Time travel question...

[Singular Intellect]

Having recently watched the 2002 remake of "The Time Machine", it brought up a question I thought I'd ask here.

In the movie, Alexander builds his time machine which projects a bubble around him and time accelerates rapidly around him as he 'moves' into the future.

According to modern physics, time travel into the future is possible, although using a radically different system and is 'very expensive' as I heard it put.

Setting aside all the movie's scientific errors and time travel to the past, is it even theoritically possible for a (presumeably spherical) pocket of space to exist within Earth's gravity well whereas an individual within it would observe the passage of time around him at a vastly accelerated rate, or is that concept just pure fantasy?

[Crossroads Inc.]

as far as I know, if you traveled in time, only, the world would be long gone when you stopped, as it moves while you stay in place.. You would need to somehow affix yourself to a location while you moved in time... Or... simply travel in jumps where you come out of Time Trvael at a point where the Earth is in the EXACT spot in which you went in.

[Singular Intellect]

as far as I know, if you traveled in time, only, the world would be long gone when you stopped, as it moves while you stay in place.. You would need to somehow affix yourself to a location while you moved in time... Or... simply travel in jumps where you come out of Time Trvael at a point where the Earth is in the EXACT spot in which you went in.

I think the best way to describe what I'm talking about, is imagine this hypothetical time traveller is located near some city center in his little time bubble. Everyone can see him, and from their perspective his movements and actions are hundreds or thousands of times slower than everyone else's (almost appearing frozen in place), unless anyone or anything enters that bubble, and therefore is subject to it's relative time. There doesn't seem to be a valid reason why he or his bubble would shoot off into space.

However from his perspective everyone and everything around him is moving so quickly that it would be a blur unless whatever being looked at is stationary or relatively unchanging for months for 'outside' time.

[freker]

what about light traveling in and out of the bubble, since light travels slower inside the bubble, the concentration of light increases. the concetration would then become as relatively high as the time difference. for instance: if time is 100.000 slower, the concentration of light would be 100.000 times higher. this would also go for everything else entering the bubble.

and what would happen at the interface between nornal time and slowed time, would that be a direct transit or would there be a thick boundary layer in which time slowes (or accelerates, depending which way you would go)

[Marko Dash]

i think what crossroads meant was that if our traveler's bubble stayed still, the earth would move out from underneath him as it orbited. even if he timed it so that he came out in exactly 1 year, it wouldn't be the same spot. even a few dozen feet off will bury him under tons of earth or leave him falling to his death.

[Surlethe]

what about light traveling in and out of the bubble, since light travels slower inside the bubble

Why is this, again? One would expect that relativity still holds.

[Singular Intellect]

i think what crossroads meant was that if our traveler's bubble stayed still, the earth would move out from underneath him as it orbited.

Which brings up the question as to why gravity and interia suddenly don't apply to this spherical pocket of space just because it has a different relative passage of time.

even if he timed it so that he came out in exactly 1 year, it wouldn't be the same spot. even a few dozen feet off will bury him under tons of earth or leave him falling to his death.

You're picturing this as one of those Star Trek scenarios where the traveller instantly pops into the future, whereas I'm talking about experiencing time at a different rate of 'speed', which is quite well documented in modern physics. I'm merely taking that example and applying several orders of magnitude to it's scale.

[Singular Intellect]

what about light traveling in and out of the bubble, since light travels slower inside the bubble, the concentration of light increases. the concetration would then become as relatively high as the time difference. for instance: if time is 100.000 slower, the concentration of light would be 100.000 times higher. this would also go for everything else entering the bubble.

Surlethe answered this.

and what would happen at the interface between nornal time and slowed time, would that be a direct transit or would there be a thick boundary layer in which time slowes (or accelerates, depending which way you would go)

One could propose either I suppose, I didn't specify. Depending upon a more scientifically educated opinion, we'd stick to the most 'practical' or 'realistic' boundary, assuming there is one. My best guess is it would probably be more likely there's a substantial boundary where a moving object or person going to or leaving the bubble's center might notice the change in time 'speed'.

However this does bring up the interesting conclusion that our (presumeably intelligent) time traveller better have accounted for the unexpected introduction of moving objects and matter into this bubble of his, including even people (as I said, we're ignoring the movie I quoted where Alexander appears to be out of 'phase' with normal matter, not just moving through time). Our time traveller simply must have a defensive shield (ie: thick glass) in place to prevent harm or even potential death from anything incoming from the outside.

For example, let's assume our time traveller is experiencing a time rate one million times faster than outside time. In other words, for every second he experiences, one million seconds go by for everyone else outside the bubble (or about eleven and a half days roughly). Let's further assume that roughly every second day of outside time that some moving object flies towards our traveller, whether it's a bird, flying leaf, penny thrown by some mischievous individual, random drive by shooting bullet, etc.

That means for our poor time traveller, he is getting hit by almost six random objects every one of his seconds. They are no more lethal to him than they would be to anyone outside the bubble, he's just coming across these flying objects a million times faster than another person would without the time bubble.

[freker]

Surlethe wrote:

freker wrote:

what about light traveling in and out of the bubble, since light travels slower inside the bubble

Why is this, again? One would expect that relativity still holds.

when photons move in normal space they cover approx 300.000.000 meters/sec. in the bubble, where they move 100.000 times slower (relatively), they cover 3.000 meters/sec. when the bubble would be 300.000.000 meters across (for ease of calculations) it would take 100.000 seconds to pass through the bubble (seen from normal space), when a continues beam is aimed at the bubble, 100.000 times a much light can enter before light starts to exit.

[Singular Intellect]

Surlethe wrote:

freker wrote:

what about light traveling in and out of the bubble, since light travels slower inside the bubble

Why is this, again? One would expect that relativity still holds.

when photons move in normal space they cover approx 300.000.000 meters/sec. in the bubble, where they move 100.000 times slower (relatively), they cover 3.000 meters/sec. when the bubble would be 300.000.000 meters across (for ease of calculations) it would take 100.000 seconds to pass through the bubble (seen from normal space), when a continues beam is aimed at the bubble, 100.000 times a much light can enter before light starts to exit.

You obviously aren't familiar with relativity. You better read up on it before trying to 'correct' someone on it.

[wjs7744]

For example, let's assume our time traveller is experiencing a time rate one million times faster than outside time. In other words, for every second he experiences, one million seconds go by for everyone else outside the bubble (or about eleven and a half days roughly). Let's further assume that roughly every second day of outside time that some moving object flies towards our traveller, whether it's a bird, flying leaf, penny thrown by some mischievous individual, random drive by shooting bullet, etc.

That means for our poor time traveller, he is getting hit by almost six random objects every one of his seconds. They are no more lethal to him than they would be to anyone outside the bubble, he's just coming across these flying objects a million times faster than another person would without the time bubble.

What about ordinary sunlight? I dont remember much about relativity, so I can't comment on the speed of that light, but it strikes me that being hit with 11 days worth of sunlight per second wouldn't be very good for you.

[Surlethe]

when photons move in normal space they cover approx 300.000.000 meters/sec. in the bubble, where they move 100.000 times slower (relatively), they cover 3.000 meters/sec. when the bubble would be 300.000.000 meters across (for ease of calculations) it would take 100.000 seconds to pass through the bubble (seen from normal space), when a continues beam is aimed at the bubble, 100.000 times a much light can enter before light starts to exit.

You're still operating under Newtonian assumptions, which violates the fundamental postulate that the speed of light is the same for all observers.

[Singular Intellect]

What about ordinary sunlight? I dont remember much about relativity, so I can't comment on the speed of that light, but it strikes me that being hit with 11 days worth of sunlight per second wouldn't be very good for you.

While you might end up being hit with a million times more sunlight, you're only being exposed to it a millionth of 'normal' exposure time anyhow.

[Steel]

The way that relativity deals with the sunlight issue would be to expand space inside the bubble. This would mean that the intensity of sunlight you would recieve on the inside would be the same as if you were on the outside, as the light is stretched out as it crosses the boundary.

In normal frame with coordinates (x,t) a light ray travels as dx=c dt

In bubble frame, (x',t'), We have dx'=c dt' (as the speed of light is the same for all observers)

If dt'=dt/T where T is the time dialtion factor (100,000 as people seem to be using)

then dx' = T dx

Hence the space enclosed in the bubble is greatly expanded. Not sure exactly what that means for you in the bubble though... I think it would appear the same size to you. However it certainly means that if (for T=100,000) you run a 200,000m ladder in to one side of the 2m bubble, it wont poke out the other side. (This is the same as the standard paradox of the ladder in the barn)

On a semi related note, i think this is the opposite of what happened when the wizards were playing about in the latest discworld book... but i hope i have a better grasp of relativity than most fiction authors.

[wjs7744]

While you might end up being hit with a million times more sunlight, you're only being exposed to it a millionth of 'normal' exposure time anyhow.

Eh? I say that the power intensity of the sunlight would be a million times greater, and you respond that that's OK because it occurs over one millionth of the time? That is exactly what I said, since P=E/t. Is that what you meant to say, because your statement sounded like a rebuttal. God, I wish I could think straight right now.

The way that relativity deals with the sunlight issue would be to expand space inside the bubble. This would mean that the intensity of sunlight you would recieve on the inside would be the same as if you were on the outside, as the light is stretched out as it crosses the boundary.

In normal frame with coordinates (x,t) a light ray travels as dx=c dt

In bubble frame, (x',t'), We have dx'=c dt' (as the speed of light is the same for all observers)

If dt'=dt/T where T is the time dialtion factor (100,000 as people seem to be using)

then dx' = T dx

Hence the space enclosed in the bubble is greatly expanded. Not sure exactly what that means for you in the bubble though... I think it would appear the same size to you. However it certainly means that if (for T=100,000) you run a 200,000m ladder in to one side of the 2m bubble, it wont poke out the other side. (This is the same as the standard paradox of the ladder in the barn)

On a semi related note, i think this is the opposite of what happened when the wizards were playing about in the latest discworld book... but i hope i have a better grasp of relativity than most fiction authors.

I think I must be doing something horribly wrong, as when I try to recreate your calculations, I end up with dx' = dx / T. Of course, I don't understand the scientific portion of it, so I can't comment on that bit.

BTW, which book is that you are referring to? I don't remember that.

[Winston Blake]

While you might end up being hit with a million times more sunlight, you're only being exposed to it a millionth of 'normal' exposure time anyhow.

Eh? I say that the power intensity of the sunlight would be a million times greater, and you respond that that's OK because it occurs over one millionth of the time? That is exactly what I said, since P=E/t. Is that what you meant to say, because your statement sounded like a rebuttal. God, I wish I could think straight right now.

It's a million times more sunlight in a million times the exposure, not a millionth. The photon train is slowed down by the exact factor its density is increased by, so the flow rate is the same.

After the first photon exits the bubble, the flow rate in equals the flow rate out. The guy inside is not experiencing any greater intensity. Sure, there's 'more' sunlight in the bubble, but that means greater energy density, not greater intensity.

Relativistically, the speed of light should remain the same for all observers. Anybody in the bubble has their observation processes slowed down by the same amount that the light is slowed down, so it 'appears' to be going its normal speed. I imagine looking through the bubble from either side would be analogous to slowing light down in transparent materials, except with an infinite number of infinitesimal interatomic delays.

This sort of bubble must have a very high index of refraction that permeates all space inside it and applies equally to all the carriers of the fundamental forces. This would make every physical process slower, including life. This bubble would also be extremely reflective. This is an idea I had a while ago when thinking about scifi 'stasis' fields.

As for the OP, if you could slow down your biological processes, your brain would see everything going faster. Suspended animation requires unconsciousness, but 'mind uploading' to a computer would do the trick. Or something similar, e.g. replacing all brain neurons with nanites that handle the same messages, except slower (may require life extension). This stuff is soft science of course.

[Steel]

While you might end up being hit with a million times more sunlight, you're only being exposed to it a millionth of 'normal' exposure time anyhow.

Eh? I say that the power intensity of the sunlight would be a million times greater, and you respond that that's OK because it occurs over one millionth of the time? That is exactly what I said, since P=E/t. Is that what you meant to say, because your statement sounded like a rebuttal. God, I wish I could think straight right now.

The way that relativity deals with the sunlight issue would be to expand space inside the bubble. This would mean that the intensity of sunlight you would recieve on the inside would be the same as if you were on the outside, as the light is stretched out as it crosses the boundary.

In normal frame with coordinates (x,t) a light ray travels as dx=c dt

In bubble frame, (x',t'), We have dx'=c dt' (as the speed of light is the same for all observers)

If dt'=dt/T where T is the time dialtion factor (100,000 as people seem to be using)

then dx' = T dx

Hence the space enclosed in the bubble is greatly expanded. Not sure exactly what that means for you in the bubble though... I think it would appear the same size to you. However it certainly means that if (for T=100,000) you run a 200,000m ladder in to one side of the 2m bubble, it wont poke out the other side. (This is the same as the standard paradox of the ladder in the barn)

On a semi related note, i think this is the opposite of what happened when the wizards were playing about in the latest discworld book... but i hope i have a better grasp of relativity than most fiction authors.

I think I must be doing something horribly wrong, as when I try to recreate your calculations, I end up with dx' = dx / T. Of course, I don't understand the scientific portion of it, so I can't comment on that bit.

BTW, which book is that you are referring to? I don't remember that.

Hmmm... yes shit. Does look like you get dx'=dx/T. I didnt actually work it out i just assumed the answer based off intuition... Now i think about it, i was misremembering my original conclusion i came to after reading the discworld book. In the book, the character says if you shrink time you expand space, but i thought that shrink time => shrink space. I got confused which one was my conclusion So now i'm not so sure how the whole situation would work.

The line was a throwaway comment by the professor that took them to stibbons in the massive room with the 'tree' in making money.

[Kuroneko]

If the effect is relativistic, then the Lorentz-boosted Alexander will observe blue-shifted incoming radiation, and thus will experience a rather uncomfortably intense radiation if the boost is large. This happens routinely in near a gravitating body; for a Schwarzschild black hole, for example, merely being near the event horizon is enough. Lorentz contraction doesn't change this fact at all--all it means is that what may be a millimeter in Schwarzschild coordinates may be a light-year when normalized to a frame of an observer hovering just above the horizon.

I'm at a loss at how this can be done while remaining stationary without seriously affecting the immediate surroundings, however, even given arbitrary amounts of positive and negative mass. Clearly spherically symmetric distributions won't do the trick, as spacetime will be flat at the center (unboosted relative to an observer at infinity), whereas having an asymmetric distribution will tend to accelerate the the system.

It's a million times more sunlight in a million times the exposure, not a millionth. The photon train is slowed down by the exact factor its density is increased by, so the flow rate is the same.

After the first photon exits the bubble, the flow rate in equals the flow rate out. The guy inside is not experiencing any greater intensity. Sure, there's 'more' sunlight in the bubble, but that means greater energy density, not greater intensity.

... This sort of bubble must have a very high index of refraction that permeates all space inside it and applies equally to all the carriers of the fundamental forces. ...

This has several problems, though. The bubble would essentially store the incident energy, suspending (most of) the light wavefront around Alexander. When the bubble collapses, all that lagged information would suddenly be upon him in a flash. I suppose one could invent some further pseudomagic to deal with that, but a larger problem with this scenario is that it simply does not conform to the described effect in the OP (er, third post). If the bubble if one light-microsecond in radius and forms instantaneously, for example, then using the dilation factor of 100,000, in the first 0.1s (external time), Alexander would observe the 1μs of information already inbound to him, and perceive it in normal subjective speed, while the subsequent 0.1s of information would not yet reach him. And so on, with the bubble storing ever more energy and Alexander's observations lagging behind by the reciprocal factor of 1/100,000.


P.S. The OP's handle seems very appropriate to this thread.

[wjs7744]

So, basically I was right about the intensity of radiation being greatly increased? Of course, I missed the blue shift thing, so instead of being hit by gigajoules of visible light, he'll get hit with a massive burst of X-rays instead? Things are looking better for our time traveller by the minute...

[HRogge]

There might be some problems with the pressure inside his bubble too.

Because of the similar temperature the chance per second that an air molecule is moved through the bubble should be similar (without any wind), but time is moving faster outside than inside... I'm not completely sure about this, but I think it might be possible that air would moving in faster than it would move out until a pressure difference counters the time difference.

In addition to this there will be LOTS of mechanical stress to anything in contact with the field... can't be healthy if some part of you is moving 1 million times faster than the other part. Depending on the "time gradient" (might be even a two dimensional bubble !) this could be enough to rip apart anything, including molecules...

[Zwinmar]

So, basically I was right about the intensity of radiation being greatly increased? Of course, I missed the blue shift thing, so instead of being hit by gigajoules of visible light, he'll get hit with a massive burst of X-rays instead? Things are looking better for our time traveller by the minute...

Actually by going that fast he would be going faster than the speed of light. So Id imagine he would get hit with gamma rather than xrays. If not something farther down the spectrum that we havent discovered yet. At the same time however, he may get bombarded with all spectrums of light.

[Winston Blake]

I suppose one could invent some further pseudomagic to deal with that, but a larger problem with this scenario is that it simply does not conform to the described effect in the OP (er, third post). If the bubble if one light-microsecond in radius and forms instantaneously, for example, then using the dilation factor of 100,000, in the first 0.1s (external time), Alexander would observe the 1μs of information already inbound to him, and perceive it in normal subjective speed, while the subsequent 0.1s of information would not yet reach him. And so on, with the bubble storing ever more energy and Alexander's observations lagging behind by the reciprocal factor of 1/100,000.

The way I'm picturing it, Alexander perceives the world at the normal subjective speed only for the first 0.1s. When the bubble is created, the photons heading towards his eyes that are within one light-microsecond are 'frozen' at their normal 'separation'. So for the first 0.1s, the light flow rate is 1e5x less, matching Alexander's 1e5x slower brain and giving no subjective change.

However, incident photons are 'bunched up' by factor of 1e5x as they pass into the bubble. After 0.1s, light flows into his eyes at the normal rate, making the world appear to be moving 1e5x faster to him. His skin is also merely absorbing energy at the normal rate, so he isn't burnt. Stored energy doesn't accumulate without limit, it only increases until 0.2s after bubble creation, when light starts to exit the bubble at the same rate it enters.

How is this incorrect?

[Winston Blake]

Actually, he does get burnt, since his skin is 'perceiving' a 1e5x greater flux. His body is absorbing the normal number of photons per second in external time only; inside it's 1e5x greater. Given that he just invented a time bubble, he may be able to invent an 'opacity bubble' that flickers on and off with a 1/1e15x duty cycle to block out the harsh, deadly rays.

An OP-violating solution would be to do his experiment in a dark underground vault.

There might be some problems with the pressure inside his bubble too.

Because of the similar temperature the chance per second that an air molecule is moved through the bubble should be similar (without any wind), but time is moving faster outside than inside... I'm not completely sure about this, but I think it might be possible that air would moving in faster than it would move out until a pressure difference counters the time difference.

This is reasonable. Since the air inside the bubble appears to be n-times colder, the pressures with be equal when there's n-times greater air density in the bubble. Internally, the pressure gets n-times higher.

Hmmm, Alexander needs to encase his time bubble in a double-layered forcefield bubble, then pump out the air between the layers until the pressure drops by n-times. Then creating the time bubble between the two forcefield layers will prevent a nasty pressure rise.

Against the OP, that dark underground vault would need to be a hypobaric chamber too.

[Kuroneko]

You're right (about revised stance). I suppose it shouldn't have been to surprising: such a field behaves just like a "Lorentz boost without actual motion".