The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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
6
votes
3answers
95 views

How unique is the length scale picked out by intelligent life? [on hold]

Our human bodies pick out a length scale (let’s say 1m). How unique is this scale and why did it arise? In other words, how much smaller could humans, or multicellular lifeforms in general, be while ...
0
votes
0answers
40 views

Why don't we see/feel charged particles, penetrating our brains/retina?

If we see tracks in bubble or Wilson chamber, it means that particles are everywhere and can leave tracks in gases and liquids. They can also penetrate concrete of the building levels in the lab. So ...
3
votes
3answers
145 views

Do proteins interact through classical or quantum mechanics?

For the protein interactions that occur in our cells, do they "follow" classical mechanics or quantum mechanics when interacting? I have zero knowledge about quantum mechanics, but I was wondering ...
0
votes
1answer
34 views

On seeing and especially in the dark

Our retina detects the change in the electromagnetic field due to the jiggling of the atoms surrounding us as I understand the seeing process. In the total absence of a light "source", however, why ...
22
votes
4answers
3k views

What determines the top speed in ice skating?

I was watching a hockey skating competition. The best skaters are able to accelerate quickly and turn without losing much speed; however, most people have similar top speed around 20-25 mph. What is ...
0
votes
0answers
14 views

What are good books to study life sciences related physics at an introductory level?

I study medicine, but also love physics and I want to have this physical and mathematical perspective of what I learn. What are some good textbooks for studying physics for the life sciences (i.e ...
1
vote
0answers
50 views

How precisely can you control the tip of a pen? [closed]

If we imagine that I have a pen that is very thin and I am trying to draw two straight lines very close to each other will the tip of my pen start moving randomly if I try to draw them very very close
1
vote
2answers
60 views

How does tanning oil increase UV skin damage?

I see many websites claiming oils amplify UV waves. This would only seem possible if thicknesses caused no reflection as in a quarter-wave coating, but that seems hard to believe. So, is it a myth ...
0
votes
0answers
23 views

Permeability of the human skull using Radio Frequency (RF) and Ultrasound waves

I have been looking into the permeability of the human skull using RF and ultrasound waves, and had a few questions. Which frequencies of Ultrasound and Radio Frequency (RF) waves can pass through ...
1
vote
3answers
108 views

Why are you doing no work when carrying a body through a horizontal distance?

Work done on an object is equal to $$FD\cos(\mathrm{angle}).$$ So, naturally, if you lift a book from the floor on top of the table you do work on it since you are applying a force through a distance....
0
votes
1answer
45 views

Relation of time dilation with Biological clock

I have completely understood the time dilation topic along with its mathematical derivation and consequences. And we know due to time dilation a person's biological clock slows down.So I am not ...
1
vote
0answers
44 views

Fine tuning of the cosmological and gravitational constants [closed]

Consider the gravitational constant $G$. According to philosopher Robin Collins, cosmologists have been able to determine a region $W_r\subseteq\mathbb{R}$ for which the universe would have permitted ...
1
vote
1answer
46 views

Nuclear relaxation time in absence of a magnetic field

It seems that after reading about how MRI scans work, and it appears that I had a misconception of what T1 relaxation times mean. From what I think I understand now, the T1 relaxation time refers to ...
-1
votes
1answer
112 views

5G networks and health concerns

Are there any peer reviewed journals on 5G networks and health concerns? I know very well that 5G radiation is of low frequency and non-ionizing and some concerns are related to the power of the ...
-1
votes
3answers
124 views

The fastest man on Earth physics

The legs of the world's fastest man (Usain Bolt) can develop up to 5 times the force compared to those of normal people. What stops him from being faster? A normal healthy high-school student can ...
1
vote
1answer
49 views

Why does blood pressure drop when blood vessels rupture?

Some people say that because the flow is large, the pressure is low. Is that right? Why does the pressure drop when the flow rate is high?
2
votes
1answer
98 views

Irradiated persons as sources of radiation?

The new HBO series "Chernobyl" is supposedly filled with misconceptions about radioactivity, among other things, according to an opinion piece published in "Forbes". In particular: "The most ...
1
vote
1answer
86 views

Quantum mechanical effects on humans

I just got into a flame war with a non-physicist who insists that the quantum-mechanical idea that the process of observation affects the outcome of an experiment is the fundamental reason why the ...
5
votes
1answer
143 views

Are birds warming up on high voltage lines?

Birds are unharmed on high voltage lines, because they touch only one wire and don't experience voltage as the difference of potentials. However, birds also seem quite comfortable there. Could this be,...
25
votes
2answers
5k views

How do photons get into the eyes?

I hope you will understand me correctly because there are some things that I translated. It is known that we see the world around us thanks to photons that are reflected from the surfaces of objects, ...
-3
votes
2answers
50 views

How can the motion of the brain within the skull be stopped at the moment of impact? [closed]

How can the motion of the brain within the skull be stopped or controlled at the moment an object with velocity comes in contact with it. What type of a system would this require?
1
vote
0answers
147 views

Are 5G signals dangerous? [duplicate]

Ive been seeing a lot lately on the dangers of 5g and exposure to the internet and mobile signals but I dont understand why they are considered harmful when the 5g frequency band will be around 25 Ghz....
3
votes
1answer
73 views

What does Earth feel like when squeezed?

he average density is about 4g/cm^3 so if the earth was in the size of an orange, it would feel like a rather heavy ball. The crust is relatively thin, and the earth is said to be solid land masses ...
1
vote
1answer
136 views

Cut in two but still alive? [closed]

Suppose we have an indestructible and sharpest knife ever made, which can cut through everything at ease. If it cuts you in half, you're more likely to be dead. As the knife begins to be thinner and ...
-1
votes
3answers
384 views

Why is grass green? [closed]

How come grass isn't blue or pink, but apparently, it is according to this scientist it is every color but green. I also got told by my teacher that grass is only green and no other color. So I am ...
1
vote
2answers
85 views

Why is radiation dangerous? [closed]

From Wikipedia: Exposure to radiation causes damage to living tissue; high doses result in Acute radiation syndrome (ARS), with skin burns, hair loss, internal organ failure and death, while any ...
1
vote
1answer
48 views

If you get punched, is it better to be lighter or heavier?

I've seen people argue that lighter people can take a punch better because they can "go with it" better. This seems plausible to me, but is it really true? One reason why it seems plausible is that ...
0
votes
1answer
83 views

How can sunlight cause skin cancer? [closed]

If the atmosphere absorbs the UV wavelengths, then what’s left is visible, IR and maybe a really small amount of UV that transmits it’s way to earth. IR and visible are non ionising, so is it the case ...
3
votes
6answers
614 views

Why is high voltage dangerous?

High $V$ low $A$ electricity is transformed into low $V$ high $A$ through a step down transformer for safer use in homes. But how is it any safer? The wattage is the same for the pre-transformer ...
1
vote
2answers
132 views

Are human beings radioactive?

I am reading "The greatest story ever told - so far" by Lawrence Krauss. He starts chapter 9, Decay and Rubble, telling how he was shocked when he realized that humans are radioactive. When I first ...
-4
votes
1answer
105 views

Can a projectile bullet kill? [closed]

Today, I was watching a movie, in which a person shot a gun in air. The bullet went high in sky, became stationary for a moment and dived back and killing a non-innocent person by hitting him in head ...
1
vote
3answers
229 views

Can radio waves be harmful to us?

I was studying about Microwaves and their action on water molecules in heating up the food. This all is probably due to Microwaves have wavelength such that it can be absorbed by water molecules (am i ...
24
votes
4answers
3k views

Could quantum mechanics be necessary to analyze some biology scenarios?

As an example, we could talk about a neuron cell in brain, with a size of $1 \mu m$ (=$10^{-6}$ m), being the distance between one neuron and next one in a synaptic connection of around 40 nm (=$40 \...
0
votes
0answers
31 views

The rise of BCI

If EEG and MEG are measuring different aspects of neural oscillations, why can't we measure the combined signals as a whole, when we are doing the same for higher frequencies? Why did the us navy ...
2
votes
1answer
196 views

Why hot soup is tastier than cold soup? [closed]

My physics teacher recently asked me this question. Can anyone answer the question?
-3
votes
1answer
62 views

Where does my mass go when i lose weight? [duplicate]

Presuming conservation of mass to be true, mass has to go somewhere if i lose weight. Doing workout i burn my fat to do some work but then where does that fat go?
0
votes
1answer
64 views

Is there a correlation between aging and the increase of organisms entropy?

This question is a restatement of Death by entropy. Question: Does aging, as we understand it nowadays (shortening of telomeres etc.) goes hand in hand with the increase of entropy? If so and an ...
1
vote
2answers
38 views

Fastest hyperloop-like vehicle which a human could endure [closed]

I'm currently writing on a science-fiction novel where a transportation system like the hyperloop has been built. Now, I'm wondering how fast I can make this. Since the plot takes place on many ...
1
vote
2answers
979 views

Am I positively charged or negatively charged?

We often hear that the human body has a weak electrical charge. Is it a positive charge or negative charge? Or maybe different parts of me have different electrical charges? Or maybe there's a ...
1
vote
1answer
37 views

How do we hear harmonics and how does it affect audio fidelity?

First and foremost, do we hear a sound wave as a sum of all the individual harmonics, at the fundamental frequency, or do we hear all the associated harmonics above the fundamental frequency and ...
6
votes
3answers
520 views

Why do cones require more light than rods?

The title says it. In our eyes, why do cones require more light than rods? Like is it because of the energy needed to change the state of the existing atoms, the molecules or what leads to the need of ...
0
votes
2answers
70 views

What is the max amount of photons per second of the rods and cones in our eyes?

The title says it all. I just cannot find any information about this - I have tried for so long now. Therefore, I figured that I could reach out to some clever guys in this forum for help instead:) ...
0
votes
1answer
48 views

Cycling: The energy behind it

I'm developing a school project (I'm studying software engineering) and it's about a sharing bicycles company. We need to calculate the total amount of necessary energy to travel from one point to ...
0
votes
2answers
36 views

What is the advantage of stacking the electrocytes? Of having the stacks side by side?

Electric rays (genus Torpedo) can deliver electric shocks to stun their prey and to discourage predators. The voltage is produced by thin, wafer￾like cells called electrocytes, each of which acts as a ...
2
votes
5answers
104 views

In thermal spas the temperature of steam is about $50^{\circ}C$, but feels way hotter. Why?

So when you're in hot water and start to move or something the steam feels really hot even though I read its temperature is about 50 degrees Celsius in thermal spas. So why does it feel that warm?
0
votes
1answer
541 views

Why don't we see inverted image while wearing spectacles? [closed]

We know that the lens in our eyes forms an inverted image on retina and brain reverses it to give the correct image. But when one wears specs the image would get reversed twice so we should see things ...
74
votes
5answers
7k views

Why can we distinguish different pitches in a chord but not different hues of light?

In music, when two or more pitches are played together at the same time, they form a chord. If each pitch has a corresponding wave frequency (a pure, or fundamental, tone), the pitches played together ...
0
votes
2answers
335 views

Relationship between blood pressure and cross sectional area of blood vessel

What is the reason why blood pressure and a larger cross sectional area of blood vessel cause a lower blood pressure and vice versa? This question is related to another question I found here. The ...
0
votes
1answer
230 views

Why do we sweat on a hot and humid day but the clothes are able to dry?

I know that on a humid day,water vapour content is high in air and as a result evaporation of sweat is lesser and hence we feel hotter. What I am not able to get is, if water vapour content is high,...
5
votes
2answers
129 views

How is it possible to survive more than a few cm submerged underwater?

Suppose you hold your breath and dive a meter underwater. Assuming the surface area of the back of your body is approximately $1$ m$^2$, you have about $1$ tonne of weight above you. If you were out ...