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Sunday, November 26, 2017

What is the velocity of the edge of a bubble as it is "popping"?

What is the velocity of the edge of a bubble as it is "popping"?

What is the velocity of the edge of a bubble as it is "popping"?

Posted: 25 Nov 2017 02:01 PM PST

Take a bubble - soap/water, milk or otherwise - and initiate a "pop" from a single point on the surface. What would be the velocity of the bursting edge, as it propagates away from the initiation point?

Here is a video of some bursting bubbles in slow-motion. Notice that the bursting edge recedes from the initiation point; the intact surface remains unaffected until the bursting edge reaches it.

For simplicity, assume a perfect bubble:

  • Perfectly spherical
  • Evenly distributed surface
  • No external forces (i.e. gravity, which would cause deformation and pooling of the medium)
  • "Pop" or burst initiated from a single point on the surface

It seems intuitive that the upper limit would be the speed of sound for whatever medium the bubble was made from, because the speed of sound would be the physical limit that the information could be passed along that the bubble was popping. But I'm unsure what role the pressure differential might play - if any at all.

submitted by /u/rockitman12
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Why are non-steroidal anti-inflammatory drugs (NSAIDs) bad for inflammatory related diseases like ulcerative colitis? Why don't they help reduce the inflammation? Aren't they anti-inflammatory?

Posted: 25 Nov 2017 07:31 PM PST

How does sleeping work? I close my eyes and go unconscious. How does brain do that?

Posted: 26 Nov 2017 01:30 AM PST

How do we know the earths core is iron?

Posted: 26 Nov 2017 01:42 AM PST

In UV-Visible spectroscopy, why aren't the absorption bands infinitely thin, since the energy for each transition is very well-defined?

Posted: 26 Nov 2017 07:11 AM PST

What I mean is: why there are bands that cover a certain range in nanometers, instead of just the precise energy that is compatible with the related transition? I am aware that some transitions are affected by loss of degeneracy, like in complexes that are affected by Jahn-Teller distortion. But every absorption I see consist of bands of finite width. Why is that? The same question extends to infrared spectroscopy, with the transmittance bands.

submitted by /u/Lichewitz
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If there was a perfectly symmetrical circular spinning top spun perfectly horizontal on a frictionless platform, would it continue forever since air resistance wouldn’t be able to “grasp” on the top since there are no deformations on it?

Posted: 25 Nov 2017 08:43 PM PST

In spacetime continuum, why are we only able to move forwards in time, when we can move in any direction in space?

Posted: 26 Nov 2017 12:14 AM PST

Why doesn't the glass found within fiber optics break/shatter when the cord is bent?

Posted: 26 Nov 2017 12:52 AM PST

Glass is rigid and brittle, so how is it that you can bend it without it breaking (at least to some degree)?

submitted by /u/Javelin901
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Does light near earth experience the same acceleration due to gravity as a dropped object?

Posted: 26 Nov 2017 12:01 AM PST

To my best understanding, gravity is curvature in spacetime due to mass. What we experience as an acceleration of 9.8 m/s2 is actually just us trying to travel in a straight line through spacetime, which is warped for us mostly due to the earth's mass.

When a black hole warps spacetime enough, light does not escape.

If I fire a bullet out of a gun perpendicular to the earth, it immediately begins accelerating towards the earth's center at 9.8 m/s2, but because of its high velocity it seems to shoot mostly straight. Only over long distances do we notice that acceleration, and a bullet dropped from the height of the gun would hit the ground at the same time as the bullet fired from the gun.

So my question is, does light leaving a source near earth accelerate toward the planet at 9.8 m/s2 initially? It obviously moves so quickly away that the earth's gravity rapidly loses its effect, but does that curvature of spacetime also apply to light (and other electromagnetic radiation) near the earth?

submitted by /u/yellowboat
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Are there materials that conduct electricity but not heat? If so, what are they?

Posted: 26 Nov 2017 02:11 AM PST

How do we know what the Milky Way looks like?

Posted: 26 Nov 2017 02:16 AM PST

Since we are in the Milky Way galaxy, and it is not yet conceivable for us to send any object outside of it for observation, how do we know the shape and composition of our galaxy? Further, why does the Milky Way only take up one strip of the visible sky?

submitted by /u/alexjowski
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What was the temperature of the Moon's surface when Neil Armstrong first stepped foot on the Moon?

Posted: 25 Nov 2017 11:48 PM PST

Why does fire need oxygen, what can it do that other gasses can’t?

Posted: 25 Nov 2017 09:33 PM PST

Why isn't the ISS spun for "gravity"?

Posted: 25 Nov 2017 10:31 PM PST

What qualities of quantum fields account for their differences?

Posted: 26 Nov 2017 07:05 AM PST

My understanding of quantum field theory is that all particles are now seen to be disturbances in a field - the electron field, the electromagnetic field (photon), the gluon field, and so on. To me this sounds like saying that everything is made of one kind of stuff: a field. But the way these fields behave seem very different: one is influenced by massive bodies, one is influenced by charged particles, disturbances in one produces one kind of particle, another produces a very different kind of particle. But isn't a "field" just a number assigned to every point in space? What qualities do fields have that produce such different behaviors? How can a field be said to be different than another field, other than its strength at a given point in space?

submitted by /u/harumphfrog
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Why do "small" changes of temperatures caused by climate change (0-2° C) cause such drastic effects?

Posted: 26 Nov 2017 03:01 AM PST

I am not a climate change denier, I've just been too scared to ask this question for quite a long time --- why do what I would consider "small" changes of the temperature of the earth cause things like the melting of glaciers in Antarctica?

submitted by /u/RealShigeruMeeyamoto
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What causes the muscle aches when a person has the flu?

Posted: 26 Nov 2017 12:20 AM PST

And, are there useful remedies that can treat the cause instead of just painkillers?

submitted by /u/BotiaDario
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Why is it that dilute sulfuric acid is more corrosive than its concentrated counterpart?

Posted: 25 Nov 2017 10:14 PM PST

I was talking with an industrial chemist and he brought up the fact that 99% sulfuric acid will do little damage to you relative to a more diluted solution. His reasoning was that there need to be water molecules in the solution to be converted to hydronium which then cause damage. If that's true, why is it that hydronium is the one causing damage to a person's skin/body and not sulfuric acid when they have pKa values of -1.7 and -3, respectively? Why can't sulfuric acid directly protonate the body's fats/proteins/etc which then causes visible damages and burns?

submitted by /u/VeraMar
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[Biology] Why do bananas have those shiny crystals on them? What are they?

Posted: 25 Nov 2017 11:19 PM PST

How do Scientists derive formulas and constants?

Posted: 25 Nov 2017 04:04 PM PST

For example how did Newton know the Force is equal an objects mass times it's acceleration (F=ma)? And how are constants found (like G which is 6.67x10-11 )? Thank you!

submitted by /u/IanCarteriDubbbz
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What are the origins or predicted origins of gold and silver on planet Earth?

Posted: 25 Nov 2017 07:29 PM PST

Could earth’s GPS satellite network be used on the moon for telemetry purposes?

Posted: 25 Nov 2017 08:27 PM PST

Is the signal strong enough?
Are the angular changes drastic enough for an antenna to pinpoint location?

submitted by /u/mikebellman
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Saturday, November 25, 2017

What is the body's conversion efficiency of energy stored in food to energy stored in fat, or energy available to do work with?

What is the body's conversion efficiency of energy stored in food to energy stored in fat, or energy available to do work with?

What is the body's conversion efficiency of energy stored in food to energy stored in fat, or energy available to do work with?

Posted: 25 Nov 2017 01:08 AM PST

For example, if I eat 1000 calories of sugar:

  • How many calories will be stored in fat (assuming none of the calories are used for exercise etc).
  • How many calories are available to perform work with (after the body has converted the sugar to ATP, etc). The assumption is that the conversion process from Sugar --> X --> ATP --> ? is not 100% efficient.
  • How do the above numbers differ for different sources of energy. For example does eating 1000 cal of fat result in the same number of calories available for work as eating 1000 cal of sugar?

Bonus question:

  • How efficient is the body in converting the energy stored in fat to energy available for work (e.g. ATP)

Note: I am not a biologist, from my understanding ATP is the last form of energy muscles use, albeit I could be wrong.

submitted by /u/YbgOuuXkAe
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Does boiling water in a low pressure atmosphere still kill pathogens?

Posted: 24 Nov 2017 09:44 AM PST

Reducing the atmospheric pressure will reduce the boiling temperature of water, so will boiling in low pressure still kill pathogens in the water?

submitted by /u/xzez
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At what point does atmospheric friction from high speeds negate wind chill effects?

Posted: 24 Nov 2017 07:30 PM PST

What distance from the centre of the earth is an object's potential energy the greatest?

Posted: 24 Nov 2017 11:19 PM PST

As you move a rock further away from the centre of the earth you are increasing its potential energy. If I pick up a rock off of the ground and move it 10 feet up I've just added energy to the system.

Now as you get further from the earth, the gravitational pull weakens by the a factor of 1/(distance)2.

At what point is the rock at the sweet spot where it's potential energy is the greatest it can possibly be and moving further from the earth will reduce potential energy at that point? At what distance does the potential energy become near zero and the rock becomes "weightless?"

submitted by /u/Invrlose
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Particles in Space.. is Space a gas?

Posted: 24 Nov 2017 06:12 PM PST

Matter, in the form of a gas is when "the atoms or molecules in gases are more widely spaced than in solids or liquids and suffer only occasional collisions with one another."

On sea level, one cubic cm of air has about 30 quintillion particles. Space, although often said not to, contains more than nothing. In our solar system, about there are about 30 particles per cubic centimeter. Can someone explain what these particles are?

Considering how far apart the particles in our solar system are spaced from each other, would they be considered a gas? If not, what are they? Are these particles anything? What thing are they? What type of thing?

Considering any of these question are a yes, would the Space we know be considered a mixture?

submitted by /u/ztamm
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Is it possible to study fields in space rather than excitations of those fields?

Posted: 25 Nov 2017 03:02 AM PST

I was wondering if it is even theoretically possible if we can directly study and measure quantum fields that 'make' subatomic particles like the electron field. Rather than study the electron itself? Thanks in advance for the answers!

submitted by /u/JackTalle
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Why can't we make pacemakers that can withstand magnetic fields?

Posted: 25 Nov 2017 04:32 AM PST

The pacemaker sign is often found near strong magnetic fields. What's blocking us from making them non-sensitive to magnetic fields?

submitted by /u/Helmarche
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If calcium is a metal, can it be used for things like electric circuits? Can it be smithed?

Posted: 24 Nov 2017 08:50 PM PST

I just found out it was a metal.

submitted by /u/ten_mile_river
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Does the magnus effect still work underwater?

Posted: 25 Nov 2017 03:13 AM PST

Scramjets and Entropy - The reason for thrust?

Posted: 24 Nov 2017 06:23 PM PST

I have taken Thermodynamics I and II in college. I was reading through my textbook and it said that there is a velocity drop in a supersonic flow stream when a heat transfer to that system occurs. If this is the case, how does it produce thrust?

submitted by /u/Fuck__living
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What happened to the Global Cooling scare of the 1980's?

Posted: 24 Nov 2017 09:13 AM PST

Not that I don't believe in global warming or anything, but im just generally curious

submitted by /u/Lendesnia
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How do satellites survive in the thermoshere when they should melt?

Posted: 24 Nov 2017 09:06 PM PST

By what mechanism does the brain keep time?

Posted: 24 Nov 2017 02:55 PM PST

In every time-measuring device we have, we need mechanical parts that follow a certain rhythm to keep time, so wouldn't the brain also require some physical mechanism in order to perceive time? If so, how does that mechanism work?

submitted by /u/Tendy777
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Do we know how many tons of CFC are in the atmosphere?

Posted: 24 Nov 2017 08:53 PM PST

A question about the relativity of velocity?

Posted: 25 Nov 2017 06:17 AM PST

If all movement is relative to some other reference point, then we could say that we are moving at near light speed compared to a particle in an accelerator. Instead of the particle coming towards us, we would be going towards the stationary particles at near light speed.

If this is true, then why aren't we moving forward in time more slowly compared to the particles? According to the theory, objects that move faster in space experience time more slowly compared to other objects. In other words, time moves faster for slower objects.

If anyone has some knowledge to share on this please do so because it is something that has been bugging me for a while now.

submitted by /u/_Haxington_
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What's to stop a spinning object surpassing the speed of light, if large enough?

Posted: 24 Nov 2017 06:15 PM PST

Let's say you had a giant compass needle spinning in space.

Diameter of the needle = 95,426,903.18 metres

Spin circumference = 299,792,458 metres (the distance light travels per second).

If it were to spin at >60rpm the ends of the needle would (on paper) surpass the speed of light. Can anybody explain what would actually happen? Would the needle be forced to bend, regardless of its material?

submitted by /u/Zombreeez
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What's the state of current lithium-ion batteries and what improvements can we expect in for batteries in general in the short term?

Posted: 24 Nov 2017 02:59 PM PST

Question from my 4 year old sister, do other animals also get "Boogers"?

Posted: 24 Nov 2017 07:02 AM PST

I was telling my sister that she shouldn't pick her nose in public, and somehow she asked me if our dog also couldn't. I told her that animals don't get them. She asked why and I had no idea, in fact I didn't even know if me saying that they don't get them was accurate.

It's my understanding that "boogies" are dried muccus. When something irritates the lining of your nose, like dust, or powder, that muccus stops it. So, does the differing nasal cavity shape on other animals stop them from getting them? Do other animals lack that same muccus?

submitted by /u/SomecallmeMichelle
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How do we clear out dust/debris/lint that gets into our lungs from breathing?

Posted: 24 Nov 2017 02:51 PM PST

As the question states, clearly we breathe in minute particles of dust everywhere we go that must build up over time. Is it all captured by the cilia lining our respiratory tract? But even if they were caught on the way down, there is no way of clearing it unless it's in the nose so how come after decades of living people don't have to clean out their lungs like they would a dusty old room?

submitted by /u/synapgorithm
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How does the brain produce chemicals like dopamine, serotonin, etc?

Posted: 24 Nov 2017 06:00 PM PST
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Friday, November 24, 2017

I’ve read that when caterpillars are in their cocoons, they dissolve completely into goo; no original parts survive in the butterfly. How is the butterfly made from the goo? Is there an embryo that grows and uses the goo like a yolk sac? Or does the goo somehow arrange itself into new body parts?

I’ve read that when caterpillars are in their cocoons, they dissolve completely into goo; no original parts survive in the butterfly. How is the butterfly made from the goo? Is there an embryo that grows and uses the goo like a yolk sac? Or does the goo somehow arrange itself into new body parts?

I’ve read that when caterpillars are in their cocoons, they dissolve completely into goo; no original parts survive in the butterfly. How is the butterfly made from the goo? Is there an embryo that grows and uses the goo like a yolk sac? Or does the goo somehow arrange itself into new body parts?

Posted: 23 Nov 2017 06:52 PM PST

If tooth decay is just caused by the bacteria feeding and producing acid, would a person that just used listerine have the same dental health as a person that brushed without flossing?

Posted: 24 Nov 2017 04:00 AM PST

How sustainable is our landfill trash disposal model in the US? What's the latest in trash tech?

Posted: 24 Nov 2017 06:08 AM PST

How are isotopes used in nuclear physics Experiments isolated?

Posted: 24 Nov 2017 12:59 AM PST

From what I know for heavy species like uranium the preferred method is gas centrifuge but it is extremely expensive.

Is the same method used for lighter species such as calcium-48?

submitted by /u/electric_ionland
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My doctor says that chemotherapy works by specifically targeting rapidly-dividing cells, which is how it works to fight cancer and also why it has the side effects that it does. But how does it “know” which cells are rapidly dividing? And how rapidly is “rapidly”?

Posted: 24 Nov 2017 04:53 AM PST

How mixable are different types of plastic? Like PET and HDPE?

Posted: 24 Nov 2017 03:13 AM PST

What makes a laser shine in a straight line?

Posted: 24 Nov 2017 02:30 AM PST

If you shine a laser into a screen or wall you see a round dot and nothing else around. I surely know that the laser can be very coherent spatially and temporally, but shouldn't in that case behave like a point source and emit in all directions as it comes from a small aperture? (I'm basing my argument in Huygen principle)

Is the focus just a game of lenses at the aperture of the laser or I am not understanding something?

submitted by /u/MaoGo
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Can animals understand human body language like laughing or smiling?

Posted: 24 Nov 2017 03:35 AM PST

If was looking at a monkey while laughing, would the monkey know it was causing positive emotions and continue to do so?

submitted by /u/tthatoneguyy
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How are the triple(or more) parachutes commonly seen on capsules returning from space kept apart?

Posted: 24 Nov 2017 01:05 AM PST

Judging by the direction of force by the cord, shouldn't they be pulled together?

submitted by /u/DirectorOfStruts
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How are the needles for Atomic Force Microscopes made, and how can the tip be smaller than the atoms they are manipulating? What are their limitations?

Posted: 24 Nov 2017 06:11 AM PST

Could an electric vehicle stand a chance in a racing event?

Posted: 23 Nov 2017 02:00 PM PST

Telsa released their new roadster just a bit ago, which is a very powerful car, and completely electric. Would an electric vehicle have any benefits in a race? Fuel efficiency or decreasing the weight of the car maybe?

submitted by /u/ethanpo2
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If there is an ocean below the ice surface of Europa, is the ice shell buoyant? Geologically supported? Or is it kept in place by the distribution of gravity?

Posted: 23 Nov 2017 11:55 AM PST

In other words, how does the solid surface exist with a liquid layer beneath it? Forgive my ignorance if I'm missing any obvious answers to this :D

submitted by /u/olafur98
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Lithium batteries are being developed to power cars in response to the decline in fossil fuels, but will lithium eventually run out as well?

Posted: 24 Nov 2017 03:22 AM PST

There's a huge push for more sustainable sources of energy because we're running out of fossil fuels, but are lithuim ion batteries that sustainable if the amount of lithium on earth is limited too?

Are rechargable batteries truly a renewable source of energy or is it just an alternative to pass the time?

What are we gonna do if/when lithium runs out?

submitted by /u/mangostarfish
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How to calculate eigenvalues in the Kirchhoff's thin plate model?

Posted: 23 Nov 2017 03:53 PM PST

I guess this could be either physics or mathematics, but I'll mark it as physics. I've been studying the acoustic properties of coins as a personal hobby related to coin collecting. I found this fascinating article by a French professor at the Bank of France about how to determine if a coin is genuine or counterfeit. This methodology is superb and I even tested it with the type of coin used in the paper with an app called spectroid, and the frequencies match up perfectly. However, the calculations in his paper only relate to a specific type of coin with a specific composition.

I'm creating a spreadsheet to allow me to enter a coin's properties to recreate this method for any coin. The formula is pretty straightforward, you just need three parts to determine a given frequency, its shape factor (calculated with the thickness and radius), the metal factor (calculated with the density, Young's modulus, and Poisson's ratio), and the eigenvalue. I figured how to do the shape and metal factors, but I'm stumped by the last part which involves eigenvalues for a free, circular plate. That's an area of math well over my head. If anyone has any background in this subject, could you take a moment and look at Table 3 and explain how I could solve the eigenvalues for λ 2,0 , λ 0,1 , and λ 3,0? The author stated that it involved Bessel function of some kind but that wasn't enough to help me figure out on recreating the values.

submitted by /u/alphabetcereal
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Since the event at CERN that proved the existence of Higgs bosons/Higgs field, can we now see this event happen regularly now we know ‘where’ to look?

Posted: 23 Nov 2017 06:28 PM PST

How did we get solid matter from light? How did Photons and Electrons create solid matter in the early ages of the universe when everything was insanely hot?

Posted: 23 Nov 2017 12:52 PM PST

Pretty self explainatory, but Ive struggled to find answers on google/quora. Anything helps.

submitted by /u/GodelianLeviathan
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Is there anywhere other than Earth in the Solar system where you could see a total solar eclipse and/or total lunar eclipse equivalent?

Posted: 23 Nov 2017 09:14 AM PST

By lunar eclipse equivalent, I mean when a planet or moon is directly between the sun and another moon.

submitted by /u/Gentlemanchaos
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Why does turning on an electric blender in the kitchen cause my HD antenna signal to go out in a different room?

Posted: 23 Nov 2017 10:37 AM PST

Can the human body survive breathing pure oxygen at lower pressures?

Posted: 23 Nov 2017 12:04 PM PST

I know that pure oxygen is poisonous at atmospheric pressure, but wasn't sure about the question in the title. I'm reading the new Artemis book about the moon colony - the book explains they breathe pure oxygen at a lower pressure and I wasn't sure if it was true, and if it is true, what the difference is that allows people to be fine in this situation.

Thanks!

submitted by /u/jamnjustin
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How do we know the earth’s core is super hot and why is it so?

Posted: 23 Nov 2017 10:27 AM PST

Also, do other planets have super hot cores as well?

submitted by /u/mninml
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