Physicists: Sorry, you can't travel back in time

[Queasy]

Link

The urge to hug a departed loved one again or prevent atrocities are among the compelling reasons that keep the notion of time travel alive in the minds of many.

While the idea makes for great fiction, some scientists now say traveling to the past is impossible.

There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller "The Elegant Universe" and a physicist at Columbia University.

"And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it," he said. "Most of us think that almost all of them can be ruled out."

The fourth dimension

In physics, time is described as a dimension much like length, width and height.

When you travel from your house to the grocery store, you're traveling through a direction in space, making headway in all the spatial dimensions ? length, width and height.

But you're also traveling forward in time, the fourth dimension.

"Space and time are tangled together in a sort of a four-dimensional fabric called space-time," said Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book "One Universe: At Home In The Cosmos."

Space-time, Liu explains, can be thought of as a piece of spandex with four dimensions.

"When something that has mass ? you and I, an object, a planet or any star ? sits in that piece of four-dimensional spandex, it causes it to create a dimple," he said. "That dimple is a manifestation of space-time bending to accommodate this mass."

The bending of space-time causes objects to move on a curved path, and that curvature of space is what we know as gravity.

Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn't share this multi-directional freedom.

"In this four-dimensional space-time, you're only able to move forward in time," Liu told LiveScience.

Tunneling to the past

A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole ? a hypothetical tunnel connecting two regions of space-time.

The regions bridged could be two completely different universes or two parts of one universe. Matter can travel through either mouth of the wormhole to reach a destination on the other side.

"Wormholes are the future, wormholes are the past," said Michio Kaku, author of "Hyperspace" and "Parallel Worlds" and a physicist at the City University of New York. "But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today's technology."

To punch a hole into the fabric of space-time, Kaku explained, would require the energy of a star or negative energy, an exotic entity with an energy of less than nothing.

Greene, an expert on string theory ? which views matter in a minimum of 10 dimensions and tries to bridge the gap between particle physics and nature's fundamental forces, questioned this scenario.

"Many people who study the subject doubt that that approach has any chance of working," Greene said in an interview . "But the basic idea if you're very, very optimistic is that if you fiddle with the wormhole openings, you can make it not only a shortcut from a point in space to another point in space, but a shortcut from one moment in time to another moment in time."

Cosmic strings

Another popular theory for potential time travelers involves something called cosmic strings ? narrow tubes of energy stretched across the entire length of the ever-expanding universe.

These skinny regions, leftover from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.

Cosmic strings are either infinite or they're in loops, with no ends, said J. Richard Gott, author of "Time Travel in Einstein's Universe" and an astrophysicist at Princeton University. "So they are either like spaghetti or Spaghetti-O's."

The approach of two such strings parallel to each other, said Gott, will bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory.

"This is a project that a super-civilization might attempt," Gott told LiveScience. "It's far beyond what we can do. We're a civilization that's not even controlling the energy resources of our planet."

Impossible, for now

Mathematically, you can certainly say something is traveling to the past, Liu said.

"But it is not possible for you and me to travel backward in time," he said.

However, some scientists believe that traveling to the past is, in fact, theoretically possible, though impractical.

Maybe if there were a theory of everything, one could solve all of Einstein's equations through a wormhole, and see whether time travel is really possible, Kaku said.

"But that would require a technology far more advanced than anything we can muster," he said. "Don't expect any young inventor to announce tomorrow in a press release that he or she has invented a time machine in their basement."

For now, the only definitive part of travel in the fourth dimension is that we're stepping further into the future with each passing moment.

So for those hoping to see Earth a million years from now, scientists have good news.

"If you want to know what the Earth is like one million years from now, I'll tell you how to do that," said Greene, a consultant for "Déjà Vu," a recent movie that dealt with time travel. "Build a spaceship. Go near the speed of light for a length of time ? that I could calculate. Come back to Earth, and when you step out of your ship you will have aged perhaps one year while the Earth would have aged one million years. You would have traveled to Earth's future."

 

[theGlove]

obviously this guy never heard of the flux capacitor

 

[JS80]

can't you theoretically SEE into the past though?

 

[slpaulson]

Originally posted by: JS80
can't you theoretically SEE into the past though?

You see into the past when you look at the stars...

 

[silverpig]

Originally posted by: theGlove

obviously this guy never heard of the flux capacitor

I actually know how that term was coined

 

[pontifex]

Originally posted by: Queasy
Link

The urge to hug a departed loved one again or prevent atrocities are among the compelling reasons that keep the notion of time travel alive in the minds of many.

While the idea makes for great fiction, some scientists now say traveling to the past is impossible.

There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller "The Elegant Universe" and a physicist at Columbia University.

"And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it," he said. "Most of us think that almost all of them can be ruled out."

The fourth dimension

In physics, time is described as a dimension much like length, width and height.

When you travel from your house to the grocery store, you're traveling through a direction in space, making headway in all the spatial dimensions ? length, width and height.

But you're also traveling forward in time, the fourth dimension.

"Space and time are tangled together in a sort of a four-dimensional fabric called space-time," said Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book "One Universe: At Home In The Cosmos."

Space-time, Liu explains, can be thought of as a piece of spandex with four dimensions.

"When something that has mass ? you and I, an object, a planet or any star ? sits in that piece of four-dimensional spandex, it causes it to create a dimple," he said. "That dimple is a manifestation of space-time bending to accommodate this mass."

The bending of space-time causes objects to move on a curved path, and that curvature of space is what we know as gravity.

Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn't share this multi-directional freedom.

"In this four-dimensional space-time, you're only able to move forward in time," Liu told LiveScience.

Tunneling to the past

A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole ? a hypothetical tunnel connecting two regions of space-time.

The regions bridged could be two completely different universes or two parts of one universe. Matter can travel through either mouth of the wormhole to reach a destination on the other side.

"Wormholes are the future, wormholes are the past," said Michio Kaku, author of "Hyperspace" and "Parallel Worlds" and a physicist at the City University of New York. "But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today's technology."

To punch a hole into the fabric of space-time, Kaku explained, would require the energy of a star or negative energy, an exotic entity with an energy of less than nothing.

Greene, an expert on string theory ? which views matter in a minimum of 10 dimensions and tries to bridge the gap between particle physics and nature's fundamental forces, questioned this scenario.

"Many people who study the subject doubt that that approach has any chance of working," Greene said in an interview . "But the basic idea if you're very, very optimistic is that if you fiddle with the wormhole openings, you can make it not only a shortcut from a point in space to another point in space, but a shortcut from one moment in time to another moment in time."

Cosmic strings

Another popular theory for potential time travelers involves something called cosmic strings ? narrow tubes of energy stretched across the entire length of the ever-expanding universe.

These skinny regions, leftover from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.

Cosmic strings are either infinite or they're in loops, with no ends, said J. Richard Gott, author of "Time Travel in Einstein's Universe" and an astrophysicist at Princeton University. "So they are either like spaghetti or Spaghetti-O's."

The approach of two such strings parallel to each other, said Gott, will bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory.

"This is a project that a super-civilization might attempt," Gott told LiveScience. "It's far beyond what we can do. We're a civilization that's not even controlling the energy resources of our planet."

Impossible, for now

Mathematically, you can certainly say something is traveling to the past, Liu said.

"But it is not possible for you and me to travel backward in time," he said.

However, some scientists believe that traveling to the past is, in fact, theoretically possible, though impractical.

Maybe if there were a theory of everything, one could solve all of Einstein's equations through a wormhole, and see whether time travel is really possible, Kaku said.

"But that would require a technology far more advanced than anything we can muster," he said. "Don't expect any young inventor to announce tomorrow in a press release that he or she has invented a time machine in their basement."

For now, the only definitive part of travel in the fourth dimension is that we're stepping further into the future with each passing moment.

So for those hoping to see Earth a million years from now, scientists have good news.

"If you want to know what the Earth is like one million years from now, I'll tell you how to do that," said Greene, a consultant for "Déjà Vu," a recent movie that dealt with time travel. "Build a spaceship. Go near the speed of light for a length of time ? that I could calculate. Come back to Earth, and when you step out of your ship you will have aged perhaps one year while the Earth would have aged one million years. You would have traveled to Earth's future."

i didn't think we could travel at light speed yet?
meh anyway, i always hate reading these things because everyone talks in current technology. who knows what we'll have 100 years down the line?

 

[jtvang125]

88 miles per hour!

 

[So]

Originally posted by: pontifex

Originally posted by: Queasy
Link

The urge to hug a departed loved one again or prevent atrocities are among the compelling reasons that keep the notion of time travel alive in the minds of many.

While the idea makes for great fiction, some scientists now say traveling to the past is impossible.

There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller "The Elegant Universe" and a physicist at Columbia University.

"And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it," he said. "Most of us think that almost all of them can be ruled out."

The fourth dimension

In physics, time is described as a dimension much like length, width and height.

When you travel from your house to the grocery store, you're traveling through a direction in space, making headway in all the spatial dimensions ? length, width and height.

But you're also traveling forward in time, the fourth dimension.

"Space and time are tangled together in a sort of a four-dimensional fabric called space-time," said Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book "One Universe: At Home In The Cosmos."

Space-time, Liu explains, can be thought of as a piece of spandex with four dimensions.

"When something that has mass ? you and I, an object, a planet or any star ? sits in that piece of four-dimensional spandex, it causes it to create a dimple," he said. "That dimple is a manifestation of space-time bending to accommodate this mass."

The bending of space-time causes objects to move on a curved path, and that curvature of space is what we know as gravity.

Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn't share this multi-directional freedom.

"In this four-dimensional space-time, you're only able to move forward in time," Liu told LiveScience.

Tunneling to the past

A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole ? a hypothetical tunnel connecting two regions of space-time.

The regions bridged could be two completely different universes or two parts of one universe. Matter can travel through either mouth of the wormhole to reach a destination on the other side.

"Wormholes are the future, wormholes are the past," said Michio Kaku, author of "Hyperspace" and "Parallel Worlds" and a physicist at the City University of New York. "But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today's technology."

To punch a hole into the fabric of space-time, Kaku explained, would require the energy of a star or negative energy, an exotic entity with an energy of less than nothing.

Greene, an expert on string theory ? which views matter in a minimum of 10 dimensions and tries to bridge the gap between particle physics and nature's fundamental forces, questioned this scenario.

"Many people who study the subject doubt that that approach has any chance of working," Greene said in an interview . "But the basic idea if you're very, very optimistic is that if you fiddle with the wormhole openings, you can make it not only a shortcut from a point in space to another point in space, but a shortcut from one moment in time to another moment in time."

Cosmic strings

Another popular theory for potential time travelers involves something called cosmic strings ? narrow tubes of energy stretched across the entire length of the ever-expanding universe.

These skinny regions, leftover from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.

Cosmic strings are either infinite or they're in loops, with no ends, said J. Richard Gott, author of "Time Travel in Einstein's Universe" and an astrophysicist at Princeton University. "So they are either like spaghetti or Spaghetti-O's."

The approach of two such strings parallel to each other, said Gott, will bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory.

"This is a project that a super-civilization might attempt," Gott told LiveScience. "It's far beyond what we can do. We're a civilization that's not even controlling the energy resources of our planet."

Impossible, for now

Mathematically, you can certainly say something is traveling to the past, Liu said.

"But it is not possible for you and me to travel backward in time," he said.

However, some scientists believe that traveling to the past is, in fact, theoretically possible, though impractical.

Maybe if there were a theory of everything, one could solve all of Einstein's equations through a wormhole, and see whether time travel is really possible, Kaku said.

"But that would require a technology far more advanced than anything we can muster," he said. "Don't expect any young inventor to announce tomorrow in a press release that he or she has invented a time machine in their basement."

For now, the only definitive part of travel in the fourth dimension is that we're stepping further into the future with each passing moment.

So for those hoping to see Earth a million years from now, scientists have good news.

"If you want to know what the Earth is like one million years from now, I'll tell you how to do that," said Greene, a consultant for "Déjà Vu," a recent movie that dealt with time travel. "Build a spaceship. Go near the speed of light for a length of time ? that I could calculate. Come back to Earth, and when you step out of your ship you will have aged perhaps one year while the Earth would have aged one million years. You would have traveled to Earth's future."

i didn't think we could travel at light speed yet?
meh anyway, i always hate reading these things because everyone talks in current technology. who knows what we'll have 100 years down the line?

"NEAR the speed of light"

careful reading FTW!

 

[SSSnail]

If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

 

[James3shin]

10,000 GIGAWATTS of power biatch!

 

[JS80]

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

i thought you could if you can travel at speed of light

 

[SSSnail]

Originally posted by: JS80

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

i thought you could if you can travel at speed of light

Nope, because you'd be there as well. Next theory.

If this ever become possible, I don't think physically traveling will ever get you into the future.

 

[So]

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

 

[Aikouka]

Originally posted by: theGlove
obviously this guy never heard of the flux capacitor

I've always found that term to be quite odd... theoretically all capacitors flux, don't they? :Q

 

[SSSnail]

Originally posted by: So

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

I don't think he did, he offered a great theory on general relativity though. If time is a flat dimension as stated, then one should be able to traverse it back and forth.

 

[Kev]

Originally posted by: So

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

haha, pwned

 

[So]

Originally posted by: SSSnail

Originally posted by: So

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

I don't think he did, he offered a great theory on general relativity though. If time is a flat dimension as stated, then one should be able to traverse it back and forth.

:laugh:

So you debate that you are currently traveling forward in time? You reject the MASS of experimental proof that has shown clock skew in fast moving objects? The other mountains of proof. There is no question that forward time travel is possible, since you're doing it right now, and there are mountains or proof that you can relativistically speed up the passage of time. Don't like it? Too bad, it's a FACT. You're free to stop traveling forward in time if you please, but that would make you dead, and I'd rather you just make peace with forward time travel.

 

[SSSnail]

Originally posted by: So

Originally posted by: SSSnail

Originally posted by: So

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

I don't think he did, he offered a great theory on general relativity though. If time is a flat dimension as stated, then one should be able to traverse it back and forth.

:laugh:

So you debate that you are currently traveling forward in time? You reject the MASS of experimental proof that has shown clock skew in fast moving objects? The other mountains of proof. There is no question that forward time travel is possible, since you're doing it right now, and there are mountains or proof that you can relativistically speed up the passage of time. Don't like it? Too bad, it's a FACT. You're free to stop traveling forward in time if you please, but that would make you dead, and I'd rather you just make peace with forward time travel.

Yes, because we're both traveling towards now, because at no point in time did you leave the present. As for the clock skew, could acceleration and mass has anything to do with it? How fast did they get it going anyways? I didn't know they could launch a clock approaching speed of light. To put this in perspective, if you're sitting in a car, you can't say you're traveling faster than the car if you just lean forward.

With that, I can't just call someone in a different time zone and ask them what the future holds, because that's what you're saying.

Don't get me wrong, scientific proofs are fascinating and I'm a big fan of science. I just don't want to see it turns into a religion.

 

[Kadarin]

It will remain theoretically impossible until someone figures out how to do it. I wouldn't underestimate human ingenuity, and the fact that there's a lot we don't know.

 

[flashbacck]

Originally posted by: SSSnail

Originally posted by: So

Originally posted by: SSSnail

Originally posted by: So

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

I don't think he did, he offered a great theory on general relativity though. If time is a flat dimension as stated, then one should be able to traverse it back and forth.

:laugh:

So you debate that you are currently traveling forward in time? You reject the MASS of experimental proof that has shown clock skew in fast moving objects? The other mountains of proof. There is no question that forward time travel is possible, since you're doing it right now, and there are mountains or proof that you can relativistically speed up the passage of time. Don't like it? Too bad, it's a FACT. You're free to stop traveling forward in time if you please, but that would make you dead, and I'd rather you just make peace with forward time travel.

Yes, because we're both traveling towards now, because at no point in time did you leave the present. As for the clock skew, could acceleration and mass has anything to do with it? How fast did they get it going anyways? I didn't know they could launch a clock approaching speed of light. To put this in perspective, if you're sitting in a car, you can't say you're traveling faster than the car if you just lean forward.

With that, I can't just call someone in a different time zone and ask them what the future holds, because that's what you're saying.

Don't get me wrong, scientific proofs are fascinating and I'm a big fan of science. I just don't want to see it turns into a religion.

Because there's no relative difference in velocity between the objects.

 

[So]

Originally posted by: SSSnail

Originally posted by: So

Originally posted by: SSSnail

Originally posted by: So

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

this dude did, and he did it like this

I don't think he did, he offered a great theory on general relativity though. If time is a flat dimension as stated, then one should be able to traverse it back and forth.

:laugh:

So you debate that you are currently traveling forward in time? You reject the MASS of experimental proof that has shown clock skew in fast moving objects? The other mountains of proof. There is no question that forward time travel is possible, since you're doing it right now, and there are mountains or proof that you can relativistically speed up the passage of time. Don't like it? Too bad, it's a FACT. You're free to stop traveling forward in time if you please, but that would make you dead, and I'd rather you just make peace with forward time travel.

Yes, because we're both traveling towards now, because at no point in time did you leave the present. As for the clock skew, could acceleration and mass has anything to do with it? How fast did they get it going anyways? I didn't know they could launch a clock approaching speed of light. To put this in perspective, if you're sitting in a car, you can't say you're traveling faster than the car if you just lean forward.

With that, I can't just call someone in a different time zone and ask them what the future holds, because that's what you're saying.

Don't get me wrong, scientific proofs are fascinating and I'm a big fan of science. I just don't want to see it turns into a religion.

Put one really sensitive clock in LEO going clockwise around the earth and one going counterclockwise. Measure the times. Again and again and again, the clocks have shown a small but measurable deviation that matched relativity EXACTLY. There have been experiments of this type done that perfectly support relativity and forward time travel. Relativity is one of the most important theories (read:FACTS) of modern science. I'm not asking you to accept it on faith or because a lot of others have. It's a fact because it's supported by mountains of evidence and is perfectly logically coherent. My argument has nothing to do with time zones, and the parallel you attempted to draw makes me have to ask you to actually read up on relativity, because you clearly don't fully understand it.

Edit: Sorry if this comes off as insulting, because I realize it reads that way, but I don't mean to insinuate that you are stupid, so please do not take it that way.

 

[ultimatebob]

Originally posted by: James3shin
10,000 GIGAWATTS of power biatch!

Gigawatts are totally overrated. Jiggawatts is where the real action is at! Gimmie 1.21 of those, and we're good to GO!

Of course, we'll probably need Plutonium, a Mr. Fusion, or maybe a lightning bolt for that, but those should be pretty easy to come by!

 

[40sTheme]

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

You are correct sir.
How exactly did people come up with the idea that moving really fast can move you forward in time? You've moved a certain distance in a period of time, but that does not change what time it is.

 

[So]

Originally posted by: 40sTheme

Originally posted by: SSSnail
If you can't travel backwards, you can't travel forwards either. Prove to me that I'm wrong.

You are correct sir.
How exactly did people come up with the idea that moving really fast can move you forward in time? You've moved a certain distance in a period of time, but that does not change what time it is.

That's funny, because traveling fast does EXACTLY that. It changes how fast your clock appears to tick when compared with another clock that is stationary relative to you.

 

[SSSnail]

Originally posted by: So
Put one really sensitive clock in LEO going clockwise around the earth and one going counterclockwise. Measure the times. Again and again and again, the clocks have shown a small but measurable deviation that matched relativity EXACTLY. There have been experiments of this type done that perfectly support relativity and forward time travel. Relativity is one of the most important theories (read:FACTS) of modern science. I'm not asking you to accept it on faith or because a lot of others have. It's a fact because it's supported by mountains of evidence and is perfectly logically coherent. My argument has nothing to do with time zones, and the parallel you attempted to draw makes me have to ask you to actually read up on relativity, because you clearly don't fully understand it.

Edit: Sorry if this comes off as insulting, because I realize it reads that way, but I don't mean to insinuate that you are stupid, so please do not take it that way.

Don't worry, after reading some of the responses on ATOT, I've learned not to take anything personally. As far as the clock goes, I don't think it's that simple, because it's doesn't take a lot of effort to travel through time, as you put it.

If that was the case, we'd all be in orbit trying to travel through time. Guess what happens when you land? Yup, you'd be right here in the present with us, regardless of what your clock tells you.

I'm not a physicist, so my understanding of the subject is very limited. I draw my conclusion from reading information that are widely available, which may or may not include the publications that proved this theory of relativity. By the way, why is it still a theory if it's proven? IMHO, time traveling would be possible when we learn how to bend the dimension, and this won't be accomplish with any speed.