SCI: Time Travel 101: A How To Guide

reply to post by spy66

Lets do some math.

You are going to travel at 300 000 km a second.

I am going to travel at 150 000 km a second.

Earth is going to do what earth does best.

We are both going to start at the same spot. And at the same time 0.

So our starting point is 0. On the same day.

After 1 second you will be 300 000 km away from earth. Because you travel at 300 000 km a second. I will be 150 000 km a way from earth because i travel at 150 000 km a second. From you i will be a 150 000 km.

When we stop after 1 second and compare time and date. Your watch will show 1 second. My watch will chow 1 second.

Hey but that's not true. If i call you my message would take 0.5 seconds just to reach you. So when you get my message your watch will show 1.5 seconds. But hey!! so will mine. When you get my message my watch will show 1.5 seconds too. And when you reply back i will get your message 0.5 seconds later. And my watch will show 2 seconds, but so will your watch when i get your message.

Then you call earth and ask them what time and date they have. And they say we have 3 seconds and the same date. But when you get the reply from earth your watch will show 4 seconds. The reply would also takes 1 second to return to you.

But if i listen in on the reply from earth my watch will show 3.5 seconds. because it will reach me before you. But when i hear the message at 3.5 seconds, the time will be the same on your watch. Its just that you haven't heard the message yet. When you get the message 0.5 seconds later. Your time will be 4 seconds. But so will mine and so will the time on earth.

Ok lets move on.

We travel for another 4 seconds. And stop and compare time and date.
This time when we stop the watch shows 8 seconds. It will be 8 seconds for you and 8 seconds for me and for earth.

But when we start communicating that's when things start to change even more. But time hasn't changed for any of us. But the distance between us have. So its going to take even longer to communicate. Because the message has to travel the distance as well.

Ok, I can see major confusion here.

Firstly, even though it's impossible, but we'll let it slide to keep your scenario simple ... we're going to assume that both you and I don't waste any time in building up speed from 0 to 300,000 km/s and 150,000 km/s or in slowing down from those speeds back to 0. We simply reach those speeds instantaneously ... ok ?
Actually, let my speed be 299,999 km/s (a piddly 1km/s difference) as it's impossible to hit light speed itself but this won't change your scenario to any extent at all.

Next ... if I'm travelling at 299,999 km/s even for such a short period of time as you stipulated, relativistic effects CANNOT be ignored.
The same goes for your speed of 150,000 km/s ... relatavistic effects also CANNOT be ignored.
If we did ignore them, then any conclusion that we reach would be badly flawed !

Ok, now for some maths of my own

When relatavistic velocities are involved, we need to use the Lorentz Contraction equation

D = √(1-(v²/c²)

to calculate the amount that our respective clocks diverge from that of a stationary observer back on Earth.

For a velocity of 299,999 km/s, my onboard watch will instead of showing that 1 sec has passed as it will for someone on Earth, actually shows that ONLY 0.0025 sec has elapsed during my journey of almost 300,000 kms.

As for your watch, it also shows that less than 1 sec has elapsed for you and in your case that's 0.86 sec or just over 3/4 sec.

So without needing to continue with this scenario any further, you can see that we have an immediate and substantial difference in the times shown by the 3 watches !

Earth elapsed time = 1 sec
Your elapsed time = 0.86 sec
My elapsed time = 0.0025 sec

reply to post by gormly

Two questions:

1. How come "light" itself can get around this "mass" issue?

2. And how exactly is light propelled?

Glad that you're enjoying giving your brain a good workout !

Ok, question 1 ... light can travel at EXACTLY this velocity because it's essentially a particle that has NO mass and because whenever a photon (light particle) is created, it's IMMEDIATELY and ALREADY travelling at light speed and doesn't need to continuously get a kick in the backside to make it go faster and faster. Just one of those things about the universe that we simply have to ACCEPT !

Hmmm ...I think I just answered question 2 as well !

Hope that helped make things a bit clearer for you ....

reply to post by tauristercus


Ok lets use your time if that helps.

In 0.0025 sec you will be at 299 999 km. And when you stop. your watch will show 0.0025 sec.

Now when you stop what do you think the time on earth would be?

Would it be 1 second ? No you would have to travel a lot longer. But it wont change anything. Only the distance traveled in time.

If you travel in 0.025 seconds and returned. you would be back on earth at 0.05 seconds.

We would have problems clocking that But you would arrive 0.05 seconds later.

Not 20 seconds later.

[edit on 27.06.08 by spy66]

Originally posted by tauristercus
Just one of those things about the universe that we simply have to ACCEPT !

Sorry, I can't accept that something with no mass (mass essentially being "something"):

1. Exists
2. Is traveling at 186,000 miles per second with no method of propulsion.

That's why I asked.. and no matter who I ask, I always get the same reply.

"we simply have to accept it"

This isn't a challenge to your assertions or the realities we live in, it's the inability of my feeble brain to wrap itself around it....

I am just continually saddened that we don't really know enough yet and we are really just working with suppositions.

But yea, my brain is thinking again today and that's a nice bonus. Thanks!

Originally posted by gormly

Originally posted by tauristercus
Just one of those things about the universe that we simply have to ACCEPT !

Sorry, I can't accept that something with no mass (mass essentially being "something"):

1. Exists
2. Is traveling at 186,000 miles per second with no method of propulsion.

That's why I asked.. and no matter who I ask, I always get the same reply.

"we simply have to accept it"

This isn't a challenge to your assertions or the realities we live in, it's the inability of my feeble brain to wrap itself around it....

I am just continually saddened that we don't really know enough yet and we are really just working with suppositions.

But yea, my brain is thinking again today and that's a nice bonus. Thanks!

Well light travels at 186,000 miles per second in a perfect vacuum i guess that the vacuum is the propulsion force.

But i dont know how they could say that when no one knows if a perfect vacuum even exists.



[edit on 27.06.08 by spy66]

reply to post by spy66

In 0.0025 sec you will be at 299 999 km. And when you stop. your watch will show 0.0025 sec.

Now when you stop what do you think the time on earth would be?

My elapsed time will be 0.0025 secs.
Earth elapsed time will be 1 sec.

Would it be 1 second ? No you would have to travel a lot longer.

Yes it WILL be 1 second !

If you travel in 0.0025 seconds and returned. you would be back on earth at 0.005 seconds.

Absolutely correct (assuming an impossible INSTANT turn around and no loss in velocity).
That would be 0.005 seconds had elapsed on MY watch .... BUT 2 seconds on an Earth watch.

Thnk about it this way ... someone watching from earth would see me travel 1 light second away from Earth (299,999 km in 1 sec) and then travel the same distance (1 light second) back again. After all, I'm travelling at the speed of light from earths point of view and the max distance I can reach in 1 sec at light speed is 300,000 km. Then exactly the same distance back again gives someone on Earth the following times ... 1 sec there + 1 sec back = 2 secs round trip from their point of view.

Are you absolutely sure you understand the concept of time dilation that occurs at relatavistic speeds ? I know it can seem to be somewhat confusing ....

Originally posted by tauristercus
reply to post by spy66

 

In 0.0025 sec you will be at 299 999 km. And when you stop. your watch will show 0.0025 sec.

Now when you stop what do you think the time on earth would be?

My elapsed time will be 0.0025 secs.
Earth elapsed time will be 1 sec.

Would it be 1 second ? No you would have to travel a lot longer.

Yes it WILL be 1 second !

If you travel in 0.0025 seconds and returned. you would be back on earth at 0.005 seconds.

Absolutely correct (assuming an impossible INSTANT turn around and no loss in velocity).
That would be 0.005 seconds had elapsed on MY watch .... BUT 2 seconds on an Earth watch.

Thnk about it this way ... someone watching from earth would see me travel 1 light second away from Earth (299,999 km in 1 sec) and then travel the same distance (1 light second) back again. After all, I'm travelling at the speed of light from earths point of view and the max distance I can reach in 1 sec at light speed is 300,000 km. Then exactly the same distance back again gives someone on Earth the following times ... 1 sec there + 1 sec back = 2 secs round trip from their point of view.

Are you absolutely sure you understand the concept of time dilation that occurs at relatavistic speeds ? I know it can seem to be somewhat confusing ....

Yeah i think so

Well how could it be.

I raised the time by 10 one way (10 times 0.0025) that becomes 0.025 seconds. It would take 10 times 0.0025 seconds to get back. Don't you have to do the same with 1 second.

If i time the speed of light by 10 you would have to do the same to 1 second.

10 times 1 is not = 1






[edit on 27.06.08 by spy66]

Originally posted by spy66

Well light travels at 186,000 miles per second in a perfect vacuum i guess that the vacuum is the propulsion force.

How is a vacuum a method of propulsion?
Isn't that just a medium?

reply to post by spy66

I raised the time by 10 one way (10 times 0.0025) that becomes 0.025 seconds. It would take 10 times 0.0025 seconds to get back. Don't you have to do the same with 1 second.

Sorry, I must have missed the shift you made in the decimal point.

If I travel 10 times the distance at 299,999 km/s, my time dilation relative to an Earth watch would STILL be 0.0025% as it makes NO difference how far I actually travel ... so it would take me 10 x 0.0025 secs = 0.025 seconds OF MY TIME to travel the 10 light seconds of distance away from Earth.

Meanwhile, an Earth watch would show 10 x 1 sec = 10 seconds EARTH TIME had elapsed ... which makes perfect sense as for someone on Earth watching a light beam will obviously agree that the MAXIMUM distance that light beam can travel in 10 earth seconds is 10 x 299,999 kms ... which is EXACTLY the distance I travelled one way.

PERFECT AGREEMENT !

Originally posted by gormly

Originally posted by spy66

Well light travels at 186,000 miles per second in a perfect vacuum i guess that the vacuum is the propulsion force.

How is a vacuum a method of propulsion?
Isn't that just a medium?

Well light is energy from matter. In a vacuum matter would try to shrink as much as it can. But why would it give of light?

Why wouldn't light just be stationary around the matter producing it when the vacuum pools matter together. And why wont it slow down or speed up in the vacuum?

Originally posted by spy66

Well light is energy from matter. In a vacuum matter would try to shrink as much as it can. But why would it give of light?

Why wouldn't light just be stationary around the matter producing it when the vacuum pools matter together. And why wont it slow down or speed up in the vacuum?

This dialog between you and me is like two boxers fighting each other in opposite directions.

Originally posted by gormly

Originally posted by spy66

Well light is energy from matter. In a vacuum matter would try to shrink as much as it can. But why would it give of light?

Why wouldn't light just be stationary around the matter producing it when the vacuum pools matter together. And why wont it slow down or speed up in the vacuum?

This dialog between you and me is like two boxers fighting each other in opposite directions.

Well i am not sure about the answer either. So i am fishing for some information as well

in concept there is a ratio relationship between time and space... the faster you go the greater your ' mass ' kinda ...
the basic Idea is... at infinite speed... you are the size of infinite space .
because the speed of light is " kinda" the infinite speed... you fill all space

if N= infinity

Ne= Nm xc xc is true

infinite's are funny like that

reply to post by spy66

Well light is energy from matter. In a vacuum matter would try to shrink as much as it can. But why would it give of light?

Why wouldn't light just be stationary around the matter producing it when the vacuum pools matter together.

There's nothing in physics that states that matter has any tendency to "shrink" as much as it can when in a vacuum. Perhaps a bit more info as to what you're trying to say, please ?

Matter only emits light when electrons in the outer shell of the atom absorb energy and get raised to a higher energy level ("excited"). After a random time, these "excited" electrons spontaneously drop back down to a lower energy level and gives back this previously absorbed energy by emitting radiation in the form of a photon.

And why wont it slow down or speed up in the vacuum?

It's one of those things that we simply have to accept about the universe ... that when created, a photon IMMEDIATELY travels at light speed in a vacuum ... it doesn't speed up and it doesn't slow down. As long as the photon exists, it will ALWAYS travel at EXACTLY light speed in a vacuum.

Originally posted by readerone
in concept there is a ratio relationship between time and space... the faster you go the greater your ' mass ' kinda ...
the basic Idea is... at infinite speed... you are the size of infinite space .
because the speed of light is " kinda" the infinite speed... you fill all space

if N= infinity

Ne= Nm xc xc is true

infinite's are funny like that

A thing that possels me is how can we say that a photon travels at a infinite speed when we can observe it as (c) or as 300 000 km a second in a perfect vacuum?

300 000 km a second is not a infinite speed?

infinite is 0 witch means speed and distance is = 0 time no matter what the distance is.

Would that mean that the photon we see is just a fraction of what it really might be?







[edit on 27.06.08 by spy66]

You know what really makes my brain hurt?


Not all this "light speed" and "time travel" stuff.. nope, that's child's play compared to the real brain teaser.

My real question is much more complex (and damaging to the soul I think)...

We know there is a beginning, an end and measurements to all things, time, space, mass. We know the universe is made up of immeasurable amounts of varied materials. We can debate, discuss, inspect and conclude all kinds of things from what we know, what will will come to know, but what we don't know and never will know can be summed up into two simple questions.

1. From where did all this material (Universe) originate?
2. What was there before the materials (Universe) originated?


Yea, think about that for a while.
Makes time travel seems like a walk in the park.

(I'd still like to walk in that park)

Originally posted by tauristercus
reply to post by spy66

 

Well light is energy from matter. In a vacuum matter would try to shrink as much as it can. But why would it give of light?

Why wouldn't light just be stationary around the matter producing it when the vacuum pools matter together.

There's nothing in physics that states that matter has any tendency to "shrink" as much as it can when in a vacuum. Perhaps a bit more info as to what you're trying to say, please ?

Matter only emits light when electrons in the outer shell of the atom absorb energy and get raised to a higher energy level ("excited"). After a random time, these "excited" electrons spontaneously drop back down to a lower energy level and gives back this previously absorbed energy by emitting radiation in the form of a photon.

And why wont it slow down or speed up in the vacuum?

It's one of those things that we simply have to accept about the universe ... that when created, a photon IMMEDIATELY travels at light speed in a vacuum ... it doesn't speed up and it doesn't slow down. As long as the photon exists, it will ALWAYS travel at EXACTLY light speed in a vacuum.

Sorry but i dont read anything i just make the thoughts and equations on my own.

But if i focus on matter and energy compared to a vacuum.

The compression wont exceed the pressure of the vacuum.
Everything is made up by different types of pressures.

A vacuum has no pressure, temperature, time or matter. So if you get a matter into this vacuum it will do a great deal to the matter. The vacuum will make the matter change all the time. That means it will shrink by giving of energy. The matter wont expand in a vacuum. But the energy will. The energy will leave the matter because of the pressure differential applied by the vacuum.
The energy will also change because energy is just a finite state in time. And that to is because it is different then the vacuum it travels in.

Also when this energy leaves the matter. It will also give the matter real mass. Meaning the atmosphere of energy will create a new differential in pressure between the vacuum and the mass. This atmosphere of energy will give the outside layers weight/pressure down to the core of the mass. In return this will create heat at the core of the mass. And work as the second catalyst for giving of pressure at the top layers of its own mass. The heat will travel up or out where the pressure is lower.

WoW maybe this is how planets where really made



[edit on 27.06.08 by spy66]

reply to post by gimme_some_truth


Love the post, I also have been a big fan of time travel since I was a kid. Some thing I always think about is...

1. Will we ever have the technology to time travel?
2. If in the future we do get this technology, will we ever used it?
3. And if we have, of course we wouldn't know it now. because we would have no idea that time has changed, because we would be part of that change.

Thanks again for the post, no need to answer these questions, just random things I think about

-JP

[edit on 11-8-2009 by JohnParanorm]

reply to post by gimme_some_truth


I recommend looking into M Theory.

Originally posted by ThinAir

What would happen if there was some sort of 'live stream' video active from the ship to Earth at the start of the journey, through the two years?

How could the people on Earth, for 27 years, be watching a video of a man in space, who is only there for 2 years?

I mean, would the image of the man in the ship be in extreme slow motion?

It really fascinates me!

I'd love to hear your answer, thanks Gimme_some_danger, this is an extremely active and interesting thread!

Hi, first, let me apologize for missing your original post in this thread. As you pointed out, this thread has grown so fast in the past few days and has spawned some amazingly interesting conversation.

Now, let me say that you question reminds of of the movie Contact, based on the book by Carl sagan.

You see what happened at the end was after they built this mysterious machine Ellie ( The main charachter) was chosen to go for the ride and be transported to another world. Well she ended up going through worm holes and traveling all through space ending up at the place that the signal they picked up first came from. After visiting with the aliens, it cuts all of a sudden to Ellie back on earth falling in the machine and landing in the water.

They too had a camera in side of her craft. From the view point on earth her trip appeared to be only a few seconds. Her trip appeared to consist of falling a few hundred feet into the ocean. But the tape had recorded several hours of static.

Now, I realize these are two different ideas we are talking about but that is what it reminded me of.

As for what would happen where the special theory of relativity applies... I don't know. All I keep picturing in that scenario is a video of what appears to be playing in slow motion, only it is not, it is live streaming... That is assuming we ha a new way to get the signal to earth really fast, the radio waves we use today might take quite a while to get here if we were light years away...

Now I don't know if that is what it would look like, but that is how I picture it anyway.

[edit on 11-8-2009 by gimme_some_truth]