Once a black hole is formed, all that matters is mass, angular momentum, and net charge.

And (if dark matter has one or more long-range dark-matter/dark-matter interaction forces, as baryonic matter has electric charge), the "charge" analog(s) for that/those force(s).

Dark matter doesn't interact with baryonic matter, except gravitationally. OK, fine. Does it interact non-gravitationally with other dark matter? Who knows? Maybe, maybe not.

It would, of course, interact with other dark matter gravitationally. And that means that it can fall into clusters if its particles can lose their relative velocities. Harder to do without other interactions to provide friction, but still possible.

But once it's clustering, if enough of it clustered it would form a black hole just fine. Further: Dark matter could fall into a (primarily full of baryonic matter) black hole and help mass it up, and similarly baryonic matter could do the same with a black hole mostly full of dark matter. And two could spiral in and combine, radiating gravitational waves (to provide the friction), just fine regardless of what kind of matter predominated in each' formation or current composition. Once a black hole is formed, all that matters is mass, angular momentum, and net charge.

Seems to me that, with dark matter allegedly making up most of the mass of the universe and now appearing lumpy rather than just cloudy, cosmologists need to examine the implications of the capture of this matter's mass in black holes - and also its escape as a component of Hawking radiation.

What's the supposed advantage of Daylight Saving Time? Less power used for lighting.

But even a few decades back, before even CFLs, it had been shown that the higher air conditioning loads from people arriving home earlier, overwhelmed the alleged savings. Daylight Saving Time was a net loss. Now, with incandescents, arc lamps, and CFLs being replaced by LEDs (at about a 10x energy saving from incandescent bulbs), lighting is a drop in the energy bucket.

But if the government INSISTS on resetting the clocks twice a year...

Why save sunlight in the SUMMER? You have EXTRA sunlight in the summer ALREADY. What you're short on is DARKNESS. One of the main effects of universal DST was the death of the drive-in movie, and the need to get to sleep in order to get up for work so early severely limits the ability of people (especially young lovers) to contemplate the beauty of the evening sky in the outdoor comfort of the end of a summer day.

So I propose we preserve this precious dark time by turning the clocks BACK in the spring and FORWARD in the fall. I call this Nightlife Saving Time.

Party on!

Moore's law has a long way to go - into the third dimension, until the vertical layers of circuitry, power bus, and interconnect fill the buildable space or are no longer able to be powered and cooled. Currently we have a few layers in some memory but mostly that's it. At tens of nanometers for feature size, going to 3-D could get you close to another 80 years before you get to your FIRST meter of thickness.

You no longer get a free ride on single-threading speed from using smaller transistors closer together (though you get some improvement by arranging them in 3-D so the signals have less distance to travel). But there are some computations that are VERY parallelizable. (Organic-style artificial intelligence should be one of them, as it seems to run on mainly digital circuitry with a clock speed under 20 Hz.) For those, throwing additional gallons of processors at the problem should continue to work.

'way back in the late '60s, when the buzzwords were small- medium- and large scale integration, I described a thought-scenario I called "Preposterous Scale Integration": A three-D integrated circuit technology concept:

  - Diamond for the semiconductor. (It is VERY conductive for heat, which helps keep it from cooking itself. This is good, because the bandgap is about 5 volts...)
  - A six-foot cube of it. (These days I'd use the size of a '60s IBM mainframe cabinet - just small enough to fit into a standard elevator, thanks to Amdahl having seen Univac having to tear out a wall to get their machine into a computer lab - with the prospect of tearing it out again to remove it some years later.)
  - Power and cooling to two opposite faces (using water-cooled silver bus bars.
  - The remaining four faces paved with firber-optic I/O diodes - until the big diamond is "covered in hair". 144 square feet of fiber optics represents a LOT of bandwidth.
  - In a glass container filled with an inert gas - so you can run it up to orange-hot without it catching fire.

(Part of the fun of the scenario was to build something you'd expect to see in one of E. E. Smith's golden-age S.F. spaceships... B-) )

This wasn't intended to be built as described, of course, but to get a rule-of-thumb estimate of the scale of computing devices that might be possible and still useful enough to build.

(I have some ideas on how to get something that big to actually work, rather than fail due to manufacturing flaws. But I'll keep those to myself: They might actually start being useful enough to patent as we start bumping into the quantum size limits and have to stretch out into thickness.)

Some similar effects occur with engineering and programming. For instance:

An engineer is ALWAYS working on something that's broken. That's because, when he gets it fixed, he moves on to the next thing that's broken. (It's like the thing you're searching for always being in the last place you look. It's not Murphy's law, It's becaue, when you find it, you stop looking.)

A good programmer doesn't come to a problem with all he needs to solve it. Instead he comes to it with a big toolbox, SOME domain knowledge, and the skills needed to learn the rest during the project. This will be mostly stuff related to the project, but may include more programming tools as well.

Designing/architecting a program or system is like handling a black bag with the solution inside, in the form of blocks connected by strings. You squeeze it around until you get it into two lumps with very little string running through the thin neck. Then you it into two bags and document all the strings that went through the cut. Repeat unti the bags are small enough to understand easilyj and keep the entire explanation in your head. (In the case of a program that means the code itself fits on a page, with over half of the page being comments.) Then you can open the little bags and grok each one - which by now will be either trivial or maybe embody a single deep concept or "neat hack". (But avoid "neat hacks" if they're not obvious or if something straightforward does the job just fine.)

... in fact all we know is what is too much radiation. Back in the 50's and 60's a group of scientist were asked to provide safety information on radiation and they came up with a scale using the points of zero and you aren't gonna see the end of the week. They then drew a linear line between these points because they had little to go on, and presented it as a best guess and further research was needed to prove it's truly linear, exponential, logarithmic, or what-have-you. Since then the linear graph has become kind of dogma and various groups have picked various points across it to set their safety thresholds.

Excluding issues for your future offspring, the hazard from low-level long-term radiation exposure is primarily increased cancer risk. IMHO that's normally an integer power law, with the integer dependent primarily on the type of cancer (and secondarily on whether you have an inherited tendency toward that cancer type.)

Excluding a few oddballs (such as when TWO lines of tissue foul up to produce each other's growth factors), cancers consist of a cell line where several mutations have changed the cell's behavior into continuous reproduction, non-suicide, and immortalization (keep resetting the telomere clock). That typically takes the form of hits to a specific small target in the genome (the gene itself, some particular part of it, or its regulator) for each change.

In mature tissues (where ongoing cell reproduction is nearly stopped) that means one cell "Hitting the jackpot" by getting ALL of the necessary hits, independently. The probability of getting them all is proportional to the product of the probabilities of each hit, and the probability of each hit goes up linearly with the radiation level, so the probability of getting the set of N goes up with the Nth power of the radiation level. (This ignores quibbles, such as ordering if some hits start slow growth, and not getting some other damage that kills the cell.)

You can estimate N by looking at a log-linear graph of cancer incidence versus age. Cancers that behave this way will have a straight line with integer slope, where the slope gives the number of mutations you need. (One type of lung cancer, for instance, behaves this way and has a slope of 6.)

If this model of radiation response is correct, the model extrapolated down linearly from high level exposure ENORMOUSLY overstates the danger of low level exposure.

(Trying again with paragraph breaks. B-b )

Back in 1973 I made it to my first NCC (the AFIPS National Computer Conference - the annual big industry shindig in those days). At that time Moore's law was quite the buzz. Memory chips were still following it, but complex function chips were starting to fall off from the straight line on the log graph.

At that time there were a few microprocessors out. But it was far before the stage where you could put a microprocessor on every device control card. Most such functions - including the "glue" around the microprocessors themselves - were constructed of small-scale integration chips. Support chips were starting to graduate from things like four independent gates, a couple flops, or a multiplexer per package. But chips were essentially all still being designed by silicon manufacturers. A few might have been done under contract with companies designing boxes. But most were based on the semiconductor companies' marketing departments' guess at what would be wanted a couple years in the future.

I realized that one explanation for the shortfall might be that, as the complex function chips became larger, the engineering of more of the circuitry was moving from the system designers - including the garage and venture-financed startups - to the semiconductor manufacturers. This reduced the number of engineers on the job and their connection to the needs of the final products. Further, it changed the incentives on the engineers, making them more conservative (since they needed to keep an established company in business rather than take risks to establish a new venture or product).

There was a panel with several of the silicon companies that discussed the problem. Come the Q and A session I brought up the above, and proposed a solution: That the silicon companies license their design tools to the system designers and build the chips THEY design. That way the complex-function engineering, along with its risks and costs, could be moved back to the ventures, while the silicon companies could concentrate their engineering on what they do well - improving the process. And I asked whether any of their companies would consider such an approach. (I thought of it as a "silicon breadboard", but I don't recall actually using the term in the question.)

At least three of the companies' representatives - Mororola, Intel, I forget who else - said that there was no way they would ever do such a thing. (The Motorola guy was quite emphatic about it.)

And the guy beside me gave me his card and suggested I interview with him. (He was from Signetics, which was already doing a mask-programmed gate array chip which the customer could customize. I DID interview with him - and to this day I kick myself for not taking a job there. It would have gotten me out to Silicon Valley 12 years earlier, two years before both the release of the Altair 8080 and the founding of the Homebrew Computer Club. B-b )

A few months later that year, IBM announced they'd make their design tools available to customers and would fabricate chips under contract. Over the next couple years several other manufacturers followed suit. One of them transitioned from custom silicon design to tool licensing as a business and several others started up just to do tools. For a while it was known as the "silicon foundry" system. Now it's ASIC (application specific integrated circuit) design, there are standards for the major design languages, and a whole ecosystem of manufacturers of chips and of computer-aided design tools for all stages of the process.

And ASIC design is what I do for a living since I went back over to the hard side of the force in the early 1990s.

Back in 1973 I made it to my first NCC (the AFIPS National Computer Conference - the annual big industry shindig in those days). At that time Moore's law was quite the buzz. Memory chips were still following it, but complex function chips were starting to fall off from the straight line on the log graph. At that time there were a few microprocessors out. But it was far before the stage where you could put a microprocessor on every device control card. Most such functions - including the "glue" around the microprocessors themselves - were constructed of small-scale integration chips. Support chips were starting to graduate from things like four independent gates, a couple flops, or a multiplexer per package. But chips were essentially all still being designed by silicon manufacturers. A few might have been done under contract with companies designing boxes. But most were based on the semiconductor companies' marketing departments' guess at what would be wanted a couple years in the future. I realized that one explanation for the shortfall might be that, as the complex function chips became larger, the engineering of more of the circuitry was moving from the system designers - including the garage and venture-financed startups - to the semiconductor manufacturers. This reduced the number of engineers on the job and their connection to the needs of the final products. Further, it changed the incentives on the engineers, making them more conservative (since they needed to keep an established company in business rather than take risks to establish a new venture or product). There was a panel with several of the silicon companies that discussed the problem. Come the Q and A session I brought up the above, and proposed a solution: That the silicon companies license their design tools to the system designers and build the chips THEY design. That way the complex-function engineering, along with its risks and costs, could be moved back to the ventures, while the silicon companies could concentrate their engineering on what they do well - improving the process. And I asked whether any of their companies would consider such an approach. (I thought of it as a "silicon breadboard", but I don't recall actually using the term in the question.) At least three of the companies' representatives - Mororola, Intel, I forget who else - said that there was no way they would ever do such a thing. (The Motorola guy was quite emphatic about it.) And the guy beside me gave me his card and suggested I interview with him. (He was from Signetics, which was already doing a mask-programmed gate array chip which the customer could customize. I DID interview with him - and to this day I kick myself for not taking a job there. It would have gotten me out to Silicon Valley 12 years earlier, two years before both the release of the Altair 8080 and the founding of the Homebrew Computer Club. B-b ) A few months later that year, IBM announced they'd make their design tools available to customers and would fabricate chips under contract. Over the next couple years several other manufacturers followed suit. One of them transitioned from custom silicon design to tool licensing as a business and several others started up just to do tools. For a while it was known as the "silicon foundry" system. Now it's ASIC (application specific integrated circuit) design, there are standards for the major design languages, and a whole ecosystem of manufacturers of chips and of computer-aided design tools for all stages of the process. And ASIC design is what I do for a living since I went back over to the hard side of the force in the early 1990s.

Speaking of "doing my bit for human communication", let's try that with the formatting set to "plain old text". And preview it, too. B-b

As long as people are claiming things, I claim the invention of the "Bearded Bulletin". This is the hardcopy bulletin-board posting with a fringe of precut tear-offs with contact information (typically a phone number and a word or two to indicate what this particular one is about).

This occurred in the winter of about 1969 or 1970. (I could go through some old records and figure it out exactly.) I was in Ann Arbor at the time and needed to move to Lansing and sublet my current apartment.

I first went to the University of Michigan's Student Union housing bulletin board to see if anybody was looking, before making my own posting. At that time I noticed that the contact information had been torn off from many of the postings there (rendering the remainder useless B-( ). One poster had taken this into account and defended by writing the number along the bottom of the 3x5 card four times.

So I decided to turn a downside into an asset. I made up my posting, wrote the phone number repeatedly along the bottom in "landscape mode", and precut the entries into a fringe so they'd be easy to tear off without destroying the main message or the other tear-offs. It was intended to emulate printed postings with the pad of tear-off coupons, but much more cheaply. And I figured that a dozen or so tear-offs would be more than enough. (If they were all torn away at least one should produce a hit.)

I made up maybe 4 of these and posted one on the student union housing board and the others in similar places. And I checked it daily to make sure the bulletin didn't get buried or taken down and lost.

Next day there was another like it.

Day after there were four.

By the end of the week more of the new postings used the technique than didn't.

And of course the meme had spread to the OTHER bulletin boards, too. Like the next one over - the "ride to other cities" board.

This was just before a major holiday (Thanksgiving, I think, though it might have been Christmas.) I figure the college students hitching rides cross-country or going home on vacation spread it to other campuses across the country (and world) within a matter of weeks. (I know it was pervasive at Michigan State in Lansing by mid-January.)

So I figure that, even if nothing else I ever do or did is useful or long-lasting, I've definitely done my bit to improve the technology of human communication with that one invention. B-)