Ah, the monthly Physics thread.
I have a couple of comments about this, so bear the horrible quote list.
NO.
Physical Laws are un-break-able and un-bend-able. They CAN NOT be modified.
As others pointed out, Physical Laws are only human invention, and model the nature to a certain degree. Other than that, I would advise caution when using words like "never", "cannot", etc. in the Physics context.
Usually proposed options include making the way between A and B shorter (warp drive, which actually has somewhat of a sound theoretical basis already, the problem is manipulating space-time continuum...), or creating a shorter alternative route between A and B (wormhole, or Einstein-Rosen bridge).
For some reason I always get the feeling that the scientists researching these topics are hardcore sci-fi show fans. I have said it before here, but there are problems to model certain everyday things, like the interaction between light and in some cases, even thermal distributions. With background like this, expanding up to the Universum-scale at this point should cause shuddering in the scientific community. Yeah, I don't have anything to back this up but the common sense. If liquid form water in -4 degrees of Celsius turning to ice in a split-second cannot be modelled, what is the probability of getting things right in the Universum-scale? Anyways, back to business.
Not impossible...just extremely difficult to the extreme. Some mathematicians and physicists calculated out what it would take to warp space time and jump from one location to another. Its doable...just needs allot of power.
Add engineers to that equation and then you'll see we are even further away. I have had some funny discussions with colleagues specialized in engineering about the requirements of the theoretical physicists; for example extremely dense matter with no mass (yes, this was once required).
Trying to flyl at the speed of light, you're own mass would kill you LONG before you reached it...now, if you somehow managed to nullify your mass (handwavium) then flying at the speed of light might actually be possible.
As Herra already said, this is a misconception. If you measure your mass inside the rocket that goes ~c (with no acceleration), it will be the same that you measured on Earth. But since I time by time tend to understand what people not-so-involved with Physics, I think you are meaning the effects of that rocket smashing to a extremely thick wall of lead. There you would see that the momentum that deformed the wall could be calculated from the old p=mv (this is a simplification of matters, I know), except this time mass should be modified with the formula Herra put up. For a person struck by a relativistic bullet, he would report getting hit by massive amounts of energy in any case, even though the mass of the bullet would be small.
For example, it's still not quite clear to me if Lorentz-contraction of relative co-ordinates is an observation or a real phenomenon... and, indeed, what is the difference between observation and reality. After all, don't we define reality by observations? Even the concept of simultaneity in relativity is heavily connected to observations due to signal speed limit of c - which can be interpreted, in a way, so that what you see on the night sky is simultaneous to this co-ordinate system. Or you could interpret our time as global time and make the distance-time corrections to each star's relative time to us.
For me, the only way to get out of that mess was to think that for humans there is no such thing as reality. Only observations in certain reference frames. The length of the metre in a rocket doing 0.99c is the simply the length of the metre. Some idiot is of course measuring that stick outside of the rocket in his own reference frame and measures that the length of that stick is less than one meter. Both are equally valid results. But here we assumed before hand that we that the length of the stick was one meter in some universal, absolutely true coordinate system, which doesn't exist, one of the prequisites of Special Relativity! This is probably one of the reasons Church objected to the relativity first since it seems to destroy the concept of God. The Lorentz transformations are simply coordinate system changes between frames, nothing more on that. Everything is relative! Or at least this is how I understand it.
One can see clearly in it why one can't go faster than light - the root can't be a negative number! Which means the (v/c)^2 can't be bigger than 1, which čeads to the conclusion that v < c
And at this point it doesn't take long for some Mathematician to point out the flaws in here. The sqrt-function can be defined for the complex numbers and thus v can be greater than c. The mathematics don't prevent it. Only observed world has a lack of FTL-objects. Unfortunately FTL travelling in our current world would also cause some difficulties with causality. Because causality is so much incorporated in humans, most of the Physicists would like to accept the spacetime wrapping as a way to go faster, rather than break the causality. Some times I wonder what funny surprises are there with the tachyons, if you cannot connect them to incidents, how can you measure them at the first place?
And please don't ask me to write the energy tensor metrics here, I can't. I basically know what happens but I can't use the maths... yet.
Quitter.
Here we have another interesting question: what exactly is space-time? It is a four-dimensional quantity with three space-like components (the world we observe) and time for the temporal-like component. But what is it, when you get to the bottom of the things?
However, if you consider the statement "each old theory must be part of the new on" it simply doesn't hold water. There are numerous old theories that have been abandoned because they were not replaced by more accurate theory, but because they were proven untrue. Heavier objects falling faster than lighter comes to mind, as well as geocentric models of universe. Or elements being fire, water, earth and air.
Careful with the interpretations of the old world. In most cases, the heavier object indeed falls faster than the lighter one, since the friction caused by air has to be taken account. That is an observation that unfortunately is true to certain amount. Some poindexter Galilei went out and dropped different iron balls(?) on the ground, demonstrating that the falling time is the same for both of them. Unfortunately, he didn't report results with a feather. If there is air involved, the feather would indeed take lots more time to hit the deck so to say. Of course, most people will now understand that air friction and gravity are separate effects, but during those times it might not have been so, and in practical life it was not necessary to separate them.
Geocentric model, well, that is pretty much what church said and if you didn't like it you lost your head. Then the elements fire, water, earth and air, well, there are some interesting medical things coming from the old element theories that govern the functions of organs inside human body. Most of that stuff is quite interesting actually, since as far as I know it is based on experiments done on humans...
That's similar logic as "5 billion flies can't be wrong - manure tastes and smells good!"
Well if 5 billion flies do that, then it is probably so for the flies. For humans, maybe not.
Also, in the scale of galaxy-wide travels, the end of the universe will be upon the travelers much faster than for those left behind.
And then there is a possibility that the expansion speed of the universe approaches c. Which would cause some trouble in returning back to home.
If you don't believe me, go ask a physicist about singularities, or why we can describe things up to just short of the actual Big Bang (we're still off it by some small but very crucial fraction of a second).
Personally I have some difficulties in believing this stuff. It is too far-fetched for my tastes and due to the difficulties in reversing the flow of time, it will be quite difficult to know how far back does that stuff exactly hold. It is an interesting research topic since this is quite difficult to verify experimentally, but still lots of money can be spent there.
For something easier task first, how did Sun (as we know it) form? I recall it was stated that it is probably a remnant of some supernova or a nova, but where are those blown-up stars now? And, what causes the sun-spots? Then there is a thing about the emitted energy of the sun, it increases within time to till certain event in the far future. Before there was less irradiance on the surface of the Earth, but the temperature levels were higher. I would be a little more optimistic about the Big Bang stuff if they replied a little bit more about the sun first.
Mika
