Recent content by evan-e-cent

By the way blocking UV light in the human eye may have another purpose since melanoma of the retina can occur with UV exposure. A more common problem is the formation of cataracts, especially in the tropics. This occurs when UV light exposure causes the lens of the eye to become opaque...

It may be of interest that DNA has absorption peaks in the UV range and if cell nuclei lay over the retina as they do in human eyes they might block UV light. They do block some visible light too. Sharks living underwater have much smarter eyes. They position the supporting cells behind the...

The graph is interesting in that it shows visible light corresponding with the peak produced by the sun. But equally interesting that it does NOT correspond with the light we actually see on the surface of the Earth at sea level!

So do we now move onto the mechanism of infrared detection in snakes? Of course IR is still considerably higher energy than the radio waves we were discussing. I also wonder whether this consideration of energetics has any relevance to the mass fear that radio frequencies could cause problems...

I asked "Has anyone wondered why water is perfectly clear". No one took my bait. Well I will give you my answer anyway. Vision evolved in water, in species that lived in the sea, or otherwise had eyes that contain water. Any wavelength of light that is absorbed by water would not penetrate...

All the above discussion is very interesting with different perspectives from people coming from different backgrounds, and with different areas of expertise. I was about to comment on the fact that the basic chemical structure of the light sensing molecule Retinal is the same in all the...

Further reading of Wikipedia on opsin proteins revealed: https://en.wikipedia.org/wiki/Photopsin In humans there are 3 different iodopsins (rhodopsin analogs) that contain the protein-pigment complexes photopsin I, II, and III. The 3 types of iodopsins are called erythrolabe(photopsin I +...

I don't think this mechanism of light detection corresponds with the excited state of electrons. It is more like a chemical reaction which requires a certain thermal activation energy to get over the energy hump and then drop into a lower energy state. This mechanism would not depend so...

Ah that explains the bulge of tides leading ahead of the moon. This would tend to speed up the motion of the moon and slow down the, rotation of the Earth until eventually, in many millennia they may be rotating at the same speeds I think. I thought that higher speed of rotation of the moon...

A doctor's perspective. I think we should be able to answer this by referring to the chemical process in the eye. The retina produces a chemical called retinal which can exist as two isomers. The cis isomer of the double bond has a higher energy state than the trans isomer due to steric...

Russ, after a lot of hunting I found where I think you had referred to the critical pressure drop of 65 psi. https://www.physicsforums.com/threads/velocity-of-compressed-air-blowoff.327909/#post-2291274 Thanks "Insightful". That seems to answer my question about the critical delta-P. My next...

It is amazing how things that we thought were simple, rapidly get complicated. In order to gain some understanding I tend to over-simplify them. That introduces assumptions that may not be valid. But I suppose that is the first step in learning. Thanks for the explanation. I wonder why the...

Thanks for the link. It shows a slightly different algebraic rearrangement of the formula I used. Perhaps I should explain my comment "There is little to be gained by higher pressures. " I had calculated the thrust (which is velocity times mass ejection) produced by the two steam nozzles...

I am not a physicist but his is how I see it. The reason that the moon is moving further away from the Earth is, I believe, caused by the moon's rotation slowing down. The gravitational force between the Earth and the moon is responsible for pulling the moon into its circular orbit. We used to...

I am planning to build a Hero's steam engine or Aeolipile. This is the steam engine invented by the Greeks about 2000 years ago. It is attributed to Hero or Heron (10-70 AD) but was also referred to in 15 BC. My grandfather build one for a show. I have inherited it but rather than try to repair...