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Tuesday, April 19, 2016

American Chemical Society AMA: I'm Patti Galvan, I help K-8 teachers bring more chemistry to their students. Ask me anything about being a great chemist/scientist guest speaker in an elementary or middle school classroom.

American Chemical Society AMA: I'm Patti Galvan, I help K-8 teachers bring more chemistry to their students. Ask me anything about being a great chemist/scientist guest speaker in an elementary or middle school classroom.


American Chemical Society AMA: I'm Patti Galvan, I help K-8 teachers bring more chemistry to their students. Ask me anything about being a great chemist/scientist guest speaker in an elementary or middle school classroom.

Posted: 19 Apr 2016 05:07 AM PDT

Hi Reddit!

I'm Patti Galvan, K-8 Education Specialist at the American Chemical Society. Along with colleagues, I develop resources for K-8 students and their teachers. Another part of my job is helping chemists who volunteer to be guest speakers in an elementary or middle school science class. If it's Career Day in your child's school, for example, what could you say and do to represent chemistry and make your child proud? At this point in the school year (April), we are entering Career Day and guest speaker season!

I enjoy helping chemists develop a presentation that will give students a positive experience learning science, please the teachers, and have them invited back for years to come. I help scientists guest speaking in classrooms feel cooler than the firefighter!

For chemists who want to make more of an impact than a one-time visit can provide, ACS offers the Science Coaches program which is currently recruiting chemist-teacher partnerships. Find out more at www.acs.org/sciencecoaches

I have seen both sides, as a teacher inviting guest speakers into my classroom, and as a guest speaker representing chemistry at my son's elementary school. Ask me anything about how to be a great guest speaker in an elementary or middle school science class.

I will be back at 11:00 a.m. EDT (8:00 a.m. PDT; 3:00 p.m. UTC) to answer questions.

submitted by /u/AmerChemSocietyAMA
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Why aren't decimals countable? Couldn't you count them by listing the one-digit decimals, then the two-digit decimals, etc etc

Posted: 18 Apr 2016 08:37 PM PDT

The way it was explained to me was that decimals are not countable because there's not systematic way to list every single decimal. But what if we did it this way: List one digit decimals: 0.1, 0.2, 0.3, 0.4, 0.5, etc two-digit decimals: 0.01, 0.02, 0.03, etc three-digit decimals: 0.001, 0.002

It seems like doing it this way, you will eventually list every single decimal possible, given enough time. I must be way off though, I'm sure this has been thought of before, and I'm sure there's a flaw in my thinking. I was hoping someone could point it out

submitted by /u/ikindalikemath
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Can Blackholes absorb matter larger than itself?

Posted: 18 Apr 2016 06:49 PM PDT

Was having this debate with a friend and he said that blackholes cannot absorb anything larger than themselves. Personally I felt like he was wrong since not even light can escape from one. I would appreciate an answer, thanks!

EDIT- Thanks for all your amazing answers. I tried to respectfully explain to my friend how he's wrong but he wouldn't have it. I said please provide a source that proves that "blackholes can only absorb things smaller than themselves" and he simply said, The Universe in a Nutshell by Stephan Hawking.

I have decided to avoid getting into debates with this friend again because he's always right. Even topics he knows nothing about he's seemingly an expert. When trying to tell him how he's "wrong" he laughed, smirked and said that I have no idea what I'm talking about. Anyways short rant over but thanks for the great answers guys.

submitted by /u/AtomicKush
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Why can't LASIK give me super vision?

Posted: 18 Apr 2016 12:48 PM PDT

I've been tossing around LASIK eye surgery for a bit. But I was wondering if eyesight can be corrected to 20/20, why not go for 20/10 or 20/5 or full on superpower 20/2. Is it a function of the operation of the eye not just the lenses that limits it?

submitted by /u/AristotleKnowsAll
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Are there any solar systems / stars outside galaxies? If so, does it have any impact on the planets/stars?

Posted: 18 Apr 2016 05:49 PM PDT

Why are rocket engines not able to throttle down all the way?

Posted: 18 Apr 2016 06:20 PM PDT

In the case of the Merlin 1D, it can throttle down to 70% max thrust. What is preventing it from going any lower than this?

submitted by /u/FTLSquid
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Do biochemical processes have binary on/off switches?

Posted: 18 Apr 2016 07:33 PM PDT

I have a vague perception that biochemical processes don't generally have a binary on/off switch, but tend to occur on a gradient according to concentrations of precursors, enzymes, and other factors affecting the rate at which they occur.

For example, the simple Biology 101 story is that insulin is produced when blood sugar is high and glucagon is produced when blood sugar is low. But my sense is that insulin would still be produced, albeit at reduced levels, even in a hypoglycemic state.

Is this correct? If so, are there any notable exceptions?

submitted by /u/brberg
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Why do different electric guitars sound different when the sound comes from the same process?

Posted: 18 Apr 2016 09:52 PM PDT

For example.

Why is it that people will say that fender Stats and Gibson Les Paul guitars sound different when they use the same pickups.

People say that it has something to do with the neck of the guitar, but why would this influence Faraday's law with the pickups?

submitted by /u/Windston57
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Why does sodium dissolved in water (through table salt for example) not react like pure sodium does when it touches water?

Posted: 18 Apr 2016 06:28 PM PDT

If my basic understanding of chemistry is correct, the bond between Na and Cl in table salt vanishes when it is put into water. Wouldn't this leave pure atoms of Na floating around which are highly reactive with water? Probably I'm missing something obvious from one of my teacher's lectures that I zoned out in.

submitted by /u/MagicMadDawg
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Does the density of a charged object affect the amount of force it feels in an electric field?

Posted: 18 Apr 2016 10:13 PM PDT

So far I've only looked at the effects of electric field on a charged particle - a one-dimensional point. Is there any distinction when dealing with a 3D object?* If so, is the object's density a factor in the force it feels?

In regards to the answer, do the same principles apply for density of 3D objects in a gravitational field?

I was thinking density doesn't matter where Newtonian physics breaks down (space or quantum) since density doesn't show up in the gravitational force equation, nor in the electric force equation. I just realised that in the equations mass of the object is density/volume. Then I assume it is equally important; true? Are 3D objects on Earth affected?

*Side question: what happens to 2D objects in a field? Is that even possible?...what does that even mean?

submitted by /u/potatoes4brainz
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Can you make a waterproof Shear-Thickening Fluid?

Posted: 18 Apr 2016 04:02 PM PDT

Ok, as many of you are probably aware, the military uses a shear thickening fluid on kevlar to create pierce-proof body armor. They use Silica Nanopowder (or Calcium carbonate nanopowder) dissolved in Polyethylene Glycol, then they dilute it with ethanol, and soak the kevlar in it. Then they bake the kevlar to make the ethanol evaporate, leaving the Shear Thickening Fluid behind, between all of the fibers of the kevlar.

Well, my question is this: Can you make a waterproof shear-thickening fluid that would do the same?

I was considering using Polydimethylsiloxane silicone fluid that has dissolved calcium bicarbonate in it, and then try using Boric Acid to create the solidity needed? (This would be a variation of Silly Putty) And then maybe dilute it in pentane, dip a shirt in and bake the pentane out? Would this work?

Is there a better waterproof liquid + calcium carbonate nanopowder that would make a better, or stronger Shear-Thickening fluid than the one I presented?

Any help in this endeavor would be appreciated!

submitted by /u/Hutch0687
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Is there a scientifically viable explanation of quantum mechanics that suggests the universe is deterministic?

Posted: 18 Apr 2016 04:58 PM PDT

How do blacklights work?

Posted: 18 Apr 2016 08:15 PM PDT

Black lights shoots uv light at stuff and that uv light is then somehow seen by our eyes? Also wouldnt this uv light be harmful?

Ps: would this be a physics question or a biology one?

submitted by /u/D-Spark
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Besides human activity, how is the carbon in fossil fuels returned to the ecosystem?

Posted: 18 Apr 2016 06:18 PM PDT

Based on the biogenic theory of fossil fuels, the carbon locked into petroleum, coal and natural gas comes from millions year old biomass. Human activity releases that carbon in the form of carbon dioxide, which is then returned to the ecosystem.

Besides humans burning fossil fuels for energy, how is that carbon returned to the ecosystem?

As a followup - is there any model that states all carbon would eventually be locked away in fossil fuels and the earth would end up barren as a result?

submitted by /u/kingcoyote
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For HIV Drugs like Epivir, Which is a reverse-transcriptase inhbitor, why is this not harmful (deadly) to the entire organism?

Posted: 18 Apr 2016 10:37 AM PDT

How can a drug inhibit Complementary RNA production, and not kill off the organism? I understand cRNA is necessary for viruses like AIDS to disseminate, but if it's a type of RNA the body produces, doesn't the body need it to survive?

submitted by /u/ljpaulsen
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Why don't we make "solar panels" that convert radiation from radioactive material to electricity?

Posted: 19 Apr 2016 01:52 AM PDT

Solar panels; point them at the sun and get electricity from it converting that radiation. Yet we have potent sources of radiation in the form of radioactive material. We have stockpiles of nuclear waste. Why can't we, or why don't we, use the same principle as solar energy cells to turn radiation into electricity?

submitted by /u/securitywyrm
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Has anybody explored the "188 day earthquake cycle" theory?

Posted: 19 Apr 2016 03:15 AM PDT

With several of our recent larger earthquakes happening, I got thinking about this again.

I discovered this theory that the alignment of Jupiter and Saturn have influence on the timing of earthquakes and have not been able to successfully bunk/debunk it. I would think that the moon's perigee/apogee would have a much greater influence on the earth than distant planets, but I wonder if they add or subtract in different ways that finally push that tectonic plate over the edge. All of the information I have come across about it is bottom-feeder conspiracy theory links and those who claim to have debunked it without a large enough data-set. Then again, those who claim it's true (e.g.: Japan 9.0 and the Indonesia one) do not have large enough data-sets either.

  • Is it possible to aggregate all the USGS data from all time and crunch the numbers looking for patterns in figures like: total magnitude for a day, largest magnitude, quakes only above 3.0, 5.0, 7.0 and search for some patterns to see if they correlate to the cycles of certain celestial bodies?
  • Is there somebody who has an occupation that has a background in seismology that has already done these types of studies?
submitted by /u/PigNamedBenis
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Do animals need to learn language from a young age like humans do?

Posted: 18 Apr 2016 03:15 PM PDT

I know animals don't have the same range of communicative powers that humans have, but most have some degree of physical and or vocal ability to express themselves to one another.
My question is: how learned are these interactions? For instance, would apes raised away from exposure to other apes be able to communicate effectively if they were introduced to a larger group? I know tigers use a wide spectrum of vocal cues to convey information (on emotional states, etc), so would a tiger raised away from other tigers be mute in the same way an isolated human would be?
Have there been any interesting cases studied? Just how instinctual is animal language?
Sorry for all the questions, but this has been on my mind a lot recently. Thanks for y'alls help! Cheers!

submitted by /u/cclef615
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Why does a Helium nucleus have less mass than the mass of two protons + two neutrons?

Posted: 18 Apr 2016 11:26 AM PDT

Hello, Science Whizzes!

I'm learning about the proton-proton chain.

Six protons combine over several steps to form:

  • 1 helium nucleus, comprised of two protons and two neutrons.

  • 2 protons

  • 2 neutrinos

  • 2 positrons

The following figures come from Wikipedia, and presumably from some more reviewed source prior to that:

Mass of proton: 1.672622 x10-27 kg

Mass of neutron: 1.674927 x10-27 kg

The mass of two neutrons + two protons, using the figures above = 6.695098 x1027 kg

But: the mass of an alpha particle (which I gather is for all practical purposes, a Helium nucleus): 6.644657 x10-27 kg

Should they not be equal?

Going back to the proton chain:

Mass of positron: 9.109383 x10-31 kg

Mass of neutrino: smaller than rounding error, above.

Inputs = 6 protons = 1.0035732 x10-26kg

Outputs = 4 protons + 2 neutrons + 2 positrons + 2 neutrinos = 1.00421639 x10-26 kg

Thus, the outputs weigh more than the inputs. This is at odds with numerous sources that assert that fusion of hydrogen into helium releases 0.7% of the mass as energy.

If someone could either explain what I've missed or be willing to coauthor a paper disproving the fusion theory of star energy, I'd appreciate it.

Edit: Thanks, everybody. I'm disappointed not to have disproven orthodox nuclear theory via arithmetic, but am pleased to learn that there's a reason for the discrepancy. I'm also annoyed that my (basic astronomy) class doesn't even mention binding energy.

submitted by /u/San_Fran_Dan
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How does Platypus venom vary from other venoms in the animal world, and what is it's effect and purpose?

Posted: 18 Apr 2016 01:25 PM PDT

How can light move things?

Posted: 18 Apr 2016 03:13 PM PDT

I read somewhere that light is able to move things.

But if light is massless then there shouldn't be a force to move things with?

submitted by /u/akaChromez
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Before IV's, how would comatose people be kept alive (food, water, etc.)?

Posted: 18 Apr 2016 10:51 AM PDT

Is having a good memory genetically passed down or totally random?

Posted: 18 Apr 2016 02:52 PM PDT

Monday, April 18, 2016

AGU AMA: I’m Dr. Kim Cobb, and I’m here to talk about the science of climate change, El Niño, and the reconstruction of past climate. And I’m Dr. Anne Jefferson, and I’m here to talk about how water moves through landscapes and how land use and climate change alter hydrology. Ask Us Anything!

AGU AMA: I’m Dr. Kim Cobb, and I’m here to talk about the science of climate change, El Niño, and the reconstruction of past climate. And I’m Dr. Anne Jefferson, and I’m here to talk about how water moves through landscapes and how land use and climate change alter hydrology. Ask Us Anything!


AGU AMA: I’m Dr. Kim Cobb, and I’m here to talk about the science of climate change, El Niño, and the reconstruction of past climate. And I’m Dr. Anne Jefferson, and I’m here to talk about how water moves through landscapes and how land use and climate change alter hydrology. Ask Us Anything!

Posted: 18 Apr 2016 04:50 AM PDT

Hi Reddit!

I am Kim Cobb, Professor and Georgia Power Scholar in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. I am also Editor of Geophysical Research Letters. My life's work is dedicated to unlocking the patterns of past climate changes from corals and cave stalagmites, with a particular focus on El Niño. With the current record-breaking event still underway, it's been a busy year full of field expeditions to my remote research sites. Together with my students, we've been able to uncover the first evidence that El Niño events may be strengthening in response to anthropogenic climate change. Most recently, I participated in an interdisciplinary expedition that documented extensive coral mortality on an island in the very middle of the Pacific. I enjoy tweeting at @coralsncaves, and blogging (infrequently) at http://cobblab.blogspot.com. In my spare time, I'm raising four children ages 5-8. You can view my lab web-page at http://shadow.eas.gatech.edu/~kcobb

I am Anne Jefferson, recently tenured faculty in the Department of Geology at Kent State University. I am also a AAAS Public Engagement Fellow. My research answers questions like "What happens to streams when climate changes from snow to rain in the winter?" and "How can we manage stormwater to mitigate the effects of urbanization and prepare for climate change?" and "Does stream restoration work?" I've studied water everywhere from groundwater deep below lava flows to the mighty Mississippi River, from green rooftops to the pipe network below our streets. I am a physical hydrologist and I spend a lot of time carefully measuring how much water there is, how it's moving, where it has come from, and how old it is. I also I collaborate with scientists who study water quality, stream ecology, landscape architecture, and human institutions. Water is a very interdisciplinary subject! Learn more about my work on my web page: http://all-geo.org/jefferson/. Follow me on Twitter: https://twitter.com/highlyanne.

We will be back to answer your questions between 12 and 1 pm EDT on Monday, April 18th, Ask Us Anything!

submitted by /u/AmGeophysicalU-AMA
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If you were to drive in a car at the same speed as a bullet and shoot backwards, would the bullet hang in mid-air? If so, how long?

Posted: 17 Apr 2016 08:37 AM PDT

In Terminator, when they say skynet "begins learning at a geometric rate," what does that mean?

Posted: 17 Apr 2016 08:54 PM PDT

What base are the Roman numbers?

Posted: 17 Apr 2016 10:33 AM PDT

It seems to me that they have no base. They have 7 symbols (I,V,X,L,C,M) but it isn't a base 7?

submitted by /u/aimnox
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Is it possible to calculate the initial velocity and angle of a basketball shot, knowing only the angle at which it enters the hoop?

Posted: 17 Apr 2016 10:12 AM PDT

I was discussing this with my physics teacher and he was not able to calculate it. You do know the distance from the hoop, the starting height of the shot, the hoops height and the angle at which the ball enters the hoop. In our example, the ball enters at 34 degrees. Is there any way to calculate the initial velocity and the angle at which the ball was shot?

submitted by /u/onetwenty1
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Why are so many of the energy levels of a hydrogen atom degenerate?

Posted: 17 Apr 2016 06:55 AM PDT

Specifically, why does the one-electron model have degenerate orbitals for all energy levels with identical principal quantum numbers, and why is this unique to only the one-electron model?

I've tried googling and reading textbooks but all I get are how some of the p and s orbitals are degenerate due to their mathematically indistinguishable(?) properties. Something to do with [2, 1, 1] being identical to [1, 1, 2] in terms of energy considerations. Sorry for being slightly incoherent, I read up on this about last week and didn't have time to go about clarifying it until now.

submitted by /u/manyQuestionsToAsk
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If you want to equally divide an n-shaped baked dish between x amount of people, how do you optimize slice size (and shape)?

Posted: 17 Apr 2016 07:52 AM PDT

I do have an inkling that this might be some sort of optimization problem, but my maths fails me beyond that.

So, let us say that we bake a large, rectangular dish of food to divide by x people. We want to minimize the amount of tiny little pieces left after cutting and also want the piece size to be equal for all participants. The slices are rectangular.

If the dish is rectangular (sides A and B) and the number of people to divide it to is even, this is pretty easy. But what if there is, say, 17 people, or any odd or prime number?

Could there be a generalized solution for an n-sided polygon? How about a solution where the slices can also be any one type of polygon? Is this a problem of irreducible complexity or?

submitted by /u/timipeko
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If you were traveling at 99.9% the speed of light, and you fired a gun, would the bullet fly at the speed of light?

Posted: 17 Apr 2016 11:18 AM PDT

As far as I know, if you're moving then you throw an object, that object moves in relation to you. Could this theoretically happen?

submitted by /u/ZaneWuzHere
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Sunday, April 17, 2016

Is the sun soft or hard?

Is the sun soft or hard?


Is the sun soft or hard?

Posted: 16 Apr 2016 06:45 AM PDT

To give an example; if I was flying a spaceship (let's assume it can withstand the extreme conditions), and I wanted to enter the sun, would the ship just sail through or would it crash on the surface?

submitted by /u/Jiji5
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Why are men who have had sex with other men not able to donate blood?

Posted: 17 Apr 2016 12:05 AM PDT

I believe it is against regulation at least in the US.

submitted by /u/thefangster7needsaid
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How did the scientists, in the dawn of chemistry as we know it, knew when they found a new element? How were they sure it wasn't just another compound?

Posted: 16 Apr 2016 07:55 PM PDT

Taking boron as an example: it was discovered in 1808. How did Gay-Lussac and the other scientists who discovered it knew it was a completely new element?

submitted by /u/Lichewitz
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Are earthquakes "connected"?

Posted: 16 Apr 2016 09:13 PM PDT

I've been noticing in the past couple of years that when a medium to large-scale earthquake happens in one part of the earth, another one follows within a week or two in another part of the earth. This makes me think that there is a connection between them... the most recent example being the 7-magnitude quake in Kyushuu, Japan and the 7.8 in Ecuador. If this is true, can someone explain?

submitted by /u/cooperCollins
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Does the discovery of gravitational waves falsify quantum mechanics?

Posted: 16 Apr 2016 09:18 PM PDT

What is the unit of measurement for gravitational waves?

Posted: 16 Apr 2016 02:44 PM PDT

Now that we have found einsteins gravitational waves; I am writing a bit of science fiction which is centered around space-fold/warp technology. I am curious, now that Einsteins gravitational waves have been proven; what is the unit of measurement by which they are measured? Also are these gravitational waves measurable in the electro-magnetic wave-length? I ask, because by this measure, wouldn't "warp" drives use wave-length to measure jumps?

submitted by /u/lordpoee
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Are the electrons within an atom entangled?

Posted: 16 Apr 2016 01:32 PM PDT

Because of Pauli's exclusion principle, two electrons within the same orbital cannot have the same spin, so, this means that by measuring the spin of one electron you automatically know the spin of the second electron. Are the electrons really entangled? Does the same math that is used to describe entanglement describe what's happening here?

submitted by /u/yeahbitchphysics
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Can you use quantum entanglement to get around Heisenberg's uncertainty principle?

Posted: 16 Apr 2016 12:13 PM PDT

Could you not measure the momentum of one entangled particle a and the position of the entangled particle b, then use the momentum of the entangled particle b as the momentum of entangled particle b?

submitted by /u/CitizenWoot
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Could enough rotational energy be imparted to a black hole to rip the singularity apart?

Posted: 16 Apr 2016 08:11 AM PDT

I was just thinking about centrifugal force and I was wondering if enough rotational energy could theoretically be added to a black hole to cause the singularity to be pulled apart and release the mass contained in the black hole.

Is it theoretically possible? If not, what would prevent that from happening?

submitted by /u/rebbsitor
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How strong a gravity could humans adapt to?

Posted: 16 Apr 2016 10:18 AM PDT

For a sustainable society everything else being equal what is the strongest gravity a human world can have? And what would a visit to Earth be like for the inhabitants of this hypothetical world?

submitted by /u/wickedsteve
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What exactly makes a bolide explode in the atmosphere?

Posted: 16 Apr 2016 12:02 PM PDT

Been looking around Wikipedia for an answer to this, but it doesn't explicitly say it so I'm still not sure. Does the bolide contain something in its body that's explosive? Is it just that if it's hot enough, it cracks like wood in a fire? Or is it something pressure-related?

EDIT: I scoured Wikipedia but forgot to do a basic Google search, which I did after I got the bot's message. So Today I Learned it's the air pressure that makes it shatter. Secondary question still applies though.

As a secondary question, Wikipedia's list of meteor air bursts page has a chart that says the (average, I'm assuming) kinetic energy yield during an air burst, for an asteroid 20m in diameter, is 230 kt of TNT equivalent--but the Chelyabinsk meteor, with the same diameter, released double that at 500 kt. What makes the explosion vary like this?

EDIT (same one as before): Also, on the meteorite thread from the FAQ, there was a question that got asked but I don't think got answered. Was it the air burst specifically that caused windows to shatter, or was it "just" the fact that it was making continuous sonic booms, strengthened by the fact that the meteor fell at an angle?

submitted by /u/AKAAkira
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What are some "presentable" nuclear or quantum physics subjects?

Posted: 17 Apr 2016 03:32 AM PDT

Hello,

We have to present a topic to the class in my Modern Physics class. It should be about nuclear physics or quantum physics, yet I am unable to find something interesting that we didn't already learn.

"You will be giving a 16 minute seminar, with a maximum of 2 minutes for additional questions, during class time in May- June. Your presentation will be based on a topic from nuclear physics, or from medical physics, or from quantum physics and will be approved by your teacher beforehand."

What are some interesting yet rather unknown topics that come to your mind?

Thanks.

submitted by /u/klankeser
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Is there any place in the universe, or could we make a place, where EM field doesn't exist ? Are we able to PURGE an EM-Field ?

Posted: 16 Apr 2016 11:47 AM PDT

Is there any difference between mass granted by the Higg's mechanism versus mass granted by the Strong force?

Posted: 16 Apr 2016 09:44 AM PDT

Forgive my terminology, but as I understand it, the Higg's field creates mass for elementary particles, but the vast majority of mass we see is a result of the strong force holding together bundles of quarks and nucleons. How is it that these 2 seemingly different mechanisms result in something that on our scale look like exactly the same thing? Does mass created by the strong force interact with the Higg's field? Does mass created by the Higg's field interact with the curvature of spacetime?

submitted by /u/Camelfoe
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Is a square or a triangle shaped "tower" able to hold a heavier load?

Posted: 16 Apr 2016 12:42 PM PDT

I have noticed that different cell towers (or similar type tower) are sometimes Triangular (3 support pillars) and some are square (4 support pillars). I got into a discussion with a friend as to what the difference was between the two were and if one design can hold more weight than the other. We each have theories on why one is better than the other, but can't find a definitive answer. So I guess my question is, which can hold a heavier load, a square base or a triangle shaped base?

Edit: To be a little more specific,assume they both have the same build cost and amount of material put into it.

submitted by /u/tannerdanger
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What factors determine the "voice" of a crowd in a stadium chanting a player's name?

Posted: 16 Apr 2016 06:59 PM PDT

I'm watching the Capitals VS Flyers game and the Caps goalie has done a great job tonight. In the final seconds, the crowd was cheering "HOLTBY! HOLTBY! HOLTBY!" and it occurred to me that it appeared to be a pretty deep voice.

So does the shape of the stadium/dome affect the tone and pitch of the voice, or is it just an average of all the voices?

submitted by /u/Tnargkiller
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When a helium balloon contracts from the cold, does it loose lift power?

Posted: 16 Apr 2016 06:58 PM PDT

We have been sending off gas filled balloons attached to helium balloons, and we noticed that the helium balloons contracted and seemed to deflate in the cold. Since this space isn't being replaced with any other gas, does the balloon loose any power?

submitted by /u/Zorac877
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Will an object greater mass hit the ground faster than lighter object if they're dropped in still air conditions (no wind etc) and are of the same shape and size?

Posted: 16 Apr 2016 04:28 PM PDT

E.g. Two exactly similar balls with absolutely same size and shape, volume and all other physical properties, except mass are dropped from, say, plane, but with no wind to affect them. Will the heavier ball reach the Earth a bit faster?

submitted by /u/teinekin
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What's the mechanism of pH indicators? Why do they change color?

Posted: 16 Apr 2016 05:31 PM PDT

I understand that the molecule changes because a hydrogen ion is removed or added, changing resonance structures, but I don't see how resonance changes how light interacts with the molecule.

From what I've seen, I've also noticed that more indicators are more red on the acid side, and more blue on the base side. I was wondering, is that just a coincidence or does it mean something?

submitted by /u/minecraftian48
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During El Niño years do the trade winds over southern Atlantic also weakens?

Posted: 16 Apr 2016 07:53 PM PDT

I know that during El niño years the southern Pacific trade winds weakens.

What about the southern Atlantic trade winds? Do they also weaken?

submitted by /u/fellinitheblackcat
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What are the physical/neural mechanisms for keeping track of time?

Posted: 16 Apr 2016 07:03 PM PDT

Saturday, April 16, 2016

How does toothpaste affect the microbial flora of the mouth?

How does toothpaste affect the microbial flora of the mouth?


How does toothpaste affect the microbial flora of the mouth?

Posted: 15 Apr 2016 10:15 AM PDT

Hi! I'm a microbial ecology M.Sc. candidate that works predominantly in soil. In soils, there is quite a bit of evidence that anthropogenic changes to the soil affect the microbial community and it seems (at least from what I read and work on) that this can sometimes severely limit the diversity of microbes to species and genera that are capable of withstanding the changes. For example fertilization can limit the ammonia oxidation community to a small subset of species that are capable of surviving at high ammonia concentrations and make better use of the substrate.

The human microbiome is a pretty interesting subject to me even though my understanding of it is pretty limited. I've always wondered about toothpaste. I'm not sure what sorts of antibacterial properties it has and what exactly it's supposed to be doing to teeth... Does brushing your teeth 1 to 3 times a day cause the microbial community to shift towards species that can resist the perturbation? Could this practice cause us to have higher concentrations of bacteria that have negative effects on our health and hygiene (such as increasing the proportion of bacteria that cause bad breath or tooth decay)? It seems pretty amazing to me that we still follow a practice that has been around since before PCR and as far as I know, we kind of just accept it.

Please enlighten me!

Edit: As I watched the upvotes climb and the comments stay at 0, I thought about the similar scenario with soap. We wipe out most of the microbes every time we wash and let them colonize anew. I remember seeing some evidence that some bacteria metabolize odour-causing chemicals, but that by washing the "bugs" away, we end up stinking when we're no longer "clean". There is anecdotal evidence from a reporter that tried not washing with soap for a while and after a few weeks of applying bacteria (coincidentally the same ones I study in soil), when his skin microbiome had reached some sort of equilibrium (presumably), he stopped stinking.

submitted by /u/GreatAssGoblin
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How did the ancients discover the value/concept of Pi? In what ways was it useful to their lives?

Posted: 15 Apr 2016 04:36 PM PDT

What makes electomagnetic waves able to propagate without a medium and other not other waves??

Posted: 16 Apr 2016 03:50 AM PDT

What two creatures are most closely related genetically, but look the most different physically?

Posted: 15 Apr 2016 10:23 AM PDT

Is there any evidence of two seperate planets orbiting an object in the same path but not colliding?

Posted: 15 Apr 2016 03:23 PM PDT

Are there the same number of Protons as Electrons in the Universe? If so, why?

Posted: 15 Apr 2016 02:39 PM PDT

This article (http://cosmology.berkeley.edu/Education/CosmologyEssays/The_Standard_Cosmology.html) states that Proton creation and Electron creation after the Big Bang occurred on different schedules. As such, there would seem to be no reason for their numbers to be equal. Are they equal and, if so, why?

submitted by /u/dgm42
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What happens when you use ackermann's function with graham's number as it's arguments?

Posted: 15 Apr 2016 03:42 PM PDT

How does nuclear binding energy work and what are it's uses?

Posted: 15 Apr 2016 11:30 AM PDT

Is there a way to do floor and ceiling functions using only 4 operators ( + , - , * , / )?

Posted: 16 Apr 2016 12:49 AM PDT

How do electrostatic forces play a role in accretion and agglomeration of cosmic dust?

Posted: 15 Apr 2016 02:56 PM PDT

This has a few parts to it....

first, how does the charge get attached to the dust?

Second, if like charges repel, and unlike charges attract, how is it that the asymmetry of charges comes about which allows particles to stick together? Shouldn't a similar charging process make it so that the cosmic dust is charged with like charges making it repulsive?

another related bonus question: how are dust bunnies formed?

submitted by /u/portmantoux
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What rare elements are used in modern CPU and GPU designs, and are there viable substitutes?

Posted: 15 Apr 2016 08:54 AM PDT

There has been a lot of talk about things like Indium for transparent semiconductors becoming scarce, but what about the most crucial chips in computing, the CPU and GPU? I know the chips are mostly made from silicon with small amount of dopants, but are these particular dopants rare, and how long could we go if they continue being used at accelerating rates?

Moreover, supposing we wanted to change to a more sustainable alternative, do they exist? Could you make today's high-speed microchips with commonly available elements, or are we basically boned if we run out of certain rare earth metals?

submitted by /u/slugwind
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Do each of our nerves have separate connections to the brain or do signals travel up a common pathway?

Posted: 15 Apr 2016 08:20 AM PDT

For the moment I'm considering our senses of touch, hot, cold...

If the signals merge into some kind of central line then they would have to have some method of telling the brain where they originated. Otherwise, there must be a TON of wiring going up there!

submitted by /u/ace_urban
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How does the stop/start technology work in a modern car and why isn't the radio cut off when it starts again, like when I start an older car?

Posted: 15 Apr 2016 08:16 AM PDT

Does saltwater have a net electrical charge? If so, how would you go about calculating it?

Posted: 15 Apr 2016 02:17 PM PDT

Title

submitted by /u/50Genie
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If most average galaxy groups are discovered to contain supermassive black holes, like the recently measured NGC 1600, would that provide any evidence to contradict our current theories of dark matter being primarily nonbaryonic?

Posted: 15 Apr 2016 10:19 AM PDT

After reading about the recently measured supermassive black hole at the center of NGC 1600, which is considered to be surprising because it contradicts our current theories of such large black holes usually being found in large dense clusters, I wondered if this discovery (or, more accurately, the potential discovery of many more similarly-sized black holes in non-large and non-dense clusters) would have any impact on our current hypotheses that dark matter is likely comprised primarily of nonbaryonic matter. After reviewing the current evidence in favor of nonbaryonic dark matter (i.e., baryonic gas or dust would be visible, the observed abundance of chemical elements, not enough gravitational microlensing, and CMB anistropies showing most matter interacts only through gravitational effects), it seemed to a layman like myself that the potential discovery of supermassive black holes at the heart of most clusters, instead of only at the heart of large dense clusters, would offer evidence to refute these current lines of evidence. But I would appreciate someone pointing out how this would not, in fact, refute the current lines of evidence. Thank you.

submitted by /u/lonefeather
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Why do photons have energy?

Posted: 15 Apr 2016 07:56 AM PDT

Thinking about photons as a particle, they are massless (as in, I assume, they have no rest mass). So by E=mc2, they should have no energy.

The thought that comes to mind (and I've seen this 'explained' with), is that the actual form of that equation is: E2=m2c4+p2c2 Where more energy could come from the momentum of the photon. But isn't momentum defined as the product of the mass and the velocity? Is this different for photons, or is there another reason for their energy?

submitted by /u/BaconWraith
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Why is time not divided into tens?

Posted: 15 Apr 2016 03:48 AM PDT

One day has 24 hours, one hour has 60 minutes and one minute has 60 seconds. This makes it harder to convert a year into seconds. Or for example if you said 2.5 hours had passed it would actually be 2 hours and 30 minutes that has passed. This seems illogical.

In all European countries (as far as I know) we use the metric system which is basically everything divided into tens and makes convertion of meters to centimeters or any other conversion easy.

To me, it seems illogical not having time be divisible by ten. Is it because seconds (or rather centihours?(a hundredth of an hour)) would span such a short time it would be impossible to count?

Even seeing how much of the day has passed would be easier if you said there is 10 hours in 1 day. After 2.5 hours you would know that a quarter of the day has passed. And 2.5 hours would be 2 hours and 5 decihours. Or 2 hours and 50 centihours.

(Edit: fixed spelling errors)

submitted by /u/TheNumber999
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