Monthly Archives: November 2016
And it isn’t even directly about Donald Trump. Or then again maybe it is.
Across numerous countries, including Australia, Britain, the Netherlands, New Zealand, Sweden and the United States, the percentage of people who say it is “essential” to live in a democracy has plummeted, and it is especially low among younger generations.
— Amanda Taub, How Stable Are Democracies? ‘Warning Signs Are Flashing Red’
This graph says it all:
Really. It’s the controversial Em Drive, and it’s NASA science and peer-reviewed and everything. Formally it’s called “Measurement of Impulsive Thrust in a Closed Radio Frequency Cavity in Vacuum” by Harold White, Paul March, James Lawrence, Jerry Vera, Andre Sylvester, Davis Brady and Paul Bailey.
An EM Drive produces thrust without fuel, instead using microwaves that bounce around a conical, enclosed device. According to the theory, the momentum of those bouncing microwaves is higher at the wide end of the engine, which means the whole system should experience thrust.
I don’t pretend to understand the pilot-wave theory that the authors of the new paper propose as an explanation, but I gather it challenges the Copenhagen consensus that has dominated physics for a long time — and makes quantum behavior a tiny bit less weird in some ways (double slit experiments would have an explanation I could understand) but at a price of making large pieces of the universe more likely to be connected in some odd way. Or something.
But this part I think I get:
Although this test campaign was not focused on optimizing performance and was more an exercise in existence proof, it is still useful to put the observed thrust-to-power figure of 1.2mN/kW in context. The current state-of–the-art thrust to power for a Hall thruster is on the order of 60mN/kW. This is an order of magnitude higher than the test article evaluated during the course of this vacuum campaign; however, for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2mN/kW performance parameter is over two orders of magnitude higher than other forms of “zero-propellant” propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the 3.33–6.67μN/kW (or 0.0033–0.0067mN/kW) range.
Yes, “for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements”.
Space! As long as you are not in a hurry to boost up to speed to get there.
I wonder if the Em Drive works equally well at relativistic velocities? Does thrust taper off if you are going faster relative to the pilot wave? (Does that question even make sense?)
UPDATE: Well, of course, it’s the Internet, so there’s an emdrive FAQ. And it seems you do lose thrust as you go faster:
Q. Why does the thrust decrease as the spacecraft velocity along the thrust vector increases?
A. As the spacecraft accelerates along the thrust vector, energy is lost by the engine and gained as additional kinetic energy by the spacecraft. This energy can be defined as the thrust multiplied by the distance through which the thrust acts. For a given acceleration period, the higher the mean velocity, the longer the distance travelled, hence the higher the energy lost by the engine.
This loss of stored energy from the resonant cavity leads to a reduction in Q and hence a reduction of thrust.
“I pledge to give to bigotry no sanction, to persecution no assistance. I pledge to work toward a world where everyone may sit under their own vine and fig tree, and there shall be none to make them afraid. A world that scatters light and not darkness in our paths, and makes us all in our several vocations useful here, and in due time and way everlastingly happy.”
1. Do not obey in advance. Much of the power of authoritarianism is freely given. In times like these, individuals think ahead about what a more repressive government will want, and then start to do it without being asked. You’ve already done this, haven’t you? Stop. Anticipatory obedience teaches authorities what is possible and accelerates unfreedom.
2. Defend an institution. Follow the courts or the media, or a court or a newspaper. Do not speak of “our institutions” unless you are making them yours by acting on their behalf. Institutions don’t protect themselves. They go down like dominoes unless each is defended from the beginning.
3. Recall professional ethics. When the leaders of state set a negative example, professional commitments to just practice become much more important. It is hard to break a rule-of-law state without lawyers, and it is hard to have show trials without judges.
UM Law alumnus Reince Priebus profiled in NYT Mag as Reince Priebus, Normalizer in Chief and in Miami Herald puff, Before making his name in politics, Priebus was a force at Miami law school . The Herald article includes this:
Without exception, more than half a dozen people interviewed for this story who knew Priebus during law school described him as affable, thoughtful and kind.
Andrew Moss, who was in the same first-year section as Priebus, recounted to a Miami Herald reporter an anecdote about going to grab a bite at Wendy’s with Priebus when they were working on a project. A homeless man lay outside. Priebus didn’t have much money, Moss said, but he bought two meals and gave one to the man.
Say what you will, he’s Trump’s least crazy appointee so far — by several miles. Whether he’ll have actual power with alt-right Bannon down the hall remains to be seen.
Google Takeout–I didn’t know this was even possible, but you can download a copy of your email, contacts, calendar, google drive, and indeed everything google, in .zip format. Alas there is no way obvious way to automate it. So do it right away, or you’ll forget.
Thank you to Stefan Krasowski for the pointer.