Time travel. Is this paradoxical?

[Prozac the Robert]

Imagine I build a time machine. Its creation requires no handy hints from the future or anything like that. At this point I have a time machine but haven't ever used it.

Sometime later, I eat some chicken which has gone off and get a bit ill. I don't die. I do feel terrible though, so I decide to test the time machine out.

At 5 o'clock exactly I send back a holographic projection which says "Don't eat the chicken else you'll get a tummy ache!" to arive just seconds before point B. It also says "Send this message at exactly 5 o'clock this evening."

I recieve the message, don't get ill, quickly set my time machine to send the message at the correct time, and then go on with my life.

Is this a paradox, or is it logically reasonable?

[SirNitram]

I don't beleive so, as long as you make sure to send the message back after learning not to eat the chicken.

[Zero]

But what started the chain of causality if he sends the message back just because the message got sent back?

[Lord Zentei]

But what started the chain of causality if he sends the message back just because the message got sent back?

Indeed: that would be information appearing out of nowhere. Bad mojo, I suspect.

A "many worlds" multiverse would solve that: the message came from an alternate universe. Of course, there would always be some universes where you would end up with a tummy ache - that would be the ones that sent the warning to those where you did not.

[Cao Cao]

Or maybe it would end up as the universe conspiring against you rule, the warning fails to get to you in time or you inadvertantly eat the chicken anyway.

[Count Dooku]

I suspect that your former self and your current self would exist in parallel universes, if they exist; but there is absolutely no way to know for sure.

[Lord Woodlouse]

Imagine I build a time machine. Its creation requires no handy hints from the future or anything like that. At this point I have a time machine but haven't ever used it.

Sometime later, I eat some chicken which has gone off and get a bit ill. I don't die. I do feel terrible though, so I decide to test the time machine out.

At 5 o'clock exactly I send back a holographic projection which says "Don't eat the chicken else you'll get a tummy ache!" to arive just seconds before point B. It also says "Send this message at exactly 5 o'clock this evening."

I recieve the message, don't get ill, quickly set my time machine to send the message at the correct time, and then go on with my life.

Is this a paradox, or is it logically reasonable?

From my understanding it's not how things would happen (I'm reluctant to say paradox, because the nature of time is so unknown the very word only has meaning when we know the laws that govern time. It's a paradox for a heavy hammer to float upwards on Earth with no outside assistance because it violates our understanding of gravity).

From my understanding it would merely create an alternate branch of time where you don't get ill. You'd still remain ill yourself and your own personal history would still remain unchanged.

[Patrick Degan]

It is paradoxical from a linear-time perspective; all such time-engineering operations would be. However, cause still precedes effect. The message cannot exist unless somebody sends it first. And there is no guarantee that merely sending information into the past will affect the flow of events. The message could get scrambled or be merely ignored. If the message is received clearly, is listened to, and "alters" anything, it's because that's the way things happened to begin with.

[Sriad]

But what started the chain of causality if he sends the message back just because the message got sent back?

Indeed: that would be information appearing out of nowhere. Bad mojo, I suspect.

If he can send info back at all, then data out of apparent nowhere isn't a problem. Multi-universes aren't even needed, just a brief closed loop in this one's past.