0:02 just over 100 years ago Einstein showed
0:04 how gravity could be imagined as a
0:07 distortion of space-time his equations
0:09 revealed that an object small enough and
0:11 massive enough could hide behind an
0:14 event horizon a point where gravity is
0:16 so strong that not even light could
0:18 escape astronomers now believe that
0:21 these objects known as black holes exist
0:24 they inhabit the Centers of almost all
0:26 galaxies where they can grow to be
0:28 millions or billions of times the mass
0:31 of our Sun despite this history and
0:33 growing astronomical evidence we have
0:36 never actually seen a black hole the
0:39 event horizon telescope or EHT is the
0:41 first experiment designed to capture a
0:44 black holes image in doing so the EHT
0:47 will test Feinstein's theory of gravity
0:49 at one of the most extreme places in the
0:52 universe the event horizon the best
0:54 chance we have of taking a picture of an
0:56 event horizon is the supermassive black
0:58 hole at the center of our own Milky Way
1:01 though it is 4 million times as massive
1:03 as our Sun it is so far away that
1:06 mapping its event horizon is equivalent
1:08 to standing in New York and counting the
1:10 individual dimples on a golf ball in Los
1:14 Angeles gas falling towards this black
1:15 hole heats up to billions of degrees
1:18 causing the event horizon to appear as a
1:20 silhouette whose size and shape are
1:23 predicted by Einstein's theory it is
1:25 best to observe this silhouette in light
1:27 with the wavelength of about one millimeter
1:27 millimeter
1:29 where the gas glows most brightly and
1:32 light can travel unimpeded from the
1:34 center of the galaxy to telescopes on
1:37 earth close to the black hole the light
1:39 waves appear circular like ripples in a
1:41 pond but by the time they reach Earth
1:45 they are essentially plane waves imaging
1:48 a black hole at this wavelength requires
1:51 a telescope as big as our planet the EHT
1:54 uses a global network of dishes to
1:57 simulate a telescope of this size each
1:59 dish collects and records radio waves
2:02 coming from near the black hole the data
2:04 are then combined to create the image of
2:06 the event horizon this will only work
2:09 however if the dishes are completely
2:12 synchronized to understand this let's
2:13 use the analogy of a
2:15 such as an optical telescopes used for stargazing
2:16 stargazing
2:19 imagine the EHT formed from all the
2:21 different array sites as one big
2:24 parabolic mirror the mirror is curved so
2:26 that when a line of waves comes into the
2:28 dish they bounce off at specific angles
2:31 and arrive at the focus at the same time
2:33 when the EHT sites are synchronized
2:36 their recordings can later be perfectly
2:38 aligned in the same way that the mirror
2:39 aligns the optical light
2:42 if the surface of the mirror is not
2:45 stable if it is vibrating for example
2:47 the reflected light rays will not
2:50 combine properly at the focus for the
2:53 EHT an unstable mirror surface is
2:57 analogous to an unstable recording to
3:00 ensure stability the EHT uses atomic
3:02 clocks that will lose only one second
3:06 every hundred million years the amount
3:08 of data recorded during observations is
3:10 so large that it could never be
3:12 transferred over the internet instead
3:15 the recordings are stored on hard disks
3:16 and shipped back to a central facility
3:19 for processing there a supercomputer
3:22 combines the data from all the sites
3:24 staggering them during playback to
3:25 account for the time difference between
3:27 waves getting to each telescope the
3:29 resulting data can then be used to make
3:32 images with extreme magnifying power as
3:35 more dishes join the HT and the more
3:37 widely spaced they are the sharper our
3:39 image of the event horizon will be in
3:42 April 2017 the HT coordinated
3:44 observations of the Milky Way's central
3:47 black hole using a global network of
3:49 telescopes an international team of
3:52 astronomers is analyzing the data eager
3:54 to bring a black hole into focus for the
3:57 first time the results could transform
4:00 our understanding of black holes gravity
4:03 and even the universe [Music]
