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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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Thursday, April 19, 2018

This may be a stupid question, but what defines GMO. Is it simply changing a plant through cross pollinating (at its simplest level) such as Mendel, or does GMO mean laboratory tested and genetically altered through a laboratory?

This may be a stupid question, but what defines GMO. Is it simply changing a plant through cross pollinating (at its simplest level) such as Mendel, or does GMO mean laboratory tested and genetically altered through a laboratory?

This may be a stupid question, but what defines GMO. Is it simply changing a plant through cross pollinating (at its simplest level) such as Mendel, or does GMO mean laboratory tested and genetically altered through a laboratory?

Posted: 18 Apr 2018 09:59 PM PDT

How is it possible for every human to have different voices?

Posted: 18 Apr 2018 07:54 PM PDT

If microwaves are "non-ionizing", how does a grape create plasma in a microwave oven?

Posted: 18 Apr 2018 04:24 PM PDT

Is non-ionizing radiation really incapable of ionizing ANY molecule?

submitted by /u/lcarusLlVES
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How do swept wings differ from straight wings in performance?

Posted: 18 Apr 2018 04:12 PM PDT

Are bird/whale (animals in general) songs learned or genetically programed? IOW, are animal songs the same in captivity as nature?

Posted: 18 Apr 2018 08:12 PM PDT

Are bird/whale (animals in general) songs learned or genetically programed? IOW, are animal songs the same in captivity as nature?

My dad and I were talking about this and we didn't know. We heard (but after googling I couldn't find this) that there was a university test whereby chickens were raised for generations in captivity and never squawked seeing shapes (such as squares and triangles) fly over, but then fifteen generations later the researchers sent one hawk and all the chickens were frightened.

This is a general question about genetically remembered fears or traits that aren't exactly taught.

Edit: I wasn't sure which flair to put this under. I think it would be more appropriate for zoology (but that is not present); so, I put it under biology. I think this is accurate since I ultimately am asking about the biological questions relating to genetically implied actions.

submitted by /u/Isatis_tinctoria
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Does rate of dissolution of salt change while a quantity of salt is being dissolved?

Posted: 19 Apr 2018 07:07 AM PDT

I have two buckets full of enough water that the amounts of salt I am attempting to dissolve will not saturate the solution. I want to dissolve a quantity of salt, X cups, in one bucket. In the other bucket I want to dissolve 2*X cups. Will these two quantities finish dissolving at the same time? Does the amount of salt already dissolved in the solution affect the rate of dissolution?

submitted by /u/electrodynamometer
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Why do some solids (like metals) make a *ting* noise when struck, and others (like wood or plastic) make a *thunk* noise?

Posted: 18 Apr 2018 07:32 PM PDT

Why do the acoustics of certain materials vary? Why can't you make a guitar string out of carbon fiber for instance?

submitted by /u/JohnH550
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Does bees' honey concentrate or filter out toxins from the original flowers?

Posted: 18 Apr 2018 02:54 PM PDT

I was thinking of this recently when reading an article on the main page about NYC beekeepers. In a pollution-heavy area, where flowers might be exposed to toxins in the ground/water/air, can those toxins concentrate into honey? Or is pollen and/or honey somehow insulated from toxins by some mechanism? Since I imagine it will be asked, we can break them out into earthly/local contaminants (heavy metals in the soil, agricultural runoff, etc) and air pollution from cars/trucks/smog/etc.

submitted by /u/polishprocessors
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Sending a rainbow into a prism?

Posted: 19 Apr 2018 02:56 AM PDT

If colored light rays were to send into a prism in the correct angles (Just the reverse of what happens to white light), would it produce actual white light?

submitted by /u/mantlair
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How does voyager 1 not run out of fuel?

Posted: 18 Apr 2018 08:06 PM PDT

Sorry if this is a dumb question, but that thing is in space since 1977 if I'm not wrong. How has it not ran out of fuel? Or hit a meteor or something?

submitted by /u/M33RHARIS
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Are Fourier transforms something fundamental in our Universe?

Posted: 19 Apr 2018 03:49 AM PDT

So I was watching a Sixty Symbols video about bandwidth and Fourier transform and in some part of it, it is said that Δf x Δt ≈ 1, where Δf is the range of frequencies that can pass through the cable and Δt is the minimum pulse width that those frequencies can make(Fourier). So for example in an optical fiber cable you can't send very short pulses because the Fourier transform of that pulse would have frequencies components beyond the limit of the optical fiber. My question is: That doesn't imply that the Fourier transform(and its sinusoids components) are not only a mathematical tool but a fundamental part of our universe? I mean, shouldn't the minimum pulse width be determined only by the wavelength of the frequency carrying the signal?

submitted by /u/jrmiranda
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Why do I sometimes get the urge to jump from a great height, randomly destroy something expensive, or to put something disgusting in my mouth?

Posted: 19 Apr 2018 03:07 AM PDT

In islands such as Hawaii which are made from lava hit spots how does the lava stack up to make a island since the lava comes from the bottom up?

Posted: 19 Apr 2018 01:31 AM PDT

Is it possible to transmit wireless data at the frequency of visible light? In that case, we could see the data transmission.

Posted: 18 Apr 2018 09:38 PM PDT

If a supersonic aircraft gets hot from compression heating, does that mean that the air behind it is colder because it transferred heat to the aircraft?

Posted: 19 Apr 2018 12:33 AM PDT

Additionally, if you had a perfect theoretical model (ignoring the inconvenient physics) could you fly a second aircraft behind the first that would get colder?

submitted by /u/18107
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How do LIGO results infer distance/size etc of source?

Posted: 19 Apr 2018 01:25 AM PDT

I have some questions about how LIGO works... I understand the basics and how it works by basically detecting very small changes in a laser beams path. Thats fine I get that that is an indicator of gravitational waves.

So..

  1. How can we identify that the waves are from X billion years ago?
  2. How do we know the direction the wave came from?
  3. How do we know the decay rate of a wave?
submitted by /u/liltbrockie
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This is not a medical advice request. Lansoprazole - a common PPI (as prescribed to me) states not to take indigestion remedies "2 hours before, or after" taking the medicine. Why? I have searched, no actual answers.

Posted: 18 Apr 2018 11:05 PM PDT

I am not asking for medical advice.

I am struggling to find out why this time line is stated on the pamphlet, and the label my pharmacist(s) put on the packaging. Basic searching (as far as I have delved) only results in the actual medicine and its uses, not why you shouldn't take "indigestion remedies" within in this period. I also cannot find what types of indigestion remedies they are saying to avoid.

I respect this isn't ELI5, but I'd appreciate some clarification as to why, that a layman can understand. If not, I'm happy to read papers relating to this to try and figure my own way around, slowly. Thank you.

Oh, they are gastro-resistant (enteric, if you prefer) capsules.

submitted by /u/neffs
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A catalyst lowers the activation energy for a reaction. Is there something that increases it, like an anti-catalyst?

Posted: 18 Apr 2018 09:45 AM PDT

How (if they do at all) do orb-weaver spiders establish territories?

Posted: 18 Apr 2018 09:07 PM PDT

There's lots of spiders near my house. How do they determine which one gets to build its web in the sunny spot near the outside faucet (which is like an all-you-can-eat insect buffet), and which ones have to go up to the third floor (where there never seems to be as many insects caught in the webs).

Strangely the spiders on the ground level, with the prime insect supply, seem to be smaller than the vast monsters on the third floor.

submitted by /u/AWinterschill
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Where exactly does the LHC get protons?

Posted: 18 Apr 2018 12:35 PM PDT

I want to a talk recently that stated that the LHC accelerates protons to relativistic speeds, and I was wondering where they get the protons? I was under the assumption that they create a positive hydrogen ion, leaving just the proton - is this correct? And if so, how is it done?

Thanks!

submitted by /u/Undercover_Ostrich
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What's The Deal With ITER's Funding & Timeline?

Posted: 18 Apr 2018 06:29 PM PDT

It's supposed to take until 2025 to be assembled and then another 10 years for the full scale experiments.

It's estimated to cost 20 billion Euros. This seems like a paltry sum for Europe, China, or the USA, let alone a collaboration between them and Japan, India, Russia, etc. so it seems like participants could fairly easily pony up additional funding.

Does building it just take that long due to the nature of the project or is it a matter of funding such that doubling the funding move the 2035 date up to the 2020s?

submitted by /u/pennypurplepyramid
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