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.