Answer to Question: Why does time seem to exist only in a forward direction?

Time seems to only exist in a forward direction because the universe is expanding. If the Universe reaches Critical Velocity and starts to contract ….then time, as we measure time will reverse according to the Big Bang / Big Crunch Theory. The reason for this is that time does not exist without change or movement….. (change or movement of particle matter or energy as we know it). If matter has no movement either expanding or contracting then time does not exit for that matter. However Time can exist around non moving particle matter if something is either expanding or contracting around it.

If the expansion of matter increases as in the case of our universe, or an expanding object, or even light…then time increases relative to the rate of expansion. Example: if carbon A is heated and expands faster than carbon B (which is not heated) then time increases in carbon A relative to carbon B…However as Einstein pointed out…time is relative to the observer…and you need something of contrast to make that comparison….fortunately our universe offers lots of contrast …otherwise we would have a very difficult time figuring this out. Time being relative to the observer can exist at different speeds based on the rate of expanding matter. If you are on riding on a beam of light than time is much different than your friend riding on a sound wave. Of course time is relative to the observer, therefore your time is much faster only to him, or any body else who is not on a beam of light.

If matter contracts or condenses then time actually reverses…as in the case of a contracting universe…so Planks Quantum would be measured as zero time for the entire Universe…and time starts at the point of the Big Bang (once matter is on the move again)… In the case of a Black Hole, relative to our expanding universe)… there is also no time. (except for matter being sucked into a Black Hole….this matter would be reversing in time, until at which point it becomes part of the Black Hole mass, then time (in a Black Hole) as in Planks Quantum is zero….which is odd because the Universe is still expanding around the Black Hole…but it is consistent with the theory that. Time can exist around “non moving matter” if something is either expanding or contracting

Time as we know it is measured in a forward direction and will continue until the point of critical velocity…at which point time starts to reverse…and for a brief moment…the point where the Universe changes from expanding to contracting…time will again be zero…as in Planks Quantum. However…during the forward direction of time…(while the Universe is expanding)…Black Holes are continuing to suck up matter…and should in theory at some point converge with other Black Holes….Therefore…as the universe is expanding from the Big Bang…there is multitude of matter which is not expanding (Black Holes)…which might well be unexploded Planks Quantum matter from the Big Bang…and the Black Holes with their massive gravitational force are sucking up matter which was attempting to expand but was not able to overcome the stronger force of the Black Hole…like mini-Plank Quantum’s converging within the universe …When the Universe reaches Critical Velocity and then all matter in our Universe starts to contract…heading towards the Big Crunch….the multitude of Black Holes converging (up to that point) should in theory rapidly increase the speed of reverse time …acting as an accelerant force of a contracting Universe with their collective gravitational force …So the reverse of time.(the journey the contracting Universe is taking towards the Big Crunch)…should happen much quicker than the time it took for the Universe to go from the Big Bang to Critical Velocity…That is of course Time relative from the Big Bang to Critical Velocity ……in contrast to …….Time Relative from Critical Velocity to the Big Crunch. Mathematically it might be possible to estimate this time.… Rob MacRiner rmacriner@sympatico.ca Nov 2007

But there is another limitation I can think of: BUS speed. This is a huge bottleneck in games, and I’d imagine sharing info between the CPU and the GPU would be even worse for scientific apps when considering the huge amount of data that has to scheduled and transfered.

Well, that’s just a function of how much processing you need to do on the data between bus transfers, such that any time your operation scaling with data size is greater than linear it’s likely to be a benefit over CPU processing.

Exactly. The reason why GPU’s became a massively SIMD arch in the first place was because graphics has so many inherently parallel processes (e.g., ray tracing, scan conversion, voxel based computations, etc.). Similar processes in scientific computing would make GPU’s very useful (as soon as they natively support double precision flops).

But there is another limitation I can think of: BUS speed. This is a huge bottleneck in games, and I’d imagine sharing info between the CPU and the GPU would be even worse for scientific apps when considering the huge amount of data that has to scheduled and transfered.

So, for scientific apps, the ideal situation would be to have a CELL or GPU-optimized library where you just call a few commands to make use of the CELL or GPU as an external processing device. As a result, I think that GPU’s are a bit more usable in this regard, as the PPE is a bit underpowered compared to desktop processors. The difficulty, though, is that modern GPU’s don’t even support double-precision floating point, though nVidia has promised support with hardware released late this year (this was as of last year).

Using PS3’s is pretty makeshift though. The CELL may have a high theoretical peak performance (especially with flops), but you have 7 asymmetric coprocessors with all kinds of different address space. Optimizing the code is a bitch, refactoring code from other platforms is a nightmare. Can’t imagine it would be ideal as a scientific computing solution.

LOL. Men, If just I had had this wonderful idea before I started my stupid PhD thesis about such an useless thing as autonomic computing . . .

There could be a nice thesis project on what happens when you include time-dilation in Mario Cart.

So seems quite a cool deal, you get your cluster and a bunch of gaming machines for playing Resistance: Fall of men while you are supposed to work. The next level on procastination, I suppose.

So What’s the name of the game they are trying to ban or have banned in the uk?

Actually, anything to overcome a “Cover 2″ defense would be pretty high in my list … or anything Appalachian State used in their defeat of Michigan, for that matter …

Too bad I didn’t think about the corporate sponsorship angle!

So either Gaurav is optimizing his code by making do with single precision, or it’s not running as fast as it could, had the creators of the Cell processor been more sympathetic to scientific applications. It is hoped future versions of the processor will remedy this.