1

Technology / Re: How dangerous are self driving cars?

« on: 21/03/2018 08:49:48 »

Computer vision is a difficult problem, but no doubt getting better. 

In this case, the reports are that the woman stepped out in front of the car.  What was she wearing?  Lights?  Everything seems to indicate that using visible light, she would have been difficult to see, and likely would have been hit be many human drivers.

However, I think there are likely several things that could have been improved.  For example passive IR might be good for night detection of life. 

The car is supposed to also have various types of active imaging that isn't necessarily dependent on visible light.  So, when was the woman first detected?  Could she have been detected earlier?

Part of driving is to anticipate that others will do stupid things.  So, perhaps slow down or move over to create a larger buffer around pedestrians, cyclists, and others that might cross one's path.

A lot of it is basic defensive driving.  Not really a "fault" thing, but rather just rules to be safe on the road.

We'll see what the final report about the incident says.

2

Physics, Astronomy & Cosmology / Re: Which is the Closest Star to Planet Earth ?

« on: 21/03/2018 06:54:08 »

It looks like we need to kick our space program into high gear.  We have about 10,000 years to get to Barnard's Star, otherwise we may never have another chance.  20,000 years to get to Lalande 21185 before it is gone. 

The Centauri cluster of stars will be hanging around a little bit longer, but still, it might not hurt to try to get a rocket out there in 20,000 to 30,000 years. 

And, with our current rocket speeds, we may have to get an early start on some of the trips. 

3

Physiology & Medicine / Re: What would happen if you stabbed yourself through your upper trunk?

« on: 18/03/2018 10:14:47 »

Probably a combination of a lack of anatomical knowledge coupled with an aversion to sticking things into oneself deters most people from trying to kill themselves this way. People aiming to commit suicide "like" the idea of dying (more than they like the idea of being alive) but that doesn't mean that they like the process. As a result, approaches that are very fast with little margin for error or reversing the process tend to be preferred: jumping from a height, medications, hanging and so on.

At least in the US, there are somewhere between 10:1 and 30:1 suicide attempts vs successful suicides, with men choosing more lethal guns more frequently than women, and women tending to choose drugs frequently with less lethal results.

It may well be that some of the attempts are actually cries for help, without consideration of the most lethal method, at least for those that are unsuccessful.

I presume a portion of the choice of methods is what the individual considers least painful.  So, taking drugs and "going to sleep".  Slitting one's wrist may seem to be less painful than trying to cut one's face and neck.

Even a choice of shooting vs cutting may be a choice of what may seem quick, easy, and with the least pain.  Perhaps jumping falls into the same category.

Of course, with the use of guns, people do typically aim for the head, and sometimes miss.

4

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.

5

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.

6

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.

7

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.