9081

Physics, Astronomy & Cosmology / Re: Northern Lights & Holograms

« on: 30/04/2007 17:58:59 »

what I was wondering was if there was any applicability of using rainbows as holograms. 

The "Fogscreen" does use water droplets to display images , but they are not holographic:-
http://www.it-ltd.com/fogscreen.php?gclid=CK-hgNP16osCFQfnlAodMg8QQw
It only costs £62K  []

9082

Physics, Astronomy & Cosmology / Is it possilbe to do astrophotography with a normal digital camera

« on: 30/04/2007 17:14:08 »

The big problems are focussing, holding the telescope steady and tracking the earth's rotation for a long exposure picture

For DIY enthusiasts, here is how to build a "Scotch" mount which allegedly will permit a 20 minute exposure with a standard camera lens.
http://www.philharrington.net/scotch.htm
[Don't blame me if you get RSI from hand-cranking the thing  [].]

9083

Physiology & Medicine / Blood pressure

« on: 26/04/2007 15:35:56 »

The numbers are the pressure in millimeters of mercury (mmHg)

9084

Physics, Astronomy & Cosmology / What colour is dust?

« on: 25/04/2007 16:57:38 »

Anyway- as Quentin Crisp  once said - "After two years, the dust doesn't get any worse."

He (Quentin Crisp) moved to New York in the early 1980's and lived, as ever, alone in a one room apartment which he famously never cleaned.
 "After four years," he quipped, "you don't notice the dust."

http://news.bbc.co.uk/1/hi/uk/211644.stm

9085

Physics, Astronomy & Cosmology / Is it possilbe to do astrophotography with a normal digital camera

« on: 25/04/2007 16:18:55 »

Is it possilbe to do astrophotography with a normal digital camera.

It is possible to attach a cheapo webcamera to a telescope...
http://www.astrocam.org/english.htm   

9086

General Science / Why do males have breasts?

« on: 25/04/2007 15:45:01 »

Some men actually do have breasts, try googling "gynecomastia".

9087

Physiology & Medicine / Re: How does the blood pressure of an amputee compare with normal?

« on: 25/04/2007 15:30:58 »

Do amputees suffer from high blood pressure!

There could be an association between hypertension and amputation:
If someone has had their leg amputated because of arterial disease
they would also have hypertension (high blood pressure).
(They would have had hypertension before and after the amputation).

9088

Physiology & Medicine / Blood pressure

« on: 25/04/2007 15:24:48 »

can you have low blood pressure, and what illnesses does it cause?

Abnormally low blood pressure is called "Hypotension", it causes fainting.
(High blood pressure is called "Hypertension").

9089

Physiology & Medicine / Eye lids

« on: 25/04/2007 14:30:19 »

If eyelids were totally opaque then the pupil would adapt to total darkness during a blink and dilate to its maximum size, then when the eyelid was opened vision would momentarily be compromised by overexposure, (pupils do not change size instantaneously).
So totally opaque eyelids are not a good idea.

9090

Chemistry / Why do Old Books Smell ?

« on: 19/04/2007 15:16:28 »

Books that are well old seem to have a smell all of their own ?

Or is it just my imagination ?...

..and the pages seem to go a kind of yellow/orangey tint ?...are these two related ?

The yellowing can be due to UV

Rapid and serious deterioration of paper is caused by the oxidation of cellulose brought about by the ultraviolet rays in sunlight and fluorescent light. There are two effects of light on paper that result in its ultimate embrittlement and deterioration. First, it has a bleaching action that causes some whitening of paper and fading of colored papers and certain inks. Second, it causes any lignin, which may be present in the paper, to react with other compounds and turns it yellow or brownish. It is this reaction that results in newspapers' turning yellow on exposure to light.

http://palimpsest.stanford.edu/byauth/maravilla/deterioration-causes.html

9091

Physiology & Medicine / noses

« on: 14/04/2007 10:42:20 »

http://en.wikipedia.org/wiki/Olfactory_nerve

9092

Physiology & Medicine / eyes

« on: 14/04/2007 10:38:24 »

http://en.wikipedia.org/wiki/Lacrimal_gland

9093

Physiology & Medicine / Hot drinks & poo

« on: 14/04/2007 10:31:40 »

gastrorectal reflex

9094

Physics, Astronomy & Cosmology / Re: What is this hexagon shaped object on Saturn?

« on: 14/04/2007 10:24:35 »

The hexagon formation could be a resonance effect, like these Cymatic images...
http://en.wikipedia.org/wiki/Cymatics

Orbital resonance can create 60 degree patterns ...

Trojan asteroids cluster around one of two points that lead or trail the planet by about 60 degrees in its orbit, known as Lagrange points.

http://www.spacedaily.com/reports/Three_Trojan_Asteroids_Share_Neptune_Orbit.html