Tag Archives: Physics

A Brief History of the Philosophy of Time by Adrian Bardon

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Someone thought it would be a good idea to call this book A Brief History of the Philosophy of Time, no doubt as an allusion to Stephen Hawking’s A Brief History of Time. The book’s focus isn’t historical, however. It’s a brief introduction to the philosophy of time, with chapters devoted to the nature of time, its direction, its passage, and a few other standard topics. Professor Bardon’s explanations of the issues are almost always clear and the book is relatively easy to read.

The most interesting aspect of the book is Bardon’s strong preference for the “static theory of time”. That’s the counter-intuitive view that the apparent passage of time is an illusion, or, more precisely, that it’s merely the result of our human perspective. The static theory isn’t new. The Greek philosopher Parmenides argued for it 2,500 years ago. J. M. E. McTaggart unhelpfully gave the name “B-series” to this conception of time, distinguishing it from the more familiar “A-series” or “dynamic theory of time” that most people accept, according to which time passes as events move from the future to the past:

The static theorist believes in change, but only understood in a way that doesn’t commit one to the passage of time: Change, on the static theory, is to be understood as merely referring to the world being timelessly one way and timelessly another way at a subsequent moment.  

The B-series places every event in the history of the universe on an unchanging timeline. On this view, it‘s appropriate to describe every event as either earlier than, later than or simultaneous with every other event. But there is no special significance to the present moment (the “now”). It’s no more descriptive to say that an event is happening “now” than to say that a location is “here” or a direction is “up”. The idea that some events are in the past or future compared to the present moment is an illusion. So far as our “block universe” is concerned, all moments in time are equally real, not just the present one.

The static view of time isn’t universally accepted, but it’s popular among physicists and philosophers. One reason Bardon accepts it is that he thinks McTaggart’s arguments for the static theory and against the passage of time are “devastating”.

I think they’re confused. For example, McTaggart and Bardon hold that it’s self-contradictory to say that an event like the 1960 World Series used to be in the future and is now in the past, since by doing so we are attributing contradictory properties (being past and being future) to the same thing (a particular event). But being past or future are relational properties that vary with time. Saying an event was future and is now past is akin to saying a person was married and is now divorced, hardly a contradiction.

Bardon also presents Einstein’s theory of special relativity as a reason for doubting that time passes. Physicists have confirmed that two observers moving at great speed relative to each other will perceive time differently. For this reason, there is no place in physics for saying that two events are truly simultaneous, or which of two events happened first, except from a particular point of view: 

If there is no privileged vantage point from which to determine the “truth” of the matter – and the whole point of relativity is that there is not – then temporal properties like past, present and future cannot possibly be aspects of reality as it is in itself. They must be subjective and perspectival in nature.

Yet the theory of relativity pertains to how events can be observed or measured, given the constant speed of light. It doesn’t tell us how reality is “in itself”; it tells us how reality is perceived. Just because we can’t always know when two events occurred doesn’t mean there is no truth to the matter. A truth can be unknowable.

Furthermore, if relativity implies that there is no objective A-series past or future, it also implies that there is no objective B-series “earlier” or “later”. Bardon tries to draw a distinction between relativity’s implications for the dynamic and static theories of time, but it isn’t convincing. Perhaps the book would have been better if Bardon hadn’t so clearly taken sides.

A Guide to Reality, Part 6

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In the rest of chapter 2 of The Atheist’s Guide to Reality, Alex Rosenberg explains the second law of thermodynamics and briefly addresses some of humanity’s “persistent questions” (such as “does the universe have a purpose?”). His account of the second law is much less controversial than his answers to those big, long-standing questions.

The second law of thermodynamics is usually summed up, somewhat inaccurately, as “entropy or disorder always increases”. Rosenberg, however, begins with this description:

The second law tells us that in any region of space left to itself, differences in the amount of energy will very, very, very probably even out until the whole region is uniform in energy, in temperature, in disorder…. In our universe, the arrangement of everything goes from more improbable distributions (with more useful energy) to less improbable ones (with less useful energy). And the same goes for any self-contained part of the universe (28-31).

In other words, everything that somehow became organized will eventually fall apart (which is one reason why long-abandoned houses invariably look worse than occupied ones). An organized system is unlikely. Energy must be applied to create it and, without further energy being added to the system, it will sooner or later revert to the much more likely state of being disorganized.

Consider, for example, the atoms and molecules that make up the Eiffel Tower. It’s much less likely that they ended up being arranged in that shape than if they were randomly spread around here and there:

The most probable distribution of energy and disorder in the universe is the completely even distribution of everything….[That] is the state toward which, according to the second law, everything is moving, some places slower, some places faster, but almost inexorably. This evening-out of things – from molecules to galaxies – from less probable to more probable distributions is the rule of the universe (31).

Increasing disorder isn’t completely guaranteed, however, which is why Rosenberg says “almost inexorably”. As he explains, the second law merely means that the tendency toward disorder is extremely, extremely probable. For example, when you pour cream in your coffee, the two liquids quickly mix together. But there is nothing in the laws of physics that prohibits the cream from spelling “Good Morning” when you drop it in.

So why are there so many unlikely, highly-organized clumps of matter around (like us)? Despite what some evolution-deniers think, these clumps aren’t counterexamples to the second law. Nor are they bizarre but permissible, random bits of organization:

These are regions of the universe in which the maintenance of order is being paid for by using much more energy to produce [and maintain] the orderly things than the amount of order they produce or store. Each region of local order is part of a bigger region in which there is almost always a net increase in entropy…. Most biological order is preserved for long periods, but at the cost of vast increases in disorder elsewhere (32).

Physicists believe that the universe began in a state of incredibly extreme heat and density. Rosenberg says that this primordial state was both highly unlikely and highly organized, although “organized” might not be the best word.

If everything in the pre-Big Bang universe was evenly distributed (unlike all the molecules in the neighborhood of, for example, the Eiffel Tower), it seems odd to say that it was organized at all. It’s not as if there was some cold, thinly-populated, disorganized space different from the hot, dense stuff, waiting to be filled up. The dense stuff that existed at that point was All There Was. Unless it had some internal structure, we might as well say it wasn’t organized at all. At any rate, the universe as a whole has been falling apart (moving toward perfect equilibrium) ever since the Big Bang, despite the fact that here and there stars and galaxies eventually came to be.

Somewhat controversially, Rosenberg suggests that the second law also explains why time appears to have a “direction”:

Hard to believe, but the second law is where the direction of time, its asymmetry, comes from. It cannot come from anywhere else in physics. By process of elimination, the time order of events from earlier to later is a consequence of the second law…. None of the basic laws of physics [allow us to tell which way is past and which way is future] except for one: the second law of thermodynamics. It makes a difference between earlier times and later times: the later it gets, the more disorder, or entropy, there is (33-35).

On the other hand, another philosopher, Adrian Bardon, argues in A Brief History of the Philosophy of Time that the second law can’t explain the apparent direction of time. The second law is merely probabilistic, as Rosenberg admits. Increasing entropy is extremely, extremely likely, but not absolutely guaranteed, even for the universe as a whole. But the direction of time, if it’s real, is supposed to be unchanging, not probabilistic. Bardon concludes that the direction of time can’t be the same as the one-way, thermodynamic “direction” suggested by the second law. He thinks the fact that these two “directions” appear to go the same way is just a striking coincidence.

This brings us to Rosenberg’s brief answers to a few of those big, persistent questions. This post being so long already, however, I’ll end for now with a brief summary of his conclusions:

Where did the Big Bang come from? We don’t know, but the best current theory is that it randomly emerged from the “multiverse”. Our universe is just one of many.

Well, why is there a “multiverse” then? There’s no reason for it to exist. It just does. Get over it already!

But isn’t there some purpose to the universe? No, there isn’t any purpose to it at all.

But why then does the universe have the physical laws and parameters that allow intelligent life to exist? Given the vast number of universes popping into existence, it shouldn’t be a surprise that some of them end up being like this one. Somebody had to get a winning ticket in the cosmic lottery. It happened to be us.

In our next installment: Oh, really?

A Guide to Reality, Part 5

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Alex Rosenberg, the author of The Atheist’s Guide to Reality, argues that “we should embrace physics as the whole truth about reality”. On the face of it, that’s a remarkable statement open to obvious challenges. 

Rosenberg, however, acknowledges that parts of physics are relatively speculative, unsettled or even inconsistent. It’s the solidly-confirmed part of physics that he’s talking about, the part of physics that is “finished” and “explains almost everything in the universe – including us”. What he’s really claiming, therefore, is that settled physics is the whole truth about reality. 

But is settled physics actually true? Philosophers disagree about what science is, what truth is and, not surprisingly, how close science gets to the truth, but I agree with Rosenberg that settled physics seems to be true. The predictions of special relativity, for example, appear to be 100% correct. (This isn’t to deny that some settled physics might become unsettled one day.) As evidence of the reliability of physics, Rosenberg points out how precise some predictions are: “quantum electrodynamics predicts the mass and charge of subatomic particles to 12 decimal places”. Those predictions are “true” in any reasonable sense of the word, even if physicists eventually refine their predictions to even more decimal places.

Some philosophers and scientists don’t accept Rosenberg’s “scientific realist” view, however. They think science is merely a tool that allows us to get things done. Questions like whether electrons or other theoretical entities really exist as physics describes them are put aside, since they’re viewed as unanswerable and irrelevant. Personally, I think physics allows us to get things done because it’s true, and furthermore it’s true in the sense that the objects and events physics describes are real, whether they’re observable or not. I believe that’s Rosenberg’s opinion too.

The second, more interesting challenge to Rosenberg’s view of physics concerns his claim that settled physics is the “whole” truth about reality. Clearly, there are mathematical and logical truths, which aren’t part of physics, but I take Rosenberg to be referring to truths about the universe and its contents, i.e. “real” stuff.

Nevertheless, if physics isn’t finished, it can’t be the “whole” truth. There must be some physical truths yet to be discovered (for example, what’s the story on dark matter and dark energy, two big things we know little about?). So Rosenberg’s claim that we should embrace settled physics as the whole truth about reality should really be understood as “settled physics is the only truth about reality we currently have”.  

Two obvious questions remain, however. Do we discover the truth from sciences other than physics? And do we learn anything true about the world even when we aren’t doing science?

Well, most people would agree that chemistry, for example, is a science that gets at the truth if any science does. Rosenberg clearly knows about chemistry, so why would he deny that chemistry is as valid as physics? The answer is that he thinks physics has shown there is nothing in the universe except fermions (e.g. quarks) and bosons (e.g. photons). From the idea that fermions and bosons are the only things that really exist, he concludes that all of reality can be explained in terms of those sub-atomic particles. After all, everything in the universe involves elementary particles being somewhere or doing something. Since physics is the science that tells us all about elementary particles and what they do, it’s the fundamental science. Using physics, therefore, we can explain chemistry, which we can then use to explain biology. Another way of saying this is that biology is reducible to chemistry and chemistry is reducible to physics. Knowledge of physics is the only knowledge that counts, because “the physical facts fix all the facts”, including chemical and biological facts.

The big problem with this point of view, aside from the difficulty in actually carrying out such reductions (replacing chemistry with physics, for example) is that fermions and bosons do such interesting things when they interact or are arranged in certain ways. Put some together and you have atoms; put some atoms together and you have molecules; put some of them together and you have cells. Once low-level particles are arranged as, for example, clouds or baseballs or trees, patterns or regularities in the behavior of these higher-level entities emerge. There are new facts to be learned.

If the universe were merely a collection of sub-atomic particles randomly scattered about, there wouldn’t be any chemical or biological facts for chemists and biologists to discover. But the particles in our universe aren’t randomly scattered. They’ve clumped together in various ways. Acquiring knowledge about these clumps (of which you and I are examples) is what chemists, biologists and other scientists (geologists, astronomers, psychologists, etc.) do. Rosenberg knows this, of course, but for some reason downplays it, choosing to focus on physics as the sine qua non of science. In virtue of its power and generality, physics should be embraced as the most fundamental science, but it clearly isn’t the only science worth embracing. 

The other question raised by Rosenberg’s scientism (or physics-ism) is whether we can add to our knowledge when we aren’t doing science at all. Rosenberg doesn’t seem to think so. Although science is built on observation, he is extremely skeptical about what can be learned by simply looking and listening. He also seriously mistrusts introspection. More on this later. 

Next: The 2nd Law of Thermodynamics and us.

A Guide to Reality, Part 4

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Chapter 2 of The Atheist’s Guide to Reality is probably the key chapter in the book. That’s where Professor Rosenberg lays out his view of physics and the nature of reality. He doesn’t mince words:

Everything in the universe is made up of the stuff that physics tells us fills up space, including the spaces that we fill up. And physics can tell us how everything in the universe works, in principle and in practice, better than anything else. Physics catalogs all the basic kinds of things that there are and all the things that can happen to them (21).

According to Rosenberg, “we should embrace physics as the whole truth about reality”. Why? Because science is a cumulative process, in which findings are confirmed, corrected or refuted, resulting in a solid foundation. Physicists are still learning things, but the “part of [physics] that explains almost everything in the universe – including us – is finished, and much of it has been finished for a century or more” (21).

Physicists, in particular, have discovered that everything in the universe is composed of either fermions (such as quarks, electrons and neutrinos) and bosons (like photons and gluons), and combinations thereof (like protons and molecules). Fermions are usually associated with matter, while bosons are usually associated with fields and forces. Rosenberg says that’s all there is:

All the processes in the universe, from atomic to bodily to mental, are purely physical processes involving fermions and bosons interacting with one another…Physical theory explains and predicts almost everything to inconceivably precise values over the entire body of data available…From a small number of laws, physics can neatly explain the whole trajectory of the universe and everything in it…The phenomenal accuracy of its prediction, the unimaginable power of its technological application, and the breathtaking extent and detail of its explanations are powerful reasons to believe that physics is the whole truth about reality (21-25).

But what about the other sciences? Surely, chemistry and biology, for example, say something true about reality. Rosenberg, however, argues that physics explains chemistry and chemistry explains biology. Everything that happens in your body is a chemical process, and every chemical process is a physical process:

The only causes in the universe are physical, and everything in the universe that has a cause has a physical cause. In fact, we can go further and confidently assert that the physical facts fix all the facts … including the chemical, biological, psychological, social, economic, political and other human facts (25-26).

He left out the geological and cosmological, but you get the idea. Higher-level sciences are in principle reducible to lower-level sciences. Philosophers call this view “reductionism”. Rosenberg is clearly a “reductionist” of some sort. A similar claim is that all higher-level facts depend or “supervene” on lower-level facts (this principle is called “supervenience”). Rosenberg asks us to imagine two regions of space-time, our own plus another millions of light-years away, in which every fermion and boson is arranged exactly the same way. In such a case, everything else in the two regions would be the same too. Regardless of the regions’ respective histories, if all the sub-atomic particles are arranged the same way, the two regions will contain the same rocks, the same birds and bees, the same political institutions, the same music, the same people with the same memories and thoughts. Physics fixes all the facts.

Next time, before continuing with chapter 2, we’ll consider whether it’s reasonable to “embrace physics as the whole truth about reality”.

A Guide to Reality, Part 3

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Continuing to work through The Atheist’s Guide to Reality by Alex Rosenberg:

Professor Rosenberg begins chapter 1 by explaining why he’s not going to spend much time arguing for atheism: others, especially David Hume, have already done that quite well; such arguments, even very good ones, don’t convince true believers; and anyway, it’s more important to understand how science can help us live without illusions than to keep talking about religion.

Instead, Rosenberg is going to discuss a view called “scientism”. As he notes, “scientism” is usually applied in a negative way to people who supposedly worship science, or try to extend it beyond its natural borders, or simply take it too seriously. Rosenberg welcomes the term, defining it this way:

[Scientism] is the conviction that the methods of science are the only reliable ways to secure knowledge of anything; that science’s description of the world is correct in its fundamentals; and that when “complete”, what science tells us will not be surprisingly different from what it tells us today (6-7).

The idea that the current scientific description of the word is fundamentally accurate is known among philosophers as “scientific realism”. The Stanford Encyclopedia of Philosophy defines it as “a positive epistemic attitude towards the content of our best [scientific] theories and models, recommending belief in both observable and unobservable aspects of the world described by the sciences”. In other words, science is a highly reliable way to acquire knowledge of the world. Science allows us to learn about the world as it is, independent of our minds. Science even allows us to find out about things we can’t directly observe, like the Big Bang and sub-atomic particles.

Rosenberg is clearly a scientific realist. Not all philosophers are (they, in fact, disagree to some extent about what science is). But Rosenberg’s scientism goes beyond simple scientific realism when he asserts that “the methods of science are the only reliable ways to secure knowledge of anything”.

Maybe he’s exaggerating on purpose (not something philosophers ordinarily do), but are you and I doing science when we look out the window and agree that it’s snowing? Is a student doing science when she concludes that Socrates was mortal if Socrates was a man and all men are mortal? As Rosenberg knows, of course, science relies on occasionally unreliable activities like seeing and hearing in order to gather evidence. Even though scientists don’t rely on a single person’s observations, they do use the same perceptual abilities the rest of us employ to acquire knowledge. In addition, most of us would agree that people clearly know lots of things that aren’t “scientific” in the usual sense (including math, logic, historical facts, cultural practices and whether the Ford is in the driveway).

Perhaps it’s enough that an adherent of scientism believes that, when applied correctly, the various methods of science are by far the best ways we have to get at the truth about many or most features of the world. Those methods include classification, observation, experimentation, measurement, replication, discussion, publication and other things physicists, chemists, biologists and psychologists regularly do.That seems right to me, but I don’t think it’s enough for Rosenberg.

Before moving on, I should mention that Rosenberg also considers this question: if science is such a reliable method of determining the truth, why do so many people reject scientific conclusions? One reason, of course, is that scientific results are often revised. Another is that scientists often disagree among themselves, especially on topics that make the news, in some cases because they are influenced by un-scientific factors, like working for Exxon. Yet another big reason why many are skeptical about science is that scientific conclusions often make people uncomfortable (as in the case of climate change, for example).

Rosenberg, however, mainly discusses the human need for “stories”, by which he means our tendency to understand the world in terms of personalities and purposes. He argues that our ancestors became good at recognizing and interpreting purposeful behavior because that skill made it much easier to live and prosper among other people. Evolution, however, overshot the mark. People heard thunder and concluded that Someone was angry. Today, according to Rosenberg, people have trouble understanding math and physics because their subject matter doesn’t include human beings or other creatures doing things. In other words, science is especially hard because most people haven’t been built (through evolution) to understand it. Religion, on the other hand, often involves stories, which we generally find more easy to understand than science.

In the next installment: physics and the nature of reality.