Questions tagged [biology]
Questions about biology are OFF TOPIC and should be asked on the Biology Stack Exchange. However, questions about biology in the context of physics (e.g., biophysics) can be on topic here if the primary concern is physics.
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Can the human eye see the images of 300 nm light on a screen through a diffraction grating?
In my textbook there is a question as follows:
A diffraction grating with 200 lines per mm is placed between a monochromatic light source and a screen. The distance from the grating to the screen is 2....
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Why does blowing a whistle in someone's ear damage it more than blowing directly in their ear? Won't the whistle reduce overall energy?
If I blow really hard from a whistle near someone's ear, it'll hurt a lot. But if I blow directly at a person's ear, it won't hurt nearly as much. But shouldn't the whistle (or any other obstruction) ...
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How long will oxygen last in a $3\times 3\times 3 $ meter room for one person? [closed]
Let's assume that the windows and doors are tightly closed.
How can I calculate at what moment I will feel a lack of oxygen and my well-being will worsen?
Can one person completely consume all the ...
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How was the structure of DNA deduced using X-ray crystallography
The determination of DNA's double helix structure by Watson, Crick, and co-workers using X-ray crystallography is a well-known milestone in the development of biology. My question is, what was the ...
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Are human eyes interferometers?
It seems like 2 eyes is enough “wetware” to do interferometry inside brain. Can you definitely see some reason why this could not be happening, or some way to test if it does happen?
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Does the human brain use random number generators? [duplicate]
Neurons fire depending on the impulses they get from other neurons. This seems to be 'deterministic'. However, sometimes it might be useful to use random processes instead. Does the human brain have ...
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Generation of order on the Earth
I learnt in a course on Biological Physics that it is possible to generate order without violating the second law of thermodynamics. This can be done if "high quality" energy is delivered to ...
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The sun's neutrinos and the brain [closed]
Is it possible for the sun's neutrinos to be detectable biologicaly . Or what is the simplest way for a experimenter to detect neutrinos externally?
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Question about the 2nd law of thermo
In some ways the 2nd law of thermodynamics appears to be violated by the creation of large molecules like proteins.
The reason this seems to be a violation is because individual atoms become much more ...
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How is abiogenesis not a violation of the second law of thermodynamics?
Randomly traveling molecules plus random changes in temperature, pressure, acidity, electric charges equals a cell. That is a decrease in entropy.
How does that not violate second law of ...
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What happens, if amino acids are exposed to extreme heat?
What will happen to amino acids if they are exposed to extremely high temperature such as the temperature of the Sun? Do the amino acids become more simple structures?
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Which electrons kill you during electrocution?
I understand that there are three velocities in play in a circuit (I haven't studied Physics past high school so give me some rope)
v1: the velocity by which the electrical field propagates through ...
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Out running a bear
I was going to ask this in wilderness but I’m pretty sure we’ll need some math to find out the real answer.
They say you can’t out run a grizzly bear because they run about 35 mph. While the average ...
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What's the reason that it requires less effort to walk against an escalator (to stay stationary) than walking up stairs?
I had this discussion with my relatives about the reason why it feels like you spend less energy on a step machine in the gym (basically an escalator that goes down), than it is to move up some stairs....
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In theory, how fast could I possibly serve in a game of ping-pong?
A tennis player can serve in a more or less straight line from their racket to the service box on the other side of the net: there's a direct line of sight. That means that there's no inherent limit ...
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Are bacterial flagella the most efficient propulsion system at the microscopic scale?
Bacterial flagella can be regarded as microscopic propellers. The rotor is a long, helical protein filament powered by proton gradient. When protons pass through the gap between the rotor and stator, ...
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The *compressive* strength of spider silk
There's plenty of information about the tensile strength, density, energy density, ductility, etc. of spider silk.
However, I personally cannot find any figures in regards to the compressive strength ...
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Is possible to "isolate" some audio frequency? [closed]
I want to know if is possible to "isolate" some audio frequency for certain human that only this human can hear this "frequency spectrum", some animals can hear certain frequencies ...
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Can Low-Freq sound wave with High-Amplitude destroys human ear?
Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. So that's mean human unable to hear 1 Hz frequency sounds since it's far under 20 Hz.
At detectable frequency of human like ...
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How do retinal cones see color when the cones pickup photons and not waves?
I am wondering how cones (photoreceptors in the retina) can see color if colors are wavelengths but cones send signals when they absorb photons. Maybe by using the energy level (or only being ...
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If we know information existed when life first began on earth, then can’t we surmise that information existed prior to earth life? [closed]
If true, then wouldn’t information have been created when the universe was created?
In other words, if information existed from the start of the universe, then it’s possible that information can not ...
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Energy and force relation
So in simple machine we apple less force with more displacement to exert same energy as the load need so if energy is related to tiredness i.e. more energy you lose more tired you feel but by applying ...
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Wouldn't our own EM emissions be good the places to look for signs of intelligent life?
I read that only a narrow band of radio waves are reserved for astronomical observation, and humans emit all sorts of electromagnetic waves, which leads to my question:
Could there be signals of ...
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Do photosynthesis and respiration violate the law of conservation of energy?
I don't know, if it's a physics question, biology or chemistry question but anyways here it is:
I have been taught that for making one molecule of glucose in photosynthesis 18 ATP molecules are used ...
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At what rate does the human body heat itself?
The human body heats itself at some rate, because of this, I'm trying to add a forcing function to the differential equation known as Newtons law of cooling: $Q = hA(T-T_{env}) + f$, which I suspect ...
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Would you run faster on Mars?
Given the 1/3rd of Earth's gravity on Mars and neglecting space suit limitations and also assuming you have maintained your muscle strength, would you run faster on Mars?
The answer may not be so ...
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Chemical detector of radio waves?
Since there are molecules in the eye that can detect electromagnetic waves at light frequencies, would it be possible to detect radio waves (longer wavelength electromagnetic waves) biologically / ...
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Why can we hear instruments but not voices?
I've seen this graph:
But I don't get something. Consider the 2kHz line (highlighted in red).
This graph implies we can hear an orchestral instrument at 2kHz before we can hear a human at the same ...
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Is it actually possible to make an amputated hand move with electricity? [closed]
I was watching a TV show that involved the police tracking down an insane person who was using deceased limbs to perform experiments on. It then cuts to a scene where they find the safehouse with what ...
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Does this work to reduce eyes strain? Enlarge the PC monitor with a lens
I have an idea to reduce eyes strain, but don't know if it works.
I work by looking at PC monitor all day long and I believe my myopia condition is getting worse and eyes strain occurs are due to ...
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Will I get a shock holding a superconductive wire?
Assume a current carrying superconductive wire is in front of me, with no voltage source attached.
If I hold it, will I get a shock? Forget for a minute that the superconducting wire will be too cold ...
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Where does the extra energy go when walking vs biking?
We burn a lot more Calories when walking a mile vs biking a mile. Why? Where does the extra energy burned from walking go? Is it that the mechanics cause the body to generate a lot more heat energy ...
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How can work done by a person be negative, e.g. in lowering a book? [duplicate]
I am holding a book of mass 0.5 kg in my right hand at a height of 1 m from ground level.
The book is lifted to a height of 1.5 m above ground and then brought down to its original height of 1 m. The ...
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Is my assumption for thinner limbs on race horses / hounds correct? [closed]
My assumption -as a layman- is that thinner limbs (given equal compared length on normal animal limbs) can accelerate faster due to their reduced mass i.e. unsprung weight transfer in regards to g-...
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Will a body start to deform if it is accelerating very fast? [closed]
I had a question in my mind that when a body will start accelerating in outer space where there is vacuum and no other object to hit the accelerating one, then will that body start to deform? I mean ...
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Does sound travel through FINGERS?
as we know that sound's speed is fastest in solid (and slowest in air).
QUESTION - what is the reason when we close our ears and don't really hear loud noises though sound travels faster in solids?
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What does it mean for sunlight to be of low entropy?
I once listened to a lecture by Sir Roger Penrose on life and also read the second answer to this question. If I understood correctly, then the reason why life still exists on earth inspite of the ...
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How can effect of electromagnetic radiation on human sperm be explained physically? [closed]
I am not sure if this question belongs here. If it doesn't belong here, feel free to remove it (and maybe tell me where to post this instead?).
I have been researching the question of whether ...
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How does the electrical ground rod work?
I was reading this article about shock current path, but it seems to be contradicting answers that I have seen on this site regarding electric shock. I can't find the original question but it was ...
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Physical Model of Exercise
Trying to model caloric effects on the body when exercising. I think I have something for lifting weights, but at a loss for running or bicycling.
Lifting Weights.
I think this is pretty easy. ...
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Are Humans and DNA the only things capable of creating order (Negentropy)? [closed]
the 2nd thermodynamic law insists that our universe is reacting towards a maximized state of entropy (disorder). Yet it is clear that order exists in the universe with cosmological and biological ...
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At which slope angle is a runner faster than a bicyclist?
On level terrain a bicyclist is faster than a runner.
On a steep slope a runner is faster than a bicyclist.
(That's why you see bicyclists pushing their bikes uphill.)
Can we calculate the angle where ...
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More on Bicycle Gears
I read a related post on bicycle gears and I still have a doubt. In low gear, the output force exerted on the ground is larger than the output force that would be produced in high gear. A large ...
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What physics could be applied to accelerate a person from zero to 8000 m/s if you want to: a) Minimize the time, and b) Not kill or hospitalize them? [closed]
My thoughts on this are that you would:
Immerse the person facing forwards in a neutral buoyancy fluid,
Slew the acceleration up and down just enough to avoid shock waves in their body,
Increase air ...
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If I lift a body with a force greater than its weight, what will happen to the excess energy provided to the body
I will give an example to explain my question.
Case 1:
An elevator lifts body a with force equal to its weight for a distance $d$
Energy given to the body (work done)$=$ Weight $×$ $d$
Amount of ...
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How to run faster? Velocity vs foot on floor
I was wondering how you can increase your running speed depending on how you set your foot on the floor.
In other words, how does the position of the foot area on the floor influence the speed/...
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What potential difference or current would kill a person?
I was watching this YouTube lecture, and earlier in the vid he mentions 120 volts from a power outlet would kill you. So if human resistance is $300\ \Omega$, $0.4 \rm A$ should be enough to do the ...
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Is there any possible scenario where a human could directly sense gravitational waves (preferably without being destroyed)? [duplicate]
Merging black holes radiate enormous amounts of energy - several solar masses worth! Unlike most astrophysical happenings, this happens on very human timescales. Most of the energy is released in the ...
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What happen if all the carbon-14 atoms in a person body decays at once?
What happens if all the carbon-14 atoms in a persons body decays at once? Would they die or will they be unaffected?
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Why does the length of a person change when they are lying down or standing up?
It's just an observation. I don't know if there is actually a physics theory behind it. I am looking for an intuitive answer.
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