To be a firm believer in the arrow of time insists that you don't fully understand the special or general theories of relativity. We have PROVEN, beyond the shadow of a doubt, that time is relative to the observer. An atomic clock on the ground will most definately measure a "longer" time than one on a supersonic jet. We;ve tested this and know it as scientific fact. As YOU approch c, 3.0x10^8 m/s, observation of YOUR time relative to a 3rd party at a fixed point approaches zero, while your perception of time stays exactly the same. Likewise, if you were to somehow reach the speed of light (impossible, since your mass reaches infinity as you accelerate towards c, also a proven fact), time to you would still tick on, however your time relative to a fixed point outside of your system would not measure a time for you. Time for you has effectively stood still, however you still feel as though time is passing. If the time of the universe were to be an "arrow," as you say, then it would be impossible for time to stop. We've tested the theories of special and general relativity so many times that we can take the new laws they present as fact, and it states that time and space form a 4-dimentional spacetime, as well as raising the possibility of imaginary time where any and all histories possible are infact definate. That was Feynman's fault :)...The basic idea that Feynman presents is that since Heisenberg's uncertainty principle states that you cannot know both the position and the momentum of a particle, you must therefore have to assume that any and all paths between point A and B are indeed travelled. As it turns out, the false paths cancel eachother out and only the true path remains, but we can never measure it. Instead, we measure it in probability terms using a wave formula to decide where a particle MAY be...This idea has been extrapolated to imaginary time, where you deviate to a timeline perpendicular to that of "real time," Where all histories between points A and B are both possible and definate. A history where you batted 1.000 for the 1947 New York Yankees exists in imaginary time, but Feynman's statement shows that if this is not true, it will cancel out a completely reverse history in the same dimension of time. The universe cannot possibly have a single measurement of time, because A) we don't have a way to measure it, B) is negates a tested theory of modern physics, and C) it negates a perfectly plausible theory of imaginary time, combining the proven Uncertainty Principle, Probability Formulas developed by Shroedinger, The time-tested (no pun intended, really) theories of special and general reletivity, and Steven Hawkings huge friggin brain (p-brane? ;)). As Einstein stated: "There are no absolutes in the universe." Time is no exception.

Consider this thought experiment. I'm sure you've heard of the twin paradox: One twin leaves in a spaceship at close to the speed of light, while his bother stays on earth. They both measure time the exact same way. One second at a time. Each second has the same duration RELATIVE to each person, however, if they were to somehow measure EACHOTHER's time, the twin in the space ship would see the seconds flying by, thousands of them per his own measure of a second, while the twin on the earth would see his brother's time passing extremely slowly. This thought experiment alone shows that there's no way that time is constant, because it's measured differently by different observers.

In response to the cosmic background radition: as we look back in space, we see further back in time. This is obviously true just because it is light that left its source Billions of years ago and is just reaching us now. We will not see its "current" state (another time issue there...I'll spare the discussion...'current', relative to this second on this planet) for the same duration of time...a few billion years (and our sun will be long-gone by then...). As you look deeper and deeper, you see smaller, newer, less-formed galaxies and other celestial bodies. The cosmic background radition is simply what you see as the Language Removed that was there BEFORE and WHILE the celestial bodies formed. Rather, more precicely, the soup that matter was constructed of. Neutrons, Protons, electrons, etc, forming light elements such as Hydrogen and Helium, which compact, form dust clouds, then stars, which produce heavier elements like Carbon, which then form other bodies, blah blah blah... As Stephen Hawking explains ever so wonderfully, if you were to look back past the newest galaxies, 15 Billion light-years, you would find the sub-sub-sub-atomic particles that the universe is built on, back when the universe was still 100 Billion degrees and "rapidly" (need I say this is relative? I guess not...I just did...) cooling to 1 Billion degrees. Thanks to Edwin Hubble, we also know that the universe is expanding, leading to the conclusion that since we are moving farther apart, than we MUST, NO DOUBT ABOUT IT, have been closer to other objects in the past. Hawking theorizes, and I believe correctly so, that if you were to look past the background radiation to a point where the universe was extremely dense, the very light reaching your eyes would have been skewed by the immense gravitational pull of the compressed mass of the early universe, eventually bending to the singularity that we call the big bang. With the EXTREMELY IMPORTANT SUPER-DUPER recent discovery of the polarization of the background radiation, we are within mere fractions of 100% certainty that this 'noise' is definately the early remnants of the big bang.

So, after all that is said, no, the background radition is not the "sucking-sound" of a big-bang fabricated vacuum, but it is a huge cloud of the building blocks of the universe, filled with particles, anti-particles, and imaginary particles which we can't detect.

As far as travelling into the past, Einstein said it already happened, so you can't back up - I suppose this is something like the arrow of time, but it is possible based on wormhole theory that since time and space are part of the same thing, a 4-dimensional universe, you can connect two point in the fabric of spacetime with a tunnel called a wormhole (which can be shown on 3d graphs to represent a position in spacetime where time ends and stand still), and wind up in a position in a different place at a time before you left. It's heavy...VERY heavy. It takes a lot of math to figure out, a lot of math to understand fully, or a really big head to wrap around one of Mr. Hawking's books - or Mr. Feynman. Two of the best physics teachers to ever grace this earth.

Lemme know if this helped or only stood to confuse you more...

You know, actually, how about we start off with you telling me if you ever READ this ;) It took me forever to type up.

~Chris

• Tachyons: faster than light? - omicron - November 20, 2002 - 04:33 UTC