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)
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TechTranscript
00:00When Hubble was launched, one of its main objectives was to measure the Hubble constant,
00:12the expansion rate of the universe.
00:14Charlie.
00:15You have to stand about for a go for release.
00:18Minute late.
00:19Okay, Charlie.
00:21Flight PDRS.
00:23Go ahead.
00:24The telescope's released.
00:25Okay, thank you.
00:27Starting in the mid-2000s, around 2005, I started a project to use what are sort of the gold standard tools
00:36in astronomy for measuring distances, which is to use pulsating stars called Cepheid variables
00:42and exploding stars called Type Ia Superdovi and, of course, the Hubble Space Telescope itself
00:47and to try to make more precise measurements than had ever been made as a check on the universe.
00:53New observations from the early history of the universe, what's called the Cosmic Microwave Background,
00:59were beginning to make very precise predictions of how fast the universe ought to be expanding today,
01:04and so we wanted to follow up on that by making comparably precise measurements.
01:09First, it was the WMAP, Cosmic Microwave Background Satellite, that NASA flew in the early 2000s,
01:14and then that gave way to PLONK, the European Space Agency satellite, as even more precise.
01:20So by measuring the Cosmic Microwave Background and then using a model that we call the Standard Model of Cosmology,
01:27to then extrapolate that to the present time, they determined ultimately that the universe ought to be expanding
01:33in front of units that we use 67.4 plus or minus .5 kilometers per second per megaparsec,
01:42which roughly means the universe will double in about 10 billion years.
01:45Using the Hubble Space Telescope and some of these tools, the Cepheid variables and the type 1a supernovae,
01:55we determined the local expansion rate to be about 73.0 plus or minus 1.0 kilometer per second per megaparsec,
02:04which is the most precise local or present measurement of the expansion rate.
02:10But it differs from the expected value, expected that is, by the state of the universe shortly after the Big Bang,
02:17coupled with our understanding of the universe, this cosmological model.
02:22And in fact, those two now sit apart from each other by about five times their mutual error bar,
02:27which is a phenomenon we call now the Hubble Tension.
02:31To give you an analogy, it would be like if you had a small child and you measured their height when they were two years old,
02:38that would be like the cosmic microwave background measurement.
02:41And then you used a model of how children grow to predict how tall they ought to end up at adulthood,
02:47and that would give you a height, and then you would actually measure when they grew up how tall they were.
02:52And so that's the comparison we're making, the present state of the measurement
02:56versus what is a very precise measurement in a younger universe,
03:00and then a model like the growth curve of a child to predict how tall they will be.
03:05Except unlike a child, we've seen many children grow.
03:08We have a very good understanding of that growth curve.
03:10But we've only ever seen one universe, and it's full of stuff whose nature we don't deeply understand.
03:15And so it's not crazy to think that we might be missing something in that understanding.
03:21In order to predict and really extrapolate the state of the universe from the beginning to the present day,
03:29we have to understand components of the universe, particularly two components whose nature is not well understood,
03:35but make up 96% of the universe, and that's dark matter and dark energy.
03:40Dark energy makes up about 70%, and dark matter probably makes up about 25% to 27%.
03:47And we don't really understand at a detailed level what these are exactly.
03:52We don't understand they're microphysics.
03:54So in order to make these predictions, we assume that they are their most vanilla or plainest possible forms.
04:01We see this tension then, and so one possibility, not the only possibility, is that they are more complicated,
04:07that there's a more complex story, or some other aspect even that we've been missing about the universe.
04:13The Hubble Space Telescope has more or less been working on measuring the Hubble concept for its entire lifetime, about 30 years.
04:22So the original goal when it was launched was to measure it to 10% uncertainty,
04:27and I think that was successfully accomplished in the early 2000s.
04:31We're now on sort of what I would say is the second generation of measurements of the Hubble concept
04:35that are targeting closer to percent level precision, and I think Hubble, especially with its new instruments,
04:42has absolutely come through with the capabilities needed.
04:46Hubble really has delivered the quality and caliber of data that's necessary to make these measurements.