## Search found 190 matches

- Mon Mar 30, 2009 5:15 pm UTC
- Forum: Science
- Topic: Global Warming Fail.
- Replies:
**22** - Views:
**3030**

### Re: Global Warming Fail.

Launch the excess sea-water into the sun.

- Fri Mar 20, 2009 8:24 pm UTC
- Forum: Mathematics
- Topic: Alternative definitions of the derivative
- Replies:
**15** - Views:
**2176**

### Re: Alternative definitions of the derivative

Distributions are a generalization of functions that let you do more things with them. For example, the "derivative" of the Heaviside step function is the Dirac delta function. Distributions are defined in terms of their integrals. So, even though the delta function carries an "infini...

- Mon Mar 09, 2009 6:39 pm UTC
- Forum: Mathematics
- Topic: Graph: F(x)=x^∞
- Replies:
**25** - Views:
**3147**

### Re: Graph: F(x)=x^∞

∞ is not an integer and therefore even and odd don't really make sense for it. Compare: Is 3.5 even or odd? pi? \sqrt 2? Neither even nor odd works for ∞ if you try to use naive infinite math on it, either. ∞ + ∞ = ∞, so ∞ must be even. But, ∞ + 1 = ∞, so ∞ must be odd. It just doesn't work. So the ...

- Thu Feb 26, 2009 7:22 pm UTC
- Forum: Science
- Topic: Kelvin double bridge?
- Replies:
**2** - Views:
**1167**

### Re: Kelvin double bridge?

My guess, and I know almost nothing about circuits, is that the leftmost path is the original circuit, so you don't exactly "need" it, but you are probably not going to remove it either.

- Fri Feb 13, 2009 5:47 pm UTC
- Forum: Science
- Topic: Neutrinos and the expansion of the Universe.
- Replies:
**11** - Views:
**1048**

### Re: Neutrinos and the expansion of the Universe.

I think what you're saying is, given a fixed density for the universe, any additional mass must increase the size of the universe. I think we have calculated the size of the universe independently of its mass or density. In fact, our calculation of the universes size was too large to account for its...

- Tue Feb 10, 2009 1:10 pm UTC
- Forum: Mafia
- Topic: The Gojoe Memorial Mafia Discussion Thread
- Replies:
**32706** - Views:
**2501484**

### Re: Forum-Mafia Discussion/Recruitment/Gojoe canNEVER be trusted

I will gladly fill in for anyone who needs a replacement.

- Tue Feb 10, 2009 1:05 pm UTC
- Forum: Science
- Topic: Charged Black Hole
- Replies:
**27** - Views:
**3003**

### Re: Charged Black Hole

Remember that in relativity, different observers can have different notions of time. Part of the reason that black holes are confusing is that different observers have very different notions of time. If a particle falls into a black hole, an observer far away from the black hole would calculate it a...

- Sun Feb 08, 2009 6:51 pm UTC
- Forum: Science
- Topic: Charged Black Hole
- Replies:
**27** - Views:
**3003**

### Re: Charged Black Hole

There would be an electromagnetic field around the black hole, outside the event horizon.

- Sat Feb 07, 2009 6:18 am UTC
- Forum: Movies and TV Shows
- Topic: Look around you
- Replies:
**5** - Views:
**1242**

### Look around you

Look around you is a very amusing show. It takes the form of one of those old science shows, but the science is completely bogus. The bell isn't broken. In fact it's in perfect working order. It's just that when bumcivilian is produced, it has the effect of sucking up all the sound in the vicinity. ...

- Fri Feb 06, 2009 5:43 pm UTC
- Forum: Mathematics
- Topic: How does the cartesian product relate to other products?
- Replies:
**30** - Views:
**2986**

### Re: How does the cartesian product relate to other products?

In Nathaniel's definition of a matrix, a 3x3 matrix is just a list of 9 real numbers, so it can be defined as a function with takes as input one of the nine positions of the matrix and takes as output whichever element of the matrix is in that position. Linear algebra takes advantage of the fact tha...

- Fri Feb 06, 2009 6:02 am UTC
- Forum: Mathematics
- Topic: How does the cartesian product relate to other products?
- Replies:
**30** - Views:
**2986**

### Re: How does the cartesian product relate to other products?

The identity matrix in three dimensions can be defined either as I: m:{1,2,3}x n:{1,2,3} -> r:R where r=1 if m=n and r=0 if m=/=n or as the function I: x:R

^{3}-> y:R^{3}where y=x. Both are valid and useful depending on what aspect of matrices you're studying.- Fri Feb 06, 2009 5:03 am UTC
- Forum: Mathematics
- Topic: How does the cartesian product relate to other products?
- Replies:
**30** - Views:
**2986**

### Re: How does the cartesian product relate to other products?

That's a horrible way to define a matrix. It's a fine way to define a matrix, depending on your context. In particular, if you want to deal with higher-dimensional matrices, then that's a very good definition to use, since you can just slap on d cartesian products, where d is the dimension you want...

- Thu Feb 05, 2009 1:46 pm UTC
- Forum: Forum Games
- Topic: Post next in this thread and
- Replies:
**80** - Views:
**6997**

### Re: Post next in this thread and

Can it be hugz tiem nao?

The next person to post in this thread will divide by zero.

The next person to post in this thread will divide by zero.

- Sat Jan 31, 2009 9:40 pm UTC
- Forum: Mathematics
- Topic: Stacked Hypercube Vertex Convex Hull Boundary Minimization
- Replies:
**6** - Views:
**734**

### Re: Stacked Hypercube Vertex Convex Hull Boundary Minimization

For example, if n=2 and h=4 you assign:

(0,0) -> 1

(1,0) -> 2

(0,1) -> 3

(1,1) -> 4

The level set for 2 goes from (0,0.5) to (1,0). so r is [imath]\sqrt 5 / 2[/imath].

This is the minimal arrangement.

(0,0) -> 1

(1,0) -> 2

(0,1) -> 3

(1,1) -> 4

The level set for 2 goes from (0,0.5) to (1,0). so r is [imath]\sqrt 5 / 2[/imath].

This is the minimal arrangement.

- Fri Jan 30, 2009 7:01 pm UTC
- Forum: Mathematics
- Topic: Stacked Hypercube Vertex Convex Hull Boundary Minimization
- Replies:
**6** - Views:
**734**

### Re: Stacked Hypercube Vertex Convex Hull Boundary Minimization

Choose h vertices from a n-dimensional hypercube. Assign each point a "Temperature" T from 1 to h, without replacement. The temperature varies linearly between the points. Minimize the size of all the isothermal surfaces.

- Fri Jan 30, 2009 6:26 pm UTC
- Forum: Mathematics
- Topic: The continuous elevator
- Replies:
**15** - Views:
**1974**

### Re: The continuous elevator

In other words, he's saying a restaurant where two people each wait 30min (30 2 +30 2 =1800) is better than one where one person waits 5min and another waits 45min (5 2 +45 2 =2050). I think the a good solution would be to create a potential function P(x|y,t) for each dot that depends on where and w...

- Thu Jan 22, 2009 7:25 pm UTC
- Forum: Mathematics
- Topic: Argh... what am I not seeing? (homework problem)
- Replies:
**14** - Views:
**1993**

### Re: Argh... what am I not seeing? (homework problem)

Sorry, I meant e

^{x}[imath]\neq[/imath] -3.- Thu Jan 22, 2009 7:02 pm UTC
- Forum: Mathematics
- Topic: Argh... what am I not seeing? (homework problem)
- Replies:
**14** - Views:
**1993**

### Re: Argh... what am I not seeing? (homework problem)

ln(x) [imath]\neq[/imath] -3 for any x

- Thu Jan 22, 2009 6:56 pm UTC
- Forum: Logic Puzzles
- Topic: Gravity, Acceleration, or Centrifugal Force?
- Replies:
**19** - Views:
**3246**

### Re: Gravity, Acceleration, or Centrifugal Force?

Never mind that all three of those cases are gravity.

- Tue Jan 20, 2009 4:58 am UTC
- Forum: Science
- Topic: Freezing Water
- Replies:
**18** - Views:
**1749**

### Re: Freezing Water

You could try insulating either the cage, the bottle, or the metal spout. If you occasionally shake the bottle, that should stop the bottom from freezing first.

- Tue Jan 20, 2009 4:14 am UTC
- Forum: Logic Puzzles
- Topic: Outsmarting the Genie
- Replies:
**257** - Views:
**25232**

### Re: Outsmarting the Genie

I wish for whatever would be best for me.

- Tue Jan 20, 2009 4:02 am UTC
- Forum: Logic Puzzles
- Topic: Cutting The Cake
- Replies:
**14** - Views:
**2563**

### Re: Cutting The Cake

Consider all the intersection points of the cake. Consider the partition of these intersections such that two points are in the same partition if they are connected by a cut. Before cutting, there are 122 partition sets: one for all the boundary points, and one for each interior point. Consider maki...

- Wed Jan 14, 2009 7:25 pm UTC
- Forum: Mathematics
- Topic: Beginner Stuff
- Replies:
**23** - Views:
**2383**

### Re: Beginner Stuff

There is nothing wrong with repeating elements in a set. Writing "A={(9,0), (8,2), (7,3), (8,2)}" means "(9,0) is in A, (8,2) is in A, (7,3) is in A, and (8,2) is in A." Sure, it's redundant, but I wouldn't go so far as to call it wrong. More relevant to the OP's question, though...

- Sun Jan 11, 2009 5:37 pm UTC
- Forum: Science
- Topic: Pair Production
- Replies:
**6** - Views:
**1143**

### Re: Pair Production

http://en.wikipedia.org/wiki/Pair_production

According to wikipedia, pair production can't occur from a single photon, but it has more to do with conservation laws than antiparticles.

According to wikipedia, pair production can't occur from a single photon, but it has more to do with conservation laws than antiparticles.

- Tue Jan 06, 2009 7:52 am UTC
- Forum: Logic Puzzles
- Topic: Tarot
- Replies:
**18** - Views:
**2139**

### Re: Tarot

I would ask 'Will I receive the bottom card from the deck before the top card?', proving that the fortune teller is inaccurate.

- Wed Dec 24, 2008 1:00 am UTC
- Forum: Mathematics
- Topic: Fractals, baby! Vote now!
- Replies:
**45** - Views:
**8326**

### Re: Fractals, baby! Vote now!

The coastline of Britain is a fractal. It has a fractal dimension of 1.25. Granted, it may not be an exact fractal as the coastline itself is poorly defined at smaller scales, but it is statistically self-similar at all larger scales.

- Thu Dec 18, 2008 2:12 am UTC
- Forum: Logic Puzzles
- Topic: Slot machines
- Replies:
**9** - Views:
**2028**

### Slot machines

A casino has two types of slot machines available: a nickel machine which takes 5 cent bets and pays out 40 cents every 1 in 10 games, and a quarter machine which takes 25 cent bets and pays out 225 cents every 1 in 10 games. As a casino owner, which machine should you install more of? As a player, ...

- Tue Dec 16, 2008 6:05 am UTC
- Forum: Science
- Topic: Downwind faster than the wind
- Replies:
**262** - Views:
**31777**

### Re: Downwind faster than the wind

It is important to be very careful about which frame of reference you are in. Also, you seem to be disregarding contributions to kinetic energy and momentum from the ground. In the ground frame, the propeller takes energy from the air, and gives it to the vehicle. In the air speed frame, the vehicle...

- Thu Oct 30, 2008 4:32 pm UTC
- Forum: Logic Puzzles
- Topic: Quantitative Analysis riddle
- Replies:
**13** - Views:
**2113**

### Re: Quantitative Analysis riddle

since P(+) must be nonzero (otherwise he could not have gotten a positive test) Just because something happens doesn't mean its probability is non-zero. We should take P(+)=0. Then Bayes Theorem gives P(G|+)=P(+|G)P(G)/P(+)=0/0. Or, to rewrite: P(G|+)P(+)=P(+|G)P(G)=0. This is satisfied for any pro...

- Thu Oct 30, 2008 4:14 pm UTC
- Forum: Logic Puzzles
- Topic: 2 simultaneous chess games (simple solution)
- Replies:
**20** - Views:
**4126**

### Re: 2 simultaneous chess games (simple solution)

Perhaps she has a strategy for Chess that proves either a win for white or a win for black. By playing her strategy perfectly, she guarantees at least one win (assuming she plays white in one game and black in the other).

- Thu Aug 07, 2008 4:33 pm UTC
- Forum: Language/Linguistics
- Topic: What is a "climax"? (In literary terms.)
- Replies:
**11** - Views:
**3991**

### Re: What is a "climax"? (In literary terms.)

The climax is the point of greatest tension in the story. It is usually followed immediately by the resolution. It is not usually found in the middle of the story.

- Sat May 17, 2008 7:11 pm UTC
- Forum: General
- Topic: Writing Badly (you can too!)
- Replies:
**40** - Views:
**9536**

### Re: Writing Badly (you can too!)

I recall "Half-Life: Full-Life Consequences" as a particularly poorly written example of awful fan fiction.

- Sat Mar 29, 2008 6:23 pm UTC
- Forum: Logic Puzzles
- Topic: Pi litres
- Replies:
**17** - Views:
**3552**

### Re: Pi litres

If you have a string, you can wrap it around the cylinder to get the length 2πR. Then draw it across the cylinder to get the length 2R. Use those two length to construct a right triangle with base 4R and height πR. Use that triangle and the height of the cylinder to construct the length (π/4)H. Fill...

- Fri Mar 28, 2008 12:43 pm UTC
- Forum: Mathematics
- Topic: Exponents using only addition and subtraction
- Replies:
**9** - Views:
**2185**

### Re: Exponents using only addition and subtraction

There's always Taylor polynomials. I think most calculators use Taylor polynomials or some variant to calculate trigonometric functions. The Taylor polynomial for that function is 1 + [ln2(x-69)/12]

It should converge rather quickly.

^{1}/2! + [ln2(x-69)/12]^{2}/3! +[ln2(x-69)/12]^{3}/4! + . . .It should converge rather quickly.

- Sat Mar 15, 2008 8:26 pm UTC
- Forum: Mathematics
- Topic: Pi, Monkeys, and Shakespeare
- Replies:
**27** - Views:
**3283**

### Re: Pi, Monkeys, and Shakespeare

The usual definition of "natural" or "unnatural" sequences or sets is to imagine a computer program (in some programming language) that would print the result. Or you could use a natural language like English. For example, "110100000101110" falls into the category "...

- Wed Mar 12, 2008 6:32 am UTC
- Forum: Religious Wars
- Topic: Which of Valve's creative guns doyou want?
- Replies:
**120** - Views:
**20119**

### Re: Which of Valve's creative guns doyou want?

Well, the storage cube would have to be large enough to accommodate a portal, which would make it too big to fit through a portal. Even if you had a rectangular shape, it would just get stuck partway through the portal. You're not imaginative enough. Pop one on a piece of plywood and the other on t...

- Wed Mar 12, 2008 5:49 am UTC
- Forum: Forum Games
- Topic: Haiku.
- Replies:
**316** - Views:
**37773**

### Re: Haiku.

Oh, pentameter

You are so full of iambs

but not in haiku.

You are so full of iambs

but not in haiku.

- Wed Mar 12, 2008 5:46 am UTC
- Forum: Logic Puzzles
- Topic: Can you pick out what's wrong here?
- Replies:
**9** - Views:
**2958**

### Re: Can you pick out what's wrong here?

Would this be a good place to post similar puzzles? My favorite was always:

2πi = ln(e

2πi = ln(e

^{2πi})=ln(1)=0- Wed Mar 12, 2008 1:11 am UTC
- Forum: Logic Puzzles
- Topic: Can you pick out what's wrong here?
- Replies:
**9** - Views:
**2958**

### Re: Can you pick out what's wrong here?

Well, precisely which step is wrong depends on your definition of the square root. Step 2 is wrong because the square root is multi-valued. If you have a single-valued square root with an appropriate branch cut, then step 3 is no longer correct. Steps 1, 4 and 5 are always correct with standard def...

- Tue Mar 11, 2008 3:20 am UTC
- Forum: Religious Wars
- Topic: Which of Valve's creative guns doyou want?
- Replies:
**120** - Views:
**20119**

### Re: Which of Valve's creative guns doyou want?

Here's a thought experiment: suppose portals could be attached to weighted storage cubes and that they didn't disappear when the surface moved. What would happen if you put a portalled cube through a portal on the wall? Well, the storage cube would have to be large enough to accommodate a portal, w...