We’ve mentioned before that Richard Feynman was way ahead of his time when it came to the need to understand cosmological initial conditions and the low entropy of the early universe. (Among other things, of course.) Feynman actually wrote three different books in the early 1960’s — in his way of “writing books,” which consisted of giving lectures and having others transcribe them — all of which made a point of discussing this problem. The Character of Physical Law was aimed at a popular audience, the Feynman Lectures on Physics were aimed at undergraduate physics majors, and the Feynman Lectures on Gravitation were aimed at advanced graduate students — and in every case he emphasized that we can only account for the Second Law of Thermodynamics by assuming a low-entropy boundary condition in the past, for which we currently have no reliable explanation. (These days we have a larger number of speculations, but still nothing reliable.)
Here’s a video clip from about ten years afterward, in 1973, where Feynman raises a similar point in a conversation with Fred Hoyle, the accomplished astronomer and a pioneer of the Steady State cosmology. (Thanks to Ronan Mehigan.) They don’t go into details, but Feynman introduces the idea as a kind of meta-issue in physics:
“What, today, do we not consider part of physics, which we may ultimately be part of physics?”
His answer (which should be cued up here at the 7:10 mark) is the initial conditions of the universe, as well as the possibility that the physical laws themselves evolve with time. (Conversation continues for a tiny bit in the followup video. Listen on to hear Feynman explain how he doesn’t like to speculate about things.)
What’s interesting is that now, four decades later, it’s commonplace to address the issue of initial conditions in a scientific context, and even to consider the evolution of local physical laws, as we do with the multiverse and the string theory landscape. I’m not sure what is the precise history of this endeavor, but in the very same year this interview was aired, Collins and Hawking wrote an early paper asking why the universe is isotropic. In 1979, Dicke and Peebles published “The Big Bang Cosmology — Enigmas and Nostrums,” which set out many of the puzzles that Alan Guth would attempt to address with the inflationary universe scenario. When we marry inflation with the idea of a landscape of vacua (whether from string theory or elsewhere), we naturally are led to the idea of an evolving set of local physical laws, raising the possibility that we might be able to actually explain (using the anthropic principle or simple probability arguments) why we observe one set of laws rather than some other. Not that we have, or even seem very close, but the scientific agenda is clear.
So how could we answer Feynman’s question today? What do we not consider part of physics, which someday we might?
I could listen to Feynman all day long. He makes ideas and concepts so accessible to mere mortals and does so with such enthusiasm.
Aren’t you writing a paper with Alan Guth exploring initial conditions, the second law and inflation? I hear Guth mention this in a talk at MIT last week and look forward to your article.
“What do we not consider part of physics, which someday we might?” (Feynman):
I say that Man has evolved to have a spiritual side and able to ask six questions: who? what? when? where? how? and why?
Physics struggles well with the first five questions. Philosophers struggle poorly with the sixth. So “why?” might eventually become part of physics.
Erwin Schrödinger made a dent.
“What do we not consider part of physics, which someday we might?”
Conscious/subconscious thought, possibly?
Maybe what some people call the “soul”… the idea of oneself – the undefinable entwining of our perception of reality with our sense of personal essence. dunno. I may be straying into Leary, as opposed to Feynman, territory.
The list has already gotten so far ahead of what can reasonably be tested I’d be happy just to stop at what we’ve got for the time being.
Sorbet– We’re supposed to be, yeah. Neither of us is the fastest paper-writer in physics…
I’ve always considered the low entropy boundary of the universe to be a purely logical consequence of the second-law, not its cause. If Feynman had something else in mind, he sure didn’t make it clear to me in his lecture series.
This topic makes me imagine Sean Carroll acting out the role of Sean Combs in “get him to the greek”. “mind **** baby”.
That’s a great video clip. I always feel sad whenever someone only mentions Hoyle’s connection to Steady State Cosmology. His discovery of nucleosynthesis (the famous B2FH paper) is surely one of the most significant scientific achievements of the 20th century, if not of all time. His prediction of the resonance level of carbon based on anthropic arguments still makes my jaw drop. Yet Hoyle is a good reminder of the fact that famous scientists often tend to be associated more with their misdeeds than their great deeds.
Oh I think I finally see why this is a bit of a conundrum. The universe could be described as undergoing a reversible adiabatic expansion in which case the change in entropy should be zero, but it’s more like an irreversible adiabatic expansion, so there had to be something more ordered to start off.
What always gripes me about this subject is that cosmic variance in vacuum energy is assumed to come with no physical effects that would not be easily observed. This is a ridiculous assumption. A black hole could be defined as an extreme cosmic variant phenomena because it involves an extreme decrease in temperature in the vacuum energy surrounding it. This decreased vacuum energy density results in extreme gravitational forces that has a profound effect on all material objects in it’s vicinity.
The whole idea of bubble universes is completely ridiculous because it ignores all the extreme gravitational effects that would accompany the splitting off off of bubble universes. What has physics today come to when the “gee whiz” factor overrides common sense. It reminds me so much of two physics nerds driving in a car at 70 mph while directly for a brick wall where the road terminates.
One nerd says to the other, “It looks like we may be heading towards an obstacle ahead”. The other nerd replies, “Oh you are such a worrier. Look, the gps says there is clear sailing straight ahead for the next forty miles.” (Crash heard.)
Something I am puzzled about, probably just the semantics of it. What would it mean for a law to evolve in time? do time-dependent Hamiltonians, used in the same old Schrodinger equation, count as “laws evolving in time”?
Note also Feynman’s resolute, absolute refusal to engage in speculation at the end. 😉
Consciousness… That´s it.
Consciousness… That´s it. It will be physics some day, deep physics.
If I answer, you have to trade desks with me. 😀
Peter Woit does not consider string theory to be part of physics, but someday he and Lee Smolin might.
“What always gripes me about this subject is that cosmic variance in vacuum energy is assumed to come with no physical effects that would not be easily observed”.
Make that cosmic variance in vacuum energy is assumed to come with no physical effects AND WOULD NOT be easily observed. You smart ones probably already figured out that I accidentally said the exact opposite of what I meant to say because nothing else I said agree with that original sentence.
OK, most of this column is way above my academic level, but I’ll take a stab anyway.
What effects of quantum mechanics could manifest above ‘normal’ quantum space-time scales? Could we ever directly attribute observed macro results to quantum mechanical causes?
@Low Math, amen to that! There’s even reason to cut some things off the list. I’ve always seen Feynman’s refusal to speculate in this conversation as underscoring the value of not adding things to the scope of physics too soon. However, if I had to guess based on actual empirically verifiable progress, I would name microbiology.
The “evolution of laws” as in the multiverse theories is really just replacing constants in the equations by variables which can change over regions in space. But the basic framework – quantum fields in spacetime, wavefunctions etc is the same.
A more genuine variation of laws would be if the entire mathematical framework and equations changed over space and time, but I have no idea how this could happen or what it would mean.
John Wheeler said something similar in “At Home in the Universe”
“Never has physics come up with a way to tell with what initial conditions the universe was started off. On nothing is physics clearer than what is not physics: equation of motion, yes; initial position and velocity of the object which follows that equation of motion, no.”
I think chemistry will be the first discipline to be replaced by physics.
Feynman is my personal hero.
His bongos are telling me to suspect that the chilly O-ring of ‘living Constitution’ nonsense is being perpetrated on the communal weak of mind.
You know, Che said it: “Silence (as an approach; misdirection) is revolution carried on by alternative means.”
I’m skeptical of Sean’s approach. So should you, even of my own.
Trust neither of us.
“I’ve always considered the low entropy boundary of the universe to be a purely logical consequence of the second-law, not its cause. ”
And you’ve always been wrong.