What's at the center of the Milky Way Galaxy and what would be different if Earth was positioned there?
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00:00 (music and explosion)
00:07 See that strip of stars
00:09 splashed across the night sky?
00:12 That's our home galaxy,
00:14 the Milky Way.
00:16 You can see it from Earth
00:17 because we live right on the outskirts,
00:19 far away from all the fun stuff
00:21 happening at its center.
00:23 What would it be like to reside
00:25 in its galactic downtown?
00:28 What would our night sky look like?
00:31 Would we get sucked into a black hole?
00:35 This is WHAT IF,
00:36 and here's what would happen
00:38 if the Earth was near the center
00:40 of the Milky Way.
00:41 (music and explosion)
00:43 The Milky Way is huge,
00:45 about 100,000 light-years across.
00:48 It has four large spiral arms
00:50 encircling its center.
00:52 That makes it a barred spiral galaxy,
00:55 just like most galaxies
00:57 in the observable Universe.
00:59 If the Earth packed up its belongings
01:01 and moved to the heart of the Milky Way,
01:04 things would be looking pretty bleak
01:05 for the survival of any kind of life
01:07 on the planet.
01:09 But not because of the Milky Way's
01:11 supermassive black hole.
01:13 (music and explosion)
01:16 The Earth is located in a quiet neighborhood
01:18 in one of the smallest spurs
01:19 of the Milky Way,
01:21 the Orion Arm.
01:23 We've got approximately 27,000 light-years
01:26 between us and the galactic center.
01:29 It's a comfortable spot to live in.
01:31 The temperatures on Earth
01:32 are just right to sustain life,
01:34 and there aren't too many space hazards
01:36 that could wipe out our existence.
01:38 (music and explosion)
01:42 Well, I didn't say it's completely safe,
01:44 did I?
01:46 Living anywhere near the center
01:47 of the Milky Way would be different.
01:50 It would depend on what part of that center
01:52 the Earth had the misfortune to occupy.
01:56 The closer you get to the heart of the galaxy,
01:58 the tighter the stars are packed together.
02:01 Because of this high star density,
02:03 the Earth would be blasted
02:04 with a lot more radiation
02:06 than what the Sun throws at you right now.
02:08 Under these circumstances,
02:10 the odds of life ever evolving
02:12 would be pretty small.
02:14 But if the Earth moved to the center,
02:16 together with all its inhabitants,
02:18 you'd find yourself very unlucky.
02:23 Earth's magnetosphere
02:24 wouldn't be able to protect you
02:25 from space radiation
02:26 blasting from all directions.
02:29 This could change the Earth's climate
02:31 and cause everything on the planet
02:32 to either mutate or die.
02:36 If you lived,
02:37 your biggest concern would be
02:38 a close encounter with a supernova.
02:41 A supernova occurs
02:42 when a massive star collapses,
02:44 releasing radio waves,
02:46 X-rays, cosmic rays,
02:47 and gamma rays into space.
02:51 For all we know,
02:52 one massive stellar body
02:54 could throw the Earth
02:55 out of the Sun's orbit.
02:56 Our planet would be surrounded
02:58 by foreign stars,
03:00 until one of them exploded in a supernova
03:02 and wiped us out for good.
03:04 But it would look spectacular from Earth,
03:06 if only for a brief moment.
03:09 There's another big hazard
03:11 that lies within the Milky Way's center,
03:13 a supermassive black hole
03:15 called Sagittarius A*.
03:18 If getting sucked into a black hole
03:20 isn't on your to-do list,
03:21 consider yourself lucky.
03:24 The Earth might stay far enough from it
03:26 that we wouldn't get engulfed
03:27 by this cosmic beast.
03:29 But we could get close enough
03:31 to get caught in the black hole's orbit.
03:34 At a distance of 20 billion km (1.2 billion mi)
03:37 from the black hole's event horizon,
03:39 the Earth could develop a speed
03:40 of 25 million km/h (1.2 billion mph).
03:44 That's over 230 times faster
03:46 than the speed our planet
03:47 is moving at right now.
03:50 So would that mean strong winds?
03:52 More natural disasters?
03:54 Would you end up flying off into space
03:56 and right into the black hole?
03:59 It sure wouldn't be good for you,
04:00 or anything else on the Earth's surface.
04:03 The Earth is perfectly designed
04:05 to be right where it is.
04:07 It can survive on the outskirts of the galaxy,
04:10 but you wouldn't want it to be anywhere else.
04:13 The most dangerous place
04:14 for a planet to be located
04:16 is anywhere near the center of a galaxy,
04:18 any galaxy.
04:20 If you just want a nice view,
04:22 your best bet might be to teleport the Earth
04:25 to the middle of a nebula instead.
04:28 But that's a story for another WHAT IF.
04:32 ♪ ♪