Recent content by synch

I was thinking more of half of the full 3-d ellipsoid, like half an egg shape. EG carve out an ellipsoid volume in foam then set the plaster around it. Now I remember , there was a image once, an ellipse of xenon atoms placed with an ATM. with a cobalt atom at a focus - there was a "ghost"...

I have seen drops of coffee ejected back from cups when liquid is added. It would be an easy experiment on the small scale, say make a half ellipsoid from plaster or somesuch in an old plastic drum, and see what happens if a baseball is dropped in at a focus. Maybe a bit messy though - I'll...

[ just a fun question :) ] Thinking of the focussing properties of ellipses - If a swimming pool was shaped liked a large half-ellipsoid...and someone dived in at a focus...would the splash then largely appear at the other focus ? In fact would a swimmer at the second focus then be projected up...

Thanks for the fantastic explanations and help ! I was vaguely aware of etalon filters, but didn't realise how narrow the passband was. They are certainly precise and expensive. Scratching around the net a bit, I can see there are (amateur level) oxygen(III) filters at ca 540nm/7nm width, and...

So images seen through a oxygen(III) filter are only seeing the photosphere hotter oxygen, with the bulk main emission being absorbed by the upper layers? BTW The image I remember (maybe incorrectly !! ) apparently showed structure in the wall of the sunspot, ie the photosphere around the...

As far as I know : Fluorescence is the phenomenon where a high energy radiation is absorbed, the energy creates an excited state which then collapses with a lower energy radiation being emitted. It is routinely seen with UV being absorbed and visible light given off, eg typically by some metal...

I thought ions in plasma could fluoresce ?

Is the Sun photosphere fluorescent ? I have seen some beautiful images with sunspots etc, filtered to particular spectral lines eg green O[III] and violet Ca for better contrast. I am wondering if those lines are Fraunhofer line absorbances or is there extra luminance from fluorescence at those...

Thanks everyone ! Well appreciated. I (now) wonder if anything with a non-zero spin can be regarded as "fixed" apart from approximation. But that is a whole different question and topic. Thanks again :smile:

Is there a gravitational analog of electromagnetic force? [Apart from the obvious "static" forces, ie electrostatic between fixed charges and gravitational between fixed masses.] I am thinking of the classic situation of a moving charge (or current) creating a magnetic field which then...

If a mass is moving it has a wavelength - my question is, is the gravitational field of the mass then modulated accordingly ?

[Will the spins be aligned in a weak field? .] The standard logic goes, magnetic fields are typically created by moving charge, and so on. But charge always seems to be associated with spin, so there is also spin involved. Hence my question regarding using changed spin . In general I am...

Does the magnetic field caused by moving particles depend on the particle spin value? Eg a stream of say protons spin 1/2 is creating a magnetic field. If the particles are (say) lithium nuclei spin 3/2 instead, does that create the same strength field ? (same conditions of course)

Well that is depressing. I knew platinum was generally used as a reduction catalyst in chemistry but thought it would be too awkward and expensive for the low-lifes. Thanks everyone.

I wanted to make a simple platinum electrode with a few cm of wire. But it is hard to get. Local (Australia) science equipment suppliers are now citing platinum wire as a drug precursor. I can't see how anyone uses platinum wire or salts as a drug to get high. I am puzzled, in any case it...