Greetings, greetings, Bill Nye here.

Today we're gonna do some science support.

Our first question comes from Destiny Dolin.

No, serious question.

What makes people think global warming isn't a real thing?

Like, it's February and it's 70 degrees outside.

Upside down smiley emoji.

So I'm thinking now that it's cognitive dissonance.

This is a real effect where people

have a certain worldview, they're confronted with

evidence which conflicts with the worldview

so they have dissonance, conflict in their minds.

What's generally done, instead of changing your worldview

which you may have held your entire life,

you dismiss the evidence, and along with that you dismiss

the authorities that may have provided the evidence.

Bird TV asks, If we can clone extinct species, should we?

I think it'd be cool.

What we're all talking about is like a wooly mammoth.

Hi, Steve.

Hi, Bill!

That's my wooly mammoth impression.

This one would be named Steve.

Anyway, I think it'd be cool, but it's not up to me.

Carry on.

Do you know how long Earth has existed?

This is from Issa Nissan.

And I would say Yeah, 4.6 billion years.

Rocky Online, I have a doubt, related to evolution theory.

If we evolved from monkeys,

then why are there still monkeys?

(laughs) That's brilliant!

You're the first guy to ever wonder this.

We did not descend from monkeys.

Monkeys and we have a common ancestor,

so you may have seen this picture, this famous arrangement.

This isn't really accurate,

it wasn't just one to the other to the other.

As we say, the family tree of hominids like you and me

and even my old boss (laughs) is not just a straight line

of one organism leading to another,

it's a bush, as we say, so there's many, many branches

and you and I ended up on one of them.

So we did not descend from monkeys,

monkeys and us have a common ancestor and you can prove it.

Anthony Arjun, Ar-jen?

Arjun, asks, What makes a planet a planet?

You gotta have enough gravity to be a ball,

and right now you gotta have enough influence

to clear out your orbit from other stuff, other debris.

Stand With Rand writes, Can alternative energy

effectively replace fossil fuels?

Absolutely yes.

Burning coal is the worst thing we can be doing.

So I encourage you to check out thesolutionsproject.org.

They have done an analysis of not only the United States's

electricity needs, but 130 other countries around the world.

And we could power the whole place right now

if we just decided to do it, with wind, solar energy,

some tidal energy, some geothermal energy.

We could run the whole place.

It wouldn't shut down existing nuclear plants,

but it's really hard to build a new nuclear plant

because nobody wants them around.

Bruning Two asks, A double rainbow

I saw a couple months ago.

What causes a double rainbow

opposed to a normal rainbow?

Well, one could make an argument,

he's got pictures here, or she.

In a sense there's always a double rainbow,

it's just the second one is much fainter.

It's not as bright, so the background,

the sky has to be dark enough for you to see it, generally.

R Camp asks, Why is the sky blue?

Why can't it be green?

Careful what you wish for.

Air molecules are spaced in such a way that

when waves of light pass between them, they are scattered.

As we increase the greenhouse gasses

in the earth's atmosphere, people have speculated

that the scattering will change.

The molecules doing the scattering will be so abundant

that the sky will no longer be blue.

It's not good.

Carry on, R Camp.

Backseat Drawing, Magnets, how do they work?

They're magic.

No, what happens in certain materials,

the strongest one and the most common one,

the one we all know and love is iron,

and these are steel and steel is almost entirely iron,

just a little bit of carbon,

there's what they call a virtual current,

where the electrons are moving from atom to atom.

And this produces this magnetic field,

and this tendency is so strong

that magnets stay magnetic for centuries.

Mint Choc-Lit Chip asks, What is the 4th dimension?

Is it smell?

The fourth dimension is time.

This is not rocket surgery.

The fourth dimension is time.

X, Y, Z, time.

Lil' Poundcake asks Can artificial intelligence

take over the earth?

Yes.

Yes.

What do you think?

No, people make artificial intelligence.

Are we gonna make a machine that produces electricity

in a way that we can't control that takes over for us?

Really, who's gonna build that machine?

How's long do you genuinely believe

the human race has existed on Earth?

About a hundred thousand years.

Gerry Buck, What is dark matter?

It's not clear, but it has, apparently,

an influence like gravity, and there's more of it than

there is regular matter that you and I are familiar with.

Gerogeperson, People say that cell phoness,

I think it's might give off radiation to the brain.

Turns out people get brain tumors all the time.

People talk on cell phoness way, way more of the time.

They have done studies trying to connect

cell phoness and brain tumors, there is no connection.

Carry on.

Farah Damji, How safe is acupuncture?

I know people believe in acupuncture,

there's no value to it.

But if you think it works and

it makes you feel better, carry on.

Will horseradish and rib au jus

leak through you after you get acupuncture?

I don't know, run a test, try it.

BrieAnna Rae, They say avocados are 'good' fat, but

how much avocado can you eat before it becomes bad fat?

You can eat a million avocados.

What do you think?

For crying out loud, there's calories in avocados.

Just there's also some unsaturated fat.

Avocados are great, I recommend

an avocado with a poached egg.

That is, that's living.

Vates, I wonder what the world would be like

after a nuclear war?

It would suck, okay?

I was in class when Professor Carl Sagan

talked about this idea of nuclear winter,

where you'd set off so many nuclear weapons so rapidly

that all the debris thrown in the sky

would make the earth cold, and this was dismissed

for a while until Walter and Luis Alvarez found an

impact crater off Chicxulub, Mexico

that was almost certainly where this asteroid hit

that killed the ancient dinosaurs in the same way,

by throwing this cloud of debris.

The ejecta, the ejected material from that impact

was bigger around than the diameter of the earth.

Dr. Chand Zahid So what's concluded about GMOs?

Are they safe to eat or not?

Yes, GMOs are safe to eat!

We feed genetically modified food to rats, lab rats, mice

all the time, and they're fine.

The problem is that what genetically modified organisms

have enabled monocultures, these enormous fields

of the same type of plant, and that has

led to some environmental problems.

Callie, How do people actually believe the earth is flat?

I'm stumped Callie, I don't know how people believe that.

We have classroom globes, we have spacecraft

that take pictures, you can find documents from

medievals times where people knew the world was round.

Columbus, Christopher Columbus knew the world was round.

He just sold Queen Isabella on the idea

that he could get it done really fast,

sailing around the world.

Derrick, Why are people willing to pay more for

organic food when there's absolutely no evidence

that it is any better for you?

Uh, perception, it's marketing, man.

People want to feel that no pesticides were used

and they're thinking maybe globally.

It's not just a question of whether or not

it's good for you, it's a question of

whether or not it's good for the ecosystem,

and good for the agriculture, the sustainability

of our agricultural systems.

One of these is organic and

one of them is genetically modified.

Do you know which one?

Neither do I, but generally the bigger one.

No, no, you can't tell.

Carry on.

Final question, Hey Bill, are you free for dinner?

Uh, often.

Thanks for your question, carry on.

Thank you all for supporting science.

We went through your tweets and we had nothing but fun.

I'm Bill Nye, see you next time.