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Gravity! In black holes and our Solar System Dr. Abbie Stevens Event Horizon Telescope

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Gravity ● Gravity is a pulling force between two or more things with mass ● The more mass something has, the stronger the gravitational field it produces ● Two famous scientists who described gravity: Newton and Einstein ● Mass curves space; the more mass, the more space is curved, and thus the more gravitational pull it has

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What is a black hole?

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Myth or Fact? Credit: Peter & Trent Ninos

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Black holes have enormous mass ● Mass: 3 Suns to billions of Suns Credit: NASA Credit: NASA Credit: Creative Commons

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Black holes have a huge escape velocity ● Earth’s escape velocity: ~25,000 mph ● The Moon’s escape velocity: ~5,300 mph ● A black hole’s escape velocity: 670 billion mph

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What is a black hole? ● Powerful gravity ● Even light cannot escape Credit: NASA 8,000 miles 2,160 miles 239,000 miles

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Do you really know gravity? ● Space ● Mass ● Bending ● Newton ● Einstein

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Re-visiting: Myth or Fact? Credit: Peter & Trent Ninos

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Hunting for a black hole

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Watching a black hole eat Credit: NASA

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What if the black hole isn’t eating? Black hole as ☆

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Watching a black hole bend light

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Gravitational forces in the Solar System

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Credit: caltiva

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Relative distances in our Solar System 3 Mercury: 1.5 yds Sun: 0 yds Neptune: 120 yds Venus: 2.9 yds Earth: 4 yds Mars: 6.1 yds Jupiter: 20.8 yds Saturn: 38.1 yds Uranus: 76.8 yds 3

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● Big swirling gas cloud flattens under its own gravity ● Dust clumps into rocks, which clump into planetesimals, which attract more dust and rocks by their gravity, and become planets Real picture of a protoplanetary disk Credit: ALMA; C. Brogan; B. Saxon Protoplanetary nebula → protoplanetary disk

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Summary ●Mass bends space to form a gravitational field ●Black holes are ‘black’ because their escape velocity is faster than the speed of light ●Gravity was important in the formation of our Solar System within the protoplanetary disk Event Horizon Telescope: first-ever picture of a black hole!

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Fitting the Solar System in this room: distance ● Sun – Mercury: 35 million mi ● Sun – Venus: 67 million mi ● Sun – Earth: 93 million mi ● Sun – Mars: 142 million mi

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Fitting the Solar System in this room: distance ● Sun – Mercury: 35 million mi ● Sun – Venus: 67 million mi ● Sun – Earth: 93 million mi ● Sun – Mars: 142 million mi ● Sun – Jupiter: 484 million mi ● Sun – Saturn: 889 million mi ● Sun – Uranus: 1.79 billion mi ● Sun – Neptune: 2.8 billion mi ← total size of Solar System

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Fitting the Solar System in this room: size ● Sun: 864,000 mi ● Mercury: 3000 mi ● Venus: 7500 mi ● Earth: 7900 mi ● Mars: 4200 mi ● Jupiter: 89,000 mi ● Saturn: 75,000 mi ● Uranus: 32,000 mi ● Neptune: 31,000 mi ← total size for comparison Credit: Universe Today

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More resources https://www.nasa.gov/topics/solarsystem/index.html https://www.universetoday.com/ https://exploratorium.edu/ronh/weight/ CrashCourse Astronomy by PBS on YouTube (10-15 min episodes on gravity, black holes, the Solar System, etc.)