Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
×
Image

PhD Candidate Talks About the Physics of Space Battles 361

darthvader100 writes "Gizmodo has run an article with some predictions on what future space battles will be like. The author brings up several theories on propulsion (and orbits), weapons (explosives, kinetic and laser), and design. Sounds like the ideal shape for spaceships will be spherical, like the one in the Hitchhiker's Guide movie."

Comment Re:This is NOT a battery, it's a RTG (Score 1) 444

If I could get my hands on say an ounce of Pu 238 I could build a RTG that would power my home, all my vehicles, and enable me to quit my job and live of the check my local electricity provider would have to pay me for the excess power I would generate. It would generate full power for ~ 87 years and not only wold I be using the greenest power available I would be providing a community service of disposing of a radioactive material.

OK, you must have a very efficient house. The specific heat output of Pu238 is about 0.5 Watts/gram, so an ounce puts out about 14 Watts. Given 10% RTG efficiency (which is much better than normal), I give you about 1.5 watts from this. Can you run your house on that?

Businesses

The "Dangers" of Free 242

With today's Free Summit broaching the subject of the "dangers" of free, TechDirt has an interesting perusal of why free often can't work without a good business model and why it often gets such a bad reputation. "I tend to wonder if this is really a case of free gone wrong or free done wrong. First, I'm always a bit skeptical of 'free' business models that rely on a 'free' scarcity (such as physical newspapers). While it can work in some cases, it's much more difficult. You're not leveraging an infinite good -- you're putting yourself in a big hole that you have to be able to climb out of. Second, in some ways the model that was set up was a static one where everyone focused on the 'free' part, and no one looked at leapfrogging the others by providing additional value where money could be made. The trick with free is you need to leverage the free part to increase the value of something that is scarce and that you control, which is not easily copied. [...] Still, it's an important point that bears repeating. Free, by itself, is meaningless. Free, with a bad business model, isn't helpful either. The real trick is figuring out how to properly combine free with a good business model, and then you can succeed."

Comment Re:Independent Verification (oops) (Score 1) 509

I think your sample is badly biased by ending on the 1,000,000th prime, since essentially all your primes are then those between 10,000,000 and 15,485,863 which is the last prime in the first million file.

It took me a while to notice this, too, since any sampling which doesn't sample exact decades is badly biased. By the time you get all the primes less than 1e9, the distribution is very flat. Here are the stats:

first digit histogram [6003531, 5837665, 5735086, 5661135, 5602768, 5556434, 5516130, 5481646, 5453140]
fractions:

0.118069263338
0.114807236968
0.112789853038
0.111335485585
0.110187602998
0.109276369051
0.108483724924
0.107805540623
0.107244923476

I am running through all the primes less that 1e11 right now, and will post that later.

Comment New marketing strategy (Score 3, Funny) 379

OK, this is an interesting new marketing strategy for a company as a way to remove a product from their line. You don't ever have to stop selling it. You just keep halving its size until no one is sure whether they have bought one or not.

With some good access to the RDF, everyone will continue to hear music, whether or not there was actually a device in the box.

I still own a first generation Shuffle. I think it weighs 50 grams. Really, that's just to much to bear, carrying it in my briefcase. I know that if my briefcase only had a 10.7 gram Shuffle in it, it would be MUCH easier on my walk to work.

Slashdot Top Deals

There are two ways to write error-free programs; only the third one works.

Working...