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Impossible. To travel back in time one'd have to go at speeds faster than light - nothing is faster than light (and can you imagine the mass of an object that would need to travel that fast?). It's a nice thought, but impossible all the same.

Tarzan Boy
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whether its is ever invented or not, it would be totally cool.  I would do like they did in "Back to the Future II" when Biff Tannen got all the sports stats in the almanac and became a billionaire.  Now THAT would be cool.  I would also like to go back and buy up a bunch of stocks of companies that were just starting out and are huge corporations today(Wal-Mart, Microsoft, etc).  Lastly, I think I would gather some of the most advanced products we use today and take them back to 1985, such as a 2.4 Ghz computer of today, and show them what is to come in the future.  If you would have told me in 1985 that in 2002 we would have 2.4+ Ghz computers with 60 GB hard drives etc, I would have called you crazy!
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As cool as all that would be, that is exactly why if time travel is ever accomplished it would be a closely guarded secret. The accomplishment of such technology would probably only be publicly shared after a system has been invented and tested to regulate it. This regulation would prevent people from making the kinds of changes that you spoke of, changes that would change History as a whole and/or cause criminal impact. IMO, they would probably allow a person to go back and do relatively smaller scale things like make amends with family or prevent accidental deaths or suicides of loved ones and then be monitored through the process. Hey, I'd be happy to be able to do just that, actually.

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settle down now.  Geesh, it's not worth arguing over!End Quote

We're not arguing, silly.  ;)  This topic's a little more interesting than I'd first imagined!  

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For all we know, they might have already invented a time machine and we may never know about it.
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I agree it's a feasible possibility - the "we may never know about it" part. Hey, there's still a lot out there we don't know and perhaps never will. Aliens? Conspiracies? Who knows? Someone sure does. Hmmm...  ;)

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compared to today, the 1980s was great.  99% of my best times were during the 80s.  Don't get me started on how the 90s and 00s suck.  Frankly, I don't have the energy.  LOL
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Same here, man.  ::) :P

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I'm usually not too serious here, but I recently did some study of Einstein's physics because I was curious about the possibility of things like time travel and teleportation, so this is my first time to really expound ( :) ) on my discoveries. I'm no expert, but this is my understanding:

So much of time travel talk uses elements from Einstein's Theory of Relativity for support, such as "the speed of light", yet the elements are often not consistent with a true understanding of the theory.

First, the Theory of Relativity does not consider time an actual thing or path that can be traveled, but simply the relation of one process to another. For example, we measure the typical life span of a human by the number of times the Earth travels around the Sun during an average person's life. We use this same standard for keeping track of historical events. Things happen in a certain order, processes happen at a certain pace relative to other processes, and we as humans recognize this concept as "time."

The Relativity Theory proposed a number of factors that seemed to affect the speed of atomic processes (or aging processes in living things) and one of those factors was velocity. Therefore, it was determined that the closer something traveled at the speed of light (assuming the speed of light was the fastest speed something could travel) the slower its processes would go. For example, if a spacecraft full of astronauts darted into space near the speed of light and returned to Earth 30 years later, the physical and mental processes of everyone and everything inside the spacecraft would slow down to almost no change. However, everyone on Earth would have continued to age at the normal rate and would now be 30 years older than the astronauts who would have seemed not to age at all.

The important point here is that the spacecraft did not "travel in time" any more than the people on Earth did. The Earth traveled around the Sun 30 times as the astronauts traveled through space at near the speed of light. It's just that, one, their physical processes slowed down to the point that they barely aged, and two, their mental processes slowed down proportionally so that, to them, the 30-year flight seemed a mere fraction of a second.

Another misunderstanding of Relativity is evident when someone says "if you could travel faster than the speed of light you could go back in time." Relativity simply uses "the speed of light" as a standard to measure the maximum speed something can travel. When it is said that "if a person could travel at the speed of light, that person would experience no passage of time" it is the same as saying "if a person could travel as fast as anything could possible travel, that person would experience no passage of time." If we discover something that can travel faster than the speed of light, then that thing would become the new standard for "as fast as anything could possibly travel."

In short, the Theory of Relativity does not support any kind of going forward or backward in "time." It may be, as a few here have said, that new science may be discovered that allows this, such as time warps or whatever. But it would be exactly that, new science, and not supported by Einsteinian physics, and so would very likely have little to do with the elements of Relativity like "the speed of light."

And now back to your regularly scheduled 80s reminiscing...  :)
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Thanks Pell! I enjoyed your post.  :)

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Thanks Pell! I enjoyed your post.  :)
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You are most welcome. :)

Actually, I would like to go back and live a few days like an episode of "Do Over" where I am a teen in the 80s again, but I would know what I know now. But I don't think I'd want to permanently change any of my history, and I'd like to be able to come back to the present and still be the same.

Maybe I'll dream it.

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So... if a ship is traveling at 70 mph and it shoots a cannon with a muzzle velocity of 100 mph the cannonball travels at 170 mph... right?  

What happens if we shoot that cannon off a ship traveling 1/4 mph slower than the speed of light?
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Usually, the question is "If the spaceship travelling at the speed of light turned on its headlights, would the astronauts see the headlights in front of the ship? And, if so, would the light of the headlights be traveling faster than the speed of light?"

The answer is that the ship could not cause anything to travel faster than the speed of light, but I'll have to go back and check the reason why. There are a lot of factors including gravity, the curvature of space, and the mass of the spaceship, which would be tremendous when traveling at the speed of light (remember: e=m c(squared) or energy = mass times speed of light squared. The faster something travels, the more energy involved, and therefore, the more mass involved).

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Usually, the question is "If the spaceship travelling at the speed of light turned on its headlights, would the astronauts see the headlights in front of the ship? And, if so, would the light of the headlights be traveling faster than the speed of light?"

The answer is that the ship could not cause anything to travel faster than the speed of light, but I'll have to go back and check the reason why. There are a lot of factors including gravity, the curvature of space, and the mass of the spaceship, which would be tremendous when traveling at the speed of light (remember: e=m c(squared) or energy = mass times speed of light squared. The faster something travels, the more energy involved, and therefore, the more mass involved).
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Here's a Web Site that answers the "headlights" question in simpler terms than I could without delving back into all that again. I was mostly paying attention to the time-travel aspects (or lack thereof) of Relativity.

http://www.heathers.net/paradox1.html


By the way, Steve, I like your Avatar. I used to watch Ambrose on PBS. I wish I could have taken a history class with him at the University of New Orleans before he died. He was obviously very passionate about what he taught.

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Have you read Richard Feynman's Surely You're Joking, Mr. Feynman.  A very good read.  If you're interested in science, a must read.  

Here's another poser: Is small infinite?   I'm familiar with Planck's length (and understand it from a photon's frame of reference), but can't anything be shorter than Planck's length?  Does small expand inward indefintely?
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I haven't read Feynman, but I've browsed his books and I like what I've seen on TV, so I may get around to reading it one of these days.

My knowledge of physics is very limited, but I tend to believe that "infinite small/large/distance/speed" are theoretical concepts that do not exist in the physical world. I would imagine that there are limits to how many pieces a real object can be broken into.

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We know many have seen the "Back To The Future" series.

Has anyone seen "Time Cop"? What did you think?
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Was that the one with Sylvester Stallone and Wesley Snipes?

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Was that the one with Sylvester Stallone and Wesley Snipes?
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Nah, that was "Demilition Man". I did like that one very much.

"Timecop" (correctly typed ;D) 1994

Plot Summary:
 
The perfection of time travel brings with it new opportunities for criminals. The government sets up a special police force (T.E.C.) to ensure the new technology isn't abused. Max Walker, one of these timecops learns of a corrupt politician's plot to become president using the device. Senator McComb discovers Walker on his trail and the real action begins--in Walker's own past!

Cast:
 
Jean-Claude Van Damme - Walker
Mia Sara - Melissa
Ron Silver - McComb
Bruce McGill - Matuzak
Gloria Reuben - Fielding

Quoting:
Hasn't R&RF already got one ?  ;)
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Yep...at the moment I am in 1982, and Rockin' :D

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My knowledge of physics is very limited, but I tend to believe that "infinite small/large/distance/speed" are theoretical concepts that do not exist in the physical world. I would imagine that there are limits to how many pieces a real object can be broken into.
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Science had to be easier before Einstein.  Had to be.

Time and space is baffling.  For instance, can a black hole change time?  This is what they say at http://image.gsfc.nasa.gov/poetry/ask/a11568.html...

Now, if you study what happens to the Kruskal-Szekeres coordinate system as you pass inside the black hole event horizon, nothing unusual happens, but in the conventional newtonian (x,y,z,t) system, if you look at the formula for the so-called 'metric' you see that the space and time parts reverse themselves. This means that just inside the horizon, space becomes time-like and time becomes space-like. What we call time does change to something with the mathematical properties we have normally associated with space.

This sounds pretty bizarre, but considering that we are using a non-proper coordinate system in the first place, I would not put much stock in how to physically interpret it. It is possible that time changes somehow inside a black hole, but that is an experiment we will never be able to test because we can never receive information from inside a black hole. Because (x,y,z,t) is a 'bad' coodinate system in the first place for describing black hole geometry, I do not feel compelled to ask it to make too many predictions.



Here's another link to a site talking about black holes and time travel:
http://www.popsci.com/popsci/science/article/0,12543,211498,00.html

Quoting:


Science had to be easier before Einstein.  Had to be.

Time and space is baffling.  For instance, can a black hole change time?  This is what they say at http://image.gsfc.nasa.gov/poetry/ask/a11568.html...

Now, if you study what happens to the Kruskal-Szekeres coordinate system as you pass inside the black hole event horizon, nothing unusual happens, but in the conventional newtonian (x,y,z,t) system, if you look at the formula for the so-called 'metric' you see that the space and time parts reverse themselves. This means that just inside the horizon, space becomes time-like and time becomes space-like. What we call time does change to something with the mathematical properties we have normally associated with space.

This sounds pretty bizarre, but considering that we are using a non-proper coordinate system in the first place, I would not put much stock in how to physically interpret it. It is possible that time changes somehow inside a black hole, but that is an experiment we will never be able to test because we can never receive information from inside a black hole. Because (x,y,z,t) is a 'bad' coodinate system in the first place for describing black hole geometry, I do not feel compelled to ask it to make too many predictions.



Here's another link to a site talking about black holes and time travel:
http://www.popsci.com/popsci/science/article/0,12543,211498,00.html
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I am re-reading Nigel Calder's "Einstein's Universe", a very simple, everyday explanation of Einstein's Theory of Relativity as far as it was understood as of 1979. I recommend it if you can find it. I got mine in a used bookstore for two dollars. I'm not sure if it's still in print.

I want to get a firm understanding of Relativity before I look into more modern theories like quantum physics.

Quoting:


I am re-reading Nigel Calder's "Einstein's Universe", a very simple, everyday explanation of Einstein's Theory of Relativity as far as it was understood as of 1979. I recommend it if you can find it. I got mine in a used bookstore for two dollars. I'm not sure if it's still in print.

I want to get a firm understanding of Relativity before I look into more modern theories like quantum physics.
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Thanks, Pell, I'll look for it.  I've read The Idiot's Guide to the Theories of the Universe.  It was pretty slick going till it got to... quantum physics.  Nanotechnology intrigues me because of the gumdrops... developing fabric that cleans and self-repairs rips and tears; computer chips made out of pure diamonds.  Cool stuff, but I'd like to understand the math.  I'm beginning to think very few people understand quantum mechanics -- scientists tend to fight like junkyard dogs.  I might not understand what they're talking about, but the venom comes through.

Before we know it we'll all live to be 150, cars will be made out of rice paper and peace will rule the planets.  

Quoting:
maybe nothing can go faster than the speed of light...YET.  Maybe they will invent something that CAN go faster, thus providing the missing component to the wonders of time travel.  Oh yea, they'll also need a Flux Capaciter.  LOL
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I hope they also make it with a DeLorean and a Mr. Fusion :)

Quoting:
It is a nice thought, but rationally it is not going happen. Where are these time travelers from the future now?  On the other hand, I have heard it is possible to travel into the future, however there would be no way to get back.  
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Maybe UFO's are actually travellers from the future, and not from other planets..?

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Don't you guys think! This may sound crazy but I just had to make a topic about this. Do you suppose one day way in the future someone might make a time machine. If that happens that person will become rich and famous. You guys that want to go back to the 80s and 90s can get your wish. No, I think someone can make a time machine that change the time instead someone going to the future or back in time. Set the time back to January 1, 1980 but I want be around until the end of 1985. Oh well.

What do you guys think.
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Hey, It could happen. Why not. My opinion is that maybe we will not be able to go back in time, like in Back to the Future, but somehow get to places at a much faster amount of time.  

Quoting:
I'd like the idea of someone building a time machine so I could see what I actually look like 20 years from now.If I have kids,marriage,house,money,etc..... -howard-
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I love my family but, I would prefer to turn "Back" the clock 20 years and maybe do things a bit better than I have ;)

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I love my family but, I would prefer to turn "Back" the clock 20 years and maybe do things a bit better than I have ;)
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What he said.  

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Imagine what it would be like to prevent the assassination of JFK or Abraham Lincoln?
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or Martin Luther King...


Howard

Quoting:Imagine what it would be like to prevent the assassination of JFK or Abraham Lincoln?

or Martin Luther King...
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We would all like to think that going back in time and saving these great leaders would vastly improve the lot of mankind today.  However, a big time pessimist like me knows altering such momentous historical events would set off a chain reaction leading to EVEN WORSE SH*T down the road!!! :o

Quoting:
Nothing can travel at the speed of light. Therefore an event cannot be finished before it is started. If you can offer a real argument against proven physical theory and facts, I'd like to see what dissertation you wrote and if you are going to be the next Einstein ::)
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http://www.cnn.com/2000/TECH/space/07/20/speed.of.light.ap/

http://www.angelfire.com/zine/dailytravesty/98.html

Quoting:

http://www.cnn.com/2000/TECH/space/07/20/speed.of.light.ap/

http://www.angelfire.com/zine/dailytravesty/98.html


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And notice how it was a pulse of laser that traveled that fast.

Quoting:
"This effect cannot be used to send information back in time," said Lijun Wang, a researcher with the private NEC Institute.End Quote

No "thing" was sent back in time... it was a pulse of laser: particle-waves. No thing can travel beyond the speed of light. You'd have to be light yourself to travel that fast. Also, the event did not finish before it started - which is what this discussion is about. The CNN article also states that the experiment did not break Eistein's Theory of Relativity.

Nice try ;)

Quoting:
If they invented a time machine,maybe my brother would've still been alive and prevented himself from dying,just take his insulin cause he was a diabetic. :(


Howard
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Sorry to hear about your brother. :'(
So he didn't know he was diabetic?  
I know a guy who's diabetic and is having some of his toes amputated because his circulation is going.  He may also have to go on dialysis.  His heart is also going bad (hence the circulatory troubles).  The guy is still a chain smoker, which doesn't help.  Not a happy camper!

Quoting:
the 80's were great but i wouldn't want to give up my life that i have now. If you go back in time to do stuff differently
you would not be the same as you are today. My children are no.1 in my life and I wouldn't chance going back and changing anything because a world without them is not one i would want to live in. even the bad stuff that has happened to us, has shaped who we are today.
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I would kill to go back to the age of 12 knowing what I know now, 'coz boy oh boy did I ever f**k it up!! ;D

Quoting:

Sorry to hear about your brother. :'(
So he didn't know he was diabetic?  
I know a guy who's diabetic and is having some of his toes amputated because his circulation is going.  He may also have to go on dialysis.  His heart is also going bad (hence the circulatory troubles).  The guy is still a chain smoker, which doesn't help.  Not a happy camper!
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He knew he was a diabetic.He just forgotten on occasions to take his insulin.Thanks for caring,Max. :)

Howard