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No Time Travel, Sorry
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."
This guy is a pseudo-scientific moonbat. Please don't waste your time with the not-so-FA.
Helium balloons want to be free.
Discounting the obvious fact that each and every one of us are traveling into the future at one second per second, time travel into the future is a proven fact-- if you define "time travel" the right way. That is, if you define "time travel" as "moving at some velocity significantly different from one second per second through time", rather than "instantly POOFing from one time to another", "time travel" forwards is as simple as traveling at high relativistic speeds.
With spending like this, exactly what are "conservatives" conserving?
"Didja see the foot?"
He doesn't get British humor, clearly.
The relativistic 4-velocity is not (1, dx/dt, dy/dt, dz/dt) as claimed by the web page author, but it is instead (dt/dgamma, dx/dgamma, dy/dgamma, dz/dgamma), where gamma is definted as the Lorentz invariant interval: gamma^2 = 1/(1 - v.v/c^2). This page gets attention because he bitch-slaps big names, but his basic math claim gets him an F in any undergrad special relativity class.
doug
TheStandUpPhysicist.com
Working on new views of old physics at http://VisualPhysics.org
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.
Looking for an Information Security student project suggestion?
Try http://dotcrimeManifesto.com/
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.
The past, future and present are convenient terms used to describe an event's occurence as viewed by a particular observer. Two observers moving at very different speed will observe the same event at different times. what will be one observer's "present" may well be another observer's "past". All three are equallly meaningless in terms of physics.
Your pizza just the way you ought to have it.
True, but according to the Lorentz Transformation, the one who goes the fastest gets there the youngest! So there is a winner.
Mouse over the foot (on appropriate browsers) and you get a popup label saying "It's funny. Laugh."
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
No. You misunderstand the twin paradox: the twin that journeys will age less than the twin that stays behind in the classic "paradox".
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
Life is short: void the warranty.
Haven't read the article thoroughly, but the author seems to confuse to concepts in Relativity:
The four-dimensional speed 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.
There is no way that Laura "Pickles" Bush is going to be nominated for the 2008 election.
No: we actually travel through time at slightly different rates all the, er, time. We just don't notice it because the effect is so small under normal conditions.
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.
Life is short: void the warranty.
I too cannot tell if this link is serious. If you want to read a good explanation of the current understanding of time, check out Brian Greene's article "The Time We Thought We Knew" from the 1/1/2004 edition of the New York Times. (note: if you don't want to pay for it from the Times, you can get to it through your local library's website under their public databases, if you have a library card/account.) Greene says, "catapulting yourself forward in time is beyond what we can now achieve, but scientists routinely use high-energy accelerators to propel particles, like electrons and protons, to nearly the speed of light, slowing their internal clocks and thereby sending them to the future. Though unfamiliar, forward time-travel is an unavoidable feature of relativistic reality." He goes on to explain what time is and ends by saying, "And in moments of loss I've taken comfort from the knowledge that all events exist eternally in the expanse of space and time, with the partition into past, present and future being a useful but subjective organization."
This dude clearly has no idea what he's talking about. Especially when it comes to differential geometry, which is paramount to the theory of general relativity.
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, it seems this guy really is full of crap. It's scary that he's asking for money for this stuff.
m0nstr42.blogspot.com
time dilation can be reproducably created, and in fact occurs on a daily basis, to a slight extent every time someone flies an airplane, or is launched into orbit aboard a space vehicle. technically just 'walking' will create a small bit of 'time dilation' it might be impossibly small to try and detect, or course.
;)
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
https://www.gnu.org/philosophy/free-sw.html
Technically true, but time is relative (remember Einstein?) and really the 'temporal velocity' you would measure would be dt'/dt (passage of local time relative to, say you great-grandfathers time frame.). These guys really are crackpots :P. Just thought I would clear that up for those more gullible ./-ers .
Your Mach = (Your speed)/(Speed of sound) = (x1 m/s) / (x2 m/s) = x1/x2 => no units.
====
Crudely Drawn Games
Try a Google search for "nothing moves in spacetime".
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.
The parent is correct - time travel is possible - into the future anyway. That's what Einstein's theory of relativity says - as you approach the speed of light time slows down. So, travel fast enough, and you may experience only one hour while 100 years go by on earth.
That's not time travel? It is to me.
Dear Rob
...@steel.ucs.indiana.edu (Gregory L. Hansen) wrote: , ...@indiana.edu wrote:
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 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./ 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
I would suggest you remove the story
Tubby or not tubby. Fat is the question
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?
Supreme Granter of Doctor of Obviology Letters ("A FIRM Command of the Obvious")