When I was in high school, I did a project on PRT — Personal Rapid Transit. It was the “next big thing” in transit and of course, 30 years later it’s still not here, in spite of efforts by various companies like Taxi 2000 to bring it about.

With PRT, you have small, lightweight cars that run on a network of tracks or monorail, typically elevated. “Stations” are all spurs off the line, so all trips are non-stop. You go to a station, often right in your building, and a private mini-car is waiting. You give it your destination and it zooms into the computer regulated network to take you there non-stop.

The wins from this are tremendous. Because the cars are small and light, the track is vastly cheaper to build, and can often be placed with just thin poles holding it above the street. It can go through buildings, or of course go underground or at-grade. (In theory it seems to me smart at-grade (ground-level) crossings would be possible though most people don’t plan for this at present.)

The other big win is the speed. Almost no waiting for a car except at peak times, and the nonstop trips would be much faster than other transit or private cars on the congested, traffic-signal regulated roads.

Update: I have since concluded that self-driving vehicles are getting closer, and because they require no new track infrastructure and instead use regular roads, they will happen instead of PRT.

Yet there’s no serious push for such systems…

Read on.  read more »

I’ll admit that female endocrinology is not something I know a great deal about, but I do know that most of the birth control pills today follow a general strategy of fooling the body into thinking it is pregnant. This stops ovulation and implantation.

It is also the case that certain types of stress, notably caloric restriction and extremely high levels of physical activity can also retard both ovulation and menstruation. In fact, young girls who are serious athletes often do not experience menarche until years later than ordinary girls. (On the other hand, for reasons not fully understood, the average age of menarche has been gettting significantly younger in recent decades.)

The evolutionary reason for the late menarche seems obvious — if times are tough, and food is scarce, it may be best to not have babies right then.

Anyway, there must be some hormonal signals which these levels of stress generate which trigger the reproductive system not to operate. My question is — might it be possible to mimic these signals, without other harmful effects, as a method of birth control and even menstrual supression?

Of course, we’re very interested in other ways to mimic the signals of caloric restriction without the actual restriction, since in all the animals tested so far, caloric restriction results in serious extension of lifespan and youthspan.