I read a book by Isaac Asimov called "Nemesis" and he had quite an interesting theory regarding the possibility of superluminal speeds. Basically he proposed that the speed of light is actually zero, relative to us. He also said that if this were true, it would mean that mathematically, everything that we know would be moving at a negative speed/velocity, and everything moving faster then light (Tachyons) would have a positive speed/velocity.

 

Before I go any further, let me just say that I am in no way, shape, or form convinced that Asimov is correct about any of this.

 

Now since Tachyons are predicted to travel at speed infinity when no energy is added to them, would that mean that ordinary particles would be moving at speed negative infinity if we consider the speed of light as zero?

This looks to me to be just a coordinate settup, it doesn't change the physics.

I dunno what Asimov said, but it strongly sounds like the pseudo-norm for vectors - 4-velocity in this case. With the signature of the metric tensor chosen to (-1,+1,+1,+1), this value would be =0 for lightspeed, <0 for velocities below lightspeed and >0 for velocities faster than the speed of light. The 4-velocities only give directions (note that a direction in 4D has the same amount of degrees of freedom as a vector in 3D) and are usually normalized to -1 and +1, respectively (except where the value was 0 in the first place, you cannot normalize that to anything else).

 

Note: In the signature-choice that appears more common to me, namely (+1,-1,-1,-1), the signs are inverted, so don't run around telling people that all sub-lightspeed velocities are negative (not a good idea anyways, unless you can answer the follow-up question "what does that mean?").

Would things traveling at "positive" speed have negative mass, if things traveling at negative speed have positive mass?

Would things traveling at "positive" speed have negative mass, if things traveling at negative speed have positive mass?

 

If they where going faster than the speed of light, then it'd be exactly the same as if you defined the speed of light to be 3*10^8m/s and obay the same superliminal ideas that people throw about. Which IIRC have no evidence for them atm...