Hi. This is a question about Logic. I've read in a book by Michio Kaku, _The Physics of the Impossible_, that it may be possible to receive a signal before it was sent. This to my way of thinking would violate the logic behind causality. And yet on a social level we are effected by what happens in the future. An example would be Christmas shopping. My question is can an effect precede a cause, and if so what does that mean in relation to actuality and reality? Cheers, Pasquale

How does the temperature ever change? If we assume that temperature is a continuous measurement, then we know that it has an infinite number of potential values. In order for temperature to transition between two values, it must then pass over the infinite set of values that lies between whichever two values the temperature is transitioning between. It now seems that temperature should not be able to change at all because before it may change to a given value, it must first reach a value between the desired and the current. Since we can make this claim infinitely, it would seem that temperature becomes "trapped", in a sense, at its current value, unable to change at all. Of course this problem can be applied to other concepts as well, and we might easily draw comparisons to Zeno's ancient thought experiment of Achilles and the tortoise. But the logic here is slightly different; the desired temperature is not continuously fleeing from the present as the tortoise is from Achilles. I simply raise the...

Does a concept, such as the Law of Gravity, exist? If there was no such thing as mass or time, would the Law still exist - just in case?

I seen a question that went, "Can there be an event that is entirely random?" I put a little bit of thought into this and concluded that the "Big Bang" theory, about the fact that the singularity became the universe (which is explained in the opening chapters of Bill Bryson's _A Short History Of Nearly Everything_) must be the only ever event that was random because no one can say why it happened and why it did not simply stay as a singularity forever. I still don't know if that is right because it wouldn't be classed as staying in that state "forever" as time did not exist. But it can be argued that it was not an event as it was the thing (if it can be referred to as a thing) that created time, on which events are obviously based. Also, if this is true wouldn't that be detrimental to the belief of free will? So this may be an answer, I'm not sure but I just wanted to know an expert's opinion on it as I am just a 17 year old student. Also I don't know if it was ok to post the title of a book on this so...

I am a very ordinary art teacher, one who breaks into a rash at the merest glimpse of an equation, and one who is trying to get to grips with the quantum world. Can you answer me this question about the double slit experiment? In the Double Slit experiment, why is it assumed that the particle splits and then reconverges at a point in between the two expected points, rather than a single particle merely bending and curving its trajectory to arrive at the in between point? Yours, Keith

In what sense does the earth rotate around the sun? couldn't the entire universe be thought to rotate around any arbitrary point?

Many of my science professors have remarked that the law of conservation of mass and energy is unprovable (or at least unproven); is this really the case, however? Isn't the problem of the conservation law precisely the problem of induction? (I.e., we observe that the mass and energy of every system we have ever examined has remained constant, but how do we know that this will hold true (1) in the future and (2) of all systems?) But presumably when my professors have said that the conservation law is unproven, they didn't mean that this is so because of the problem of induction (after all, if they took this route then all of science would be "unproven"!). I feel as though they are treating the conservation law as exceptional when in fact it is not. -ace

It seems that most astronomers and theoretical physicists believe that time only began at the formation of the universe with the "big bang". Assuming that this is correct, is it possible for time to end (to no longer exist)? If so, what conditions would be necessary for this to occur? JW (Australia)

If the universe has existed forever, i.e. if the universe did not have a beginning, would the present time be possible? That is, if an infinite amount of time was necessary to get to the present time? And if this is so, does this mean the universe necessarily had a beginning?

If science is based on observable, measurable data, what is the basis of science's belief of the origins of the 'Big Bang'? Even religions talk of the cataclysmic beginnings of the Universe, but they don't claim the Bang was of Nothing. Observable, mathematical data suggests nothing begets nothing.