<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";
color:black;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0in;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";
color:black;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:"Consolas","serif";
color:black;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Arial","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";color:#1F497D'>If there is no time, then light has no speed, so we can move at will throughout the universe (to any position), unless we get sucked into a black hole.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><a name="_MailEndCompose"><span style='font-size:11.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></a></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> extropy-chat-bounces@lists.extropy.org [mailto:extropy-chat-bounces@lists.extropy.org] <b>On Behalf Of </b>Anders Sandberg<br><b>Sent:</b> Thursday, August 22, 2013 4:29 PM<br><b>To:</b> extropy-chat@lists.extropy.org<br><b>Subject:</b> Re: [ExI] speed of light at the speed of light<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>On 22/08/2013 20:58, John Clark wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal>On Thu, Aug 22, 2013 at 7:29 AM, Gordon <<a href="mailto:gts_2000@yahoo.com" target="_blank">gts_2000@yahoo.com</a>> wrote:<o:p></o:p></p><div><div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><p class=MsoNormal><o:p> </o:p></p><div><div><div><p class=MsoNormal>> I am in a spaceship accelerating away from earth and approaching the speed of light. I have a flashlight. My instruments tell me that the light emitted from my flashlight travels at c. This is true no matter whether I shine it forward in the direction of my travel or backward toward the rear of the ship. <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:9.5pt'>I am accelerating away from earth such that my ship's velocity relative to earth compared to c is halved in each time period. For example at time t, my ship is travelling at 90% of c. At t2, my ship is travelling at 95% of c. At t3, my ship is travelling at 97.5% of c, and so on for an infinite amount of time as I approach c.<o:p></o:p></span></p></div></div></div></blockquote><div><p class=MsoNormal><span style='font-size:9.5pt'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:9.5pt'>It's OK for thought experiments to be wildly impractical but they must be physically possible, and the above experiment would not only take an infinite amount of time to perform it would also take an infinite amount of energy.<o:p></o:p></span></p></div></div></div></div></blockquote><p class=MsoNormal><br>However, the conclusion about infinite time and energy are a *result* of doing the Einstein thought experiment properly. You cannot dismiss the lightspeed case straight away.<br><br>Einstein had a nifty way of showing that there is something problematic going on in this case, which I think was one of his primary reasons for developing the full theory: suppose you run past an electromagnetic wave while travelling at c. What do you see? It ought to be static in your reference frame, but in that case it breaks Maxwell's laws. So either electrodynamics is wrong, or the velocity addition formula is wrong (and we already have some suspicions since light seem to move at c regardless of speed). So let's see what happens if we assume the velocity addition formula has to be something else...<br><br><br><o:p></o:p></p><pre>-- <o:p></o:p></pre><pre>Anders Sandberg,<o:p></o:p></pre><pre>Future of Humanity Institute <o:p></o:p></pre><pre>Oxford Martin School <o:p></o:p></pre><pre>Faculty of Philosophy <o:p></o:p></pre><pre>Oxford University <o:p></o:p></pre><div class=MsoNormal align=center style='text-align:center'><hr size=1 width="100%" noshade style='color:#A0A0A0' align=center></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>No virus found in this message.<br>Checked by AVG - <a href="http://www.avg.com">www.avg.com</a><br>Version: 2013.0.3392 / Virus Database: 3211/6600 - Release Date: 08/22/13<o:p></o:p></p></div><hr noshade="noshade" size="1"><a></a><p class=""avgcert"" align="left" color="#000000">No virus found in this message.<br>
Checked by AVG - <a href='http://www.avg.com'>www.avg.com</a><br>
Version: 2013.0.3392 / Virus Database: 3211/6600 - Release Date: 08/22/13</p></body></html>