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#21 shadowspy

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Posted 20 September 2004 - 02:59 AM

Theoretically speaking, Time travel is both possible and impossible, using Einstein Theory of Relativity, E=mc2.

It is possible, because time slows down when speed approaches the speed of light, and if faster than light speed is achieved, we can travel backwards in time. Only one future time travel is possible, and that what's we're doing now.

It is impossible, since mass is converted to energy as it approaches the speed of light. This is irreversible. Matter can be converted to energy almost instantaneously, but converting energy to matter is a different story altogether. If an object achieved light speed, it has become light energy. Converting it back into matter will require "devolving" it, and that is a complicated process I can't even try to explain (nakalimutan ko na kung papaano, but it's still in my head somewhere).

Also, with those things considered, NOTHING travels faster than light.

Except probably, the speed of thought. (Think you're in Andromeda and you're there).

theoretically, E=mc^2 does not gove you a formula for time travel. Theory of Relativity (General and Special) requires 4-vectors and tensors and only from their mathematics can one "theorize about time travel" In addition, matter and energy can be converted to and fro. An example of this process is pair production and annihilation. In production, light , near the presence of an atom can produce an electron positron pair. On the other hand, annihilation involves the production of 2 photons from an electron and positron pair. Also, theoretically, there are particles which travels faster than light. These particles are called tachyons.

In addition to time travel, scientists (that's us!) are probing the idea of a multiverse. These multiverses exists simultaneously and can be found beyond the Hubble Dimension of our Universe.

By the way, these things are ourely theoretical. no concrete evidence of these things exists (Well, except for E=mc^2 probably, which is the way our Sun produces its energy).

Just to enlighten you guys...

#22 shadowspy

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Posted 20 September 2004 - 03:07 AM

With the current theories and laws of Physics, time travel is impossible.

Think about the 3 Laws of Thermodynamics.
1 Mass-Energy can not be created or destroyed
2 Conservation of Mass-Energy
3 Entropy would increase as time goes forward.

Classic time travel would involve moving mass from the present and take it into the past or the future.

Time travel in the past would, in effect, destroy mass in the present and create mass in the past. Violates all three Laws of thermodynamics.

Your first two laws are contradicting. In any case, these are not the lawas of thermodynamics. Conservation of mass- energy (note that they are combined as one term) inplies that one can create mass if one destroys energy and vice versa. This is the way the sun produces energy through hydrogen fusion. Conservation of Energy and Conservation of Mass (separate) is valid only for low energy processes (such as chemical reactions). For high energy processes (nulcear fusion etc.) the governing law is conservation of mass-energy.

In simple terms the for laws of thermodynamics state
Zeroth Law - gives the definition of thermal equilibrium and allow sthe construction of a thermometer
First Law - a restatement of the conservation of energy
Second Law - entropy is increasing; heat flows spontaneously from hot to cold
Third Law- it is impossible to reach absolute zero in a finite number of reversible processes.

#23 shadowspy

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Posted 20 September 2004 - 03:14 AM

If one goes to velocities close to the speed of light, one is not actually "catching up" with the photons. The fundamental postulate of the special theory of relativity states that the velocity of light is the same for all observers imply that even though your speed is close to the speed of light, you will still measure it as c. it's not like you're just going to subtract your velocity with the spped of light. so independent of the reference frame you are in, the speed of light remains the same.

i just want to clarify erroneous things perpetuated by science fiction writers. As a physicist, I (actually we as most physicists have this reaction) get pissed of when I hear erroneous things. Blame it on the science fiction writer.

incidentally, star trak has some fairly accurate physics concepts.

#24 shadowspy

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Posted 20 September 2004 - 03:20 AM

just to set things straight, these are the things that happens when one travels close (but does not reach) the speed of light.

1) Time dilation - the time for someone travelling close to the speed of light becomes dilated for someone who is at rest.

2) Length Contraction - things become shorter along the direction of motion

3) Mass Increase - as one goes closer to the speed of light, the mass of the object becomes heavier. this poses the major engineering problem for those "designing" a time travel machine or any machine ti travel faster than light. As you go faster, your mass increases, which means you need more energy to propel it. This increases the speed which increases the mass which increases the energy requirement ad infinitum.

Take note that we are talking hear about the velocity of light IN VACUUM. Technically, an object passing through a medium can exceed the speed of light in that medium as the speed of light in a medium is given by v=c/n where n is the refractive index of the medium (i.e. water). For water, n = 1.33 . You do the math. If objects travel faster than the speed of light in a medium, it emits a light in a mechanism known as Cerenkov effect. This is similat to a sonic boom when one crosses the sound barrier.

#25 orionpax

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Posted 20 September 2004 - 10:13 AM

For now...its impossible...current propulsion systems can only provide existing spacecraft with just enough lift (though more to spare)to get out of the atmosphere......as stated in the previous posts...no machine or man for that matter can travel even near the speed of light....(unless you are the Flash or Superman :lol: )...the most is Mach 4-5 on earth and a bit faster in the gravity less outer space, and increases exponentially (like what are propelling Voyagers 1 & 2)...the future propulsion systems involve ionic plates...but basing it on the laws of physics...its still impossible...:)

#26 shadowspy

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Posted 20 September 2004 - 11:09 AM

If I am not mistaken, the record is Mach 15.

#27 orionpax

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Posted 20 September 2004 - 11:14 AM

If I am not mistaken, the record is Mach 15.

I stand corrected.. :lol: my mind got stuck in the Airwolf era :D

#28 Rex Steele

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Posted 20 September 2004 - 09:40 PM

It can't happen. . . otherwise, we'd have encountered a time travelling tourist by now.

#29 mrwc

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Posted 29 September 2004 - 07:17 PM

If you see yourself in the past, can you touch yourself? I saw an action movie wherein the villian died after touching his past self.

#30 Joblow

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Posted 07 October 2004 - 08:46 AM

Mukhang sa movie ng Time Cop ito.

If you see yourself in the past, can you touch yourself? I saw an action movie wherein the villian died after touching his past self.

<{POST_SNAPBACK}>



#31 ba_to

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Posted 07 October 2004 - 07:16 PM

kung maging possible man.. dapat di siya mapunta sa mga masamang kamay

#32 draco456

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Posted 08 October 2004 - 12:36 AM

ok dito ha. may free physics lessons. :)

#33 dyakhardy

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Posted 16 October 2004 - 07:38 PM

gusto ko balikan ang jurassic era... gusto ko makita kung totoo ang depiction ng dinosaurs, especially the skin colors

#34 dyakhardy

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Posted 16 October 2004 - 07:39 PM

gusto ko rin balikan nung panahon ni Lapu-Lapu, bibigyan ko sya ng maraming baril at bala para maiba ang course ng history ng bayang mahal...

#35 Jhonnyjhon

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Posted 22 October 2004 - 07:25 PM

kung meron akong time machine, babalikan ko ung time na bata pa ako.. bibigyan ko siya ng tips para gumanda ang buhay niya in the future

#36 Jhonnyjhon

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Posted 22 October 2004 - 07:34 PM

babalikan ko rin ung time ni Rizal.. tuturun ko cya mag e-mail para maka chat niya sila aguinaldo... haha

#37 cyberpinoy1973

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Posted 27 October 2004 - 05:49 PM

If time travel were possible, what would time be like?

If we go back in time and change something at some point, will it also change the future like inthe movie "Back to the Future"? In other words, are there different possibilities for time as we know it?

Or is it like in the movie "Time Machine" where the protagonist said, "I can go back a thousand times and see will die a thousand deaths"? In other words, that there is only one possibility for time as we know it and that we cannot change the future by changing the past?

But if I could travel in time, I would like to see how life began on earth and how it will end. Of course, I would also like to be able to go back to the present.

:)

#38 c0mpass

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Posted 27 October 2004 - 08:09 PM

i believe in the possibility of travelling through time. what interests me more is not the idea of travelling but the laws which defines how it is possible while everything else remains harmonious.

:D

#39 robo_cop

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Posted 30 October 2004 - 06:37 AM

maganda to, para maitama ang mga maling nagawa

#40 marc.alan

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Posted 07 November 2004 - 02:30 AM

this is cool!!!

supernatural and the occult ang topics pero ito scientific!! physics abound!!

anyway, guys, di ba we are constatly time travelling?? travelling to the future constantly di ba??

i heard in a movie that there is no such thing as present... kasi if you say "what is the time now?" then the instant you asked for the time, that was already past... (tama di ba? im making sense right?)

anyway, you only talk about moving forward and backward in time...

what about moving sideways??? parallel dimensions a la sliders! (anybody remember that TV show??) and jet li's "the ONE"

one more thing, if you go to the future, then is it safe to assume that you wont see yourself in that future (unlike back to the future, michael j fox saw himself in the future)well, this is because you shouldnt exixt kase wala ka sa past, nasa future ka, di ba? nawala ka sa past you wnt to the future, so sa future na pinuntahan mo, wala ka dapat doon... (makes sense ba?)

hmmmm....

anyway, shadowspy, thanks for commenting on the science of star trek.. even though its science fiction, they have physics consultans who edit the script and try to make the terms more realistic (at least, thats what the books on trek say)

... see yah!





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