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.

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?...
8
votes
1answer
3k views

Would travelling at relativistic speeds have any impact on human biology?

If a person was sitting on a craft that has accelerated to near light speed speed from Earth (e.g. 99.999% of light speed) would there be any impact on his or her human biology due to relativistic ...
75
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 ...
11
votes
2answers
7k views

Why are smaller animals stronger than larger ones, when considered relative to their body weight?

I am interested in why many small animals such as ants can lift many times their own weight, yet we don't see any large animals capable of such a feat. It has been suggested to me that this is due to ...
111
votes
17answers
212k views

How does mass leave the body when you lose weight?

When your body burns calories and you lose weight, obviously mass is leaving your body. In what form does it leave? In other words, what is the physical process by which the body loses weight when ...
28
votes
8answers
7k views

Why is there a size limitation on animals?

Why is there a size limitation on human/animal growth? Assuming the technology exists for man to grow to 200 feet high, it's pretty much a given that the stress on the skeletal structure and joints ...
8
votes
3answers
1k views

Why do we use decibels instead of just using intensity to measure how loud things are?

In my physics book, it says that in the human ear, the sensation of loudness is approximately logarithmic. And that the relative sound intensity is directly proportional to a logarithmic ratio ...
8
votes
2answers
10k views

How can an an ant lift 50 times its own weight and pull 30 times its weight?

According to many sites like this one, an ant can apparently lift 50 times its own weight and pull 30 times its weight. Is it true? Can it be proved using physics? Though most sites agree that an ...
21
votes
9answers
4k views

Why can we cycle faster than we can run? [duplicate]

This seems obvious: faster long-distance runners hit ~20 km/h (marathon records) while fastest cyclists can do ~40 km/h (Tour de France stats). But on the physical/biological level this doesn't seem ...
16
votes
2answers
64k views

Effects of a very large magnetic field on the human body

Ever since reading about the NHMFL I have always wondered about this and asked several people without getting a good satisfactory answer. My question is, considering the simplest case let's say a ...
5
votes
6answers
22k views

Limit of human eye flicker perception?

I am designing a LED dimmer using software-controlled Pulse Width Modulation, and want to know the minimum PWM frequency that I must reach to make that LED dimming method indistinguishable from ...
4
votes
2answers
848 views

Human perception of distance

When we see things around us, distant objects look smaller to our eyes than nearby objects do. Is there any physics-related reason why our eyes or brain perceive things like this? Or if this is ...
2
votes
1answer
3k views

Effects of high frequency lighting on human vision?

I have a couple of different LED flashlights. One of them has three different "modes" of brightness, and the way it controls it is via pulse width modulation (PWM). Here is a picture that illustrates ...
1
vote
2answers
328 views

Is the universe really “fine-tuned for life”?

I understand what is meant when we say the universe is "fine tuned", but I've seen it claimed it's is fine tuned "for life". Is it? When I look at known or even speculated life in our universe, I see ...
5
votes
5answers
4k views

Is it really impossible for Bumblebees to fly?

According to some source or other (I forget which now) it is theoretically impossible for bumblebees to fly by virtue of their size/bulk/aerodynamic properties. Is this old adage apocraphyal or true? ...
1
vote
2answers
129 views

Neutrino project in Tamil-Nadu India [closed]

In Tamil-Nadu, the Indian government is going to start a neutrino project. Questions: Is it harmful for people who stay there? Will this project affect any living beings? Does it cause any ...
20
votes
6answers
21k views

Google interview riddle and scaling arguments

I am puzzled by a riddle to which I have been told the answer and I have loads of difficulties to believe in the result. The riddle goes as follows: "imagine you are shrunk to the size of a coin (...
23
votes
6answers
11k views

Physics of how the cochlea isolates frequencies along its length?

Can anyone explain the separation of frequencies along the basilar membrane of the cochlea please? (equations would be nice) I understand it being related to the resistance caused by fluid in the ...
21
votes
3answers
3k views

Why do different letters sound different?

If one sings the letter "A" and "M" at the same volume and pitch, the two letters are still differentiable. If both pitch and volume are the same however, shouldn't the sound be the exact same?
45
votes
3answers
24k views

Why aren't 100% UV blocked sunglasses safe to view an eclipse with?

I am not planning on staring into the sun during an eclipse or any other time. I have been reading about how no variety of regular sunglasses are safe enough to view the eclipse with. I'm not talking ...
20
votes
4answers
20k views

Why do whips hurt so much?

What exactly is the mechanism that makes a whip deliver such a strong impact? Elasticity, torque, or pressure? Just hitting something with a plank doesn't deal nearly as much damage. What's the ...
12
votes
3answers
15k views

Is it possible to kill a human with a powerful magnet?

I'm asking in terms of physics. Can powerful magnetic induction rearrange spins of my body in such way I will die? How? Or maybe it can rip all iron from me, which would make my blood cells useless? ...
8
votes
3answers
2k views

Most True to Life Physics & Biology Simulation Engine? [closed]

I'm a programmer. I code in C++, C#, HTML5, and PHP. There are many graphics engines I have at my disposal. The question is: Does there exist a graphics engine that is as true to our reality as ...
14
votes
2answers
589 views

Implications of parity violation for molecular biology

In biology, the concept of parity emerges in the context of chiral molecules, where two molecules exist with the same structure but opposite parity. Interestingly, one enantiomer often strongly ...
5
votes
3answers
4k views

What is the minimum optical power detectable by human eye?

If one is in complete darkness, what is the minimum optical power that the eye can "see" (let's say in 500-600 nm range). I found that for 510 nm, 90 photons can be detected (http://en.wikipedia.org/...
9
votes
2answers
17k views

How many frames can human eye see? [closed]

What's the limitation of our eyes? Can we differentiate 60fps from 120fps? Are new 144hz monitors just a marketing trick? Couldn't find any proper journals or studies about the matter.
6
votes
2answers
1k views

Are living organisms deterministic?

Are living organisms physically deterministic at any given time? Since it's all physics and chemistry, it leads me to believe they are.
-1
votes
1answer
1k views

Why can I look at the sun with my sunglasses but not at the solar eclipse?

Is the problem with seeing an eclipse that you have a sudden change between penumbra and regular sun? If that's the case, why can I look to the sun with my sunglasses on but I can't do it in an ...
8
votes
1answer
8k views

How much sky do we see at any one moment?

When we look at any particular point the sky, what percentage of the celestial sphere do we see? This question arises from the notion that on average there passes one meteor per hour overhead. So ...
4
votes
1answer
246 views

Relation between Casimir and hydrophobic effects

Background Some years ago I was studying "Fundamentos de biología" (Biology fundamentals) and learned how the lipids create a bilayer due to the water repulsion. Some time later I learned that this ...
2
votes
2answers
2k views

Are cosmic muons causing mutations or even influence evolutionary rate?

As there are experiments studying influence of cosmic rays on organisms, http://www.ncbi.nlm.nih.gov/pubmed/11541768 I ask my self, if there any influence to DNA from atmospheric muons on the Earth ...
2
votes
2answers
152 views

What sound frequency can be heard the greatest distance by humans?

What sound frequency can be heard the greatest distance by humans? Assuming a pure tone, single frequency, same source SPL (dB) for each frequency, outdoors with no obstacles between source and ...
2
votes
1answer
564 views

Physical explanation of seeing sparkles?

I know this might look more appropriate to ask this kind of question on the biology or medical stackexchange but since this kind of cross-science question I'll ask it here. Sometimes when sitting and ...
2
votes
0answers
420 views

What is the maximum magnetic field that a human body can withstand? [closed]

Are there limits to the exposure of human bodies to magnetic fields? What happens if we cross that limit? How to create such magnetic fields? Has this been tried out?
1
vote
0answers
103 views

Why are there limits on physics' applicability? [closed]

(Not sure if this is the right SE for this question). Physics is great at predicting what inanimate stuff do. Why can't it also predict what living things do? For example, if I throw a ball off a ...
1
vote
2answers
320 views

Thermal Radiation of human body

I've read that all bodies emit electromagnetic radiation of all wavelengths. Does this mean that humans emit gamma rays too (excluding the radiation from radionuclides present in humans)?
1
vote
0answers
317 views

Is it possible to prove that an elephant and a human could jump to the same height? [duplicate]

Is there a physics argument, based on scaling, that leads to the conclusion that an elephant and a human could jump about same height? Could this be extended to any two creatures with different ...
0
votes
1answer
748 views

What happens when a bird lands on a power line?

I know that when a bird is sitting on a high-voltage power line, virtually no current flows through the bird because there is (almost) no voltage drop between its legs, the two points are ...
-1
votes
3answers
3k views

Death by entropy [closed]

An idea struck me as I was walking to class today. According to Wikipedia, entropy is defined as the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a ...
-2
votes
1answer
473 views

Space-time hospitality

Are there any reasons to assume that organic processes cannot arise in relatively flat spacetime environments? An argument for the existence of a critial value or window.