If I'm running a video camera on an extremely still scene (eg. in my living room where there is no wind) and I grab two consecutive frames, is there a possibility of both frames being totally identical? By identical, I mean each pixel is the exact same color, and they both have the exact same checksum when saved to a file...

submitted by /u/hannibaldon
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If you have an infinite amount of things in each box, and an infinite amount of boxes. Do you have more things than boxes?

Posted: 05 Jun 2017 07:02 PM PDT

Why does light pass through glass? I know why it doesn't get absorbed, but why doesn't it reflect off?

Posted: 06 Jun 2017 03:29 AM PDT

How does airport security see inside of bags when putting it through a scanner?

Posted: 06 Jun 2017 06:13 AM PDT

Is a nonlinear system truly indeterminable?

Posted: 06 Jun 2017 05:47 AM PDT

I've been thinking a lot lately about determinism from a physics standpoint: if we disconsider Quantum Physics, wouldn't everything be pre-determined? If all there is are atoms and we can predict the next state of the system based on the current one, technically the future is already known. Of course, with Quantum Physics the future would be nothing but probabilities.

But then I've heard about complex, nonlinear systems, which the human brain would be an example. They're described as being unpredictable and that the state before doesn't necessarily dictate the state after. How can this be? Are nonlinear systems just something that is affected by many variables and it's virtually impossible to account for all of them? However a hypothetical all-knowing creature that had all the information would be able to predict the next state? Or is it truly chaotic?

submitted by /u/fevieiraleite
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Do pixels, bytes/computer memory occupy matter?

Posted: 06 Jun 2017 03:48 AM PDT

Why don't we induce artificial gravity on space stations with a rotating section?

Posted: 05 Jun 2017 02:07 PM PDT

This is something I've been asking myself for a while: the absence of gravity (eg on the ISS) causes problems to astronauts like muscle volume reduction. If one of the parts composing the ISS were rotating, it would induce a gravity-like force pulling radially, that would allow the astronauts to at least exercise passively. Due to low friction, maintaining the rotation wouldn't be expensive.

I'm curious to know why this isn't practical. My guess is that maintaining the sealing between the rotating and noon rotating parts is not as trivial, but again one could "pack" everything.

submitted by /u/UserAlreadyNotTaken
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If we remove one by one elements of natural numbers infinitely many times, will we ever empty the set? What about reals?

Posted: 05 Jun 2017 11:41 AM PDT

Let me explain, the key here is that you remove numbers infinitely many times, you don't stop at one moment. My guess is that if the set is countably infinite we can achieve removing every element because we removed countably infinite numbers from the set and we can construct a bijection from the elements removed to the natural numbers, so there is no room left for another number; but if it is not countable, there is not even a way from where to start removing elements so we wouldn't reach an end(or even a start), am I right? What is the correct answer for this?

submitted by /u/PeriferialGuy
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Why do some photons pass through a mirror?

Posted: 05 Jun 2017 02:42 PM PDT

I had once watched a very interesting youtube video which explained this in detail, but I forgot the reasoning & can't find the video. If someone can find it, I'd love to re-watch!

submitted by /u/sloppies
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How much mass is travelling in the LHC when it is on?

Posted: 05 Jun 2017 03:06 PM PDT

Like the title says, when the Large Hadron Collider is operating, how much does all the particles traveling in it weigh(combined)?

submitted by /u/Tuxinet
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Why is Beryllium-8 Unstable?

Posted: 05 Jun 2017 10:25 AM PDT

Helium-4 (an alpha) is super-stable. So is Carbon-12, which can be viewed as merely 3 alphas. So are Oxygen-16, Neon-20, Magnesium-24, as 4, 5, and 6 alphas, respectively.

Each of these elements can be viewed as merely a pile of alphas, and all but Be8 are all stable, and given my limited, hand-waving understanding of nuclear physics, it makes sense: Nuclei "like" even numbers of nucleons, even numbers of protons & neutrons (an even-even nucleus), and a comparable number of protons to neutrons, which all of these nucleii have.

So why is Be8 the outlier?

Get your shit together Beryllium-8!

submitted by /u/garrettj100
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What IS potential energy?

Posted: 05 Jun 2017 03:01 PM PDT

One that always bothered me is the concept of potential energy. It is said that is energy stored in an object with the famous example of the ball and gravity, but that doesn't seem to make any sense at all it seems as if it is just a term used so that the law of conservation of energy is true. So what is it? How do we know it is a thing?

submitted by /u/Kemo-III
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How accurate are laminar boundary layer models?

Posted: 05 Jun 2017 11:47 AM PDT

I have just finished my second year of university with a module in fluid dynamics in which Laminar boundary layers with zero pressure gradients were looked at. As part of this module, boundary layers with adverse pressure gradients that looks at separation of flows were also looked at.

My question is, how accurate are the models that assume u/U=n-n2 for example where u is the velocity,U is the free-stream velocity and n is the ratio (y/delta) and obtaining solutions based on the no-slip conditions for example.

Thanks!

submitted by /u/spk96
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Do time crystals imply CP violation?

Posted: 05 Jun 2017 07:06 PM PDT

I know they can exhibit spontaneous T-symmetry breaking, so does that in turn imply CP-symmetry violation? Pardon me if I misunderstand the notion.

submitted by /u/BackburnerPyro
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What's the highest temperature attainable by magnifying our sun's light?

Posted: 05 Jun 2017 12:10 PM PDT

Assume a magnifying glass lens the diameter of Mercury located somewhere within the Earth's orbit.

submitted by /u/dick_long_wigwam
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Is there anything that is 100% dense?

Posted: 06 Jun 2017 05:07 AM PDT

Are there any liquids that are less viscous than water?

Posted: 05 Jun 2017 08:20 PM PDT

Looking and the small waves in my pool the other night cause by very slight breezes provoked this thought as it seemed very little force is needed to get a lot of water to move. No better place to ask then here!

submitted by /u/mojoespo33
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Monday, June 5, 2017

Why don't humans have mating seasons?

Why don't humans have mating seasons?


Why don't humans have mating seasons?

Posted: 05 Jun 2017 01:28 AM PDT

Hummingbirds flap their wings around 70 times per second during normal flight...what is the fastest natural movement that humans are capable of, either voluntary or involuntary?

Posted: 04 Jun 2017 07:48 AM PDT

My daughter was watching a cartoon on PBS this morning and they were talking about pollination. It was mentioned that hummingbirds are capable of flapping their wings upwards of 200 times per second. After a quick google, it seems 70 is the more common number for "normal" flight. That's obviously still extremely fast and made me wonder what humans are capable of in terms of pure speed, so I thought I'd ask here.

submitted by /u/imTHATitguy
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what, precisely, is the difference between a dipole-dipole interaction and a "hydrogen bond"? Why is a hydrogen bond (a) different and (b) stronger?

Posted: 05 Jun 2017 05:08 AM PDT

People typically just give the reason that it's the electronegativity difference. But that's wrong - HCl does not show hydrogen bonding - just look at the boiling points - it's very clear that only HF, H2O and NH3 have hydrogen bonding here. There's a huge offset from the rest of the trend because of them. CLEARLY the electronegativity is not the full story, because HCl is not showing anything off-trend in that plot, yet has a bigger electronegativity difference than NH3 does.

I went down the rabbit hole of thinking it was because it had to be period 2 elements - because then they were smaller and therefore had a better orbital overlap with hydrogen, creating a stronger bonding interaction. But NOPE. That's not the explanation either. I found some chem papers floating around that are talking of hydrogen bonding in H2S. WTF? I look on wikipedia and see that hydrogen bonds are supposedly why water gets such a high boiling point whereas H2S doesn't, because H2S doesn't hydrogen bond.

Um. GUYS. Does it or doesn't it?? wtf even IS a hydrogen bond anymore?? if it's just a dipole-dipole thing then why have its own name??! and what's the deal with water's boiling point?? if it ISN'T just that then what IS it? what differentiates it?

I find it maddenning that literally nowhere clarifies this. All it EVER says is lists molecules that hydrogen bond and ones that don't, and states NO REASON why those specific ones do or don't or what the flipping difference is supposed to be. WHATS THE DIFFERENCE?

FOR example. How do I tell whether the electrostatic interactions in HS are hydrogen bonding or not?

BEYOND something vacuuous like "oh it's a sulfur therefore we don't call it that". There are papers out there that DO call it that.

submitted by /u/usernumber36
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Does water have a high heat capacity because it is a polar molecule? Do all polar molecules have high heat capacity?

Posted: 04 Jun 2017 05:48 PM PDT

How does a pencil eraser work?

Posted: 04 Jun 2017 05:51 PM PDT

Chemically or mechanically, what happens when an eraser rubs off lead/graphite from a paper? Why doesn't this work for, say, ink?

submitted by /u/Khenghis_Ghan
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Why does water form little spheres when thrown in the air, versus just spreading out into a random blob?

Posted: 05 Jun 2017 06:42 AM PDT

Has the string theory been validated by any experimental evidence like from the LHC?

Posted: 05 Jun 2017 03:45 AM PDT

Are there better contenders for the theory of everything?

I know just the basics of what the string theory is, that is using vibrating strings and extra dimensions to explain all the different forces and particles. I come from a medical background, so please excuse any gross misunderstandings of the concept.

submitted by /u/zorbix
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What's the current state of Thorium Molten Salt Reactor research?

Posted: 04 Jun 2017 09:46 AM PDT

From time to time talk about Thorium / Molten Salt Reactors pops up as possible solution to our energy problem. As far as I can see it's far away from being well-funded research nowadays. Can someone explain why we put billions into fusion reactor research and not closely enough into Thorium / Molten Salt Reactor research? Also: What is the current state of research? How far would we realistically be away from having such reactors?

submitted by /u/hdsjulian
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How common is prion resistance/immunity in humans?

Posted: 04 Jun 2017 09:21 AM PDT

I have general anxiety disorder, and recently I have been losing sleep over a prion phobia. So, how common is genetic resistance to prion disorders in humans? Specifically, my family is of southern Chinese background, and I would like to know if prion resistance would be common in a typical southern Chinese genotype. Thank you.

submitted by /u/HappyDaysInYourFace
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How are percent chances of rain, storms, etc. determined?

Posted: 04 Jun 2017 05:26 PM PDT

I'm curious to learn how those percentages are determined, and why they vary from station to station.

I also would like to know why we can't be more exact and how "surprise" storms occur with little to no warning.

submitted by /u/knine1717
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Does increasing orbital angular momentum cause electromagnetic radiation to travel slower through a material?

Posted: 05 Jun 2017 04:19 AM PDT

Or rather, can you cause electromagnetic radiation to have more interactions with a material before leaving by increasing its OAM?

submitted by /u/RevEngineer_11
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What happens when Thermite burns asphalt?

Posted: 04 Jun 2017 05:03 PM PDT

I was watching videos on the Battle of Britain, more so memoirs of those involved. And recalled a documentary mentioning the allies use of thermite bombs in cities during late war. Can't remember the documentary though.

Even if not historically true, what would happen to Asphalt when burned by thermite?

Thanks

submitted by /u/Toads45
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Does the density of air change in a controlled volume, if we change the temperature inside the box?

Posted: 04 Jun 2017 08:21 AM PDT

Since density is mass over volume, and the mass isn't changing, and the volume isn't changing, does the density of air not change?

submitted by /u/bush_did7-11
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Can energy be generated through the color force?

Posted: 04 Jun 2017 06:04 PM PDT

Generating usable energy seems to be done by exploiting one of the four fundamental forces. Gravity can be harnessed by dams, electromagnetism by chemical reactions such as the combustion of gasoline, the weak nuclear force through fission, and the strong nuclear force through fusion. I realize that the strong nuclear force and color force are fundamentally the same interaction, but they are distinct. Matter can be created by applying energy trying to separate quarks due to confinement, is the reverse possible?

submitted by /u/mattbros
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How does the huge arch over Chernobyl work?

Posted: 04 Jun 2017 09:43 AM PDT

How does it keep radiation from getting out? Will it help the surrounding area or just keep the reactor from contaminating it more? Is it actually worth it if it's only going to last 100 years, when the radiation will last hundreds of thousands of years?

submitted by /u/PetersPickleParking
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At whitch speed would you hit/be hit by the fewer amount of rain drops?

Posted: 04 Jun 2017 07:27 AM PDT

I seek how to demonstrate the answer. Thank you =)

submitted by /u/Lifender
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What sort of symptoms of radiation poisoning (if any) can be seen in plant life?

Posted: 04 Jun 2017 06:30 AM PDT

Will denser objects sink forever?

Posted: 04 Jun 2017 02:00 AM PDT

If you hve an infinite column of water and place an object denser than water in it, will that object sink forever?

I don't think it will because if pressure inside the water is pgh, then there must be some height h where the pressure balances out the pressure exerted by the object and the water on top, right?

Say water area is A, density is 1, and height is H. And object area is A, density is 2, and height is h. And gravity g is 10.

So if the object is in the water, it displaces the water on top. So now there is water on top of the object, and the water below the object feels the force of both weights.

Force of water on top of object is 1AH*g = 10AH.

Force of object is 2Ah*g = 20Ah

Adding both forces gives 10AH + 20Ah.

Pressure is force/area, so we get (10H + 20h) for pressure.

Is there any height in the water column that will support this pressure and prevent sinking?

submitted by /u/yosimba2000
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Sunday, June 4, 2017

Is gravity weaker on the equator just because the radius is larger, or also because of a centrifugal force?

Is gravity weaker on the equator just because the radius is larger, or also because of a centrifugal force?


Is gravity weaker on the equator just because the radius is larger, or also because of a centrifugal force?

Posted: 03 Jun 2017 02:49 PM PDT

And if a centrifugal force also has an effect, how large is it compared to the difference in radii?

submitted by /u/vanavv
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Why is infrared radiation usually associated with heat even though UV, X ray, and gamma radiation are much higher energy?

Posted: 03 Jun 2017 09:48 AM PDT

Why do we build larger particle colliders with bigger diameters instead smaller diameters traveled multiple times?

Posted: 04 Jun 2017 05:08 AM PDT

The question came up after this article discussing the successor to the Large Hadron Collider.

submitted by /u/Schlaefer
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If we mined the moon, how much could we extract before it's orbit started to decay?

Posted: 03 Jun 2017 09:58 PM PDT

About 20 ants are sitting still in a group on my ceiling. Is this behaviour normal?

Posted: 03 Jun 2017 06:42 PM PDT

I live in Auckland, New Zealand and last night i noticed a group of ants huddled together on the ceiling not moving. After being disturbed they only dispersed very lightly. There was no evidence of a food source or hole leading somewhere. After about 14 hours they are still there. Is this behaviour normal? Either way, what is causing it?

Here is a picture: http://imgur.com/AJ1OXCQ

Thanks

submitted by /u/ghostapplejuice
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Can we accurately (+/- 1 C) predict the weather one month ahead assuming we have the access to enough computational power?

Posted: 04 Jun 2017 12:00 AM PDT

I was reading recently about struggle for computers and humans to generate truly random numbers. It seems like there is no random stuff happening in the nature. Yet, still my weather forecast is sometimes horribly wrong. It appears to me, that since humanity was improving their weather forecasting skills for thousands of years, we should be pretty much good at it.

Assuming we have access to all computational power we need, can we predict the temperature in every location on Earth for every point of time one month ahead?

submitted by /u/Kukis13
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How do you measure the most accurate measurement devices?

Posted: 03 Jun 2017 09:58 AM PDT

Or more simply, if I have access to a device that measures something with a certain, known accuracy, and I have a device with an unknown accuracy that I expect to approach that of my known device, what sort of math should I be doing statistically? How is this generally handled in science/engineering?

Edit: there's been one cool answer which is measuring something different that you correlate using scientific theories. However, that doesn't really explain my original (intended) question of what you do when you're measuring the SAME property directly.

submitted by /u/anprn
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Are viscosity and surface tension of liquids effected by their temperature?

Posted: 04 Jun 2017 01:25 AM PDT

Does, for example, water have a lower surface tension when it is closer to its boiling point and the molecules are beginning to speed up and act similar to gas molecules?

submitted by /u/Acuity_Or_Inability
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What is the pysical meaning of a matrix determinant?

Posted: 04 Jun 2017 04:58 AM PDT

The wikipedia page is being mysterious:

In linear algebra, the determinant is a useful value that can be computed from the elements of a square matrix.

Yeah, I can compute all sorts of neat values from a square matrix, why do we need a special name for it?

Now, I understand, say, eigenvectors: it's a vector that doesn't change direction when multiplied by the matrix. Ditto for eigenvalues, inverses, etc... all of them have neat descriptions of what they mean qualitatively. Yet the only tangible difference between matrices of different determinants depends on whether or not the determinant is zero. What's the big difference between a matrix of determinant 1 and determinant 2?

submitted by /u/thetimujin
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Why does molten metal loses its electromagnetic properties?

Posted: 03 Jun 2017 09:23 PM PDT

Can heat travel through vaccum?

Posted: 04 Jun 2017 12:37 AM PDT

If no,then they can replace the insulator in that hot and cold bottles

submitted by /u/jenith25
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Why dont my headphone wires attract metals if magnetism is caused by the flow of electrons?

Posted: 04 Jun 2017 04:03 AM PDT

Is it possible to move through the overlapping event horizons of two nearby black holes?

Posted: 03 Jun 2017 05:56 PM PDT

And if so, what is this area called? I'd think it'd be something like a Lagrange Point, but not sure.

submitted by /u/Lokarin
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Would more salt dissolve in hotter water heated under higher pressure? what's the limiting factor stopping more salt from being dissolved at greater and greater temperatures and pressures?

Posted: 04 Jun 2017 06:45 AM PDT

At what rate does a wake move in relation to the boat creating it?

Posted: 04 Jun 2017 02:49 AM PDT

Why do some stars produce four lines that protrude from the star whenever a photograph is taken from them?

Posted: 03 Jun 2017 05:06 PM PDT

Since gravity is weaker at the equator, why wouldn't we launch all of our rockets from there?

Posted: 04 Jun 2017 01:11 AM PDT

Does the size of spheres alter the void fraction in a close packing system of a fixed volume container?

Posted: 03 Jun 2017 01:49 PM PDT

Basically, I'm looking at water content in a foam (void fraction), where bubbles of similar size behave in some way like a close packed system of spheres.

My question is, as the bubbles in the foam get larger, (while the cylinder the foam is flowing in remains fixed), does this affect the void space theoretically?

submitted by /u/kewldude69
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If mass can't be created, how do trees and plants grow from tiny seeds ?

Posted: 04 Jun 2017 12:55 AM PDT

Seeds create trees and fruit etc. If mass cant be created how can so much come from something as small as a seed ?

submitted by /u/andydeerfc
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How far does the infrared of a remote reach?

Posted: 04 Jun 2017 04:02 AM PDT

Hello

I'm trying to mess with some projectors using my phone but I was wondering what the reach is for common infrared remotes Like how many meters of air/concrete/glass can it penetrate and still be useful? The projectors I'm interested in are acers and dells. My phone is a LG G5 SE (european model).

submitted by /u/tomanythrowaways99
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How far "up" do you need to be in order to see earth spin below you?

Posted: 03 Jun 2017 03:13 PM PDT

I thought of the question why the earth doesn't spin below helicopter hovering still in the air and learned that the air of earth moves along with it. So how high up do you need to be in order to see the earth spin below you?

submitted by /u/Knight-Jenerik
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Why can we see light through our eyelids when both are closed, but not when only one is closed?

Posted: 03 Jun 2017 05:44 PM PDT

Close both your eyes and stand with a light to your right side. Now wave your hand over your right eye. You'll see the shadow of your hand through your eyelid, blocking the light.

Now open your left eye.

You can no longer see the "red" coming through your right eyelid, and there's no difference in light/coloration when you wave your hand in front of it. It's not picking up any of the light anymore.

Why/how does this happen?

submitted by /u/LinksGayAwakening
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What makes the complex plane so convenient to express the Mandelbrot set with?

Posted: 03 Jun 2017 03:13 PM PDT

I understand you cannot simply substitute the complex number in x2 + c with (x,y) and get the same results, since the "y", or rather, the Imaginary axis of the complex plane functions differently than it's "x" or Real axis. But I don't have an intuitive enough sense of this difference to know why a formula for the Mandelbrot set can't be expressed so simply on a simple coordinate plane using only real numbers.

I'm sure my phrasing betrays a lot more about what I misunderstand than what I understand, so if my question doesn't even make sense, then please help me clear up my initial misunderstandings!

Thanks.

submitted by /u/Sophilosophical
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