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- 1. Fun with E = mc2 Samir Dhurde IUCAA, Pune
- 2. E = mc2 is everywhere!
- 3. 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?
- 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?!? Its our same old friend E = mc2 But did you know these units? No… Because you never used E = mc2 !!! for us… ≠ Using Knowing = Memorising
- 5. So lets use it… How much energy will one litre of water yield if it is converted entirely into Energy?
- 6. E = mc oki: ;k! 2iz’u% 1 fyV’ ik.;krqu vkiY;kyk fdrh mtkZ fuekZ.k djrk ;sby ?
- 7. Isn’t that a strange question? Lots No energy be Neither can goes of it’s Not! E = mc2 tells you destroyed but, under into making even a MattermassEnergy can and and it are exactly how much special circumstances, small twoenergyof the same formsgot given in a eitherbe be turned also can back amount of mass into thing! some form. the other 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 ??? That’s a So (forgetting the units for now) BIG lot 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?) .
- 9. izdk’kpk osx… 300,000,000 m/s So (forgetting the units for now) ,o<s ‘kqU; ! Energy = mass x (300,000,000)2 or E = m (90,000,000,000,000,000) = m (9 x 1016) (gs :i fnlk;yk vk.kh okijk;ykgh lksia vkgs) .
- 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 Einstein’s Equation!!!
- 11. oLrqeku1 fyV’ ik.;kps oLrqeku dk; ? 1 kilogram! m=1 So, E = 1 (9 X 1016) = 9 X 1016 Joules >kya ! dBhu gksra dk ? vkiu Einstein’s 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 vkiY;kyk 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 <dy.;kl ykx.kkjh mtkZ. lrr 1 second okijY;kl 1 Watt 1 Joule “kDrhpk iz;ksx gksrks. 1 litre ik.;kP;k mtZs}kjk 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 let’s 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 E=mc2 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 Sun’s core.It needs unbelievable temperatures of 15 million degrees.
- 22. More E = mc2The 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 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).
- 24. Keep trying Doc…
- 25. 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!
- 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

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