Reminds me of a question I was asked a while back - what's the average time dilation of all mass/particles in the universe, due to the expansion rate of the universe - i.e how much younger is the universe now than it 'should be' if it was static?
(I had to think about that one!) I guess technically since time was created at T=0 then the answer is simply 'now'!? Mark -----Original Message----- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Rob Matson Sent: 26 August 2009 08:28 To: Mexicodoug; Meteorite-list@meteoritecentral.com Subject: [meteorite-list] Speed-of-light question Hi All, Doug was first with the correct answer: 1/sqrt(2) * speed of light or a little more than 70% of the speed of light. I figured it might come down to a race between Doug and Sterling. ;-) Here's an alternative way of looking at the problem which will give you the correct answer almost immediately. The trick is to assume that *ALL* objects travel at the same "velocity" in 4-dimensional space-time, and for convenience we'll call this velocity "c". For simplicity, assume linear motion along just one spatial axis -- let's just call it the X-axis and make it horizontal. Now add a perpendicular axis (traditionally the Y-axis) but instead we're going to call it the T-axis (the velocity component in the time-axis direction): ^ | | T | | +---------> X A vector representing the velocity of any object will have a length of c. Any object traveling at the speed of light (e.g. a photon) is represented by the vector of length c parallel to the X-axis; in other words, time stands still for this object. And any object at rest gets represented by a vector of length c parallel to the T-axis; all the "motion" is in the direction of time. For our problem, we're looking for the vector that has equal velocity components in both the X-axis and T-axis (X=T). Obviously this is a 45-degree angle clockwise from +T (or counterclockwise from +X). So the component of the 4-D velocity that is in the spatial direction is C*COS(45), while the component of the 4-D velocity that is in the time direction is C*SIN(45). Voila! When you accelerate from a stand-still, your 4D velocity vector rotates away from vertical and toward horizontal (by a miniscule amount). Using the simple system above, you can easily figure out the required velocity in order to cover 2 light-years distance in one year, 4 light-years in one year, etc. --Rob ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list CONFIDENTIALITY NOTICE: This email and any files transmitted with it are confidential. If you are not the intended recipient, please notify us. Email i...@ssl.gb.com. You should not copy or use this email or attachment(s) for any purpose nor disclose their contents to any other person. GENERAL STATEMENT: Southern Scientific Ltd's computer systems may be monitored and communications carried on them recorded, to secure the effective operation of the system and for other lawful purposes. Registered address Rectory Farm Rd, Sompting, Lancing, W Sussex BN15 0DP. Company No 1800317 ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
