Physics: What We Do and Don’t Know

Weinberg has been writing for NYRB for a long time now. Several of his other articles are not behind the paywall:

http://www.nybooks.com/contributors/steven-weinberg-2/

I have completely different feelings about this image, but I think you are correct in attaching a lot of meaning to it. We're very lucky to have been born at a time were we get to see it.

If it's uniqueness you're concerned about, there are a lot of different parameters that describe habitable worlds and even more to describe the history of a civilization. Odds are, what most civilizations experience is unique to them; but I too believe there are likely to be many similarities, too.

Our inability to see and interact with other civilizations - even within the relatively small neighborhood of our own galaxy - is frustrating, and somewhat of a logical conundrum as described by the Fermi Paradox. Whatever the factors preventing us and others from making contact are, and I think it's likely a combination of several instead of one big filter, I hope we can leave them behind at some point and join up with the other people out there.

When I look at bigger parts of the universe, I feel inspired. The universe is not small and limited, it's vast and full of possibilities. Odds are we're not singular but in good company, and we have a lot still to discover and explore. What we do and know is unique and meaningful, yet at the same time it's not all there is.

You're experiencing the effects of Douglas Adams' Total Perspective Vortex (from Hitchhiker's Guide to the Galaxy).

It was basically a torture chamber which inflicted the most horrific sort of torture imaginable upon its victims. How?

"For when you are put in the Vortex, you are given just one, momentary glimpse of the size of the entire unimaginable infinity of creation along with a tiny little marker saying, 'You are here'."

When the victim sees his complete and utter insignificance, his psyche is utterly destroyed beyond recovery.

Presumably it's dated by when the print version is released.

It's funny, for each thousand miles of space explored, we explored a mm or less of what is beneath us. We know what primal forces govern building blocks of space and time but we don't know how bicycle works.

For every profound truth we discover, there is an inane mystery we are yet to discover.

Yeah physics departments should share this article with incoming students, to help them see where the field is going. Although one thing missing is that I would want to find another article that illustrates the ways that physics research is improving and helping our lives today.

I started out in physics, was interested in relativity and the like, but thought ahead to a career in physics and saw that folks were into string theory, which didn't really appeal to me, and I wasn't seeing how physics research was helping people today. I should have done more research into the field before leaving it, but, I went into physics and science education research and cognitive science. Ironically, a similar article like this one got me into cognitive science (before I even started college), an interview with Patricia Churchland by Bill Moyers.

First, we would expect to see such matter production occuring today, not just in the past.

Second, and much more conclusively, we have specific predictions from Big Bang Nucleosynthesis (which was just 20 minutes after the big bang, when the entire universe was as hot and dense as the interior of a star) that match up to observations today with exquisite detail. BBN is perhaps the most stunning underappreciated fact about our world, even amongst physicists.

You are not the first that thought about that possibility, there's a lot that we observe that is expected result of the Big Bang and that wouldn't exist otherwise:

http://en.wikipedia.org/wiki/Big_Bang#Observational_evidence

As the article itself mentions, the Big Bang hypothesis did not become an accepted theory just based on the single piece of evidence that other galaxies seem to be receding from ours. Indeed, the term "Big Bang" was originally coined as derogatory by the famous astronomer Sir Fred Hoyle, a steadfast supporter of the competing Steady State hypothesis [1]. Many in the astronomer community found the idea of the universe having a beginning simply preposterous. However, in the end, it was the model that best matched observations, and thus became (perhaps reluctantly on some people's part) accepted. This is how science is supposed to work.

[1] http://en.wikipedia.org/wiki/Steady_State_theory

"don't we need to understand the /actual/ creation of space and matter in totality"

Well, there are some hypotheses on what caused the Big Bang in the first place (and as a result, all of space, time & matter) but they are currently relegated to thought experiments. We just don't have the technology yet to test them. There might be some things that could show up in more detailed observations of the cosmic microwave background, things which if found would be suggestive, but the evidence still wouldn't be conclusive.

You can google "what came before the big bang" to read up on those hypotheses. Keep in mind that they are thought experiments. Pop-scientists will often talk about those hypotheses like they're fact, but the truth is there's still a long way to go.

Yes, there is basically no real evidence for any of the multiverse hypothesis. If they're right then physics and cosmology has nearly ended in its reach of what is knowable. It feels so much like this is premature surrender and physicists are turning themselves into religious philosophers just because they can't think of anything better. If we had been backed into this wall for hundreds of years with nothing better, then I might agree that the program was over, but I think the whole anthropic/multiverse idea is a condemnation of how sold physicists and cosmologists have gotten on one possible solution, and indicative of the fossilization of some of their ideas. We need a new Einstein to do away with the modern-day aethers...

I thought that article was a great read, combining historical perspective with technical detail that wasn't glossed over.

Keep in mind that the 2 megasecond exposure was not done all at once. It consists of many shorter exposures (probably about 10-20 minutes apiece) added together. If the exposure had been done all at once, it would have saturated. Moreover, cosmic rays would ruin large regions of a single long-exposure image.

They mean that when hydrogen gas is highly energized/ionized, the (hot) hydrogen electrons exist ripped out of the atom and this state prevents hydrogen from collapsing on itself to form stars and stuff.

Really? That's what you have to contribute in conversation to a discussion about thousands of years of discovery about the nature of reality itself? We know a lot more than "shit".