June 04, 2008 at 03:57 AM · Posted under Stuff
Today has been a fun day. I’ve been blowing things up. Liquid nitrogen in soda bottles under buckets, there’s a video on YouTube.
A small amount (about a cup) of liquid nitrogen poured into a 2 liter soda bottle. The bottle was then capped, placed in a can with a little water on the bottom, and covered with a bucket. 21.9 seconds later (the counter in the video counts by frames, 9 frames is 0.3 seconds) the expanding liquid nitrogen exploded the bottle and broke the bucket, sending it flying. The bucket went about 25-30 feet up, but that is a very rough guess. Liquid Nitrogen is slightly colder than -196°C/-321°F, which is really cold. When liquid nitrogen becomes a gas it takes up about 700 times more volume. This intense expansion is what enables it to explode the soda bottle.
Very cool!
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April 30, 2008 at 05:50 AM · Posted under Stuff
Thermite is a mixture of iron oxide and aluminum. It burns at about 2,500 degrees celsius, that’s really hot. I’m not sure how the chemistry of it works but when a lot of heat is added to thermite it reacts violently. It needs more heat than a match, something like a blow torch or burning piece of magnesium. The resulting reaction is really really cool. My dad filmed we made.
I bought the ingredients at a place called Alpha Chemicals for far cheaper than pre-mixed thermite would have cost. It is honestly one of the coolest things I have ever seen.
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April 21, 2008 at 02:19 AM · Posted under Internet
A while back I wrote a bash script to download all episodes of Security Now. In the latest episode the topic of downloading the back catalogue of episodes came up so I though I’d update my script.
This bash script will download all episodes of Security Now and dynamically pull the name of each episode and apply it to the file name. I’m quite happy with it.
#!/bin/bash
curl -o /tmp/snd-download http://twit.tv/sn
grep -e 'class="podcast-number current">[0-9]*</a>' -o /tmp/snd-download > /tmp/snd-work1
grep -e '[0-9][0-9][0-9]' -o /tmp/snd-work1 > /tmp/snd-work2
counter=`cat /tmp/snd-work2`
rm /tmp/snd-download
rm /tmp/snd-work1
rm /tmp/snd-work2
while [ $counter != 0 ]
do
curl -o /tmp/snd-download http://twit.tv/sn${counter}
grep 'class="podcast-number current"' /tmp/snd-download > /tmp/snd-work1
grep -e 'Security Now[^"]*' -o /tmp/snd-work1 > /tmp/snd-work2
sed -e "s/:/ -/" /tmp/snd-work2 > /tmp/snd-work3
title=`cat /tmp/snd-work3`
rm /tmp/snd-download
rm /tmp/snd-work1
rm /tmp/snd-work2
rm /tmp/snd-work3
clear
echo Downloading ${title}
if [ $counter -lt 10 ]
then
curl http://aolradio.podcast.aol.com/sn/SN-00${counter}.mp3 -o "${title}.mp3"
else
if [ $counter -lt 100 ]
then
curl http://aolradio.podcast.aol.com/sn/SN-0${counter}.mp3 -o "${title}.mp3"
else
if [ $counter -lt 1000 ]
then
curl http://aolradio.podcast.aol.com/sn/SN-${counter}.mp3 -o "${title}.mp3"
fi
fi
fi
counter=`expr $counter - 1`
done
To run the script place it in the folder you want to save the episodes to. In your command line give the file executable permissions, chmod 777 script, then run it, ./script. It will dump the episodes in the same folder the script is in.
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