Stephen Hawkins Universe - Time Travel

[Robosapien]

Don't they both just experience exactly the same, but time is just said to be different, therefore not really making any difference at all at the end of the journey? They'll both be the same age, and one will have been away for the same amount of time as the other one has spent on earth.

All sounds a bit pointless tbh.

I don't think it's simply a measurement problem, I think it's an actual real effect.

 

[Robosapien]

Hawkins had a problem with paradoxes in this episode. I don't think he's right about the feedback thing he suggested though, I think its simpler.
Paradoxes cannot exist imo. Let say for instance you go and try and kill your grandfather in the age old tale, and lets assume that every possible thing that can happen will happen.

If you go back and try and seperate your sucess into 2 catergories, 1-everytime you kill ur grandad, and 2-every time you don't. (everytime you don't could happen, from say the bullet being deflected by a bird or a falling branch, remember everything that does happen will)
So you now have two categories, but one leads to you death, and ones leads to you failure. So in theory, no matter how hard you try you can never kill your grandad, because the eventualities that result in a sucess live in a category that leads to your death and thus cannot happen, so they dont. The universe then only has half the eventualities it started with, and they will always lead to your failure, no matter how hard you try.

Is this Feynmans sum over all histories?? Or are you just saying it's highly improbable that it would happen?

 

[Robosapien]

Although a human construct, mathematics seems to occupy it's own world, with it's own consistencies, beyond spacetime. It stands to reason that we merely draw upon a small part of mathematics in order to describe the physical world, and that all maths does not accurately describe the physical world.
Castiel may have been wrong in his assertion that .99r doesn't equal 1, but the surely the point he is making is simply that infinitessimally small differences in velocity make an increasingly bigger difference in time dilation results as you approach the speed of light.
Quantum physics initially got it's name from the fact that light seems to come in discrete packages, so a continuious real number description wouldn't be appropriate, however I know this is no longer the case but I intend to read up on the details.

 

[Castiel]

You need to articulate this concept more precisely, because at the moment you've made several patently false statements. 100=99.9r inasmuch as 3 = 9/3.

OPPS! In my sobriety I see my fatal mistake.

I should have pointed out that after each decimal progression the calculation needs to be redone to see the exponential progression in time dilation. The (r) was misleading.

99---> 1/7
99.9 ---> 1/700
99.99----> 1/7000

And so on. I hope this clarifies.

 

[LordSplodge]

I'd add "Why Does E=mc2?" to that reading list. Brilliant book.

http://www.newscientist.com/article/mg20227141.700-review-why-does-e--mc2.html

Of course, it can be bought online from places I'm not allowed to mention here.

Agreed. An excellent book.

 

[DavidMarq]

I understand perfectly. Unfortunately you cannot grasp that I am not talking about a REAL number but a PROCESS, we add a decimal point to enable the equation to proceed, once we stop the process we reach infinity and only then 99.99r = 100, as we have reach a real value (that of c) until then we retain an infinitesimal difference between 99.99r and 100. You need to read up a little on quantum physics, a mass cannot physically attain lightspeed thus 99.99r is a valid representation, and different from 100 because the difference between 0.99r and 100 is a physical and measurable alteration in speed, not simply a mathematical construct that any pure mathematician will tell you is the basis of debate, even with the proofs, many of which Quantum Physicists ignore for this reason.

Utter tosh, nice rolleyes, ignorance is bliss.

You started off posting sense in this thread, but I'm afraid you're completely wrong on this one.

gamma for 0.9999r * c is infinite, the same way that gamma for c is infinite.
For any finite sequence of 9s gamma is not infinite, all we're arguing is that 0.9999r is not a finite sequence of 9s.

Yes

You need to articulate this concept more precisely, because at the moment you've made several patently false statements. 100=99.9r inasmuch as 3 = 9/3.

Yes

OPPS! In my sobriety I see my fatal mistake.

I should have pointed out that after each decimal progression the calculation needs to be redone to see the exponential progression in time dilation. The (r) was misleading.

99---> 1/7
99.9 ---> 1/700
99.99----> 1/7000

And so on. I hope this clarifies.

The penny drops.

(r) was not just misleading but patently wrong.

 

[Castiel]

The penny drops.
(r) was not just misleading but patently wrong.

No it was misleading, I used the (r) to show the progression when that was patently wrong, but the clarification was what I meant all along and if you look at the context you'll see that, I'm sure. It'll teach me not to get into such discissuiond after eight pints and a litre of JD.

 

[Castiel]

Although a human construct, mathematics seems to occupy it's own world, with it's own consistencies, beyond spacetime. It stands to reason that we merely draw upon a small part of mathematics in order to describe the physical world, and that all maths does not accurately describe the physical world.
Castiel may have been wrong in his assertion that .99r doesn't equal 1, but the surely the point he is making is simply that infinitessimally small differences in velocity make an increasingly bigger difference in time dilation results as you approach the speed of light.
Quantum physics initially got it's name from the fact that light seems to come in discrete packages, so a continuious real number description wouldn't be appropriate, however I know this is no longer the case but I intend to read up on the details.

That is what I meant, I'm glad someone saw through my alcohol induced haze of an explanation to see what I was attempting to explain.

 

[w11tho]

OPPS! In my sobriety I see my fatal mistake.

I should have pointed out that after each decimal progression the calculation needs to be redone to see the exponential progression in time dilation. The (r) was misleading.

99---> 1/7
99.9 ---> 1/700
99.99----> 1/7000

And so on. I hope this clarifies.

I don't really understand how that relates to the statement

sufficed to say 99.999 to infinite .9's will still not be 100

Regardless, I'm glad it's now understood that 99.9r (i.e. "99.999 to infinite .9's") is exactly equal to 100.

 

[Castiel]

I don't really understand how that relates to the statement

Regardless, I'm glad it's now understood that 99.9r (i.e. "99.999 to infinite .9's") is exactly equal to 100.

Because I wrongly assumed everyone knew that the calculation was done after every decimal progression, thus velocity and time dilation never converge. If they did then you are at 100% and you hit a paradox where you occupy all places at all times until the velocity progresses another decimal place and you then begin travelling faster than light and the time dilation reverses.

 

[w11tho]

Because I wrongly assumed everyone knew that the calculation was done after every decimal progression, thus velocity and time dilation never converge. If they did then you are at 100% and you hit a paradox where you occupy all places at all times until the velocity progresses another decimal place and you then begin travelling faster than light and the time dilation reverses.

There is no calculation. You claimed two numbers (100 and "99.999 to infinite .9's" to use your language) were different. They're not different - they are the same number.

 

[Castiel]

There is no calculation. You claimed two numbers (100 and "99.999 to infinite .9's" to use your language) were different. They're not different - they are the same number.

If you go back to the beginning of the argument you will see I was illustrating the point I clarified above, I made the mistake of using (r) to represent the decimal progression after each calculation using The Lorenz Factor equation to calculate the resulting time dilation from the increased velocity. This caused the confusion, added to my inebriated state of course.

 

[w11tho]

There was no "r" in your claim:

sufficed to say 99.999 to infinite .9's will still not be 100

So you can hardly attribute your faux pas to some sort of misinterpretation of notation! Look, it's no big deal. You had a few drinks and said something daft, we've all been there!

 

[Inquisitor]

The time dilation at only 99 percent the speed of light is not great enough for that period of Earth time to have passed in relation to Ship time.

One Lightyear is the distance it takes light to travel a specific distance....Thus in 80 years ship time, only 560 years would have passed during the journey. The Galaxy (milky way) is about 100,000 light years across so light would take 100,000 years to traverse the galaxy.

To extrapolate, a starship travelling at lightspeed would also take 100,000 years to traverse the galaxy (ship time), however back on earth due to relativistic time dilation 700,000 years subjective earth time would have passed.

Not quite. If the galaxy is 100,000 light years across in the lab frame (Earth), it will be roughly 14,000 light years across when seen by an observer travelling at 0.99c relative to the lab frame (due to length contraction) and hence the journey would take 14,000 years. This is why it is consistent for the journey to be much quicker for one party than for the other.

Edit: Missed the 6 pages between here and the quoted post. Oops!

 

[Souness]

It's always easy to tell who the trash talker is in physics threads - they always refer to a mysterious fictional character known as Stephen Hawkins.

 

[lixxus]

this guy beat Stephen Hawkin to it

 

[Castiel]

There was no "r" in your claim:

So you can hardly attribute your faux pas to some sort of misinterpretation of notation! Look, it's no big deal. You had a few drinks and said something daft, we've all been there!

I accept that I made a booboo, I was pointing out that what I wrote and what I meant to say where not the same. Hence my clarification.

The above quote shouldn't be taken in isolation, the context is still with the assumption that we do the Lorenz calculation after each progression. I just didn't explain it well at all and then proceeded to dig a big hole, get in it and then carry on digging....

Anyway I'm sure you get what I meant now, so I'll chalk it up to experience.

 

[SlugForAButt]

Whats black and sit's at the top of the stairs?

..............................................................

Stephen Hawkings in a house fire.

 

[Castiel]

Stephen Hawking and Christopher Reeve walk into a bar...Oh Wait.

 

[w11tho]

The above quote shouldn't be taken in isolation, the context is still with the assumption that we do the Lorenz calculation after each progression. I just didn't explain it well at all and then proceeded to dig a big hole, get in it and then carry on digging....

Anyway I'm sure you get what I meant now, so I'll chalk it up to experience.

You can talk about whatever context you like. Whether it be basic special relativity, or deep index theorems in functional analysis. It still doesn't detract from the enormity of the booboo!

However, I'm very much an advocate of post-five-pint physics - so I wouldn't worry about it too much!