Time travel | Clipmarks


	Time travel

chetler

8-17-2009 9:45 AM

63 views

tags:

physics

chetler says:

we're not as free as we'd hope. Some interesting constraints.

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<div style="margin: 12px 0px; font-family: arial; color: #333333; background: #ffffff; border: solid 4px #e5e5e5; width: 100%; clear: left;"><div class="CM_CTB_Content_Wrap" style="margin: 0px; padding: 0px;background-color: #ffffff;"><div style="border-bottom: solid 1px #dcdcdc; white-space: nowrap; margin-bottom: 8px; background-color: #eeeeee ;background-image: url(http://clipmarks.com/images/source-bg.gif); background-repeat: repeat-x; height: 24px; line-height: 24px; vertical-align: middle; padding-bottom: 4px; color: #666666; font-size: 10px;" ><a href="http://clipmarks.com/clip-to-blog/" title="see clips that are hot right now"><img src="http://content.clipmarks.com/blog_embed/b1a372c3-b8a8-4736-8a47-a496188ee8d0/DBBC1D37-0B47-4510-84EE-568F5A1BAAD1/" alt="" width="19" height="19" border="0" style="vertical-align: middle; margin: 0px 4px; display: inline; border: none; float:none;" /></a>clipped from <a title="http://www.slate.com/id/2225223/pagenum/all/" href="http://www.slate.com/id/2225223/pagenum/all/" style="font-size: 11px;">www.slate.com</a></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.slate.com/id/2225223/pagenum/all/"><P> Imagine you shot a pool ball into a time machine and it emerged a moment before<EM> </EM>you made the shot. Now suppose that you aimed the shot just right, so the outgoing ball (your ball, a second earlier) would block the original shot and prevent it from going into the time machine.<A name="return"> </A>This paradox, proposed by Joe Polchinski, then at the University of Texas,<A href="#correction">*</A> turns out to be the same as the grandfather paradox, albeit with less profound implications.</P><P>Kip Thorne and his students worked out what looks like a compromise solution for the impossible pool shot. They argue that you'd line up your shot exactly, but as your ball headed toward the time machine, another one would fly out at a slight angle and graze its side. The first ball would still travel into the time machine but at a slightly different angle than you'd intended. Then it would come back out of the machine, a moment earlier, at the same barely skewed angle—and the <EM>Terminator</EM>-style loop would be complete. </P></blockquote></div><div style="margin: 0px 6px 6px 4px;"><table style="font-size: 11px;border-spacing: 0px;padding: 0px;" cellpadding="0" cellspacing="0" width="100%"><tr><td style="background:transparent;border-width:0px;padding:0px;">&nbsp;</td><td align="right" style="background:transparent;border-width:0px;padding:0px;width:107px" width="107"><a href="http://clipmarks.com/share/DBBC1D37-0B47-4510-84EE-568F5A1BAAD1/blog/" title="blog or email this clip"><img src="http://content7.clipmarks.com/images/c2b-foot.png" border="0" alt="blog it" width="107" height="17" style="border-width:0px;padding:0px;margin:0px;" /></a></td></tr></table></div></div>

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