Pages

Thursday, April 28, 2016

A lot of skin products offer a "sensitive skin" alternative. What is the usual difference in ingredients and why is this better for sensitive skin?

A lot of skin products offer a "sensitive skin" alternative. What is the usual difference in ingredients and why is this better for sensitive skin?


A lot of skin products offer a "sensitive skin" alternative. What is the usual difference in ingredients and why is this better for sensitive skin?

Posted: 27 Apr 2016 11:02 PM PDT

Is there an actual reason the Sun and the Moon are the same size in the sky?

Posted: 27 Apr 2016 06:57 PM PDT

In school, I was taught that it was just a coincidence that the Sun and Moon are the same size in the sky but it seems like such a rare coincidence, there'd have to be a reason, wouldn't there?

submitted by /u/dancingbanana123
[link] [comments]

Is a Yellowstone eruption in the next decade imminent?

Posted: 28 Apr 2016 05:33 AM PDT

What is a tl;dr of your PhD?

Posted: 27 Apr 2016 10:33 AM PDT

Inspired by a similar thread in /r/math. Feel free to ask follow-ups.

Edit: for those posting, consider becoming a panelist and getting flair by posting to the stickied panelist application thread!

submitted by /u/albasri
[link] [comments]

What is the method and way of computational and visual detection of subatomic particles as seen in the CMS?

Posted: 27 Apr 2016 09:08 PM PDT

What happens to photons of light that only penetrate the open ocean so deep? Why don't they hit the seafloor?

Posted: 27 Apr 2016 04:40 PM PDT

Is the universe expanding in three dimensions or four?

Posted: 27 Apr 2016 02:07 PM PDT

If space has been expanding since the Big Bang, is it expanding in the three spatial dimensions, or is spacetime also expanding in the time dimension?

If it's also expanding in time, how does that actually affect progression of time? Does it slow?

submitted by /u/goodevilgenius
[link] [comments]

Does cardiac muscle contain different muscle fiber types, like skeletal muscles do (Type I, II...)?

Posted: 27 Apr 2016 09:04 PM PDT

How are pill vitamins made?

Posted: 27 Apr 2016 08:11 PM PDT

Getting an operation in a few weeks. I've been told to take some vitamins a few weeks before. I understand we get vitamins through food but, how are they made in pill form? They sure are expensive, maybe make my own if it isn't to hard.

submitted by /u/zephyer19
[link] [comments]

why does boiling point of noble gases change as you go down the group?

Posted: 27 Apr 2016 08:10 PM PDT

How long is a second?

Posted: 27 Apr 2016 02:35 PM PDT

IIRC, for measurements like the kilogram we base it off the number of atoms of a specific element. How exactly do we come up with a uniform version of a second, since time is kind of more abstract than mass.

submitted by /u/OneDozenEgg
[link] [comments]

Given x points on a circle, how many different polygons can be constructed?

Posted: 27 Apr 2016 04:29 PM PDT

If a neutralisation reaction is exothermic why does adding heat to the reaction promote product formation (opposite logic to Le Chatelier's Principle)?

Posted: 27 Apr 2016 07:10 PM PDT

Increasing the reaction temperature increases the number of collisions and number of molecules traveling at or above the activation energy, which would favour product formation. However, the overall neutralisation reaction is exothermic, so by Le Chatelier's Principle adding heat should have the effect of favouring the reactants. This is so fundamental, pls help.

submitted by /u/foxcmethoxc
[link] [comments]

What is the fastest algorithm for multiplication of two n-digit numbers?

Posted: 27 Apr 2016 03:39 PM PDT

[Chemistry] How does the voletage of a reference electrode affect the overall cell potential?

Posted: 27 Apr 2016 04:43 PM PDT

Given the vast distances of space. Do radio signals in space ever suffer from attenuation?

Posted: 27 Apr 2016 04:32 PM PDT

A common advice given to runners is to perform a "leg drain". Does the practice have any real basis in physiology?

Posted: 27 Apr 2016 08:10 AM PDT

One website (and it is by no means alone in making this claim) suggests: > Do "leg drains" by lying on your back with your legs extended vertically and feet propped against a wall for three to four minutes. This drains the blood out of your legs so fresh, clean blood can be pumped back into them when you stand up.

Something about the idea of "fresh, clean blood" rings false. But is it?

submitted by /u/celebratedmrk
[link] [comments]

Are gas giants simply stars that failed to "ignite?" Why would one gas clump turn into a star and another one turn into a gas giant?

Posted: 27 Apr 2016 09:55 PM PDT

Are we able to observer and directly quantify any forms of magnetism outside of our galaxy?

Posted: 28 Apr 2016 12:46 AM PDT

Do illnesses like influenza leave small long-term after effects on normally healthy individuals?

Posted: 27 Apr 2016 06:18 PM PDT

Influenza strains can be quite serious diseases that can kill but for most healthy individuals it can be survived with a high likelihood. However, many disease have after effects caused by symptoms experienced through the course of the disease. Have there been studies done to examine if relatively minor diseases have caused lasting effects such as increased susceptibility to future illness? Is there damage accumulated in areas the body isn't typically replacing cells?

submitted by /u/pandizlle
[link] [comments]

There are reports of a tale of an Inuk making a knife out of shit and spit in deeply sub-zero temperatures and using it to butcher a dog, build a sleigh and flee. Is such a knife mechanically possible or is it a tall tale?

Posted: 27 Apr 2016 10:44 AM PDT

link to the apocryphal tale here: https://dontdontoperate.wordpress.com/2012/08/09/wade-davis-zombies-the-inuit-and-the-shit-knife-louis-riel-and-canadian-history/

Previous discussion of this story on TIL:

https://www.reddit.com/r/todayilearned/comments/1w0yxz/til_that_an_elderly_eskimo_in_the_1950s_in_order/

I underline that the tale is from Inuit oral history, so it may have grown in the telling.

Could such a knife hold an edge sufficient to kill, skin and butcher a dog? Could it be mechanically resilient enough to do the job the tale claims it did?

Are the faeces necessary? Would not simply making a similar tool out of ice/snow and spit be just as effective (if true)?

submitted by /u/Gargatua13013
[link] [comments]

Wednesday, April 27, 2016

If I could very accurately measure the temperature increase of an object in a wind tunnel could I use that to calculate the drag?

If I could very accurately measure the temperature increase of an object in a wind tunnel could I use that to calculate the drag?


If I could very accurately measure the temperature increase of an object in a wind tunnel could I use that to calculate the drag?

Posted: 26 Apr 2016 01:46 PM PDT

How does bad weather obscure radar?

Posted: 26 Apr 2016 11:41 PM PDT

In my history textbook, it says that bad weather helped the Japanese fighter planes slip past radar on their way to Pearl Harbor. How does bad weather obscure radar?

submitted by /u/RestSnorlax
[link] [comments]

What is the maximum speed of a liquid running through a tube?

Posted: 27 Apr 2016 06:18 AM PDT

How do prion proteins actually cause a normal copy to misfold?

Posted: 27 Apr 2016 06:27 AM PDT

What do antivirus scanners on your PC actually look for in a file?

Posted: 26 Apr 2016 06:24 AM PDT

Obviously they search for a virus but what attributes of a file gives away thats its a threat to the system?

submitted by /u/Mash-tash
[link] [comments]

If a girl has an above average amount testosterone in her body, will she grow longer than girls with less testosterone?

Posted: 26 Apr 2016 12:46 PM PDT

How different would the Earth be today if the Permian-Triassic extinction event did not occur?

Posted: 27 Apr 2016 02:22 AM PDT

I know this is an oddly specific question, and I couldn't find anything using the search bar. I'm just curious how this would have effected Earth and biodiversity as a whole.

submitted by /u/Froggmann5
[link] [comments]

If the stratum corneum is dead and covered in bacteria, why doesn't it decay?

Posted: 26 Apr 2016 11:56 PM PDT

What is the effect of length (Lorentz) contraction on the outer surface of a rotating sphere?

Posted: 26 Apr 2016 12:41 PM PDT

Assuming the surface's linear velocity is a significant fraction of c and is composed of one connected material at rest. What would be observed from different frames? A similar question could be asked of a 2D disk as well.

submitted by /u/Parzival6
[link] [comments]

Does sound sound different on other planets with different atmosphere densities?

Posted: 26 Apr 2016 10:02 AM PDT

EDIT: Really intriguing and interesting answers. Thank you!

submitted by /u/mango__reinhardt
[link] [comments]

How were the very first computer languages/operating systems coded?

Posted: 26 Apr 2016 10:21 AM PDT

Without any basis with which to code such complex programs, did they have to write everything in binary? Machine code?

submitted by /u/HungoverHero777
[link] [comments]

Why do some people's bruises readily appear while others hardly show?

Posted: 26 Apr 2016 10:02 AM PDT

If I hit my leg hard on a surface, I can feel a bruise, but it won't appear until a yellowish green surfaces a week later. My girlfriend, on the other hand, bruises like a peach. A light tap will bring a purple spot the surface in less than a day. How does this work?

submitted by /u/FarFromAmusing
[link] [comments]

What are the biological/pharmacological mechanics involved that cause tinnitus (ototoxicity) to occur after taking antibiotics i.e. vancomycin/cephalexin?

Posted: 26 Apr 2016 10:24 AM PDT

Do light waves cast a shadow?

Posted: 27 Apr 2016 04:54 AM PDT

How do nuclear power plants draw and convert energy for our use?

Posted: 27 Apr 2016 04:04 AM PDT

I was watching a documentary called Surviving Disaster: Chernobyl, and it made me curious as to how the energy is harnessed, converted for use and what causes it to melt down.

Edit: Added text.

Forgot to add: What does cause it to melt down the way Chernobyl did?

submitted by /u/Dazd95
[link] [comments]

When looking at pictures of Earth taken from space, why do you see only black and no stars?

Posted: 26 Apr 2016 11:55 AM PDT

If there is no "absolute" velocity, how can we determine centripetal force?

Posted: 26 Apr 2016 01:01 PM PDT

For instance, if I look up at a satellite in geostationary orbit, it appears to be standing still. But then, there would be no centrifugal force and it should come crashing down. But from other perspectives, the satellite DOES rotate at the right speed to stay in orbit. What causes that other perspective to be 'correct', whereas mine isn't?

submitted by /u/Huugnuut
[link] [comments]

Why does excessive wing angle of attack (AoA) cause roll?

Posted: 26 Apr 2016 08:18 AM PDT

I do not understand why exceeding AoA limits by pitch causes the aircraft to roll uncontrollably. Also what factors go into AoA limit/how can I reduce the effect with design?

Edit: no flare for Aero??

edit, answer: asymmetric stall

submitted by /u/accounttoberacist
[link] [comments]

Is there any particular reason that some planets rotate very fast on their axis, while others rotate slowly?

Posted: 26 Apr 2016 07:57 AM PDT

For example a day on Jupiter is around 10 hours, Earth is around 24 hours, while a Venus day is around 5,832. What effects the different speeds?

submitted by /u/ed123dead
[link] [comments]

Is there a liquid with the same density of our atmosphere at 1 atm? If so, would a glass full of it not experience refraction?

Posted: 26 Apr 2016 04:50 PM PDT

How do microbes in the human body survive our immune systems?

Posted: 26 Apr 2016 08:25 AM PDT

Is there a constant struggle between the non-human organisms and our immune systems or do they operate without issue?

submitted by /u/ChainedBroletariat
[link] [comments]

Can you charge your phone from a plant? Is this legit?

Posted: 26 Apr 2016 11:05 AM PDT

http://www.bioo.tech/ This reminds me of the miniscuba system I saw on Reddit recently and it was pretty quickly debunked (though who knows if it is still attracting investors). Is this the same kind of "half-science" being used to defraud people again or can this really work?

Found the rebreather device I was referring to. They have raised a ton of money for this thing! https://www.indiegogo.com/projects/world-s-first-artificial-gills-oxygen-respirator--2#/

submitted by /u/EyePad
[link] [comments]

Why does the carboniferous period have a mean surface temp equal or lower than today, when it had 2x the atmospheric CO2?

Posted: 26 Apr 2016 08:09 AM PDT

The mean rise in surface temperature that's been cause for concern within the last 2-3 decades has been almost always attributed to the rise of atmospheric CO2. The Carboniferous period, a geologic era defined by it's large quantities of flora due to high CO2 density (800ppm to today's 400ppm), had a (theorized) mean surface temperature comparable to current temperatures.

What other effects are contributing to the rise of global temperatures if not for CO2? Are other greenhouse gases a greater threat than discussed frequently? Do standard cycles of glaciation play a bigger part in the temperature variance (or lack there of)?

submitted by /u/Snaz5
[link] [comments]

Tuesday, April 26, 2016

How can everything be relative if time ticks slower the faster you go?

How can everything be relative if time ticks slower the faster you go?


How can everything be relative if time ticks slower the faster you go?

Posted: 26 Apr 2016 02:22 AM PDT

When you travel in a spaceship near the speed of light, It looks like the entire universe is traveling at near-light speed towards you. Also it gets compressed. For an observer on the ground, it looks like the space ship it traveling near c, and it looks like the space ship is compressed. No problems so far

However, For the observer on the ground, it looks like your clock are going slower, and for the spaceship it looks like the observer on the ground got a faster clock. then everything isnt relative. Am I wrong about the time and observer thingy, or isn't every reference point valid in the universe?

submitted by /u/MrPannkaka
[link] [comments]

Is entropy low in a black hole?

Posted: 26 Apr 2016 05:42 AM PDT

Does it even make sense to think about entropy in black holes?

submitted by /u/Redbiertje
[link] [comments]

Are there any traits passed on through the Y chromosome that are not related to sex determination?

Posted: 25 Apr 2016 01:48 PM PDT

How many more "new" stars become visible each year?

Posted: 25 Apr 2016 02:19 PM PDT

In other words, how many stars join the observable universe each year?

submitted by /u/Edzeo
[link] [comments]

Both ICl and Br2 have the same number of atoms and approximately the same molecular weight, but ICl is a solid whereas Br2 is a liquid at 0oC. Why?

Posted: 25 Apr 2016 08:04 PM PDT

[Astronomy] Since black holes grow in size, shouldn't that mean there's a solid in the center of the black hole and matter is just added to it over time?

Posted: 26 Apr 2016 06:45 AM PDT

Is there a word for something that's neither unstable nor stable?

Posted: 25 Apr 2016 10:10 PM PDT

If you stick a ball on a hill and nudge it, it will roll off the hill. It's unstable. If you stick it in a valley and nudge it, it will roll back. It's stable. If you stick it on a plane with friction, it will just move a little and stay there. It's not really either. Is there a name for that?

submitted by /u/DCarrier
[link] [comments]

Are there forces on a spacecraft other than acceleration during a flyby? (Powered or unpowered)

Posted: 26 Apr 2016 06:32 AM PDT

Looking at the Oberth effect (powered flyby) and unassisted flyby, would there be any forces other than F=ma on the craft due to gravity or other issues? If periapsis was low enough, atmospheric friction would probably come into play, but are there other forces? Thanks.

submitted by /u/keithgcochran
[link] [comments]

Is it possible to use other hadrons to catalyze nuclear reactions akin to photocatalysis of chemical reactions?

Posted: 26 Apr 2016 06:22 AM PDT

A bit of background: My quantum mechanics course was in the chemistry department and pertained specifically to interactions within electromagnetic force.

Sometimes photons are used to put reactants into an excited electronic, vibrational, and even rotational state that has the lowest kinetic (as opposed to thermodynamic) barrier to reaction. This leads to faster reactions at lower temperatures.

Is controlled use of other gluons akin to lasers are for photons theoretically possible, feasible, or currently done? What about the bosons that carry the weak force?

submitted by /u/Liberals_to_Gulag
[link] [comments]

How do photons have momentum?

Posted: 26 Apr 2016 04:57 AM PDT

Could someone provide the answer without pointing out Einstein's equation saying its incomplete and all? Practically, physically how is it possible for a massless object to have momentum? Analogies are appreciated.

submitted by /u/Ashen_Cyborg
[link] [comments]

Would moving something at a high speed increase its temperature?

Posted: 26 Apr 2016 04:31 AM PDT

Temperature is just a measure of average kinetic energy. Say, in a vacuum (where friction from air resistance is... unlikely), would moving an object extremely quickly increase the average kinetic energy of the particles in the object enough to noticeably raise its temperature?

submitted by /u/pm_MGSVTPP_steamcode
[link] [comments]

Are mass and weight directly related?

Posted: 25 Apr 2016 06:04 PM PDT

Say you have an object, and you want it to become heavier, without changing its mass (adding external objects). Example: a handheld object for a virtual reality device, in order to achieve a more realistic experience, they controllers need to add weight.

Is this somehow possible? Just a random question

submitted by /u/Jpalermo99
[link] [comments]

In a Neutron Generator, how is the Neutron Beam "Focused"?

Posted: 25 Apr 2016 02:44 PM PDT

I understand the accelleration of a Deuterium or Tritium nucleus into a D/T target, creating fusion and the product neutrons - but how are those neutrons collected?

submitted by /u/statdance
[link] [comments]

Can isotopes commonly used in food irradiation induce radioactivity through neutron activation?

Posted: 26 Apr 2016 02:00 AM PDT

I have two trusted sources at ends. This study: http://www.ncbi.nlm.nih.gov/pubmed/18220055 , claims that radioactivity can be induced in food by the isotopes Cobalt-60 and caesium-137, however (understanding wikipedia is not perfect) it explicitly states here: https://en.wikipedia.org/wiki/Induced_radioactivity that; "The isotopes used in food irradiation (cobalt-60, caesium-137) both have energy peaks below this cutoff and thus cannot induce radioactivity in the food". Providing the minimum required energy for this is 2 MeV for deuterium. Is wiki wrong with their MeV requirement, is this study wrong, or can you provide another answer, thanks.

Sorry for the formatting, I'm still learning.

submitted by /u/Trajjan
[link] [comments]

How can propellants push a spacecraft if there's nothing to push off against?

Posted: 26 Apr 2016 12:10 AM PDT

If a rocket burns fuel to accelerate in space, why does that force push the rocket if there's no atmosphere or mass to push off against?

submitted by /u/mustangbanana
[link] [comments]

How does Ph level affect on ice cubes?

Posted: 25 Apr 2016 09:58 PM PDT

Are elliptical orbits any more stable than circular orbits?

Posted: 25 Apr 2016 05:52 PM PDT

I'm in an argument with another user on reddit (/u/somerandomguy02), over on /r/todayilearned. Here is the thread.

/u/somerandomguy02 believes that all orbits are non-circular orbits because non-circular orbits are more stable than circular ones. I've tried my hardest to convince him otherwise, going as far as providing sources to prove that he is incorrect.

I do not understand why he has any reason to believe this other than misunderstanding that the statement "elliptical orbits are stable." means that closed orbits are stable, and not that elliptical orbits are more stable. He also does not understand that circular orbits are a special subset of elliptical orbits, because circles are a special subset of ellipses, and refuses to believe the latter.

I know that science is not a democracy, but I think having a large number of people verify that he is incorrect would help lead him to admit that he is incorrect, or at least believe that he is incorrect, so therefore I would greatly appreciate it if you were to confirm this.

submitted by /u/Artillect
[link] [comments]

If the cooling of one object is caused by the transfer of heat to another object, how does the Earth cool in winter? Isn't space empty?

Posted: 25 Apr 2016 10:26 AM PDT

My icy drink is cooled because it transfers its own heat energy to the ice. How then does Earth cool, if there's no surrounding matter in space to soak up the Earth's heat energy?

submitted by /u/MemeHunter421x
[link] [comments]

At what temperature does a magnetic material (EX: Neodymium) lose its magnetic field?

Posted: 25 Apr 2016 10:19 AM PDT

And by lose, I mean to the point at which its negligible or has the same intensity as the average nonmagnetic material.

submitted by /u/Xanjaxn
[link] [comments]

Why is thermodynamic equilibrium equal to maximum entropy?

Posted: 25 Apr 2016 06:10 AM PDT

I already asked this, but the answer got deleted so... :/

submitted by /u/9voltWolfXX
[link] [comments]