Fun with EMC2
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  • Show One Joule
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Transcript

  • 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. oLrqeku1 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