Time Travel discovered

Agree speed or position (but not both WITH EXTREME PRECISION) at the same time

Cop can say "He was doing 100klm/hour exactly according to my radar" (close enough for the court) so let's take that as a given

Asked exactly where he was "Driving past that tree in the photo"

The more precise you make one measurement the less precise the other becomes

The mathematics at quantum level defeats me

I'm guessing it will involve Planck's length which I take to be the shortest physical length possible

How NOW (which I had noted and contend has no thickness - being only a concept between PAST and FUTURE) straddles the physical world is the puzzle

It just occurred to my 3 neuron brain - Planck's length shortest physical length possible, NOW a non physical concept (hence no physicality hence not real)

leaves me with PAST - non existent- FUTURE - non existent and now NOW not real

HELP

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Hi there Michael. "Now," exists more than ever in your example. Should I reverse time before moment B, I may see a certain event; should I reverse time AFTER moment B, the event may not occur, or may have changed. ☺ Good luck.

 

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From LaurieAGPost 12

Hawking never made such a silly claim.

I did not read all the Posts to this Thread & apologize if remarks similar to the above have been previously posted.

 

Time is a logical progression of humanity (both good and evil.)

 

Is that ... like ... a definiton of time?

What was time before humans evolved?

 

I'd still be human. I'd be as I am today.

 

What?

 

You cannot change the past, it has already happened. If I reversed time my life would be the same as it is.

 

My question involves how you define what time was before mankind came along to "progress" - either goodly or evilly.

Did the dinosaurs not see the Moon chase the Sun across the sky?

 

I would not become an animal if that's what you're asking.

 

Psssst, you are an animal.

 

Chess pigeon?

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I am not an animal, I'm human. Jimmy Saville was an animal. He attacked me when I was nine-years old. I would like to visit his grave but apparently they've moved it to a secret location. He's buried in concrete staring out to sea. B*st*rd!

 

Humans are animals. You're not a plant you're an animal.

Nobody liked Jimmy.

We all were attacked by Jimmy at one time or another.

That is because everyone would put graffiti on his head stone.

 

Not if they buried him with his bum sticking out the ground. That way people could gently place flowers. And I'd have somewhere to park my bicycle.

 

The SciFi version of Time Travel presents a lot of problems not usually addressed, although my my not infallible memory tells me that Asimov addressed some of the issues.

In almost all of the Scfi versions of time travel, there is not mention of requirements for spacial travel.

In SciFi time travel, a person who travels (for example) 10 years backward or forward in time, remains in his pre-travel position on Earth, with no mention of a requirement for traveling some distance in space.​

The Earth's 10-year change in position is not easy to determine. Aside from rotation around the sun, the galaxy has rotation and translation motion. I am not sure what other motions must be considered.

It is not clear what what coordinate system is applicable to this situation. ​

The space travel requirements might require traveling faster than light, which is not likely to be possible. ​

 

Indeed. Since our current understanding of nature is that there is no absolute, stationary rest frame, I find it very unlikely that any time travel device would be affixed to a given point in space at all.

In fact, let me generalize that idea:

Our "traditional" time travel device would have us move in only a single dimension (time), keeping the other three fixed.

Yet, we can't even do that with spatial dimensions.
I cannot decide to keep two of three spatial dimensions fixed and move only through the third. Sure I could move in a straight line and call that 'dimension Z', but it's not. There's no fixed orientation of the dimensions. Any given movement is as easily considered moving equally in all tree spatial dimensions, just by arbitrarily redefining the axes.

This strongly suggests to me that any form of time travel will involve all four dimensions simultaneously. All we're really doing is trading off displacement in one dimension with displacement in another dimension.
I can trade off some displacement in X for more displacement in Z (again, even though they are arbitrary). The only way I'll be able to change my displacement through T is if I trade off some displacement in X,Y and/or Z.

And the only way we know of to make that trade is by approaching the speed of light or getting close to a massive object (both, forms of acceleration).

 

"I'm Brian and so's my wife."-A Jew, The Life of Brian.

 

The location considerations become applicable to the magical teleportations or "leaps" over decades, centuries, and millennia that occur in the least "hard-science" speculative fiction tales. Kind of like the time-travel version of hyperspace jumps that provide a gimmick for crossing light-years quickly in space opera stories and shows.

Otherwise (and this potentially involving thaumaturgical powers as well), the "chrono-naut" adventurer would have to pass through all the distinct, incremental changes in the "past direction" just as s/he already passes through all the moments of the "future direction". With regard to the latter, we certainly don't worry about planet Earth suddenly disappearing under our feet and finding ourselves in the middle of empty interstellar space, either. If time-traveling to the future via relativistic speeds, you'd need to be aboard a spaceship or something, which would entail departing the Earth, anyway (in the classic scenarios).

Regarding the "loops" as sported in genre fare like Primer, there is the tedious progress/regress through the incremental durations, even if following a curve back to a certain point or where one started. Not the "temporal teleportation" stuff.

~