0:00

You're listening to Brains On, where we're

0:02

serious about being curious. Brains

0:05

On is supported in part

0:06

by a grant from the National

0:09

Science Foundation.

0:16

This is the bus to Worcester. If

0:19

you're going to Leicester, that's

0:21

the next bus. And

0:24

if you're going to Bermuda,

0:26

take me with you please! Salutations!

0:32

One human ticket please! For

0:34

me, a human named

0:37

Henry J. Flyman.

0:40

Nice try, pal.

0:43

Read the sign. Hold your

0:45

farts till you step outside.

0:50

What? No! The

0:52

other sign! Honk

0:55

if you're gaga for Gouda? No!

0:59

This sign! No flies

1:02

allowed. Oh, how

1:04

did you... How

1:06

did I know you were hundreds of flies in

1:09

a trench coat? Well, maybe

1:11

the fact that you were all floating. Or

1:13

that buzz. Or your face

1:16

is literally a ball of

1:18

flies spinning around in circles. But

1:21

why? Why can't flies

1:23

step onto the bus? Flying

1:27

to Worcester takes so

1:29

long.

1:30

Because

1:33

if we let you on, you'll be flying there mid-air,

1:35

not touching a seat or the ground. And

1:38

when I speed up the bus, we'll

1:41

go forward and you won't!

1:43

Splat! It's fly-guts-o-rama

1:46

all over the back of the buzz. Wait,

1:51

that's not how physics

1:53

works. Pretty

1:56

sure it is, according

1:59

to TikTok. I vaguely remember?

2:01

No. I may be hundreds

2:03

of flies in a trench coat, but

2:06

I can assure you that is not

2:08

how physics works. If

2:11

that were the case, then if

2:13

I hovered here right now, not

2:16

touching the ground, then you

2:19

would move away from me because

2:21

you are touching the Earth, and the Earth

2:23

is always spinning. But

2:26

we're both staying

2:29

still. Well,

2:32

I'll

2:32

be. I think you may be

2:34

right. So will

2:36

you sell me a ticket now?

2:39

No way I'm selling you a ticket. Read

2:41

the sign. Oh, the

2:43

no flies sign? No,

2:46

the other, other, other sign.

2:50

The one that says, anyone who teaches

2:52

me something cool gets to ride

2:54

the bus for free. Come

2:57

on up here, pal. Superb.

3:00

Thank you.

3:11

You're listening to Brains On from APM Studios.

3:14

I'm Molly Bloom, and my co-host today is Bruce

3:16

from Wellesley, Ontario. Hi,

3:18

Bruce. Hi, Molly. You know,

3:21

one of the best parts of working on this

3:23

show is reading the many emails and

3:25

letters we receive from our listeners every day.

3:27

They're brimming with curiosity and fun

3:30

and emojis.

3:32

Lots of emojis. We got two

3:34

emails that were so similar and so

3:36

intriguing, we had no choice but to investigate.

3:39

The first one was from Uma. The

3:42

other day, I was riding the bus to school,

3:44

and there's a fly flying around. I was

3:46

wondering that if the fly was just hovering

3:48

there in the middle of the bus, shouldn't it crash?

3:51

The bus is moving fast, and the fly is not connected

3:53

to it or sitting down like everyone else. If

3:56

it did, would it crash in the back or the front?

3:58

And the second was this one. one from Hazel

4:01

and Eleanor. If a bee flies

4:03

into a moving car, does it need to fly as

4:05

fast as the moving car while it's inside

4:07

or can it just hover?

4:08

These are the kind of questions that can send your brain

4:10

in circles. Right. Bruce,

4:13

have you ever wondered something like this?

4:16

Yeah, um,

4:18

I certainly have.

4:19

Do you like thinking about these kind of brain bending

4:22

ideas? Yeah.

4:25

What do you daydream about? Life,

4:27

the universe, everything. Dolphins.

4:31

Dolphins, excellent. What

4:34

kind of questions do you have sort of about like those

4:36

big

4:37

universe questions? If

4:39

the universe is really infinite

4:42

and there's only

4:45

a finite amount of worlds

4:47

with life, because finite

4:51

is such a small amount of infinite,

4:55

it could be seen as

4:58

zero, so does that technically

5:00

mean there's no life in the universe?

5:02

Whoa, that is a big question, Bruce. I

5:05

think that's our good brain bender. Very

5:07

good brain bender. Well, to

5:10

answer this question about flies in vehicles,

5:13

we talked to someone very comfortable with

5:15

mind-bending questions.

5:17

Thank you, Kim. I've taught

5:19

physics at Michalas college for the last 50

5:22

years, so I'm a long-time

5:25

teacher.

5:26

So what's the fate of a hitchhiking flying

5:28

friend? The short answer is this. The

5:31

fly is simply hovering in the air

5:34

and the air is carried by the bus.

5:36

That means the bus is carrying the air and

5:39

the air is carrying the fly. So

5:41

if the bus is moving, the air is also

5:43

moving.

5:44

The fly can just keep hovering in the air

5:47

and be carried along like the rest of the passengers. So

5:50

if the fly is in the bus and the bus

5:52

is going down the street at 30 miles per hour,

5:55

the fly itself is not flying 30

5:57

miles an hour to keep up. It's just a little bit of a struggle.

5:59

hovering. But also the fly,

6:02

the bus, and the people on the bus, they're

6:04

all moving at 30 miles per hour because

6:07

that's how fast the bus is moving through space.

6:10

But

6:10

also maybe the fly

6:12

isn't moving at all.

6:18

That's because it's all relative.

6:21

We'll explain more about that in a second. These

6:24

questions from Uma, Hazel, and Eleanor

6:26

and their answers are very complicated.

6:30

Actually this is the kind of

6:32

question Einstein thought about. So

6:34

it's a profound question. I

6:37

want them to know that. Albert Einstein was a

6:39

scientist and when he

6:41

asked

6:44

these kinds of questions, the same kind

6:46

that Uma and Eleanor and Hazel are asking,

6:49

he came up with something called the theory

6:52

of general relativity, which was

6:54

really a brand new way of thinking

6:56

of time, space, gravity,

6:59

and the universe itself.

7:00

Essentially what Einstein said is

7:03

motion and rest are relative

7:05

concepts. That means whether

7:07

you are moving or staying still all

7:10

depends on how you are looking at it. Relative

7:12

to the bus, if you're on the bus,

7:15

you are at rest. But if you're on the

7:17

ground, then the bus is moving.

7:20

So you're sitting on the bus that's driving down

7:22

the road. In relation to the bus,

7:25

you're not moving. You're sitting still.

7:28

You look around at the floor or the seat in

7:30

front of you and it's all staying put.

7:33

But let's say I'm standing on the sidewalk

7:36

and I see you sitting on the bus through the bus

7:38

window as you go zooming by. I

7:40

would definitely say you were moving, right?

7:43

That's because relative to me, you were

7:46

moving. Whoa,

7:47

brain bending.

7:49

Here's another example from Sung

7:52

Kyu Kim. When you're on an

7:54

airplane, especially if the

7:56

flight is very smooth and

7:59

you ocean and

8:01

you don't see anything underneath except

8:03

water, then you look out the window and

8:05

you feel like the plane is not moving.

8:08

So there's no sensation of motion.

8:10

It's actually moving really fast,

8:13

over 500 miles per hour. So

8:16

it turns out you can't always

8:18

tell the difference between whether you're moving or

8:20

at rest. That's called Einstein's principle

8:23

of relativity. It's the idea that

8:25

motion and rest are relative concepts.

8:28

It depends on who's looking and how they are looking.

8:30

Right, but all of that is based

8:33

on a car or bus going

8:35

in a straight line at a constant speed.

8:37

Not speeding up, not slowing down,

8:40

no turns or bumps in the road.

8:43

If the bus or car were to quickly stop

8:45

or turn, the flying of people inside

8:48

would feel the effects. They'd all slide

8:50

forward or to the side, for example.

8:52

Then they'd suddenly feel like they were moving.

8:55

Now that you're starting to grasp relative motion

8:58

in cars and planes, ponder

9:00

this.

9:01

Even when you're sitting on the floor, no

9:04

vehicle in sight,

9:05

you're still moving relative to something.

9:08

After all, the Earth is constantly spinning.

9:10

You just don't feel it because everything around

9:13

you is moving just as fast as you are.

9:15

Not only that, but this spinning

9:17

planet is also making large circles

9:20

around the sun, so it's flying 67,000 miles

9:22

per hour relative to the sun. And

9:26

the galaxy our whole solar system is

9:29

in is moving relative to other galaxies.

9:31

So depending on how you look at it,

9:34

nothing is actually still anywhere

9:36

in the universe. Try explaining

9:39

that to someone next time they say you need

9:41

to sit still.

9:42

Mind-bendy enough for ya? It's

9:44

mind-bendy, alright? But I could go even

9:46

bendier. I was doing brain

9:49

yoga before this taping, so my mind is

9:51

super limber today. Well,

9:52

just you wait. We're going to turn

9:55

your brain into a pretzel in a minute. But

9:57

first, this idea of general relativity

9:59

is...

9:59

is very important, so important,

10:02

that we wanted to really explore it a bit. We

10:05

asked some scientists to help explain

10:07

it in different ways.

10:08

Right, you heard our bus example,

10:11

so here are some other explanations using

10:13

different ways of getting around. Take it

10:15

away, physics friends.

10:18

My

10:18

name is Andrea Bryant. I'm a PhD

10:21

candidate at University of Chicago. So

10:23

let's imagine we have a little green alien

10:26

on Saturn, and also

10:28

we have a brains-on

10:31

spaceship right outside of Saturn, looking

10:33

at the little green alien. And I'd say

10:35

that the spaceship is more or less, it's

10:37

not moving. The little green alien

10:39

would look and see this spaceship

10:42

moving, because from his point

10:44

of view, he's just glued

10:46

to Saturn as it's rotating.

10:48

But the brains-on spaceship,

10:51

since it's stationary, would see

10:53

the little green alien moving because he's

10:55

rotating with Saturn. My

10:59

name is Carlos. I'm a

11:01

PhD student in the physics department

11:03

here at the University of Chicago in

11:06

Chicago, Illinois. And I study

11:09

cosmology, which is basically the

11:12

study of the entire 14-billion-year

11:15

history of our universe.

11:16

So the sort of classical

11:19

example that we're

11:21

taught in school is that imagine you're

11:23

a sailor on a ship below deck,

11:26

and the water is really calm, and

11:28

so the ship is moving steadily along, it's not

11:31

rocking back and forth or anything. And because

11:33

you're below deck, you wouldn't be able to tell if

11:35

the ship was moving or standing

11:38

still. But then as soon

11:40

as the ship, say, starts speeding up or

11:42

waves start crashing against the ship, then

11:45

you start feeling these forces of acceleration

11:47

and you become aware that you are moving.

11:51

My

11:51

name is Jamie Valentine Miller. I'm

11:53

a patent examiner for the U.S. Patent and

11:55

Trademark Office. I'm also

11:57

the founder of African American.

11:59

Women in Physics Incorporated, which

12:02

is a nonprofit that works to help

12:04

support diversity in STEM.

12:07

There's an experiment you can try when you're on a

12:09

roller coaster or one of those drop rides. You can

12:11

put the penny on your knee

12:14

and as you drop you can see what

12:16

happens to the penny. For a bit, the

12:18

penny will stay stationary if your

12:21

eyes are open and if

12:23

you're able to really focus on it. But

12:25

that's another way to kind of think about general

12:27

relativity because even though you

12:30

are moving, the penny for a bit stays

12:32

still until gravity starts to act on it.

12:41

Okay, let's give the deep thinking

12:43

part of the brain a break and work out another

12:46

set of brain cells. It's time for

12:48

the...

12:55

Bruce, are you ready for the mystery sound? Yep,

12:58

I'm ready. All right,

13:00

here it is.

13:15

Oh, I think, I

13:18

think that

13:21

is raindrops

13:24

pattering on a metal

13:26

roof. I

13:29

like that idea.

13:30

Okay. It was noisy,

13:33

that's for sure. I don't know what it is either. So

13:35

we will have another chance to hear it and guess

13:38

and hear the answer right after the credits.

13:40

So keep listening.

13:45

We're working on an episode about how creatures

13:48

would evolve on other planets. So

13:50

we want you to do a little dreaming with

13:52

us. Imagine you find life

13:54

on another planet. How would that life

13:57

greet you? What would it sound like in

13:59

their language to

13:59

say hi, but they even have

14:02

language or maybe they would greet you another

14:04

way. Bruce, if you found

14:06

a creature on another planet, how

14:09

do you imagine they would say hi?

14:11

I didn't know it really depends on the planet.

14:13

If it were Jupiter, I think

14:15

they wouldn't have

14:18

evolved communications yet. I think they'd be

14:20

really basic because

14:22

the force of gravity is so high

14:25

that it would be really hard

14:27

for them to move muscles without training

14:30

them for Jupiter

14:32

years on end. Hmm, very

14:34

good answer. On the other hand, if

14:36

they were on Mars, then

14:39

I think they'd have a very deep

14:41

voice because of their large

14:43

lungs, which I think they would have

14:46

because of

14:48

the very thin atmosphere on Mars.

14:51

So they'd say hi like hello,

14:55

but an alien voice. Yeah,

14:57

what do you think the word for hello would be in their

15:00

language? Moo. Oh,

15:03

very nice. Can I hear that in your low voice? Moo.

15:06

Oh, very good. Very well-reasoned

15:09

responses, Bruce. Listeners, we

15:11

want to hear how you imagine an alien creature

15:13

would say hi. Record yourself and send

15:15

it to us at brains-on.org slash contact.

15:18

While you're there, you can also send us mystery sounds, drawings,

15:21

high fives, and questions like this one.

15:23

My question is why

15:25

do snails have shells and

15:27

slugs do not? You can find an answer

15:30

to that question on our Moment of Um

15:32

podcast. It's a short daily dose of

15:34

facts and curiosity you can find wherever

15:36

you listen to Brains On. Again, that's

15:39

brains-on.org slash contact.

15:41

And keep listening.

15:49

This is Brains On. I'm Bruce. And

15:51

I'm Molly. And we're talking about one of the most

15:53

important ideas in physics, relativity.

15:56

It's one of many big ideas thought

15:59

up by Albert Einstein.

15:59

Today, the word Einstein

16:02

is shorthand for genius. Someone said, wow, he's

16:04

a real Einstein. She's a real Einstein. But

16:07

Einstein himself wasn't always

16:09

seen that way. As a kid, he said

16:11

he was slow to talk. And he

16:13

didn't get great grades in school, especially

16:16

in subjects that bored him.

16:18

But when he was interested in something,

16:20

he'd often spend a lot of time

16:22

thinking about it. And when he was thinking,

16:25

he'd often make up thought experiments.

16:27

A thought experiment is when you try

16:29

to imagine something as a way of seeing

16:32

how it might work. One of his famous

16:34

thought experiments involved a person in

16:36

an elevator.

16:37

For our purposes, let's use Bob. Hi

16:41

there. Let's stick Bob in

16:43

an empty elevator. Oh,

16:46

an elevator. So fun. I

16:49

love how it has four walls. Classic.

16:52

Now, if Bob was just standing

16:55

in this elevator on Earth, and the

16:57

elevator wasn't going up or down, he

16:59

would simply feel the weight of gravity

17:02

holding him in place. Gravity is the

17:04

force that holds us down on the planet. Without

17:07

it, we'd float away.

17:09

Good old gravity. Like

17:11

a hog that keeps me grounded.

17:14

Shouldn't there be buttons in this thing? Where

17:17

am I going anyway?

17:18

But what if we put Bob and the elevator

17:21

in space where there is no gravity? Oh

17:24

boy. Okay. Am

17:26

I supposed to be floating? This

17:29

is a strange elevator. I

17:31

should call someone to come fix it. Oops,

17:34

I dropped my cell phone. And now it's

17:37

floating away. Get

17:39

back here.

17:40

Next, let's imagine what would

17:43

happen if there were rocket boosters attached

17:45

to the bottom of the elevator. When

17:47

the boosters fired up, the elevator would

17:49

start flying fast and the force of that

17:51

would push Bob back down. Suddenly,

17:54

Bob and the cell phone and anything else

17:57

in that elevator would suddenly fall back to

17:59

the floor.

21:58

bent

22:01

and kneaded like sourdough.

22:03

Right? I know. So, twist

22:06

it. So, next time you see a fly

22:08

hovering on the bus. Or a bee

22:10

flies through the window of a car.

22:12

Or something else catches your eye and

22:15

your imagination. Don't just forget

22:17

it. Follow the thought and see

22:19

where it takes you.

22:25

Movement is relative. That

22:27

means it depends on whose point of view you're

22:29

talking about. A person on a bus might

22:32

feel like they are sitting still in their seat. But

22:34

someone on the sidewalk would say they're

22:36

moving really fast. If we stand in one

22:38

place, we feel like we're still. But

22:41

if you zoom way out, we're on a planet

22:43

that is spinning and orbiting the sun. These

22:45

are some of the ideas in Albert Einstein's

22:47

theory of relativity. He came up with these

22:49

thoughts and many more using his

22:52

imagination.

22:53

That's it for... Hey!

22:55

Anyone there? I've

22:57

been stuck in this elevator for a while

23:00

now. And I'm not really

23:03

sure what's going on.

23:05

Oh no! We forgot about Bob. He's

23:07

stuck in our thought experiment. Quick!

23:10

Let's imagine him somewhere nicer. A beach?

23:12

Too sunny for Bob. A theme park? He

23:14

gets sick on coasters. The movies?

23:17

Too exciting. The zoo? Too

23:20

exciting. A museum? Too

23:22

exciting. Bob likes to keep things real

23:24

low-key. I got it! A

23:26

museum before they hang up any

23:29

paintings.

23:30

Perfect. Hey

23:33

now. Is this a museum

23:36

before they hang up any paintings?

23:38

Don't mind if I do.

23:41

Well, well, well. Look at this

23:43

beautiful wall. It's so white,

23:46

so empty. You know, a blank

23:48

wall is the real art, I always

23:51

say. Oh, is that

23:53

an electrical outlet? I wonder if

23:55

it has three holes or just two.

23:58

I better go inspect.

23:59

Oh, three holes. This

24:02

is so exciting. I

24:04

love how the outlets look like little faces.

24:08

Hello there, outlet face.

24:11

Did you see these beautiful walls?

24:14

That's it for this episode of Brains

24:16

On. This episode was produced by Santa

24:18

Totten, Molly Bloom, Rosie DePont, Anna

24:21

Goldfield, Anna Waggle, Nico

24:23

Gonzalez Whistler, Arone Woldeslossi,

24:26

Molly Quinlan, Ruby Guthrie, and

24:28

Mark Sanchez. This episode was edited

24:30

by Shayla Farzon and sound designed by Rachel

24:32

Grease. Beth Perlman is our executive producer,

24:35

the executive in charge of APM Studios, our Chandra

24:37

Cavati, Alex Shaffert, and Joanne Griffith. Special

24:40

thanks to Chris Colvin, Melissa Winkler, and

24:42

Eric Ringham. And my class,

24:44

6C, at Wellesley

24:46

Public School. And my brother, Clyde,

24:48

Brains On, is a nonprofit public

24:51

radio program. There are a ton

24:53

of ways you can support the show. Head to brainson.org.

24:56

While you're there, you can send your fan art, your questions,

24:59

even your mystery sounds. And you can

25:01

also subscribe to our Smarty Pass. Add

25:03

free episodes and bonus

25:05

stuff just for you.

25:09

Okay, Bruce, are you ready to listen

25:11

to the mystery sound again?

25:12

Oh yeah. All right,

25:14

here it is. There

25:17

is a lot happening

25:21

there.

25:29

What did

25:32

you hear this time?

25:33

I

25:36

still, hmm, I actually

25:38

think it's the classic.

25:40

Raindrops falling into a bucket out

25:43

of an eaves trough. Classic.

25:47

Should we hear the answer? Yep. Also,

25:49

I'd like to say thanks to whoever

25:51

sent that mystery sound to Brains On. Well,

25:53

we're about to find out. You ready? Yeah.

25:56

Okay.

25:58

Hi, my name is My name is Charlie and

26:01

this is the sound of my mom flipping

26:03

over puzzle pieces.

26:06

Ohhhh.

26:06

Puzzle pieces. Yeah.

26:09

Well, thanks, Charlie.

26:11

Very good mystery sound, Charlie.

26:13

That was a tough one. Mm-hmm.

26:16

It makes sense though. I also thought it was drumsticks

26:18

falling out of the bag. Yes, I

26:20

could hear that. That would kind of make a clattering sound, you

26:23

know? Mm-hmm. Definitely. Mystery

26:25

sounds are tough.

26:40

Now it's time for the brains honor roll. These

26:42

are the kids who keep the show going with their questions, ideas,

26:45

mystery sounds, drawings, and high fives. Rayanche

26:48

from Illinois, Lydia from Indiana, Bodhi from Elgin,

26:50

Oregon, Santino from Albany, New York,

26:52

Owen from Yorkville, Illinois, Emerson from

26:54

Golido, California, Aziza from Chicago,

26:57

Jenna from Longview, Washington, Silas

26:59

from Durango, Colorado, Leisha from Salt Lake City,

27:01

Liam from Colorado Springs, Peyton and

27:03

Gage from Overland Park, Kansas, Pearl from Salem,

27:05

Oregon, Linnea from Singapore, Maddie from Olympia,

27:08

Washington, Isabel and Ian from St. Bezia La

27:10

Grande, Quebec, Julie, Emily, Liam,

27:12

and Carlos from South Carolina, Koa from Kailua,

27:14

Kona, Hawaii, Lucas from Burlington, Ontario,

27:17

Adam from Cambridge, Massachusetts, Noah and Elliott

27:19

from Wake Forest, North Carolina, Jude from

27:21

Hudsonville, Michigan, Miles from Lehigh, Utah,

27:23

Quinn from Hamilton, Ontario, Jackson from

27:25

Easton, Massachusetts, Molly from DeKalb, Illinois,

27:28

Maddie and Jillian from Baltimore, Theo from

27:30

Manassas, Virginia, Becca Rose from Beaufort,

27:32

South Carolina, Oliver and Porter from Tallow

27:34

Fofo, Guam, Jenna from Amman, Jordan,

27:37

Quinn and Emmet from Kentville, Nova Scotia, Sebastian

27:40

and Eliza from Toronto, Margarita and Alexis

27:42

from Elko, Newmarket, Minnesota, Arabella

27:44

from Arlington, Texas, Spencer from San Francisco,

27:46

Josh from Calgary, Emily from Houston, Texas,

27:49

his Greenwells class in Jacksonville, Florida, Alison,

27:51

Zoe Miranda, Levi, Charlie and Billy from

27:53

Dublin, Ireland, Grace, Lucy, Ellie and

27:55

Grant from Dublin, Ireland, Isaiah and Sterling

27:57

from Georgia, Saria from Brookfield, Illinois, Henry

28:00

and Francis from Cottage Grove, Minnesota. Emmett and

28:02

Mia from Portland, Oregon. Cashel from Stuart,

28:04

Florida. Amira from Memphis, Tennessee. Carson

28:06

from Aloha, Oregon. Davis, Oliver

28:09

and Archer from Honolulu. Max from Utah. Roshan

28:11

from Raleigh, North Carolina. Mariana from Papua

28:13

Moa, New Zealand. Aaron from Bethlehem, Pennsylvania.

28:16

Shreyas from Singapore. Belle from Winston, Salem,

28:18

North Carolina. Nola and Ainslie from

28:20

Brighton, Colorado. Will and Noah from Portland, Oregon.

28:22

Saria from Calgary. Sawyer from Victoria, Minnesota.

28:25

George from Chattahoochee Hills, Georgia. Rini from

28:27

Lakewood, Colorado. Solomon from Davidson, North Carolina.

28:30

Amelia from Tarrytown, New York. Finley from North

28:32

Oaks, Minnesota. Lola from San Jose, California.

28:35

Oz from Newburgh, New York. Asha from Sydney, Australia.

28:37

Max and Ezra from Toronto. Claudia from Shirley,

28:39

New York. And Loeweek from Vancouver. Pray

28:44

in the circle, I fight.

28:48

We'll be back next week with more answers to

28:50

your questions. Thanks

28:52

for listening.