Edward Ashton's Blog, page 10
November 19, 2016
Fun Science Fact #35: The EM Drive may be real. Take that, Newton!
So apparently, the EM Drive is maybe possibly real. NASA’s Eagleworks Laboratory has gotten a paper through peer review describing a vacuum engine that produces reactionless thrust. This appears to violate Newton’s third law (that whole “equal and opposite reaction” thing,) but there are some interpretations of quantum mechanics that might explain what’s going on. I don’t care so much about how it works, though. I’m an engineer. I want to know what we can do with it.
All known space drives (with the exception of solar sails) operate by throwing stuff out the back at high velocity. Thrust is then imparted to the vehicle in the same way that thrust is imparted to your shoulder when you fire a rifle. There’s a big drawback to this approach: pretty soon, you run out of stuff to throw out the back. As a result, there are very severe limits to how fast we can accelerate a space probe with conventional rockets. We can get out of the solar system (barely) but to reach the next nearest star at the velocities we can reasonably achieve would require a minimum of 50,000 years or so.
In order to do much better that this, we would really like a propulsion method that doesn’t require so much fuel, and which therefore allows us to work with much lighter probes—enter the EM Drive. It operates by bouncing microwaves around in a reaction chamber, which interact with quantum vacuum fluctuations in the blah blah blah blah. Bottom line: it generates 1.2mN of thrust for every kW of power you pump into it. What does that get us?
Well, this is actually a very small amount of thrust. Let’s assume we’re powering this engine with a 1MW fission reactor. These things are about the size of a trash can, and weigh roughly 500kg. Let’s assume also that we’re attempting to move something like the Cassini probe that we sent to Saturn a while back. Without fuel, that weighed about 2,100 kg. So, we have a total vessel weight of roughly 2,600 kg. Our 1MW reactor gets us 1.2N of thrust. How much acceleration does this produce?
Not much, as it turns out—0.00046 m/s2, to be precise. So, after an hour of continuous thrust, our probe would be traveling at 1.7m/s—a comfortable walking speed. This doesn’t seem all that promising, does it? However, because this engine doesn’t require reaction mass, we can leave it running as long as the nuclear reactor holds out. Marine reactors (the kind we put in submarines and such) can run up to 33 years without refueling. Leave our engine running for that entire time, and we’ve got our probe up to roughly 480,000m/s. That gets our travel time to Proxima Centauri down to only 2700 years! Don’t forget to pack a snack.
Okay, so that’s not great, but what if we scale up the power a bit? Thrust for this engine appears to rise linearly with the amount of juice we pump through it. So, replace our dinky 1MW reactor with the kind we use on aircraft carriers. Those are a bit heavier, of course (like 8,000kg instead of 500kg) but they also produce 700MW, which is quite a bit more power. Hook this up to our Cassini probe and we have a total vehicle weight around 10,000 kg, coupled with thrust of 840N (and yes, I know it’s a big assumption that thrust will continue to scale with power at these levels, but go with me on this.) Our acceleration is now 0.084 m/s2, giving us a maximum cruising speed of about 87,000,000m/s. Fun fact: this velocity gets us to Proxima in only 15 years! We can’t actually get to Proxima in that time, of course, because reaching this velocity takes us 33 years of continuous thrust. Also, we’d probably like to slow down at the other end of the trip. Zipping through the Proxima system at a significant fraction of the speed of light would make for a very anticlimactic trip. So, we accelerate for a while, shut down the reactor, then turn it back on and decelerate for arrival. At the end of the day, we’ve got a probe orbiting another star in about 40 years, give or take.
Again, lots of assumptions here. First, we’re assuming that our probe isn’t going to bump into anything during its trip, because a pebble at relativistic speeds has the kinetic energy of a nuclear bomb. Also, we have to make sure our Cassini probe has enough juice at the other end to get a signal back to us over four light-years. These are details, though. Also, on the upside, we could conceivably scale this up with multiple reactors and multiple engines to power something even bigger. Conceivably, something like this could get get humans to another star—I mean, as long as we don’t mind using babies for astronauts, we could possibly even get them there before they die!
Anyway, the bottom line is that the EM Drive, if real, is kind of a big deal. Stay tuned for further developments.
November 15, 2016
November 1, 2016
October 25, 2016
Edward Ashton: Not Just Any Three Days in April
Thanks for the shout-out, homie.
October 23, 2016
Fun Science Fact #34: Ranked-choice voting would not result in President Stein.
A few days ago, I had a chance to listen to a lengthy interview with Jill Stein, the Green Party candidate for POTUS. Most of it wasn’t too interesting, to be honest—lots of stuff about how Republicans and Democrats are just the same, a bit about how Hillary Clinton is planning to start a nuclear war in her first hundred days, and a pretty clear demonstration that Dr. Stein doesn’t understand what the term “quantitative easing” means. In and among the nonsense, however, was a suggested solution to the eternal third-party complaint that voters who really support their positions won’t vote for them because they’re afraid of throwing away their votes. We could have a viable third (and fourth and fifth, presumably) party in this country, Dr. Stein asserted, if only we’d adopt ranked-choice voting.
At this point, it’s probably a good idea to briefly explain what ranked-choice voting is. Also referred to as instant-runoff voting, ranked-choice voting allows you to vote for more than one candidate, ranking them in order of preference. If, for example, you love Jill Stein but are terrified of a Donald Trump presidency, you could vote Stein first, then Clinton, then Johnson, then Trump. Votes are tallied under this system by first counting all the first place ballots for each candidate. If anyone gets more than 50%, that’s your winner. If not, the last place candidate is eliminated, and everyone who ranked that person first gets re-allocated to their second-ranked choice. This continues until somebody achieves a majority.
The beauty of this system is that you can vote your heart, without worrying that your vote will doom you to the worst of all possible worlds. There are obvious benefits to that, and using this system would prevent third party candidates from acting as spoilers, as Ralph Nader did for Al Gore in the 2000 election, or as Ross Perot may have done for George Bush the Elder in 1992. But—would this allow those third party candidates to actually win?
The answer, for better or worse, is no. The reason that third party candidates can’t win in the United States isn’t because of our voting system. It’s because the thing that makes them third party candidates in the first place is that they represent minority positions. The reason Jill Stein has no opportunity to win the presidency is that her policies, while very appealing to a small subset of the electorate, are anathema to enough people that there is absolutely no way for her to cobble together a majority coalition. The same can be said of Gary Johnson, and Ralph Nader, and pretty much all of the other obscure protest candidates who launch quixotic runs every four years.
But wait—lots of other countries have many different political parties that actually succeed in putting people into office. What about them? Well, the difference is that those places generally are parliamentary democracies. In a parliamentary system, a party that gets 15% of the votes gets roughly 15% of the seats in parliament. Obviously, that’s not how it works in the U.S. Here, you actually have to win a majority within your district or state or, in Dr. Stein’s case, the entire nation, to take office. This is a winner-takes-all system, and it necessarily drives toward two dominant parties, because taking second or third or fourth place in this system gets you absolutely nothing.
This is not to say new parties can’t arise, of course—but to do so, they have to cannibalize and destroy one of the two existing dominant parties. That’s what happened to the Whigs in the 1850s. The key factor that has to be in place for this to happen, however, is that the new party has to better represent the mainstream of American thought than the existing party. It could have been argued a few years ago, for example, that there was an opening for a new party embodying a combination of fiscal conservatism and social tolerance, but the existing Democratic party seems to have more or less moved into that space during the Obama presidency. It is also possible that a new party may arise to better represent the center-right in the wake of the Trump candidacy. If this happens, though, it will mean the end of the current GOP.
Needless to say, neither the current Green or Libertarian parties as represented by Stein and Johnson are likely to fit this model. Both appeal to a narrow swath of voters (those who are very concerned about GMOs, and those who are really, really into weed, respectively,) and if the United States were a parliamentary democracy, both would probably pick up a seat or two, and maybe have a shot to weasel their way into a coalition with the winning party. As noted, though, that’s not how it works here. As long as the U.S. electoral system sticks with the winner-take-all model, we’re going to have to reconcile ourselves to making the best of two imperfect choices.
Will either of those choices ever perfectly represent your views? No, they will not. This is not a bug. It’s a feature. The United States is a large and diverse nation, and perfectly representing your views means perfectly not representing somebody else’s. If there can only be one winner in an election, everyone needs to compromise on something. Understanding that principle is not a sign of moral corruption. It’s one of the basic requirements of political adulthood.
October 14, 2016
Further evidence that our universe is actually somebody else’s video game: Hillary Clinton, after a...
Further evidence that our universe is actually somebody else’s video game: Hillary Clinton, after a lifetime spent driving towards becoming America’s first female president, has to overcome the most misogynistic troll on the planet in order to claim the prize. I half expect Trump to morph into Donkey Kong on the White House steps on November 9th.
October 6, 2016
Fun Science Fact #33: Common sense is common. That’s not a good thing.
I recently made the mistake of scrolling down into the comments section of an article I’d been reading. The topic was climate change—specifically, the role that improved fuel efficiency can play in slowing it down. In the article, the author noted that automotive emissions are particularly problematic because burning a single gallon of gasoline produces about twenty pounds of CO2.
As you can probably guess, the commenters jumped all over this. Clearly, here was evidence not only that global warming is a myth, but that the liberal stooges who believe in it are completely lacking in common sense. A gallon of gasoline, many commenters pointed out, weighs in at just a bit over six pounds. How can burning six pounds of fuel produce twenty pounds of waste? Ridiculous!
Well, this assertion is a bit counter-intuitive. It’s also 100% true. Gasoline is a hydrocarbon. It’s mostly made up of octanes, which are molecules containing eight carbon atoms and eighteen hydrogen atoms. When you burn gasoline, it reacts with oxygen in the air (this is why Elon Musk will be taking a Tesla with him to Mars) to produce two new types of molecule: carbon dioxide (CO2) and water (H2O). Note that each CO2 molecule contains only one atom taken from the gasoline. The other two come from the air. Note also that each oxygen atom is actually about a third heavier than each carbon atom. The result? Yeah, burning a gallon of gas produces twenty pounds of CO2, along with about nine pounds of water.
Okay, fine. Proving that internet trolls are dummies is like shooting fish in a barrel. However, common sense can be misleading to smart people too, often in subtle ways, and failing to recognize when you’re being misled can result in very bad outcomes. Here’s a favorite example of mine: some years ago, there was a push to require small children on airplanes to use car seats. Seems like common sense, right? I fly a lot, and I’ve experienced some pretty rough patches. I have a very vidid memory of my orange juice rising up out of my glass over Wisconsin once, hovering there in front of me for an instant, and then splattering all over my lap. I shudder to think what might have happened at that moment if I’d been holding a child, and hadn’t been paying full attention to her. Making parents buy seats for their kids might cost a bit of money, but surely it would save tiny, vulnerable lives.
Well, no. Fortunately, before legislation mandating child seats on airplanes made its way through the legislature, somebody actually thought to study what the net effects would be rather than just intuiting them. What they found is that if small children were required to purchase seats on commercial flights, the extra expense would prompt a certain number of parents to forgo flying, and drive where they needed to go instead.
This is where we remember that (again, counter-intuitively for many folks) flying is almost infinitely safer than driving. Because this regulation would force many parents onto the roads, the number of kids who would be saved from turbulence and rough landings would be vastly outweighed by the number who would die needlessly in auto accidents. Passing this common sense safety regulation would in fact cost lives, not save them.
The takeaway here is this: common sense is a fine and necessary thing. It allows us to make our way through the world without being paralyzed by the need to think through the ramifications of every tiny decision. However, in America in 2016, there is an unfortunate tendency to elevate common sense and intuition above actual knowledge. This tendency manifests itself in the increasing rejection of expertise in areas as diverse as climate science (Humans are changing the climate? Crazy!); economics (Free trade obviously hurts the American worker. Derp!); and even medicine (Who are you to tell me that my kid needs to be vaccinated?) Thinking for yourself is generally a good thing, but… this is a complex world, and there are people out there who spend their lives studying individual parts of it. Every once in a while, particularly on complicated topics, it might not hurt to listen to them.
October 1, 2016
Advice for Selling Short Fiction
1. Read some selections from the magazine or website you are targeting.
2. If you think the stories in that magazine or website are terrible, this does not mean the editors will be dazzled by yours and that you will have an easy sale. This is because:
3. Every magazine or website that pays anything at all is inundated with submissions, most of which are written by competent writers. As a result:
4. Pretty much all of them are publishing stories that their editors really, really like. If you do not like them, it almost certainly means that:
5. They will not like yours either. As a result:
6. If you want to be paid for your writing, submit it to markets that publish work that you would pay to read.
September 26, 2016
An excerpt from Hannah, Altered
“Hey,” I said. “Jordan? Can I ask you something totally random?”
He shrugged, and brought his nose down to his right knee.
“Sure, as long as you don’t mind a totally random answer.”
“Yeah,” I said. “I guess that’s fair. So… in the Stupid War, were there really people who backed the AIs?”
Jordan looked up from his stretch. He wasn’t smiling.
“It’s for an essay,” I said. “For Modern History. “
“Right,” he said. “Modern History. You know they don’t offer that class to freshies, right?”
In fact, I had not known that. Jordan sat up, rolled his neck around in a slow circle, and stretched down to his left leg.
“So,” he said. “Tara’s been talking smack about Devon Morgan, huh?”
I didn’t say anything. He straightened, and gave me a long, searching look.
“Yeah,” he said finally. “There were. I don’t think any of them made it to the end of the war alive, though. Devon’s family weren’t partisans like the UnAltered or the New Human Army. They just took a lot of shit over some stuff her parents said when NatSec started talking about doing a total network purge. Honestly, her dad came pretty close to getting himself lynched. There were all kinds of rumors—I mean, some folks even said they were harboring. The only thing anybody ever proved, though, was that he wrote an essay on one of the news blogs saying maybe NatSec shouldn’t totally wipe out what was basically a brand-new sentient species just because a few of them did some really bad stuff.”
He pulled one knee up, and twisted around to stretch his lower back.
“Anyway,” he said, “I hung out with Devon at States last spring. Whatever her parents did or didn’t do six years ago, she’s a good kid. I know Tara’s fired up about the meet yesterday, but dredging up that shit…” He looked over a Tara again. “That’s pretty low, even by her standards.”
Doyle called Jordan’s name from across the field. He sighed, and climbed to his feet.
“Look,” he said. “I know that sounded like I was shitting on Tara. I’m not. She’s a good kid too, for the most part. She just…” He looked over at her, then back at me. Doyle called his name again, a little louder. “Right,” he said. “Just watch your back, okay?”
September 18, 2016
Gluten Sensitivity: A Slightly More Ethical Update
A bit over a year ago, I posted the results of a medically and ethically suspect experiment in the area of gluten sensitivity:
http://smart-as-a-bee.tumblr.com/post/127878104652/gluten-intolerance-or-chemical-sensitivity-an
Now comes the NIH with a much more well-conditioned study of this subject:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3945755/
Interestingly, they come to essentially the same conclusion in their real study that I did in my bullshit one. The recent upsurge in what appears to be celiac disease (increasing from 0.7% of the general population to greater than 5% in North America in less than two decades) is not biologically plausible if we think gluten is responsible. The culprit in all this diarrhea is not in fact gluten. It’s glyphosate (sold as Roundup). American farmers douse their wheat fields with the stuff just prior to harvest in order to kill the stalks and desiccate the kernels, and as a result it winds up in our food supply in significant amounts.
My take? Whether you get sick after eating American wheat or not, this might be one area where it’s worth the extra cost to invest in organic food. Glyphosate doesn’t appear to be carcinogenic, which is why farmers are allowed to use it they way they do. However, even in people who don’t react strongly to it, glyphosate definitely alters the makeup of our intestinal flora. We don’t fully understand how our body interacts with this biome, but we know these interactions are important in a number of ways. This is probably one of those areas where discretion is the better part of valor.
