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Message: <blockquote data-quote="mutantlast" data-source="post: 2941379" data-attributes="member: 115180">Presumably, Brian’s goal is to be able to travel nearly instantaneously between any two points in the galaxy. The problem is that there are physical laws we have to obey; we don’t have a choice. One of them is <a href="http://en.wikipedia.org/wiki/Special_relativity" target="_blank">special relativity</a>, which tells us that the maximum speed any object can move through space is c, or the speed of light in a vacuum, also known as 299,792,458 meters-per-second.  Furthermore, only things with zero mass can ever travel even that fast (and even then only in a <a href="http://en.wikipedia.org/wiki/Vacuum" target="_blank">vacuum</a>); everything with a mass always, by the laws of physics, has to travel slower than that.   <img src="http://startswithabang.com/wp-content/uploads/2008/02/batlight.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />First off, why is that the case?  The easiest explanation is that light always travels at the speed of light. Well, duh, you might say, that’s by its definition! But this is actually profound. What it means is that, no matter how quickly you move, light will always move relative to you at the same speed! Let’s say I shine a light at BatmanTM, and Batman and I are both standing still.  We can both measure the speed of that light, and we’ll both get the same value: c. On the other hand, what if I move towards Batman? If it were anything other than light, like a baseball, a bullet, or an electron (even electrons have mass), Batman and I would measure different velocities. Here’s why; let’s say I throw a baseball at 100 mi/hr, and I run towards Batman at 20 mi/hr. I would measure the baseball to be moving at 100 mi/hr, but Batman would measure the baseball at 120 mi/hr.   <img src="http://startswithabang.com/wp-content/uploads/2008/02/slr.JPG" alt="" class="fr-fic fr-dii fr-draggable " style="" /> But this doesn’t happen the same way with light; regardless of how fast I’m moving or how fast Batman moves, we both always measure the light beam to be moving at the same speed, c, or 670,000,000 mi/hr. If I take something with a mass, like my baseball, into a rocket, and I fly at 400,000,000 mi/hr towards Batman and launch the baseball at 400,000,000 mi/hr, will he observe the baseball moving at 800,000,000 mi/hr? No.  Special Relativity tells us that <a href="http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html" target="_blank">velocities don’t work like that</a> close to the speed of light, and Batman would see the baseball actually moving at 580,000,000 mi/hr, or less than the speed of light in a vacuum.  Lots of funny things happen close to the speed of light, but this really boils down to three things:<ol> <li data-xf-list-type="ol"><a href="http://casa.colorado.edu/%7Eajsh/sr/time.html" target="_blank">Clocks run slower</a>.</li> <li data-xf-list-type="ol"><a href="http://www.glenbrook.k12.il.us/gbssci/Phys/mmedia/specrel/lc.html" target="_blank">Lengths contract</a>.</li> <li data-xf-list-type="ol"><a href="http://en.wikipedia.org/wiki/Relativistic_mass" target="_blank">Masses appear to increase</a>.</li> </ol><img src="http://startswithabang.com/wp-content/uploads/2008/02/relativisticcurve.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />This last one explains why something with a mass can never move faster than c. No matter how much energy I put into something with a mass, trying to accelerate it faster and faster, I wind up making it heavier close to the speed of light, making it harder to accelerate. It gets so hard as I approach the speed of light, that to actually reach c, anything with a mass requires an infinite amount of energy!  And that is why it’s impossible for anything with a mass to travel even as fast as the speed of light in a vacuum.</blockquote>

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