Time Machines

John Clark (jonkc@worldnet.att.net)
Sun, 22 Aug 1999 11:04:31 -0400

Hash: SHA1

In looking over the Extropian archives I noticed that the subject of time machines and faster than light travel came up on the list about a year and a half ago, I didn't have time to enter into the discussion then but I do now so I just used my Tachyon modem to send a message to the list for December 17 1997, just for the hell of it I decided to cc a copy to the list for August 22 1999 too.

Relativity does not forbid anything from moving faster than light, only stuff that has mass or energy or carries information. Strangely some things have none of these attributes, although calling them "things" may be stretching a point. It's been proven experimentally that some quantum effects propagate much faster than light, probably instantly, and for unlimited distances. One system can influence another system on the other side of the universe with little or no delay, but it carries no information because the receiving system just changes from one apparently random mode to another, it's only when you compare the two systems (and that can only be done at light speed or less) does the correspondence between the two systems become obvious. The 2 random modes have equal energy so energy is not transferred either.

A less spooky example could be found in the idea of Phase Speed. I'm standing in the center of a huge hollow sphere 2 light years in diameter, I've been there for a long time and I'm holding a powerful LASER that makes a spot of light on the distant wall of the sphere one light year away. Suddenly, still holding the LASER and in the space of one second I make a complete 360 degree turn. Exactly 2 years later an observer standing at the same place would see the spot move much faster than light, it would travel the entire circumference of the sphere, 2PI or 6.28 light years in only one second. No photon moved faster than light however, and no energy or information between any two points traveled faster than light. A photon of light moves at light speed and carries energy and information, a spot of light can move at any speed but carries neither energy nor information.

And then there are Tachyons. Actually relativity does not forbid matter moving faster than light, it forbids matter moving AT the speed of light. That's almost the same thing but not quite. Perhaps a particle could somehow tunnel past the speed of light or maybe Tachyons have always moved faster than light from the first instant of The Big Bang.

People have looked for Tachyons but have never found the slightest evidence that they exist in nature, much to the relief of physicists. Tachyons are an embarrassment, the faster they move less energy they have, one that moved just a little faster than light would have a lot of energy, one that moved at an infinite velocity would have zero energy. Much worse, Tachyons move backward in time, they arrive at their destination before they start. You could communicate with the past.

Even though they have never been detected and the laws of physics do not demand that Tachyons exist, they don't seem to forbid them either. Most think nature is totalitarian, if it's not forbidden then it's mandatory.

What about the logical paradoxes that would result from communicating with the past, wouldn't that be enough to rule out Tachyons? It would if anybody saw them, but suppose nature rubbed out any witnesses to her crime and brought a universe to an end that was about to see a paradox.

Damn, I just knocked my coffee cup off the table, what a mess! I'm really not in the mood to clean it up, instead I'll use my Gateway 14,400 Tachyon modem and send myself some E mail 2 minutes ago. I'll just hit the send key and

.....brought a universe to an end that was about to see a paradox. Pardon me, I just got some E mail from John, let's see what it says " Dear John: Be careful with that coffee cup near your elbow, you're about to knock it over." Wow, John is right, that cup is dangerously near the edge, I'll put it in a safe place. It was nice of John to warn me about it, it's too bad that means oblivion for him and his entire universe but that's life, nature just will not allow anybody to observe a paradox.

I know what you're thinking, how could John be so stupid, he must be completely out of his mind, why else would he deliberately buy an obsolete 14,400 Tachyon modem? Well, call me cheap if you want but I still think the 28,800 model is too expensive, besides I have it on very good authority that Gateway will drop the price next year.

John K Clark jonkc@att.net

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