Is it possible to travel through time ?

[y_raj]

Forget somewhere, what about somewhen? If time travel was even theoretically possible, why hasn't some future time traveler returned to visit us?

the reason is same as parallel universes, a body does not travel into its own past light cone but enters a new dimension totally. so one does not disturb his own past.

Or maybe we are the ones ahead of athers in time

[y_raj]

Not quite true, a scientist recently broke the FTL barrier, or the barrier never existed at all.


Speed of light broken with basic lab kit

* 10:03 16 September 2002
* NewScientist.com news service
* Charles Choi

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* Munday and Robertson, Applied Physics Letters
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Electric signals can be transmitted at least four times faster than the speed of light using only basic equipment that would be found in virtually any college science department.

Scientists have sent light signals at faster-than-light speeds over the distances of a few metres for the last two decades - but only with the aid of complicated, expensive equipment. Now physicists at Middle Tennessee State University have broken that speed limit over distances of nearly 120 metres, using off-the-shelf equipment costing just $500.

Jeremy Munday and Bill Robertson made a 120-metre-long cable by alternating six- to eight-metre-long lengths of two different kinds of coaxial cable, each with a different electrical impedance. They hooked this hybrid cable up to two signal generators, one of which broadcast a fast wave, the other a slow one. The waves interfere with each other to produce electric pulses, which can be watched using an oscilloscope.

Any pulse, whether electrical, light or sound, can be imagined as a group of tiny intermingled waves. The energy of this "group pulse" rises and falls over space, with a peak in the middle. The different electrical resistances in the hybrid cable cause the waves in the pulse's rear to reflect off each other, accelerating the pulse's peak forward.
Four billion km/h

By using the oscilloscope to trace the pulse's strength and speed, the researchers confirmed they sent the signal's peak tunnelling through the cable at more than four billion kilometres per hour.

"It really is basement science," Robertson said. The apparatus is so simple that Robertson once assembled the setup from scratch in 40 minutes.

http://www.newscientist.com/article.ns?id=dn2796

Granted this isn't very useful but neither was the Wright Flyer, where will we be in 100 years is anybodies guess.

oh , so this is the case with tachyons , but they aren't detected or proved yet, but reamin a hypothesis.
I would certainly like to know more about who proved it , or there was a fault in the equipment.. Moreover a tachyon said that it can directly travel in its own past does not appear to travelling in past but assumes its anti-particle characters, as stated by the theory.

[gamercube]

re

Gamercube Sir,no energy is lost even in radioactivity decay. As Antoinete Auguste Bouvoisier in c1700 observed"the atoms in matter are not lost,the stuff of the matter does not go away,nothing disappears"A certain Mr Einstein agreed and i dont think for one minute you or i can argue will Him. Agreed Sir with the theory that energy becomes mass and mass becomes energy(not absolute)Special t of Rel=mass and energy are the same# E=Mc2

Heh, please don't call me "Sir", I'm just an ordinary civilian, and I do not even deserve the title.

The mass of a particular radioactive substance changes with time, because the substance decays. For example, if you have a bit of radium, which you keep somewhere in a drawer, and then, after 2000 years, you open the drawer, you'll find out that the mass of radium has decreased by more than 50%. That is because the unstable atoms in radium emit atomic particles in the form of radiation, which is lost to the surroundings.

However, although the law of Conservation of mass by itself is not valid anymore, the Law of Conservation of Mass+Energy is still valid. The mass law had to be modified because of Einstein's equation E=mc^2. So, although the mass of radium is reduced to half its initial value in around 1600 years, the sum total of it's mass at that time plus the amount of equivalent mass emitted in the form of radiation will still be equal to the initial mass.

That's where the concept of half life comes from. Half life is the amount of time taken for a radioactive substance to decay to half its original mass.

[y_raj]

As many people believed a century ago that sound barrier cannot be broken, our present theories provide that we need extremely high energies to travel though time. many here have mistaken time dilation as time travel. Time dilation is a effect derived from special relativity which says that time runss different for two bodies in relative motion. but time travel is travelling back into time that has passed.
but since our modern theories are not very perfect, maybe we slowly in a century or so develop a new theory whic allows time travel in a different way.

anyways good luck.

[Sombra]

ok i'll refrase that, weight,just like a hot air baloon, or airship can have 0 bouyancy,and stay in the air , or negative bouyancy when it's lighter than air and goes up, so what if rocket weights 0 but due to arificial gravity field around it, or even negative weight, i'd say it'll definatly need much less fuel to take off and fly, we may not even need convential source of propulsion, i'm not saying it'll go faster than C, but .98C would be just as good.

Go into space, zero gravitiy = weight =0 still the mass is still there and energy is still needed to accelerate.

Still I like the idea of an artificial gravity field and its possible uses. Who knows? The day we really understand gravitiy in the form we did understand "electricity" with the Maxwell equotations perhaps we will be able to manipulate Gravity the same way some day.

[dave lukins]

Sombra.James Clark Maxwell and Faraday i think ,came to the same conclution that "the flow of electricity through a wire created a little magnatism therefore: magnatism creates electricity = pulses@670million mph,the speed of light, at a never ending loop"...this became the c in e=mc2

[neilmpenny]

Oh for cryin' out loud people! Time travel is cinch. All we need is a DeLorean and a little plutonium, which as everybody knows is available on every corner drugstore.

You are probably going to need a flux capacitor as well LOL

[neilmpenny]

What exactly would the point be in going back into the past? Sit idly by whilst the Japanese bomb Pearl Harbour? To be somewhere for the experience of being there?

Influence world history? Go back and take out Hitler for instance? Don't you think that if time travel were possible it would have been done so already?

Of course it may be interesting to speculate that the really nasty stuff could have been taken care of already and our future ancestors, relative to human existance in that future time, see what has transpired as our history is not worth altering.

[tankie]

What exactly would the point be in going back into the past? .

heh , read my post 146 ,and make yourself rich for your future , (or richer perhaps)

[highsea]

...That's where the concept of half life comes from. Half life is the amount of time taken for a radioactive substance to decay to half its original mass.

No. Half-life is the time it takes 1/2 of the radioactive isotope in a sample to decay to a stable isotope. In your example of Radium, the decay product is Radon. Radium has an atomic number of 88, Radon 86. So no way you are losing 50% of the sample mass. Even if you had 100% Ra226 in your sample, you would only lose 2 grams/mole in your 1600 years. e.g an 226 gram sample would decay to 224 grams. The sample would then consist of 50% Ra226 and 50% Rn222.

(edit to add: this is an oversimplification, because the isotopes would not be pure concentrations)

[neilmpenny]

heh , read my post 146 ,and make yourself rich for your future , (or richer perhaps)

Ok mate, will do. I got lazy and did not read all the posts as there is eight pages of them.

[tankie]

[QUOTE=tankie;323611

But, i think i will save all my old pennies for when i can go back in time and invest in some property and horse racing results ;)[/QUOTE]



here you are , saves you getting tired m8

[durtyburd]

Travelling back in time might be possible. But it would only move you back in time.

That is I get in my time machine, key in 22/11/63 and press go. I then arrive in 22/11/63. Unfortunately i am still in the same place i was in the universe, which is millions of kilometres away from Dallas at the time. Even if i press go on my time machine sitting in Dealey plaza tomorrow (15/5/05) Dealey Plaza isn't in the same place in the universe it was 42 years ago. since the Earth has moved a long way following the Sun, which has moved a long way itself. My time machine would be floating in space hundreds of billions of miles away from Dealey Plaza . At this point i wish i had upgraded my time machine to the "star drive" option so that i can get about in space - although i would have to use a relativistic speed to get to where Dealey Plaza was in '63. Even if i could adjust my course to allow for the time dilation to get there.

Which might be why we can't see travellers from the future. Because whilst they might be able to move in time. They still have the problem of moving through space which would then take time ....

I think.

Of course the other answer is to simply look for any blue Police 'phone box that has just appeared and ask the nice man inside to take you somewhen fun. It seems much easier in the Tardis :)

Greatest post...ever :D

Now that is an idea for space travel...no rocket boosters to overcome earth's gravity...just turn on your time machine and you'll end up millions of miles away where the earth was orbiting the sun years ago...or 10 minutes ago for that matter.

[neilmpenny]

here you are , saves you getting tired m8

Visions of Marty McFly with his almanac a la BTTF 2

[Militarythinker]

If we eventually invent time travel, where are all the people from the future?