Alicia: Do you think time is real?
For example, sometimes an hour can feel very
short and sometimes it can feel very long
depending on your perception.
So then is time subjective?
If it's a measurement of something what is
it a measurement of?
I'd really like to know your thoughts about
time.
Thank you.
Bill Nye: Alicia, that is fantastic.
Notice that in English we don't have any other
word for time except time.
It's unique.
It's this wild fourth dimension in nature.
This is one dimension, this is one detention,
this is one dimension and time is the fourth
dimension.
And we call it the fourth dimension not just
in theoretical physics but in engineering.
I worked on four dimensional auto pilots so
you tell where you want to go and what altitude
it is above sea level and then when you want
to get there.
Like you can't get there at any time.
We have a whole bunch of other words.
We have appointments.
We have morning, afternoon, evening, noon
time.
We have a whole bunch of words describing
periods of time, but when it comes to actual
time we just have this one word it's a strange
and surprising thing.
So along this line, in my opinion, which as
you know is correct, I'm kidding, in my opinion
time is both subjective and objective.
What we do in science and engineering and
in life, astronomy, is measure time as carefully
as we can because it's so important to our
every day world.
You go to plant crops you want to know when
to plant of them.
You want to know when to harvest them.
If you want to have a global positioning system
that enables you to determine which side of
the street you're on from your phone you need
to take into account both the traditional
passage of time that you might be familiar
with watching a clock here on the earth's
surface and the passage of time as it's affected
by the speed of the spacecraft and the passage
of time as it's affected by the gravity of
the earth itself, both special and general
relativity.
It's astonishing.
So, we work very hard to measure time with
all sorts of extraordinary clocks, but there
is no question with our brains, which are
wet chemical computers, we lose track of time.
Sometimes it feels short, sometimes it feels
long and it's just the nature I think of being
constrained by measuring time with our brains.
This is why we build instruments to measure
time outside of ourselves externally.
But it is a great question.
And then the whole idea of science really
started with this thing people used to call
natural philosophy.
And when you throw in the word philosophy
for me you start asking this question like
can you know anything, let alone what time
it is or how long it's been since something
happened or when something will happen in
the future or whether or not it will happen
at all, these are philosophical questions.
I feel that you can get yourself pretty spun
up in saying to yourself there's no way to
know anything.
Philosophically you can't know anything.
On the other hand, it seems to me we can know
a great deal objectively about nature and
that includes time and it's passage.
One last thought Alicia, when I think about
my grandfather he had no idea, no understanding
of relativity.
Not because he was a bad person, because no
one had discovered it yet.
And so I just wonder what else it is about
the nature of time or the nature of what physicists,
astrophysicists like to call space time where
you talk about these four dimensions at once
X, Y, Z, and T. I cannot help but wonder there
is something else undiscovered about time
and perhaps you and I will be alive, not much
more time will have passed before this discovery
is made.
Carry on.
Excellent question.
Thank you.
