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Comment Re:Misconception about space "pollution" (Score 5, Informative) 41

Hey dude, it's a really nice visualization website done by a high school kid. Don't kill the buzz.

But now that you've diverted the topic, let me tell you that you're full of BS. doesn't show it, but space debris is a serious problem. shows the largest satellites, upper stages and debris chunks, but there are billions more pieces of debris that are too small to show on a website, but large enough to cause serious damage.

It really doesn't take much to damage a spacecraft. I have some experience with this: I've worked with two different spacecraft that experienced "micrometeoroid" hits that damaged sensitive equipment. But really, in low earth orbit, micrometeoroid means human-made debris. There are plenty of flecks of paint and fragments of silicon that can slice through delicate spacecraft apertures or pop a solar panel.

When we ran the numbers using NASA's best simulation of space debris at the time, we were horrified to find out the amount of 20-50 micron pieces of debris that had enough energy to puncture sensitive detector windows and films. And this simulation only had data from before the huge space collisions of the past decade, which have probably doubled or tripled the total debris load. In our plans for a new satellite project, a damaging hit by space debris was one of the serious factors limiting mission lifetime.

And no, most of the debris will not de-orbit. Yes, anything within 600 km or so altitude will likely be affected by atmospheric and solar drag and re-enter within our lifetimes, but there is a huge orbital phase space where debris will essentially be stuck there forever. NASA requires its missions to have a debris mitigation plan.

So, thanks for poo-pooing space debris. Some high school guy's website sure was a great soapbox for you to tear a straw man apart.

Comment Re:Sloppy language (Score 4, Interesting) 58

Actually, yes, black hole *systems* go dormant. The system consists of the black hole itself, but also an accretion disk orbiting the black hole, and also an orbiting donor star which is providing a relatively steady flow of matter to the outer part of the accretion disk.

Matter can stay there, in the accretion disk for a year, tens of years, or thousands of years, until enough mass density builds up. At that point, an accretion disk instability turns on and you get a transient outburst, and then it will take a few months to flush out the disk.

Google for "dwarf nova instability."

Comment Re:The real importance of the event (Score 2) 58

Well yes and no. There are probably hundreds of thousands of these systems, lying dormant, in our galaxy. Each one is probably fed by a nearby orbiting donor star, that transfers matter in a slow trickle to an accretion disk which surrounds the black hole. The material kind of stays there, dormant, in the disk. When enough density builds up in the accretion disk, there is an hydrodynamic instability that causes flow to suddenly turn on. This will flush out the disk, the system will eventually turn off after a few months, and then it will lie dormant again. The time scale for recurrence could be a year, it could be thousands of years; it kind of depends on the mass transfer rate from the donor star and the mass of the black hole. There are typically tens of black hole outbursts per year in our galaxy, but V404 Cyg is one of the brightest known.

Comment Re:I hate the term "awakens" (Score 4, Informative) 58

Actually the term is appropriate. Gravity doesn't disappear, but material can orbit the black hole in an accretion disk, in a dormant state. When enough material builds up in the disk, accretion flow to the black hole can activate. It's called an accretion disk instability. In the astronomy business we would say the black hole has become active, or is having a transient outburst, but awaken is fine for public consumption.

Comment Re:Maybe science went off the rails... (Score 1) 444

Yes, astronomy. Biomedical definitely has different protocols, but stricter statistical requirements, I'm not so sure.

Astronomy has its own weirdnesses. There is only one universe: we don't get to repeat our experiment independently. So one needs to be careful about statistical tests based on a limited sample. It doesn't mean work is impossible, but the statistics need to be understood.

Comment Re:Maybe science went off the rails... (Score 4, Informative) 444

I work in a science field. I have *never* seen "truth" or "fact" set by polling. Scientific controversy exists and disagreements exist. Researchers attempt to use carefully designed experiments with measurements to resolve those disagreements. Fringe researchers get a voice, and once in a while, an "out there" idea does pay off. I have attended many conferences where unconventional theories were presented.

However, when conveying scientific results to the public or policy makers, discussing what is consensus and what is not consensus does make sense. For that purpose, we as scientists and public trust holders shouldn't let the fringe distract us from our best understanding of the world. Because 99.99% of those fringe ideas are pretty much junk.

Science does permit challenges to existing models. But in most cases those challenges will have an extraordinarily difficult time of it. Difficult, not because of some kind of popularity contest. The current best models are there for a reason. They have survived knock-down fights with other models. They have been run through multiple experimental gauntlets. Theoretical models usually have multiple consequences and these consequences can be tested in multiple, cross-linking ways. A new model can be proposed, a new way of thinking put forth, but the burden is upon the proposer to show how this new way is consistent with all previous experiments. Fringe theories should not get a free pass because they are new or fringe.

Comment Re:Academic la la bullshit. (Score 1) 258

This. Anybody who remembers the IBM DeskStar (a.k.a. DeathStar) debacle will remember that drives from certain batches would fail on a weekly basis. To get better independence, one would need drives in the same RAID from different manufacturers, and hopefully, from different batches.

Comment Re:Can someone who knows about astronomy fill me i (Score 2) 129

A paper by Bailey et al. is here...

The age is estimated from the primary star. Presumably the system formed all at the same time, star and planet together. (It's difficult to gain a planet in some other way, such as "capture," especially in such a short period of time since the star's birth.)

The planet's mass is estimated from the brightness and color of the planet. HD 106906 b is a rare case where the companion can be resolved from its primary so a spectrum can be measured. Known models of planet brightness can be used to work backwards from the brightness and color to get mass.

Distance is usually a hard one to solve, but in this case the star is bright and Hipparcos has a distance derived from parallax. A distance of 92 parsecs means that the annual parallax is 1/92 arcsec. For comparison the moon is 1800 parsecs in diameter.

Comment Beautiful, but somewhat disappointing (Score 2) 172

The actual design of the building is beautiful and marvelous.

But I have to say that the entire design of the campus is a little disappointing. The buildings on campus are completely isolated from the rest of the city of Cupertino. The campus will be separated by a new security wall/fence surrounding the perimeter that will prevent all unauthorized entry, and most of the buildings will be hidden behind substantial landscaping. The plan also demolishes a city street that will disturb local automotive and bicycle routes.

Apple workers will get to appreciate the beauty of the architecture, and the calmness of the natural park-like setting, but the public will have to gaze from a distance.

I think Apple had a chance here to integrate the campus more closely with the city, and the city had an opportunity to ask for more of a community feeling than an ivory tower feeling. What if the park-like portions of the campus were an actual public park? The public could appreciate the architectural wonder and feel that the campus was at least a little bit a part of their city. What if the campus had more walking-friendly routes to and from the rest of the city, to encourage interaction between workers and local businesses? Facebook did this, by basically buying a little mini-city ( which integrates work and life elements. You'd get a better city, quite frankly.

Comment Re:It's not "bells and whistles!!!" (Score 1) 177

You ordered just one Protect?

Most fire codes require a smoke detector in each bedroom, each hallway outside a bedroom, and on every level, and sometimes near kitchens and bathrooms. If you have an efficiency apartment, I guess you only need one alarm, but most homes are going to need at least 3, maybe a lot more depending on number of bedrooms and layout. At $129 per device, that starts to add up cost quickly.

A sine curve goes off to infinity, or at least the end of the blackboard. -- Prof. Steiner