Good read so far. I've only started reading it.
i used to work around the clock on call, phone ringin all the time. its no way to live,
Time is only relevant when you're talking about it in context to space. Other than that it has little importance outside the realm of physics. Our species uses time because our lives are short and pointless and we need some mechanism to mark our achievements.
-Funk
Time is an illusion created by man. When man is gone so will be time.
So NPR just did a sweet piece on the very subject, last week I think, can't remember too many specifics. But, time is relative to the force of gravity, i.e. more gravity=slower perception of time...
(SP?)
time is a measurement like miles or litres. next you'll be arguing that distance or volume doesn't exist.
just to take the piss, hes fat wears a red suit, has a white beard, lives in the north pole, and gives out presents at xmas. By your logic santa now exists as I have described him.
There's always a question about "what happened before the big bang," or about the nature of time. Stephen dealt with that in "A Brief History of Time," and you helped with that vision through your work on "A Briefer History of Time." How does this book advance the ball?
A: One of Stephen's big ideas in this book is called "top-down cosmology." It's the idea that we should trace the history of the universe from the present time backwards — and that the universe has many histories because it's a quantum system. In "normal" physics, we work in a laboratory and we do experiments. We set up the experiment in an initial state, then we let it go for a while, then we do measurements on its final state — and we check predictions. The theory tells us how the initial state should develop, and then we make predictions about the final state.
We can't do that with the universe as a whole. We don't set up the initial state. We don't have a laboratory where we can control what's going on. We can't repeat the experiment and take the data. Also, the universe — since we believe in quantum theory now — is a quantum system.
In normal cosmology, people start with the initial state as if it were a laboratory — which it's not — and they use classical ideas, meaning that there's one history of the universe which they trace forward. Stephen believes that we should start from our observations now, because that's all we can do, and trace it backwards, taking into account the fact that the universe has many histories and not just one.
Q: Right, there's a discussion in the book about how the past is as much affected by quantum mechanics as the future is. So there's uncertainty about the past — which is counterintuitive. That must be a hard sell with normal people who say, well, I remember specifically what I had for dinner yesterday. We know for sure what happened in the past because of things ranging from human memory to the fossil record to the process of baryogenesis at the beginnings of the universe. So how can you say that there's a factor of uncertainty about past events?
A: Well, if you happened to have experienced all possible aspects of the universe for all of time, there would not be uncertainty. Quantum theory doesn't say that if you ate an egg, you might not have eaten the egg. Let's get that straight. What quantum theory says is that in between the times when we observe and measure, and interact in that way, these properties that we talk about have no meaning.
For instance, in classical theory, if you push a billiard ball down the table, and if no one is interacting with it or measuring it, it still has one path with a well-defined position at every time. Those properties exist. In quantum theory, if you push it and then no one interacts with it, you cannot in general say that it has a particular position and velocity at any time. In classical theory, we say that it has those properties, and when we measure it, we're just reading off those properties. In quantum theory, it's not correct to say that a measurement is merely reading off those properties. Rather, it doesn't have those properties when we don't measure it.
Now, if you had an egg yesterday, you interacted with the egg, and there's an egg there. When we look at the universe today, with top-down cosmology, we don't allow for the possibility that the moon is made of green cheese – because we already know that the moon isn't made of green cheese. We put in all the data of all our observations, and that prunes down the number of different histories that have to be taken into account. But where observations haven't been made, we don't.
So the vagueness of the past is the vagueness of things unmeasured in the past.
Q: Does that imply then that there will be no way to answer that classic question, "What happened before the big bang"? Because the uncertainty goes to an indeterminately high level?
A: No, it's not that. As you go backward in time, quantum theory, combined with general relativity, tells you that if you go back early enough in the universe, time ceases to have the meaning that we assign to it today. It ceases to act as we know it. So it's not a well-posed question to say, "What happened at the beginning of time?" — because time doesn't go back to the beginning.
According to general relativity, time and space exist under certain conditions. Quantum theory tells you that there are always fluctuations in empty space, and if you make the universe small enough, the fluctuations are great enough that the matter is squashed down enough that this affects the character of space and time itself. Time doesn't exist at that point. So the question doesn't make any sense.
Yea but measurments are exact you can kno exact volume or exact distance therefor u must be able to measure time exactly, but as i tried to explain in my first post there is no exact time.
to everyone who is able to grasp this concept... really requires some abstract thinkin.