WEBVTT FILE

1
00:00:00.000 --> 00:00:07.472
"Hubble Science"

2
00:00:07.472 --> 00:00:14.480
"Gravitational Lensing: Nature's Boost"

3
00:00:14.480 --> 00:00:20.560
As Hubble looks out into these fields of 
galaxies, we sometimes see clusters of  

4
00:00:20.560 --> 00:00:26.400
galaxies; these are galaxies that are held 
nearby each other by their mutual gravity.  

5
00:00:26.400 --> 00:00:35.280
These clusters are massive conglomerations. 
There's so much mass that they have an actual  

6
00:00:35.280 --> 00:00:43.840
observable impact on space-time itself. Einstein 
predicted that mass distorts space, but we didn't  

7
00:00:43.840 --> 00:00:49.120
realize we could actually see the effects of 
that. But with Hubble, we have been able to see  

8
00:00:49.120 --> 00:00:54.720
distortions in space around clusters of 
galaxies. The way we see that is when light  

9
00:00:54.720 --> 00:01:00.880
from a background galaxy travels through that 
cluster of galaxies or around it, due to this  

10
00:01:00.880 --> 00:01:07.760
gravitational lensing effect. The lensing also 
magnifies that background galaxy. So if we look  

11
00:01:07.760 --> 00:01:13.280
in some of these distorted arcs, we can see more 
detail than we would ever have been able to see  

12
00:01:13.280 --> 00:01:20.320
without gravitational lensing, nature's boost. So 
Hubble has been used in an unexpected way for us,  

13
00:01:20.320 --> 00:01:26.400
to look at nature's magnifying glasses, these 
gravitational lenses, and using those to tell  

14
00:01:26.400 --> 00:01:31.600
us about much more distant galaxies in detail 
we could never have seen without the lensing,  

15
00:01:31.600 --> 00:01:35.760
and also to tell us how dark matter 
is distributed in those clusters;  

16
00:01:35.760 --> 00:01:41.600
because it turns out that most of the mass that's 
distorting space and these clusters of galaxies  

17
00:01:41.600 --> 00:01:46.960
is made of this unseen dark matter, not the 
visible stars in the galaxies, and we can't  

18
00:01:46.960 --> 00:01:51.360
see the dark matter. But by seeing how this 
background light is distorted, we can kind of  

19
00:01:51.360 --> 00:01:57.760
map out where that dark matter is through this 
effect we call gravitational lensing. So we're  

20
00:01:57.760 --> 00:02:02.560
learning a lot about dark matter, this mystery 
of matter we don't really know what it is, but  

21
00:02:02.560 --> 00:02:07.840
we know where it is in these clusters because of 
this innovative use of the Hubble Space Telescope.

22
00:02:07.840 --> 00:02:29.274
[ MUSIC ]