This view corresponds better to the physical world and has more explanatory power in describing immediate physical phenomena: gravity, electrostatic interaction, information transfer by EPR experiment are physical phenomena carried directly by the space in which physical phenomena occur.
It seems that the Universe is 3D from the macro to the micro level to the Planck volume, which per formalism is 3D. The researchers give an example of this concept of time by imagining a photon that is moving between two points in space. The distance between these two points is composed of Planck distances, each of which is the smallest distance that the photon can move. The fundamental unit of this motion is Planck time. When the photon moves a Planck distance , it is moving exclusively in space and not in absolute time, the researchers explain.
Numerical order is not equivalent to temporal order, i. Without using time as the fourth dimension of spacetime, the physical world can be described more accurately. As physicist Enrico Prati noted in a recent study, Hamiltonian dynamics equations in classical mechanics is robustly well-defined without the concept of absolute time. I think often it is misunderstood. The question is, why can't we live happily together, and why can't people pray to their gods and study the universe without this continuous clash?
I think that this continuous clash is a little bit unavoidable, for the opposite reason from the one often presented. It's unavoidable not because science pretends to know the answers. But it's the other way around, because if scientific thinking is this, then it is a constant reminder to ourselves that we don't know the answers.
In religious thinking, often this is unacceptable. What is unacceptable is not a scientist that says I know, but it's a scientist that says I don't know, and how could you know? Based, at least in many religions, in some religions, or in some ways of being religious, an idea that there should be truth that one can hold and not be questioned.
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This way of thinking is naturally disturbed by a way of thinking which is based on continuous revision, not of the theories, of even the core ground of the way in which we think. So summarizing, I think science is not about data; it's not about the empirical content, about our vision of the world. It's about overcoming our own ideas, and about going beyond common sense continuously. Science is a continuous challenge of common sense, and the core of science is not certainty, it's continuous uncertainty.
I would even say the joy of taking what we think, being aware that in everything we think, there are probably still an enormous amount of prejudices and mistakes, and try to learn to look a little bit larger, knowing that there is always a larger point of view that we'll expect in the future. We are very far from the final theory of the world, in my field, in physics, I think extremely far.
Every hope of saying, well we are almost there, we've solved all the problems, is nonsense. And we are very wrong when we discard the value of theories like quantum mechanics, general relativity or special relativity, for that matter. And throw them away, trying something else randomly. On the basis of what we know, we should learn something more, and at the same time we should somehow take our vision for what it is, a vision that is the best vision that we have, but then continuous evolving the vision. If this is science, if science works or in part works in the way I've described, if this which I've described, it's some relevant aspect of the way science works, this is strongly tied to the kind of physics I do.
The way I view the present situation in fundamental physics is there are different problems in fundamental physics. One is the problem of unification; it's providing a big theory of everything. The more specific problem, which is a problem in which I work, is quantum gravity. Quantum gravity means simply doing the quantum theory of gravity, how things fall, i. It's a remarkable problem because of general relativity; gravity is space-time; that's what we have learned with Einstein.
Doing quantum gravity means understanding what is quantum space-time. And quantum space-time precisely requires some key change in the way we think about space and time. Now, with respect to quantum gravity, in my opinion there are two major research directions today. Which is the one in which I work, loops, and strings. There are not just two different set of equations, but they are based on different philosophies of science, in a sense. The ones in which I work is very much based on the philosophy I just described, and that's somehow what forced me to think about the philosophy of science.
Because the idea is the following: the best we know about space-time is what we know from general relativity. The best we know about mechanics is what we know from quantum mechanics. There seems to be a difficulty in attaching the two pieces of the puzzle together: turn them around, and they don't fit well.
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But the difficulty might be in the way we face the problem. The best information we have about the world is still contained in these two theories, so let's take quantum mechanics as seriously as possible, so believe it as much as possible.
Maybe enlarging a little bit to make it general relativistic, or whatever. Let's take general relativity as serious as possible. General relativity has peculiar features, specific symmetries, specific characteristics. Let's try to understand them deeply and see wether as they are, or maybe just a little bit enlarged, a little bit adapted, can fit with quantum mechanics to give a theory. Even if the theory that comes out then contradicts something that is the way we think. That's the way quantum gravity, in the way of the loops, the way I work in, and the way other people work in, is being developed.
This takes us in one specific direction of research, a set of equations, a way of putting up the theory. String theory has gone in the opposite direction. In a sense it says, well, let's not take too seriously general relativity as an indication of how the universe works.
Even quantum mechanics has been questioned to some extent. Let's maybe imagine that quantum mechanics has to be replaced by something very different. Let's try to guess something completely new, which is some big theory out of which somehow the same empirical content of general relativity and quantum mechanics comes out in some limit. I am distrustful of this huge ambition because we don't have the tools to guess this immensite theory.
String theory's a beautiful theory. It might work, but I suspect it's not going to work. I suspect it's not going to work because it's not sufficiently grounded in everything we know so far about the world, and especially in what I think or perceive as the main physical content of general relativity. String theory's a big guesswork.
I think physics has never been a guesswork; it has been a way of unlearning how to think about something, and learning about how to think a little bit different by reading the novelty into the details of what we already know. Copernicus didn't have any new data, any major new idea, he just took Ptolemy, in the details of Ptolemy, and he read in the details of Ptolemy the fact that the equants, the epicycles, the deferents were in certain proportions between them, the way to look at the same construction from a slightly different perspective and discover the earth is not the center of the universe.
Einstein, as I said, took seriously Maxwell's theory and classical mechanics to get special relativity. So loop quantum gravity is an attempt to do the same thing: take seriously general relativity, take seriously quantum mechanics, and out of that, bring them together, even if this means a theory where there's no time, no fundamental time, so we have rethink the world without basic time.
The theory, on the one hand, is very conservative, because it's based on what we know. But it's totally radical because it forces us to change something big in our way of thinking. String theorists think differently. There we know what is time, we know what is space, because we're at asymptotic distances, at large distances.
The theory's wilder, more different, more new, but in my opinion, it's more based on the old conceptual structure. It's attached to the old conceptual structure, and not attached to the novel content of the theories that have proven empirically successful. That's how my way of reading science matches with the specifics of the research work that I do, and specifically of loop quantum gravity.
Of course we don't know. I want to be very clear. I think that string theory's a great attempt to go ahead, done by great people. My only polemical attitude with string theory is when I hear, but I hear less and less now, when I hear 'oh, we know the solution already, certain it's string theory. What is true is that that's a good set of ideas; loop quantum gravity is another good set of ideas. We have to wait and see which one of the theories turns out to work, and ultimately to be empirically confirmed.
This may take me to another point, which is should a scientist think about philosophy, or not? It's sort of the fashion today to discard philosophy, to say now we have science, we don't need philosophy. One is historical. Just look back. Heisenberg would have never done quantum mechanics without being full of philosophy. Einstein would have never done relativity without having read all the philosophers and have a head full of philosophy. Galileo would never have done what he had done without having a head full of Plato. Newton thought of himself as a philosopher, and started by discussing this with Descartes, and had strong philosophical ideas.
But even Maxwell, Boltzmann, I mean, all the major steps of science in the past were done by people who were very aware of methodological, fundamental, even metaphysical questions being posed. When Heisenberg does quantum mechanics, he is in a completely philosophical mind. He says in classical mechanics there's something philosophically wrong, there's not enough emphasis on empiricism. It is exactly this philosophical reading of him that allows him to construct this fantastically new physical theory, scientific theory, which is quantum mechanics.
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It has worked because in the first half of the 20 th century, people were so smart. Einstein and Heisenberg and Dirac and company put together relativity and quantum theory and did all the conceptual work. The physics of the second half of the century has been, in a sense, a physics of application of the great ideas of the people of the '30s, of the Einsteins and the Heisenbergs.
When you want to apply thes ideas, when you do atomic physics, you need less conceptual thinking. But now we are back to the basics, in a sense. When we do quantum gravity it's not just application. I think that the scientists who say I don't care about philosophy, it's not true they don't care about philosophy, because they have a philosophy.
How can that be? By counting the number of atoms in the universe and comparing that with the amount of energy we see, scientists determined that "exactly equal" isn't quite right.
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Somehow, when the universe was about a tenth of a trillionth of a second old, the laws of nature skewed ever-so-slightly in the direction of matter. For every 3,,, antimatter particles, there were 3,,, matter particles. Since this puzzle was understood nearly a century ago, researchers have been studying matter and antimatter to see if they could find behavior in subatomic particles that would explain the excess of matter.
They are confident that matter and antimatter are made in equal quantities, but they have also observed that a class of subatomic particles called quarks exhibit behaviors that slightly favor matter over antimatter.
Internal clocks in timeless universe
That particular measurement was subtle, involving a class of particles called K mesons which can convert from matter to antimatter and back again. But there is a slight difference in matter converting to antimatter as compared to the reverse. This phenomenon was unexpected and its discovery led to the Nobel prize, but the magnitude of the effect was not enough to explain why matter dominates in our universe. Thus, scientists have turned their attention to neutrinos, to see if their behavior can explain the excess matter. Neutrinos are the ghosts of the subatomic world.
Interacting via only the weak nuclear force, they can pass through matter without interacting nearly at all. To give a sense of scale, neutrinos are most commonly created in nuclear reactions and the biggest nuclear reactor around is the Sun. To shield one's self from half of the solar neutrinos would take a mass of solid lead about 5 light-years in depth.
Neutrinos really don't interact very much. They change their identity. Physicists know of three distinct kinds of neutrinos, each associated with a unique subatomic sibling, called electrons, muons and taus. Electrons are what causes electricity and the muon and tau particle are very much like electrons, but heavier and unstable. The three kinds of neutrinos, called the electron neutrino, muon neutrino and tau neutrino , can "morph" into other types of neutrinos and back again.
This behavior is called neutrino oscillation.
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Neutrino oscillation is a uniquely quantum phenomenon, but it is roughly analogous to starting out with a bowl of vanilla ice cream and, after you go and find a spoon, you come back to find that the bowl is half vanilla and half chocolate. Neutrinos change their identity from being entirely one type, to a mix of types, to an entirely different type, and then back to the original type. Neutrinos are matter particles, but antimatter neutrinos, called antineutrinos , also exist.