time travel

[dejitaru]

But as you approach the speed of light, your mass becomes infinite. Theoretically, doesnt this make traveling at speed C impossible?

I would say so.
But if time slows as you approach c, wouldn't travelling faster than c permit you to travel back in time?

Say you safely land on a black hole of immense density. By its high gravity, wouldn't the "speed of light" be greatly decreased? If its gravity is so high that light cannot escape, could the speed of an ordinary stroll across its surface be enough for detectable time travel?

 

[Daxxax]

<Beavis>Uhhhhh you guys are smart!!</Beavis>

 

[Akira13]

Originally posted by: dejitaru

But as you approach the speed of light, your mass becomes infinite. Theoretically, doesnt this make traveling at speed C impossible?

I would say so.
But if time slows as you approach c, wouldn't travelling faster than c permit you to travel back in time?

Say you safely land on a black hole of immense density. By its high gravity, wouldn't the "speed of light" be greatly decreased? If its gravity is so high that light cannot escape, could the speed of an ordinary stroll across its surface be enough for detectable time travel?

I think that the speed of light isn't changed with gravity, but the path of light is changed. I haven't read the whole thread, but I have quite the love/hate relationship with gravity.

 

[Akira13]

On the same note, has anyone seen that old film of "what we would see if we were riding on a bicycle at the speed of light"? It's basically a black and white film of someone riding down a street (in first person). While approaching the speed of light, the street lights start to bend towards you, and you can see the tops and far sides of buildings. I don't remember the explanation for that, but I thought it was cool.

 

[rimshaker]

Personally, as much as I can't explain it , I don't think light is the absolute fastest entity in the universe. In the grand scheme of the universe, there is much that mankind still doesn't know about in terms of new physics and chemistry.

And in case no one has heard yet, they're currently disputing the famous E=mc^2 expression. Apparantly, it may not be an absolute constant, but may be also affected by relativity.

 

[Sohcan]

Originally posted by: rimshaker
In the grand scheme of the universe, there is much that mankind still doesn't know about in terms of new physics and chemistry.

Of course, any competent physicist would admit this. In fact, the theoretical physicists that I've worked with would love a new avenue to be opened up, it will keep them employed for a few more decades .

We've known for decades that while special relativity gets along with quantum mechanics very well, general relativity does not. It is obvious that a more accurate model will eventually replace general relativity. But that does not mean general relativity is useless; quantum mechanics and special and general relativity ultimately showed that classical mechanics was flawed, but classical mechanics is still used except in cases of atomic scales, high velocities and acceleration, low temperatures, and high energies because of its relative simplicity. By analogy it may be reasonable to assume that a more accurate model that replaces those of modern physics will also behave accordingly.

And in case no one has heard yet, they're currently disputing the famous E=mc^2 expression. Apparantly, it may not be an absolute constant, but may be also affected by relativity.

Ah, the mass-energy equation has employed relativity for about 97 years . The rest mass equation, E = mc^2, is often misquoted....the relativistic mass-energy equation is actually E = (mc^2) / (1 - (v/c)^2)^.5.

 

[Sahakiel]

Originally posted by: dejitaru
We're all travelling through time at the rate of one second per second - but that's not what I mean.

I may be ignorant, but I'm having a hard time swallowing that.

I'd like to point out that until we discard our instictive reasoning of everyday physics and utilize the same framework for analysis, no matter how much data/speculation/theory/flatulation gets thrown in, nobody's going to understand each other. It seems like there are a few posters who understand relativity, a few more (like me) who somewhat grasp the idea, and the others who've only just begun to touch upon the idea that time does not "flow" constantly.

From what I can remember, special relativity concluded that two observers in different frame of references always saw the same event occuring. The only difference was that their measurements of the distance and the time of occurance differed. What ended up happening was that everything can only travel at the speed of light. But, with spacetime, there are four axes, x, y, z, and t, resulting in the speed of light c being split up amongst the four axes via pythagorean, c² = x²+y²+z²+t². Either that, or I'm getting confused with another theory. At any rate, I'm sure the pythagorean part holds true, just not sure about the speed of light being the only speed.

That said, I wonder what you guys would think about the idea of "time" being not the fourth dimension, nor another axis of measure, nor even an independent variable, but as the result of causality. I mean, if you think about it, how is time measured? Crystal oscillations, swinging pendulums, the path of the sun across the sky, the path of the Earth around the sun, and so forth. All we've done is just relate one "measure" of time to the other.
Take, for example, the measure of one year. That's the time it takes for the Earth to orbit the sun once. Then, break that down into months, days, hours, minutes, seconds, nanoseconds, until you get to the number of oscillations for a weight on a string, quartz or cesium or whatever you're using. None of these really measures "time" as we traditionally picture it. The Earth's orbit is influenced, even if only minutely, by external forces. Swinging weights are influenced by gravitational fluctuations and air resistence. Crystals are influenced by heat and the actualy instruments used to measure them. In fact, according to Heisenburg's simple, yet annoying principle, you can never measure the exact position of your measuring device without messing up its oscillation, which would mess up its measure of time, which means in order to keep an exact measure of time, we would never be able to know what time it is.
The conclusion of this long spiel is time does not cause events to occur, these events cause time. It is only because these events occur that we can actually come up with a measure of time; that we can actually perceive the passage of time.

 

[Grminalac]

Take the example of a very long train travelling in a vaccum in a straight line at very high velocity. In the middle of the train two flashlights are pointed facing opposite ends. They are turned on at an identical time, and the two beams of light hit the opposite ends of the train at the same time. Classical physics would show that the speed of the light travelling with the train would have been c + the speed of the train and the speed of the beam travelling against the train c - the speed of the train however this is not the case. In fact the light remained at a constant speed the entire time.
Is this explained by the fact that time has changed in respect to allow light to remain constant?
If I am grasping this correctly, things would appear normal for a person on the train, however to an outside observer travelling at a different velocity the appearance of the train would be very sckewed.

 

[IaPuP]

Why is the effect not reversed with deceleration?

I think that's because there is no such thing as "deceleration" unless you've already decided on a fixed point of reference.

When you are traveling a .99c with no acceleration, from your point of reference, you are not moving. Perhaps there are objects you are passing which are travelling at .99c in the other direction (from who's relative perspective YOU are traveling .99c) but you youself are not moving because from your perspective, when you shine a flashlight out in front of you (or behind you), its light travels away from you at c.

So when you decide to match your speed with the objects around you (you call that "decelerating" I guess), you simply acceerate to the same .99c that you OBSERVE the objects around you to be traveling. That's is not "decelration" per-say. It is "acceleration" to .99c in the opposite direction.

If you are standing on the planet that you started from, obviously, you observe it to be "deceleration" from .99c to 0 but from your perspective ON the ship, it is merely "acceleration in the opposite direction". Since the direction of acceleration means basically nothing in terms of relativity, you have your answer.

Eric

 

[dejitaru]

I think that's because there is no such thing as "deceleration" unless you've already decided on a fixed point of reference.
When you are traveling a .99c with no acceleration, from your point of reference, you are not moving. Perhaps there are objects you are passing which are travelling at .99c in the other direction (from who's relative perspective YOU are traveling .99c) but you youself are not moving because from your perspective, when you shine a flashlight out in front of you (or behind you), its light travels away from you at c.
So when you decide to match your speed with the objects around you (you call that "decelerating" I guess), you simply acceerate to the same .99c that you OBSERVE the objects around you to be traveling. That's is not "decelration" per-say. It is "acceleration" to .99c in the opposite direction.
If you are standing on the planet that you started from, obviously, you observe it to be "deceleration" from .99c to 0 but from your perspective ON the ship, it is merely "acceleration in the opposite direction". Since the direction of acceleration means basically nothing in terms of relativity, you have your answer.

Yes, but someone said that it relies on acceleration, I say gravity.

I don't think light is the absolute fastest entity in the universe

Yeah, it's restricted even by gravity, may be obstructed by common bjects. It's just the fastest yet discovered, perhaps noticeably faster in microgravity.

 

[Akira13]

Originally posted by: IaPuP

Why is the effect not reversed with deceleration?

I think that's because there is no such thing as "deceleration" unless you've already decided on a fixed point of reference.

"Deceleration" is actually acceleration in a negative direction.

 

[RossGr]

Very nice thread, Sohcan as done an execellent job of presenting the physically "correct" information. Just a couple of points. Maxwells equations are the source of the constancy of the speed of light, to deny the constancy of the speed of light is to deny Maxwells equations, to deny Maxwells equations is to deny the existance of our moderen electronic socity. So if you own a televison, a radio, a computer or any other electrical device and deny that the speed of light is constant you are an unknowning hypocrite, your electronic devices rely on the speed of light in a very fundamental way were it not constant they simply would not work. Radios would not work in airplanes because the frequency would be shifting witht the velocity, even car radios would fail. A constant c is necessary for all of these devices to work. They relie on Maxwells equations.

When Maxwell first derived the speed of Electromagnetic waves (about 1867) he was surprised to find that his predicted number matched the current experimental number for the speed of light. Though it had been sujested that light was electomagnetic in nature this was the first TRUE evidence that it was electromagnetic. For the next 40yrs the world of Physics tusseled with this piece of the puzzel that did not fit. How could the fact that the speed of light was determined by fundamental universal constants be rectified with the then accepted thoeory of relativity, the Galliean velocity transforms, which insisted that the velocity had to depend on the velocity of the emitting body. This was called Maxwells Cundrum and most Physicist felt that the trouble was with Maxwells work and it was his job to straighten it out and get it right. Mean while Michelson and Morely set out to do measurement sto prove that the concept was wrong, though they has the capability to detect the varitions preticted by the Gallean transforms they WERE UNABLE to detect them, thus varifiing that which they has set out to disporve. In the 1880 s Hertz finally generated the Electromagnetic waves predicted by Maxwell 20 yrs earlier, thus began our modern electronic world. In 1905 Einstein finally did the analysis (Special Relativity) which demonstrated that it was possible to fit the constancy of the speed of light into Classical physics. It required a revolutionary mind set change but it worked and was soon verified experimently. Though history reveals that some of the early experiments were pretty dodgy and may have relied more on wishful thinking then sound measurements. (We do better now!)

Someone mentioned "In Search of Schrodingers Cat" the auther is John Gribbin, this is recommened reading for all. Sohcan, if you have not read it, find a copy it is a very well written history/explaination of modern physics.

BTW
I also have a BS in Physics from Oregon State U. (1977)

 

[shansen008]

Just a little note about what you would "see" if you were traveling at the speed of light:

I think this whole subject tends to overwhelm peoples' minds and it forces them into oversimplifying. If you were traveling in any direction at the speed of light, and rotated 360 degrees while still traveling in the same direction, light woud still be entering your eyes at different angles. The only angle you would NOT see would be the single degree in the direction you are traveling away from. Even if you were standing in the direction you were leaving, traveling at the speed of light, light would be entering your eyes at 89 degrees from either side of you. I can only imagine how confusing this would be to the brain, would probably force anyone into an epileptic seizure hehe.

Interesting thread.

 

[Howard]

Why 89 degrees?

 

[Hamburgerpimp]

we may be able to travel great distances forward, or even backward through time

According to thousands of persons it already has happened. The Montauk Experiments in Long Island, NY got so out of hand, they shut it down many years ago and filled in all the labs with concrete. What IS known is that the Experiments really happened. What IS NOT known is if time travel actually happened.

Something even "crazier" to think about is the Philadelphia Experiment:

The origin of the Montauk Proiect dates back to 1943 when radar invisibility was being researched aboard the USS Eldridge. As the Eldridridge was stationed at the Philadelphia Navy Yard, the events concerning the ship have commonly been referred to as: the "Philadelphia Experiment". The objective of this experiment was to make the ship undetectable to radar and while that was achieved, there was a totally unexpected and drastic side effect. The ship became invisible to the naked eye and was removed from time and space as we know it! Although this was a remarkable breakthrough in terms of technology, it was a catastrophe to the people involved. Sailors had been transported out of this dimension and returned in a statc of complete mental disorientation and horror. Some were even planted into the bulkhead of the ship itself. Those who survived were discharged as "mentally unfit" or otherwise discredited and the entire affair was covered up. After the war, research continued under the tutelage of Dr. John von Neumann who had directed the technical aspects of the Philadelphia Experiment.

 

[Jeff7]

Originally posted by: Wolfie
I may not sound as technical as some of you, but this caught my attn. and I have one question.
WHAT IF
Someone was in a plane, flying in the opposite direction of time. Say to the west. And continued for a while at a high rate of speed. Would he age faster then the people that stayed behind? Or would he age slower?

Steven Hawking said something about that in his "The Universe in a Nutshell" book. He said that the tiny amount of time you'd gain (don't remember which direction you'd have to fly) would be "offset by eating the airline food."
Plus, what exactly is the "direction of time?" Good luck finding it.

Originally posted by: TheSnowman
i dont think the slowing of time is relitive to gravity

Steven Hawking also would disagree. As gravity increases, time slows down - according to that same book, as an observer approached the event horizon of a black hole, time would slow and eventually stop.

I can only imagine how confusing this would be to the brain, would probably force anyone into an epileptic seizure hehe.

I could stand to have a more powerful brain! They need to do for neurons what has been done for transistor sizes - make them smaller, quicker, while using less power. Engineer people for bigger brains, and there's problems. (yes, some of these are from Steven Hawking's book) One of course is giving birth to something with an even bigger brain than what we've got. Second, we have two options, more of one would detract from the other: smart or quick. Smaller, more efficient neurons or something to replace them could provide a workaround. You might just need to wear a heatsink hat all the time.

Why 89 degrees?

Probably more like 89.99999..... degrees. If light approached your eye at exactly 90 degrees or greater, it wouldn't be perceived because it wouldn't be able to make it to the retina.

It would be so cool to have all the time in the universe to research this stuff. Of course, we'd need those advanced brains of the future to be able to actually understand and perhaps even to perceive the discoveries awaiting us. Of course, for now, we might want to concentrate on not annhialating ourselves in nuclear war. (not trying to deviate from the subject here)