# Time Travel is Science Fiction

Discussion in 'Alternative Theories' started by Farsight, Feb 17, 2014.

1. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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CONCLUSION (for lazy readers): Calculations by laws of physics show that traveling by rocket ship, the traveling twin cannot return even 5 years younger than his “stay at home brother.” As the time traveler could age a maximum of 7.36 years while his staying home twin ages 1.57x7.36 = 11.55 years.
To even do that, if a standard D/T fusion reaction is used, the fuel mass ONLY at launch is 837 times greater than the mass of Earth!

To show the extremely difficult actually doing only slowing aging by a factor of (7.14/4.5) = 1.57 via a rocket ship, I post physics from this link: http://www.astro.cornell.edu/pdfs/relrocketderiv.pdf
{Most equations are omitted and text in these “curly brackets” was inserted in the quotes by Billy T.}

“.. Consider a rocket that accelerates uniformly. This means that the acceleration is fixed in the rocket rest frame; let the acceleration be a. Now suppose we wish to go a total distance D in the Earth frame going out halfway at a uniform acceleration, a, and then the rest of the way at uniform {reversed} acceleration -a so that we arrive at our destination with zero speed.”

{Note their analysis is for a “one way” trip and in later numerical results, D = 4.5 light years as the destination is Alpha Centaurus. Also the acceleration assumed for the trip is acceleration of Earth's gravity. I. e. a = g = 980 cm /sec^2 ≈ 1.03c / year. They define m as the mass of the rocket when it has attained speed v {max speed at the half way point} and m(0) is the much larger mass at launch. We can assume when half way the crew yaws their space craft 180 degrees so it ends up back on Earth, instead of near Alpha Centaurus.}

“Note that the astronauts age less than 4.5 years, {getting to full stop near Alpha Centaurus} a reflection of their relativistic motion and time dilation.” {While their twins on earth age 6.14 years} “The amount of fuel consumed during the journey depends critically on the value of v0.” {Speed of the exhaust relative to the rocket, a constant if the fuel never changes. Speeds are “normalized” by the speed of light c.}

{The best conceptually possible exhaust is only gamma rays - no real mass is discarded. It is 100% converted to energy. However only way to make them is particle / anti-partial annihilation and then the gammas go in opposite uncontrollable directions.} “In this case, m(0)/m ≈ 42. But this is a lower bound on this ratio. For more realistic rocket fuel, the requirements are more stringent. Nuclear energy derived from H fusion, {assuming that can be done}, is a more practical source of fuel, would have v0 ≈ 0.122, and in this case we would have m(0)/m ≈ 2 × 10^13. {I. e. Gamma ray exhaust is fantastically more “mass efficient,” However, even if that were possible, the intensity required for 1 g acceleration is so great that the heavy thick lead shield for the traveler(s) would be glowing red hot even with huge internal cooling coil flows and that refrigerator's needs would dominated the power requirements*}

“For nuclear fuel, a practical limitation on the maximum distance that can be traveled may be derived from assuming that at most all of the H in the solar system could be packed along as fuel. That amounts to something like 10^30 kg of H. Even with the most Spartan design, it seems hardly possible for a spaceship to weigh less than a ton, or about 1000 kg. Thus, a practical limitation would be m(0)/m 10^27.”

{I. e. You need for reactor's fuel more than half the mass of Jupiter, the largest planet, inside your fuel tank, at lift off from Earth! (even if it is only hydrogen, not a 50/50 mix of D/T.)
Also total empty space craft weight of only 1000 kg with that m(0)/m ratio is ridiculously optimistic – you can not hold more than half the weight of Jupiter in 10^6 gram tank! But I'll continue using their numbers.}

“For such a spacecraft, the distance traveled cannot exceed about 41.06/(a/g) light years! Longer trips can be made at lower accelerations, since the distance traveled is inversely proportional to the acceleration given m(0)/m, but the biological effects of protracted living at sub-g gravity may be prohibitive. The astronauts would age about 7.36/(a/g) years during this longest possible nuclear powered journey.”

{Please note I try to spread physics facts, not BS - this thread is "saturated" with repeated copies of same BS and inane short posts already.}
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Now consider making a worm hole humans could travel thru, although that is almost certainly impossible to do. I. e. probably is not possible, but if it is, doing so takes more mass energy in “exotic mass” than is known to exist. Also most of space time is so nearly “flat” that which way it curves, if it does, is not certain; yet some section of that space time must be “bent” approximately U-shaped in central cross section so the time required for traveling around normal surface of the bent U is greater than traveling to cross between the tops of the U, if and when they are connected via a worm hole, which of course needs to be made (and stabilized against its strong tendency to collapse – to again cease to exist.)

At the start this essentially impossible construction task the Space Bending Machine, SBM, needs some where to “stand” as it starts making just a small “dimple” in the flat space time. Then it needs to orbit the depression it is producing to avoid simply falling in due to the new gravity (curved space) it is making.

Also the “dimple” is much more like a long trough. Somewhat like the start of a bend in a flat sheet of paper. - An elongated “trough dimple” shape is very hard to “orbit” but I will continue, for want of a better word, to say the SBM “orbits” around the initial elongated depression it is making in space time.

Thus to “deepen the long trough dimple” the SBM must “de-orbit” some more “exotic mater” so it can fall into the beginning of the depression in space time. Not at all clear, even in principle, how this exotic material can be “slowed from orbit” to fall without some normal matter touching it – big explosion etc.

More ill defined procedures needed as this is just the start of worm hole making. - AFAIK, no one discusses how one could be made or stabilized against collapse, if it could be made, so I certainly will not venture any guesses. – I just wanted to note that the process starts by making a slight elongated “trough dimple” in flat space-time by using (negative gravity?) “exotic mater,” which probably needs to be created there by unknown processes (but requiring at least the energy E = Mc^2 of it and accelerators to collide normal mater to produce it. Last time I looked, any such accelerator cost billion dollar or more and weighed more than 10,000 tons. That SBM will be something to take you children to see.).

Last edited by a moderator: Dec 10, 2014

3. ### brucepValued Senior Member

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We won't be doing any interstellar journey using that type of technology. We'll need a sub-light warp drive that can create a spacetime where the rocket constantly slides down a g_earth gradient over the warp spacetime. We wouldn't be burning any fuel. We'd be changing the local spacetime curvature by introducing a huge electromagetic charge and manipulating to get the spacetime we want.

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I'm not going to address the numerous erroneous concepts and lies in your post Billy, suffice to say that you, driven by your emotions, have sunk to the Farsight level of dishonesty.
That is sad especially for a mod.
Again, I reiterate what I have claimed in this and the other time thread.
[1]THE LAWS OF PHYSICS AND GR DO NOT FORBID TIME TRAVEL, AND THE EQUATIONS OF GR GIVE THEORETICAL SOLUTIONS AS TO HOW THAT MAYBE ACHIEVED:

[2]ANY SUFFICIENTLY ADVANCED CIVILISTATION COULD ACHIEVE IT:

I also reiterate other facts.....
[a]NO LINK I HAVE GIVEN AND NO OTHER LINKED PROFESSSIONAL OPINION HAS CONTRADICTED [1] AND [2] ABOVE.
There are many methods as to how time travel maybe achieved by any sufficiently advanced civilisation.
[c] Time dilation and its effects are one of those methods.
[d]That has been mentioned by both Carroll and Thorne and the others also.

What I have never said is that.......
TIME TRAVEL IS 100% POSSIBLE: or that TIME TRAVEL WILL HAPPEN:

What you chose to deny is of no consequence in the greater scheme of things.
But what I would say, and which I have generally only put to the many alternative hypothesis nuts we get on this forum, is the following.
If you are so confident that the laws of physics and GR do forbid time travel, [and that is what you seem to be implying mixed with your over-bearing loads of bullshit] then via the scientific method, gather your evidence and incomplete mathematics and get it peer reviewed.

Now I certainly hope that as a forum moderator, you take a more honest, factual, approach to this question, and what I have claimed, and cease the Farsight like devious methodology you have used in your previous post.

All my links have been given, and I'm rather tired of having to rehash them for the likes of you.
But here is a new one, around 60 minutes in length from a lecture by Sean Carroll.

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The point is brucep, that although much of the technology to get to the stars etc are beyond present capabilities, and we all know that.
It's just the down right dishonest and stupid attempt in using our technological limitations now, to somehow infer that it can and will never be done.
How obtuse! how dishonest! how stupid!

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A couple of questions that no naysayer has yet had the guts yet to answer...way back in post 1250.

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Just once again to re-right the lies that have been expressed in certain posts re what Thorne has said and what he hasn't said.......
http://plus.maths.org/content/time-travel-allowed
In brief: The laws of physics allow members of an exceedingly advanced civilisation to travel forward in time as fast as they might wish. Backward time travel is another matter; we do not know whether it is allowed by the laws of physics, and the answer is likely controlled by a set of physical laws that we do not yet understand at all well: the laws of quantum gravity. In order for humans to travel forward in time very rapidly, or backward (if allowed at all), we would need technology far far beyond anything we are capable of today.
http://plus.maths.org/content/time-travel-allowed

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10. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Nice dream, but I still like Santa Claus's sled pulled by team of rain deer better.

11. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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I have answered it twice. I.e. noted that is IMPOSSIBLE to PROOVE any thing is impossible (outside of closed tautologies, like math).

12. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Yes that is the first headline grapping sentence of that link. A brief version of what will follow he says.
Here is the first sentence of the third paragraph, where he begins to amplify what he means by it:
"This personal character of time allows one person to travel forward in time much faster than another, a phenomenon embodied in the so-called twins paradox."

I agree with Thorne that the traveling twin can age less or speed forward in time, faster than his stay at home bother does as the bother goes forward in time at the normal rate of 24 hours per day, like we all do.

You read into the first sentence something more than the twin paradox. Neither Thorne nor Einstein nor any Ph.D. In physic distorts the twin paradox as you do. There are at least four different means, for example, to slow your rate of aging so in you with only a week of aging race forward 10 days that others need to age by 10 days to arrive at the same calendar date.

SUMMARY: Again you are "cherry picking" to support your POV rather than trying to understand what Thorne means.

Last edited by a moderator: Dec 10, 2014
13. ### LaurieAGRegistered Senior Member

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I note when you first posted you mentioned aliens and time travel but you edited it before I could respond.

How about letting us know what Kip Thorne et al think about alien civilisations and time travel?

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Stop dodging and weaving and avoiding the obvious. Is time travel allowed by the laws of physics and GR? What does the equations of GR say about time travel?
Could a sufficiently advanced civilisation achieve it?

15. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Paddoboy note that the laws of physic do NOT change from those of the future AFAWK yet Thorne strongly doubt the allow time travel as you use the term to mean more than just the twin paradox. I.e. None of can travel back into the non-existing past nor the non-existing future. The past slips away for all at 24 hour/ day rate but their re means for your body to age at only 22 hours per day as you travel into the future days,

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I don't see anything refuting what the laws of physics and GR say about time travel.

No it is you reading into Thorne's statement and every other expert's statement, exactly what you see to support your erroneous concept that time dilation can be inferred as time travel.
Show me anywhere, where any of the professionals have said anything like time dilation Is not time travel.
You can't, because they all agree it is a form of time travel.

17. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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We can and do, travel into the future at 24 hours per day rate. Some can travel to the same calendar day with slightly less biological aging. That is what is allowed by GR. - that and only that. Not travel into a future (or past) that does not exist.

18. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Nor do I. GR does allow some to only age 22 hours biologically while going to a calendar date most need 24 hours per day of biological aging to reach.

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I'm sure if you need to know what he thinks about Alien civilisations and time travel, you could find it.
But knowing him as a world authority on BH's, gravity, and time travel, I'm pretty certain he agrees that any sufficiently advanced civilisation could achieve it.
And no, I did not post anything from Thorne about Aliens, other then what is in that link I gave.
My only reference to Aliens is the fact, that any sufficiently advanced civilisation, [Alien or even us in the future] could achieve time travel.
But again, knowing Thorne from what I have read of his, I'm again sure he believes the logical assumption that Aliens do exist somewhere, sometime, despite no direct evidence supporting that idea.

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Billy, as I tell most alternative hypothesis trolls, if you see the laws of physics and GR forbidding time travel, then gather what you have and get it peer reviewed, and stop your childish nonsensical analogies and misrepresentations, which you have been repeating from day one.

21. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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people don't often say what something is not, unless asked. At your link here is what Thorne does say:
"These time travel phenomena have been tested in the laboratory. Muons — short-lived elementary particles — travelling around and around in a storage ring at 0.9994 of the speed of light, at the Brookhaven National Laboratory on Long Island, New York, have been seen to age 29 times more slowly than muons at rest in the laboratory. And atomic clocks on the surface of the Earth have been seen to run more slowly than atomic clocks high above the Earth's surface — more slowly by about 4 parts in 10 billion." (I added the bold.)

I.e. he calls aging more slowly a time travel phenomena or a FORM of time travel and I ave agreed with that for 55+ years. Yes you can reach a future data with less biological (or Thorne's "personal time") laps than most biologically age to reach that same date.

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Again, the laws of physics and GR do not forbid time travel [as generally accepted as time travel]and the equations of GR give theoretical possible solutions.
And all professionals so far have seen it as the way I have stated. All of them...

"""""""""""""""""""""""""""""""
Carl Sagan Ponders Time Travel
http://www.pbs.org/wgbh/nova/physics/Sagan-Time-Travel.html

Highlights of what he says......
"It might be that you can build a time machine to go into the future, but not into the past."

"Maybe backward time travel is possible, but only up to the moment that time travel is invented."

"Time travel into the indefinite future is consistent with the laws of nature."

How is the speed of light connected to time travel?
A profound consequence of Einstein's special theory of relativity is that no material object can travel as fast as light. It is forbidden. There is a commandment: Thou shalt not travel at the speed of light, and there's nothing we can do to travel that fast.

The reason this is connected with time travel is because another consequence of special relativity is that time, as measured by the speeding space traveler, slows down compared to time as measured by a friend left home on Earth. This is sometimes described as the "twin paradox": two identical twins, one of whom goes off on a voyage close to the speed of light, and the other one stays home. When the space-traveling twin returns home, he or she has aged only a little, while the twin who has remained at home has aged at the regular pace. So we have two identical twins who may be decades apart in age. Or maybe the traveling twin returns in the far future, if you go close enough to the speed of light, and everybody he knows, everybody he ever heard of has died, and it's a very different civilization.

It's an intriguing idea, and it underscores the fact that time travel into the indefinite future is consistent with the laws of nature.