Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?

Slashdot videos: Now with more Slashdot!

  • View

  • Discuss

  • Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).


Comment: Emperor! (Score 2) 191

by Geoffrey.landis (#49336063) Attached to: Your favorite Julian?

Emperor Julian the Apostate! (AD 332 - AD 363)
"He is clearly Rome's second ever philosopher-ruler, after the great Marcus Aurelius. But if Marcus Aurelius was weighed down by war and plague then, Julian's greatest burden was to be that he belonged to a different age. Trained classically, learned in Greek philosophy he would have made a fine successor to Marcus Aurelius. But those days had gone, now this distant intellect seemed out of place, at odds with many of his people, and certainly with the Christian elite of society. "

--nice bio by Gore Vidal, too.

Comment: Single crystal needed (Score 1) 56

by Geoffrey.landis (#49335263) Attached to: Stanford Breakthrough Could Make Better Chips Cheaper

...if they can deposit a layer of GaAs on top of the sacrificial layer and make circuits out of that, then why do they need the bottom wafer at all? Why not add the sacrificial layers on something less expensive and then deposit the GaAs circuit layer on top of that?

Because the chips need to be made on single-crystal material, which needs to be grown on a single crystal substrate.

This is, by the way, not particularly new in the solar cell research community. Photovoltaics researchers have been developing technologies like this for a long time-- it's called "epitaxial lift-off" or "monolithic metamorphic" in the most recent versions (with "metamorphic" indicating a change in lattice constant), but older variants were called "cleft" and "peeled film technology".

Comment: Correlation (Score 1) 283

"A key stumbling block in the effort to combat global warming has been the intimate link between greenhouse gas emissions and economic growth."

Time to cue up the warning about correlation not being causation.

Most particularly, in this case: when the economy gets better, people buy more stuff. There's a correlation between how many teddy bears people buy for their children and their income. That doesn't mean that increasing the production of teddy bears will increase average income. When the economy grows, people buy more.

Comment: Re:What exactly were the rules? (Score 1) 538

After some quick digging, this appears to be the law broken:

That link says nothing whatsoever about rules for government employee e-mail.

That's a link to rules about ISPs archiving e-mail that is the subject of a subpoena.

Comment: Re:What exactly were the rules? (Score 3, Informative) 538

So, I'd like to see the text of the "rule" saying she needed to use a .gov account before saying she broke the law. (People seem to be referring to the 2013 National Archives and Records Administration guidance as the "rules", but 2013 was after she left office.)

After some quick digging, this appears to be the law broken:

Basically, she was required by law to archive her communications on federal servers. She did not.

The link you give says nothing of the sort. The link states that a government may require an ISP to archive e-mail subject to a subpoena.

That has precisely nothing to do with State Department employees, nor does it say anything whatsoever about what e-mail addresses they use.

Also of note, according to TSG she forwarded classified intelligence Emails to Sidney Blumenthal, who was not a federal employee.

That is a great example of "ABCs"-- Argument By Changing the subject.

Comment: Effective killing nevertheless (Score 1) 247

Humans are the most deadly predators that the planet has ever had. Killing stuff is what we're really really good at. Making weapons is something we're really really good at.

Actually, making tools and organizing labor is we're really good at.

Exactly. And tools and organization are the two most useful skills... for efficiently killing things.

I personally have never killed anything larger than a bug in my life; I suspect a lot of other people haven't either. I've never had to, because there have always been other people who are willing to do those unpleasant tasks for me, in exchange for modest amounts of money.

Paying somebody else to do it turns out to be a very efficient strategy for killing.

Comment: Zombies versus Predators (Score 2) 247

Nevertheless, this is silly.

Humans are the most deadly predators that the planet has ever had. Killing stuff is what we're really really good at. Making weapons is something we're really really good at.

Zombies... their weapons are teeth and fingernails. Their tactics are go straight in and attack regardless of tactical situation.

They wouldn't have a chance.

Comment: You miss the center by how much? [Re:Kinda notnews (Score 2) 122

by Geoffrey.landis (#49094271) Attached to: The Science of a Bottomless Pit

OK I created the following Matlab code:


The plot isn't very impressive. It looks like a line straight through the center. The min radius is 114m so basically over 6500m drop the center moves about 114 m.

That doesn't seem right. You are doing the calculation in the rotating coordinate system of the Earth?

Equatorial rotational velocity of the Earth is 465 m/s. The center of the Earth is stationary in the rotating coordinate system, so over a 22 minute drop, the lateral displacement should be 614 kilometers. That's not the distance by which you miss the center, since as you deviate from the initial radial line the gravity vector changes direction, but the effect of that will be small until you get to distances that start to be comparable to 10% of the Earth's radius, so it should be close to the miss distance.

It's a non-Keplerian orbit (even in the non-rotating frame), so you don't come back to the same place you started.

Comment: Non Keplerian [Re:Kinda notnews] (Score 4, Informative) 122

by Geoffrey.landis (#49094197) Attached to: The Science of a Bottomless Pit

Mathematically it's an example of a degenerate orbit with one zero semi-axis, and the orbital period can be simply calculated from Kepler's laws.

No, it can't; it's not a Keplerian problem. You could calculate the period using Kepler's laws if the Earth were a point mass. But it's not. You could calculate the period using the Brachistochrone calculation if the Earth were a uniform sphere. But it's not. The Earth is layered, with the density changing as you go closer to the center. Only way to solve the problem correctly is numerical integration.

(I'd actually be interested in seeing the calculation done in the article.)

There is no distinction between any AI program and some existent game.