Wile_E_Quixote

Passing away on June 3rd, 2018, Georg von Tiesenhausen was the last of the original German rocket scientists that came to the United States with Wernher von Braun.

He is also presumably responsible for #29 and #30 of Akin's Laws of Spacecraft Design:

29. (von Tiesenhausen's Law of Program Management) To get an accurate estimate of final program requirements, multiply the initial time estimates by pi, and slide the decimal point on the cost estimates one place to the right.

30. (von Tiesenhausen's Law of Engineering Design) If you want to have a maximum effect on the design of a new engineering system, learn to draw. Engineers always wind up designing the vehicle to look like the initial artist's concept.

After vacuuming up a bunch of purple urchins, would it be possible to alter their DNA to be more like that of red urchins? Then release those genetically modified urchins back into the ocean to pass their “red-shifted” traits into the greater purple urchin population.

I realize there are plenty of ethical issues surrounding an attempt at genetically modifying an entire species. Perhaps doing so would be irresponsible? It’s not my area of expertise.

Looking through the recent Wall Street Journal A. Pasztor headlines that you've linked to, it seems Northrop Grumman has also been having production issues with the James Webb Space Telescope satellite. Upon further search, I haven't yet seen any articles claiming that the issues are technical mistakes, only that they were "avoidable".

Not a great PR month for NG.

Sure, the article describes the Coriolis Effect. But only as a part of a larger narrative analogy describing how two groups of people can each be entirely convinced that they are right and that the other group is delusional. Each group has a different frame of reference.

My best summary: In order to understand the conclusions of another group of people, one must first be willing to experience the world as they do.

I wasn’t too surprised about getting downvoted. I suspected that some might find “the solution is simple” a bit brazen, but I wasn’t sure how old the thread was, and wanted to draw some attention and critique before the thread died. My next line was more honest “I suspect that the reason…”. :-)

As for why a curling stone is different than a beer bottle or upturned glass on a table, that wasn’t the goal of my thinking. I was only trying to explain the curling stone. In any case, while having some similarities, the two scenarios are still pretty different. As laxd points out below, the beer bottle and glass have higher centers of gravity which make the “leaning forward” line of thinking seem more reasonable.

As for the effect of pebbled ice, it seems reasonable that the difference between the static friction coefficient and kinetic friction coefficient is greater for pebbled ice than for smooth ice. And if static friction and kinetic friction are approximately the same for smooth ice, then this effect would not contribute substantially to curling on smooth ice.

This was a fun problem to think about. I had hoped that a smarter physicist would tell me why my hypothesis was bogus. As a friction expert, Nyberg almost certainly entertained this idea at some point. I may send him a message to see what it is that I’m missing.

THE SOLUTION IS SIMPLE

I suspect that the reason curling stones curl the way that they do is primarily due to one side of the stone being subjected to “static” friction while the other side experiences “kinetic” friction. This would also explain why the curling doesn’t start to happen until the stone’s linear velocity has sufficiently decreased.

If a stone is moving down the ice, away from the observer, and spinning to the left (that is, counter-clockwise when looking down on it), the right-side edge of the stone is moving in the same direction that the stone travels while the left-side edge of the stone is moving in the OPPOSITE direction that the stone travels. This means that the right edge of the stone is moving faster across the ice than the stone’s linear velocity. And the left edge of the stone is moving slower across the ice than the stone’s linear velocity.

As the stone’s linear velocity decreases, there will come a point when the left edge of the stone is no longer moving relative to the ice, while the right edge of the stone is still moving at 2 times the stone’s linear velocity relative to the ice. This means the left side of the stone is now being subjected to static friction while the right side is only being subjected to kinetic friction. The force opposing the left side of the stone is greater than the force opposing the right side of the stone, causing the stone to pivot around the left edge of the stone, “curling” to the left, until the stone's linear velocity reaches zero.

I believe you mean 'just' $1.5B.

Still a nice chunk of change, but order of magnitude less.

I think it would be interesting to have a "swap" button between the start and end points, perhaps just under where it says "to". (similar to the swap buttons in translator apps and GPS apps to quickly swap the start and end points) As some other comments have mentioned, the paths are not necessarily the same route or length, and it is fun to see how they might be different.

It seems that improving the annealing process of printed parts from current 3D printers could, at best, reach the maximum crystallization of pure stereoregular PLA polymers.

Due to the two enantiomers of lactic acid, there are four different PLA polymers with different stereochemical structures: PLLA, PDLA, racemic PLA (PDLLA), and meso-PLA. It is only the the PLLA and PDLA stereoregular polymers that show crystalline characteristics. However, research indicates that mixing the PLLA and PDLA polymers allows the formation of a stereocomplex that has a much greater degree of crystallization. Note that this is a physical mixture of the two stereoregular polymers rather than a polymerization of the two lactic acid enantiomers, so the PLLA/PDLA stereocomplex (greater crystallization than either of the PLLA or PDLA polymers) is very different than the PDLLA polymer (which is amorphous, meaning non-crystalline).

Perhaps what we need is a 3D printer that uses one PLLA filament and one PDLA filament. The two filaments would be melted and combined in the nozzle of the printer. As the mixture of the two polymers annealled, allowing the stereocomplex structure to form, the resulting material might have mechanical properties that are superior to either of the parent filaments.

If anyone is interested in how modern versions of these machines work, the annual conference for the American Association of Physicists in Medicine (AAPM) is currently proceeding at the Walter E. Washington Convention Center in Washington, DC, and will continue until Thursday, August 4th. It's the largest international gathering of medical physicists in the world. If anyone is in the area and interested, you shouldn't have much trouble sneaking in and taking a stroll through the vendor area where you can see examples of the newest technologies in imaging and therapy physics. Just dress business casual and you'll blend right in with the other couple thousand physicists.

I'm not sure the pain-in-the-back argument is necessarily true. Even for many upright refrigerators, you must still bend over or crouch to get things from lower shelves and drawers. I've never felt inconvenienced removing things from my chest freezer. Also, my chest freezer has some sliding racks that make it great for organizing its contents. It seems possible that the pain-in-the-back argument is great for marketing, because it sounds like there could be some truth to it. I would argue that a person that has back trouble would likely only be able to use the chest level shelves in fridges, but they could just as easily use the top level racks in a chest freezer.

My guess for why traditional upright fridges could be seen as more convenient is because they take up less floor space for the amount of volume they provide. Also, upright fridges would be easier for small/short children to access. If floor space is less of a concern, and there is no need for small children to access the fridge, a chest-freezer-style fridge sounds like a brilliant idea. Next time I need a new fridge, I will seriously consider this as an option. Perhaps by then some contrarian manufacturers will realize how much sense this makes and I won't even need to convert a freezer myself.

I do not own Facebook stock, HTC stock, or any other stock associated with VR tech. Also, I do not own any VR systems or have any current plans to buy one.

I was just surprised at Oculus’s reversal. It seemed to be a generally bad business decision for Oculus, as well as a loss for VR developers. Certainly, this is a victory for HTC and other VR hardware competitors. It is also a short-term victory for non-Oculus VR hardware owners. They now get access to some existing content without having to buy a new system. But longer-term, if developers are less motivated to work in the VR space with no hope of negotiating a exclusive contract, I’m not sure the decision is such an indisputable victory for consumers.

I think sergiosgc's thoughts are on the right track "Dividing the market would definitely cause prospective consumers to wait for market stabilization. It is a risk bigger than the risk posed by competitors.” Oculus clearly saw some other risk as being greater than that posed by competitors. But I’m not sure risk of dividing the market or slow market growth are what Oculus was worried about. Dividing the market and slower market growth are both certainly better (for a business) than your competitor getting the majority of the market, which seems much more likely now.

Also, I understood why Vive owners/loyalists would be upset by Oculus-exclusive content. Haters gonna hate. But it didn’t make sense why the VR community in general would be upset. Seanp2k2 mentions in a comment further down “broke promises about DRM”. I am not familiar enough with this controversy to confirm or disconfirm such promises, but if Oculus explicitly promised that they would not prevent their content from being used with other hardware, then breaking those promises would certainly be a risky move. The outrage would at least seem more justified. My guess is that this was the risk that was greater than the risk posed by competitors, and that Oculus underestimated it.

-Early adopters take considerable risk when buying new hardware. If the market ends up crowning a different system king, your options are: Accept that objectively/subjectively superior technology isn’t the only thing driving sales and adoption. Or be a sore loser (which I’m not admonishing; VR tech is expensive) and complain loudly on message boards.

-I doubt that what Microsoft chooses to do with Xbox games in the future is due to regret or guilt about past decisions regarding exclusive content. Halo served them quite well at the height of the console wars.

-If I’m a dev making VR content and I am doing it to make a living, not just to make something cool to show my friends or as a fun project, my dream is that a VR hardware manufacturer pays a premium for exclusive rights. The hardware manufacturers can currently afford to pay more for exclusive content than they can hope to actually earn from the content, simply to drive hardware sales and platform adoption. I suspect it will be rough for developers, especially small teams, that are unable to negotiate exclusive deals. They will need to optimize and maintain their content for multiple platforms. And what can they hope to earn? <50,000 units in the wild, ~$25 per title Without an exclusive deal, it looks a lot like the movie industry. You either make a hit and do well, do really bad an move on, or worse, you do kind of okay, and then feel obligated to maintain the games and support the few that bought your game for the next few years.

-Exclusive content makes sense for many businesses. Doing it flawlessly, without causing potentially debilitating PR backlash is clearly easier said than done.

I think your argument is a great defense for whichever VR company ultimately secures a near-monopoly on this market. “Your Honor, my company is really just a fancy monitor company. We are actually in close competition with dozens of monitor and television manufacturers. We don’t have anything close to a monopoly.”

Again, I don’t believe VR hardware is in the same category as most PC peripherals, including monitors. The hardware could easily be marketed as a standalone system if the more traditional PC hardware was put into a pretty box and sold with it. The system would just cost $1k-2k more and few would be able to afford it.

If I was a traditional monitor manufacturer and I created some kind of magical new content for traditional monitor viewing that people would be willing to buy a new monitor to experience, I would definitely try to make it exclusive. Though I’m not sure the best way to do that would be a proprietary port.

Content has almost always sold hardware in the video game industry. Look at all of the exclusive content for Nintendo consoles. Or how many people bought XBox's for the sole purpose of playing Halo.

Sure, most VR hardware options may technically be peripherals for PCs, but at a cost of several hundred dollars or more, it isn't in the same category as PC mouses or joysticks. The way I see it, VR hardware is essentially a standalone device that connects to PCs, simply so that many people won't need to buy that too, saving them $1k-2k.

Creating exclusive games and buying exclusive content licensing/distribution rights for any gaming platform, especially ones in stiff competition for early adopters and the lion's share of a new market, is a great business decision. If Oculus hadn't secured exclusive content, people would have simply bought whichever hardware worked better, or shipped first. In this case, most people would have likely bought the Vive. Oculus knew that superior content is the tie-breaker and can even overshadow slight technological shortcomings, if they exist.

Oculus should never have reversed their plans to keep the content exclusive. Now, many people will just buy Vives and use them to play Oculus-subsidized content. Oculus could have created a great monopoly. Now I suspect they will have serious difficulty building a sustainable business. Peter Thiel is on Facebook's board and Marc Andreessen is on both Facebook's and Oculus's board. I can't imagine either one would support reversing the decision to make exclusive content.

Perhaps Apple should consider restructuring in a way similar to Alphabet. Take big risks within individually branded subsidiaries. If a subsidiary startup-like company fails, it disappears, and Apple can easily distance the parent brand from the failure. If a moonshot subsidiary wins, Apple wins too, and they've potentially created a new, valuable brand in the process.

Or maybe Apple should attempt a partnership with YC or some other incubator (or perhaps even start their own iNCUBATOR). Apple has lots of money. They need to take on riskier projects, but perhaps want to limit risk to public perception from failed projects. So they fund startups and compensate YC for vetting ideas and founder teams. In return, Apple gets equity and/or some kind of acquisition option. More startups get to be funded, with more ideas and founders getting tested, and YC reduces their risk of initial funding.

Making the claim "Radioactivity is good for them." without any additional qualification seems irresponsible. One might similarly claim that eating fried chicken and bacon everyday is "good" for someone because it makes them feel happy. Of course, this ignores the fact that doing so dramatically increases their risk of heart disease. Overall, this article seems to be written for the layman, where all forms of radiation are created equal (untrue). The research that the article describes may very well show that sustained low exposure to alpha particle radiation reduces symptoms of arthritis. It should stop there though rather than make judgement as to whether or not it is good or bad.

You're right, mostly. Considerably more data has been obtained from the fields of radiation oncology and medical physics about the effects of radiation on the body in the time since WWII. The main difference, I would argue, is that the article (as you also mention) is talking about alpha particle radiation. Most radiation oncology data comes from x-ray, gamma ray, and electron modalities. Heavy ions, including alpha particles, affect tissue rather differently. There is, however, a growing amount of data available from proton therapy and carbon therapy modalities.

Radiation therapy treatments are almost always fractionated, meaning the total dose prescribed by the radiation oncologist is spread fairly evenly across multiple days, typically 25-38 treatments for most disease sites. And since patients are rarely treated on the weekend, it usually takes 1 to 2 months for a patient to complete treatment. I don't know that I would consider 1 to 2 months a short time. There are some exceptions, such as gamma knife for brain cancer, in which the entire prescribed dose is delivered all in one session.

Also, radiation therapy is often used to treat not-so-small areas (volumes). For example, mesothelioma cases often require irradiation of the entire thoracic cavity. And if that isn't a big enough target for you, well, total body irradiation is actually a pretty common modality for certain, less localized, cancers originating in the blood and bone marrow. Both external beam irradiation (for mesothelioma) and total body irradiation treatments are always fractionated, generally delivering no more than 2 Gy to a patient in a single day, to give healthy tissue time to recover between fractions. Having said all that, you are right that this is still quite unlike the conditions presented in the article. Perhaps you would prefer studies analyzing the increased exposure of long-haul international airline flight crews.

I'm guessing this partially depends on region, and is of course partially dependent on both, but what is the primary factor limiting the lifespan of road surfaces: usage or weather (rain, snow, winter salt, etc.)? Certainly, there are some types of city infrastructure that deteriorate less from usage and more so from exposure to the elements over time (telephone poles, bridges, drainage systems). It seems that increased housing density would increase the amount of tax dollars for a given area of land without necessarily increasing the need for more roads or roadway area. One might argue that higher housing density means more cars, but if doubling the number of cars doesn't half the lifespan of the roads, then it's a win. Also, double the housing density doesn't necessarily mean twice the cars, because higher density regions are generally more walkable and there are greater opportunities for carpooling/ride-sharing/public transit.

So, basically, increase housing density so that more people are sharing established infrastructure. Fund the maintenance of this infrastructure using taxes that are population (or perhaps income) dependent, rather than property taxes.

Oh, and based on the cost and longevity numbers provided in the article, why would anyone ever use asphalt over concrete for a roadway surface? I assume some key factor has been left out of this comparison.

What Houston lacks in zoning laws, it makes up for with many, if not most, neighborhoods being "deed restricted" communities. For residents, this is effectively the same as zoning. From the city website (http://www.houstontx.gov/legal/deed.html):

"Restrictions mean limitations that:

-Affect the use to which real property may be put;

-Fix the distance that a structure must be set back from property lines, street lines, or lot lines;

-Affect the size of a lot or the size, type and number of structures that may be built on the lot;

-Regulate orientation of a structure; or

-Regulate certain fences requiring a building permit."

I know this isn't the point of the article, but did anyone else LOL at the bottom of page 3 when the difference of 10^100 - (ninety nine 9's) was given as 1? The author seems proud to attest "There really are ninety nine 9s!" The problem though is that this doesn't equal 1. You would need to subtract a number with one hundred 9's in a row to get an answer of 1.