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.

Filter by
Sorted by
Tagged with
-2
votes
0answers
40 views

It is harmful to look directly towards the Sun. Why? [closed]

Sun's electromagnetic spectrum, Convex lens of the eye, Retina.
0
votes
0answers
27 views

Has there been any development regarding lifelike helical dust structures? (Tsytovich et. al. 2007)

Tsytovich et. al. 2007 proposed that some interaction of dust and plasma might produce inorganic lifelike structures. Has there been any development regarding such theories?
2
votes
0answers
24 views

What is the physics behind why incorrect cuff size for measuring blood pressure manually or automatically lead to inaccurate results?

The biophysics behind measuring systolic and diastolic blood pressure manually with a cuff and stethoscope is that Determine the approximate pressure it takes for the cuff to occlude the brachial ...
0
votes
1answer
47 views

How much weight do I need to lose to grab the basketball rim?

I am 195 pounds, 71" tall, standing reach of 92”. Currently, I can jump to touch 115" in height (finger tips). I'd like to jump to 123" in. to grab the basketball rim. (Note: 10ft/120&...
3
votes
2answers
76 views

How much energy is transferred to a human hit by lightning?

Wikipedia tells me that a bolt of lightning releases roughly 1 GJ of energy, but I'm guessing that's along the entire length of the bolt and that most of it is dissipated as heat and light to the ...
-2
votes
2answers
203 views

Physically, how does erection work?

All articles I found explain a human male erection through biological mechanism. However I am still curious how such process can make the male sexual organ "stand up" during an erection. ...
-1
votes
1answer
65 views

Do my arms feel pain if I put them upwards in space? [closed]

On Earth, our arms feel pain if we put them upwards due to the gravitational force downwards. Is this also true when I find myself in empty space (without gravitation)?
2
votes
2answers
68 views

When I just move my hands around, how is the momentum being conserved?

I guess when I'm moving my hands around, the electrostatic potential stored in the chemicals in my body is converted to motion of my arms? But what about momentum conservation? I think the brain sends ...
0
votes
0answers
136 views

Avoiding snails around potted greenery

I am not sure how a snail "sticks" to surfaces e.g. plastic pot or stone. I suspect that it produces mucus, which then adheres with molecular forces. I would like to know, how does the ...
0
votes
1answer
22 views

Binnig's fractal evolution applied to multiple universes?

Gerd Binnig, Nobel laureate in physics in 1986, proposed in his article "The fractal structure of evolution" 1 that everything in the universe, including its laws, had changed and became ...
2
votes
1answer
34 views

How is it that some mammals avoid the dangerous physiological effects from hyperbaric conditions?

Deep sea diving and cassion workers are at extreme risk from many hazards such as "bends," nitrogen narcosis, and oxygen poisoning when compressed air is absorbed into their bodies, and then ...
0
votes
1answer
36 views

It seems like the many-world hypothesis would explain the Fermi paradox?

The fermi paradox asks why we don't see more complex life in the universe if we exist? Essentially, it seems either would naturally develop in our universe, in which case it would be plentiful, or it ...
0
votes
4answers
80 views

Why can a batter hit a pitched ball farther than one thrown by himself? [closed]

The main problem I am having is what Actually remains constant in the two cases. Is it the average force, or the time period for which the force is exerted? any helpful hints would be appreciated. ...
1
vote
0answers
33 views

What is the entropy difference between $n$ free-floating amino acids and $n$ amino acids that have been translated into a protein?

Is there any known calculation for the (~ average) change in entropy between $n$ free-floating amino acids in a cell, at typical physiological concentrations, versus those same $n$ amino acids after ...
-2
votes
2answers
39 views

Newton's first law of motion [closed]

A dog sleeping in a room and after some time it suddenly woke up and started running so its state of rest changed but no external force is applied on it. Every one will answer this like **the leg of ...
2
votes
4answers
118 views

How do we get energy to start walking?

The answer seems obvious, it's our energy that gets converted into kinetic energy. But my question is how exactly? Which force is responsible for doing work on us so that we gain kinetic energy? It ...
-1
votes
1answer
105 views

How do we know that the peak of human eye sensitivity is at 555 nm? [closed]

How do we know that the human eye is most sensitive to a light of wavelength of $555$ $nm$ and power of $1/683$ watt? How are experiments performed for obtaining this result? What's so special about ...
0
votes
1answer
70 views

Why aren't we (humans) affected from magnetic field?

From what I understand humans has a capacitance and are able to store charge, and we also have a velocity, we know that the magnetic force is $\vec{F}=q\vec{v}\times \vec{B}$. I assume while we ...
0
votes
2answers
97 views

Can human brain do quantum computation?

First of all, I know that any math (or computation) a classical computer can do, we human can do with pen and paper at same type of efficiency. Obviously, that is because we tell a classical computer ...
0
votes
0answers
12 views

Are PMLs also used for soft-matter structural dynamics modelling as they are commonly used in Wave Propagation modelling?

Numerical modelling of waves by FDTD method makes use of PMLs to establish absorbing boundaries. I recently began modelling soft-material structural dynamics (for biological cells) using FEM where the ...
2
votes
3answers
371 views

Why does it take different levels of effort to lift two objects with the same mass?

Suppose we have two different objects, one denser than the other. In short, what I mean is that one object is bigger than the other but they have the same mass. Now why does it take different efforts ...
2
votes
1answer
154 views

Could a human, even in principle, hear a gravitational wave? If so, how powerful must it be? [duplicate]

Sufficiently powerful gravitational waves can excite an eardrum and be heard. How powerful would the waves have to be for a human to actually hear them, and what would be the side-effects of that ...
1
vote
0answers
61 views

At what slope angle does walking uphill become more energy-efficient than cycling?

At what angle does walking uphill become more energy-efficient than cycling? To me cycling uphill feels harder than walking uphill, so I wonder at what slope-angle this happens. Two other ways to put ...
5
votes
3answers
69 views

Pressure at the greatest depths humans have dived to without a suit is many atmospheres but humans not crushed, why?

I understand that the pressure can be 50 atmospheres: https://en.wikipedia.org/wiki/Deep_diving. Okay, I understand also that the pressure is equal all around but if someone was put between two metal ...
1
vote
1answer
38 views

Why does hair dry faster when I have less hair?

I recently had a haircut, and have noticed that water in my air dries up faster when I short hair. I assume that hair loses water due to evaporation. We have been taught that evaporation is faster ...
1
vote
1answer
72 views

Why is Polonium-210 more lethal than other radioisotopes? [closed]

So it takes a single microgram or less of pure Polonium-210 to be lethal. Which according to basically all sources makes it the most toxic material or at the very least the most toxic element. But why ...
0
votes
1answer
27 views

Does leveraging a leg reduce the amount of resistance during exercise?

Diagram: A - Resistance machine configured with 50lbs of resistance and in an overhead pulley system B - Performing a bicep exercise standing with feet shoulder width apart and underneath torso C - ...
1
vote
4answers
109 views

Why exactly do we feel a shock when we place our hand into a conducting solution?

I have a very naive question. Suppose you have pure water in a flask, and you place two ends of a copper wire (which are connected to a battery) into the water. If you were to place your hand into the ...
1
vote
2answers
63 views

What determines the mathematical relations between energy use, axon thickness, and firing rate of action potentials in a neuron?

I have a naive model of action potential energy use and I’m unsure where the model is wrong. Clearly the model is wrong because its conclusion is wrong: When an action potential moves along an axon, ...
49
votes
4answers
14k views

Could I survive at (or near) absolute zero with a very, very, very thick sweater?

Imagine I'm in an infinitely large vacuum and have a special apparatus built into my body that allows me to breath, eat, pee/poo, etc. and never age. The vacuum is similar to deep space and has no ...
1
vote
2answers
72 views

Teaching Electromagetism to Life-Science Students

I am going to be teaching an introductory university class on E&M and Modern Physics (from Coulomb's Law through Maxwell's Equations and optics, followed by a brief mention of quantum and ...
0
votes
1answer
40 views

Has physics ever tried to explain how do we get “sensorial experiences”? [closed]

To be clear about what I mean with "sensorial experiences", let's take for example our visual experiences. Certainly, physics (and other sciences) explains a whole process which involves light ...
0
votes
0answers
31 views

Is 260 picoampere sufficient to transmit a signal through an axon in a nerve?

Would 260 picoampere be sufficient to transmit a signal through a 1 meter long axon in a nerve, with a diameter of one micron? There is context to why I ask this, but, because of failure to interpret ...
3
votes
4answers
212 views

How much current will go through my body if I were to put my finger in an outlet?

i know this is a silly question, but i couldn't manage to wrap my head around it. I am kinda new to electronics. My home's outlets provide 220V. Upon doing some (a lot) research, the current that ...
-1
votes
2answers
91 views

Why is it hard to exercise with wearing the mask? [closed]

In today with COVID 19, we should wear the mask all day. My teacher in Korean high school said "If you want to play basketball, you could play with wearing the mask" to me. My friends and I wanted to ...
19
votes
11answers
3k views

Are colors grounded in physics or are they a matter of human perception? [duplicate]

My father was colorblind, and I always wondered if colors were a matter of physics or if different colors are just a human way of describing and differentiating our visual perception of the world? ...
0
votes
0answers
37 views

Using particle physics math model to simulate simplest life [duplicate]

We still don't know many thing going inside living cells so I'm wondering whether it's possible to create a math/computer model operating on basic known particles (or higher level composite particles ...
25
votes
10answers
6k views

What determines whether colors you can't see are visible or not?

So, when someone is red-green colorblind, the colors appear the same to them, like this: And if you're totally colorblind, then things presumably just appear like they would in a black-and-white ...
4
votes
6answers
738 views

Does bending your arm in space require any energy?

Since your are weightless in space, your arm has no weight, right? Does this mean that bending it in space requires no energy? Why or why not?
1
vote
1answer
26 views

Energy Conservation in Holding Weights [duplicate]

This is a two part question, and it might have to do with biology a bit. Part 1: I grab a heavy dumbbell and curl it. Halfway up I stop the curl and just hold it there with my elbow at 90 degrees. ...
-2
votes
1answer
37 views

Why do leaves of trees shudder when they expose to heavy smoke? [closed]

Why do leaves of trees shudder when they expose to heavy smoke? See this video here: https://i.imgur.com/hTOOxu6.mp4
-1
votes
1answer
61 views

Is $200 \,\text{J}$ enough for heart defibrillation? [closed]

In some movie I saw that defibrillation was done on a patient by emitting $200 \,\text{J}$ electric impulse onto heart region. I couldn't in noway imagine is this quantity big or small, so I've tried ...
0
votes
2answers
53 views

Can life decrease the entropy of an isolated system? [closed]

A high entropy isolated system is shuffling through its more probable micro-states. Local entropy dip produce several structures. These structures, akin to life, feed on free energy to preserve ...
2
votes
1answer
42 views

During pull-up, does your upper body use less energy when the legs are raised?

The pull-up mainly uses your biceps and your lats, which are exclusively upper body muscles. So would raising your legs during a pull-up reduces the energy used in those muscles? Let's say the energy ...
-4
votes
1answer
53 views

Restart the Universe expansion? [closed]

Is there anything that could restart the universe expansion? Basically a black whole or something else entirely different? It seems to me that, once the Universe stops expanding, the human life ...
4
votes
1answer
51 views

High pressure cryonics

In this link, it is suggested to use high-pressure cryonics to freeze living cells, tissues or small organism as opposed to various and potentially toxic anti-freeze agent. The core idea is that over ...
-17
votes
2answers
181 views

What does meant AC corona? Any connection to coronavirus? [closed]

In the abstract of this paper Authors said in abstract of that paper entitled Simulation of the AC corona phenomenon with experimental validation : ".....,This phenomenon is also associated with ...
0
votes
1answer
91 views

How can a picture of a virus be taken when they are not even 300 nm (wavelength of blue light) long?

We cannot take photos of protons because they are not at least the size of the wavelength that registers into visible light. I see photos of Coronavirus in the news everywhere where there is a clear ...
1
vote
0answers
41 views

Physics-based Demonstrations for biology students

I am looking for resources where physics concepts relevant to biology are explained in simple terms by actual experiments or virtual animations. The site should be suitable for freshman students with ...
1
vote
0answers
75 views

Is there a minimum principle which governs neuronal activity in brain function? [closed]

Reinforcement learning is a well established field which attempts to explain the behavior and decision-making of toddlers, among other agents. The core principle of this theory is based on dynamic ...

1
2 3 4 5
7