This is all true(or at least the theories say it’s true) but recently certain theories have come to the fore - one gem talks about how light may actually get slowed down due to occurrences of matter in the vacuum of space. Just a little thought.

My problem with science fiction (which touches on this subject a lot) is that the authors don’t research sciences enough when they put half of this crap in books, tv shows and films (sound effects of explosions in space anyone?).

also, here’s a good one for you (assuming you haven’t heard of this before) - when you approach light speed you gain enough mass to travel faster than light by being smashed into an alternate universe, where our laws of physics don’t exist.

Questions:

What is time? How do you measure it? How do you make it slow down?

Think about the non-Euclidean Geometries: all they had to do was to assume, that one of the basic axioms was wrong, and they discovered alternative worlds, where rules are totally different. And guess what? It turned out that these worlds do exist. In our universe.

Every proof is based on certain axioms. You may say that in physics the axioms are based on real live observations - but how can you possibly be sure, that these observations are comprehensive enough to represent whole universe?

What MA said. But with an extra black swan thrown in for good measure.

Most FTL drives in sci-fi do NOT involve accelerating a ship up to and beyond the speed of light. They involve jumping to some kind of alternate place/layer/dimension/subspace, and using that medium to travel, before popping out in the required location. We know that some ‘other’ dimension exists because these damned particles keep popping briefly out of it (hence the whole ‘alternate universe’ theory people keep banging on about). Whether it can be used to travel at FTL speeds is another matter, but since we haven’t even gone to another PLANET yet, maybe it’s a bit early to start speculating about whether or not it can be used to travel to other star systems.

And YES I realize that being able to get to a destination before the light from the system you left from gets there would cause horrible relativistic time problems, but minds no smaller than Einsteins and Hawkings agreed it would be possible, and they were, about, oh, I don’t know, a gajillion times smarter than we.

I can still remember sitting in my Higher Maths class towards the end of term, discussing this with our teacher.

What happens if light is grey, instead of black and white?

Maybe one day we WILL, that’s not speculation, that’s optimism. A healthy dose of which may be a good thing for the ‘scientist’. A ‘can do’ attitude and all that.

Anyway, remember when the world was flat… what a hoot that was, eh!

What about wormholes? They are perfectly accepted by scientists, including Einstein and Hawking, as a method of travelling vast distances across space-time at speeds far in excess of the speed of light. Granted, you would be travelling at sub-lightspeed whilst in the wormhole, but the distances travelled would mean relativistically (?) you were travelling faster than light, albeit through a shortcut.

The whole ‘alternative universe’ theory is not theory, as fiction.

That’s bollocks. It’s an extremely well-regard theory, because there isn’t currently any other explanation where these particles are coming from that doesn’t disobey the law of thermodynamics. If fermions can cross over (albeit briefly, but observably), it’s not UNTHINKABLE that larger particles can also cross over.

It’s not that you get to the destination before the light from the system you left gets there, it’s that you get to a destination before you yourself have left the system you left from gets there.

Can I leave this sentence before it gets there?

So what you’re saying is: Einstein and Hawking = wrong. You = right. And your nobel prize is where?

I never said ‘exceed the speed of light’, in fact I clarified that I wasn’t saying that! I said: Disappear from one point in the universe and appear at another point in the universe before the light from the first point reaches the second. This doesn’t, actually, cause any unsolvable relativistic problems (like sending a message to yourself telling yourself not to go in the first place), although it does create problems. All you’d need is an Einstein-Rosen Bridge, which has never actually been dismissed as a possibility- in fact, it makes mathematical sense, which is why it’s considered a theory at all.

In other words: Will we ever be able to make FTL jumps? Certainly not with your attitude.

Black swans 4tw. cough Sorry.

Nobody is disagreeing with the statement that you can’t simply accelerate until you’re going faster than c. However there are a couple of other things that - while clearly not probable - don’t seem impossible under the current system (or at the very least, haven’t been demonstrated as such to this audience - perhaps more proof is in order).

You’re arguing absolutes, and only a Sith Lord logician deals in absolutes. You are reasoning with a system that is only related to the one we are discussing by convention, and I get the impression that at times you’re not giving that fact its due. We’re rapidly getting back to that discussion about scientific discussion being like proselytisation.

I would like to hear the proof that causality absolutely cannot be breached, though. That may be the way to get Dan to leave you alone…

Well, for starters the Bajoran wornhole went to the GAMMA quadrant, not the Delta quadrant (you must be thinking the Barzan wormhole, which did not have a fixed exit/entry point, but moved through the universe), and since it was powered by aliens on another plane of existence, I don’t think regular phsyics apply to them- the Prophets lived outside the regular stream of time.

You can’t argue against alt. universe theory by using string theory, since they’re both equally unproven!

Please outline how one would use a FTL jump to break causality. It’s already been demonstrated that you could NOT use an FTL jump to send information backwards to prevent yourself from making the original jump, which was Einstein’s main problem with causality. If you were to accelerate to light-plus speeds, relativity would certainly have some extremely bizarre effects, but we’ve already agreed that kind of acceleration is impossible. I’m saying what is, Battlestar Galactica-style, I just disappeared from where I am now and ended up twenty light seconds from Earth. It would take 20 seconds for Earth to even know I’d got there. What could I possibly do to break causality?

Sounds fair enough to me. I’ll complain more about causality when I’ve gone and read your reference for closed time-like curves.

Black swans are one of the canonical examples of the problem with philosophical inductivism as a way deducing facts about the real world. In the middle ages, people had noted that they saw only black ravens and white swans. After sufficiently many instances of a swan being white and a raven being black with no instances of either contrary case, they felt confident in assuming that this would always be the case: that all ravens were black, and all swans were white. When European man got to Australia, he found black swans.

Don’t talk down to me, science-boy, I know how relativity works! If you can demonstrate to me how instantaneous travel breaks causality particularly to a third observer, I’ll be very impressed. As will scientists the world over who actually spend their days thinking about exactly this kind of problem.

Relativity says that an events cause must precede it’s effect.

WHAT?!? The “law of cause-and-effect” has never been enshrined by scientists because it’s more of a philosophical issue. Change is entirely subjective in relativistic terms. Einstein himself said there was no reason, if you did travel ‘back’ in time (which FTL travel does not entail!), to think that you couldn’t top your old grand-dad.

The comments are interesting, but I’m trying to come up with an argument as to how I could prove that FTL travel may well be possible, without it being either a “Maybe One Day” argument or an “if I had a time machine I’d show you” argument. It seems to me, as in most scientific theories, that there are many theories that disprove it, and an large number of equally sound theories that also prove it to be entirely possible. Or basically it’s the “you are both right” argument, which you don’t want to hear either, I assume.

And I am also enjoying the argument. Why do you think I read both yours and Dans blogs more than anyone elses? It’s the arguments, you see.

There is Faster Than Light travel. Not of you, me and cars but of small particles like an electron. I remember hearing about it in university. It’s called Quantum Tunneling. If I remember correctly you basically you send an electron against a barrier and with a small probability it pops out on the other side faster than the speed of light. A particle would not be able to do this but a particle wave can. (The particle/wave duality is another assumption to discuss.) Here is a link on the subject.

For larger things such as myself there are some practical problems to solve when travelling at the speed of light. Due to the mass one would travel through universe like a huge magnet attracting planets, light, space stations and other random space goo. Better get those titanium window wipers screwed on. Then take off would take forever. To accelerate to c and surviving it you would have to accelerate for 6 months assuming a human can’t stand no more than 2G of prolonged exposure. Same goes for slowing down.

My bet is on a wormhole or fiddling around with Plank’s constant so that we can experience wave properties too. Pickup line “Let’s walk through a door together?”

I’m also finding the comments very interesting, please continue!

When I first read this post yesterday morning I was going to comment and ask how photons can have energy and momentum when they don’t have any mass (something I never understood amongst all the Physics reading I did during A-levels), but then I saw that a serious and complicated discussion had started instead, so thought I wouldn’t interrupt :-)

“Out of interest, is anyone finding the comments interesting? Is anyone reading the comments? Or is this just me and Dan having an argument?”

All of the above. I’m with Matthew on this one…

Cathy, a photon is usually seen as a wave moving through space very quickly i.e. speed of light. As small particles are assumed to have a duality of wave and particle properties the photon can also be considered as a moving particle which would have kinetic energy (Wk = mv2/2). So if we are observing it as moving (energy) it must also have mass. This is why light bends around big planets. The gravity force attracts the light and alter its initial direction. A resting photon as Adrian said has zero mass and I guess that there is no such thing as a static photon hence zero.

Don’t take my word for it but I think this is how it works, I’ve not had physics in the last 7 years but enjoy bringing it back to life.

With regards to warped spacetime. Yes your right, but spacetime is warped depending on the distribution of mass and energy in it. There is no ether or something like that just is bent when the photons come along. They have to be there for the warping to occur.

Light being unable to escape from black holes was another thing that used to contribute to my confusion (because if it’s affected by gravity it must have mass, right?) until I found out about the curvature of spacetime.

I’m really getting a hankering to go and read some Feynman now (or at least John Gribbin).

Adrian: “You cannot have two laws of physics operating simultaneously in the same space time.”

You are making an assertion based on your limited experience. Even if we knew all the laws governing everything we can observe, by definition your experience is limited in space by a sphere of radius 15 billion light years (as any further space wouldn’t have had enough time for any signal to reach us). How do you know that tomorrow we won’t suddenly pick up a signal from the edge of the visible universe which indicates that there is a region beyond the current radius which has different laws of physics? There may be a different speed of light, or a different number of dimensions, or anything.

The science here is way over my head - but my philosophy of science used to be pretty good.

Absolute statements of ‘we will never’ were frowned upon, because our current understanding (in good science) is always looked on as the current theory, rather than absolutely correct. It can and will be updated as new information comes along. Good theories are those that are liable to testing and being disproved and improved upon. The assumption that our understanding is perfect is faith-based, and faith is the domain of the irrational (using the word technically, rather than pejoratively).

We don’t still think in flat-earth, centre of universe terms, but we may still have assumptions of a similar nature (if not degree) that we haven’t advanced culturally or scientifically enough to be able to cast off.

If you’re striving for scientific accuracy, and a good scientific outlook, don’t have absolute faith in our current equations, models and the like. Newtonian physics was the ‘complete’ model of how things are not that long ago. Our understanding will evolve. Abandoning the idea that it will is unscientific.

I’m greatly enjoying the debate - even if I don’t understand the technicalities of the science you’re discussing.

Tol

Actually the prospect that the universe could have developed in separate ‘bubbles’ with different laws of physics / constants of nature is consistent with certain models of the inflationary theory [which is believed by many to be the best explanation of the large-scale uniformity of the observed universe if we accept the big bang theory as correct (in naive terms, why dies the universe 15 billion light years in one direction look broadly the same as that in 15 billion years in the other direction, even though they are 30 billion years apart? The unevenness which would otherwise have come out of the big bang should still be apparent, as any signal which could ‘smooth’ the unevenness couldn’t have occurred unless these areas were initially much closer together - i.e. we need a period of hyperexpansion to make the big bang model work).]

The attraction of this ‘bubble universe’ theory for many cosmologists is that it doesn’t need any further explanation for why the constants of nature/laws of physics are what they are - in effect it is saying that they are not in any way special, just those that happened to fall out of the process which gave rise to the particular ‘bubble’ we occupy. The only ‘special’ thing about this bubble is that the constants were those that allowed intelligent observers to evolve and ask the question in the first place.

This theory doesn’t require there to be no spacetime outside our particular bubble.

Which brings us neatly back to Black Swans…

The scientific theories that you are talking about, from Newton’s law of universal gravitation to Einstein’s general relativity, presupposes that a sequence of events that have occurred will continue to occur in the future. This is inductive reasoning.

To simplify, observation and experience may tell us that all swans are white. This universal statement will hold true as long as all swans we observe are white. However, the single occurrence of a black swan will falsify this statement.

Similarly, the statement that “nothing can travel faster than the speed of light” would be falsified if or when something is discovered that does travel faster than the speed of light.

You are making an assertion that the science you have learned indicates that the laws of physics apply universally in our universe. This is your white swan. The black swan would be the discovery of something that exists in our universe that obeys a different set of physical laws.

(As you said, trying to explain complexities in simple terms is hard to do and this is a primary school breakdown of the philosophies of Karl Popper)

Incidentally, how does travelling faster than light break causality? If I leave point A at time t and arrive at point B at time t+1 then I am not arriving at my destination before I left. If I am travelling faster than the speed of light, then the light that also left point A at time t will arrive at time t+3.

An observer on point B would at, time t+2, be able to see me both at point A and at point B because the light from point A has not yet reached point B even though I have.

So it would appear that I am at point B before I left point A, even though I haven’t. I am physically only in once place, and that place is in Point B.

If you want to ask how I travelled at the speed of light then I’m going to refer you to a study done in 1994 in a Californian institute which suggested that the idea of a “Warp bubble” a la Star Trek, would be how FTL travel was achieved as it would be used to negate the mass of the object it encompassed. Or something. Didn’t personally have the internet back in those days.

No, Adrian, there is no spoon proof. It’s all theory. There is a lot of empirical evidence to indicate the theories that have been put forward are correct and so far, predictions made by theories - such as that about black holes - indicate that the formulae used are correct. These laws are the white swans. A single observation that does not fit in with these theories is your black swan. The predictions that these theories might indicate that the black swan is unlikely to exist, but they cannot prove that it does not exist.

So, the fi in sci-fi stands for fiction then? ;)

I dunno why I’m commenting here. This is all way over my head. Can’t we talk about cars and women? Yikes, I sound like a Nuts/Zoo reader. I should get out more.

No Adrian, this is the whole point.

Science’s utility is not that it provides proof. Its utility is that it is the only method of reasoning we have found which WORKS.

As in we have been able to deduce certain things from observation and as a result we have been able to develop theories to predict future behaviour which have been accurate. Based on this we have been able to build a technology which is why our scientifically based society has televisions and aeroplanes.

However the whole basis on which the edifice of science rests is FALSIFICATION.

Science can never, and never even tries, to PROVE a theory to be true. What it does do is to prove theories are false. Those theories which remain after the most rigorous of experiments are those which we can believe to be true. However, a true scientist would never say that a theory has been PROVED to be true - there is always another experiment which we can carry out which might, just, provide a different outcome (even if we’ve already done the experiment 10 million times it COULD come out differently next time).

When you say that “The universe must have fundamental laws that govern it.” then this is an assumption which might or might not be true.

A more accurate statement would be “the overwhelming majority of experimental evidence indicates that the universe has, so far, appeared to behave as if it is governed by fundamental laws, and we work on the assumption that it does, while admitting that there is always the possibility that it is entirely capricious and unpredictable”. (That possibility might appear to us to be highly improbable, but that doesn’t make it disappear entirely)

“Why bother?” - because it suits us to, and it’s almost always worked before (unlike praying, say).

Please note that your comment : “if black swans cannot exist in the same universe as white swans because the universe cannot exist in a form with both black and white swans and here is the proof”

is based on an assumption that the model of the universe which you have is correct.

Even something which you can prove mathematically to be true, doesn’t necessarily apply to the universe - there is no guarantee that the universe behaves in a way which is consistent with ANY mathematics (although I’d be happy to bet that it is).

Boo-yah! pwn3d.

I agree with Fer and the Stalker here.

There may well be a system of laws that governs the universe, but the universe isn’t letting us know them. Our only interaction with those laws is through observation of their effects.

Your quest for proof, on the other hand, is resorting to logical deduction and inference. You cannot make logical deductions about anything except logical entities, by the nature of the rules used, and logical entities are always abstract. (The key feature is that you can know everything about a logical entity [usually because you defined it to be so], whereas you can’t justify claiming that you know all about a real-world one)

What is needed is a link between abstract entities and concrete ones, and that’s where the philosophy comes in. In effect, you assume your model is right because you haven’t yet seen it go wrong. Although the argument itself is irrelevant here (and everywhere else, I’m inclined to think), the main point acknowledged by both inductivists and Popperians (and other more obscure persuasions) is that the model can never be proved right, and that the good scientist should always have in the back of his mind that he might later need to fix it or throw it out because a new observation doesn’t fit it.

You say that the value of c has been proven. That’s fair enough; there have been occasions at which man has known the speed of light, under the conditions measured. What if c were a function of time? Knowing the value of something on particular occasions (and I mean not only the times, but all other environmental and experimental variables) doesn’t tell you a great deal about its nature, such as why it evaluates to that and whether it will continue to do so under all conditions. You’ll say it’s incredibly unlikely, and I would agree, but under no circumstances can we - as observers - claim that we’ve proved it can’t be.

I like the idea of these other bubbles. I like the idea of having gateways: devices that know the protocols on both sides so that things can be put onto the right metric/subnet/ values-of-fundamental-constants/etc as they pass from one to the other. I don’t know enough about the ideas involved to comment on how reasonable a thought that is, besides that which is implied by my argument above.

Your logic is well out of whack:

I can say “your white swan is actually black because it’s only a theory you have that it’s really white in the first place”

The Universe must have fundamental laws that govern it

your argument is you can prove nothing

Every argument can be defeated with “you’re all a construct of my imagination anyway and nothing actually exists”.

Boo-yah! pwn3d

A bit like an cross word. As you fill up the cross word you either find earlier answers were wrong and need correction, or they start to prove that latter answers are too correct.

Physics usually leads to philosophy at some point. As science progress we keep pushing this point forward but at the end we just don’t know and the question becomes who are we to understand, are we even meant/capable to understand. Cutting butter with a knife of butter.

What is religion if not a way for people to accept what they don’t understand? Science provides that same comfort, albeit based on reason and empirical proofs, and has some great practical applications that makes life easier. However, how do we as scientist manage beyond the point where we just don’t know? Ideally there is a Theory of Everything, find it, prove it and your done. Last man out turn off the lights. However, until then I guess we’re as much in the dark as anyone else and can only have faith in that our cross-word is correct. -Crap, was that a black swan…naah?

I’m not claiming that the universe doesn’t have fundamental laws. I do however dispute the claim that humans can understand them; because humans can only deduce the laws by observation of their effects, the best we could have is an understanding of a system that we have devised in our belief that it is analogous to the true laws.

Science - and I mean real, concrete science that deals with real things - differs in approach to a religion. Human science is not an absolute though, and it would make little or no progress if everyone believed it to be so.

While progress may possibly be made extrapolating the structure of our science beyond that which we have verified by observation, to do so always carries the risk that we have diverged from the fundamental laws. Beyond that which our observables cover, we have only as much reason to believe in the science as we have faith in its veracity. Yes, I’m talking about theoretical physics. I’m a big fan of Occam’s Razor; if you show me a theory that fits all observables while requiring only a reasonable number of new particles/dimensions/unicorns or other assumptions, then I’ll happily sit back and wait for more observations, to see if it fits. If the model doesn’t allow time travel because that would have required additional particles, an extra dimension and an albino dragon, have we proved that time travel isn’t possible?Of course not, it just makes it very unlikely.

In your crossword analogy, the fundamentals of the universe are a puzzle in which we can only see the middle of the grid. We have the clues for the words in the middle, and we can work out what the next words out are likely to be. We can then guess the next, since they will fit into the ones that we have already estimated. In doing so we assume that our previous deductions are correct, and there’s nothing wrong with that provided we always remain ready to go back and revise them should we gain more clues. And just because we can sometimes find new clues and confirm the words we already guessed, doesn’t mean that the next clue we find isn’t going to point out that in a particular direction the crossword is actually a cross-number, or even a wordsearch.

I’m not arguing against most of the things you believe (in fact I agree with most of them). I’m arguing against the claim that you know them and that humans have proved them.

I do want to hear your take on causality as proof against FTL though :-)

As a trivial aside, according to the Animatrix, the name of the boy with the spoon in the original film was Micheal Karl Popper.

That’s the whole point though Adrian. Any fundamental law we have deduced through the observation of our universe is through inductivism. The only way you can prove anything 100% is to examine every single occurrence. That’s the principle behind falsification.

In the meantime, we are working under assumptions. There’s nothing wrong with this as long as we acknowledge that we are working under an assumption.

Actually, to be fair, you did cover this in your original post.

I’m going to need you to accept two axioms: 1) that the speed of light is contstant… 2) E=mc^2

Given these assumptions, your conclusion is correct. But they are assumptions, albeit based on good solid inductivism. And to date, we have found nothing that falsifies these assumptions (depending on how you view the theories concerning the VSL).

I haven’t read all of the comments in depth (what a time to come into the argument) but I’d like to refer to something Sevitz’z Stalker said way back in Comment 37 about the causality issue.

Here’s your ship sitting in orbit around the earth. Rather than go to the troublesome effort of staying in observable spacetime and accelerating as hard as possible, let’s say we, by hypothetical means, step outside of observable spacetime and step instantly back elsewhere…let’s say a multi-storey car park on Pluto.

The light which bounced off your ship the instant before you stepped outside observable spacetime reaches Pluto five hours and 22 minutes later.

If time is a fundamental, no time travel will have taken place. Everything is relative. When the light arrives, assuming me and my rather zippy little ship are still there (who’d stick around?) and folks on Pluto have great eyesight caused by straining in the gloom the whole time, they’d be able to see my ship in two places at once. But it isn’t in two places at once.

Time travels forward at all, uh, times. Mine, the Plutonians, the ship’s cat’s time. Perception caused by the lag in information relay through reflected light is corrupted. Causality isn’t.

Isn’t saying photons have zero rest mass a bit of a cheat? Zero mass accelerated to infinite speed is still zero mass, so how come they have observable mass at c?

I get the impression from the webcam picture that I’ve introduced an element of despair into Adrian’s life.