Learn how Hubble is measuring the expansion rate of the Universe in this new explainer from NASA's Goddard Space Flight Center.
Credit: NASA's Goddard Space Flight Center
Producer & Director: James Leigh
Editor: Lucy Lund
Director of Photography: James Ball
Additional Editing & Photography: Matthew Duncan
Executive Producers: James Leigh & Matthew Duncan
Production & Post: Origin Films
Video Credit:
Hubble Space Telescope Animation
Credit: M. Kornmesser (ESA/Hubble)
Dark Energy Expansion Graph
Credit: NASA's Goddard Space Flight Center
Dark Energy Expansion Animation
Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
Hubble Extreme Deep Field Fly Through
Credit: NASA, ESA, and F. Summers, L. Frattare, T. Davis, Z. Levay, and G. Bacon (Viz3D Team, STScI)
James Webb Space Telescope Animations
Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
Music Credit:
“Alpha and Omega” by Laurent Parisi [SACEM] via KTSA Publishing [SACEM] and Universal Production Music
“Cosmic Call” by Immersive Music (Via Shutterstock Music)
Credit: NASA's Goddard Space Flight Center
Producer & Director: James Leigh
Editor: Lucy Lund
Director of Photography: James Ball
Additional Editing & Photography: Matthew Duncan
Executive Producers: James Leigh & Matthew Duncan
Production & Post: Origin Films
Video Credit:
Hubble Space Telescope Animation
Credit: M. Kornmesser (ESA/Hubble)
Dark Energy Expansion Graph
Credit: NASA's Goddard Space Flight Center
Dark Energy Expansion Animation
Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
Hubble Extreme Deep Field Fly Through
Credit: NASA, ESA, and F. Summers, L. Frattare, T. Davis, Z. Levay, and G. Bacon (Viz3D Team, STScI)
James Webb Space Telescope Animations
Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
Music Credit:
“Alpha and Omega” by Laurent Parisi [SACEM] via KTSA Publishing [SACEM] and Universal Production Music
“Cosmic Call” by Immersive Music (Via Shutterstock Music)
Category
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TechTranscript
00:00 [ Music ]
00:07 >> When Hubble was launched, one of its main objectives was
00:10 to measure the Hubble constant,
00:11 the expansion rate of the universe.
00:13 >> Charlie?
00:13 >> [Inaudible] stand by for a go for release.
00:17 A minute late.
00:18 >> Okay, Charlie.
00:19 >> Flight PDRS.
00:22 >> Go ahead.
00:22 >> The telescope's released.
00:24 >> Okay, thank you.
00:26 >> Beginning in the mid-2000s, around 2005, I started a project
00:31 to use what are sort of the gold standard tools in astronomy
00:36 for measuring distances, which is
00:38 to use pulsating stars called Cepheid variables
00:41 and exploding stars called Type 1a Supernovae,
00:44 and of course the Hubble Space Telescope itself, and to try
00:47 to make more precise measurements
00:48 than had ever been made as a check on the universe.
00:53 New observations from the early history of the universe,
00:56 what's called the Cosmic Microwave Background,
00:58 were beginning to make very precise predictions
01:01 of how fast the universe ought to be expanding today,
01:04 and so we wanted to follow up on that
01:05 by making comparably precise measurements.
01:08 First, it was the WMAP,
01:10 Cosmic Microwave Background Satellite, that NASA flew
01:13 in the early 2000s, and then that gave way
01:15 to PLONK, the European Space Agency Satellite,
01:18 that was even more precise.
01:19 So by measuring the Cosmic Microwave Background
01:23 and then using a model that we call the Standard Model
01:26 of Cosmology to then extrapolate that to the present time,
01:30 they determined ultimately that the universe ought
01:32 to be expanding in funny units that we use 67.4 plus
01:37 or minus .5 kilometers per second per megaparsec,
01:41 which roughly means the universe will double
01:43 in about 10 billion years.
01:45 Using the Hubble Space Telescope and some of these tools,
01:52 the Cepheid variables and the Type 1a supernovae,
01:55 we determined the local expansion rate to be
01:58 about 73.0 plus or minus 1.0 kilometer per second per
02:04 megaparsec, which is the most precise local
02:06 or present measurement of the expansion rate.
02:09 But it differs from the expected value, expected that is,
02:14 by the state of the universe shortly after the Big Bang,
02:17 coupled with our understanding of the universe,
02:20 this cosmological model, and in fact,
02:22 those two now sit apart from each other
02:24 by about five times their mutual error bar,
02:26 which is a phenomenon we call now the Hubble Tension.
02:30 To give you an analogy, it would be like if you had a small child
02:34 and you measured their height when they were two years old,
02:38 that would be like the Cosmic Microwave Background
02:40 measurement, and then you used a model of how children grow
02:43 to predict how tall they ought to end up at adulthood,
02:47 and that would give you a height,
02:48 and then you would actually measure
02:49 when they grew up how tall they were.
02:51 And so that's the comparison we're making,
02:54 the present state of the measurement
02:55 versus what is a very precise measurement
02:58 in a younger universe, and then a model, like the growth curve
03:02 of a child, to predict how tall they will be.
03:05 Except unlike a child, we've seen many children grow.
03:08 We have a very good understanding
03:09 of that growth curve.
03:10 But we've only ever seen one universe, and it's full
03:12 of stuff whose nature we don't deeply understand.
03:15 And so it's not crazy to think
03:18 that we might be missing something in that understanding.
03:20 In order to predict and really extrapolate the state
03:27 of the universe from the beginning to the present day,
03:29 we have to understand components of the universe,
03:32 particularly two components whose nature is not well
03:34 understood, but make up 96% of the universe,
03:37 and that's dark matter and dark energy.
03:39 Dark energy makes up about 70%, and dark matter probably makes
03:43 up about 25 to 27%.
03:46 And we don't really understand
03:49 at a detailed level what these are exactly.
03:51 We don't understand their microphysics.
03:53 So in order to make these predictions,
03:55 we assume that they are their most vanilla
03:58 or plainest possible forms.
04:00 We see this tension then, and so one possibility,
04:04 not the only possibility, is that they are more complicated,
04:06 that there's a more complex story, or some other aspect even
04:11 that we've been missing about the universe.
04:12 The Hubble Space Telescope has more or less been working
04:18 on measuring the Hubble concept for its entire lifetime,
04:21 about 30 years.
04:22 So the original goal when it was launched was to measure it
04:25 to 10% uncertainty, and I think
04:27 that was successfully accomplished
04:29 in the early 2000s.
04:30 We're now on sort of what I would say is the second
04:33 generation of measurements of the Hubble concept
04:35 that are targeting closer to percent level precision,
04:38 and I think Hubble, especially with its new instruments,
04:42 has absolutely come through with the capabilities needed.
04:46 Hubble really has delivered the quality and caliber
04:49 of data that's necessary to make these measurements.
04:51 [ Music ]
04:59 [BLANK_AUDIO]