Ming the Mechanic
The NewsLog of Flemming Funch

Saturday, May 26, 2007day link 

 Trackback spam
I finally figured out what had been overloaded my server here for weeks. I had previously noticed that an extraordinary amount of trackback spam is arriving all the time. I had turned off that option for my own blog here, so that trackback would receive a "not found" error. But it was sent by a PHP page, so the server still had to do a bit of processing, which was enough to slow everything down.

My own weblog here is getting 5-10 trackback requests per second, 24-7, all of which are nothing but spam.

I now set up a rewrite filter in Apache, which gives back a "refused" error. The same amount of trackbacks keep arriving, from some kind of botnet of 100s of computers, but this takes much less processor power, so it doesn't matter much.

Trackback used to be a neat feature, allowing weblogs to notify other weblogs that one links to them. But it has been totally useless for quite some time, with the ridiculous amount of phony spam trackbacks.
[ | 2007-05-26 01:52 | 4 comments | PermaLink ]  More >

 Reboot
picture Next week I'll be at Reboot in Copenhagen. The best tech conference I know, and, also since it is in the town I'm from, the one I'm most likely to go to. I go to very few conferences these days, but that's a fine reason for dropping by for a few days. Many great people on the list of participants and speakers, including quite a few coming from the States.
[ | 2007-05-26 02:01 | 16 comments | PermaLink ]  More >

 Mars cave
picture Closeup of one of several likely openings into recently dicovered underground caverns on Mars. This one is 100 meters wide.
At its highest resolution of 25 centimeters per pixel, the HiRISE camera can see the detailed shape of the slightly scalloped edge of a hole on the flank of Mars' Arsia Mons (left), but no amount of image enhancement (right) can bring out any further details inside the hole. That means that the walls of the cave are overhanging -- the cave is larger below the ground than the entrance we can see at the surface -- and that it is very deep. Mars' dusty atmosphere produces enough scattered light that "skylight" would illuminate the floor of a shallow cavern well enough for HiRISE to detect it.

The hope for the HiRISE images was that we could see some details from inside the hole. But as you can see by the highly stretched version at right, there is absolutely nothing visible inside that hole. It's black black black black black. HiRISE is a very sensitive instrument, and Mars' dusty atmosphere scatters quite a bit of light around, so there is certainly light entering that cave hole and bouncing around the interior. But it seems that the cave is so big and so deep that almost none of the light that enters the cave comes out. It's deep, and it's big; the hole that we see really is just a skylight on a big subterranean room. How big? We'll never know for sure without visiting it, but I expect that Cushing and his coauthors and the HiRISE team will be crunching the numbers on the illumination conditions and the sensitivity of the camera to put a lower limit on how deep that cave must be for HiRISE to be able to see nothing at all inside it.

Think about that. All these orbiters at Mars, and most of them are just seeing the surface and atmosphere. To be sure, there are two instruments up there -- MARSIS on Mars Express and SHARAD on Mars Reconnaissance Orbiter -- that are probing the shape of the subsurface with ground-penetrating radar. But neither of those instruments have the resolution necessary to tell us what the inside of this cave looks like. It might as well be in the greatest depths of space. Here there be dragons. What's down there? Are there stalactites and stalagmites and crystals, or is it just a vast open room or tunnel?
Yeah, might just be something boring, like a parking garage.
[ | 2007-05-26 02:26 | 36 comments | PermaLink ]  More >

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