Quotes from Sean Carroll

In quantum mechanics, no matter how many individual pieces make up the system you are thinking about, there is only one wave function . Even if we consider the entire universe and everything inside it, there is still only one wave function, sometimes redundantly known as the "wave function of the universe.

Life is a process, not a substance, and it is necessarily temporary. We are not the reason for the existence of the universe, but our ability for self-awareness and reflection makes us special within it. This

If a symmetry between electrons and electron neutrinos is like comparing apples to oranges, trying to connect fermions with bosons is like comparing bananas to orangutans.

Now comes the real magic. In pre-relativistic Newtonian mechanics, momentum is represented by a three-vector given by mass times velocity, . In the world of relativity, we define the four-momentum in an analogous way, as mass times four-velocity:

The universe is incredibly more orderly than it has any right to be.

This book is about the nature of time, the beginning of the universe, and the underlying structure of physical reality.

But honest physicists admit that we don't truly understand quantum mechanics.

The minus sign in the proper-time formula (6.2) opens up an interesting possibility. If we consider a straight path that traverses equal amounts of space and time, (?x)2 = (?t)2, we will have ? = 0. So the object moves, but no proper time elapses along its journey.

Newton blew away any dusty talk of natures and purposes, revealing what lay underneath: a crisp, rigorous mathematical formalism with which teachers continue to torment students to this very day.

What in the world is going on with that?

wormholes don't grow on trees.

They were materialists, who hoped to explain the world in terms of objects obeying rules, rather than being driven by an underlying "purpose.

finding evidence for the divine in the gaps in our physical understanding. Likewise,

Intellectual fascination crosses many boundaries.

Then we compare the predicted abundance of such a WIMP with the actual abundance of dark matter.

According to quantum mechanics, what we can observe about the world is only a tiny subset of what actually exists.

To a physicist, a "vacuum" is not a machine that cleans your floors, nor does it even necessarily mean "empty space." It's simply "the lowest-energy state of a theory.

There may be no ultimate answer to the "Why?" question. The universe simply is, in this particular way, and that's a brute fact.

We can think of the difference between math and science in terms of possible worlds. Math is concerned with truths that would hold in any possible world: given these axioms, these theorems will follow. Science is all about discovering the actual world in which we live.

Neutrino masses aren't completely understood as yet, so let's pretend that they don't interact with the Higgs, although the jury is still out.)

of this changed thanks to a clever chap named Isaac Newton.

There's nothing wrong with doing elaborate double-blind studies to look for parapsychological or astrological effects, but the fact that such effects are incompatible with the known laws of physics means that you would be testing hypotheses that are so extremely unlikely as to render it hardly worth the effort.

But what makes a good clock? The primary criterion is that it should be consistent—it wouldn't do any good to have a clock that ticked really fast sometimes and really slowly at others.

As impressive as matrix mechanics was, it suffered from a severe marketing flaw. The mathematical formalism was highly abstract and difficult to understand. Einstein's reaction to the theory was typical: A veritable sorcerer's calculation. This is sufficiently ingenious and protected by its great complexity to be immune to any proof of its falsity. This from the guy who had proposed describing space-time in terms of non-Euclidian geometry.