For the last week or so, on a physics blog I follow, I’ve been part of a debate about the nature of time. It’s been interesting and fun, but the conversation has reached that point where folks are mainly maintaining their positions, and it seems that the matter has stalled.
Some of the on-going assertions bemused me so much, that I was about to tender one more rebuttal comment… When I remembered what a wiser person, “back in the day” (before the web), said about online debates: State your view. Support it further if you need to address points raised. But once you’ve covered it well enough, just stop. After that, you’re just wasting your time; it’s rare that anyone changes their mind on the internet. Including yours.
Fair enough. I can natter on about it to myself on my own blog, though…
And that’s all this is — me over in my corner muttering to myself about someone being wrong on the internet. Again. But at least I can info dump here and get it out of my system.
Since this is out of sight of those in the debate, I’m just going to ramble about some ideas expressed within that debate. I’ve heard those ideas elsewhere, they’re not new, so this goes beyond any participant, and I’m not pointing any fingers.
It should go without saying this is all just my own opinion. No one currently really knows what time is or why it flows in only one direction. We don’t know if it’s continuous or if there is some (very short!) minimum time — a time quantum (a chronon).
As it turned out, the interview didn’t really go anywhere, but the comment section got lively. People put forth a number of their own theories about time, some that struck me as… probably not likely.
Keying off those basic ideas, my own ideas (caveat emptor):
Time is unordered.
Most of these ideas propose to show something is “wrong” with time, therefore it can’t be fundamental (or in some cases, even real). The seeds were planted by Rovelli speaking several times about time being more complicated than our experience shows. From the interview, it’s not clear how far he meant that.
One such view holds that, because of how relativity screws up time — simultaneity is strictly local — there is no ordering to events, thus our sense of any “timeline” is an illusion.
But causality orders time. No event can precede its cause. That’s the timeline.
That we can’t untangle the plate of spaghetti doesn’t mean the universe can’t.
It’s like orbits. We can’t calculate a bunch of them accurately, but the universe does it all the time. (That said, between Special Relativity (SR) and General Relativity (GR), that plate of spaghetti is seriously tangled.)
Under GR, clocks run slower in higher gravity (from the perspective of those outside — those local to the clock see outsiders’ clocks running fast).
That means the center of the Earth is younger than its surface. The center of Jupiter is even younger than its surface, and the center of the Sun is younger still than the Sun’s surface.
And under SR, things moving relative to each other have different clocks, so the fabric of time is as complex and tangled as smoke in air.
But nature (or physics, whatever) keeps it all straight just like the orbits of planets. Causality trumps all! Light cones never lie!
Time emerges from change.
Another approach holds that time emerges from something more fundamental. One view seems to be that time somehow emerges from change.
I don’t understand how this is possible. We define “change” as two states separated by time. First, one thing is true, then, something else is true. You can’t discuss change except in the context of time.
Rovelli, illustrating how time is more than what we perceive, mentioned how we perceive the Earth’s surface as flat, but from a distance it appears round. (And, obviously, the longer view is the “more correct” one.)
This idea morphed into the idea that such a change in perspective is a change that can occur without time, which supposedly demonstrates that change can be more fundamental than time.
I don’t see any coherence to the idea; it’s doubly incorrect in my view.
Firstly, an abstract change of perspective is not at all the same sort of change we mean when we speak of change in physics.
Secondly, even an abstract change requires first one state, then another state. There is always an ordering of states in time. We can reverse the order to obtain a different effect, thus demonstrating the fundamental nature of time when it comes to change.
Not the other way round. A property can’t arise from something that is necessary to its definition.
time = change
To the extent anyone in the debate actually claimed that time and change were synonymous (which I’m not sure anyone actually did), that’s clearly false.
Change is defined in the context of time, but its description involves more than just time. A system in one state at time changes to another state at a later time. The definition requires two points in time and two states for the system.
A more complicated, less fundamental, concept than time.
Lab results show problems with SR.
Or so it was claimed.
I’m sure this is a misunderstanding. If it were true, it would be huge news. SR is one of science’s most rigorously — and successfully — tested theories. Any violation of it would rock science.
(Like faster than light neutrinos. Which were also totally not true.)
In fact, I read recently that astronomers had an opportunity to track a Milky Way core star as it whipped around the putative Black Hole at the center. Because of the star’s close passing distance, as well as its speed, it provided a test of both GR and SR in an extreme domain.
Einstein won again. Spectra dead on per theory.
So I’m very dubious about claims there are problems with SR.
Time dilation is a mathematical artifact.
It’s not clear if the person making this argument (who is also the interviewer) really means time dilation doesn’t happen, or if it does but is explained in some other way. (I asked; wasn’t answered.)
The reality of time dilation has been well-explored, and it definitely really does happen. Not only in the lab, either. Muons created in cosmic ray collisions with the upper atmosphere reach the Earth’s surface because they are traveling so fast. (If they weren’t, they’d decay much faster.)
It further appears there is a misunderstanding here, too. The idea that time dilation isn’t real is apparently due to early thinking by Lorentz, but that was pre-Einstein. Later Lorentz clearly agreed time dilation is real.
So I’m not sure what’s going on there.
As a closing thought, I have at least one data point suggesting I can be wrong on the internet and be corrected. (I’d like to think it isn’t unusual, actually.)
Over on a SF blog I mentioned my belief that FTL radio might be possible under certain special circumstances (i.e. matched frames). Someone who knew better than I corrected me, and provided an example that made clear what I hadn’t seen before.
And, nope, sorry, no FTL Radio. (Gonna have to write a followup post now!)