To think our current science and knowledge of physics is at some pinnacle is very egocentric. Or perhaps more Earth-centric way of thinking. Human beings have a tendency to believe everything we do and achieve is somehow at the very precipice of knowledge. We haven't evolved much beyond "the Earth is the center of the Universe" way of thinking, if at all.
Most of our current "modern" everyday things we take for granted today, were essentially discovered or invented during the 19th century (1800s). Most of our electronics we use in 2008 were not developed until after WW II - and more aggressively after the 1960s.
Taking this very short time period of technological advancement into account. It's a little presumptuous to think that just because we humans can not travel between the stars in a timely manner, doesn't mean that a civilization many orders of magnitude more advanced than we haven't extrapolated the means to do so themselves.
Our current understanding of matter, spacial dimensions and energy are crude at best. Theories such as relativity only explain a certain aspects of a much broader range of things that we have no clue about as of yet.
I personally think that our current theories of what matter is, what the Cosmos is, what and how the various known forces work, among many yet undiscovered aspects of the Cosmos are woefully incomplete. String theory will probably prove to be a dead end as will many of our current theories that only describe very specific spheres of physics.
Here is something I wrote on space.com forums about matter and grappling with a more complete understanding of the Cosmos. By no means am I claiming to be correct, but if we can not think beyond 19th century theories, how do we expect to reach the stars?
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There is much debate on the issue of dark matter. And I've been thinking about this whole problem for quit a long time. Mind you, this is a very compact version of this hypothesis.
According to Cosmic mass measurements, the Cosmos is missing roughly 85-90% of the mass required to keep galaxies intact. Physicists are continually throwing some missing particle to solve the insurrection of the missing mass. And to add to this problem, gravity is the weakest force of the four known forces in the Cosmos. Its as if gravity is leaking from our dimension, or perhaps leaking in from another dimension. The force of a weak magnet is on the order of magnitudes stronger than gravity. Gravity doesn't make sense from a known force standpoint.
It's also stated we live in a three dimensional space with a 4th dimension of time. Ok, but when matter is accelerated to relativistic speeds, time ceases to exist as we understand it and becomes some sort of odd spatial dimension, such as the theories of black holes would suggest. Time is not a constant and this would again suggest it is actually a spatial dimension. This time dilation aspect of the Cosmos is a very well known phenomenon and makes technology such a GPS possible. Time might be more accurately described as a spatial dimension of movement as apposed to our perception of "time".
Now, in order to understand what I'm about to suggest here, one must delve into the realm of a two dimensional reality. Imagine if we existed in a two dimensional reality. How would the 3rd dimension appear to us? Well, if our perception was on the lines of X and Y, there would be virtually no height, so our perception of the 3rd dimension would be that of an infinitely thin slice of a given 3rd dimension object as it passed by our range of perception - some peculiar changing line within our line of vision. Although the 3rd dimension object would be complete and whole, to the two dimensional observer, it would only appear as a very thin slice of it's totality.
Take this concept one step further into our 3rd dimension perception, plus the time* dimension. What if "matter" is our three dimensional perception of what matter actually is as it exists in a higher dimension. And when matter is subject to certain conditions such as a black hole, time then regains its spatial dimension characteristics. But time from our perceptional standpoint is movement.
So if our perception of matter is only a slice of what it actually is in reality, then this could very well explain many things. Take an electron. It is said that an electron when it's not being measured, exists in a state of probability. And once measured, it's then quantified into a physical state of existence that we can detect. But if we attempt to predict what energy state any given electron will be in at a given point in time, we can then only predict a probability of this phenomenon.
Let's take an electron and put its true reality into a higher spatial dimension. In this reality, the electron would appear to us as the 3rd dimensional object would appear to a two dimensional observer - only a slice of what it actually is. The electron would be much more than what we could perceive or measure at any given moment. So from this stand point, an electron would appear to jump from state to state within the confines of probability given the passage of time, when in fact, the electron is moving within higher spatial dimensions that are, for all intent and purpose, impossible for us to interpret from our 3rd dimensional perception.
Now, in an attempt to visualize what is I'm speaking about. Let's simplify this into a line, and the line is matter in its various spatial dimensional existences. Try to imagine the below line as an encapsulation of matter in its totality.
|-- far negative dimensions -- negative dimension spaces -- 1st dimension -- 2nd dimension - us, the 3rd dimension -- 4th dimension -- 5th spatial dimension -- positive dimensions -- far positive dimensions --|
From our standpoint, we experience other dimensions that are at or very near to our 3rd dimension reality, but beyond these limited perceptions, our observational and perceptual abilities greatly diminish. From our standpoint, gravity would then appear to be a weak force as we are capable of measuring the effects of what we can perceive. The other known forces could be just as weak but appear to be very strong when compared to gravity. It all depends on how the various properties of matter interact within the confines of our perceptual reality.
If in fact dark matter is roughly 85-90% of the physical matter of the Cosmos, then this might give us some clue on how much of the missing dimensional space we are not able to perceive. Dark energy could be placed into this equation as well, in the form of negative dimensional space(s) of matter. These negative dimensional spaces would exhibit properties that are counter intuitive of our perception in the positive dimensional realms.
Additionally, this hypothesis could be applied to multi-verse concept, in that multiple parallel Universes could be part of our physical Universe but exist in a different phase of energy from ours. What appears to be empty space* could in fact be our tiny fraction of perception of what actually exist. Parallel Universes would not be separate from ours but rather lie within another range of perception of the very same physical matter we are comprised.
Perhaps string theory is completely off. Instead of continually attempting to reduce particles to their smallest constituent parts, maybe entertain the idea that our current understanding of matter is very poorly understood in that we may only perceive a small fraction of what matter actually is.