– Xochielt Sanchez
What's it like working with the CIA as a computer scientist?
sanchez
How do rockets accelerate in space (or vacuum) in absence of any material to provide them the required reaction force?
– Xochielt Sanchez
Answer by Robert Frost:
Inside a rocket, there is a combustion chamber in which we ignite a fuel and oxidizer. They burn, converting into a very hot gas that wants to expand, rapidly. But the chamber is rigid and there is only one small hole, so the gas is ejected through that hole, out of the back of the rocket.
Newton's third law tells us that,
For every action there is an equal and opposite reaction.
Imagine you are on roller skates and you are holding a heavy cannon ball. What happens if you throw the cannon ball in front of you?
If there is a force propelling the cannon ball forwards, there must be an equal and opposite force propelling you backwards.
But, you won't move backwards as quickly as the cannon ball is moving forwards, because you are more massive. This concept involves momentum.
Momentum (P) equals the mass of an object (m) times its velocity (v).
Momentum of a system is conserved. That means that without outside influence, the total momentum of a system is constant. So, if you throw the cannonball and change its momentum by giving it a velocity in a particular direction, your change in momentum will be equal and opposite.
Tsiolkovsky came up with a rocket equation based on all of this:
The change in speed of a rocket is equal to the exhaust velocity of the fuel times the natural log of the initial mass of the rocket divided by the final mass. The final mass is the initial mass minus the fuel that was ejected out of the rear of the rocket.
So, we can make a rocket go faster by either increasing the exhaust velocity (make the exploding fuel hotter) or by ejecting the fuel out of the back of the rocket faster.
When is it appropriate to rub a stranger’s belly?
– Xochielt Sanchez
Answer by Sue Sullivan:
When the stranger is a friendly dog.
How does NASA manage odor inside International Space Station (ISS)?
– Xochielt Sanchez
Answer by Clayton C. Anderson:
One of my favorite things to do these days is to "piggy-back" on the wonderful –and always technically sound– Quora answers of NASA's Robert Frost. While he gives you the clear and concise "mechanical, text-book" type answer to your questions, I can jump in with some real life experiences. Together, it is my hope that our "tag team" efforts give you some insight that you may not have expected, but can honestly appreciate and enjoy. Hopefully, we are all learning something together!
As a two-time space flier with over 167 days in space (all but 8 on the International Space Station (ISS)), I have definite personal knowledge of the odors existing inside her anodized aluminum hull.
The systems mentioned by Robert typically perform flawlessly, with the crew performing routine maintenance on those systems per the schedule provided by the ground. This, in and of itself, gives us a significantly "odor-free" environment on the ISS. That's not to say we are without smells however. Our standard atmosphere, composed of the very same percentages of constituent gases that we have here on earth, is regulated to 14.7 psi and gives us a shirt-sleeved environment maintaining about 72 degrees F, 55% humidity, with a slight breeze out of the south!
Oleg Kotov, my Expedition 15 Russian crewmate and our Soyuz Commander, liked to stash his used workout clothes above the forward facing FGB (Functional Cargo Block, Russian Module) hatch. This was not my favorite choice for the stowage of sweaty workout gear as there was not a very good chance that they would dry out effectively. I chose to put my nasty shorts/socks/t-shirt onto a handrail in the US segment's Node 1 module. This handrail was near an A/C vent, meaning fresh, cold air would blow across my sweaty laundry for many hours until I donned them –dry as a bone– the next day. Decreasing their ability to generate any "locker-room" odors, that special placement also allowed for our environmental systems to easily soak up my sweat and turn it into drinking water for later!
Food odors were also present, but they didn't seem unusually overpowering to me.Eating a fish dish often produced the most pungent odor, especially the US version of seafood gumbo. It might take a couple of hours to "purge" that smell from the airflow of the ISS. On shuttle missions, many commanders outlawed the eating of seafood gumbo due to its distinctive, and disliked, smell.
And don't worry too much about the stink from the toilets. The airflow systems there (especially the US segment… not so much for the Russian side) were very effective (the shuttles had the absolute best system for containing poop odors!), pulling the stench quickly and completely into the bowels (from one set to another!) of the ISS where they were absorbed efficiently by filters.
Finally, there is the "smell of space." Oft mentioned by astronauts, in answering insightful questions from folks like you, the smell of space is somewhat hard to describe. Ever distinct –I would know it instantly if I smelled it– it has been likened to smells associated with welding or burning of ozone (now who the heck really knows what that smells like?!). Most noticeable following a spacewalk, when crews and their equipment returned to the inside of the ISS, I remember being able to smell traces of this unique scent for several days following an excursion into the unforgiving vacuum of space.
Keep lookin' up! And thanks to Robert Frost, for his continued, insightful answers.
How does NASA manage odor inside International Space Station (ISS)?
What are the biggest cultural differences between Yale and Harvard?
– Xochielt Sanchez
Answer by Dave Cheng:
I've been sitting in front of my computer pondering this question for the last 15-20 minutes, and the best I've been able to come up with is: not much.
I went to Harvard undergrad 2001-2005, my wife went to Yale for an MA and a PhD 2006-2013, and many of my closest friends and former colleagues went to HLS, YLS, or HBS*. I also grew up outside of Boston (20 minutes drive from Cambridge/Harvard Square) and spent most of my weekends during law school (in Manhattan) taking the train up to New Haven to see my girlfriend (now wife). Like most answers to these types of questions, my experiences are mostly anecdotal, and I'm sure many people will have had different experiences and some may strongly disagree with my observations:
By "not much" I mean both universities have talented (and lucky**), ambitious, and diverse students and faculty with well-funded facilities. Both universities enjoy top brands***. Both are very well endowed****.
Here are a few random and, as already mentioned, anecdotal observations (i.e., subjective generalizations) on how they differ:
- New Haven has much, much better pizza. Let's just get that out of the way.
- Cambridge has better bars and better looking locals (e.g., the ones going to other schools). Both have amazing restaurants though (I'd say it's a tie in terms of food).
- Yale's campus is prettier–and older–but both campuses have their charm.
- In terms of reputation/prestige, Harvard college students are slightly more envied (rightly or wrongly) by their peers while Yale law students are much more envied (rightly) by their peers. Yale law school, which rejected me by the way, is the hardest law school to get into by a wide margin while HLS pumps out nearly as many biglaw corporate lawyers as other conveyor belts for biglaw sweatshops: Columbia, NYU, and Stanford law schools.
- More douchebag lawyers and bankers working in PE, hedge funds, investment banks, law firms, and consulting shops came out of Harvard than Yale–though both have their fair share. More activists, politicians, judges, and artists came from Yale–though both have their fair share. More entrepreneurs came out of Stanford than both combined. Again, this is purely anecdotal, and I only speak for my generation (born in the early 80s or late 70s) and the social and profession circles I've passed through personally.
- Cambridge and greater Boston overall are much safer than New Haven, which has rougher, lower-income neighborhoods and much more crime [1]. My wife used to get New Haven crime bulletin alerts while she was living off campus. Muggings, carjackings, and similar crimes were reported almost weekly.
- Cambridge is younger (i.e., surrounded by colleges, populated by their undergraduate and graduate students, as well as local high schools and the dropouts of those high schools ("townies")) and more cosmopolitan (i.e., more ethnic and cultural diversity among the locals) than New Haven.
- Despite the above and despite being so close to Boston, Harvard undergrads are slightly less likely to venture off campus than Yale students. Yalies get into Manhattan (slightly over an hour via metro north railroad from New Haven to Grand Central station) more often than Harvard kids go into Boston. Purely anecdotal again, but I got the sense that Harvard kids are less likely to study abroad as well.
Most of the above boils down to geography.
All sophomoric jokes during Harvard-Yale games aside [2], most of the students at both universities deep down inside understand that the two schools share more similarities than differences. I disagree with Christopher's answer about Yalies being more likely to have a chip on their shoulders. I've met plenty of kids at both schools with huge, boulder-sized chips on their shoulders–minorities on financial aid who show up on campus and immediately think "I'm not like the spoiled, trust fund fraternity/finals clubs/skull+bones WASPs I see all around me who are just coasting and more concerned about partying than studying." [3].
Plenty of those types of underdog overachievers at both schools. I wasn't one of them. I was an anti-social slacker for most of college. In law school, I overcompensated and spent far more time trying to make friends and participating in student groups (and partying) than studying.
Plenty of all types of students and cultures at both schools–which of course is a big part of what make both great. We shouldn't over-generalize.
—
*didn't realize until now that I don't know very many Yale MBAs off the top of my head
**Like it or not, luck has a lot to do with where one ends up going to college as well as how "successful" or happy many of us end up in life. Very little separates a Harvard student from a BU student:
Dave Cheng's answer to What do Ivy Leaguers think of non-Ivy Leaguers?***In the U.S. and even more importantly abroad, brand very much matters when it comes to higher education: Dave Cheng's answer to Why do so many students in China want to study abroad, especially in America? Is the education in China really so disappointing compared to that in developed countries?
****I briefly interned for HMC, which manages and invests Harvard's endowment in 2004–back when it was the second largest non-private fund (after the Vatican). I just realized I rather enjoy bragging about how well-endowed my alma mater was/is. I'm going to do it more often.
Pssst, my alma mater has a bigger endowment than yours.
[1] Only safer than 3% of other U.S. cities…
New Haven CT crime rates and statistics
New Haven Police Plan To Revitalize Neighborhood Watch Groups[2] harvard-yale shirts jokes – Google �j�M
Each year, the best minds at both institutions (i.e., the editors at the Lampoon and Record) brainstorm long and hard to come up with highly witty, highly original slogans for The Game–comedic aphorisms summing up the faults and insecurities of the competing school. Particularly memorable ones include "yuck fale" and "harfart."[3] "Now for some of you, it doesn't matter. You were born rich and you're going to stay rich, but here's my advice to the rest of you…"
http://www.youtube.com/watch?v=m5RbdReBMLEThis would be a great speech for students at either university.
What are the biggest cultural differences between Yale and Harvard?
What were you born “too late” for?
– Xochielt Sanchez
Answer by Soumadeep Mazumdar:
I was born too late to be respected as an Engineer. (At least in India.)
Once this used to be a pioneer profession. Now they are just everywhere. I stopped asking young people what they do for a living years back. I just ask them which college they are from and their concentration.
Here is a small joke to further enhance my point,
20 years back.
Salesman to Shopkeeper : Where does the Engineer live?
Shopkeeper to Salesman : You see that bunglow up front, that one.Today.
Salesman to Shopkeeper : Where does the Engineer live?
Shopkeeper to Salesman : You just go ahead and knock on any door.
Does Tim Cook get the latest iPhone ahead of its official release?
– Xochielt Sanchez
Answer by Marc Bodnick:
For sure. Many top executives at Apple (and certainly Tim Cook) would have been using the iPhone 6 as it went through various build versions during the development process.
You shouldn't think of this as "was he fortunate enough to have early access to the finished product?" and more as "he was using various versions of the product as it went through development."
To be clear, I'm not 100.00% sure of this. He's probably not as crazy hands-on product-obsessed as Steve Jobs was. But given the importance of the product to Apple, and how product-oriented Apple is, I'd be shocked if my answer wasn't correct.
My expertise on this: I've seen stuff like this up-close as an investor.
Does Tim Cook get the latest iPhone ahead of its official release?
How dominant is Apple?
– Xochielt Sanchez
Answer by Marc Bodnick:
They really aren't dominant at all.
- In computers, they are still dwarfed by the Windows/PCs ecosystem.
- In mobile, they are a distant #2 to Android.
To be clear, this is really great for Apple customers, because Apple has been forced to increase its sales by making better products and pushing the envelope on commercializ-able technology — rather than by leveraging and harvesting its monopoly position to the detriment of its users.
Why do astronauts grow an inch in space?
– Xochielt Sanchez
Answer by Robert Frost:
In microgravity the spine elongates 1-2% because there is no longer axial loading pushing down, compressing the spine. The spacing between each vertebrae increases slightly, resulting in a longer spine and thus a taller astronaut. The downside is that the stretching of the ligaments can cause spasmodic back pain.
What are the long term effects of nicotine use on intelligence?
– Xochielt Sanchez
What are the long term effects of nicotine use on intelligence?
xochielt 