The biophysics tag has no wiki summary.
21
votes
7answers
3k views
Why does holding something up cost energy while no work is being done?
I read the definition of work as
$$W ~=~ \vec{F} \cdot \vec{d}$$
$$\text{ Work = (Force) $\cdot$ (Distance)}.$$
If a book is there on the table, no work is done as no distance is covered. If I ...
23
votes
3answers
2k views
Why is the sky not purple?
I realise the question of why this sky is blue is considered reasonably often here, one way or another. You can take that knowledge as given. What I'm wondering is, given that the spectrum of ...
9
votes
3answers
356 views
Why does light of high frequency appear violet?
When people are asked to match monchromatic violet light with an additive mix of basic colours, they (paradoxically) mix in red. In fact, the CIE 1931 color space chromaticity diagram shows this ...
13
votes
4answers
2k views
What does Peter Parkers formula represent?
Okay, so the trailer for the new Spider Man movie is out and appearently our friendly physicist from the neightborhood came up with something. However I can't find out what this is.
...
3
votes
2answers
356 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 ...
14
votes
2answers
2k views
How does space affect the human body (no space suit, no space craft)
How does "outer space" affect the human body? Some movies show it as the body exploding, imploding or even freezing solid.
I know space is essentially a vacuum with 0 pressure and the dispersion of ...
36
votes
7answers
2k views
Cyclist's electrical tingling under power lines
It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...
6
votes
2answers
370 views
Quantum Computing and Animal Navigation
Someone sent me this link to a talk by Prof. Klaus Schulten from the University of Illinois: (my emphasis)
Quantum Computing and Animal Navigation
Quantum computing is all the rage nowadays. ...
12
votes
1answer
387 views
Is colour, as represented using primary colours, accurate only to humans?
Slightly biological, hopefully physical enough to be answered.
Suppose a magenta hue is represented by a mix of red and blue pigment. This is all very well for a creature with red and blue ...
6
votes
2answers
942 views
How are the calories in food calculated?
This is intended to be a fun question. Calorimetry used for calculating the heat generated from chemical changes has been around for centuries, however, I suspect the process for calculating food ...
5
votes
2answers
253 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 ...
1
vote
2answers
228 views
What happens to body chemistry at the speed of light?
Assume that I'm traveling at the speed of light in one direction. My brain is also traveling at the speed of light in that direction. Presumably there is at least one receptor site in my brain that is ...
4
votes
2answers
1k 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 ...
2
votes
4answers
1k views
Is it only red, green and blue that can make up any color through additive mixture?
I'm reading about color vision and have some trouble understanding the motivation for why the trichromatic theory was suggested in the first place. The book I'm reading ("Psychgology: The science of ...
2
votes
1answer
795 views
How to calculate calorie expidenture from lifting a weight?
Am I correct to say that when a human lifts a dumbbell from, say, 2 feet off the ground to 6 feet off the ground, he will have increased the potential energy of the weight and thus will have burned ...
1
vote
2answers
83 views
Was the early Earth radioactive?
I've been reading of the (surprising) fact we are uncertain on whether there is nuclear fission in the center of the Earth or not (yet we know so much detail on structures at the other end of the ...
1
vote
2answers
220 views
Running: Determine how much more energy is needed per extra kilogram of weight
(I recently asked this on maths but was directed here)
I have recently become a runner and having a keen interest in kinematics I'm very interested in the maths/physics of my running.
Can someone ...
