h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Going back to the time, speed, distance - simple physics mistake coming up here.

To be technically acurate, you go into vector territory:

Speed becomes velocity
Distance becomes displacement

so

Velocity = Displacement / Time

Therefore

Time = Displacement / Velocity

Both velocity and displacement can be negative.

All vectors have a direction and a magnitude, however time only has a magintude, so is a scalar, and can't be made negative

I've never studied very far in physics, so I'm not sure whether any argument I might offer would be valid.. However, in the spirit of Mission: Impossible, I'll try.


About velocity and displacement, I think that's basically what I was trying to say.

About time being scalar .... well, why does time have a magnitude? Admittedly it has a value ("now" being the only valid one as far as we know), but why a magnitude? (Please forgive my ignorance.)

-Euphoric One

Why am I wrong to talk of speed? i.e. lightspeed

I agree velocity and displacement can be negative, in a formula! If, say, you are talking about the length of time to travel between two absolute points.

If you regard velocity as a constant speed of an object in a constant direction (pleeeease don't go into angular velocity or acceleration), the amount of displacement (distance measured from a certain point) traveled is always a true distance, despite being a +/- displacement.

To explain, if I jumped a train, expecting to travel North, but I accidently jumped a train Southwards, I would be going at a negative velocity towards my target, but I am still travelling at a positive speed.

Scalar, yes!! So? But as you say, so is time.

Doesn't help us go "back in time" though, it seems to me that the thought of time travel is so enticing, it's a shame not to engage in the pleasures of ametuer dreaming.

Such as the fact that there is life on earth may be proof of time travel. Some bloke, curious to see what the earth was like before recognisable life, popped back, accidently dropped off a few bacteria (despite all time travel precations), which thrived in the planitary petri-dish environment from which all subsequent life evolves, making man his own creator etc. etc.

HB

On values and magintudes of time

saying now is a vaule of time is the same as saying here is a value of space/distance.

Now is a point of time. The time taken between then and now is a magitude / value.
---
Since the current theorys on time travel are based on movement of two bodies relative to each other (ie a guy in a rocket moving relative to the earth), we have to use velocity since speed will not tell us if they are moving relative to each other.

Back to the train

If I get a train from my current residence in Manchester to London, I will (in an ideal world) be travelling at 200 km/h. Say my friend was travelling from Manchester to Liverpool again at 200 km/h. All that comparing the speeds will do is say we are travelling the same speed. It is only by comparing velocities - 200 km/h South East V 200 km/h West that we can find we are travelling at a different velocities, and in the moments of accoration, we are time travelling relative to each other. (in a timed way, and it won't make the jorney seemany faster!)

Yeah but wasn't the relativity problem with velocity and light speed (seemingly so important with time travel), that light speed was always constant no matter how you measure it (directionwise).

In other words, light speed is as fast as you can go.

If I was in a train (most use they've been this year) going at half light speed on one track and you were in a train in the opposite direction going three quarters light speed. I could put a speed gun in my hand to try and measure your relative velocity towards me, (expecting to see your approach to be 1.25 * light speed), but wouldn't clock you faster than light speed.

Or am I drifting wider and wider from the mark?

HB

Relativity - the train would be going past you at light speed. Due to various lorentian fiddles with space make it possible

Its just the same as if I was on my train (at night), which was travelling at 1/2 light speed (assuming that they fix the track), and somebody shone a torch/serch light from behind me. The light would pass me travelling at light speed reative to me. However it would travel at light speed relative to the guy who was shining it.

Wait.. Like I said, I'm not a physics major, so please forgive me this ignorance.

If you're moving at lightspeed and someone who is behind you and standing still shines a light, you won't see the light until you stop, will you?

No, because you would be travelling at the same speed as light, but the rub is if you were moving towards the light, you wouldn't see it any sooner.... I think....

No, I'm not a physic major either, we must rely on Jon I believe!

HB

Revision of my above statement... If you moved towards the light, you would see it sooner(?), but the speed it travels through your eyeball would still be lightspeed despite your additional speed in the opposite direction........ (?)

I think I'll take up juggling jelly, it's easier to consentrate on.

HB

CHeEky (as I am) just to add my 2p worth, this is my version of time travel.
I believe that there are two dimensions. A wealthy dimension and a not so wealthy one . The way it works is by your pattern, when you are asleep here...you are awake there. The other dimension is the opposit to here (like Alice in the looking glass).

The rules are simple:-
You are the same person, with the same body and the same life, but look and feel better.
You live in the same way there as you do here but better
You speak to and spend time with the same people there, only better.
Society is not as harsh there as here.
Rules are made up on a daily basis, they can be silly or serious.
However break the rules there the penalty is paid by your doppleganger here twofold.
The twist is that from there you can see and interact (on a limited scale) what is happening on this dimension (only to yourself), but you can't reverse the action (like a one way mirror).
Once you have completed your day there and have gone to sleep that is when you wake up here and do whatever it is you do best, and so the cycle goes....
Your dreams are a memory of the life you are leading in the other Dimension.
This is why when you have a catnap, it feels as though you've been asleep for hours.
Think about it, it makes sense.

&
CHeEky

Makes more sence than the rest of this conversation.

Hey, Cheeky, I've read theories like that in scifi books (not dissing it, just saying). In the book, a few people accidentally go into the "other" dimension and various things happen. When they get a chance to rest, they fall asleep and dream, which puts them in the original (ours) universe. Interesting way of thinking about it.

But what's it got to do with time travel?

The problem with trying to exceed the speed of light and time travel like that is that it is impossible for a solid object to exceed the speed of light. The reason for this is that as any solid object goes faster, it collects mass. By the time a solid object reached the speed of ight, it would have an infinite mass, which is something we could all easily see as being a rather large problem. The way to go would indeed be through a wormhole, as mentioned above, but the difficulties presented by that solution give rise to whole new problems, not to mention new branches of physics and whatnot. The best way to go about time travel would be to find a way to open a hole in the space-time continuum. Find a way to puncture it and step through the puncture. It would be cheaper than building an entire spaceship.

It doesn't realy have much in the way this con. has progressed, To me the theory of relativity is too hard to understand and if I tried I would just hurt my pretty little brain. My version just makes sense to me, its a theory that started as a child and has progressed from there.
The relationship to time travel is that when you are asleep, you've managed to travel through time to a different dimension, you've broken all the barriers (the speed of light etc), and all from the comfort of your own bed, and you don't even have to be a scientist to do it.
I'm well pleased to that there a similar theory in a science book it makes me feel intelligent- not that I'm not, I'm just studied a different subject.
I would love to give time travel a go if the opportunity ever arose, but if it did I know I would want to change history. Which brings up the question:-
What would you change in history and why?

I may have just bypast this con. altogether and be waffling on (as you do), but I've had fun doing it.


CHeEky

If I could change history, I'd warn myself (as I think a lot of people would) away from some of my more embarassing gaffs.

But go farther back in the conversation (I do believe that it was the second page), I offered my logical (if not necessarily correct, I think it makes sense) debunking of the standard time paradox.

-Euphoric even after moving furniture all day ....

As I said on my first interjection

"Abstract concept time! Like beauty in a painting, like something being scary. It's different to all of us, I may like to think of a cyclic process, much like water, where we are in one position and the water flows past us in the stream, we know about the stream but we don't know about the sea, the clouds or the rain!

You may like to think BS!!!!!!!"


I feel I would be too un-nerved to "change history", even though we wouldn't be aware of the changes happening (Euphoric ). My life, though having ups and downs, ain't exactly a bad one. I'm happily married, I enjoy good health, I enjoy beauty and natural highs as I walk and cycle, this all (at the moment) beats the crp that seems sent to test me. Imagine if, out of greed, I tried to better my life and (let's say chaos theory) it all spiralled out of control, making a living hell and yet I couldn't identify the cause.

AAAAAARGH !!!!!!!

HB

Hmmm, Dotblack has a point. I LOVE my life. I don't think I would change anything. Thanks for pointing it out.

(Those who have been following this conversation might note that, although I've admitted to the possibility, I've never previously admitted to being wrong. w00t!)

you are traveling through time, but it is only in one direction and only at one speed, so it isn't conciderd to be the same time travel that everyone talks and wonders about.

good day i am Gandolf the Grey. i have read this strand and thought it would be a good place to enter my findings.


i have been here from just after the begining. i fought in that epic between good and evil. being this olde you learn a few things about time.

there is no future. it dosen't exist........yet. tomarrow a few hours from now will be last night. it is impossable to travel into something that doesn't exist.

however. the past does exist. we have forged it with our life's blood. it is possable to go back in time. but why. there is nothing there. the only thing that is there is an empty abandoned world. the only place people exist is in the present. you can't go visit your young self because you are you no matter what age you are.