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	<title>Dear Science &#187; Space</title>
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	<description>Seattle's Only Scientist</description>
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		<title>The Apollo Guidance Computer</title>
		<link>http://dearscience.org/2009/07/20/the-apollo-guidance-computer/</link>
		<comments>http://dearscience.org/2009/07/20/the-apollo-guidance-computer/#comments</comments>
		<pubDate>Tue, 21 Jul 2009 02:08:12 +0000</pubDate>
		<dc:creator>Jonathan</dc:creator>
				<category><![CDATA[Space]]></category>

		<guid isPermaLink="false">http://dearscience.org/?p=872</guid>
		<description><![CDATA[Let&#8217;s say you&#8217;re a NASA engineer in the 1960s, wearing your snazzy black plastic glasses, thinking of landing a man on the Moon and returning him safely to the Earth. You start thinking navigation. Getting into the right orbits is going to take a fair bit of computation&#8211;plus some fine control of rocket engines and [...]]]></description>
			<content:encoded><![CDATA[<p>Let&#8217;s say you&#8217;re a NASA engineer in the 1960s, wearing your snazzy black plastic glasses, thinking of landing a man on the Moon and returning him safely to the Earth. You start thinking navigation. Getting into the right orbits is going to take a fair bit of computation&#8211;plus some fine control of rocket engines and navigation jets. Really, you&#8217;re going to need a computer.</p>
<p>But this is the 1960&#8242;s. Computers are HUGE. Yes, yes, transistors had been invented years before&#8211;and are now in wide use. So, at least we&#8217;re not talking vacuum tubes. Egads. Tubes! Building computers means wiring a whole bunch of these transistors together. With wire. In other words, the world&#8217;s finest computers look a bit like that box of Christmas lights you don&#8217;t want to think about in the basement: tangled, ugly, mean and prone to failure if jostled. Not exactly conducive to placement in a rocket.</p>
<p>No biggie, you think. You&#8217;ll just have the computer on Earth&#8211;nice solid earth&#8211;radioing back and forth to the sensors and engines in the rocket. You can even correct for the speed-of-light delays! Problem solved! Light up some Lucky Strikes and call it a day. </p>
<p>But then you think of the return burn. If the Apollo craft are going to get <em>out</em> of lunar orbit and return to Earth, they&#8217;re going to need to fire the rocket engine on the far side of the Moon&#8211;you know, where radio waves can&#8217;t reach. Crap. I guess you&#8217;ll have to figure out a way of wiring together all those (4000 or so, egads!) transistors in a way that is small, light and durable enough to survive being rocketed into space. Time to create the first integrated circuit computer&#8211;father of every damn computer most of us have used, ever.</p>
<p>Better <a href="http://ed-thelen.org/comp-hist/vs-mit-apollo-guidance.html">call MIT</a>.</p>
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		<title>Extraterrestrial Saltwater Ocean on Saturn Moon</title>
		<link>http://dearscience.org/2009/06/25/extraterrestrial-saltwater-ocean-on-saturn-moon/</link>
		<comments>http://dearscience.org/2009/06/25/extraterrestrial-saltwater-ocean-on-saturn-moon/#comments</comments>
		<pubDate>Thu, 25 Jun 2009 21:47:16 +0000</pubDate>
		<dc:creator>Jonathan Golob</dc:creator>
				<category><![CDATA[Featured Articles]]></category>
		<category><![CDATA[Space]]></category>

		<guid isPermaLink="false">http://dearscience.org/?p=867</guid>
		<description><![CDATA[Enceladus, a moon of Saturn, probably has a saltwater ocean under it&#8217;s surface, at least per an analysis of data from the Cassini probe. Take it away NASA and JPL: For the first time, scientists working on NASA&#8217;s Cassini mission have detected sodium salts in ice grains of Saturn&#8217;s outermost ring. Detecting salty ice indicates [...]]]></description>
			<content:encoded><![CDATA[<p>Enceladus, a moon of Saturn, probably has a saltwater ocean under it&#8217;s surface, at least per <a href="http://www.nature.com/nature/journal/v459/n7250/full/nature08046.html">an analysis of data</a> from the <a href="http://saturn.jpl.nasa.gov/index.cfm">Cassini probe</a>. Take it away <a href="http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20090624/">NASA and JPL</a>:</p>
<blockquote><p>For the first time, scientists working on NASA&#8217;s Cassini mission have detected sodium salts in ice grains of Saturn&#8217;s outermost ring. Detecting salty ice indicates that Saturn&#8217;s moon Enceladus, which primarily replenishes the ring with material from discharging jets, could harbor a reservoir of liquid water &#8212; perhaps an ocean &#8212; beneath its surface. </p></blockquote>
<p>Such an ocean would vastly increase the chance of life elsewhere in our solar system, beyond our own planet. </p>
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