What strikes me about this thread is the huge number of people that want to "learn to fly an airplane from a book".

The future of humanity relies on a guy that's probably going to kill himself 10 minutes after finding the nearest airfield.

## Search found 14 matches

- Sun Dec 11, 2011 4:11 pm UTC
- Forum: General
- Topic: You are the last person left on earth. What do you do?
- Replies:
**256** - Views:
**46751**

- Sat Sep 24, 2011 1:39 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0955: "Neutrinos"
- Replies:
**159** - Views:
**44490**

### Re: 0955: "Neutrinos"

I am a first year undergrad physicist, and so my knowledge of particle physics is fairly rudimentary.

Are neutrinos more or less weakly interacting than photons?

That is, is it possible that neutrinos interact with an imperfect vacuum less than photons do, explaining the minor speed difference?

Are neutrinos more or less weakly interacting than photons?

That is, is it possible that neutrinos interact with an imperfect vacuum less than photons do, explaining the minor speed difference?

- Fri Apr 22, 2011 4:23 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0889: "Turtles"
- Replies:
**207** - Views:
**60283**

### Re: 0889: Turtles

Are turtles self aware?

- Sat Nov 13, 2010 10:37 pm UTC
- Forum: Mathematics
- Topic: Inverse matrices and the determinant
- Replies:
**4** - Views:
**3179**

### Re: Inverse matrices and the determinant

Thank you guys.

I have figured that (I+A)(I-A) = I^2 - A^2 = I

so the inverse of (I-A) in the A^2 = 0 case is (I+A)

similarly in the A^3 case (I+A+A^2)(I-A) = I

so the inverse is the geometric series 1 + A + A^2 + ... + A^(n-1)

I have figured that (I+A)(I-A) = I^2 - A^2 = I

so the inverse of (I-A) in the A^2 = 0 case is (I+A)

similarly in the A^3 case (I+A+A^2)(I-A) = I

so the inverse is the geometric series 1 + A + A^2 + ... + A^(n-1)

- Sat Nov 13, 2010 9:56 pm UTC
- Forum: Mathematics
- Topic: Inverse matrices and the determinant
- Replies:
**4** - Views:
**3179**

### Inverse matrices and the determinant

This is homework, I'll post what I've done so far. Let A be a square matrix. Given A^2 = 0, show that (I-A) is invertible. (then extend this to A^n) I can see that if A^n = 0 then det(A) must be zero (as det0 = 0) and so A isn't invertible. How can I go from here to showing that det(I-A) is nonzero?...

- Thu Apr 08, 2010 9:48 pm UTC
- Forum: Science
- Topic: Humans born on Mars
- Replies:
**58** - Views:
**5393**

### Re: Humans born on Mars

Do you mean ~0.38g?

edit: Hahaha, it's a tilde when I type it, the board converts to a dash. What the hell?

edit: Hahaha, it's a tilde when I type it, the board converts to a dash. What the hell?

- Thu Apr 08, 2010 3:25 am UTC
- Forum: Science
- Topic: A physics question.
- Replies:
**7** - Views:
**1002**

### Re: A physics question.

I am too lazy to make a diagram right now, but as a thought exercise, you're walking up a hill. The hill in this sense is your "plane". When it's at zero degrees, gravity's force is completely perpendicular to the plane, 9.81m/s^2. As the hill gets steeper, you're still walking on the plan...

- Sun Apr 04, 2010 11:16 am UTC
- Forum: Science
- Topic: Why does c =c ?
- Replies:
**32** - Views:
**4227**

### Re: Why does c =c ?

thoughtfully wrote:The clearest way of seeing c as a maximum speed is to see it as the only speed (in all four dimensions of spacetime)

Wow. I love physics.

- Fri Apr 02, 2010 6:33 pm UTC
- Forum: Science
- Topic: Why does c =c ?
- Replies:
**32** - Views:
**4227**

### Re: Why does c =c ?

Light doesn't "accelerate". It always travels at c. Even in a refractive medium, photons themselves travel at c before being absorbed/reemitted (the act of which slows them down). I believe that certain properties of vacuum prevent light from traveling faster/slower than it does, I'm only ...

- Tue Mar 30, 2010 1:47 am UTC
- Forum: Mathematics
- Topic: Changing complex coordinates to trigonometric form.
- Replies:
**5** - Views:
**974**

### Re: Changing complex coordinates to trigonometric form.

skeptical scientist is of course correct, however I always found that this was easier thinking geometrically. You can see from the diagram theta is 180deg + the angle in the triangle. Now just take the triangle, adjacent side is (3/2), hypotenuse 3, the ratio adj/hyp is 1/2. 1/2 is of course cos60 f...

- Sat Feb 13, 2010 1:41 am UTC
- Forum: Science
- Topic: Regression of Cooked State into an Uncooked State
- Replies:
**37** - Views:
**8747**

### Re: Regression of Cooked State into an Uncooked State

A simpler thought experiment is "unbreaking a ming vase". You have a ming vase on the edge of a table. It falls off, shattering on the ground. Imagine if all of the parts of the ming vase exactly reversed their direction. They would have enough energy to fly together, recrystallise the br...

- Fri Nov 20, 2009 4:26 pm UTC
- Forum: Science
- Topic: The energy efficiency of boiling cold vs hot tap water.
- Replies:
**30** - Views:
**3265**

### Re: The energy efficiency of boiling cold vs hot tap water.

I would imagine the boiler has a far easier job heating the water due to insulation.

- Sun Nov 01, 2009 12:06 pm UTC
- Forum: Science
- Topic: Physics Question
- Replies:
**9** - Views:
**1585**

### Re: Physics Question

Yeah, in that situation you could just turn the rockets off for .0000000000000001 seconds and just treat it as if you never even stopped...

- Sun Oct 18, 2009 8:55 pm UTC
- Forum: Mathematics
- Topic: Circles and squares
- Replies:
**1** - Views:
**497**

### Circles and squares

Hello, this is my first post on the xkcd boards :) My problem is such (not so much homework but just something I am reading into) http://i108.photobucket.com/albums/n39/mredgey/circles.png I need to find the length of "x" (in terms of r). The way I am approaching it is to use the right ang...