This touches on a number of subjects so I'll let JamesR decide where it ultimately belongs.

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Ok. Suppose that FTL is seriously, truly forever impossible. There go our dreams of colinizing the galaxy. No quick, easy travel between the stars in reasonable times.

Not necessarily.

Imagine a future in which human consciousness no longer resides in a biological package. We all know that our perception of time is, to some degree, subjective. Suppose we, as a future society of non-biological beings, decide that we want that galactic civilization? Where a trip to the center of the galaxy is a matter of a week not 30,000 years at close to light speed?

Imagine that 50% light speed is found to be a reasonably achievable speed. Journey to the center of the galaxy (earth time): 60,000 years.

How much would we have to slow our perception of time, as a species, to make that seem like a week?

60000yr*52wk/yr = 3.12e6 wks.

We would have to slow down by about 3 million times. 1 second would be equivalent to about 35 days of time as we experience it now. What interesting effects would arise from this? Every process you now see and observe would happen 3m times faster.

How would the universe seem to us?

A current year would last 10.5 seconds of "new time". The earth woud spin at a percieved 30 milliseconds per revolution. Of course, all forces would still be percieved the same. Only things with rates of change would appear different. We would have to redefine our entire perception of the universe.

Also, how do we know that there aren't entities that exist at a much reduced subjective time perception from us. What defines our inherent perception of time?

Many interesting things to consider.

Actually, while traveling these vast distances - your perception would be that everything is occuring 3m times slower! Not until you decelerate do you experience a singularity in simultaneity perception or whatever you want to call it (gooble-gook special relativity is what I believe MacM would refer to it as). It's is not until after (during?) this deceleration that you "see" everything happen at blazing speeds. At least that is my understanding (misunderstanding? :D)

Aer,

No no no. I'm not talking about speed, or changing physics or anything. This has nothing to do with special or general relativity. I'm talking about slowing your internal perception of the passage of time such that 60000 years (current time perception) seems like a week to you.

Imagine watching the earth spin. If your perception of time is 3m times slower, the earth and every time dependent process around you will seem to be 3m times faster. And, after redefinig the second and the meter to match your new perceptions, the speed of light would seem to be 3m times faster.

Are you sure the speed of light would be 3m times faster? I am not sure that this is anything more than redefining the week to be a century (for example). One might be able to live for 1000 centuries and call each century a week, but??? Hmm... just thinking out loud I guess.

As I said. No physical properties of the universe change. Only your perception of them.

One might be able to live for 1000 centuries and call each century a week

Yes.

Sooo bored with SRT stuff. I thought this was a neat idea to get around the light speed limitation. Any more thoughts? Why wouldn't this be practical, etc...?

Sooo bored with SRT stuff. I thought this was a neat idea to get around the light speed limitation. Any more thoughts? Why wouldn't this be practical, etc...?
It depends on what you think is practical. 1 second is still going to be 1 second whether you live for 100 years or 10 million years.

Hi Super,
It's an interesting thought... but perhaps a better way to go would be on increasing patience and long-term outlook, rather than reducing time perception?

Otherwise, it seems an awful waste of time!

Pete

Aer,

Your actual perception of time passage would change so that 35 days as we percieve it now would seem like a second to you.

Pete,

Yeah. 3e6:1 seems a bit much. Assume the earth has another 2 billion years of habitability left (I think it's less - maybe ony 500 million yrs) due to solar luminosity increasing. On our new time scale that would be just under 700 years! Ugh!

Oh well. It was a thought.

Aer,
Your actual perception of time passage would change so that 35 days as we percieve it now would seem like a second to you.

I realized what you were proposing, but I don't agree with arbitrarily saying 35 days "seem" like 1 second - in 10 seconds on earth, we have winter, spring, summer, fall - gawd damn, how to I plant food to eat without it freezing? Argh.

Oh yeah. It's a huge mess and not worth it. Bad idea.

SL, another way around the FTL issue is if we were ale to collapse space time dimensions. Thus our perception of time in transit would be as you have speculated on.
Example,
A star gate that allows travel to another galaxy along a zero distance plane.
If relativity is valid the distance would be covered instantaneously for the traveler but in "normal" time for the non traveler.
Collapsing the dimensions does not imply FTL IMO.....The v of your mass is still restrained by physics as we now them.

This is why I raise objections to the relativity explaination of time dilation. For the observer travelling between two galaxies, the distance between the galaxies collapses to 0 as the traveller approaches c. NOW, what does this MEAN? If the traveller looks behind him, can he see one galaxy full sized and if he looks in front of him, he sees the other galaxy full sized? What is meant by full sized? The traveller sees the galaxy cross section area take up the entire area of his viewing window. Imagine the ecliptic plane of each galaxy to be perpendicular to the direction of motion of the traveller.

QQ,

Well that dosen't help. I want to get anywhere in the galaxy in "normal" time. I want to go on holiday 30000ly away in say, a week, spend a week sightseeing, and come back to earth where only three weeks have passed.

So, how do we take spacetime and fold it such that two vastly seperated sets of coordinates in R4 spacetime are right next to each other? I am so pissed off at the universe.

QQ,

Well that dosen't help. I want to get anywhere in the galaxy in "normal" time. I want to go on holiday 30000ly away in say, a week, spend a week sightseeing, and come back to earth where only three weeks have passed.

So, how do we take spacetime and fold it such that two vastly seperated sets of coordinates in R4 spacetime are right next to each other? I am so pissed off at the universe.

the probolem is the right next to each other bit.....to collapse a dimension so that the two co-ordinates are one co-ordinite not two. Two would give you a worm hole I think.
I believe there is a way but it is speculative at best.

Briefly:
If we assume for a moment that matter is vibrating or emmitting EM in a way that is an alternating field and both objects are normally synchronised by nature so that both objects are repelling eg. +/+ we have established three dimensions. However if we sequence the EM so that it is attractive +/- we collapse the spec time dimension to zero.
Say for example two objects emmitt a field that is alternating + to (-) at the same rate and sequence so that both emissions are always in a state of repelling and non-attractive. This woudl keep the objects away from each other even as their individual gravities attract each other. Three dimension could be the result. By changing the alternating sequence of the EM of our two objects the space between those objects becomes Zero.

Now it is not just a simple exercise in EM in the normal sense as we are talking about the very fundamental of EM sequencing and space time. [ not the EM sequencing we already observe because that is naturally repulsive thus due to resistance to change (inertia) delivers energy.]

The difficulty I see is how to selectively target a given object in a universe full of objects.
I have a link to a concept web page

http://www.ozziesnaps.com/higgs.htm
Might be worth a look just for fun....

Aer:

This is why I raise objections to the relativity explaination of time dilation. For the observer travelling between two galaxies, the distance between the galaxies collapses to 0 as the traveller approaches c. NOW, what does this MEAN? If the traveller looks behind him, can he see one galaxy full sized and if he looks in front of him, he sees the other galaxy full sized? What is meant by full sized? The traveller sees the galaxy cross section area take up the entire area of his viewing window. Imagine the ecliptic plane of each galaxy to be perpendicular to the direction of motion of the traveller.

Actually, at close to light speed, there is a relativistic abberation effect, whereby all the light seems to fall within a cone in front of the observer. Everything behind the traveller is completely black, but the traveller can see objects that are behind him in his forward field of view. Objects behind and to the sides look distorted, though - more distortion the further you look away from dead ahead. Then there are the Doppler effects as well...

A radio signal for example is an amplification of a naturally occuring EM sequence. But not a resequencing or reconfiguration of that EM.......

It would be nice (for interstellar travel purposes) if light speed were a few million times larger.
But, we'd still have travel problems because of the fuel issue.

Perhaps we could engineer ourselves into much lighter bodies, and reduce our dependence on heavy life support (food, water, oxygen, shelter)? Improving resistance to acceleration and radiation (starlight turns pretty nasty when highly blue-shifted) would also be helpful.

Actually long before we ever achieve intersteller travel we will have sucessfully achieved control over the brain and just as in the movies you will be able to sign up for a trip and experience years of space exploration in a mere matter of a few minutes of real life time.

It would be like a vivid but coherent dream.

But I want to actually go. Not watch a brain movie.

I think we're stuck.

QQ,

So, how do we take spacetime and fold it such that two vastly seperated sets of coordinates in R4 spacetime are right next to each other? I am so pissed off at the universe.
Keeping in mind that space is essentially a zero dimension as it is, all we would have to do is identify the unique EM signature of the destination and collapse the space between it and the object to be moved.

Space would still be zero dimensional and the distance dimension between two points would be collapsed so that the distance would be zero. Normal space would remain uneffected. [because it is already zero dimensional] It is only the dimensions between two objects of mass that is 3 dimensional and not the space itself. The EM field creating the distance. [repelling]

Actually, at close to light speed, there is a relativistic abberation effect, whereby all the light seems to fall within a cone in front of the observer. Everything behind the traveller is completely black, but the traveller can see objects that are behind him in his forward field of view. Objects behind and to the sides look distorted, though - more distortion the further you look away from dead ahead. Then there are the Doppler effects as well...
Yes, I've seen a movie that demonstrates this. I am not satisfied.

Also:
Everything behind the traveller is completely black What happens to the photons that hit the observer from behind? The observer is not going -the speed of light- so photons still will hit. What is the detailed, no bullshit, explaination for why this appears black?

Actually long before we ever achieve intersteller travel we will have sucessfully achieved control over the brain and just as in the movies you will be able to sign up for a trip and experience years of space exploration in a mere matter of a few minutes of real life time.

It would be like a vivid but coherent dream. You must be a time traveller from the future. Tell me, how does everything turn out?

But I want to actually go. Not watch a brain movie.

I think we're stuck.

Me too. But I have never gotten my inertial drives to reach breakeven. :D

Aer:

Yes, I've seen a movie that demonstrates this. I am not satisfied.

What do you find unsatisfying, in particular?

What happens to the photons that hit the observer from behind? The observer is not going -the speed of light- so photons still will hit. What is the detailed, no bullshit, explaination for why this appears black?

Ok. I wasn't very precise, and I shouldn't have said "completely black". If a photon comes from directly behind, it will be Doppler shifted to the red. For visible light, this means that if you go fast enough, all photons coming from behind you are shifted into the far infrared region of the spectrum, so you can't see them and everything behind you looks black.

As for stuff behind you appearing in your forward field of vision, think about this:

Imagine an archer standing beside a road that you are driving along. At the moment you pull level with him, he shoots his arrow at your car. If he did that, he would miss, because it would take some time for the arrow to move from the bow horizontally to where your car is on the road, and the arrow would fall behind your car.

To hit your car, the archer would need to aim his arrow at some angle in front of the horizontal, so that you would drive into the path of the arrow as it flew.

Now, replace the archer by a light source. Nothing essential changes. You see the archer (the light source) when the arrow (light from the source) hits your car. That happens when you have already gone past the archer (light source). So, you see the archer, even though he is behind you.

James R,

Your detailed analysis is very much appreciated. I was not aware that red-shifting eventuallly shifts into black - I will take your word for it that this is true. What about blue-shifting? Why does a similar effect not occur for objects in the front view?

As for the objects behind you appearing in your forward view - I was not questioning that portion.

Your detailed analysis is very much appreciated. I was not aware that red-shifting eventuallly shifts into black - I will take your word for it that this is true. What about blue-shifting? Why does a similar effect not occur for objects in the front view?

It does.

Objects in the front view have a blue shift. The faster you go, the bigger the shift. So, visible light from the front gets shifted into the UV part of the spectrum, then x-rays, then gamma rays, depending on your speed.

This is one problem to overcome if we ever plan to launch spaceships which travel at close to the speed of light, because nobody would particularly enjoy being irradiated with gamma rays for the whole trip.

So then, as we approach c, when we look backward from whence we came, we see nothing and when we look forward to where we destined ourselves, we see nothing. How do we know we have not veered off course?

Can we not just detect these rays with something other than our eyes and use computers to produce a visual by correcting for red/blue shift?

We are back to the original question. Do we see each galaxy full sized as the distance between them approaches 0 due to our speed?

Can we not just detect these rays with something other than our eyes and use computers to produce a visual by correcting for red/blue shift?

Yes.

We are back to the original question. Do we see each galaxy full sized as the distance between them approaches 0 due to our speed?

Depends what you mean by "full sized".

If you're asking whether you see a galaxy the same way when you're going at high speed as you do when you're going slowly, the answer should be obvious by now.

But maybe you're asking about something else..?

Depends what you mean by "full sized".

What is meant by full sized? The traveller sees the galaxy cross section area take up the entire area of his viewing window.

You may have to change "viewing window" to "viewing monitor" if the computer has to correct for red/blue shifting. However, we are not considering any zooming.

Ok then. Using your definition...

If the galaxy is not "full sized" when the spaceship is stationary at a particular point, then it will not be full sized when the spaceship is moving, either.

If it is full sized when the spaceship is stationary at a particular location, then it would be less than full sized if the spaceship was moving at the same location.

That sounds like a very good explaination - an explaination I would use in fact.

How does this explaination agree with the fact that length contracts to 0 between the two galaxies according to our very fast spaceship? Remember that the galaxy cross-section size does not contract as the ecliptic planes are both perpendicular to our direction of travel (I specified this earlier in the thread).

This is a variation of the rocket leaving Earth effect. As the rocket accelerates from Earth, the distance contracts to 0 as the rocket approaches c - so how does the rocket prove it has moved any distance from Earth? And how would the Earth's size appear according to the rocket's POV?

Aer:

How does this explaination agree with the fact that length contracts to 0 between the two galaxies according to our very fast spaceship?

The distance never contracts to zero, of course, but you can get arbitrarily close to that.

Remember that the galaxy cross-section size does not contract as the ecliptic planes are both perpendicular to our direction of travel (I specified this earlier in the thread).

The "actual" cross-sectional size doesn't change, but how it looks changes a lot, due to abberation, as explained above. If you're going almost the speed of light, then the galaxy ahead will look like a small point on your windshield.

This is a variation of the rocket leaving Earth effect. As the rocket accelerates from Earth, the distance contracts to 0 as the rocket approaches c - so how does the rocket prove it has moved any distance from Earth? And how would the Earth's size appear according to the rocket's POV?

If you looked out the back of the rocket as it accelerated away from earth, what you would see would be the Earth first appearing to get closer to the rocket, then an intermediate period of moving away, then getting closer again as you got even faster, although by that stage abberation and red-shift would mean you wouldn't see anything out the back.

The distance never contracts to zero, of course, but you can get arbitrarily close to that. Of course, I was just getting tired of typing approximately. maybe I'll use approx.



The "actual" cross-sectional size doesn't change, but how it looks changes a lot, due to abberation, as explained above. If you're going almost the speed of light, then the galaxy ahead will look like a small point on your windshield. So if we appear to smack into a speck of dust, it could really be a massive star, neat. :bugeye:




If you looked out the back of the rocket as it accelerated away from earth, what you would see would be the Earth first appearing to get closer to the rocket, then an intermediate period of moving away, then getting closer again as you got even faster, although by that stage abberation and red-shift would mean you wouldn't see anything out the back.Let me get this straight:
We are on Earth with our rocket ready for launch and:
you would see would be the Earth first appearing to get closer
So Earth smacks into us damaging our rocket and we asplode. That's not cool.

Not quite. The rocket launches, leaving the Earth behind. Then, assuming the acceleration is constant, the Earth behind starts to look as if it is getting closer to the rocket (looks like the the rocket is flying backwards). As speed continues to increase, the Earth once again falls behind.

It's much more complicated than one would imagine from "common sense", but it all falls out of the maths.

Not quite. The rocket launches, leaving the Earth behind. Then, assuming the acceleration is constant, the Earth behind starts to look as if it is getting closer to the rocket (looks like the the rocket is flying backwards). As speed continues to increase, the Earth once again falls behind.

It's much more complicated than one would imagine from "common sense", but it all falls out of the maths.
Yes, I am very aware that we are not applying common sense here - I've never seen a rocket reach .999999c :D

However, I still raise objection to the length contraction concept as it has never been observed directly.

Would the size of the Earth ever become considerably smaller as visualized through red-shift correction and according to the length contraction distance between the Earth and destination shrinking to approximately 0?

However, I still raise objection to the length contraction concept as it has never been observed directly.

That's not much of an objection, unless you can give some reason as to why it shouldn't occur, given all the other relativistic effects which have been confirmed, and given that relativity breaks down without length contraction.

Would the size of the Earth ever become considerably smaller as visualized through red-shift correction and according to the length contraction distance between the Earth and destination shrinking to approximately 0?

You say "become considerably smaller". Do you mean "look smaller"?

Red-shift doesn't change the apparent size of anything, only the colour. Abberation would make the Earth's shape look distorted, so the earth would appear on both sides of the field of view rather than directly behind.

Why do you ask?

Not quite. The rocket launches, leaving the Earth behind. Then, assuming the acceleration is constant, the Earth behind starts to look as if it is getting closer to the rocket (looks like the the rocket is flying backwards). As speed continues to increase, the Earth once again falls behind.

This is interesting. I seem to recall pointing out in a thread I started about the affects of STR meaning the faster you receeded from something the closer it would appear to become and you called me a crackpot.

Are you now becoming a crackpot? Or was I right after all? :D

I think you have a bad memory for past conversations, MacM.

I think you have a bad memory for past conversations, MacM.

And I think you deliberately distort facts.

The thread is called "Arguement for a Decellerating Expansion of the Universe."

I also raised the issue of spatial contraction producing an apparent FTL change in distance due to the same affect of the earth moving closer due to spatial contraction as you receeded from it at relavistic speeds.

To that you asserted you would not see the changing distance. But now you tell somebody else you would.

It seems my memory is much better than yours.

That's not much of an objection, unless you can give some reason as to why it shouldn't occur, given all the other relativistic effects which have been confirmed, and given that relativity breaks down without length contraction. The objection is raised to the special relativity explaination. By objecting, I am not saying that it is definately wrong - only that it could be wrong. I do no know of an experiment that has been performed to test special relativity that would not yield the same results if a local ether was considered. Yet - a local ether does not predict length contraction.



You say "become considerably smaller". Do you mean "look smaller"?
Yes I did say that BECAUSE, what does it mean for the distance to contract to 0 then? I do not care about abberration effects here. That is just a complication of the issue. Are you saying that length contraction is also an abberration? Is time dilation an abberration? I don't think so...


Red-shift doesn't change the apparent size of anything, only the colour. I know this, but we have to correct the red-shift to be able to see anything.

Abberation would make the Earth's shape look distorted, so the earth would appear on both sides of the field of view rather than directly behind. Are you sure this is true? I thought only things to the side of you would appear ahead of you as they accually occured behind you. The Earth is never to the side of the spaceship and as such never appears in the front view.


Why do you ask?Because I can?

Aer:

The objection is raised to the special relativity explaination. By objecting, I am not saying that it is definately wrong - only that it could be wrong.

Anything in science could be wrong, potentially.

I do no know of an experiment that has been performed to test special relativity that would not yield the same results if a local ether was considered. Yet - a local ether does not predict length contraction.

Yet you seem reticent to discuss local ether theories. Are you worried that they may not withstand close scrutiny?

Yes I did say that BECAUSE, what does it mean for the distance to contract to 0 then? I do not care about abberration effects here. That is just a complication of the issue. Are you saying that length contraction is also an abberration? Is time dilation an abberration? I don't think so...

As I said to MacM, in this context I think it is easiest to regard spacetime as the "reality". Length contraction and time dilation are effects which are observer-dependent. Each observer sees a different slice of spacetime.

Are you sure this is true? I thought only things to the side of you would appear ahead of you as they accually occured behind you. The Earth is never to the side of the spaceship and as such never appears in the front view.

The Earth is not a point of no size behind the spaceship. It has a finite width. So, some parts of it are to one side or the other of the spaceship.

Yet you seem reticent to discuss local ether theories. Are you worried that they may not withstand close scrutiny?

Actually I would like it to be closely scrutinized. It is not my theory, I am not the one to give a full presentation of the theory in order for it to be closely scrutinized. However, I will try to find papers that deal with the subject if you wish to look over them.



As I said to MacM, in this context I think it is easiest to regard spacetime as the "reality". Length contraction and time dilation are effects which are observer-dependent. Each observer sees a different slice of spacetime.

Wait a minute. Either spacetime is reality or perception. I think that spacetime is defined from the theory to be reality. That means it is not an abberation effect - correct? Abberation effects can be corrected for since they have to do with the travel distance and time of photons.



The Earth is not a point of no size behind the spaceship. It has a finite width. So, some parts of it are to one side or the other of the spaceship.
What is defined as "to the side". Direction wise, the Earth is behind the ship and to the side both ways. But any part of the Earth is never directly to the side of the ship. Only objects that exist at some point in time directly to the side of the ship produce the abberation effect of being in front as they should have appeared when they were behind, correct?

Only objects that exist at some point in time directly to the side of the ship produce the abberation effect of being in front as they should have appeared when they were behind, correct?

No. The closer the ship travels to the speed of light, the more light from "behind" appears in the front field of view. "To the side" in this context doesn't just mean at 90 degrees to the direction of travel. It can mean at 170 degrees or more, if you're going fast enough.

No. The closer the ship travels to the speed of light, the more light from "behind" appears in the front field of view. "To the side" in this context doesn't just mean at 90 degrees to the direction of travel. It can mean at 170 degrees or more, if you're going fast enough.

OK - again, this is just an aberration effect from photons from the Earth traveling in a direction non-parallel to the direction of travel of the spaceship, since the spaceship is moving faster in the x direction than the x-component of the light, correct? We would still be able to see the photons hitting from directly behind as well, would we not? If that is the case (I don't see why not), then can we only consider these photons hitting from behind to make our measurements?

Basically, I want to know - is length contraction a reality or an aberration effect? What I mean by "know" is I want to find out your opinion. It seems clear to me that length contraction as defined in special relativity would have to be a real effect just as time dilation is a real effect.

OK - again, this is just an aberration effect from photons from the Earth traveling in a direction non-parallel to the direction of travel of the spaceship, since the spaceship is moving faster in the x direction than the x-component of the light, correct?

Yes.

We would still be able to see the photons hitting from directly behind as well, would we not?

In principle, yes, though they will be severely red-shifted.

If that is the case (I don't see why not), then can we only consider these photons hitting from behind to make our measurements?

Measurements of what?

Basically, I want to know - is length contraction a reality or an aberration effect?

It's a reality. But all it is saying is that observers in relative motion measure different lengths to those who are in the rest frame.

It seems clear to me that length contraction as defined in special relativity would have to be a real effect just as time dilation is a real effect.

Certainly, length contraction is as real as time dilation.

James,

I think, those who refuse to accept length contraction have a notion that 'reality' as an absolute. Their failure to understand that reality, as shown by SR, is a relative one (depends on their position & path in space-time) is what that leads to all these denials.

Correct me if i am wrong in the description :

Length contraction :

is a reality for a frame Xi,
that occurs in another moving frame Yj (relative velocity Vij between Xi & Yj > 0),
as a result of difference in proper lengths of Xi & Yj that is enforced by space-time geometry for any 2 different world lines.

where i = 1,2,3.... & j = 1,2,3...

Imagine a future in which human consciousness no longer resides in a biological package. It sounds to me like you're suggesting sending out computers/robots to colonize the galaxy, rather than people. If you're sending a machine, obviously having to wait around in space for a long time wouldn't be a problem.

I'm talking about transferring human consciousness into non-biological entities. Not computers or robots. Entities with the non-biological equivalent of brains like ours. Only better. In which you can slow down your perception of time if you choose (among other interesting things).

Imagine this:

A segment of the human race decides to go exploring the galaxy. The best speed we reasonably can reach is 0.5c. We build large O'Neill type colonies with this speed capability. Once in transit, a trip to the center of the galaxy might take 50,000 years of subjective time. This population of non-biological humans may decide to slow their perception of time passage by a factor of say, 100,000 (or more) so that the trip will seem to them to take only 6 months or less.

Unless we can alter our psyche's such that 50,000 years seems like a stroll in the park, then I think this is what we would do. Once there we could drop back to "normal" time and explore. Then travel some more.

I think the limit of 'c' is a problem of perception only. Change your perception and nifty things become possible.

why not just simply spend the trip unconscious on life support for 50,000 years, then it would appear instantaneous....? certainly easier to do than create mechanical brains with a speed stat....

If we had no perception of light - say humans evolved without eyes but we had ears. We would live in darkness with no idea what made us warm during the day, ie no knowledge of electromagnetic waves.

We would surely use our perception of sound - we could hear people and events happening around us. We could derive some sort of system using sound - how long it takes sound to travel a certain distance etc.

In this light-deprived world, a crackpot emerges and claims:

"I CAN TRAVEL FASTER THAN SOUND!"

Scientists would say that this is impossible! "Nothing can travel faster than sound! because as soon as something travels that fast we cannot hear it anymore, our devices for detecting sound emanating from that object would cease detecting that object."

The doppler effect would in a rough analogy substitute for the red shift effect. As an object approaches the sound barrier our sound-detecting devices notice the doppler shift and we would conclude that faster than sound travel is impossible because that object would cease to exist - by detection of any sort of device.

So the crackpot builds a jet and travels faster than sound. (Just say somehow they built a jet without electronics (a whip could also substitute as an object that could travel faster than sound)).

"I CAN TRAVEL FASTER THAN SOUND!"

Scientists would say that this is impossible!
You laugh, but it was in fact once proposed that it would be impossible to fly at speeds faster than sound.

However, this is a lot different than the light speed barrier. The problem that arose with supersonic flight had to do with shock waves and turbulance. This is still a problem today, an aircraft that flies at Mach 1 will have a white envelope develop around it, but this envelope goes away once the aircraft is flying faster than Mach 1.

First of all, I understand that my "story" is A LOT different than faster than light travel. Im not claiming anything - I am merely trying to point out some interesting ideas.

Secondly, let me pose a few questions.

How would you propose to detect an object travelling faster than sound using only sound waves and instruments based on sound waves?

How would you propose to detect an object travelling faster than light using devices based upon the theories of electromagnetic waves?

You would run into problems trying to detect a supersonic jet using sound. I believe in much the same way we have problems trying to deal with faster than light travel. IF faster than light travel IS possible, then we will not be able to appreciate it unless we find some alternative method of measurement which does not involve electromagnetic waves.

How would you propose to detect an object travelling faster than sound using only sound waves and instruments based on sound waves?

OK, so we want to detect objects moving faster than the speed of sound. First of all, we must clearly state what the speed of sound is. Unlike the speed of light, the speed of sound wave propagation can vary. The speed of sound, a, is given by the following equation:

a = sqrt(γ R T)

where γ is the specific heat ratio, R is the universal gas constant, and T is the temperature. I am going to assume we are dealing with measurements within the Earth's atmosphere (sound doesn't travel through vacuum). So γ and R are constant for air, 1.4 and 287 J/(kg K) respectively. Therefore we see that the speed of sound in air only varies with the temperature of the air. We could go into an analysis of why this is, but I don't think that is necessary - you only need to know that the speed of sound varies with the square root of the temperature.

Now that we know what the speed of sound is, we need to know how to measure sound waves. Sound waves are commonly thought of as vibrations in the air. However this is too vague for our purposes here. Fundamentally, sound waves are caused by pressure variations which make the particles in the air compress and decompress together as the wave propagates. So to measure these sound waves, we need to measure pressure changes.

Now, for an object traveling at the speed of sound or greater, it will create a shock wave. Shock waves produce a pressure drop behind them and the drop in pressure is proportional to the Mach speed (Mach 1 = speed of sound, Mach 2 = twice the speed of sound, etc). so if our pressure measuring devices detect such a pressure drop, then the speed can be determined.



How would you propose to detect an object travelling faster than light using devices based upon the theories of electromagnetic waves?

Well, we can't use any fundamentals from above, becuase as I said and you acknowledged, exceeding the speed of light is an entirely different problem. What an object would do when exceeding the speed of light cannot be known because we don't even know if it is possible (in fact it is almost certain that it is not possible).


You would run into problems trying to detect a supersonic jet using sound. I think I outlined a way to do it. I don't think there is anything I am overlooking - it should work.


I believe in much the same way we have problems trying to deal with faster than light travel. IF faster than light travel IS possible, then we will not be able to appreciate it unless we find some alternative method of measurement which does not involve electromagnetic waves.

Well if the object was approaching us head on faster than the speed of light, I suspect we wouldn't be able to see it until it passes by us. But that is assuming such an idea is even plausible.

How would you propose to detect an object travelling faster than sound using only sound waves and instruments based on sound waves?Well, the fact that you couldn't hear it approaching (only receding away from you) would be a pretty big clue..

If you wanted to know the exact velocity you could just set up two separate observers with synchronized clocks, then have the supersonic object pass by them. They both record the time at which the object passes. Since you know the distance between the observers and how long it took the object to pass by, it should be easy to figure out its speed.
How would you propose to detect an object travelling faster than light using devices based upon the theories of electromagnetic waves?Set up a laser shining on a detector that can record when the beam is blocked. Set up another one a known distance away. Send an object through both detectors. This will allow you to figure out the velocity of the object. I don't see what's supposed to be complicated about this?

Of course, with modern equipment you would need to FTL object to be pretty long in order for it to block the beam long enough to detect it.

Well, the fact that you couldn't hear it approaching (only receding away from you) would be a pretty big clue.. Actually, you'd have the same problem after it passes. Basically there would be a jumbled mess of sound waves coming from every direction.

If you wanted to know the exact velocity you could just set up two separate observers with synchronized clocks, then have the supersonic object pass by them. They both record the time at which the object passes. Since you know the distance between the observers and how long it took the object to pass by, it should be easy to figure out its speed.Set up a laser shining on a detector that can record when the beam is blocked. Set up another one a known distance away. Send an object through both detectors. This will allow you to figure out the velocity of the object. I don't see what's supposed to be complicated about this? What if we cannot detect the object travelling? It most likely is not going to be matter or an electromagnetic wave. If anything can travel faster than the speed of light, it is probably an exotic object/concept we haven't conceived of.

I'm talking about transferring human consciousness into non-biological entities. Not computers or robots. Entities with the non-biological equivalent of brains like ours. Only better. In which you can slow down your perception of time if you choose (among other interesting things).I would question whether or not such a thing would really be a human. It sounds to me like a machine that merely thinks like a person.

Even if you could somehow scan your brain and “download” all the information into a computer (or “nonbiological brain”, whatever you want to call it) that would have all of your memories and think just like you, I would argue that such a construct wouldn’t actually be you. It would be a wholly separate entity that thought like you, but was still a distinctly separate person/consciousness/machine/whatever.

Even if you could somehow scan your brain and “download” all the information into a computer (or “nonbiological brain”, whatever you want to call it) that would have all of your memories and think just like you, I would argue that such a construct wouldn’t actually be you. It would be a wholly separate entity that thought like you, but was still a distinctly separate person/consciousness/machine/whatever.
Do not spoil my plans on becoming immortal :m: :D

Please help me understand this link

http://www.scienceblog.com/light.html

http://www.scienceblog.com/light.html

Well, I do not know about the methods they used as it hasn't been published yet.

But it appears from reading the article that they've slowed down light, which has already been done.

And they've made a portion of light travel faster than c. Now the article doesn't specify what this "portion of light" is. However, phase velocities have already been measured faster than c. But these phase velocities are always one part of a so called "group velocity" and the group velocity is always measured as less than c. So when they say "a portion of light travels faster than c" - it sounds like the same old phase velocity measurement.

They don't talk about the speeding up part at all. I suspect they were able to speed it up wrt the natural speed in the glass fiber (but not faster than 'c' in vacuo) and the reporter isn't being clear or dosen't understand that.

Nasor:

I would question whether or not such a thing would really be a human. It sounds to me like a machine that merely thinks like a person.

Even if you could somehow scan your brain and “download” all the information into a computer (or “nonbiological brain”, whatever you want to call it) that would have all of your memories and think just like you, I would argue that such a construct wouldn’t actually be you. It would be a wholly separate entity that thought like you, but was still a distinctly separate person/consciousness/machine/whatever.
I would disagree. If the replica was accurate enough, and the transfer of brain functions took place under your control (i.e. remapping until you couldn't tell the difference between your brain and the replica) then it would be "you".

Here is a thread that discusses this idea:

http://www.sciforums.com/showthread.php?t=44011

Philosophy of Personal Identity (http://plato.stanford.edu/entries/identity-personal/)

No easy answers.

I personally suspect that personal identity is an illusion caused by the lack of situations such as those described in various thought experiments like super's.
I suspect that I am very similar to, but not the same as, the person I was yesterday - that my identity does not continue, but continually changes.

I agree. No easy answers. It's one of those questions that keeps poking at me though. There's something mysterious about consciousness...

I've got to stop that habit of adding extended afterthoughts to my posts!

I also agree that from day-to-day I am subtly different, but the sense of continuity maintains the illusion. Maybe that's all identity is. A set of memories and, more importantly, a sense of uninterrupted continuity. Redundant, yes I know.

I suspect that I am very similar to, but not the same as, the person I was yesterday - that my identity does not continue, but continually changes.
You say a new identity replaces your old idenity. I say your identity changed from a former state to a new state. Really, what is the difference? You have an identity - stubborn SR loyalist. If this identity slightly changed in the future - I wouldn't be so stupid as to not be able to recognize who you are. Maybe your mind cannot hold enough information to remember your past identities? I know I remember my past identities to an extent..

I also agree that from day-to-day I am subtly different, but the sense of continuity maintains the illusion. Maybe that's all identity is. A set of memories and, more importantly, a sense of uninterrupted continuity. Redundant, yes I know. So coma patients whom awake and retain all of their memories have a new identity? As far as I know, they pick up where they left off which is a discontinuity to us, but still a continuity to them.

Did I say that? I mean continuity for the person. Yes. Coma patients still have continuity therefore the same identity. Amnesia patients lose the criteria I posted above

"A set of memories and, more importantly, a sense of uninterrupted continuity."

I'm not even entirely sure the continuity argument is necessary. An amnesia patient loses memories which alters there identity since they cannot remember who they are. The continuity you speak of is merely a retention of memories IMO.

Same thing happens with alzheimer's. They lose memories and as a result they lose parts of their identity until it is all gone. Perhaps the discontinuity is within their memories and not the passage of time immediately before to present.

I agree. I withdraw the continuity requirement.

You say a new identity replaces your old idenity. I say your identity changed from a former state to a new state. Really, what is the difference? You have an identity - stubborn SR loyalist. If this identity slightly changed in the future - I wouldn't be so stupid as to not be able to recognize who you are. Maybe your mind cannot hold enough information to remember your past identities? I know I remember my past identities to an extent..
This is a "small change" problem.

When a whole lot of small changes lead to a complete change... when did the change occur?

An analogy:
When, precisely, does a new species appear?
There is a continuous set of parent-child relationships between every pair of living things on the planet. It seems insupportable to suggest that a two parents of one species can have offspring of a different species... so where are the boundaries?

If a boundary can not be precisely located, does that mean a boundary doesn't exist?

I would suggest a fuzzy "diffusion" region instead of a sharp boundary.

This is a "small change" problem.

When a whole lot of small changes lead to a complete change... when did the change occur?

An analogy:
When, precisely, does a new species appear?
I'm probably the worst person to ask when it comes to biology, but as far as I know, new species evolve into what you would call a "new species" when their environment suddenly and extremely changes. Some will adapt, a lot will die, the strongest survive and that is that.


There is a continuous set of parent-child relationships between every pair of living things on the planet. It seems insupportable to suggest that a two parents of one species can have offspring of a different species... so where are the boundaries? You are looking at this incorrectly. The gradual change of species does not happen that way. Like I said, as far as I know, only sudden changes tend to happen - otherwise, the species is diverse with many different appearances, much like humans.



If a boundary can not be precisely located, does that mean a boundary doesn't exist? I believe the boundary is set by environmental conditions.

On a marginally related note, I think that "humanity", like "identity", is also a fuzzy-edged region on a number of continuums.

Consider: "Humanity" has no well-accepted objective definition - in practice, it is defined by the set of its members... a circular, subjective definition: "Humanity is the set of entities which are recognized as human".

This is potentially a problem, because there is no resolution to debates over boundary conditions. If one person recognizes an entity as human, but another person doesn't, there is no standard by which to resolve their difference.

Currently, there are few entities which fall into the boundary areas, with the notable exception of fetuses/embryos/fertilized ova/unborn children. However, this may (will?) change in the future. If/when the existence of entities such as cyborgs, androids, human clones, enhanced animals, and artifical intelligences is realised, it seems pretty obvious that there will be debates over their humanity that will be as unresolvable as the abortion debate.

Go to the philosophy forum. All I read above is mublem quuak wwank doodle do tew moo..

Aer,

You are talking about gradualism vs "punctuated equilibrium" in evolutionary terms, I believe. The first states that speciation is a gradual (duh), continuous process of extremely small changes leading, over time, to adaptations to slowly varying environments. The other is like you said. Things go along in "equilibrium" until some heinous environmental change "punctuates" the situation forcing rapid "survival of the fittest" competition. I expect it is a balance between the two ideas.

I believe the boundary is set by environmental conditions.
I think you're taking punctuated equilibrium a bit too far, but that's a topic for another forum.

Perhaps a different analogy...

Do you agree that "Youth" and "Old Age" are recognizable states?

When does youth end?

When does old age begin?

Does the lack of a precise boundary mean that a boundary doesn't exist?

I thought Petes post made sense, but I'm still laughing my ass off at:

"mublem quuak wwank doodle do tew moo.. " (it's late here...)

:D :m:

Hey Pete - I beat ya by 2 minutes!

I guess the balance is what I refered to as diversity.

There is also the situation of mutual evolution between two entirely different species. That is they evolve together to depend on each other. I believe tropical hummingbirds and some plant species are a prime example. The hummingbirds only feed from a specific plant and that plant only gets pollinated from the hummingbird.

Yep. Coevolution. Happens all the time.

I think you're taking punctuated equilibrium a bit too far, but that's a topic for another forum.

Perhaps a different analogy...

Do you agree that "Youth" and "Old Age" are recognizable states?

When does youth end?When new hair in new areas appears.

When does old age begin?When gray hairs start to grow.

What grade are we in?

Does the lack of a precise boundary mean that a boundary doesn't exist?
What is wrong with the boundaries I set.

Go to the philosophy forum. All I read above is mublem quuak wwank doodle do tew moo..
You're very opinionated for such an illiterate, lazy soul.

You may think:
I think you're taking punctuated equilibrium a bit too far, but that's a topic for another forum.
But I don't think I am. If there is nothing to spur change, then why will something change? But forget that question. The reason I stated what I did is because I have a vague recollection of hearing something along the lines that the evidence that exists in the fossil records agrees with rapid evolutionary change followed by long sustained nonevolution.

And as I stated, my source is the deep crevises of my memory.

You're very opinionated for such an illiterate, lazy soul.
At least SL understood the nature of my post :D

What is wrong with the boundaries I set.
They're not precisely defined or well-accepted. Try again.

I think they are precisely defined. I will not try again.

Just because they vary from person to person? I can accept that no one person is exactly like another.

There's a flower that has a pistil that looks just like the hot ass end of a female wasp or bee or something (can't remember) and the bug goes and humps it, thus getting pollen from plant to plant.

...But I don't think I am.
Why don't you go and find out? The necessary knowledge is out there for the reading!

I think they are precisely defined.
You do?
You think that every person with a single pubic hair is not "youth"?
You think that every person with a single grey hair is in "old age", and that anyone with a gray hair is not?

I think you're just being argumentative.

Why don't you go and find out? Because I am not really much interested to know.

Aer,

Your boundaries are arbitrary and vary greatly from individual to individual.

There's a flower that has a pistil that looks just like the hot ass end of a female wasp or bee or something (can't remember) and the bug goes and humps it, thus getting pollen from plant to plant.
Richard Dawkins is great for this stuff. Fig wasps are way cool.

Because I am not really much interested to know.
Then why pretend that you know what you're talking about?

If we hold him down, we can FORCE him to learn! Mwahahah!

I know.

Just because they vary from person to person? I can accept that no one person is exactly like another.

Evolution varies greatly from specy to specy. :cool:

Then why pretend that you know what you're talking about?



I'm probably the worst person to ask when it comes to biology, but as far as I know, new species evolve into what you would call a "new species" when their environment suddenly and extremely changes. Some will adapt, a lot will die, the strongest survive and that is that.

I was just giving my 2 cents. Which I think is a bargain.

Interaction of fig wasps and fig trees (http://www.figweb.org/Interaction/index.htm)

Yeah. Fig wasps are very cool. And here's the one I was talking about:

Orchid Flowers in the genus Ophrys probably have elaborate disguises which lure insects into mating with them. Their flowers resemble insect females.

Males are attracted to them and try to mate with them. In their frenzy to copulate with the female surrogate, they pick up specialized pollen sacks called Pollinia and transfer them to the next Ophrys they visit. One species mimics a small wasp while another resembles a bumble-bee queen.

Source: (about halfway down the page - pictures)
http://www.botany.hawaii.edu/faculty/webb/BOT311/BOT311-00/anthophyta_significant_life_cycl.htm

Maybe the insect knows that it just a blow up doll/flower it is mating with but doesn't really care? :m: