|MadSci Network: Physics|
I'm afraid I can't answer you question beyond an unsatisfactory "Maybe!". I can, however, comment on the foundations of your question. High energy physics can be tricky business because it's often counter intuitive and at odds with our own personal experiences. Let me attempt address each sentence in your question individually.
Someone traveling close to lightspeed ages slower than someone who is motionless.
This actually isn't necessarily true. More importantly, it depends on how that someone is traveling. Is he moving at a constant speed, or is he accelerating (and decelerating and turning around and accelerating again...)? This is the basis of a famous though experiment know as the Twin Paradox, and demonstrates the differences between Special Relativity and General Relativity. Special Relativity deals with inertial reference frames where two observers move with fixed speeds relative to each other. When this is the case, both observers can claim that they are motionless and that the other is moving. Because of this, both will think that the other is aging more slowly while they themselves age at a normal speed. Both are actually aging at the same rate (as measured by a neutral, third observer), they're simply disagreeing on how and when they make their measurements. General Relativity, on the other hand, deals with non-inertial reference frames where one observer is accelerating relative to another. When this is the case, both observers will agree that the accelerating person has aged slower than the stationary observer upon his return. The key is that one observer experienced extreme accelerations while the other did not.
Hypothetically if someone could travel at lightspeed they would be frozen in time.
Actually, that is going to depend on which person you ask. The person moving at lightspeed would go about his life normally (relatively speaking!) watching objects zip by at incredible speeds. He would consider himself stationary and think everything and everyone else was moving at lightspeed. He would therefore think that they were "frozen in time", not him. In actuality, both parties are aging normally when measured in their own reference frames.
So hypothetically if someone was made of tachyons would they age in reverse going from old age to fetus?
Here's where I apologetically offer my official answer of "Maybe!". It's hard to draw "real world" conclusions about tachyons since they live primarily in the theoretical, superluminal world. In fact, it's probably safest not to think of tachyons as physical particles but instead as instabilities in the particle theory which adhere to the underlying mathematics. Rather than offer an answer of my own, allow me list two interesting "features" of tachyons and allow you to reach your own conclusion:
I hope this has helped
James R Holliday
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