What’s more real: time itself, or your perception of it?

We know that time in some sense is that

which allows change to take place.

>> Time is complicated. I think more so

[music] than space. We take left turns.

We write to we have a map of space. Time

is this one-way street.

>> Time is rubbery and can speed up or slow

down. Time is one of the unsolved

mysteries in neuroscience.

>> Matter is made of molecules and atoms.

Could it be that time is also made of

some kind of ingredient?

Time is something that we never evolved

to manipulate. So the brain is [music]

indeed an illusion factory. Common

example is color. Color doesn't exist

[music] in the physical world. What

exists in the physical world is

wavelength of the electromagnetic

spectrum. Our perception of color

evolved to provide information about the

external world. [music] The color of a

snake might tell us it's poisonous or

not. Presumably, our sense [music] of

the flow of time should be adaptive.

Virtually every human on the planet has

this unmistakable feeling [music] of

time flowing. We have to decide if that

feeling is something that evolved

because it offered a selective advantage

and correlates with a property of the

universe that [music] really exists or

if in contrast it's an illusion that

doesn't correspond to any property.

The experiment had never been done about

why time seems to move in slow motion

when you're in a a life-threatening

situation. I found a way to study it by

by dropping people from a 150 foot tall

tower and measuring their time

perception on the way down. That [music]

led me to understand when you're in a

life-threatening situation, your brain

writes down memory much more densely.

People don't actually see time in slow

motion during an event. Instead, it's a

completely retrospective assessment. How

long [music] something took has a lot to

do with how much energy your brain has

to burn during the event and how much

footage you have of the [music] event.

Is time some fundamental quality of

reality or is it something that our

brains impose on our perceptions to

organize our experience? Go out into

[music] space near the speed of light.

Your time is elapsing much slower than

time back on [music] Earth. If you go

and hang out near the edge of a black

hole, time again will elapse more slowly

[music] for you depending on how close

you got to the edge of the black hole

and how long you hung out there. There

might be [music] ingredients of time

that bear no resemblance to time as we

experience it. That might be the more

fundamental way that time is [music]

injected into the makeup of reality.