Sagittarius A* Is Far More Dangerous Than You Think — Transcript

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1. 0:00The stars are too close. That is your
2. 0:02first thought when the engines go quiet.
3. 0:04Through the front window, the sky is not
4. 0:06black. It is crowded. Stars everywhere.
5. 0:09Big ones, bright ones, white, yellow,
6. 0:12orange.
7. 0:14They are packed so tightly they look
8. 0:16like spilled sugar. There is no night
9. 0:18here. There is barely any dark. You are
10. 0:21at the center of the Milky Way, about
11. 0:2326,000 light-years from home. How you
12. 0:26got here is a different problem.
13. 0:28Today, you only have one job. You are
14. 0:30going to try to land on Sagittarius A*
15. 0:33the giant black hole at the heart of our
16. 0:35galaxy. It has about 4 million times the
17. 0:38mass of the Sun. And that brings you to
18. 0:40the first problem with your mission.
19. 0:42A black hole has no ground. No rocks, no
20. 0:45dust, no surface at all. You are trying
21. 0:48to land on something that does not have
22. 0:49a floor. Mission control knew this. They
23. 0:52sent you anyway. That tells you
24. 0:54something about mission control.
25. 0:56From Earth, nobody has ever seen this
26. 0:58view with their own eyes. Huge clouds of
27. 1:01dust sit between Earth and the galactic
28. 1:03center. They block almost all of its
29. 1:05visible light. You are the first one to
30. 1:08just look out of the window.
31. 1:10Back home, the nearest star is more than
32. 1:12four light-years away. Here, neighboring
33. 1:14stars can be hundreds of times closer
34. 1:16than that. You start searching for the
35. 1:18black hole. You check every direction.
36. 1:20Nothing.
37. 1:21Between them, long glowing streams of
38. 1:23gas curl slowly inward. They look like
39. 1:26the arms of a lazy whirlpool. But at the
40. 1:28center of that whirlpool, you see
41. 1:30nothing at all. That makes sense. A
42. 1:33black hole does not shine.
43. 1:35It swallows light. So, you cannot look
44. 1:38for it directly. You have to look for
45. 1:40what it does to everything else.
46. 1:42Then you notice one star moving faster
47. 1:44than the others. Much faster.
48. 1:47It is swinging around an empty patch of
49. 1:49sky. Like a stone on a string. Except
50. 1:52there is no string. And there is nothing
51. 1:54in the middle. That star is called S2.
52. 1:57At its closest pass, it moves over 7,000
53. 2:00km per second.
54. 2:02That is fast enough to cross the Earth
55. 2:04in under 2 seconds.
56. 2:06And it repeats this loop roughly every
57. 2:0716 years.
58. 2:09Something invisible is pulling it
59. 2:10around. Something incredibly heavy.
60. 2:13Packed into a tiny space.
61. 2:15Back on Earth, astronomers tracked stars
62. 2:18like this for decades. That is how they
63. 2:20knew this black hole existed. It is also
64. 2:23how they knew where to send you. S2 even
65. 2:25carries a message about what is coming.
66. 2:28As its light climbs away from the black
67. 2:29hole, it gets stretched. The light
68. 2:32shifts slightly toward red. Gravity is
69. 2:34not just pulling on the star. It is
70. 2:36pulling on its light. You make a mental
71. 2:38note. That seems important.
72. 2:41You point the capsule at the empty patch
73. 2:43and you go.
74. 2:44As you get closer, the empty patch is
75. 2:46not completely empty.
76. 2:48There is a faint glow around it.
77. 2:50Thin, hot gas swirls inward in a slow
78. 2:53spiral.
79. 2:54Most famous black holes are messy
80. 2:56eaters.
81. 2:57This one barely eats.
82. 2:59Sagittarius A* is one of the dimmest
83. 3:02giant black holes we know.
84. 3:04Most of the time, it is starving.
85. 3:06That sounds reassuring. It is not.
86. 3:09Because it has not always been this
87. 3:11calm.
88. 3:12Clouds of gas near the center still glow
89. 3:14with old reflected X-ray light. That
90. 3:16echo suggests it flared much brighter a
91. 3:18few centuries ago.
92. 3:20So, you have arrived during a quiet
93. 3:21period. You decide not to mention this
94. 3:24to the black hole.
95. 3:25Because even quiet, the gas it does eat
96. 3:28is ferociously hot. We are talking
97. 3:30billions of degrees. But it glows with
98. 3:33radio waves and it can blast out X-rays.
99. 3:36Your radiation alarm starts beeping.
100. 3:38Quietly at first.
101. 3:40You raise the shielding. You remind
102. 3:42yourself this is the calm version.
103. 3:44Then the black hole flares.
104. 3:46Without warning, the glow brightens. A
105. 3:49burst of X-rays ripples out from the
106. 3:50center.
107. 3:51Flares like this happen roughly once a
108. 3:53day.
109. 3:55Nobody fully knows what triggers them.
110. 3:57Your alarm stops beeping politely. It
111. 3:59starts screaming. Your shielding holds,
112. 4:02barely.
113. 4:03You make a note. Mission Control's
114. 4:05definition of quiet needs work.
115. 4:07The flare fades.
116. 4:09The glow settles down.
117. 4:10And now you are close enough to see the
118. 4:12dark spot itself. A round black shadow
119. 4:15surrounded by a ring of glowing gas.
120. 4:17Astronomers revealed a picture of this
121. 4:19ring in 2022. It was blurry, orange,
122. 4:23taken from 26,000 light years away.
123. 4:26Now you are looking at the real thing,
124. 4:27up close.
125. 4:29Somewhere inside that black shadow is
126. 4:30the event horizon. The edge of no
127. 4:32return.
128. 4:33Anything that crosses it, even light,
129. 4:35can never come back out.
130. 4:37The event horizon is roughly 18 times
131. 4:40wider than the sun. The glowing ring
132. 4:42around it would fit inside the orbit of
133. 4:44Mercury. That is not a planet. That is
134. 4:46not a star. That is a hole in the rules.
135. 4:50Then the sky starts to bend.
136. 4:52Stars behind the black hole do not
137. 4:53disappear.
138. 4:54They smear.
139. 4:56Their light curves around the edge of
140. 4:57the shadow.
141. 4:58One star turns into two copies. Then
142. 5:01into a thin glowing arc.
143. 5:03You can see stars that should be hidden
144. 5:04behind the black hole. Gravity here is
145. 5:07bending light like a giant lens. The
146. 5:09whole sky looks like it is being pulled
147. 5:11into a funnel.
148. 5:12Your eyes say everything is moving. Your
149. 5:14instruments say it is just the light.
150. 5:16You trust the instruments, mostly.
151. 5:19If you're enjoying this video, please
152. 5:21hit the subscribe button. It genuinely
153. 5:23helps keep the channel alive. So far you
154. 5:26have been falling freely. Now you try
155. 5:28the sensible thing. You decide to orbit
156. 5:30first. Circle the target. Find a good
157. 5:32spot to land.
158. 5:34At first, this works.
159. 5:36At about three times the radius of the
160. 5:37event horizon, something strange
161. 5:39happens.
162. 5:40Your orbit stops being stable.
163. 5:42The tiniest nudge, and you start sliding
164. 5:44inward.
165. 5:46Closer than this, there are no safe
166. 5:47circles left. There is no parking spot.
167. 5:50You can either fall in or fire your
168. 5:52engines very, very hard. You keep going.
169. 5:55Now you reach a place where gravity can
170. 5:57bend light into a circle.
171. 5:59Light can actually orbit the black hole
172. 6:01here.
173. 6:02Light leaving the back of your capsule
174. 6:04can travel all the way around and come
175. 6:06back to you from the front.
176. 6:08In principle, you could look ahead and
177. 6:10see your own ship's back.
178. 6:13The universe has turned into a hall of
179. 6:14mirrors
180. 6:15with you as the only exhibit. So you try
181. 6:18plan B. If you cannot orbit, maybe you
182. 6:21can hover. You point the engines down.
183. 6:23You fire. And you discover what hovering
184. 6:25here actually costs.
185. 6:27To hold still this close, your engines
186. 6:30must push incredibly hard.
187. 6:32We are talking hundreds of thousands of
188. 6:33times Earth's gravity.
189. 6:35At that force, you would not be sitting
190. 6:37in your seat.
191. 6:39You would become part of your seat. You
192. 6:40turn the engines off
193. 6:42and you let yourself fall.
194. 6:44Before you go further, you check on your
195. 6:46backup plan.
196. 6:47Far behind you, you left a small
197. 6:49observer probe. It is parked a safe
198. 6:51distance away.
199. 6:52Its only job is to watch you.
200. 6:55Your capsule sends it a blinking signal,
201. 6:57one flash every second. At first, the
202. 6:59probe receives one flash every second.
203. 7:02Then something strange happens. The
204. 7:04flashes start arriving further apart. 1
205. 7:07second, then two, then 10.
206. 7:11From the probe's point of view, your
207. 7:12clock is slowing down. Your capsule is
208. 7:15changing color, too. Its light shifts
209. 7:17toward red, then deeper red, then into
210. 7:20colors no human eye can see.
211. 7:22To the probe, you are slowing down,
212. 7:25fading,
213. 7:26getting dimmer.
214. 7:27But inside the capsule, nothing feels
215. 7:29different. Your watch ticks normally.
216. 7:32Your heart beats normally.
217. 7:34Time is not broken. It is just running
218. 7:37differently for the two of you.
219. 7:38By now, you are falling incredibly fast.
220. 7:41The black shadow fills most of your
221. 7:43window.
222. 7:44The rest of the universe is squeezed
223. 7:46into a bright ring around it, and then
224. 7:48you reach the event horizon. You brace
225. 7:50for impact. Nothing happens. No wall.
226. 7:54No flash, no bump, you just pass
227. 7:56through. You might expect the edge of a
228. 7:58black hole to tear you apart. But for a
229. 8:01black hole this big, the event horizon
230. 8:03is surprisingly gentle.
231. 8:05Gravity pulls on your feet a little
232. 8:06harder than on your head.
233. 8:08But near the horizon of this giant, that
234. 8:10difference is tiny. Far too small to
235. 8:12feel. Smaller black holes are the
236. 8:14dangerous ones at the edge. A small one
237. 8:17would stretch you apart before you
238. 8:18reached its horizon. This giant lets you
239. 8:20in politely.
240. 8:22It is the most polite trap in the
241. 8:23universe. Because something has changed.
242. 8:26You just cannot see it yet. You look
243. 8:28back. The stars are still there. Light
244. 8:31from outside keeps pouring in behind
245. 8:32you.
246. 8:33But nothing you send can get out. Your
247. 8:36blinking signals no longer reach the
248. 8:38probe. So you try the last escape plan
249. 8:40you have. You turn the capsule around.
250. 8:43Full thrust, away from the center.
251. 8:46It does not help.
252. 8:47Inside the event horizon, outward is no
253. 8:49longer a direction you can go. Space and
254. 8:52time are so twisted here. The center is
255. 8:54not just ahead of you, it is your
256. 8:56future. Every path you could take leads
257. 8:59there.
258. 9:00The same way every day, no matter what
259. 9:02you do, leads to tomorrow.
260. 9:04And here is the cruel twist.
261. 9:06Firing your engines does not buy you
262. 9:08time. It makes you reach the center
263. 9:10sooner.
264. 9:11The way to last longest in here is to do
265. 9:13nothing at all.
266. 9:15Just fall.
267. 9:16For a black hole this size, that means
268. 9:18roughly a minute, probably less.
269. 9:20The best survival strategy is to relax,
270. 9:23which is not something your body is
271. 9:24currently interested in.
272. 9:25The seconds tick by.
273. 9:27Then you start to feel it. Your feet are
274. 9:30being pulled slightly harder than your
275. 9:31head.
276. 9:32Then harder, then much harder. Your body
277. 9:35is being stretched along its length, and
278. 9:37squeezed in from the sides.
279. 9:40Physicists have a word for this,
280. 9:41spaghettification. It is a silly word
281. 9:44for something deeply unpleasant. In a
282. 9:46giant like this, it only happens at the
283. 9:48very end. In the final fraction of a
284. 9:50second. What happens after that, nobody
285. 9:53knows.
286. 9:54At the very center, our best theory of
287. 9:56gravity breaks down. It predicts a point
288. 9:59where density becomes infinite. Most
289. 10:01physicists think that means the theory
290. 10:03is incomplete there. Not that infinity
291. 10:05is actually real.
292. 10:07Your trip ends at the one place where
293. 10:09physics runs out of answers. Now, back
294. 10:12to the probe. It is still parked far
295. 10:14away, still watching. And from its point
296. 10:17of view, you never arrive. It sees your
297. 10:20capsule creep closer to the horizon.
298. 10:23Slower and slower. Redder and dimmer.
299. 10:27Your last flashes stretch out until they
300. 10:29fade into nothing.
301. 10:30To the rest of the universe, you never
302. 10:32quite fall in. You just fade away at the
303. 10:35edge.
304. 10:36So, did you land on Sagittarius A*? Kind
305. 10:39of. There was no ground to touch. No
306. 10:42surface to plant a flag on, but you did
307. 10:44reach it, and it kept you. Your mass now
308. 10:47belongs to the black hole.
309. 10:494 million suns, plus one astronaut.
310. 10:52Slightly heavier now. Nobody will ever
311. 10:54be able to measure the difference.
312. 10:5526,000 light years of travel. And your
313. 10:58biggest impact on the galaxy is a
314. 10:59rounding error.