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Physics, Astronomy & Cosmology / Re: Return to the Centre of the Universe

« on: 12/01/2015 05:47:30 »

Can we estimate the shape and dimensions of the visible universe?  Does it have a three dimensional form?  If so, where is the centre?

Shape of the visible universe: spherical, 3 dimensional.
Radius: About 13 billion lightyears.
Center: EARTH.

We don't know how big the unseen portion of the Universe is, and don't have a good idea to its form and shape.  But, the visible portion is roughly a sphere with Earth at the center.

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Physics, Astronomy & Cosmology / Re: how big?

« on: 06/01/2014 01:26:17 »

Above I calculated that a lunar (or solar) transit of the ISS is about 2 miles (across the equator) for any spot it is viewed from the ground.

At about 4.7 miles a second, the transit would last just under 1/2 second. 

For a 2 mile diameter body, going from a partial eclipse to full, back to partial eclipse would be about 4 miles, or in total it would last for about a second.

And, on Earth, the path that the full eclipse is visible would be extremely narrow.

I'm trying to imagine the orbit that would effectively slow it down.  I'm not sure you could design a LEO orbit so that it would "hover". 

In a geostationary orbit, your satellite would appear to hover over the equator, or in a different geosynchronous orbit, it would appear to move north and south.  And the apparent velocity would be greatly reduced.  However, your satellite would need to be about 100 times as large, or about 200 miles in diameter.

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Technology / Re: Is there a maximum temperature for a solar oven/furnace?

« on: 16/09/2013 23:09:51 »

I've seen notes about some mirrored solar furnaces rated for about 3000°C.  Perhaps the selection is because most materials melt below about 3000°C.

If one's collector was a refractory material like Tantalum hafnium carbide, perhaps one could hit up to about 4000°C before melting.  If one allowed a liquid collector, the boiling point of Tungsten Carbide is about 6000°C, but then one runs into problems with containing it and insulating it.

I suppose the question might be why one would need anything quite so hot, although undoubtedly there would be industrial uses for the ability to melt and vaporize many substances.

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Physiology & Medicine / Do antibiotics accelerate wound healing?

« on: 01/10/2011 21:43:57 »

Great article about glowing bacteria, and a sign that there are many things that should not be forgotten about the past.

As far as the original question, I believe there are indications that dressing a superficial wound will accelerate its healing by holding the skin together, and retaining moisture.  You can may also receive some benefit from the use of non-medicated petroleum jellies.

Deep wounds, or wounds on the face that might cause cosmetic damage may require stitches, or physician care.