Fun with E mc2

1
Fun with E mc2

• Samir Dhurde
• IUCAA, Pune

2
E mc2 is everywhere!
3
Does this mean that

• Equations dont scare us?
• We can use science just like scientists?
• We dont 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?

4
What do you think of

• Energy (in joules)
• Mass (in kilograms) X
• The 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

Its our same old friend E mc2
? Using
5
So lets use it

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

6
E mc2 oki k!

• izu
• 1 fyV ik.krqu vkiYkyk fdrh mtkZ fuekZ.k djrk
  sby ?

7
Isnt that a strange question?

No its 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!
8
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 isnt it?) .

Thats a BIG lot
9
izdkkpk osx

• 300,000,000 m/s
• 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)
• (gs i fnlkyk vk.kh okijkykgh lksia vkgs) .

,olts kqU !
10
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 Joules
• That is it!
• Was that tough?
• You just fruitfully used Einsteins Equation!!!

11
oLrqeku

• 1 fyV ik.kps oLrqeku dk ?
• 1 kilogram!
• m 1
• So, E 1 (9 X 1016)
• 9 X 1016 Joules
• gtkya !
• dBhu gksra dk ?
• vkiu Einsteins Equation okijys !!!

12
What else can you find out about?

• Free your Mind!

What could all this energy be used to power?
13
What else can you find out about?

• Free your Mind!

k mtsZpk okij vkiYkyk dqBs djrk sbZy?
14
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)

15
Energy Power

• 1 Joule 1 kilogram yk 1 meter/second2 k
  Roj.kkus 1 meter ltdy.kl ykx.kkjh mtkZ.
• 1 Joule lrr 1 second okijYkl 1 Watt kDrhpk
  izksx gksrks.
• 1 litre ik.kPk mtZskjk 1 watt pk light bulb
  fdrh osG isV.kkj ?
• 9x1016 seconds, or 2.5x1013 hours
• or 3 billion years! (2/3 the age of the Earth)

16
A 100 Watt bulb

• would only stay lighted for 2.5 x 1011 hours!
• There are about 109 families on Earth
• So lets light 109 bulbs of 100 Watt power
• for 250 hours!
• You
• spend the same amount of energy
• as a 100 watt bulb !
• Hint One joule is equal to about four food
  calories

17
Bad use
200,000 people have been killed by just 2 atomic
bombs. One Hydrogen Bomb could kill 50 times as
many!
18
Best use

• All our energy comes from the Sun!
• The Sun has Emc2 as its source of energy.

19
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. 

20
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.

21
A look inside

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

22
More E mc2
The Sun emits 4 x 1026 joules per second

• 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 !

23
What Einstein didnt 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).

24
Keep trying Doc
25
Why havent 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!

26
Use what you have properly
Solar Lighting
Solar Heater
Solar Cookers
27
Science is not storytelling

• its also painstaking observations of Nature.
• Respect Nature
• Thank You