
Can We Escape from Time? - Hooke
http://www.nybooks.com/articles/2016/11/24/can-we-escape-from-time-james-gleick/
======
gwern
"What would be good, though, would be for someone to call us back when the
thinking leads to something, anything, that we can see or feel or sense or
even understand—because all this astonishingly brilliant thought and science
and learning and history, all these amazing stories, as far as I can tell,
have no consequences at all. Our commonsense subjective understanding of time
is as telling, as tyrannical, as it ever was. A century-plus of fervent
speculation and analysis of time and time travel have led to exactly no
outcomes. We are as stuck in the present, as irrevocably exiled from both past
and future, as ever."

Einstein's time dilation has practical consequences: aside from being able to
observe the slowdown in atomic clocks taken up in airplanes and the many
consequences in astronomy, we also have GPS, which would not work without
taking relativity into account. If GPS doesn't count as a 'consequence' or
'outcome' due to a non-traditional understanding of time, nothing does!

~~~
dom0
This is a relatively common misconception. The location calculation in GPS is
independent of any time dilation between the GPS receiver and the satellites
(as long as the satellites have roughly equal dilation), because the receiver
clock is derived from the satellites' signals. This is also the reason why you
need at least four satellites for a 3D fix, and three for a 2D fix - you are
always deriving an additional unknown variable, time. (And this is also the
reason why a GPS time receiver works with only one satellite: the position is
locked when they are set up, after that they can work with 1+ satellites. More
satellites will reduce errors, though.)

The time dilation is therefore only compensated so that you can use a GPS
receiver as a very accurate, absolute clock.

~~~
WJW
Technically the fourth variable that a receiver solves for is the clock error
in the receiver, not the actual time (though that then follows easily enough).
The system of equations is only solvable because it is assumed that the clock
error of the satellietes relative to each other is zero. I'm not convinced
though that time dilation is the same for all the satellites, since they are
not all in the same orbit.

Since the system works by determining signal delay between the satellite and
the receiver and the signals move at (rougly) the speed of light, even an
nanosecond error in time is already a 30 cm error in position. According to
[0] the clock drift due to relativistic effects would be over 45000
nanoseconds per day. So keeping the clocks synchronized for all the satellites
is crucial and relativistic corrections are super important for accurate
positioning.

[0]: [http://www.astronomy.ohio-
state.edu/~pogge/Ast162/Unit5/gps....](http://www.astronomy.ohio-
state.edu/~pogge/Ast162/Unit5/gps.html)

~~~
dom0
> According to [0] the clock drift due to relativistic effects would be over
> 45000 nanoseconds per day.

Between an uncorrected satellite and the receiver. This error is already
removed through the fourth variable, only the average error of the satellites
used for this remains (assuming perfect receiver etc.). So even if the
satellites where not corrected the positioning error would not be "XY
kilometers per day and climbing", the much smaller difference in time dilation
between satellites would remain though.

~~~
jayisbatman
The location calculation is completely dependent upon relativistic time
dilation.

The Navistar satellites have an orbital speed of 8,750 MPH (more than 2 miles
per second, relative to our earth surface frame), they are subject to a
relativistic time dilation adjustment of -7201ns (slower than our earth
surface frame). The location calculation cannot ignore that. The GPS signal
(radio) takes on average 1 foot per nanosecond (perhaps a slightly bit more,
but this is electromag radiation in a non-vacuum). If your receiver didn't
account for this you would be more than a mile from your actual location.
Relativity and its time dilation are required for any satellite based location
system -- unless your satellites are at altitude of zero.

------
to3m
A pretty substantial flaw in the piece, almost enough to sink it, is the
suggestion that Looper is somehow more worthy of calling out than Primer.
Tsk... somebody sack the fact checkers...

Primer:
[http://www.imdb.com/title/tt0390384/](http://www.imdb.com/title/tt0390384/)

(Interesting not least because its budget was about 50p)

~~~
lomnakkus
It's a _REALLY_ confusing film, but absolutely brilliant in the way that it
shows just how confusing a world with time travel would be[1]. The way
everything escalates in the latter half of the film is insane. For a "simple"
explanation of the plot, see [2]. Since this analysis was done by a third
party, it's obviously hard to be sure that this is fully correct, but it at
least seems very close.

[1] For anyone able to observe the multiple time lines, obviously. :)

[2] [https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-
conte...](https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-
content/images/primer-chart.jpg) (massive SPOILERS, obviously)

~~~
FeepingCreature
Also recommended: Primer commentary track. Run it beside the movie, and it'll
drop in to explain things as they happen.

[https://qntm.org/commentary](https://qntm.org/commentary)

~~~
lomnakkus
Hadn't heard of this before -- I am _sooo_ going to try this. Thanks for the
link!

------
bitL
Are we capable of existing outside time?

Imagine instead of living in an [array of time-frames], moving in one
direction, i.e. time, in a single frame only, like a snapshot (even with the
possibility to observe the whole [array of time-frames] at once). Would you
have any words to describe it? I think all our mental models would just
collapse.

~~~
NumberCruncher
Some people say time is just an illusion we use to process reallity as an
[array of time-frames]. I think what you are looking for is a kind of
enlightening which in this case would mean stepping out of the illusion of
time. Some people reported to achieve this with meditation and/or
psychodelics.

------
nol13
The basics for time travel start at CERN in about a year and end in 2034 with
the first "time machine" built by GE. Too bad we can't post pictures or I'd
show it to you.

~~~
ChuckMcM
I realize that time travel is not invented in my lifetime, if it had been I
would have traveled back to tell myself to get out of tech stocks in 1999 :-)

------
lisper
The reason we can't go back in time is that time and information (and hence
consciousness, which is made of information) are inextricably linked by
quantum physics:

[http://blog.rongarret.info/2014/10/parallel-universes-and-
ar...](http://blog.rongarret.info/2014/10/parallel-universes-and-arrow-of-
time.html)

~~~
cousin_it
Your post explains why going back in time along the same path is pointless
because you lose the information. But maybe we could take a different path
(closed timelike curve) and keep the information.

~~~
lisper
> going back in time along the same path is pointless because you lose the
> information

No, it's much deeper than that: the accumulation of information is what
_creates_ time.

> closed timelike curve

This is at the limits of scientific knowledge so there's nothing definitive
one could say about it at this point. But you might want to read this:

[https://www.scientificamerican.com/article/time-travel-
simul...](https://www.scientificamerican.com/article/time-travel-simulation-
resolves-grandfather-paradox/)

------
brianberns
"'There is no difference between Time and any of the three dimensions of Space
except that our consciousness moves along it,' says the Traveller. That turned
out, amazingly and counterintuitively, to be true. 'In surprisingly short
order this notion would become part of the orthodoxy of theoretical physics,'
says Gleick."

What? Spacetime does contain four dimensions, but the whole reason that time
travel is fiction, rather than fact, is because the time dimension is
different from the space dimensions.

~~~
Razengan
I wonder. If the universe is deterministic, and nothing is random, then Time
could be thought of as a vector whose values encompass all the properties of
everything in existence and the direction of changes in each of them. If we
knew all the "rules" that govern those changes and could make a simulation
that captured the current state of everything, we could traverse back and
forth along that vector (but probably not beyond the instant when that
simulation was turned on, because then it would have to simulate itself...)

~~~
baytrailcat
This was a prevalent idea in physics till quantum mechanics burst into the
scene. I don't remember where I saw it, this the most convincing argument I
heard regarding simulating future: Our universe is actually the most efficient
computer that can simulate the future with our physical laws. Meaning, at any
given time, it is not actually executing a pre-determined program, it is busy
computing the future.

~~~
codethief
You don't really need quantum mechanics for this argument, though. Even in a
non-quantum world, non-linear and, in particular, chaotic systems effectively
prevent you from predicting the future. While you could do it in theory, in
practice you would need do know every single variable very precisely because
the outcome of chaotic systems can change drastically due to a small change in
initial conditions (which is colloquially known as the butterfly effect).
Quantum mechanics just makes this even harder or downright impossible (think
of determining the exact values of the wave function or predicting the outcome
of measurements). But even if we did know all the variables, we'd then still
need to simulate every single atom to predict the future, so we'd basically be
building another universe. So, you're right, in that sense the universe is the
most efficient computer simulating our physical reality.

------
imchillyb
Picture Time as the surface of a pond.

Events are a stone being dropped into or skipped along the surface of that
pond. The waves produced by the event are viewable from all angles. The actual
event -the stone drop- occurs only once. The event is immutable, even though
the ripples persist and are measurable.

We may eventually be able to view the ripples in more detail, and see past or
future events. The events themselves though, are immutable. They've already
occurred or have not occurred yet. The stone does not change. The interaction
between stone and surface does not change. What changes is our ability to
decipher data from that event, not the event itself.

~~~
flatline
You could argue there is no event per se: it's all just ripples.

------
blacksqr
Not at the moment.

~~~
ExpiredLink
Not for a moment.

------
dschiptsov
Sure. Time is a mere environmentaly conditioned mental conception. No such
phenomena exist. Only environmental and social conditioning. It could only be
derived by an intelligent observer. No observer - no time. For a photon there
is no time.

BTW, conversation laws are hinting to an illusory nature of time. Change of
compound structures do exist and it is in everything we are able to observe.
But the whole is unchanged, no matter what fancy theories or simulations would
say.

~~~
camerintinbun
But for a photon, it doesn't experience time for the reason that it travels at
the speed of light. It is a slightly different phenomenon.

------
johndoez
Read my Lips, Time is Real. And no new taxes.

