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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.

3
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1answer
64 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
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1answer
130 views

Cut in two but still alive? [on hold]

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 ...
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3answers
125 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
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2answers
60 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
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1answer
44 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
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1answer
70 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
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6answers
243 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
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2answers
119 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 ...
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1answer
93 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
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3answers
194 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
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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 \...
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0answers
26 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
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1answer
96 views

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

My physics teacher recently asked me this question. Can anyone answer the question?
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1answer
53 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
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1answer
48 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
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2answers
36 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
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2answers
323 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
33 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
276 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
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2answers
61 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
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1answer
47 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
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2answers
28 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
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5answers
93 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
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1answer
219 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 ...
75
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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
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2answers
206 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
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1answer
97 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
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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 ...
3
votes
1answer
39 views

What forces the maximum speed of a cyclist on a steep climb?

I know that on a flat road drag is the main force, I have to provide as much force as the drag (and the friction in the drive train) produces. I can also see that the faster I ride, the harder it gets ...
2
votes
1answer
31 views

Experiments in ISS

Recently a Japanese capsule brought back proteins that were created in ISS in the absence of gravity. Researchers will study them to "understand their folding better". My question is, regarding ...
0
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1answer
106 views

What are the main causes for eyeball becoming too long or short in myopia and hyperopia? [closed]

myopia and hypeopia occur due to change in eye ball size or lack in cilliary muscle ability to accomodate. \n\n But why in lasik laser operation , the one's cornea shape is changed rather than acting ...
0
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2answers
65 views

Symptoms of lethal neutrino radiation in a hypothetical scenario

Core collapse supernovae release the majority of their energy in the form of neutrinos. According to an XKCD What If, the neutrino radiation alone from a supernova at a distance of just 2 AU would be ...
24
votes
8answers
11k views

Is it possible to squat quicker than gravity?

It's definitely possible to propel your body using muscle to move towards the ground quicker than gravity. But is it possible to squat quicker than gravity? Assuming squatting from your knees and ...
1
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2answers
52 views

Does duration affect how lethal a current is?

It's been said in many places that it's not voltage that kills you but the source's current (or more so a combination of the two), but take a current of 0.1A which can be considered fatal. Would a 0....
2
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1answer
46 views

Do we have enough time for understanding space? [closed]

May be there more big bangs out there... while studding about space i some times think about a bacteria living on my body that may have a life span of 5 seconds if it has logical understating even ...
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2answers
50 views

Energy that can control itself (A unit that can process information without body) [closed]

I read a book called The future of the mind. There it suggested a conscience that exists in the form of energy without body. Ideally, I thought the energy without body may take the form of light. ...
12
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3answers
1k views

Humans have an average energy budget of $100$ Watts, but the power radiated from the body is $1000$ Watts?

On average a human consumes around $2000$ kilocalories per day. This converts to roughly $2000000$ calories / $86400$ seconds or around $100$ joules / second giving roughly $100$ watts. But if you ...
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2answers
50 views

Perception of curvature of human eye [closed]

How are human eyes able to detect the different curvatures of surface ? Basically how are the human eyes able to differentiate between a plane surface and a convex or a concave surface?
0
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2answers
156 views

Bernoulli's Effect on Blood Pressure [closed]

What is the impact of height, let's say being on top of a 4,000 m high mountain, on blood pressure / flow velocity given Bernoulli's Equation?
1
vote
1answer
245 views

What is the “comfortable” acceleration in a curve and braking in a car? [closed]

A car that makes a curve or a braking will naturally have its horizontal G-Force altered according to its speed and the intensity of the braking or the angle of the curve. My question is: which ...
0
votes
1answer
54 views

Would humans die of old age on an interstellar/intergalactic voyage? [duplicate]

It is often claimed that if we ever sent humans to colonize other stars, we would have to send them on generational ships. However, if the ship traveled at $99.9\cdots 9c$, wouldn't the passangers' ...
3
votes
2answers
92 views

Question about lenses in the human eye

To see near objects,the ciliary muscles contract and the suspensary ligaments loosen,making the lense thicker. İ don't understand how that helps us to see distant objects . To see distant objects ...
1
vote
2answers
46 views

Force, work and the apparent disappearance of Mechanical Energy [duplicate]

A man exerts force on a wall of bricks. The man must have consumed the energy he possessed (mechanical energy?) to exert the force. The man sweats and tires himself out but the wall does not move. ...
58
votes
6answers
9k views

How does light combine to make new colours?

In computer science, we reference colours using the RGB system and TVs have pixels which consist of groups of red, green and blue lines which turn on and off to create colours. But how does this work?...
3
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2answers
283 views

Why might Roger Penrose argue that Godel's incompleteness theorem(s) suggest that consciousness is non-algorithmic?

This past March, when I called Penrose in Oxford, he explained that his interest in consciousness goes back to his discovery of Gödel’s incompleteness theorem while he was a graduate student at ...
3
votes
1answer
61 views

probability density distribution: From free diffusion to presence of a barrier

I am a biologist and I am not very comfortable with statistical mechanics. However, I want to learn and I am trying to understand. I just need some clues from people that handle these topics easily. ...
0
votes
2answers
27 views

What is the optimal light setting for human vision? In other words, is my vision better during the day or at night?

There seems to me to be two main effects that should be considered in answering this question. The first is that the iris dilates in low-light settings, which causes an increase in the numerical ...
2
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1answer
1k views

How many calories in a block of wood?

I was recently thinking about the human body and the energy we get from food. I understand we don't have the ability to properly digest certain things like stones and wood and grass, but if we did, I ...
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1answer
80 views

Why universe is so perfectly made for us? [duplicate]

I am very eager to learn that, "Why universe is so perfectly made for us?" Or our universe is just stable by chance?
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1answer
43 views

Same amount of calories burned for half the reps and double the weight? [duplicate]

So I was looking at the work= force x distance equation and was just wondering if for example I normally do 100 dead lifts at 100 pounds. Would I get the same calories burned if I did 50 dead lifts ...