Search found 436 matches

by lgw
Fri Apr 26, 2013 7:39 pm UTC
Forum: Science
Topic: Could we launch a probe at a star to get a better look?
Replies: 10
Views: 2008

Re: Could we launch a probe at a star to get a better look?

According to this , a solar sail with a magnetic beam transmitter (producing its own "solar wind") could conceivably get up to 1/10 light speed. So it would take "only" 12,000 years for such a probe to get to Kepler-62. Or 42 years to get to Proxima Centauri, 4.2 light-years awa...
by lgw
Fri Apr 26, 2013 6:37 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1204: "Detail"
Replies: 76
Views: 16782

Re: 1204: "Detail"

It's basically "how far can you zoom". A resolution of one meter would mean everything within a given 1m square on the ground would show up as just a block of a single color, i.e. one pixel. Repeat after me: A pixel is not a little square. A pixel is not a little square. A pixel is not a ...
by lgw
Fri Apr 26, 2013 6:27 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1204: "Detail"
Replies: 76
Views: 16782

Re: 1204: "Detail"

Next time I need to ascertain the mass of a log, I'll be sure to use a log scale. ------------ Years ago I saw a box - a large crate, actually, a bit bigger than a large refrigerator/freezer. It was on a wheeled platform, and was being VERY slowly and carefully guided down the rather steep sidewalk...
by lgw
Thu Apr 25, 2013 12:03 am UTC
Forum: Fictional Science
Topic: The Light Saber problem
Replies: 122
Views: 65894

Re: The Light Saber problem

Reasoning just within the logic of the film, both light saber blades and blaster bolts are plasma contained in some sort of force field, a force field that passes through most common objects, but can't pass through other instances of the same kind of force field. That would explain: ⋅ The ...
by lgw
Tue Apr 23, 2013 5:26 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1202: "Girls and Boys"
Replies: 138
Views: 40264

Re: 1202: "Girls and Boys"

My university is doing a campaign at the moment where they get people to write "I need feminism because..." along with a reason on a whiteboard, they take a photo and put it on their website. I've already done one, but I'm very tempted to do another with today's comic drawn on it. I'm sur...
by lgw
Mon Apr 22, 2013 7:19 pm UTC
Forum: Computer Science
Topic: Level of education
Replies: 11
Views: 7938

Re: Level of education

. . .it's rare to need more than a BS . . . higher education is a plus, but not a requirement. This. I have no degree whatsoever (at any level, in any field), and yet I work as a senior software engineer. ... Same situation here. I found working for a living soul-satisfying in a way that toy proble...
by lgw
Wed Apr 17, 2013 8:42 pm UTC
Forum: Science
Topic: Thrust of a propeller
Replies: 1
Views: 692

Re: Thrust of a propeller

Propellers are wings, in a special case where different parts of the wing have different speeds of airflow over them (which is why many propeller blades have a "twist" to them, to have an angle of attack that varies appropriately with the speed of that part of the blade). You calculate thr...
by lgw
Wed Apr 17, 2013 8:32 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1200: "Authorization"
Replies: 47
Views: 17222

Re: 1200: "Authorization"

My home computer does auto-login on boot (no security at all if you have physical possession), but I do all my financial activity from an encrypted VM that I don't use for anything else. I really need to get around to moving all my financial email addresses to an account that's not used for anything...
by lgw
Tue Apr 16, 2013 8:37 pm UTC
Forum: Science
Topic: Making vacuum with high speed cars driving behind eachother
Replies: 6
Views: 1919

Re: Making vacuum with high speed cars driving behind eachot

It's no where near a vacuum, it's just that a bit-less-dense air is really noticeable. If your car is drag-limited at top speed, then a 10% reduction in drag would mean about 10% higher top speed, which you'd otherwise need about 30% more power to accomplish. That's because top speed goes with cube ...
by lgw
Fri Apr 12, 2013 9:32 pm UTC
Forum: Science
Topic: Gravity at universal scale
Replies: 1
Views: 579

Gravity at universal scale

Why would gravity act to pull objects in the universe together "non-locally" - that is, at the largest scale? From our point of reference here on Earth, the universe (at large enough scale) is a sphere of uniform density extending to an event horizon several billion light years away (event...
by lgw
Fri Apr 12, 2013 9:19 pm UTC
Forum: Science
Topic: Is there any way to overcome the expansion of the universe?
Replies: 5
Views: 2152

Re: Is there any way to overcome the expansion of the univer

What might there be in the universe's past that we've already missed out on completely, and is now lost forever? So far it seems that the universe is larger than the visible universe. Given what I understand from inflation theory, the universe is arbitrarily larger than the visible universe - there...
by lgw
Fri Apr 12, 2013 7:00 pm UTC
Forum: What If?
Topic: What-If 0040: "Pressure Cooker"
Replies: 117
Views: 58096

Re: What-If 0040: "Pressure Cooker"

I was totally going to link to Things I Won't Work With except Randall did it already. :-) If you don't click on links in what-if posts usually, this one comes highly recommended. I think my favorite entry is this one: "In a comment to my post on putting out fires last week, one commenter ment...
by lgw
Fri Apr 12, 2013 12:09 am UTC
Forum: Science
Topic: Acceleration near a black hole
Replies: 18
Views: 5788

Re: Acceleration near a black hole

My understanding from the Wikipedia article was that the distant observer saw both the infaller accelerate to approaching infinity, and the infaller's time dilation approaching infinity, and that the two neatly cancelled to recover Newton for the infaller (but as I've said, I found it not at all cle...
by lgw
Thu Apr 11, 2013 8:51 pm UTC
Forum: Science
Topic: Acceleration near a black hole
Replies: 18
Views: 5788

Re: Acceleration near a black hole

As time and distance are measured in a given frame, F=ma, so the thrust calculation isn't any different from the value you claim to be asking for. You should probably learn more about the physics we're discussing before you decide to be condescending about our answers. I don't see where I was being...
by lgw
Thu Apr 11, 2013 7:14 pm UTC
Forum: Science
Topic: Acceleration near a black hole
Replies: 18
Views: 5788

Re: Acceleration near a black hole

Thanks for a helpful reply, though wikipedia is nearly gibberish in that section, as it so often is on physics topics. If you're asking from the perspective of the infalling observer, it's infinite for all black holes, in the sense that no finite outward force could prevent you from falling in. I wa...
by lgw
Thu Apr 11, 2013 6:21 pm UTC
Forum: Science
Topic: Acceleration near a black hole
Replies: 18
Views: 5788

Re: Acceleration near a black hole

The acceleration near a black hole is not a particularly useful concept. An infalling observer is freefalling so, by the equivalence principle, they are not experiencing any proper acceleration. The acceleration a distant observer sees will be dependent on the gravitational field where that observe...
by lgw
Thu Apr 11, 2013 5:22 pm UTC
Forum: Science
Topic: Acceleration near a black hole
Replies: 18
Views: 5788

Acceleration near a black hole

I have a seemingly simple question, but googling for the answer brings up nothing but pages of crackpot relativity sites. What's the acceleration of a test particle near the event horizon of a black hole, both in the frame of a distant observer and in the particle's reference frame? The Newtonian ac...
by lgw
Fri Apr 05, 2013 9:02 pm UTC
Forum: Science
Topic: Understanding the speed of light
Replies: 17
Views: 2801

Re: Understanding the speed of light

Stable wormholes are a great answer to FTL travel for SF. If they're big capital-intensive projects, with big rewards in trade opportunities or scientific discovery, then you can write about how different societies address that. Wormholes can in theory cause causality issues, but only in a very cont...
by lgw
Tue Dec 27, 2011 7:13 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0992: "Mnemonics"
Replies: 278
Views: 65137

Re: 0992: "Mnemonics"

The next person to post the old, shitty misogynistic (and intermittently racist) resistor code like they're being adorably transgressive or otherwise wax excited about it is going out the door. Wow, I had no idea this forum was so obsessively Basically Decent. I feel regret and sadness for ever pos...
by lgw
Mon Nov 28, 2011 9:26 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0982: "Set Theory"
Replies: 55
Views: 14903

Re: 0982: "Set Theory"

It is sometimes observed that, for a proof to be valid, the author really should state all of the axioms used, including the logical axioms. Aren't there problems with infinite recursion if you try to do this, though? Say we have a simple argument: P .: Q Well, how do we know whether that is valid ...
by lgw
Tue Sep 27, 2011 1:28 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0955: "Neutrinos"
Replies: 159
Views: 44002

Re: 0955: "Neutrinos"

Here is a coincidence. ... So there is an 18 meter block of granite and an 18 meter additional distance traveled. It would be particularly hilarious if this was all a measument error due to an intern getting confused about which side of the block of graphite he was recording the position of. Twice.
by lgw
Fri Apr 15, 2011 8:51 pm UTC
Forum: Computer Science
Topic: implementing "binary or" with arithmetic operators
Replies: 14
Views: 2500

Re: implementing "binary or" with arithmetic operators

A useful trick for most "how do I bash bits fast" questions is to use a lookup table. Does the bytecode support arrays? (I assume your "no ref/deref" means no pointers).
by lgw
Wed Apr 13, 2011 7:51 pm UTC
Forum: Computer Science
Topic: Merging lists in place
Replies: 41
Views: 10848

Re: Merging lists in place

I stumbled across another option: quicksort with a stable partitioning algorithm. The C++ STL provides a stable partitioning algorithm. Their implementation is adaptive; if it can allocate some temporary storage it can run in O(n) just like the normal unstable partition of normal quicksort, and oth...
by lgw
Wed Apr 13, 2011 7:26 pm UTC
Forum: Coding
Topic: Thinking in functional programming
Replies: 28
Views: 6632

Re: Thinking in functional programming

Seconding The Little Schemer - reading The Little Lisper back in the day solved this exact problem for me. It's short and the problems are OK - some are fun.
by lgw
Wed Apr 13, 2011 7:22 pm UTC
Forum: Coding
Topic: Macro Ethics
Replies: 17
Views: 2899

Re: Macro Ethics

On macros in general: * It makes faur(x, ++y) do bad things. * If I accidentaly type (x, <y), this will compile successfully. * I have to really think about whether passing the unsigned 16bit value 0xFFFF will work or not (is it implicity cast to the int -1 or not? and even if it's safe, what if the...
by lgw
Thu Dec 16, 2010 12:52 am UTC
Forum: Computer Science
Topic: Compiling languages into C
Replies: 9
Views: 3225

Re: Compiling languages into C

I've done a bit of this - it used to be a common approach to porting a legacy language to a new platform. C instead of assembly as your object language isn't making this harder, right? You first need to pick a basic strategy to compiling your functional language. To begin with, do you understand con...
by lgw
Thu Dec 16, 2010 12:33 am UTC
Forum: Coding
Topic: intel mul instruction
Replies: 11
Views: 2031

Re: intel mul instruction

From what I understand, integer multiply (and even division) have an "apparant speed" of 1 clock cycle on a modern Intel processor, as long as you're playing nice with the instruction pipelining and branch prediction, and aren't doing two multiplies/divides close to one another. The chip c...
by lgw
Tue Aug 17, 2010 9:29 pm UTC
Forum: Coding
Topic: C++ function argument stack
Replies: 6
Views: 1897

Re: C++ function argument stack

With the Windows compiler there are several options for how it will use the stack, including __fastcall which tries to pass everything in registers and avoid the stack. Sadly, it does matter from time to time whether a function is __stdcall or __cdecl.
by lgw
Thu Jul 15, 2010 11:58 pm UTC
Forum: Computer Science
Topic: OTP encryption and true randomness
Replies: 9
Views: 2488

Re: OTP encryption and true randomness

My friend and I are playing around with one-time pad encryption for fun. We're wondering how important true randomness in the key pad is to the security of the code. We previously agreed upon a popular book that we have been referencing as our key pad. What we've been doing is adding a short string...
by lgw
Thu Jul 15, 2010 11:10 pm UTC
Forum: Coding
Topic: What is good code?
Replies: 38
Views: 6856

Re: What is good code?

This is an idea I was going to put forward, and I'd sum it up in two points. Good code is elegant. Good code is not "clever". The essense of good code is clarity . Your intention should be clearly expressed. It should be easy for a maintainer to understand what you wanted. It should be ea...
by lgw
Thu Jul 15, 2010 10:56 pm UTC
Forum: Coding
Topic: There's more to programming that someone's not telling me.
Replies: 8
Views: 2108

Re: There's more to programming that someone's not telling m

And you want to know whats scary? A huge portion of the windows API is undocumented! Many of the functions actually end up calling undocumented NTDLL functions. http://undocumented.ntinternals.net/ I ran across this in assembly programming. Wanting the fastest possible program, I quickly found out ...
by lgw
Thu Jul 15, 2010 10:31 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0766: "Green Flash"
Replies: 82
Views: 24311

Re: "Green Flash" Discussion

Syzo wrote:"The exact cause of the phenomenon is unknown, but it's thought to be linked to atmospheric refraction and your getting a really cool car. "
It shouldn't be this?


It's correct. "atmospheric refraction and your [act of] getting a really cool car."
by lgw
Tue Jun 01, 2010 8:57 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0747: "Geeks and Nerds"
Replies: 130
Views: 35960

Re: "Geeks and Nerds" Discussion

There certainly seems to be a division between those who associate "socially awkward" with geeks vs nerds. I wonder if this is generational rather than regional? I have a strong association between "nerd" and "socially awkward" that comes from having seen Revenge of the...
by lgw
Tue Apr 13, 2010 12:57 am UTC
Forum: Coding
Topic: Python Editor
Replies: 8
Views: 1599

Re: Python Editor

It's been forever since I've done Pyhton, but I'm getting the itch. Is there a decent Python IDE for Windows? Notepad++ and running the programs in a seperate window is one thing, but I'd love a source-integrated debugger.
by lgw
Tue Apr 13, 2010 12:54 am UTC
Forum: Coding
Topic: The "IT DOESN'T WORK!" thread
Replies: 1958
Views: 556729

Re: The "IT DOESN'T WORK!" thread

Yeah, but he probably doesn't know what's expected and what isn't. There are two solutions: dig into the algorithm and try to grok it sufficiently, or (more practical) find another implementation and trace through that first. Good point: if it's an implementation bug, you can very often find it jus...
by lgw
Mon Apr 12, 2010 11:01 pm UTC
Forum: Coding
Topic: The "IT DOESN'T WORK!" thread
Replies: 1958
Views: 556729

Re: The "IT DOESN'T WORK!" thread

I'm trying to implement md5, but something somewhere is wrong. How do you even start debugging something like this? The same way you can debug anything non-trivial: step through the operation of your program with a debugger and look for where it does something unexpected. This makes most bugs shall...

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