PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Black HolesBlack HolesEscape speed: The minimum speed required for a projectile to escape the gravitational effects of an object.For the earth, the escape speed from the surface is 11 km/sec.Some numbers:From the surface of the earth,M = 5.97 x 1024 KgR = 8.756 x 10-3 mvescape, earth = 3.0 x 108 m/secInteresting piece of information: IF the earth (magic?) could be collapsed to a radius of 0.008756 m (just about a centimeter)HmmmmmmmmmmEscape SpeedBlack HolesInteresting implication, once the details of General Relativity were understood:If the earth were to collapse to a radius of about 1 cm (a little less, actually), light would not be able to escape the gravitational pull of the earth.The trick is that the earth isn’t going to collapse to a radius of less than 1 cmHowever……..Black HolesIt is known from physical law that if the starting mass of a star is above 25 solar masses, the core that will remain after the life cycle has been completed will have a mass greater than 3 solar masses.There are no known mechanisms in physical law that can overcome gravity under these circumstances, and the core will continue to collapse FOREVERvescape = 2 G MR( )1/2Recall:Escape Speedvescape = c = 2 G MR( )1/2If you are looking for a circumstance for which the escape speed will equal the speed of light, then:Escape SpeedOr, rearranging,R = ( ) M or, R M2 Gc2Black HolesIF a core has a mass greater than 3 solar masses, and gravitation collapse cannot be stopped, then it is guaranteed that eventually the core will reach a radius with an escape speed greater than c.Once this happens, nothing, INCLUDING LIGHT, can escape the large gravitational pull of the core.Black HolesSchwarzschild Radius – the radius of a celestial object at which gravitational forces exceed the ability of matter and energy to escape. Event Horizon – A sphere with a radius equal to the Schwarzschild radius.Once the radius of the collapsing core goes below the Schwarzschild radius (ie, the physical object is contained within the event horizon), no form of information can escape.Block Hole – A object which has collapsed to a radius smaller that its Schwarzschild radius.Black HolesEvent HorizonBlack HolesAnd from outside, it look like…..Black HolesAre we all going to be eaten by black holes??Black HolesSunEarthBlack HolesSunEarthF = G ME M / r2 rBlack HolesSun shrunk to inside Event HorizonEarthBlack HolesEarthrSun shrunk to inside Event HorizonBlack HolesEarthF = G ME M / r2 rSun shrunk to inside Event HorizonBlack HolesEarthF = G ME M / r2 rSun shrunk to inside Event HorizonThe earth will experience no unusual effect if the sun were to suddenly shrink to inside of its event horizon
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