Immortality.
In movies, kings are always searching
for the secret to immortality.
But is immortality really a good thing?
To a ten-year-old boy,
one year is the same as 10% of his life.
To his forty-year-old mother,
one year is merely 2.5% of her life.
The same year, 365 days,
can feel differently to different people.
If we live until we're 82,
that's about 30,000 days.
If this boy lives for 30,000 years,
a year to him could feel like a day.
And if this boy's emotions sustain
through the potential boredom
of living for millions of years,
he might become extremely lonely and sad,
knowing he has and always will
outlive everyone he has ever loved.
But what if everyone were immortal?
Well, first off, Earth is only so big.
So, where would we all live?
(Grunts)
"Excuse me!"
"That's my face!"
"Stop it!"
"Pardon me."
"Tight in here!"
Do you remember what you did last year
or when you were five?
How much of your past have you forgotten?
If you have trouble remembering
what you did when you were five,
how will you remember what happened
if you were alive a thousand years ago?
A million years ago?
We don't remember every single
detail of our past
because our brains have a limited capacity
and we replace useless memories,
like middle school locker combinations,
with relevant information.
If this immortal boy finds a companion
to fall in love with
once every hundred years,
he would have ten thousand girlfriends
in a million years.
And how many of those
ten thousand girls' names
will he be able to remember?
This changes what a meaningful
relationship means, doesn't it?
Another tricky thing about immortality:
Human beings have not
always looked the same.
This can be explained
by Darwin's theory of evolution.
For instance, if women find
taller men more attractive,
then more tall men would mate
and have children,
putting more tall genes in the gene pool.
That means, in the next generation,
more children will have
the genes to be taller.
Repeat that process for a million years
and the average height
will be a lot taller
than the average height today,
assuming there's no natural disaster
that wipes out all the tall people.
Our ancestors were short, hairy apes.
We still have body hair,
but we don't look like apes any more.
If you're the only person who is immortal,
while everyone else keeps evolving,
generation after generation,
you will eventually look quite different
than the people who surround you.
"Hi, how you doing?"
If one of our ancestors, apes,
is still alive today,
how many people will make friends with it
instead of calling
the Museum of Natural History?
And one more physical consideration
for immortality:
Scars.
After all, immortality doesn't
automatically translate to invincibility,
it just means you cannot die.
But it doesn't guarantee
what condition you'll be alive in.
Look at your body
and count how many scars you have.
If you have made this many permanent scars
within your life,
imagine how much damage you would have
if you were one thousand years old!
Now, there are approximately
185,000 amputation-related
hospital discharges
every year in the U.S.
These injuries are due
to accidents or illnesses.
Certainly the percentage is low
comparing to the total population
if you only live for a hundred years.
However, if you've been alive
for over one million years,
the odds of still having
all your limbs are pretty slim.
What about little accessories,
like your eyes, your nose, your ears,
fingers or toes?
What about your teeth?
What are the odds of you
keeping your dental health
for a hundred years?
A thousand years?
One million years?
You might end up looking like
a horribly scuffed-up Mr. Potato Head
with missing pieces and dentures.
So, are you sure you want to live forever?
Now, which superpower physics lesson
will you explore next?
Shifting body size and content,
super speed,
flight,
super strength,
immortality,
and --
invisibility.