Search found 268 matches

by Certhas
Sun Dec 05, 2010 2:30 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 489615

Re: Favorite math jokes

The mathematician replies: "You must be a manager." "Oh yes, I am. How did you know?" "You see, you don't know where you are and where you are going. You have promised something, you have no idea how to keep this promise, and you expect me to solve your problem. As a matter...
by Certhas
Sun Dec 05, 2010 11:35 am UTC
Forum: Mathematics
Topic: The self defeating object and vagueness...
Replies: 0
Views: 1027

The self defeating object and vagueness...

Just came across this and thought it was rather spectacular. Thought people might like it: http://terrytao.wordpress.com/2010/11/02/the-no-self-defeating-object-argument-and-the-vagueness-paradox/ Terrence Tao shows how to get to deep mathematical results like Turings halting theorem, Gödels undecid...
by Certhas
Mon Sep 27, 2010 4:10 pm UTC
Forum: Mathematics
Topic: Doubts about my physics study: am I smart enough?
Replies: 19
Views: 5715

Re: Doubts about my physics study: am I smart enough?

Rock on! Keep us posted on how it goes!
by Certhas
Sun Sep 26, 2010 4:26 pm UTC
Forum: Mathematics
Topic: Doubts about my physics study: am I smart enough?
Replies: 19
Views: 5715

Re: Doubts about my physics study: am I smart enough?

I think you'll be alright. Proofs are a struggle for many who later successfully study the rest of physics. Also by your dedication and what you've been able to learn yourself it seems like you're plenty smart enough. Remember, the brain is a muscle! University math is just very different than schoo...
by Certhas
Sun Sep 26, 2010 4:18 pm UTC
Forum: Mathematics
Topic: Is this proof sufficient?
Replies: 6
Views: 1517

Re: Is this proof sufficient?

Cross products are not the elementary building block you want to generalise. Rather you'd take n-vectors, wedges and duals. The wedge product of two verctors (called a bivector or 2-vector) is defined a (v ^ w) = v^i w^j - w^i v^j. The dual is defined using the fully antisymmetric symbol epsilon^ij....
by Certhas
Tue Sep 21, 2010 8:46 am UTC
Forum: Science
Topic: Can you swim in a superfluid?
Replies: 26
Views: 4776

Re: Can you swim in a superfluid?

Nicely done. So you could swim by swalloing the liquid and pooping it out. Returning briefly to the propeller idea I think this case is somewhat problematic as vortices are tricky. They are topological defects in the fluid so the standard idea of 0 viscosity fluids might not apply. the rotational mo...
by Certhas
Wed Sep 15, 2010 10:59 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0793: "Physicists"
Replies: 158
Views: 41673

Re: "Physicists" discussion (#793)

This comic would have been (1) funnier and (2) truer if he'd used 'economists' instead of 'physicists'. I mean, really, have you seen an economist at the ASSA meetings? There's a reason they don't let us go near the sociology panels... There's even a term for it -- 'economic imperialism' -- to desc...
by Certhas
Sat Sep 11, 2010 7:28 pm UTC
Forum: News & Articles
Topic: Cambridge University at no. 1 in world ranking.
Replies: 48
Views: 5757

Re: Cambridge University at no. 1 in world ranking.

paulisa wrote:I also agree with Certhas that the specialisation of some european universities hinders high ratings, but that's just the historically grown system. I don't think it would be good to change that just for the rankings.


Obviously! It means we need to change the ratings :)
by Certhas
Sat Sep 11, 2010 7:23 pm UTC
Forum: Mathematics
Topic: Proving a function analytic
Replies: 6
Views: 5228

Re: Proving a function analytic

Well for complex functions it's easier, isn't it? Exactly because complex differentiable and analytic coincide. It seems it would be much harder for functions from R to R?
by Certhas
Sat Sep 11, 2010 7:18 pm UTC
Forum: Serious Business
Topic: Can Female-on-Male Abuse Victims Win at Trial?
Replies: 42
Views: 40003

Re: Can Female-on-Male Abuse Victims Win at Trial?

Regarding domestic violence. It happens. Male victims go to the police. Women get arrested for it. At least in the UK. So it's not impossible, but it's definitely an underappreciated topic. There was a good article in the Independent recently: http://www.independent.co.uk/opinion/commentators/johann...
by Certhas
Thu Sep 09, 2010 3:40 pm UTC
Forum: News & Articles
Topic: Cambridge University at no. 1 in world ranking.
Replies: 48
Views: 5757

Re: Cambridge University at no. 1 in world ranking.

What is always baffling to me: No Universities from anywhere other than the US and Britain? In a world ranking? Really? At ARWU Tokyo is the first non anglo saxon one at 20, the Zurich and Kyoto, Paris-6, Copenhagen etc... The first German one is the University of Munich at 52. Yet if you offer me a...
by Certhas
Mon Aug 30, 2010 10:25 am UTC
Forum: Science
Topic: Reducing the effects of acceleration on the human body
Replies: 123
Views: 17044

Re: Reducing the effects of acceleration on the human body

Which is why filling the whole ship would be stupid. Instead, fill individual horizontal chambers with the fluid, one for each passenger. Still a pressure gradient, but nothing like the difference you'd have over a whole ship or even a single vertical chamber. Sorry for the late answer, didn't see ...
by Certhas
Thu Aug 19, 2010 3:16 pm UTC
Forum: Science
Topic: Reducing the effects of acceleration on the human body
Replies: 123
Views: 17044

Re: Reducing the effects of acceleration on the human body

In 1 g there is quite the pressure difference between fluid at the top or fluid 10 meters down (about 1 atmosphere). The perfect homogeneous body in the perfect fluid would indeed spread the acceleration around: It would replace it with a pressure gradient. That's how the fluid would get accelerated...
by Certhas
Sun May 23, 2010 6:35 pm UTC
Forum: Books
Topic: I need a book recommendation (Renamed : Recom'd me a book)
Replies: 340
Views: 211186

Re: Hard Science Fiction Novels that XKCD approves of.

Zohar wrote:You could try Greg Egan's stuff. Diaspora is pretty cool, as is Permutation City (both of which are sort of computer science fiction).


Computer science fiction? A good part of Diaspora is basically theoretical physics porn. :D So I second Egan.
by Certhas
Sun May 02, 2010 10:43 pm UTC
Forum: General
Topic: Why isn't buying food online popular?
Replies: 17
Views: 2043

Re: Why isn't buying food online popular?

I do my normal big food shop online. I'm a student, don't have a car and the only way to the supermarket from my house is two buses or a very long walk. It's cheaper for me and my housemates to club together and get a big order every so often then it is to get the bus. Instead, the Tesco van pulls ...
by Certhas
Fri Apr 30, 2010 12:20 am UTC
Forum: Serious Business
Topic: Women in Academia
Replies: 49
Views: 10060

Re: Women in Academia

When people talk about welfare capitalism like it's communism, they're wrong. But Krugman is mostly knocking down a straw man. Per capita GDP growth in Europe and the US since the 80s was almost identical. Furthermore if this is a straw man this strawman has shown its face several times in this thr...
by Certhas
Thu Apr 29, 2010 10:16 pm UTC
Forum: Serious Business
Topic: Women in Academia
Replies: 49
Views: 10060

Re: Women in Academia

Those things don't directly equate to taking months off of work at a time, in fact none of them are even close to that. The only thing that's anywhere near close is the 2 weeks of vacation that is mandated. And that's 2 weeks out of 52. Not 12 or 24 weeks! What you are suggesting will necessarily r...
by Certhas
Thu Apr 29, 2010 4:08 pm UTC
Forum: Serious Business
Topic: Women in Academia
Replies: 49
Views: 10060

Re: Women in Academia

I love it how many people INSIST that companies just can't operate under rules that are normal in many countries. :lol: I like what we have in Germany now, parents get paid time out to care for the kids in the first year, this can be split anyway they want between father and mother but if both take ...
by Certhas
Thu Apr 29, 2010 4:03 pm UTC
Forum: Serious Business
Topic: Women in Academia
Replies: 49
Views: 10060

Re: Women in Academia

I love it how many people INSIST that companies just can't operate under rules that are normal in many countries. :lol: I like what we have in Germany now, parents get paid time out to care for the kids in the first year, this can be split anyway they want between father and mother but if both take ...
by Certhas
Thu Mar 18, 2010 11:36 pm UTC
Forum: Mathematics
Topic: Famous Math Quotes!
Replies: 32
Views: 8018

Re: Famous Math Quotes!

"Wir müssen wissen — wir werden wissen!" - Hilbert "Read Euler, read Euler, he is the master of us all." - Laplace "Mathematics is the queen of sciences and number theory is the queen of mathematics." - Gauss And there is a great one which I believe to be due to Russell...
by Certhas
Fri Feb 26, 2010 2:05 pm UTC
Forum: Mathematics
Topic: Why are most mathematical constants so small?
Replies: 66
Views: 8349

Re: Why are most mathematical constants so small?

The value of c is based on experimental observation Sorry, I'm being imprecise here. The truth is that c is defined to be exactly equal to 299792458 m/s, and together with the definition of the second in terms of cesium this gives a definition of the meter. Which further proves the point people hav...
by Certhas
Mon Jan 04, 2010 1:42 pm UTC
Forum: Science
Topic: What's a log-meter?
Replies: 28
Views: 5113

Re: What's a log-meter?

I was always taught that with transcendental functions, the input had to be a unitless quantity, and that the output would also be unitless. With algebraic functions, you could sometimes make sense of the units, like with radicals and powers and multiplication and division... More specifically as u...
by Certhas
Thu Dec 31, 2009 3:18 pm UTC
Forum: Science
Topic: What's a log-meter?
Replies: 28
Views: 5113

Re: What's a log-meter?

That's a bit strict. In general in physics we would say that taking the log of a unit makes as much sense as adding different units together for the stated reason. So it's worthing thinking carefully why you wouldn't want to do that. I think if you look at it from the theoretical perspective it's mo...
by Certhas
Thu Dec 31, 2009 3:13 pm UTC
Forum: Mathematics
Topic: The ideal number.
Replies: 70
Views: 7988

Re: The ideal number.

4 = 2+2 = 2*2 = 2^2
by Certhas
Mon Dec 14, 2009 4:48 pm UTC
Forum: Mathematics
Topic: Mathematicians and String Theory/M-Theory
Replies: 6
Views: 1801

Re: Mathematicians and String Theory/M-Theory

To be a bit more precise, theoretical physicists seem to have a different approach to maths than many mathematicians. This is not so much applied but more heuristic maybe. The fact that we use advanced maths in TP means we can actually communicate with advanced maths people. There isn't really any o...
by Certhas
Sat Dec 12, 2009 3:47 pm UTC
Forum: Science
Topic: Why do we torture ourselves with Minkowski metric?
Replies: 36
Views: 5918

Re: Why do we torture ourselves with Minkowski metric?

I think the trend goes towards -+++ overall. An important reason is the popularity of extra dimensions. if you add extra dimensions in +--- the determinant changes sign.
by Certhas
Thu Dec 10, 2009 12:59 pm UTC
Forum: General
Topic: What music does God like?
Replies: 41
Views: 3479

Re: What music does God like?

Bach. Obviously.
by Certhas
Tue Dec 08, 2009 1:05 pm UTC
Forum: Science
Topic: Why do we torture ourselves with Minkowski metric?
Replies: 36
Views: 5918

Re: Why do we torture ourselves with Minkowski metric?

It's equivalent, but you are cheating yourself. All you have done is broken up a -1 in the metric into a factor in the components. You are not really using imaginary time, as you can see by the fact that mixing time and space components does not give you a complex number. In particular you are not r...
by Certhas
Sun Dec 06, 2009 9:39 pm UTC
Forum: Mathematics
Topic: Putnam
Replies: 33
Views: 3002

Re: Putnam

mike-l wrote:
stephentyrone wrote:t0rajir0u is a sharp guy. 7 is still pretty good.


Clearly.. I thought for sure t0rajir0u was at least a grad student :)



Say that again. At least! And i am a grad student in Maths. :D
by Certhas
Sat Nov 14, 2009 6:14 pm UTC
Forum: General
Topic: Google Wave
Replies: 190
Views: 20806

Re: Google Wave

Walter.Horvath wrote:Uhm, yeah. I wouldn't recommend not adding parameters to that. Wow.


Thanks for the invite! As soon as I accepted it I noticed I had received an original google invite, so now I can spread the love around, anybody still without?
by Certhas
Thu Nov 12, 2009 6:07 pm UTC
Forum: General
Topic: Google Wave
Replies: 190
Views: 20806

Re: Google Wave

Greenie wrote:is that the actual gmail address? I have invites


Ah damn, I missed that. No it's <My xkcd username> @gmail.com
by Certhas
Tue Nov 03, 2009 9:45 pm UTC
Forum: General
Topic: Google Wave
Replies: 190
Views: 20806

Re: Google Wave

If someone has some spare invites I'd love to join the hype ehhh... have a look as well I mean. :) Username@gmail.com
by Certhas
Tue Nov 03, 2009 2:30 am UTC
Forum: Mathematics
Topic: Is Pi Infinitely Long?
Replies: 57
Views: 5689

Re: Is Pi Infinitely Long?

Him: "Okay lets just say you have a circle with a radius of 0.5, then the circumference of that circle is Pi, as 2 * Pi * r = 2 * Pi * 0.5 = Pi , right? So then if the circumference of that circle is Pi then if you lay that out as a straight line then you have a straight line of Pi. So technic...
by Certhas
Tue Nov 03, 2009 2:23 am UTC
Forum: Mathematics
Topic: Is Pi Infinitely Long?
Replies: 57
Views: 5689

Re: Is Pi Infinitely Long?

Another sense in which 10 + 100 + 1000 + ... = -10/9 is a perfectly legitimate statement is that the function f(x) = \sum_{n \ge 1} x^n has an analytic continuation to the entire complex plane minus 1 . Which, BTW, is maths that is heavily used in physics to describe real systems measured i...
by Certhas
Tue Nov 03, 2009 2:04 am UTC
Forum: Serious Business
Topic: Branched: Dawkins, God, Morals and Rationality.
Replies: 51
Views: 4697

Branched: Dawkins, God, Morals and Rationality.

Continued from here : Also, Dawkins dismissal of religion outside of his area of expertise is unnecessarily confrontational and naive/stupid/counterproductive/ill informed. Most importantly it is anti-rational. To me atheism is a moral choice, not a rational one. Now a far more important moral choic...
by Certhas
Tue Oct 20, 2009 7:08 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0647: "Scary"
Replies: 271
Views: 58051

Re: Can someone please explain this comic

There was a similar theme in: http://xkcd.com/566/
by Certhas
Sat Oct 17, 2009 4:20 pm UTC
Forum: Mathematics
Topic: Cambridge Mathematical Tripos Part III
Replies: 3
Views: 3437

Re: Cambridge Mathematical Tripos Part III

I know many people who went there, not sure if its worth going. You get to do loads of calculations and no time to absorb and really think through the concepts. It is prestigious though and if you do well will get you a good PhD position. Just be sure it's really what you're after.
by Certhas
Thu Oct 15, 2009 2:19 pm UTC
Forum: Mathematics
Topic: Becoming a Mathematician?
Replies: 17
Views: 4676

Re: Becoming a Mathematician?

Depends. Theoretical physics? Almost all of it. My PhD is in Maths, but in many other countries I would be doing the very same thing I'm doing now in the physics department. For experimental physics I don't really know.
by Certhas
Mon Oct 12, 2009 8:46 pm UTC
Forum: Mathematics
Topic: Becoming a Mathematician?
Replies: 17
Views: 4676

Re: Becoming a Mathematician?

Actually the stats I hear frequently for all of academia are that 1 in 3 or 1 in 4 people who seriously pursue an academic career end up in a permanent position. It's probably slightly better in Maths as the exit options are sweeter than in, say, critical theory. That still means it's a huge risk an...
by Certhas
Sat Oct 10, 2009 11:02 am UTC
Forum: Mathematics
Topic: Becoming a Mathematician?
Replies: 17
Views: 4676

Re: Becoming a Mathematician?

I agree with skeptical. I started in physics and moved to borderline maths/physics because that was the physics that interested me most. Now I'm writing "physics" papers which go Theorem Lemma Lemma QED. In any case your reasons are definitely the right ones, but don't give up on physics i...

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