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Technology / How does a computer chip work?

« on: 11/10/2009 04:11:38 »

Graham certainly knows what he's talking about, but unless you're going to actually go into chip design, it's not really as important as understanding the binary logic that is basis of all computing.  You need to focus on truth tables and boolean logic, then work "upward" from there.

If you are interested in how digital circuits work, I've picked up a book at library called "Digital Electronics Demystified" by Myke Predko.  I've only gotten through the first few sections, but it is very clearly presented, and starts with basic logic theory.

I've worked with computers in various capacities for decades.  If you really want to learn computers, get one, decide on something you'd like to do (a program), then grind through it.  Experience is an excellent teacher.  What you have to develop is a sense of what computers do well and what they don't do well.

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Physics, Astronomy & Cosmology / Probability of Existence discussion

« on: 09/10/2009 04:24:12 »

Hmmm.... I'll admit my knowledge of QM is superficial, but I recently listened to a podcast from Scientific American in which a scientist from the University of Arizona used the term "thermodynamic gradient".  My understanding, and my concept of how the universe came to be leads me to the conclusion that the universe does not run "up hill".

My vague memories of chemistry and physics in college dredged up a quote, paraphrased, that the universe would be happiest with an evenly distributed volume of hydrogen, at just around absolute zero.  That's a roundabout way of saying that the laws of the universe seem to hate complexity.  It would make sense if we started with complexity, and "devolved" to the current state, but that's clearly not where the evidence is pointing.

I've just never been comfortable with the idea that the incredible complexity of our universe sort of "fell" together.  Oh, well, that question won't be answered in my lifetime (unless the LHC spits out a miracle).

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Physics, Astronomy & Cosmology / How large would a rotating spaceship need to be to create artificial gravity equal to that on Earth?

« on: 09/10/2009 04:00:58 »

Graham,

Cost isn't a consideration, nor is hull temperature (although it would be in a discussion of a "practical" solution).  I was thinking more like "Rendezvous with Rama" (Arthur C. Clark).  Kilometers in diameter.

I get the feeling this question may not get an answer, because of the variable nature of "perceived" motion.  I suppose we could decide on an acceptable amount of lateral force on the upper part of your body.  I was watching "Top Gear" om BBC America, and I saw a device mounted in a car that showed the G forces exerted during a turn.  It consisted of a hollow, plastic ring filled with a red liquid.  As the car turned, the liquid tilted in relationship to the "plane" of the camera.  So if we decide on an arbitrary tilt of 5 degrees, it would would represent some measurement of lateral force.

How much force, I can't say.  Perhaps our mathematician could calculate what that force would be.  Once that is known, we can then assume a person of average height (180 cm) and weight (77 kg), with a normal distribution of that weight along the body.  The calculations for this is probably complex.  The key result of that calculation would be the speed of the ground (acceleration) on the person's feet.

With that value as a "limit", the other calculation would be the down force (gravity) and the centrifugal force needed to produce it.  From that, the diameter might be calculated.  But like I said, I have nothing close to the math needed to figure this out. 

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Physics, Astronomy & Cosmology / How large would a rotating spaceship need to be to create artificial gravity equal to that on Earth?

« on: 08/10/2009 04:07:02 »

It's me, the person who asked the question.  Thanks for the responses.  I think a few things about the "parameters" of my question.  So, I'll elaborate.

The Coriolis effect (wherein the friction of a rotating body against some "fluid" mass (or least something that can 'bend') causes the portion of that mass closest to the rotating body to move at a higher rate than that farther away from the rotating body), is really THE critical factor in terms the user's experience.  If you've ever been on a children's merry-go-round, and had it move suddenly under you, your legs move immediately with the merry-go-round, but your upper torso's mass tends to stay put, potentially taking you off your feet.*

Being in a small ship rotating at high speed would be very difficult to stand in.  The Earth, in the context of this questions, does not count.  While centrifugal force has a finite, measurable, effect on people, the Coriolis effect can't really be perceived directly by people. 

This question is, at least at our present level of technology, purely theoretical.  This isn't about an actual design, but rather, what diameter of cylinder would be needed to simulate Earth gravity (1G), without an "average" observer perceiving the rotational motion.  Yes, I realize that would depend upon the observer's sensitivity to motion, but work with me here.  So, some bright mathematician, physicist, engineer out there needs to decide on some "acceptable" difference in inertia between the observer's feet and head.  Then, based upon that acceptable difference, how big would the cylinder's inside diameter be?  I realize it's not a easy question, but that's why I asked all smart folks who listen to the Naked Scientist.


* Yes, I know, the people who write into this forum could probably quote Gaspard Coriolis' principles from memory, but I thought I'd "hold forth" with an oversimplification.

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Physics, Astronomy & Cosmology / How large would a rotating spaceship need to be to create artificial gravity equal to that on Earth?

« on: 05/10/2009 01:30:04 »

Michael Peoples asked the Naked Scientists:
   
I've read many science fictions that involve large structures in space where people live on the inner wall of the rotating "spaceship". 

Now, I'm one of those who cannot tolerate being "spun" in any way (a child's merry-go-round can make me ill). So my question is this: 

How large would the inside of the enclosure have to be so that the centrifugal force would create artificial gravity equal to that experienced on Earth, but produce no perception of motion on the part of the observer?

In other words,  it would be just like standing on our planet, except the sky overhead would be a view of your neighbours.

What do you think?