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Friday, December 28, 2018

Why does string theory require eleven dimensions?

Why does string theory require eleven dimensions?


Why does string theory require eleven dimensions?

Posted: 27 Dec 2018 04:25 PM PST

In 3-phase AC, what is the actual motion of electrons?

Posted: 28 Dec 2018 02:33 AM PST

I understand that AC is electrons "wiggling" rather than flowing.

But what about multiple phases of AC?

Does it simply mean they wiggle faster in the same space of time, or each wiggle is stronger or farther, or are they performing some more complex motion, or is something else happening?

submitted by /u/ten_mile_river
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Why do arctic climates often have days where night is warmer than day?

Posted: 27 Dec 2018 11:34 PM PST

I just looked at the weather for McMurdo Station in Antarctica and Longyearbyen in Svalbard, and this upcoming week has many consecutive days where it is 3C warmer at night. How is this possible?

My guess is that the sun loses much of its influence on the daily weather cycles, and that wind and sea currents become more influential.

submitted by /u/lax_incense
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How does regenerative braking recharge the battery in an electric car or motorcycle?

Posted: 27 Dec 2018 07:26 PM PST

Why does dispersion need to be accounted for even in single mode fiber?

Posted: 28 Dec 2018 03:38 AM PST

Light of different wavelengths travel at different speeds through glass, like a glass fiber. In a single mode fiber there's only one wavelength going through at any given time. Both the transmitter and receiver (should) know the wavelength so why does there need to be dispersion compensation?

submitted by /u/lion342
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What leads to transformer explosions emitting the colors they do? (i.e. green or blue vs red)

Posted: 27 Dec 2018 06:50 PM PST

Here in NYC, the sky was glowing a light bluish color 4 hours after sunset when a transformer blew up in a nearby neighborhood.

submitted by /u/GigaRebyc
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Which is the furthest star we can see with our naked eye? How does that compare with the size of the milky way?

Posted: 27 Dec 2018 07:46 PM PST

Do asteroids that are rich in ferromagnetic materials change trajectory significantly because of the earth's magnetic field?

Posted: 27 Dec 2018 11:08 AM PST

Why does lightning occur when a volcano erupts?

Posted: 27 Dec 2018 05:30 PM PST

Does blood clot when you die?

Posted: 27 Dec 2018 02:30 PM PST

Say you're hunting a deer and you fatally wound it, would the bleeding stop like it normally would, if the wound wasn't fatal?

submitted by /u/wilsonmack13
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How can we tell that we are moving in space?

Posted: 27 Dec 2018 04:50 PM PST

I read that we travel 300 miles a second. That old of course include the sun I would figure. How do we know this. I mean I can understand and see that we know the earth moves around the sun, and I guess I can wrap my head around that we move around the galaxy too... I think I can at least sure but I mean how do we know that we are actually moving?

Further more what tells us that we (the galaxy) is actually moving and not that just everything else is.

Lastly if we are moving, why do we not see evidence of it like we so with comets? Shouldn't sun flares be longer on the side opposite the direction that it is moving too, as well as shorter on the outwardly facing side (the side that is facing into its forward direction?

submitted by /u/Licalottapuss
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How does that brain physically recall memories?

Posted: 27 Dec 2018 08:24 AM PST

Example when we recall a name previously forgotten" what are physical, cellular, and biochemical changes that occur in that instant that allow us to remember?

submitted by /u/Slampig1
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Is it possible to simulate simplest, smallest life form on a molecular level?

Posted: 27 Dec 2018 12:01 PM PST

Its difficult to create simplest life form physically in the lab, are we currently capable of doing it on supercomputers?

submitted by /u/smusamashah
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Is the plane of the Suns orbit around the galactic center the same as the plane of the planets orbit around the Sun ? If so when in the cycle of the earths orbit are we in the front of the Sun's path.

Posted: 27 Dec 2018 12:33 PM PST

Is there a Relationship between LDL Cholesterol and risk of CVD/atherosclerosis?

Posted: 27 Dec 2018 04:39 PM PST

Not sure if this belongs here, and I apologize if it doesn't.

Over the holiday I had a conversation with someone who claimed that they had read some recent medical studies that claims there is no relationship between LDL Cholesterol and CVD (Cardiovascular Diseases) and/or atherosclerosis and that all past studies were wrong in that they were citing a flawed study that proved it. I am very ignorant of this topic so I was unable to respond with any meaningful counter arguments. Another person (second year nursing student) joined the conversation and retorted that there was plenty of evidence for the relationship between LDL-C and CVD.

I was under the impression that the relationship of high LDL-C and CDV was common knowledge and that high levels of LDL-C was bad. I began my own research and found one article that clearly supports the first person's position but was unable to find conclusive evidence for the opposite (that high level of LDL-C contributes to higher risk of CVD).

My two questions are:

1.) Is there any reliable sources (articles, studies, journals, etc) that would support the position that high levels of LDL-C are bad in that they contribute to a higher risk of CVD?

2.) where is the best place for me to research and find these studies on my own besides google scholar.

Thanks.

submitted by /u/Chanchitovilla
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What is the space between the tectonic plates like? Is it hot? Cold? Flooded with water? How big are the divides at their widest points?

Posted: 27 Dec 2018 09:07 AM PST

Is there evidence that other planets undergo plate tectonics similar to earth?

Posted: 27 Dec 2018 02:58 PM PST

Why does ice stick to a metal spoon?

Posted: 27 Dec 2018 11:06 AM PST

What's the difference between glass and crystal?

Posted: 27 Dec 2018 03:21 PM PST

How was the first nucleic acid formed?

Posted: 27 Dec 2018 06:54 AM PST

Hi, I recently read online that the initial experiment about how the first nucleic acid was formed was tampered with (I think it was watson and kirk) where they showed the conditions that were during that time period and tried to recreate that experiment but it didnt show the nucleic acid being formed. Since it is the basis for all evolution I want to ask how do we know or hypothesize how it was formed since all of the later experiments use Watson&Kirk as their starting point

submitted by /u/deadshot92
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How does acid rain causes marble monuments to undergo discoloration?

Posted: 27 Dec 2018 10:24 AM PST

If white marble is calcium carbonate and acid rain is sulphuric and nitric acid, their reaction will give us calcium sulphate and calcium nitrate as products both of which are white in color. Then where is the discoloration coming from. Please explain with equations.

submitted by /u/6inc
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Thursday, December 27, 2018

How does a zygote transcribe its DNA initially given that RNA Polymerase is a protein and has to be transcripted and translated to form? Would it use cytoplasmic egg RNA Polymerase then change to use the zygote RNA polymerase?

How does a zygote transcribe its DNA initially given that RNA Polymerase is a protein and has to be transcripted and translated to form? Would it use cytoplasmic egg RNA Polymerase then change to use the zygote RNA polymerase?


How does a zygote transcribe its DNA initially given that RNA Polymerase is a protein and has to be transcripted and translated to form? Would it use cytoplasmic egg RNA Polymerase then change to use the zygote RNA polymerase?

Posted: 26 Dec 2018 01:53 PM PST

Has the invent of traffic tracking/auto rerouting in modern satnav/mobile phone navigation systems caused a demonstrable difference in traffic levels from say 15 years ago?

Posted: 27 Dec 2018 12:42 AM PST

Is another earthquake less likely to happen after an earthquake?

Posted: 26 Dec 2018 08:12 AM PST

Hello. I live in Catania (Sicily) and we had 2 earthquakes in 2 days. The first one was very weak and short but the other one was quite powerful and it lasted for ~10 seconds (magnitude 4.8 I believe).

I'd think that after an earthquake most of the energy would be released, making another one less likely to happen, though that doesn't seem to be correct as in my case it just got stronger.

I definitely don't want to die crushed by a building, so yeah. Should I expect another one coming soon?

submitted by /u/cckcamel
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What is the actual science behind our estimate of the age of the earth? What is the tolerance and how was it arrived at?

Posted: 26 Dec 2018 10:50 PM PST

Background: I'm a pure mathematics and theoretical physics major so I am very attuned to my side of science, but i'm afraid I am almost completely ignorant about other aspects. (Geology, biology, ecology, paleontology)

I grew up in a Southern Baptist home and was homeschooled up through junior year of high school so although I have tried to actually learn as much science outside of physics as I could, there are still huge gaps left from my parents erroneous beliefs. The biggest one is the age of Earth as they raised me a young-earther. (I'm a staunch atheist now, but would like to be better apologisist for the sciences outside my direct purview.

submitted by /u/TheVicariousVillian
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Why are the blades on wind turbines so long?

Posted: 27 Dec 2018 07:36 AM PST

I have a small understanding of how wind turbines work, but if the blades were shorter wouldn't they spin faster creating more electricity? I know there must be a reason they're so big I just don't understand why

submitted by /u/chesterSteihl69
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Do field lines compress on a quickly moving magnet like air waves on a jet?

Posted: 26 Dec 2018 11:04 AM PST

Can a magnet break the 'magnet' barrier like a plane breaking the sound barrier?

submitted by /u/Nwilde1590
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Does every gene have a promoter and enhancer?

Posted: 26 Dec 2018 10:43 PM PST

What's the bridge between a photon and an electromagnetic wave?

Posted: 26 Dec 2018 03:49 PM PST

In other words, how does one connect the two? Is an EM wave a photon? Is a photon just one wave cycle of an EM wave? If we know the energy of an EM wave could we just divide by hv to get the number of photons?

submitted by /u/ChemAnon2018
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If gravity is the effect of space-time being stretched, wouldn't an object's angular momentum generate gravitational effects?

Posted: 26 Dec 2018 11:51 PM PST

I'm thinking mainly of things like planets, stars, and black holes, and how their angular momentum stretches space-time. I'm wondering if this is an explanation for why most things celestial have prograde orbits.

submitted by /u/_Sunny--
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How does "Plan B" work?

Posted: 26 Dec 2018 01:47 PM PST

During nuclear fission in uranium, what kind of radioactive rays are emitted? Alpha, Beta or Gamma?

Posted: 26 Dec 2018 12:00 PM PST

I have been told that during nuclear fission that uranium releases heat and radioactive rays, but which kind of rays are we talking about?

submitted by /u/nole120
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Before Louis Pasteur discovered diseases were caused by germs, did germophobes or any variation of it exist?

Posted: 26 Dec 2018 05:00 AM PST

How do Catalysts reduce the Activation Energy Needed to start a reaction?

Posted: 26 Dec 2018 09:13 AM PST

Do "carbon neutrality" measurements of a nation include associated ocean territory?

Posted: 26 Dec 2018 09:06 AM PST

I am aware that Bhutan is often quoted as "the world's only carbon sink nation". However I am wondering if this considers the effect of a country's ocean territory.

I know oceans are enormous carbon sinks, especially the southern ocean, so I was wondering if you included ocean then small island nations with high ratios of ocean/land or small nations with a stake in the antarctic land-grab/share might be considered carbon sinks.

I am not challenging Bhutan's status as a carbon sink, I am challenging its status as THE ONLY carbon sink.

submitted by /u/Let-Down
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What exactly is a "vitamin" and what exactly does it do for us?

Posted: 26 Dec 2018 05:54 AM PST

I have always wondered this, and have the basic understanding they are type of organic material? But that's as far as it goes and before I launch myself down a wormhole of coffee and curiosity fueled googling, I wanted to ask for a primer from the smart people in the room.

submitted by /u/genmischief
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How long could you survive being in space unprotected?

Posted: 25 Dec 2018 10:31 PM PST

Sci fi movies have shown people surviving being in space for various amounts of time, from being killed instantly to being able to survive for a fairly long time. How quickly would being in space with just regular clothing actually kill you?

submitted by /u/muffinsandcheesecake
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Why is hydrogen in group 1 on the periodic table instead of a halogen in group 17?

Posted: 25 Dec 2018 10:25 PM PST

It's an extremely reactive nonmetal gas that can form covalent pairs with itself. That sounds like a halogen to me. What am I missing here?

I considered that it's just because it has the one valence electron like the alkali metals, and that's just how the groups are ordered, but then again, boron has 3 valence electrons but is still allowed to sit in group 13 because it shares properties with it's neighbors, so why isn't hydrogen given the same treatment with the halogens?

submitted by /u/farore3
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Wednesday, December 26, 2018

Why do electrons form pairs if they repel each other?

Why do electrons form pairs if they repel each other?


Why do electrons form pairs if they repel each other?

Posted: 25 Dec 2018 06:45 PM PST

What is it about space-time that limits the speed of causality to something finite?

Posted: 25 Dec 2018 06:01 PM PST

The standard answer to why the speed of light is finite usually just boils down to that the speed of causality is finite. Is there a deeper explanation? How does relativity theory calculate this speed?

submitted by /u/yesireallyamthatdumb
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Are there infinite sets of 1-10 that have 4 primes?

Posted: 25 Dec 2018 07:46 AM PST

Question is basically what it says, for example, 1-10 has 2,3,5,7. 2081-2090 has 2081,2083,2087,2089. I kind of view shifting the set (say 7:16) as not counting, but maybe it gives a different result that gives infinite groups of 10 with 4 primes?

submitted by /u/shmeerk
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How is symmetry spontaneously broken in superconductors?

Posted: 26 Dec 2018 05:50 AM PST

I was reading about how spontaneous symmetry breaking occurs in superconductors and how Nambu proposed that by "breaking the symmetry" you give energy to break apart Cooper electron pairs resulting in giving them mass. I don't really get how this occurs in superconductors.

submitted by /u/MammothTriceps
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Can someone explain what Clausius inequality and clausius theorem is?

Posted: 26 Dec 2018 05:34 AM PST

The theorem says that for a system undergoing a cycle dQ/T=0 While the inequality says dQ/T<=0 Can someone clear it out for me?

submitted by /u/alchemink
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Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology

Posted: 26 Dec 2018 07:14 AM PST

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Biology, Chemistry, Neuroscience, Medicine, Psychology

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions.

The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here.

Ask away!

submitted by /u/AutoModerator
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Whats more wasteful..Throwing away plastics and glass or wasting the water to clean them for recycling?

Posted: 25 Dec 2018 05:48 PM PST

Do bonobos have any pair bonding, and do males invest in children?

Posted: 25 Dec 2018 07:47 AM PST

Do bonobos have any pair bonding, and do males invest in children? I know they aren't monogamous.

submitted by /u/OXIOXIOXI
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If you donate blood with low levels of cholestorol into a body with previously high levels of cholesterol, would there be any discernible effects?

Posted: 25 Dec 2018 06:30 AM PST

Do all transistors, regardless of their size, produce the same amount of heat?

Posted: 25 Dec 2018 03:38 PM PST

A professor of mine said that all transistors produce the same amount of heat regardless of their size. In other words, if you have two transistors and one is really small (a few atoms) and the other is large (a couple of milimeters), they would produce the same amount of heat. They also stated that this was the reason why there is a limit to how much transistors can be put on a single chip (because it would melt).

Is that true?

submitted by /u/StefanDimeski90
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Did people who existed before electricity was a widespread thing experience the shocks you might get randomly when touching metal? What did they think it was? How do these shocks happen?

Posted: 25 Dec 2018 01:07 PM PST

How do we know that our Lagrangian is correct other than just because it works?

Posted: 25 Dec 2018 05:55 PM PST

I'm trying to make my way through the course on classical mechanics and while I think I'm fine with understanding what is action and how it leads to E-L equations IF we already have Lagrangian given to us. By given I mean we just assume that it is in a form of L=T-V because it kinda appears to work. I do know that the most commonly presented to me Lagrangian L=T-V holds only in classical mechanics, but I also know that L can be written in different forms to make it usable to work with relativistic physics and also EM fields afaik, so the general idea of Lagrangian can reach much further than just classical mechanics. I have no problem with seeing how it can make descriptions of complicated system much easier and how much freedom in choosing coordinates suitable for different problem symmetries it gives. Yet still all of this doesn't explain what is Lagrangian other than that it's there because it works. It's like saying something along the lines of "it is a function for which action is the smallest and therefore it meets the requirements of least action principle, which can give us CORRECT equation of motion". The longer I try to understand this, the more I fell like there is virtually no reason for Lagrangian to be in any specific form, for example L=T-V for classical mechanics, other than because it works. It seems to me that CORRECT trajectories define Lagrangian, and not the other way around. Function is Lagrangian if it gives us the correct answer... but you have to find another way of verifying that answer. For example going back to Newtonian physics for classical problems, if it gives us the same answer then our function is in fact Lagrangian. We have some tools(action, least action principle and whole calculus), we have some objects which behave the way they please to, taking into consideration vastly different kind of effects and interactions depending what field we currently study. Then we assume that least action principle holds and there must exists some function L which can give us equation of motion based on said principle. Then we notice that for our specific kind of problem, Lagrangian in a specific form tend to work, so we assume it is the correct form and use it to other similar problems?

Am I missing something crucial and fundamental here? Is there any more general property which function must have to be considered Lagrangian other than 'just work'?

submitted by /u/Zychuu
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Physical meaning of matching output impedance to headphone impedance?

Posted: 25 Dec 2018 04:49 PM PST

I've repeatedly read that you want an AMP's output impedance to be less than 1/8th the impedance of the headphones connected to it. I don't understand the physical considerations behind this.

Impedance is just the complex ratio between AC voltage and current passing through an element in the circuit. Thus, it measures how much voltage is required to get a current flowing (magnitude) and the phase between these two. However, in all the recommendations I've seen, only the magnitude is considered.

So we start with an AMP of, say, 1 Ohm resistance. Out of it comes a voltage and current that goes straight to the headphones. The headphones also have a given resistance, say 10 Ohm. But from the headphones's perspective, it only cares whether the signal going into it has the right amount of voltage and current. Why does the AMP's resistance matter here? The AMP will take a source of power and produce a suitable current and voltage (which is what the headphones care about), why does it matter what its resistance is?

submitted by /u/quantinuum
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How accurately can we send large objects from the orbit back to earth? with a 100km2 margin of error or..?

Posted: 25 Dec 2018 07:05 AM PST

Double Split Experiment: Would you still get an interference pattern with macroscopic objects?

Posted: 25 Dec 2018 08:31 AM PST

What would happen if you scaled everything up? For example: instead of firing photons at a small plate with 2 small slits, you go to outer space and launch bowling balls at a giant plate with 2 giant slits.

submitted by /u/Jamessherman
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Are the 'I am not a robot' puzzles for website verification used to train robots?

Posted: 25 Dec 2018 05:10 AM PST

If yes, isn't that a problem? If no, why not? (Seems like a great resource for machine learning)

submitted by /u/swift_air
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How does ABE fermentation work?

Posted: 25 Dec 2018 10:11 AM PST

Hi! I'm studying ABE fermentation, a process that perduces acetone, butanol and ethanol from glucose. it consists of 4 main steps. glycolysis, chain elongation, acidogenesis and solvengenesis. I understand glycosis, but the other steps are lacking in good internet resources. would some please explain these steps? Just a general description of enzymes and reactions would be great, but references for detailed mechanisms would be even greater. thanks in advanced!

submitted by /u/Springo1808
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How are price-inelastic markets caused and do these markets and their condtions benefit or harm anyone?

Posted: 25 Dec 2018 05:52 AM PST

Tuesday, December 25, 2018

Why do dogs tilt their heads when curious / confused?

Why do dogs tilt their heads when curious / confused?


Why do dogs tilt their heads when curious / confused?

Posted: 24 Dec 2018 09:27 PM PST

Can the speed of light be theoretically calculated using quantum mechanics?

Posted: 24 Dec 2018 08:43 PM PST

I know the speed of light can be accurately predicted from Maxwell's equations, is there a mathematical way to arrive at the speed of light another way? Can you do it using quantum mechanics?

submitted by /u/yesireallyamthatdumb
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How do we know the age of the universe?

Posted: 24 Dec 2018 09:01 PM PST

And due to time dilation, does that mean that some parts of the universe are "younger" than others?

submitted by /u/AtLeastIHaveJob
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Are there any animals that don’t fit easily into a group (mammals, birds, etc)?

Posted: 24 Dec 2018 07:30 PM PST

Like a mammal that lays eggs or a bird that's cold blooded? Obviously that's pretty extreme. But are there any animals whose group is debated?

I find it kinda of amazing that in the process of evolution and natural selection, these groups would be so distinct and animals fit so well in them.

submitted by /u/ChuckSRQ
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How does luminosity scale with human perception of brightness?

Posted: 24 Dec 2018 10:17 PM PST

Bear with me; I'm struggling with the terms involved. I can find some information on this question concerning the use of apparent magnitude in astronomy. But I'm having a hard time comparing apparent (and absolute) magnitudes with SI units for luminosity and such.

Say I step into a closed room with a single light source that's a fixed distance from my eye. The light initially appears at the brightness of a "typical" candle. (So that would be one candela? which is 12.57 lumens?) I turn down the brightness until the light is JUST at my limit of perception. How many lumens is it now?

I guess we need to define a distance between the candle and the eye, so let's say 1 meter? I guess the alternative approach here would be to keep the brightness (luminance?) constant and move the candle further away until I can't quite see it. I found an article saying this distance is something like 2.5 km, but I didn't quite follow how they got there and I can't piece together how that relates to the "decrease the brightness" approach.

Ultimately it's about the number of photons hitting your eye, so distance means less flux. I get that much very well. There's just some link in the chain that I'm getting lost here as I've never worked with these units much.

(And yes, I'm specifically interested in a human eye. I'm aware that these units "filter" light wavelengths so they are weighted based on human perception.)

submitted by /u/jofwu
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Do we know exactly what the atmosphere was composed of when cyanobacteria producing oxygen 2.7-2.8bya?

Posted: 24 Dec 2018 08:58 PM PST

What is the minimum velocity an electron needs to escape through a vacuum after entering the conduction band of the metal electrode?

Posted: 24 Dec 2018 12:05 PM PST

Why does fish decay faster (and smellier) than meat?

Posted: 24 Dec 2018 01:06 AM PST

It looks like fish ---and i don't mean just zoological Fish, but seafood, sea dwellers in general, including mollusks, shrimps, urchins etc--- rots a lot sooner than land animals flesh.

It is as if the bacteria responsible of the decay in the dry find, in anything that has grown in water, their absolute favourite food.

Is there a reason for this?

submitted by /u/itsmemarcot
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Have any species followed an evolutionary path like cetaceans, only to revert to land-dwelling?

Posted: 23 Dec 2018 11:00 PM PST