Darth, please check your sarcasm detector. It seems to be off or broken.

This system still requires energy input to launch things into orbit, but the key point is that it requires orders of magnitude less energy than a conventional rocket launch. Without going into the math, the key feature of the launch loop, space elevator, or other "skyhook" technology is that the propulsion system applies force against a structure that is anchored to the ground. This means that most of the energy goes into accelerating the payload.

In a conventional rocket, the propulsion system is pushing against the exhaust. Exhaust comes out of the rocket at very high velocity. This means that most of the energy in a conventional rocket goes into accelerating the exhaust, and only a small amount is available to accelerate the payload.

The other major advantage is that the fuel supply can remain on the ground, and does not need to be accelerated. In a conventional rocket, the first stage, for example, needs to accelerate not only the payload, but all the fuel in the second and higher stages.

If people are interested, I can supply some math.

The two top sections of the loop would be separated enough that you could connect a capsule to only one of them. Something on the order of a few hundred meters apart. Launching capsules would be connected at the West station to the West to East cable. They would accelerate by applying a magnetic field to that cable, and then release into orbit once fully accelerated. Landing capsules would have to match orbit with a section of the East to West cable near the West end. They would then decelerate by applying a magnetic field to that cable, and would be disconnected (after stopping) at the East station.

On a scale (like that of the diagram) where you could see the entire 2000 km loop, the (for example) 200 m distance between the cables going in opposite directions will not be visible, so it will look like they are not separated.

At least some of them do. There was an incident in September 2008 where automatic trading programs mistakenly responded to an old newspaper article (from 2002) about the bankruptcy of the parent company of United Airlines. The stock dropped from about $12.50 to $3 a share in 15 minutes. You can read reports of the event on Slashdot, Reuters, and many other news sites.

The relevant statistical concepts are the following:

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True positive (TP)- The person really is a terrorist, and your test detects him (I'm going to use the male pronoun throughout to keep the language less cluttered)
False positive (FP) - The person is not a terrorist, but your test says he is
False negative (FN) - The person is a terrorist, but your test does not detect him
True negative (TN) - The person is not a terrorist, and your test correctly says he is not

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Sensitivity is the ability of the test to detect a true positive and equals TP / (TP + FN), or to put it another way, TP / (number of all terrorists, whether detected or not)
Specificity is the ability of the test to detect a true negative and equals TN / (TN + FP), or to put it another way, TN / (number of people who are not terrorists, whether the tests says they are or not)

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Generally in statistics, sensitivity and specificity are considered to be properties of the test, independent of the population it is run on, although this probably isn't strictly true in the real world.

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Positive predictive value (PPV) is the chance that someone who tests positive is really a terrorist and equals TP / (TP + FP), or to put it another way, TP / (all people who test positive, whether they are terrorists or not)
Negative predictive value (NPV) is the chance that someone who tests negative is really not a terrorist and equals TN / (TN + FN), or to put it another way, TN / (all people who test negative, whether they are terrorists or not)

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In these terms, the statement that the OP makes can be rephrased as: Even a test with good sensitivity and specificity can have poor positive predictive value if the frequency of terrorists is low.

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Example: Test is 99% sensitive and 99% specific. Terrorists are 0.01% (i.e. one in 10,000)
Consider 1,000,000 people. Terrorists: 100, not terrorists: 999,900
True Positives = 0.99 (sensitivity) * 100 (terrorists) = 99; False Negatives: 100 (terrorists) - 99 (true positives) = 1
True Negatives= 0.99 (specificity) * 999,900 (not terrorists) = 989,901; False Positives: 999,900 (not terrorists) - 989,901 (true negatives) = 9,999
Positive Predictive Value = 99 / (99 + 9,999) ~ 0.0098 = 0.98%

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Sorry about the lines that consist of a period, but my <br> tags were being ignored there, and I couldn't figure out a better way to insert blank lines to make the post more readable.

I am the OP. Read the post again. I offered the two alternative means of payment, and the Sprint Store Manager turned both of them down.

Both the store staff and I behaved like civilized adults during this discussion. The sales associate asked for my SSN. I asked if it was required, and when he said it was, I asked to speak to the store manager. The store manager confirmed the statements of the associate. I asked why the SSN was required, we had a conversation about that where I talked about the alternatives discussed in my OP, and the manager said those were not acceptable. I told her I would not buy the phone under those conditions and left.

The entire interaction took about 15 minutes, about half of which was spent actually talking to the manager. No voices were raised. I consider the store manager the appropriate escalation in this situation. If there is a need for further escalation, it's their job to figure out where to escalate to. In addition, it was a Saturday, so I doubt it would have been practical to reach anyone with more authority.

I did not have to give Verizon an SSN when I signed up for their service. I don't have records that show an exact start date handy, but I think they have been my carrier since the late 1990's.

Because I was reporting on my experience at one Sprint store. For me to say "Cellular Providers Require SSN for Contracts" would have required researching policies at a bunch of other companies.

I am a pediatric blood and marrow transplant physician and this is a question I am asked frequently. The decision is one in which a fairly significant amount of money (for most people) is being traded for a very small chance of future benefit. How much money you are willing to spend and how risk-averse you are will probably be the main factors influencing your final decision.

In my opinion, the bottom line is that for a family without any special features in the family medical history, the chances that a clinical scenario will occur in which having a stored cord blood unit from a baby, for the use of either that baby or a relative, is important are very small, but I can think of some. I have been involved in pediatric bone marrow transplant for 12 years (including training) and have not yet actually encountered such a scenario. The procedure involves no additional risk to the baby or mother during delivery, so that if collection and storage were cheap, then it would be easy to say to do it just in case, even though the chance it would ever be useful is very small. However, given the actual costs involved, in my opinion, storage of cord blood for private use is not cost effective compared to other ways that you can spend money to improve safety (for families with no special features in their medical history).

As other people have also pointed out, not every collected cord blood unit is actually usable. We recently had a case at my hospital where the parents had saved the cord blood of a sibling, but the number of cells in the saved cord was so low that we had to collect bone marrow from the sibling anyway.

Family medical history that would lead me to recommend collection would be a sibling who was diagnosed with a disease that can be treated with cord blood transplant (acute leukemia being the most common one). Because of the risk of relapse, this applies whether treatment is complete or not. A weaker indication would be a family history (or a prenatal diagnosis in the baby) of a genetic disorder that either can now or theoretically could be treated in the future with a cord blood transplant. This is much more hypothetical, but it is theoretically possible that the hematopoietic stem cells in the cord blood could be useful in a gene therapy protocol.

The (very sad if it ever actually happened) hypothetical scenario that I can think of in which a stored cord blood unit would be the most useful would be if a baby was born, the cord blood was collected and stored. That child subsequently died. At a later time, a sibling was diagnosed with a disease (like a relapsed acute leukemia) in which transplant is indicated. The stored cord blood unit was a match for the sibling and had an adequate number of cells, but no one else in the family was a match. Fortunately, the chances of something like this happening are very, very small.

Table lookup FTW!

Pregenerate the tables for each possible angle and code them as 512 byte data blocks at [sin table base address] and [cos table base address]

load register 3 with pseudo-angle
shift register 3 left ; i.e. multiply by 2 since sine and cosine results are 2 bytes long
load register 1 from [sin table base address], (register 3 value); this is the sine
load register 2 from [cos table base address], (register 3 value); this is the cosine

Last two instructions use the addressing mode that adds a register value to an absolute address to determine the final address.