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The Brainteaser Elon Musk Asks New SpaceX Engineers
Nerval's Lobster writes: The latest biography of Elon Musk, by technology journalist Ashlee Vance, provides an in-depth look into how the entrepreneur and tech titan built Tesla Motors and SpaceX from the ground up. For developers and engineers, getting a job at SpaceX is difficult, with a long interviewing/testing process... and for some candidates, there's a rather unique final step: an interview with Musk himself. During that interview, Musk reportedly likes to ask candidates a particular brainteaser: "You're standing on the surface of the Earth. You walk one mile south, one mile west, and one mile north. You end up exactly where you started. Where are you?" If you can answer that riddle successfully, and pass all of SpaceX's other stringent tests, you may have a shot at launching rockets into orbit.
I am guessing the answer is the north pole...
Be kind, for everyone you meet is fighting a difficult battle. - Plato
Lines of longitude and latitude converge into triangles at the poles. Just a guess.
$x = ($x * 10) % 10 >= 5 ? 1 + int $x : int $x
But since there's no "earth" at the north pole, the correct answer is obviously the south pole.
they take
You are in a square room. All four sides have Southern exposure. A bear walks by. What color is it? :)
Typical brainteaser that gets you so caught up in the math, you forget everything else.
This brainteaser is old and widely known. And the traditional answer is wrong. (Hint: there are an infinite number of valid points on the Earth surface, and some of the solutions are 20.000km afar one from the other.)
My first program:
Hell Segmentation fault
you would have to be on an asteroid.
The harder brainteaser they SHOULD ask:
A large, cylindrical object is falling. You want it to land upright, with the correct end down. Which of these strategies do you choose:
a) Attach a parachute to the nose and let basic physics work.
b) Try to balance it atop rocket engines firing from the bottom.
Since he says you start by walking south, the only correct answer is the North Pole.
Once you are at the south pole, you can't get any further south.
Can't be the South Pole, there's no "walking one mile south" from the South Pole. Everywhere is north.
Would never do that in the first place.
No wonder SpaceX is going bankrupt. Nasa would never stoop for the run-of-the-mill yokel.
guess its an arduous game of mind trap
I wouldn't have thought Musk would be so behind the times as to ask useless questions like this. Brainteasers are for interviewers who don't know what they are doing or what they are looking for in a candidate. The only possible valuable information you could get out of it is how a person reacts to being assigned stupid and useless tasks.
Start far enough north of the south pole that once you've walked a mile south, you're X distance away from the actual south pole, and can then walk west for one mile that ends up putting you in the same spot as when you started walking west, then walk north and end up where you started. Too lazy to do the math, but that is the logic.
So you're saying he should only accept people who have played a bit of Kerbal Space Program?
The obvious answer is the North Pole, but there are others. First, find the circle around the South Pole with a circumference of one mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Then, find the circle around the South Pole with a circumference of one half mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Then, find the circle around the South Pole with a circumference of one third mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Then, find the circle around the South Pole with a circumference of one quarter mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Continue ad nauseum.
I'm sitting right in front of you.
Trivia != Mental processing
/thread
It's funny how people talk about the poles when Musk never mentioned starting on the poles. You will end up in a different place if say you start in China. Net vector will cancel your trip north and south, ending up just travelling westward.
Also, it's a brain teaser. Never think too hard on a brain teaser. The answer is in the words. Musk is looking for a person that listens, not a person who thinks too much.
b.
Congratulations, you get the job!!
why attach the parachute and another rocket to provide thrust downward... to get it down there faster!
ok. north pole. good answer...
now lets say you're standing on land.... and not on antartica..
now where are you?
You also want it to land slow enough for it not to be damaged.
Relative to Mars, you might as well have not moved at all...
You are on the surface of the earth!
Aside from the North Pole: 1+n/(2 pi) miles from (North is redundant) the South Pole, where n is a positive integer.
The US government have made it clear that we have no inalienable rights; any we do not defend vigorously will be taken.
I know people don't RTFA, but apparently nobody RTFP(osts) either. we've got, what, 30 identical wrong answers (north pole only), 30 people who don't understand the difference between 1 mile from the South pole and 1mile+ X/pi ?
Just for that: imagine a Beowulf cluster of starting points in the Southern Hemisphere...
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
The question says "one mile south, one mile west, and one mile north." The west-bound portion is a curved line. If you walk a straight line, after one step you are no longer walking west, but rather a south-of-west direction.
2 Correct answers. First off, the north pole. Second, 1 mile 840ft north of the south pole.
I bet that final question (and probably the rest of the article) is as fake like the also famous Google interview questions, debunked many times.
In that case the correct answer would be "moar boosters!"
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
Answer: Both.
A parachute can help to point the deceleration rockets in the correct direction (down) before they fire, with a minimum of fuel usage and weight. Think of it as the 90% part. The rocket engines and all their complicated, expensive, and failure-prone controls and fuel supplies get the 10% job.
The "north of the South Pole" answers are more correct...because good luck walking the open waters around the North Pole.
Jhyrryl
Answer: Butter the bottom
(alt: affix cat to superstructure)
crazy dynamite monkey
It may be a trivial adjustment but the curvature of the earth should be taken into account on the low values of n.
I would hope just noting this would be enough for credit with Elon.
Knowing when not to waste time on a triviality unless you know you need the accuracy, should be important.
Would consider such a simple question to be a "brain teaser". In fact, I suspect this is totally fake. Why in the hell would Musk would his time and that of a freakin' rocket scientist??? He might as well demand proof that the interviewee is capable of putting on his own shoes in the morning.
Oh Mr. Musk, don't be so coy. If you want a handy just ask.
Good One!!!
http://en.wikipedia.org/wiki/L...
Rockets on the bottom is the right way to land a rocket.
Learn to love Alaska
On a treadmill using an oculus!
The Brainteaser Elon Musk Used To Ask New SpaceX Engineers, Because His Old Question Got Slashdotted.
Thanks jerks!
Left MS Windows for Linux Mint and never looked back!
Vote for Bernie in 2016!
Difficulty level: It can't touch the water in the process.
The answer Musk is looking for is:
"Are these cardinal directions magnetic or geographic? Is the surface you are walking on completely flat for the entire distance? Is that 'mile' in statute miles, nautical miles, Roman miles...?"
If you pop off an answer like "North pole! Ha! That's so easy." you fail. He wants to know if you're the type of person that is going to worry about the details and isn't going to crash one of his rockets when you don't notice one software sub was calculating metric units and the other one was calculating in imperial.
Maybe they want the system to work whether or not their is an atmosphere.
.: Semper Absurda
Agreed. A better, and more recent one, which you might nat have seen would be this one.
*there
.: Semper Absurda
Who can walk (or stand) on water? At least one religious leader is known for this ...
I really, *really* dislike hearing brain teasers in an interview.
Not because I don't like puzzles (I do), not because it's not a good way to judge the candidate (it is, in a sense), but because it shows up the deficiencies of the interviewer and the company.
Most of the time, the interviewer isn't into puzzles. They just looked something up on the internet, got a list of "here's a puzzle to ask the candidate", and mindlessly ask the question(*).
And when this happens, I answer the puzzle and then ask the interviewer my own puzzle, and see how they react.
Invariably, the answer is "I don't know. What's the answer?" within 3 seconds.
I don't want to work for someone like that, I don't want to work for a *company* that would hire someone like that, life's too short to spend time working amid thinkless drones.
A really bad company is when the VP or someone sticks his head in the door with a "hey, just wanted to see how it's going. Can you answer this question for me?" thing. I keep a chinese block puzzle in my pocket (that I invented) for this exact situation: I write down his answer on the whiteboard, hand him the puzzle, and say "if you can't disassemble this and reassemble it before the day is over, I don't want to work here".
Polite and reasonable interviews don't get this level of response, but turnabout is fair play. Ask me about my experience, ask me to solve a typical problem from the job description, get a feel for how well I work with others... these are reasonable.
But ask me why sewer caps are round, and you'll have to prove why you're company is good enough for me to work there. While you're interviewing me, I'm also interviewing *you*.
If everyone was more aggressively responsive to these types of games, companies wouldn't play them.
(*) Once, just once, I got into a real discussion of puzzles with the interviewer, I've got no problem with that. So long as it's not mindless bingo-card checkmarking, it's OK.
that is an olde
i think i first heard that in the 1970's or 80's
( k 6 through 12 , sometime in there)
the north pole
but i am used to the reverse order and having the south pole as the answer
"I don't pitch OpenSUSE Linux to my friends, i let Microsoft do it for me
The answer is the surface of the earth
It should be posed, "not only you are exactly where you started, there is bear trying to kill you. What color is that bear's coat?".
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Back in the early 90s, I discovered the magic of seed based procedural generation to make a MMORPG world the size of an actual planet. The problem I had with a 2d based tile game is that its okay if you wrap around the edges east-west, but when if you go so far north. My solution which I never implemented was to translate you to the top of the map where you'd be translated to, but it had problems too because a player would be disoriented,"Why am I going down now?" So I was thinking you'd need to maybe flip the whole map upside down, but then that makes problems making sprites that would have to be flippable and such. This was not an easy problem to think of, but today I stick with KISS. I'd probably put them where they should be, 'maybe leave them where they're at', not flip the map, and say,"Congratulations, you just reached the top of the planet, now start going back down"
God spoke to me
and needs to land with a low enough velocity to keep it from being damaged too much.
Oh, and for the record, the puzzle that Elon Musk asks is:
1) Older than dirt
2) The answer is common knowledge (hence, not a good puzzle to ask)
3) Has more than one correct answer
4) Is being asked wrong.
The actual full text of the puzzle should read something like: "A hunter walks [South... West... North... ends up in the same spot] and sees a bear. What color was the bear? (This version has only one answer.)
Here's one that *you* can ask during an interview.
You need to order weights for a 2-pan balance to weigh objects. The objects all weigh integral ounces (ie - no fractions), and the weights are all integral ounces.
What is the minimum *number of weights* you can use that lets you weigh anything up to 100 ounces?
(NB: the answer isn't 7.)
I interviewed with SpaceX for a senior-level software position last year, and was offered the job but turned it down on logistical grounds.
I did indeed have to take the tests mentioned here, and did have to interview with Musk himself as the final step. However, he did not ask me this brain teaser question. In fact, he specifically said he doesn't ask brain teaser questions because they are dumb.
Nor would he likely ask such a well-known and old brain teaser anyway. This seems like one of those things erroneously attributed to "Bill Gates" over the past 20 years because he is famous and smart, and fits people's preconceptions.
I like the one about hull displacement, canoe, rock displacement mass, hull volume, etc. Obviously the canoe was a rocket hull, displacement is thrust, rock is fuel, and the final answer is trajectory.
Standing on a Virtuix Omni. :P http://www.virtuix.com/ (No I don't work for them in any capacity.)
"GET / HTTP/1.0" 200 51230 "-" "Mozilla/4.0 (compatible; Setec Astronomy)"
You're on VR treadmill.
Which of these strategies do you choose:
a) Attach a parachute to the nose and let basic physics work.
b) Try to balance it atop rocket engines firing from the bottom.
I realize you were going for humor (and got it; congratulations on being moderated +5 Funny). But here's a serious answer.
It depends on what you are trying to accomplish:
If your top priority is to save the rocket stage, then you pursue an engineering strategy that has the best chance of saving the rocket booster. Maybe that means a parachute system; I don't know.
But a parachute system adds mass and complexity. It becomes another critical system ("if the parachute fails, we lose the rocket stage"). The rocket stage needs functioning rocket engines, so landing on the rocket engines is another use for those engines rather than a new system with a single purpose. All else being equal, the simpler design with fewer systems is more likely to succeed in its tasks.
If you add a few hundred kilograms of parachute system mass, that's going to mean the booster can push less mass to orbit. I'd guess that the loss factor is higher than 1... that each additional kilogram of non-fuel mass on the booster reduces the to-orbit capacity by more than one kilogram. But ask a physics expert for the actual numbers.
Note that new software to make the booster land on its engines does not add mass to the booster.
So I'd say that if your top priority is to efficiently deliver stuff to orbit, the parachute system is right out and the clear engineering decision is (b).
lf(1): it's like ls(1) but sorts filenames by extension, tersely
Glad I figured it out in about 8 seconds, including 5 seconds to check my work.
And I'm still unqualified to wok for SpaceX, which is a mild disappointment.
deleting the extra space after periods so i can stay relevant, yeah.
Nice, nice. Started to chuckle before I finished the first sentence of the question :)
The hospital, after Superman has flown me there, because that's the only way I'd survive walking a mile under those conditions.
I wonder if he charges ambulance fees.
It's pretty obvious that Musk provides the answer, and then gives a pretty vital clue to the answer. "You're standing on the surface of the Earth" Now the clue is "You end up exactly where you started." Even though you've walked these miles and ended up a mile west of where you were, he tells you that you haven't gone anywhere. Because you're still standing on the surface of the earth. Simple.
Next question.
Seriously? The oldest fucking brain teaser in the world. It was on QI for fuck sake. No wonder they can't land that fucking rocket on the barge. Seriously my opinion of Elon Musk has just nose dived. And I already knew he was a South African.
YOU ARE ON THE EQUATOR
And on the subject of interviewing companies, here's my response to Elon Musk:
The North Pole.
You lay a rifle on the surface of a [perfectly] spherical planet with no atmosphere. Firing the rifle, due to the curvature of the planet the bullet goes some distance and then falls to the ground. As you increase the muzzle velocity of the bullet, the point if impact gets further and further from the rifle.
If the planet has an acceleration of 10m/(s^2), what velocity must the bullet have to go around the planet and hit the gun in the stock?
(NB: This is a trick question, but Elon Musk is an actual rocket scientist.)
The source for the SpaceX Falcon 9 first stage lander will win the 2015 Obfuscated C contest.
When the copyright term is "forever minus a day", live every day like it's the last.
c) Outsource the problem to Russia.
Table-ized A.I.
"I'm still right here at SpaceX, interviewing with you Elon. We only imagined that I'm walking around."
"Is there a lot of walking involved in this job? If so, you should know that I came in 2nd in a walkathon."
"Standing in a light rail car on an East/West branch of a system with stations every mile."
"Still not on Mars, damn it! Hire me and let's get going!"
"Pretty much anywhere, if the GPS in my phone malfunctions that badly."
I'd be worried about an aerospace company that thought that miles was a good way to measure anything.
You are exactly where you where when you started. Or did he actually ask "What is the location of your starting point?" The question, as reported, is ambiguous. Otherwise it is 1 mile from the south pole. You walk to the pole, where there is no west or east, then your return north.
If I were asked that question, I think I'd answer it well. Not because I would be able to figure it out quickly under pressure, but because this brainteaser is very old.
When I was a kid in the 1950s I read both it and the original intended correct answer (the North Pole) in a book of brainteasers.
When I got into high school, someone who was actually smart discovered that the answer wasn't unique and that there was an infinite family of additional answers all involving points close to the South Pole, and I read about that, too. I'm not sure where; I think it was in Martin Gardner's "Mathematical Games" column in Scientific American.
There must be million of people who know the answer, not because they figured it out by themselves, but because they read or heard the answer somewhere.
Of all the candidates who give Mr. Musk the correct answer, I imagine very few of them are solving it on the spot. I wonder how many of the others are honest enough to volunteer the information that they had already read the answer.
Or perhaps that's the point--perhaps it's an honesty test rather than a brain-teaser.
"How to Do Nothing," kids activities, back in print!
add "You see a bear, what color is it?"
-- 73 de KG2V For the Children - RKBA! "You are what you do when it counts" - the Masso
I'd thank him for his time and take my leave telling him that metric was the way to Mars, not that imperial crap.
Anyone with half a brain can get the first answer. Anyone that I could actually work with would get the second.
I am guessing the answer is the north pole...
Magnetic North or True North?
I'd argue you are going to need a heck of a lot more rocket fuel for deceleration than the mass a parachute system would require.
---jstlook ---For that is the way of Elves, for they say both yes AND no, and mean every word of it. --- J.R.R.T.
There are a series of spots near the south pole you can also be. Start by drawing a circle 1 mile circumference around the south pole. Start a mile outside it. also works with a circle 1/2 mile circumference or 1/3 mile or 1/4 mile and so on.
The point of brain teasers is not to prove you're clever enough to know the answer, but to ask a question that you might not have heard before and observe your reasoning and explanations. While the North Pole question is cute, and most interviewees would know the question (at least I hope so), being able to answer it indicates not that you are smart, but that you have a certain kind of background that leads you to have been exposed to such things. Now if we continue with that assumption, then there are other questions that are worth asking.
My personal favorite question is: Explain the answer to the Monte Hall problem in such a way that a high school student could understand it.
A lot of people know the answer to the Monte Hall problem. Most people are confused by it, or get the answer wrong, but let's concentrate on those who know the answer or can figure it out on the fly. A few of them can cogently explain the reasoning behind the correct answer. Even fewer can explain it in such simple terms that a teenager could understand it. Those are the people I want to hire.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
Well, we know that a parachute is so simple that George Bush can use it. If their design is even simpler, yet they keep screwing it up ...
There IS a reason they're trying to balance that big rocket from the bottom, but simple isn't it.
Space, people. The correct answer is, of course, in an alternate universe. Why? Because what with the Earth and our solar system flying rapidly through space, by the time you have done your 3 mile walk, you (and the Earth) will be far from where you started. Only another universe -might- happen to be in the exact spot where you started. Thank you. Elon, you can reach me on LinkedIn.
Twenda Learning: Educational Apps that Engage.
Had I not already posted in th
The question doesn't say walking in a straight line, just walking west. A circle around the pole is the trajectory traveled when walking westward near either of the poles. The solution around the North Pole also requires walking a curved path. If you walk straight you either end up almost a mile away (if using Great Circles as your definition of "straight"), or exactly a mile away, hovering in the air (if using Euclidean "straight").
After you have traveled one mile south you would travel west on a rhumb line course. From Wikipedia, "In navigation, a rhumb line (or loxodrome) is an arc crossing all meridians of longitude at the same angle, i.e. a path with constant bearing as measured relative to true or magnetic north." In this case, you would want to measure relative to true north since the north magnetic isn't close and magnetic compasses don't work well at all at that high of a latitude. Wikipedia reference: http://en.wikipedia.org/wiki/R...
Go figure that Mr. Paypal would be asking questions like this.
Since learning my lesson about interviewers who ask brain teaser questions, I've turned down every offer I've had where they did ask one. And so far I've made the right call every single time.
Sorry - it's the obvious answer :-)
"dead", no Cheetos-eating, sci-fi gobbling Space Nutter can walk three miles in one sitting.
b) Try to balance it atop rocket engines firing from the bottom.
(c) Balance it from rocket engines firing downward and to the sides from the top.
It must have been something you assimilated. . . .
You go south one mile, west one mile, north one mile, end up where you started, and shoot a bear. What color is the bear?
There is only one answer, unless they have opened a zoo near either pole recently.
Now get off my ice sheet!
If I were 1 meter away from Elon Musk I would kill him to end his stupid question. I would gladly spend the rest of my life in a max-sec prison with all the comforts of home, 21 century digital home, and all the latest in exercise equipment and olympic swimming pool to pleasure.
Fuck Elon.
I'm home.. because I started one mile East of my house.
You really hired, congrats
The answer is actually the Bermuda Triangle obviously.
Personally I think everyone is over thinking. The North Pole is not the only place you can up in the same place....
First off, the Equator. Didn't say it was the same physical place..
Secondly, and more prominently. Earth... You never left it, so technically are in the same place. And considering this is a company whose whole prospectus is leaving Earth. The most likely and sound answer is, "On Earth".
Now hurry up and make vacation space travel feasible for the 1%. We want you to make sure it's nice and unaffordable just like your cars so the plebs have no chance of having their lives enriched in any way. Elon Musk, greed visionary.
Mod parent up. Too sleepy to try to work this out in detail, but what struck me about most of the solutions is that it assumes a person is walking following the lines in some gigantic desktop globe. So straight lines "down" (south) and "up" (north), which should cancel out the longitudinal movement. And then a curve ball along the latitude. Would the gravitational force be strong enough at such a scale to bend the path of someone walking west into a spacetime-like curvature?
The only correct answer is the North Pole. South means follow a line of longitude in the South direction, West means follow a line of latitude West, and North means follows a line of Longitude North. The only place this gets you back to where you started is at the North pole.
Following a compass that is. Not sure if the magnetic north pole is still in Canadian territories as it has been wondering northward, but I'm pretty sure the magnetic south pole is well into the Indian ocean by now.
Task Mangler
one mile south, then west, then north isn't the same exact spot that you started at. You would have to go one mile east. Unless "You end up exactly where you started" means you go 1 mile east.
The point is not to land back on earth, but rather to land on another planet and take back off. Parachutes may not work.
the question made no distinction between straight and curved lines
I'd argue you are going to need a heck of a lot more rocket fuel for deceleration than the mass a parachute system would require.
I'm not so sure of that. But I'm not an expert. Most of what I (think I) know about space I learned by reading through long discussions on the Internet.
In this case I am thinking back to discussions of SSTO craft and whether or not wings make sense; the experts all agreed that it would be better to land as a rocket than add extra mass to the system. And the key is that the thing lands almost empty... when it's taking off it's boosting itself full of fuel plus whatever upper stage(s) are in use; when it's landing it's just decelerating its own empty weight.
lf(1): it's like ls(1) but sorts filenames by extension, tersely
With balancing on rocket engines you get practice for landing and taking off from Mars repeatedly, if you have an orbiting "gas station" Besides, who wants to do an EVA to repack parachutes? Check out Max Hunter's RITA* concept from the 1960's if you want to see where SpaceX (and soon everyone else) is headed. *Reusable Interplanetary Transport Approach
It's a logic test, not a geography test.
The correct answer is in the question: 'You're standing on the surface of the Earth'
The instructions are there to catch out people that can't think out of the box. ie. those that answered 'north/south pole', etc.
It's quite a simple question used to filter out those who aren't A+ players.
What do i win?
-
if you want to be pedantic, because "south of the south pole" would not make sense
it's only a *semantic* difference...b/c of how lattitude is measured...
the *most logical* answer is near *both north or south pole* at w/e point the math says to be
it's not asking "north latitude" it just says "north"
it is an assumption based on semantics only and it is very revealing about someone's thought process
it's over-literal analysis of the question...it's a thinking error to say "only North Pole"...**however** let's note that most of the best descriptions of the why the answer works are from the over-literal "north pole only" types...
Thank you Dave Raggett
but you can start a mile north of the south pole (yes I looked it up!) and the solution still works.
exactly...
it's only a *semantic* difference...b/c of how lattitude is measured...
the *most logical* answer is near *both north or south pole* at w/e point the math says to be
it's not asking "north latitude" it just says "north"
it is an assumption based on semantics only and it is very revealing about someone's thought process
it's over-literal analysis of the question...it's a thinking error to say "only North Pole"...**however** let's note that most of the best descriptions of the why the answer works are from the over-literal "north pole only" types...
Thank you Dave Raggett
This is the kind of dumb question which rarely if ever exposes anything about the candidate other than whether they heard this brain teaser before.
I sure hope this isn't really what he asks people.
http://lkml.org/lkml/2005/8/20/95
Gravity is the same. But to stay "west" (which is west of the pole) means you must travel in a circle, otherwise you drift south (or north at the south pole) with each straight line step.
Nice to see somebody getting it right.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
How come he is exactly at same place that he was initial. If he moved 1 mile South, then 1 mile West, and then 1 mile north, he should be 1 mile west to where he initial was, dafuq buggy question. To reach the initial position there should have been a 1 mile east associated to negate the west movement.
*they're
How is this a brain teaser? There is only one answer possible and it follows directly from the question.
Here's the first hundred latitutes [I wrote a perl program--so it could never be wrong ;-) and I had to derive it]
loop degrees S lat dist to S pole
001x 89.973676291007 1 mi, 840 ft, 4 in 002x 89.975483447346 1 mi, 420 ft, 2 in
003x 89.976085832792 1 mi, 280 ft, 1 in 004x 89.976387025515 1 mi, 210 ft, 1 in
005x 89.976567741149 1 mi, 168 ft, 0 in 006x 89.976688218238 1 mi, 140 ft, 0 in
007x 89.976774273302 1 mi, 120 ft, 0 in 008x 89.976838814600 1 mi, 105 ft, 0 in
009x 89.976889013387 1 mi, 93 ft, 4 in 010x 89.976929172417 1 mi, 84 ft, 0 in
011x 89.976962029805 1 mi, 76 ft, 4 in 012x 89.976989410962 1 mi, 70 ft, 0 in
013x 89.977012579633 1 mi, 64 ft, 7 in 014x 89.977032438493 1 mi, 60 ft, 0 in
015x 89.977049649506 1 mi, 56 ft, 0 in 016x 89.977064709142 1 mi, 52 ft, 6 in
017x 89.977077997057 1 mi, 49 ft, 5 in 018x 89.977089808536 1 mi, 46 ft, 8 in
019x 89.977100376702 1 mi, 44 ft, 2 in 020x 89.977109888051 1 mi, 42 ft, 0 in
021x 89.977118493557 1 mi, 40 ft, 0 in 022x 89.977126316745 1 mi, 38 ft, 2 in
023x 89.977133459655 1 mi, 36 ft, 6 in 024x 89.977140007323 1 mi, 35 ft, 0 in
025x 89.977146031178 1 mi, 33 ft, 7 in 026x 89.977151591659 1 mi, 32 ft, 3 in
027x 89.977156740252 1 mi, 31 ft, 1 in 028x 89.977161521089 1 mi, 30 ft, 0 in
029x 89.977165972213 1 mi, 28 ft, 11 in 030x 89.977170126595 1 mi, 28 ft, 0 in
031x 89.977174012953 1 mi, 27 ft, 1 in 032x 89.977177656414 1 mi, 26 ft, 3 in
033x 89.977181079058 1 mi, 25 ft, 5 in 034x 89.977184300371 1 mi, 24 ft, 8 in
035x 89.977187337608 1 mi, 24 ft, 0 in 036x 89.977190206110 1 mi, 23 ft, 4 in
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Like a good neighbor, fsck is there
The way this goes is: A hunter walks one mile south, then one mile west, and he shoots a bear. He then walks one mile north, and arrives at his starting point. What color was the bear?
Answer: it was white, because the north pole is the only place where the movement described is possible.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
> Note that new software to make the booster land on its engines does not add mass to the booster.
Extra fuel to use for landing does. So the salient question is does that extra fuel weigh more than the parachute system?
I happen to know a guy that works at SpaceX. While we were in school together, the best I can say about him was that his arrogance was matched only by his incompetence. He can't be the standard there, or else all their rocket launches would look like a pyrotechnic blooper reel from Kerbal Space Program. But the mere fact that they hired him lowers the entire organization in my eyes.
c) Remove systemd
Or strap a cat somewhere to the superstructure....
If information wants to be free, why does my internet connection cost so much?
The north and south bound portions are curved lines as well, unless you want to become airborne.
Just another day in Paradise
What an easy question. You are still on Earth, that's the whole problem SpaceX is trying to solve.
The harder brainteaser they SHOULD ask:
A large, cylindrical object is falling. You want it to land upright, with the correct end down. Which of these strategies do you choose:
a) Attach a parachute to the nose and let basic physics work.
b) Try to balance it atop rocket engines firing from the bottom.
Yep. And then the next question would be: "Okay, so now make your solution work on the Moon and Mars."
(because that's what he's *really* trying to achieve long term)
I couldn't help hearing the question in my head in that voice, "You're standing on the surface of the Earth. You walk one mile south, one mile west, and one mile north. You end up exactly where you started. Where are you?"
Well there is bound to be some shit floating around any gravity well. As long as we are talking spherical cows in a vacuum just make the massless parachute larger? How do you actually define "atmosphere" anyways?
You also have :
c) Attach a ring of rockets to the top of the cylinder and allow gravity to balance it for you.
d) Use a teardrop shape instead of a cylinder so that it falls blunt end first, add fold out wings at the other end to produce drag and use the rockets at the top to slow the thing down.
e) Forget the land upright part, stick fold out wings on it and land it horizontally like an aircraft.
1) First assume that the Earth is a perfect sphere
2) ???
3) PROFIT!!!
Citation:
http://en.wikipedia.org/wiki/S...
"In navigation, a rhumb line (or loxodrome) is an arc crossing all meridians of longitude at the same angle
Don't be silly - a loxodrome is a building where they raise tasty fish.
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
By the time you walk any amount of distance, the earth has moved around the sun, and the sun around in the galaxy, and the galaxy, etc. no amount of course correction will put you back where you started.
Obviously,
North Pole simulation.
I knew the answer to that one in grade school. I hope that successfully answering that question is not a major factor in getting hired there.
CUR ALLOC 20195.....5804M
Everyone keeps pointing out the two poles. Which doesn't make a lot of sense to me. If it's true for the north pole which is only special due to its magnetic properties and not that it's that top of a relative sphere or the south pole with the same attributes. If you're going to generalize this enough that it works it should work for any point on this general sphere as long as you don't adhere to conventional long/lat lines and draw a new set based on your current location being the focal point.
Take a picture of a sphere with your answer. Superimpose a picture of earth supporting your answer. Now rotate your answer and proof so that you start in the middle of africa or anywhere where on the planet with a flat surface and you'll find it holds.
n/t
You are on the surface of the Earth-- where you've started..
Draw two spheres about 3/4 overlapped , now draw a third sphere that completely surrounds the first two. You now have an accurate Ven diagram of Theory, Mathematical modeling, and Reality. The big circle is reality. And for the riddle the devil, as always, is in the details. One cannot stand on the earth at the north pole. Also triangles on spheres are cool but and equilateral triangle on an oblate spheroid isn't really possible , even at the north pole . The only reasonable answer where One could stand on the earth and walk an equilateral triangle right back to their starting point with a fair chance of success would be someplace really flat , so my guess would be that I am at : The salt flats in Bolivia, Salar de Uyuni
You are exactly where you started. The surface of the earth. This question is not about math but rather about deductive reasoning.
You start "on the surface of the earth" - You end "on the surface of the earth."
**their
And then you shoot a bear. What color is the dear?
...richie - It is a good day to code.
I asked prospective engineering hires this question: I own a major league ballpark. I need new grass. If turf is $1/square ft., about how much would it cost me to resod the field? I didn't care about the answer, I wanted to see their thinking. I was amazed at how many couldn't even start to work the problem, many said they needed their computer to start.
Maybe the traveller is on an object with one mile in circumference. It just took three tests to determine that. Remember, baby steps. The P85 will soon be a globetrotter.
Am I drunk when I do this?
Re: "...You walk one mile south, one mile west, and one mile north. You end up exactly where you started. Where are you?" Nowhere in the question is the proviso "after which" or any condition of not using transport other than walking stated... as in "...one mile west, and one mile north AFTER WHICH you end up exactly where you started. Where are you?" So, as this was not stated, I could have hopped a plane from the landing point back to the start point. Not using transport might be "implied" in the question , but that's only a personal matter of interpretation. It's not actively forbidden. Furthermore, the question says "You're standing on the surface of the earth", in which could be argued that it is immediately ruling out the north pole, unless, of course, ICE is considered "the surface of the earth" . A geologist might be the one to ask this question to, if Ice is "the surface".. I suspect that this more lengthy response might be part of the answer Musk expected, because the "north pole" answer is so patently obvious that it, by itself , proves nothing intelligence wise !
That's a great question a very appropriate! If you want a soft landing, probably you should use both, but trying to land, even worse, on a sea platform, a relatively narrow cylinder, just like people imagined it to happen in the 1st part of the 20th C, is plain crazy. But then Mr. Musk's craziness has made him billions.
Answer: Butter the bottom
(alt: affix cat to superstructure)
Do both for redundancy
THE SOFTWARE, IT NO WORKY!!!
I thought the answer to where are you was: in a whole lot of trouble.
What kind of scientist uses miles instead of metric?
What does Elon really want to know ?
1) Do you think outside the box ? - North Pole is the wrong answer.
2) Are you a math geek ? - North Pole is the wrong answer.
3) Are you the sort who recognizes that the lack of a unique answer and protests the fairness of the question? - North Pole is probably still the wrong answer
4) Will you embrace the KISS principle? - North Pole is the RIGHT answer.
The form of the teaser that I originally heard is ...
"You're standing on the surface of the Earth. You walk one mile south, one mile west, and one mile north. You end up exactly where you started and you see a bear. What colour is the bear?"
You wouldn't be an neither pole; you're south of it.
Equator makes much more sense.
But it does require extra fuel. I'd have expected that fuel to be more than the weight of a parachute system, though perhaps not: it would be lowering a mostly-empty tin can.
I imagine that it's a bonus to be able to have that kind of precision on your rocket engines: if you can get them down, then it may provide advantages in going up. Certainly it's nice that you've proven that kind of control.
I applied to take out the garbage!
So I'm sure I'm missing something here:
Radius of earth ~ r = 3963 mi
radii of rings that are fractions of a mile : a = 1/(2*pi*n)
distance N of S pole based on an angle theta = arc length = r * theta
using sine for the right triangle between the center of the earth and the circular section with the circumferences we want:
sin(theta) = a/r (it's a right triangle to the circular section)
So then take the easy case, where the circumference should be 1 mile:
a = 1/(2*pi)
solve for the arclength
= theta * r
= arcsin( 1/(2*pi) * 1/r ) * r
= 0.159
Meaning the point where the circumference of the earth is 1 mile is already closer to the south pole than 1 mile... so how would there be these "rings" people keep talking about?
The equator.
My brain was not teased. it was bored.
If you are going to be an engineer at SpaceX you probably want to bone up on your spherical coordinate system. Two dimensional calculations aren't great for getting to and landing on Mars. Sadly, I have forgotten mine so can't give you an exact answer, but my response to Elon would be that it would be any number of points along the longitude approximately 1.15 miles north of the south pole and that I would need to get back to him with a more accurate answer.
You are on the surface of the Earth, which it's where you've started. - focus on the question, not on the solution.
There are other ways of looking at the problem:
"You're standing on the surface of the Earth. You walk one mile south, one mile west, and one mile north. You end up exactly where you started. Where are you?"
Other posters have pointed out that "Where are you?" is ambiguous and could mean a Simon says sort of answer like "I'm in your office, Mr. Musk." And also that it could be taken to mean relative to a Sun-centered coordinate system. This latter requires waiting N years to return to the same part of the Earth's orbit.
Once one notices that no time limit is required you get many more solutions by allowing for the polar motion over some period of time: http://en.wikipedia.org/wiki/P... - that is, the pole isn't in the same place at the end as at the beginning.
Then there's the notion of repeating the exercise at the north and south magnetic poles (and perhaps geomagnetic). But there is also no explicit constraint that south, west and north are all interpreted the same - they need not all be geographic or all magnetic. In that case there are families of solutions near each of the four poles that interpret the initial motion one way and the final mile the other.
And then the magnetic poles wander much more rapidly (several miles per year) than the geographic poles and over much more than the mile allowed (http://en.wikipedia.org/wiki/South_Magnetic_Pole), so you can put constraints on the time period allowed for the exercise while exploring solutions covering motions over a few weeks.
How hard is that.. seriously.
Well there is bound to be some shit floating around any gravity well. As long as we are talking spherical cows in a vacuum just make the massless parachute larger? How do you actually define "atmosphere" anyways?
Say we want to land on Mars. The atmosphere is 100 times less dense than on Earth, so we'll need 100 times more parachute. I'm sure that's still a lot less mass and complexity than the balancing rockets...but what if we want to make a round trip, and need to land on Mars and Earth?
We're going to need parallel parachute systems of different sizes, or a parachute that can be re-packaged combined with variable unfurling, and suddenly the parachute option is looking a lot more complicated. On the other hand, if you get the balancing rockets to work, you can use them anywhere, over and over again.
.: Semper Absurda
Consider this...suppose you are just over a mile from the SOUTH pole. You walk a mile south - and now you're maybe a hundred feet from the South pole. Then you turn west and start walking...around and around in a tiny 100 foot radius circle centered on the pole. When you've finally clocked up a mile - you turn and head North again...where do you end up?
Well, the answer depends on the exact circumference of the circle that you walked around. Generally, you'll end up someplace very different from your starting point...BUT if that circle is an EXACT sub-multiple of a mile - then you'll end up precisely where you started.
So...the North pole is clearly NOT a unique answer.
Furthermore - the north pole is only ONE answer. My approach reveals an infinite number of possible answers:
1) You could have started ANYWHERE that's at the exact right distance from the pole - so anywhere on that circle will do...an infinite number of starting points will work.
2) Note that ANY exact sub-multiple of a mile will do - so with mathematical precision, there are an infinite number of sub-multiples of a mile - and hence an infinite number of distances from the pole where you could have started.
Truly - the "North Pole" example exhibits very little lateral thinking... if that was your answer then you **FAILED** the Musk test...which (I'm pretty sure) is the whole point here.
The original version of the story is that a hunter walk a mile south, a mile west, shoots a bear, then walks a mile north to return to his starting point. What color was the bear?
Since there are no bears at the south pole - and only polar bears live anywhere near the north pole - then the north pole is the right place and the correct answer is "WHITE!"....but Musk isn't asking *that* question...he's trying to trick people into jumping to a false conclusion without stopping to think about it.
-- Steve Baker
www.sjbaker.org
I think it depends on your frame of reference. North Pole and the various rings around the south pole are correct if you want to end up in the same location with reference to the earth. If you observe the situation from the sun, there's no possible point, since the earth moves while you walk. If you observe the situation with yourself as the frame of reference, any point will do, since you will always end up where you are...
I gave up sigs almost a year ago.
EVERY west-bound portion is a curved line.
The correct answer is either the Geographic North Pole, or the Magnetic North Pole, depending on wether you use a GPS or a magnetic compass to guide you. The two poles are some distance apart - only 1600 km/1000 ter. mi.
I did the test. I started in Belgium and walked one mile south, one mile west and one mile north and I was still in Belgium. Now can we talk about salary details?
If someone answered Lost Woods Maze he/she would have made my day.
GO NORTH, WEST, SOUTH, WEST TO THE FOREST OF MAZE
the simplest answer is "still on the surface of the earth," of course. everything else is an overreaction based on irrelevant information.
Maybe testing to see if the person tends to over-complicate things?
As long as you walk as fast as the earth rotates, and you go north the same speed you came south, you would have finished where you started. I am guessing that it would be easier to match the speed of the earth's rotation nearer to one of the poles.
north pole is just easy and probably where most, even the uninformed, would probably guess first.