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Sunday, April 22, 2018

How does a master key work?

How does a master key work?


How does a master key work?

Posted: 22 Apr 2018 03:45 AM PDT

Why does sunburnt skin feel hot to the touch?

Posted: 21 Apr 2018 03:42 PM PDT

Been sunny in the uk and ouch

submitted by /u/thelongpartofaspoon
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When you shake up a carbonated drink, where does the pressure go once it’s ‘settled’?

Posted: 21 Apr 2018 06:43 PM PDT

What makes people see tennis balls as either yellow or green?

Posted: 22 Apr 2018 05:15 AM PDT

I talked to a friend and we came to different conclusions as to what color a tennis ball is. How come there is a difference at all?

I first assumed it was like the dress but there was only ever one photo with questionable background while pretty much everyone of us has seen a tennis ball in more than one occasion and context.

submitted by /u/bluefirex
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Air molecules travel at 1000 mph. Can we harness that kinetic energy?

Posted: 22 Apr 2018 12:27 AM PDT

Air molecules are travelling at around 1000 mph at room temperature. Why is it not possible to harness all that kinetic energy to produce electricity?

I guess the answer is that for every molecule travelling in one direction, there is another travelling in the opposite direction. Could a structure be designed to trap more energy from molecules travelling in one particular direction? Eg nano-scale V shapes. Air molecules hitting the top of the V would have to bounce back out again, imparting a lot of energy. Molecules hitting the underside would only need a small deflection, imparting less, leading to a downward force on the V.

submitted by /u/Freeewheeler
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Do mental illnesses run in families? Will they be the same mental illness or can they vary between each offspring?

Posted: 21 Apr 2018 10:32 PM PDT

How were the subduction zones discovered and observed?

Posted: 21 Apr 2018 05:30 PM PDT

In my chemistry class yesterday we learned about the pathlength of gas molecules in a gas at STP. What is the pathlength of interstellar hydrogen? What about the intergalactic medium?

Posted: 22 Apr 2018 12:09 AM PDT

What factors affect the orbit of our sun around the galaxy?

Posted: 21 Apr 2018 03:30 PM PDT

Our solar system circles the milky way, but it also "bops" up and down in relation to the plane of the (mostly flat) galaxy. Are we orbiting something massive besides the galactic center of mass? Or are we "oscillating" back and forth through a stable position, destines to come to a rest at some point in the future? Is the current consensus that this movement has some effect on our climate or the risk of impact from celestial objects, or that it is mostly meaningless?

submitted by /u/OlfertFischer
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Why do images on a monitor become negtive when viewed from a certain angle?

Posted: 21 Apr 2018 01:05 PM PDT

How far in advance can we predict a major tectonic event?

Posted: 21 Apr 2018 02:54 PM PDT

Is it even possible to guess based off other events that have happened?

submitted by /u/Nemnexous
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What kind of PRNG algorithm(s) are used by supercomputers running simulations for things like weather modeling or orbital dynamics?

Posted: 21 Apr 2018 08:25 PM PDT

For a specific example, what do ECMWF use in their tropical cyclone simulations? Or, amm I totally off base thinking these simulations need the speed of a PRNG?

submitted by /u/WildWildSouth
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In many-worlds interpretation, when exactly branchings happen?

Posted: 21 Apr 2018 11:25 PM PDT

According to my youtube-video-level understanding of M-W, the universe splits each time particles interact, forming ever growing tree of branches. But isn't the concept of simultaneity undefined in special relativity, making it impossible to form tree with clearly ordered branches? Also, isn't the concept of "particles interacting" just a special case of continuous wave functions interacting? So how do we define branching when every wave function interacts with every other wavefunction, to different degrees, at each moment?

submitted by /u/NotGonnaCooment
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Are there physical or practical limits to how much power batteries can store in a given amount of space?

Posted: 21 Apr 2018 07:21 PM PDT

Why doesn't concentration affect the rate constant?

Posted: 21 Apr 2018 02:47 PM PDT

From the arrhenius equation, it seems the A (or frequency factor) is partially describing the frequency of collisions. Wouldn't A increase with an increasing number of one or both of the reactants?

submitted by /u/readlock
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How is fuel efficiency defined?

Posted: 21 Apr 2018 11:17 PM PDT

Hello community,

I am not a physicist by background but I like to learn. I have always been confused by the concept of fuel efficiency. How is it defined? On one side, I feel that it can be described as how many miles per gallon a vehicle can travel but then I get asked why isn't it the amount of horsepower or torque that can extracted from the fuel.

I can say "Hey Mazda is pretty fuel efficient as they can use 2.0 liter engine and give you 35 mpg" but what about "hey my Mitsubishi evo X can product 800 hp from a 2.0 liter engine" .

To me, they both hold fair arguments. However, I would to ask experts what fuel efficiency is? Is it defined as an equation of horsepower/torque or is it defined as an equation of distance traveled? Why?

Thanks

submitted by /u/SkynetGenisys
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How does a catalyst affect activation energy?

Posted: 21 Apr 2018 08:48 AM PDT

I have seen diagrams of catalysts which hold molecules in place so that they are in the correct orientation for reactions to occur but my textbook says that they provide a alternative route which lowers activation energy.

Does that mean orientation is factored into activation energy or are they separate things?

If so how do catalysts reduce activation energy? Does it do with the way they deform the electron shells of a molecule?

submitted by /u/PocketCharacter
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How often do collisions in LEO happen?

Posted: 21 Apr 2018 09:05 AM PDT

The humanity has been sending quite an amount of satellites, space shuttles etc. to the Earths orbit for the past ~60 years and from my understanding the LEO (Low Earth Orbit) is getting quite crowded by lost satellites, parts of shuttles and smaller debris.

My question is: How often do collisions between currently operational satellites and the ISS happen and how impactful are they?

As a side question, If we somehow created a device that could pull all the unwanted debris towards Earth to burn up in the atmosphere, how impactful would the emissions be on the Earth/would we even notice?

submitted by /u/TaZjec
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Why is majority of the world right-handed?

Posted: 21 Apr 2018 06:28 AM PDT

Just curious about this, there must be some explanation, right?

submitted by /u/Alsttr
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Why does the United States generally have a colder climate than most of Western Europe despite being at the same lattitude, and some parts even being further south?

Posted: 21 Apr 2018 01:48 AM PDT

Do bees have spatial memory when foraging for food?

Posted: 21 Apr 2018 01:33 AM PDT

Hi all

Background - ok my wife found a bumble bee looking docile in the house so she fed it some honey, the bee perked up and flew out of the house.

Now we've had what we think is the same bee fly into our house 3 days in a row and each time fly to same spot in the house where she fed the bee honey - presumably to look for the honey.

So my question is - do bees have memory of locations for food or is it entirely pheromone based?

EDIT: i'm surprised to not see a nature flair to add to this post.

submitted by /u/mitchanium
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Saturday, April 21, 2018

How does sunscreen stop you from getting burnt?

How does sunscreen stop you from getting burnt?


How does sunscreen stop you from getting burnt?

Posted: 21 Apr 2018 06:23 AM PDT

Is there something in sunscreen that stops your skin from burning? How is it different from other creams etc?

submitted by /u/L-Bread
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How are drugs like antidepressants (who’s effects aren’t immediately apparent) developed?

Posted: 20 Apr 2018 10:35 AM PDT

It can take weeks for antidepressants to take effect. How did researchers know to try these substances for depression? We're they being tested for something else and they noticed participants mood improved after a few weeks?

EDIT: Should be "whose" not "who's" in post title

submitted by /u/GrassAndKitties
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How do spacewalking astronauts get rid of body heat and CO2 they generate?

Posted: 20 Apr 2018 06:48 PM PDT

Why does the space shuttle's transonic transition end so abruptly (see linked video)?

Posted: 21 Apr 2018 03:30 AM PDT

In this video from 1:13 to 1:22 you can see the cloudy turbulence as the shuttle's velocity climbs through the speed of sound. I understand that it would commence quickly as the "sound barrier" is breached. What surprised me was how abruptly that transition stopped. Why?

submitted by /u/ModelMagician
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How does the mind make up a physical feeling you've never experienced before while dreaming? For example, a virgin having a wet dream or having a foot amputated?

Posted: 20 Apr 2018 07:11 PM PDT

How do we know the composition of Earth's core?

Posted: 20 Apr 2018 07:33 PM PDT

Why does alcohol kill bacteria?

Posted: 20 Apr 2018 10:29 AM PDT

Why is the output power greater than the input power for a microwave?

Posted: 20 Apr 2018 10:12 AM PDT

On the technical specifications of a microwave it rates the output power at 1000W but the input power is only 850W; how is this possible? Power Information

submitted by /u/greenfrogs365
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When can you consoder a organism dead?

Posted: 20 Apr 2018 01:02 PM PDT

Let's seperate organisms into some categories; Bacteria, Plants and Animals...

Thanks in advance!

submitted by /u/Zequr0
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Is chemical rocket exhaust usually a plasma?

Posted: 20 Apr 2018 07:33 PM PDT

Does hydraulic fracturing contribute to increased seismic activity(earthquakes) and how likely is it for the mix of chemicals+water ,that are used to displace the shale, to contaminate wells and body’s of water?

Posted: 20 Apr 2018 09:45 AM PDT

Why do car wheels look like they're rolling backward when moving fast?

Posted: 20 Apr 2018 12:37 PM PDT

Why do 3 polarising filters, at certain angles, allow some light through when two are at right-angles?

Posted: 20 Apr 2018 03:37 PM PDT

Does everything rotate in space? If so, why?

Posted: 20 Apr 2018 02:17 PM PDT

Why don't lakes with streams flowing into other lakes eventually completely drain into the other lake?

Posted: 20 Apr 2018 07:04 PM PDT

My girlfriend and I were having a heated conversation about this, she said that there has to be some sort of "natural springs beneath the lake keeping it full"and I told her that it keeps full of water because of water cycle.

submitted by /u/Scott_Meacham
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How do plants react to opiates? If I were to, say, use fentanyl as fertilizer, would the plant die? And what about other popular types of drugs, such as coke?

Posted: 20 Apr 2018 03:10 PM PDT

Do animals have a really good sense of time or is it confirmation bias by humans?

Posted: 20 Apr 2018 10:19 AM PDT

I just saw a post on reddit about a neighbor's dog that supposedly meets the OP at a fence every morning before they go to work and it reminded me how my sister's dog would almost always sit at our front door waiting for my sister to walk in after school. It was always around the same time and really seemed to be almost every day. So do animals, even ones that are kept indoors mostly, have a pretty accurate sense of time or is it just that humans know time well so we just attribute the couple times we see this as them having a good sense of time?

submitted by /u/Revenant221
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What is the difference between an imaginary friend and a hallucination? What about Tulpas?

Posted: 20 Apr 2018 08:14 AM PDT

What defines an “oil”?

Posted: 20 Apr 2018 05:33 AM PDT

We have so many types of oil: hair, skin, coconut, petrol, canola, etc. Is there something that they have in common chemically, aside from being liquid?

submitted by /u/krani
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a spider learns to build a net from other spiders or is it instinct ?

Posted: 20 Apr 2018 02:04 PM PDT

Is it more energy efficient to put cold water in a kettle, or hot water?

Posted: 20 Apr 2018 09:54 AM PDT

Is it more energy efficient to use water the a hot water heater has already warmed? Or does it take less energy to use cold water and use a kettle to bring it to boiling temperature.

submitted by /u/flibbityandflobbity
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Friday, April 20, 2018

In the last 5-10 years, there’s been tremendous efforts made by many of the first world countries to curb carbon emissions. Have we made a dent?

In the last 5-10 years, there’s been tremendous efforts made by many of the first world countries to curb carbon emissions. Have we made a dent?


In the last 5-10 years, there’s been tremendous efforts made by many of the first world countries to curb carbon emissions. Have we made a dent?

Posted: 19 Apr 2018 06:40 PM PDT

Where do we stand on present day global carbon emissions vs say 10-20 years ago?

submitted by /u/BimmerJustin
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Why doesn't microwave energy escape through the holes in the screen of a microwave oven?

Posted: 19 Apr 2018 03:03 PM PDT

I've heard the classic explanation as to the wavelength being longer than the spatial frequency of the holes, so the radiation can't "see" the holes. But this is hard for me to visualize since the spatial frequency of the holes would be orthoganol to the wavelength of radiation. Can anyone provide an intuitive explanation?

submitted by /u/lcarusLlVES
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Why is an Alpha particle denoted as a Helium atom?

Posted: 19 Apr 2018 03:43 PM PDT

How is it that we aren't getting cancer after inhaling large volumes of helium gas to change our voice as kids?

What makes an alpha particle highly ionizing but not helium gas?

submitted by /u/Laloquera
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If Radiation is cumulative in our body, is Bluetooth (even with BLE) harmful to humans if we are constantly exposed to it with cellphones, smartwatch, etc. and also from other's electronic devices around us?

Posted: 20 Apr 2018 03:41 AM PDT

Are there any "weird" uses for heavy/transuranic elements?

Posted: 19 Apr 2018 08:04 AM PDT

I recently came across the fact that Americium is used in smoke detectors (Wikipedia). Are there any other interesting applications of other heavy elements?

submitted by /u/lordvigm
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How can we get only sunlight through glass without heating the building?

Posted: 20 Apr 2018 02:34 AM PDT

Sunlight is excellent but it comes with heat, so how do we get only sunlight in a building without heating it up?

submitted by /u/Thammarith
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If we travel 65 million light years, we would be able to see the extinction of dinosaurs, but how is that possible and why?

Posted: 19 Apr 2018 02:59 PM PDT

with super telescopes of course.

submitted by /u/han_gymolo
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Why in some metals is the Hall Effect opposite of what is expected? Like in aluminum for example, say in your set up you expect a buildup of negative charge at the top side of the sample, but instead you get it at the bottom.

Posted: 19 Apr 2018 02:05 PM PDT

In my solid state materials lecture, this was asked as one of our thought starters for lecture last week, and we never really got a satisfactory answer as to why that is. I know it has to do somewhat with the wave-particle duality of the electron, but what exactly that has to do with it I'm not sure.

Any good explanations or links to articles for more reading are appreciated!

submitted by /u/Sublethal_Panic
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How does Ozone stop UV-B and UV-C from reaching the earths surface, what makes it different from nitrogen that allows it to stop the radiation?

Posted: 19 Apr 2018 07:23 PM PDT

How does the SpaceX Merlin rocket engine achieve a TWR of 300?

Posted: 19 Apr 2018 04:40 PM PDT

Edit: Typo. ~200 TWR, impressive nonetheless

submitted by /u/t001_t1m3
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Why are thermal images so blurry? What is hard about making thermal imaging lenses?

Posted: 19 Apr 2018 02:26 PM PDT

Do man made magnets affect the Earth's magnetic field?

Posted: 19 Apr 2018 06:56 PM PDT

I just learned that we've made much stronger magnets than Earth's own magnetic field. The largest magnet reaches 25 tesla but Earth only puts out about 0.000065 tesla. Do they interfere with Earth's? Why does Earths magnetic field reach so far but ours don't? Does that play a role in it?

submitted by /u/Piggs123
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How can electrons and holes have different mobility within a semiconductor?

Posted: 19 Apr 2018 07:59 PM PDT

Holes are just the absence of a balancing electron, so how do electrons move (on average) at a different rate than their absence and vice versa?

submitted by /u/popkornking
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Will we ever be able to see beyond the edge of our observable universe? As time goes on we are able to see further and further, but is the edge just going to stay the same, or possible have less to see since the outer galaxies are expanding faster?

Posted: 19 Apr 2018 01:34 PM PDT

Is there a difference between electrets and ferroelectric materials?

Posted: 19 Apr 2018 10:58 AM PDT

With Wikipedia as my only resource I'm having trouble differentiating the two. What are some common applications for these materials ?

submitted by /u/mattbros
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If the speed of sound is around 420 knots at 30,000 feet, why did Chuck Yeager have to go over 700 mph to break the sound barrier?

Posted: 19 Apr 2018 02:41 PM PDT

I've been playing DCS World and noticed how the speed of sound is different at different altitudes. And also, the Bell X-1 was dropped from around 29,000 feet. It seems to make sense that Chuck Yeager would've had to only go about 500 kn to achieve Mach 1.06.

Edit: he actually flew to 45,000 feet, so it seems he could have gone even slower to reach Mach 1.

submitted by /u/Maelshevek
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Are there any events in history or pre-history similar to the now discredited Tabo Catastrophe?

Posted: 19 Apr 2018 03:23 PM PDT

I heard about the Tabo Catastrophe Theory a while ago and recently saw after some help from a user on r/geology that the theory is no thought to not be true. Are there any examples from planetary science of genetic bottlenecks or loss of civilizations or communities due to natural catastrophe?

submitted by /u/abaxtastic
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Why was Miranda discovered almost a century after the rest of the major moons of Uranus were discovered?

Posted: 19 Apr 2018 05:31 PM PDT

Oberon and Titania were discovered in 1787, Umbriel and Ariel were discovered in 1851 but Miranda was only discovered in 1948 almost 100 years after the previous moons were discovered. How did we miss that Uranus had a fifth moon until after we figured out nuclear bombs and were less than a decade from Sputnik? I looked at the data that Wikipedia had and did a quick back-of-the-envelope estimate of Miranda's visual cross-section and calculated that it was around ~4/25 that of Umbriel's. That explains why it was discovered later than the other moons but why did it take almost a century when it would only have taken an increase of a telescopes diameter by 2.5 would have boosted light collection enough to make it as bright as the other moons seen with the smaller telescope. It isn't that dark, in fact its albedo seems relatively high so that isn't why we didn't find it. How did an entire moon nearly 500 km across manage to go unnoticed until the first half of the the 20th century was almost over?

Edit:I just took another look at Miranda's Wikipedia page and it says that Miranda is the innermost of Uranus's five major moons. Was this part of why we didn't find it? Was it's light drowned out by Uranus's?

submitted by /u/Dovahkiin1337
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How do you break time reversal symmetry without breaking inversion symmetry?

Posted: 19 Apr 2018 11:50 PM PDT

I'm sorry I'm a little tipsy and do not understand magnetism.

submitted by /u/rishlumbaugh
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Scientifically what makes a food burnt And at what state and why does burntness taste so distinct?

Posted: 19 Apr 2018 05:11 PM PDT

Are there any stars that have multiple stars orbiting them?

Posted: 19 Apr 2018 12:05 PM PDT

I know that binary solar systems make up about half of the visible points of light in the galaxy, but those are orbiting each other. Do we know of any stars that have other stars orbiting them? Like, one really big or dense star with other, smaller or less dense stars orbiting them?

submitted by /u/TrueScorpio
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