Solar sails have been proposed as a means of propulsion for interstellar exploration. While acceleration would be very slow, top speed would be much more than that attainable from chemical propulsion. Maybe...
Will they work? Well, for the reasons stated above, certainly not like Count Dooku's sail (scroll most of the way down). But some contend that sails will not work at all. The disagreement is over what principles are in play. In theory, light photons (which are not matter, but do have momentum) would bombard the sail, and push it away from the light source (conservation of momentum). The sail would have a mirrored surface to reflect the light, and thus keep the sail from heating. This lack of heating is the very reason the nay-sayers believe the sail will not work. Since energy cannot be created or destroyed, if the sail doesn't heat, it doesn't move. If the sail does heat, it does move, until the temperature of the object reaches equilibrium with the radiation. The proponents of the sail say that thermodynamics are not involved, and that the sail depends in whole upon the conservation of momentum. But does conservation of momentum apply to light, or only to matter?
The answer seems easy enough to my unschooled mind. If the sail depends on conservation of momentum, momentum would have to be transfered from the light photons to the sail. Correct? If this is the case, the light photons would slow after reflecting off of the mirror. Is this the case? (Anyone, anyone?) I know that light appears to slow when passing through a prism, but then upon exiting returns to it's normal speed. Apparently this is not an actual slowing of light.
We will find out the true answer soon enough. A civilian team hopes to launch a solar sail for testing by the end of October. In the meantime, if anyone with a better background in physics than I can answer my question about light slowing after being reflected please do so.
8.07.2003
8.06.2003
Run away! Run Away!
While in Des Moines, we saw Lara Croft Tomb Raider: The Cradle of Life. This is the worst movie I have seen since The Lucifer Complex. The acting is horrible, the effects are mediocre, and the editing is atrocious. That is all I have to say about that.
While in Des Moines, we saw Lara Croft Tomb Raider: The Cradle of Life. This is the worst movie I have seen since The Lucifer Complex. The acting is horrible, the effects are mediocre, and the editing is atrocious. That is all I have to say about that.
The Trip
Well, for those of you who were unaware (of my regular readers, I believe this constitutes one person) I spent most of last week in the saddle. Between early Tuesday afternoon when I rolled out of my driveway, and Saturday night when I kicked the sidestand down, marking the end of the trip, I put 1250 miles on my motorcycle. 480 of those on Saturday alone.
This was much like a trip from last summer, except Krista stayed home this time. From Minneapolis I headed to Hastings, and hopped over to the Wisconsin side of the Mighty Mississippi. I followed state highway 35 south along the river to Prairie Du Chien. 35 is a great motorcycle (or car for that matter) highway, with lots of hills and twisties, and many great views. My brother met me there Tuesday night.
Wednesday morning we crossed into Iowa. No matter what you think or have heard about Iowa, the north-east corner is beautiful. We hugged the river southward for a bit, passing though Guttenberg (pronounced by the locals as Gut-en-brg) down to Luxemburg. We turned west on highway 3. Still lots of hills and curves. About this time my brother experienced what is known as a tank-slapper. He apparently was trying to adjust his jacket, with both hands. He just happened to pick the spot where the road turned suddenly rough. His handlebars started flailing violently back-and-forth. Fortunately the laws of physics allowed him to stay vertical long enough to regain control. Perhaps he will relate a bit of what is was like in the comments. Hint, Hint.
After he started his heart pumping again, we hit the road. We stopped in Waverly (home of our alma mater) for sandwiches at The Other Place, and had a look around campus. I ran into my old advisor and mentor, and we had a good long talk about the state of television news. After a couple of hours in Waverly, it was time to motor on to Des Moines.
We snaked our way through the corn fields toward Marshalltown, where we would have the promise of a straight shot of four-lane the rest of the way to the 'rents. But it wasn't that simple. Just north of Marshalltown, I noticed that things looked a bit hazy up ahead. It had been overcast all day, and I quickly realized that it was raining up ahead. We pulled onto the shoulder, I jumped off and was getting my packable rain jacket out of my bag when I felt the first drops. By the time I had unpacked the jacket from it's pocket, I was drenched. With no shelter in sight, we continued on through the rain. The rain didn't last too long, and we were mostly dry by the time we reached Des Moines.
We did some riding over the next few days with our Dad, who just this summer bought a new bike. Our Mom and sister also tagged along for some of the riding. There are actually some decent motorcycling roads around Des Moines, particularly around Sailorville Lake.
Saturday it was time to head home. Dad tagged along most of the way to Waterloo. We followed generally the same route that we used on the way down, but we used highway 20, rather than highway 3, to cut down on travel time.
Back in Prairie Du Chien, my brother headed off to Madison, and I continued back to Minneapolis. At Lake Pepin, I could see rain on the Minnesota side, but soon lost sight of it as the road moved away from the river and the trees blocked my view. Rounding a corner, I could see the tell-tale haze up ahead, but was able to stop and throw on the rain jacket in time. The rain was short lived, but the road was wet for quite a while, so my shins got a good soaking.
The road between Hagar City (not really a city, more a group of houses) and Prescott is really, really nice. It has the best hills and the highest concentration of squiggly road signs of the whole trip. Unfortunately the opportunities for passing are almost nil. I found myself stuck behind a train of four cars for this entire stretch of tarmac. The leader of this hellish caravan found a top speed of 45 to be prudent, 30-35 where the squiggly signs suggested 45. 65 would have been my speed of choice, even in the curves, as the road is nice and smooth, and lines of sight are good. So I spent most of the last hour and a half of the trip singing songs of the lead car's horrible end.
All in all it was a fun trip. Next time I am pretty sure I am going to need an iPod for some tunes...
Well, for those of you who were unaware (of my regular readers, I believe this constitutes one person) I spent most of last week in the saddle. Between early Tuesday afternoon when I rolled out of my driveway, and Saturday night when I kicked the sidestand down, marking the end of the trip, I put 1250 miles on my motorcycle. 480 of those on Saturday alone.
This was much like a trip from last summer, except Krista stayed home this time. From Minneapolis I headed to Hastings, and hopped over to the Wisconsin side of the Mighty Mississippi. I followed state highway 35 south along the river to Prairie Du Chien. 35 is a great motorcycle (or car for that matter) highway, with lots of hills and twisties, and many great views. My brother met me there Tuesday night.
Wednesday morning we crossed into Iowa. No matter what you think or have heard about Iowa, the north-east corner is beautiful. We hugged the river southward for a bit, passing though Guttenberg (pronounced by the locals as Gut-en-brg) down to Luxemburg. We turned west on highway 3. Still lots of hills and curves. About this time my brother experienced what is known as a tank-slapper. He apparently was trying to adjust his jacket, with both hands. He just happened to pick the spot where the road turned suddenly rough. His handlebars started flailing violently back-and-forth. Fortunately the laws of physics allowed him to stay vertical long enough to regain control. Perhaps he will relate a bit of what is was like in the comments. Hint, Hint.
After he started his heart pumping again, we hit the road. We stopped in Waverly (home of our alma mater) for sandwiches at The Other Place, and had a look around campus. I ran into my old advisor and mentor, and we had a good long talk about the state of television news. After a couple of hours in Waverly, it was time to motor on to Des Moines.
We snaked our way through the corn fields toward Marshalltown, where we would have the promise of a straight shot of four-lane the rest of the way to the 'rents. But it wasn't that simple. Just north of Marshalltown, I noticed that things looked a bit hazy up ahead. It had been overcast all day, and I quickly realized that it was raining up ahead. We pulled onto the shoulder, I jumped off and was getting my packable rain jacket out of my bag when I felt the first drops. By the time I had unpacked the jacket from it's pocket, I was drenched. With no shelter in sight, we continued on through the rain. The rain didn't last too long, and we were mostly dry by the time we reached Des Moines.
We did some riding over the next few days with our Dad, who just this summer bought a new bike. Our Mom and sister also tagged along for some of the riding. There are actually some decent motorcycling roads around Des Moines, particularly around Sailorville Lake.
Saturday it was time to head home. Dad tagged along most of the way to Waterloo. We followed generally the same route that we used on the way down, but we used highway 20, rather than highway 3, to cut down on travel time.
Back in Prairie Du Chien, my brother headed off to Madison, and I continued back to Minneapolis. At Lake Pepin, I could see rain on the Minnesota side, but soon lost sight of it as the road moved away from the river and the trees blocked my view. Rounding a corner, I could see the tell-tale haze up ahead, but was able to stop and throw on the rain jacket in time. The rain was short lived, but the road was wet for quite a while, so my shins got a good soaking.
The road between Hagar City (not really a city, more a group of houses) and Prescott is really, really nice. It has the best hills and the highest concentration of squiggly road signs of the whole trip. Unfortunately the opportunities for passing are almost nil. I found myself stuck behind a train of four cars for this entire stretch of tarmac. The leader of this hellish caravan found a top speed of 45 to be prudent, 30-35 where the squiggly signs suggested 45. 65 would have been my speed of choice, even in the curves, as the road is nice and smooth, and lines of sight are good. So I spent most of the last hour and a half of the trip singing songs of the lead car's horrible end.
All in all it was a fun trip. Next time I am pretty sure I am going to need an iPod for some tunes...
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