No Time Travel, Sorry 888
MOBE2001 writes "The bad news is that time does not change. Spatial velocity is given as dx/dt. Velocity in time(dt/dt) is nonsensical. As simple as that. In other words, no time travel to the past or the future, no motion in space-time, no wormholes and no hanky-panky with your great, great grandmother. There is only the changing present, aka the NOW. The good news is that distance is an illusion and we'll be able to travel instantly from anywhere to anywhere."
The e-mail I sent to the editor was ignored. (Score:5, Informative)
This guy is a pseudo-scientific moonbat. Please don't waste your time with the not-so-FA.
Comment removed (Score:3, Informative)
Re:The e-mail I sent to the editor was ignored. (Score:5, Informative)
http://www.rebelscience.org/Crackpots/notorious.ht
http://www.rebelscience.org/Crackpots/nasty.htm#Sp
(emphasis mine.) That alone should make it pretty clear that this isn't meant to be taken seriously. Oh yeah, and the story got the "foot" icon, too, so even Taco got it.
Re:Drinking to much funny-juice (Score:3, Informative)
He doesn't get British humor, clearly.
It's the Lorentz interval stupid (Score:1, Informative)
doug
TheStandUpPhysicist.com
Re:The e-mail I sent to the editor was ignored. (Score:3, Informative)
I agree. I ran across this in my searching on this guy: Einstein was dumb. ahahaha... AHAHAHA... ahahaha... [groupsrv.com] To quote: Now a whole new generation of notorious crackpots in high places have jumped in lunatic Godel's time travel banwagon. Examples are Kip "wormhole" Thorne, Stephen "black hole" Hawking, Brian "superstring" Greene, Michio Kaku (Mucho Kuckoo), etc... ahahaha... AHAHAHA... ahahaha...
I can deduce the following from this article:
- This guy does not have an advanced degree in Physics or Astronomy
- He watches too much Dexter's Laboratory
Time to call the nice men in the white coats with the truck with the padding in the back...Idiotic (Score:5, Informative)
Everyone agrees that practical time travel is at the very least exceptionally unlikely. But whether our model of the universe excludes the posibility of time travel is another matter entirely.
Note that even if our model of the universe allows for time travel it does not mean that time travel is possible. Not least because we know that our model of the universe cannot possibly be completely right. Quantum physics provides an excelent model of the universe at a large scale, relativity provides a good model at the cosmological scale. The problem is that the two models are incompatible. At leas one of our models must be wrong. Most likely they are both approximations.
The other issue that the writer does not seem to grasp is that the ability for matter to travel through time and the ability of information to travel through time are very different issues. For meaningful time travel it has to be possible for information to move backwards in time and not just matter. Otherwise what would come out the other end would be a random soup of quantum particles, not the time traveller. This is the problem with black hole time travel, the most that can come out the other side is a random soup.
The 'proof' provided by the author only demonstrates that he does not have the slightest understanding of the subject he is pontificating on. dt/dt = 0??? No, all that shows is that the dimensions of the two quantities are the same. Besides x/x = 1 in most algebras.
Re:Let's play: spot the Loony (Score:3, Informative)
While I am not particularly impressed by people mentioning their PhD either, the guy was completely correct. The Mach number IS dimensionless just like the Reynolds number, Nusselt number, Prandtl number,... whatever number. These numbers (mostly having to do with fluid dynamics) have exactly been devised to be dimensionless. The are invented to scale experiments. As long as the dimensionless number of your experiment and the real thing are the same (e.g. by making everything 10 times smaller but in 10 times lighter material and under higher pressure or so), conclusions about the relevant parameters will be unchanged. More info here [absoluteastronomy.com].
Re:Drinking to much funny-juice (Score:3, Informative)
Re:Drinking to much funny-juice (Score:3, Informative)
True, but according to the Lorentz Transformation, the one who goes the fastest gets there the youngest! So there is a winner.
Re:Drinking to much funny-juice (Score:3, Informative)
Re: Really? A tie? (Score:5, Informative)
The two frames are not inertial frames since one twin accelerates during the experiment. While the result is no doubt peculiar, there actually is no paradox to resolve.
You can read all about it here:
http://en.wikipedia.org/wiki/Twin_paradox
Proper time != Coordinate time (Score:2, Informative)
Haven't read the article thoroughly, but the author seems to confuse to concepts in Relativity:
The four-dimensional speed [wikipedia.org] is defined as d(t,x,y,z)/dtau, not d(t,x,y,z)/dt, so the first component is dt/dtau, not dt/dt = 1, as the author suggests
This mistake invalides the whole article.
Re:Of course time travel is possible! (Score:1, Informative)
Re: Really? A tie? (Score:3, Informative)
The passage of time varies with velocity and the presence of gravitation fields. You can actually measure the difference using atomic clocks. Both clocks will pass through the same points in time, but at different relative times. That is, when you bring the clocks back together you will find they have a discrepancy that is due to the difference in velocities and gravitational fields that they experienced while apart. This test has been done many times and the results are completely in agreement with General Relativity.
further reading (Score:2, Informative)
Differential Geometry (Score:2, Informative)
He claims (t,x(t),y(t),z(t)) is a 4-manifold, which is just not true. It's actually a 1-manifold embedded in 4-space. The whole point of writing "x of t" is to say that x is completely parameterized by t. So while this describes something that lives in 4-space (you could actually argue that it lives in 3-space since the dependence on t is trivial), it is completely parameterized by t. Think of a function in the plain - a set of points (x,y) such that y = f(x) (or vice-versa). While the function is embedded in 2-space it is only a 1-dimensional manifold: the entire point is that we can completely specify y in terms of x.
If we place that large restriction on our space, then it's no surprise that "dt/dt" (which is basically nonsense, but we'll assume he means the derivative of the identity function applied to t with respect to itself) is equal to 1, and that the dimensions are "seconds per second". What we really care about is the pull-back of the differential form through the t parameterization: dt + (dx/dt)*dt + (dy/dt)*dt + (dz/dt)*dt. Furthermore, this only makes sense if t lies in a connected region and is single-valued. So if we travel in time from t = now to t = future, then the differential fails to exist.
I thought he might just be goofing off, but if you look at the other crap on his website and his slashdot comments [slashdot.org], it seems this guy really is full of crap. It's scary that he's asking for money for this stuff.
Er am i the only one to notice that... (Score:4, Informative)
Nasa has done a lot of research on this. if you accelerate a physical object to the 'speed of light' it's 'relative' time stops in comparison to that of the universe, while time continues to flow for the rest of the universe, until that object is decelerated to normal velocity.
So if 'time' can't be traveled through, then what exactly is 'time dilation?' Also, black holes are only useful for traveling 'forward' in time, the 'intense gravity' within a black hole 'simulates' traveling forward at the speed of light, the closer you are the greater the gravity, and thus the greater the time dilation. no one has formulated or demonstrated the possibly to go 'to the past' although if 'gravity' and 'light speed travel' can decelerate ones own flow of time so the future can be reached, then 'anti-gravity' or some form of 'reverse momentum' might perhaps allow one to experience a pocket of time where as one progresses through it the entire universe grows 'younger' the problem with this is gravity and acceleration seem to both follow temeperature and have a common starting point or 'absolute zero' below which it is impossible to go.
appologies to all the great science fiction, but traveling back in time just isn't possible.* (unless of course one travels forward through time throught the end of the universe as we know it, until a new universe is created from the ashes of the old one, assuming that that Does in fact happen, and given the nature of atomic mass to develop in a consistant patter, one travels to the 'future' of a new 'third world inhabited by the evolutionary decendants of apes' before they manage to create time travel, and knowing exactly how the universe unfolds (because of a massive quantum computer and impressive algrythm that can determine the exact course of events Before they happen, again, based on the data it recieved while you were traveling 'forward' in time...) and thus influence the development of a primative world that the locals call 'earth' because everything formed along the same 'predestined' pattern based on the arrangment of molecules in the universe when it collapsed... only you went and went Forward in time, causing the end of the universe to happen differently than when it ended last time, so now you're ona world inhabited by 27 foot tall sentient lizards who think mamals are a tasty snack.
oops. well, you shouldn't have tried to avoid the big crunch to see how the universe would unfold the next time around
Re:Of course time travel is possible! (Score:1, Informative)
Re:Let's play: spot the Loony (Score:3, Informative)
Slashdot trolled by Usenet kook (Score:3, Informative)
Re:Let's play: spot the Loony (Score:1, Informative)
I'm not the original poster, but I would like to comment on this statement.
Units are an artificial construct of man. If we redefine our units, the universe itself doesn't change. We could measure speed in m/s, lightyears/fortnight, or furlongs/decade.
All these measuring units differ only by a fixed constant. However, they all represent the same thing, and the fundamental equations don't change when we switch from system to system.
In physics, it is perfectly natural (and common) to renormalize the values in the equations to be dimensionless. The dimensionless values are usually more important than the ones with dimension. Statements like "This value is large" and "This value is small" make a lot more sense after the normalization, because usually you just compare the number with one. Just like all other unit conversions, in practice this just another fixed constant to scale the values by.
To say that mach 1.25 is not a speed because it is unitless ("it is just a ratio") is just as disingenous as it is to say that 5 cm/millenium isn't a real speed because it isn't in m/s. In all cases they are just unit conversions; the underlying physics doesn't change. Switching to unitless scales is no different.
Re:Of course time travel is possible! (Score:1, Informative)
That's not time travel? It is to me.
CmdrTaco has been scammed by Usenet schizo (Score:4, Informative)
I'm sorry to have to tell you but you've been scammed by a well-known internet kook called Louis Savain into slashdotting his junk
If you google for "nothing moves in spacetime" and "rebelscience.org" you'll find lots of references to this particular paranoid schizophrenic (no, I'm not kidding)
He likes to spam sci.physics and sci.physics.relativity with his junk. One of his recent postings [google.co.uk] is fairly typical:
On Sun, 22 Jan 2006 16:59:17 +0000 (UTC),
glhan
>In article
>Traveler wrote:
>>On 22 Jan 2006 07:55:33 -0800, glhan
>>Repeat after me: NOTHING MOVES IN SPACETIME.
>World lines don't move in spacetime. When people talk about the motion of
>a particle they refer to a succession of points on the worldline, not the
>worldline in its entirety.
Repeat after me: ABSOLUTELY NOTHING MOVES IN SPACETIME!
NOTTHIINGGG!!!!
What this means is that there is NO CHANGE in spacetime (that's why it
was called Einstein's block universe by Karl Popper) and spacetime is
a fictitious math construct with no counterpart in reality. Now, isn't
it a tad weird that your idol Einstein agreed with his friend Kurt
"lunatic" Godel when he announced in 1949 that the spacetime of GR
allows time travel to the past via time-like loops?
Now hold on a southern cotton picking second! Aren't Kurt Godel and
Albert Einstein revered by physicists as two of the smartest men that
ever lived? Yep. ahahaha... One then wonders how they can be so stupid
as to believe in motion in spacetime. ahahaha...
http://www./ [www.] rebelscience.org/Crackpots/notorious.htm#Einstein
ahahaha...
>>> Or that your alien-induced lattice that exists nowhere is
>>>also an abstract model of your invention?
>>Nope. My lattice is not made of abstract crap but of real particles.
>>You crackpots call them virtual photons. ahahaha...
>You have a model that describes a lattice that is not made of abstract
>crap. You're like the screen writer who writes a line like "This isn't a
>movie, you know."
Maybe in your imagination but I know one thing: I am not an ass
kisser. I do my own thinking, than you very much. ahahaha... And
that's the way I like it. ahahaha... AHAHAHA... ahahaha...
Physics is so much phucking phun! ahahaha...
Louis Savain
Why Software Is Bad and What We Can Do to Fix It:
http://www.rebelscience.org/Cosas/Reliability.htm [rebelscience.org]
I would suggest you remove the story
Parent is right! Article is FOS (Score:3, Informative)
The article creator sould look into string theory-they are cruising at 11 (or 10) dimensions (haven't checked lately, may be out of date but definitely down from 26!) for spacetime, so it is quite possible for time to be a function of other dimensions (or be totally bypassed in one or more dimensions).
This is the kind of nonsensical reasoning that the NeoCon Nazis are using and that we were taught to avoid in elementary philosophy (logic course): remember proving 1 = 2?
Re:Idiotic (Score:2, Informative)
Being a math minor should be enough for you to know by now that "dt" is not "really tiny", "aproximately zero", or anything like that: it is not a number, nor a function nor anything.
The notation df/dt is simply a different way of writing "f'(t)" or "t |-> lim_{s\to t}(f(s)-f(t))/(s-t)" It is a very very good notation, because in lots of situations, it does behave like a fraction, and one can use it as a mnemonic tool (as in the rule dx/dt=dx/ds.ds/dt, and what not), but unless you understand that this kind of usage is only justified by the fact that there is a theorem which backs it, you have not understood anything. In particular, the pieces of the notation "df/dt" have no meaning when used by themselves (at least, at this level of calculus... there are things like exterior differentiation, the grassman calculus and what not; but those are a different game)
One usually sees people (in fact, this tends to be done by physicists...) using "dt" to stand for a "very small quantity", but that is just an heuristic way of doing things, and those reasonings are, formally, of no use; of course, the trained mind will know to limit itself to only use those reasonings that can be justified appropiately by real theorems. One can deduce a formula for the volume of a revolution solit using arguments that begin like "take an element of volume dV of height dh and...", but that is just heuristics.
Infinitesimals do not exist (in standard analysis...), only limit processes, in the same way that infinite sums do not make any sense, but limits of finite sums do.