We know a lot of things, but what we don’t know is a lot more.
I have a much easier time imagining how we would understand the big bang, even though we can’t do it yet, than I can imagine understanding consciousness.
String theory is an attempt at a deeper description of nature by thinking of an elementary particle not as a little point but as a little loop of vibrating string.
If I take the theory as we have it now, literally, I would conclude that extra dimensions really exist. They’re part of nature. We don’t really know how big they are yet, but we hope to explore that in various ways.
In Einstein’s general relativity the structure of space can change but not its topology. Topology is the property of something that doesn’t change when you bend it or stretch it as long as you don’t break anything.
I have a tendency, more than most other physicists, to try to figure out everything all at once, before I publish. And even to try to figure out everything in my head, without pencil and paper.
It’s indeed surprising that replacing the elementary particle with a string leads to such a big change in things. I’m tempted to say that it has to do with the fuzziness it introduces.
As of now, string theorists have no explanation of why there are three large dimensions as well as time, and the other dimensions are microscopic. Proposals about that have been all over the map.
But the beauty of Einstein’s equations, for example, is just as real to anyone who’s experienced it as the beauty of music. We’ve learned in the 20th century that the equations that work have inner harmony.
The theory has to be interpreted that extra dimensions beyond the ordinary four dimensions the three spatial dimensions plus time are sufficiently small that they haven’t been observed yet.
You enter a completely new world where things aren’t at all what you’re used to.
I wouldn’t have thought that a wrong theory should lead us to understand better the ordinary quantum field theories or to have new insights about the quantum states of black holes.
String theory is 21 st century physics that fell accidentally into the 20th century.
M stands for Magic, Mystery, or Matrixaccording to taste.
One of the basic things about a string is that it can vibrate in many different shapes or forms, which gives music its beauty.
There was a long history of speculation that in quantum gravity, unlike Einstein’s classical theory, it might be possible for the topology of spacetime to change.
Away from the safety of your home, the universe was not made for your convenience.
Most people who haven’t been trained in physics probably think of what physicists do as a question of incredibly complicated calculations, but that’s not really the essence of it. The essence of it is that physics is about concepts, wanting to understand the concepts, the principles by which the world works.
We have one real candidate for changing the rules; this is string theory. In string theory the one-dimensional trajectory of a particle in spacetime is replaced by a two-dimensional orbit of a string. Such strings can be of any size, but under ordinary circumstances they are quite tiny,... a value determined by comparing the predictions of the theory for Newton’s constant and the fine structure constant to experimental values.
The hardest part of research is always to find a question that’s big enough that it’s worth answering, but little enough that you actually can answer it.