Fun with EMC2

Fun with E = mc2

Samir Dhurde

IUCAA, Pune

E = mc2 is everywhere!

Does this mean that… Equations don’t scare us?

We can use science just like scientists?

We don’t need to go to school !? We can get all Science off Discovery Channel? Everyone knows what Einstein knew?

OR Science is bad because people can make

bombs out of it?

What do you think of…Energy (in joules)

= Mass (in kilograms) XThe Speed of Light Squared(in meters squared per second

squared) ?

Complex Science?!?

But did you know these units? No…

Because you never used E = mc2 !!!for us…

Knowing = Memorising≠ Using

Its our same old friend E = mc2

So lets use it…

How much energy will one litre of water yield if it is converted entirely into Energy?

Isn’t that a strange question?

No it’s Not!

Matter and Energy are two forms of the same

thing!

Neither can be destroyed but, under

special circumstances, either can be turned

into the other

Lots of energy goes into making even a

small mass and it can also be got back in

some form.

E = mc2 tells you exactly how much

energy a given amount of mass

contains.

Use it Properly!

The speed of light… Light travels three hundred million meters in

a second i.e. 300,000,000 m/s A meter is as big as a ???

So (forgetting the units for now)

Energy = mass x (300,000,000)2

or E = m (90,000,000,000,000,000)

= m (9 x 1016)(this form is easier to use isn’t it?) .

That’s aBIGlot

Mass What is the mass of 1 litre of water?

A litre of water is defined to have a mass of one kilogram!

m = 1 So, E = 1 (9 X 1016)

= 9 X 1016 JoulesThat is it!

Was that tough?You just fruitfully used Einstein’s Equation!!!

What else can you find out about?

Free your Mind!

What could all this energy

be used to power?

Energy & Power A Joule is the effort required to push one

kilogram over a meter at an acceleration of one meter/second2.

A Joule expended continuously for one second is a Watt. A litre of water, converted to energy

could power a 1 watt light bulb for…

9x1016 seconds, or 2.5x1013 hours

or ~3 billion years! (2/3 the age of the Earth)

A 100 Watt bulb… would only stay lighted for 2.5 x 1011 hours!

There are about 109 families on Earth

So let’s light 109 bulbs of 100 Watt power

for 250 hours…!

Youspend the same amount of energy

as a 100 watt bulb ![Hint: One joule is equal to about four food calories]

Bad use

200,000 people have been killed by just 2 atomic bombs.

One Hydrogen Bomb could kill 50 times as many!

Best use…

All our energy comes from the Sun!

The Sun has E=mc2 as its source of energy.

Nuclear Fusion

When 4 hydrogen nuclei are fused together into 1 helium nucleus, energy is released in the form of Light photons and particles called neutrinos. 

But where does the mass come from?

Mass of 4 hydrogen nuclei is more than that of 1 helium nucleus

So after fusion a little bit of mass is left over. This mass deficit appears as the energy of light and neutrinos.

A look inside…

The fusion happens 700,000 km deep in the Sun’s core.It needs unbelievable temperatures of 15 million degrees.

More E = mc2

How much mass does it convert each second in order to shine?

If the Lifetime of the Sun

is 1010 years, how much mass would it need in that time?

Use m = E/c2 !

The Sun emits 4 x 1026 joules per second

What Einstein didn’t tell us…

How do you convert any mass to Energy?

Scientists are trying to make a sun on the Earth. A fusion reactor that uses hydrogen. Hydrogen is the simplest & lightest element. Hydrogen is abundantly found in water! Hydrogen fusion has been tried and tested in

Nature and on Earth (in H-Bombs).

Keep trying Doc…

Why haven’t we done it? Hydrogen is a diffuse gas and it is difficult

to get its nuclei close enough to fuse. They start colliding into each other only at a

temperature of 15 million degrees C. We need to keep it both hot & dense.

We would use up a lot of energy to start it and to keep it from exploding!

Use what you have properly…

Solar Cookers

Solar HeaterSolar Lighting

Science is not storytelling…

…its also painstaking observations of Nature.

“Respect Nature”

Thank You