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Life in Our Universe

Peer into the exciting new field of astrobiology and learn what science knows about one of the most fundamental questions of all time: Is there life elsewhere in the universe?
Life in Our Universe is rated 4.2 out of 5 by 59.
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Rated 5 out of 5 by from Are We Alone? Some Fascinating Lectures (While referring to much greater heat and luminosity from the sun in 1 B years): “and that will move the Earth out of the habitable zone…and that would be a disaster” dryly and matter-of-factly notes Professor Close. OK, Dr. Close is not a dynamic speaker, he speaks in a near monotone and takes long pauses, but he has assembled very interesting content for this course and made it quite accessible to us non-scientists. If we were to view this course as astrobiology, it’s decidedly more astronomy than biology. We get some cosmology, some terrestrial biology, prospects for life elsewhere in our solar system, the discovery of extra-solar planets, and finally the prospects for humans to perpetuate their existence elsewhere in the universe. I particularly found insightful his use of solar power and the inverse square law (the only math used) to mark the habitable zone (where water is liquid) in our solar system which is between 0.8 and 1.1 AUs (1 AU = distance from Sun to Earth). This would appear to eliminate Venus and Mars from the habitable zone. We also get some fascinating facts about our solar system. For example, Venus with an atmosphere 100 times more dense than Earth’s has 200 mph winds that circle the planet every 3-4 days. Imagine the force of that wind! The tidal effects of Jupiter’s massive gravity on its innermost moons, while providing an energy source to potential life on Europa, raises 3,000-foot tides on the rocky (!) moon Io, with such friction literally melting Io. (The course pre-dated NASA’s funding of the Europa Clipper Mission whose launch is scheduled for late 2024 and is projected to enter Jupiter’s orbit in 2030.) Professor Close, depending on your point of view, is either scientifically realistic or scientifically unimaginative about non-carbon forms of life and interstellar space travel. We hear the usual fare that carbon’s chemical virtuosity allow it to bond with so many other elements and that water is the ideal liquid solvent in which biochemical reactions can take place. It seems that life on gas giants is eliminated without discussion because there’s no solid surface. It’s been said of the states of nature that solids don’t allow enough molecular movement and gases don’t allow enough molecular contact, so liquids are the happy medium for biochemical reactions. I wonder? Maybe I’ve been overly affected by Sir Fred Hoyle’s 1957 classic “The Black Cloud” where a living, intelligent “cloud” propels itself by manipulating magnetic fields and thinks with electrically charged dust particles. Yes, I know it’s science fiction but Hoyle was a great scientist. Of course, how would you have semi-permeable membranes in a gaseous creature? I guess that’s my one little critique of the lectures, not the enough imaginative astrobiology and too many critiques of science fiction writers…although his rebuke of UFO fans was well justified. I believe implicit in his lectures is that microbial life may indeed pervade the universe (look at Earth’s extremophiles) but that intelligent life may be rare. As Enrico Fermi said: “Where are they.” There’s a great quote during the latter part of the course where Professor Close quotes Arthur C. Clark: “Two possibilities exist: either we are alone in the universe or we are not. Both are equally terrifying.”
Date published: 2024-02-24
Rated 5 out of 5 by from Good course! It is a fairly detailed astrobiology course. I do understand that it is academic in nature, so it is slow-paced and felt longer. I think there are so many documentary films and series in the same subject matter in recent years, making the course a bit slow for sure. But for an academic learner this course is well equiped with information.
Date published: 2023-09-02
Rated 2 out of 5 by from Missed opportunity I was disappointed in the course. The instructor is an outstanding scientist (an innovator in adaptive optics) but a plodding lecturer (no Carl Sagan). Visual production is primitive: in our CGI era there is no excuse for using 1950s plastic models of the solar system. Editing is sloppy, eg. he held up interesting meteorites but showed no close-ups. Content is high school level. Sound-effects were gratuitous: there is no good reason to add a distracting whoosh, chirp or ping every time a caption is put up on the screen (very annoying). On the positive, the landing video of the Titan probe (Lecture 14) was pretty cool!
Date published: 2023-07-23
Rated 5 out of 5 by from Good Presentation Found the course informative and easy to follow. Especially informative regarding our solar system, especially its early development and survival. Appreciated the relaxed conversational lecture style of the presenter versus a stilted prepacked presentation. The presenter didn't appear to be just reading off a teleprompter which is so often the case with recent Great Courses.
Date published: 2022-09-28
Rated 4 out of 5 by from Course in need of updating While overall the course is interesting it is badly out of date in several keys areas. As a recently retired astro physicist who currently lecturers on the search for exoplanets I was hoping for more current information. The search for exoplanets has had an amazing number of discoveries in the 10 years since this course was published. His discussion of the UFO phenomena is just classic dogma from main stream scientists which of course we now see has taken a 180 degree turn in the last year. I also don’t think the course spends enough time actually discussing the possibility non carbon based and/or none water based life which seem to be important potential life vectors based on current exo planet fundings. The field of astro biology is such a new discipline and encompasses so many other fields that an updated version of this course might be better off as an interdisciplinary collaboration with several lecturers rather than from just one astronomer who may not have sufficient expertise in all the revelant areas ( terrestrial biology, chemistry, biochemistry), astronomy, astro biology, rocket propulsion, spacecraft design, etc)
Date published: 2022-07-11
Rated 5 out of 5 by from Are We Alone in the Universe? The professor explained everything very clearly, providing excellent background material and current knowledge and research about the universe and prospects for discovering intelligent life.
Date published: 2022-07-05
Rated 5 out of 5 by from The best GC course yet I'm just up to lecture seven and so enjoying this course. Not having a full scientific background I sometimes have to rewind and listen again. But that's how learning should be - stretching you and fascinating you. I keep cornering family and friends to explain how it became possible for life to start on our planet.
Date published: 2022-06-30
Rated 4 out of 5 by from fascinating, but might use an update Extremely interesting topic. It seems the studies quoted end in the early 20-teens so unclear if any newer info. Could use subtitles
Date published: 2022-06-27
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Are we alone in the universe? Or does the cosmos pulse with diverse life forms? Life in Our Universe reveals the cutting-edge research leading scientists to believe that life is not exclusively the domain of Earth. Taught by Dr. Laird Close, an award-winning Professor of Astronomy and Astrophysics at The University of Arizona, these 24 stunningly visual lectures offer an unparalleled look at the most intriguing discoveries coming from the new field of astrobiology, as well as the mysteries that remain. You'll examine the remarkable coincidences that created our planet and sustained its habitability for 3.5 billion years. And you'll join the hunt for microbial life elsewhere in our solar system and Earth-like planets in alien solar systems-one of astronomy's "holy grails."


Laird Close

We are wonderers and explorers by nature-and we are just starting to set our sights on the stars, setting the stage for mankind's biggest adventure yet!


The University of Arizona

Dr. Laird Close is Professor of Astronomy and Astrophysics at The University of Arizona. Awarded a Canadian (study abroad) Natural Sciences and Engineering Research Council scholarship while attending The University of British Columbia, he then earned his Ph.D. in Adaptive Optics from the renowned University of Arizona Astronomy Department where he now teaches. Professor Close has been highlighted as an outstanding professor and mentor by his university, and in 2004, he was honored with a prestigious National Science Foundation CAREER Award, which is awarded to the top few percent of young science professors in America. He has also won major awards from the NSF's Major Research Instrumentation, Advanced Technologies, and Instrumentations program, and its Astronomy and Astrophysics program. Dr. Close has additionally won support from numerous NASA Origins of Solar Systems grants and is a member of NASA's astrobiology institute. While a researcher at the University of Hawaii, he discovered the first moon around an asteroid with a full orbit. Serving as Deputy Director for Adaptive Optics at the European Southern Observatory in 1998, he was the first instrument scientist for the most successful adaptive optics camera in the Southern Hemisphere. As a leader in brown dwarf and extrasolar planet high-contrast imaging astrophysics, he has invented and helped develop several cameras for the world's largest telescopes. Professor Close is the principal scientist of the 6.5m Magellan Adaptive Optics extrasolar planet imager, located in the high Atacama Desert of Chile.

By This Professor

Life in Our Universe
Life in Our Universe


Is There Life Elsewhere in Our Universe?

01: Is There Life Elsewhere in Our Universe?

Is there life in our universe? As you get an overview of the course-including the five major questions it will endeavor to answer-consider the possibility that life exists in some form in the cosmos. Learn how exponential growth in technological developments is enabling breakthroughs that were recently impossible.

30 min
Bang! A Universe Built for Life

02: Bang! A Universe Built for Life

How did we go from a dead universe to a universe full of life? Begin to answer this question by evaluating the scientific evidence supporting the big bang theory of the universe's creation, and learning the role stars play in creating carbon and the key elements needed for life.

29 min
A Star Is Born-Forming the Solar System

03: A Star Is Born-Forming the Solar System

How do you make a planet? Look at what is currently known about the process by which our solar system's planets formed from billions of small planetesimals, as well as how this process left the universe teaming with asteroids and comets that play an important role in life on Earth.

30 min
The Early Earth and Its Moon

04: The Early Earth and Its Moon

Follow a series of mishaps and cataclysmic events that set the stage for early Earth to finally flourish with life after 650 million years. Learn how a hot core, a large moon, and other properties on Earth helped lead to an active biosphere.

31 min
Impacts-Bringers of Death ... or Life?

05: Impacts-Bringers of Death ... or Life?

Delve into the Late Heavy Bombardment period that kept Earth stuck in a lifeless state for 650 million years, then watch an animation demonstrating the K-T impact event that wiped out the dinosaurs. Consider whether it's possible to protect ourselves from asteroids hurtling toward Earth-and why Hollywood gets it all wrong.

29 min
Evidence of the First Life on Earth

06: Evidence of the First Life on Earth

How has the Earth managed to stay within a moderate range of temperatures for billions of years, despite the atmosphere's wild fluctuations in oxygen? Study how convection, greenhouse gases, and the carbon rock cycle contribute to a powerful system of checks and balances that keep Earth's climate consistent with supporting life. Also, meet some of Earth's earliest life.

31 min
Common Themes for All Life on Earth

07: Common Themes for All Life on Earth

Now that you have covered the key elements necessary for life to exist, take a closer look at the things all life on Earth shares. Learn why the Biosphere 2 experiment in the 1990s failed, examine the behavior of microbes-the most important constituents of our biosphere-and trace life back to your universal ancestor.

30 min
Origin of Terrestrial Life

08: Origin of Terrestrial Life

For something to be "living," it generally must use energy to drive chemical reactions, be capable of reproduction, and undergo some degree of evolution. Sort through science's best educated guesses for how and why life sprang from nonliving matter, including lessons from the groundbreaking Miller-Urey experiment. Watch an animation of protocells growing and splitting to replicate geneti...

30 min
Astrobiology-Life beyond Earth

09: Astrobiology-Life beyond Earth

Why is liquid water so important? Why do icebergs float? After quickly reviewing what you have learned about the requirements for terrestrial life, take a closer look at the "liquid water carbon chemistry juggernaut," which allows organic life to thrive on Earth. Consider whether other liquids could operate as solvents for life.

27 min
Has Mars Always Been Dead?

10: Has Mars Always Been Dead?

Mars ranks as NASA's number one priority in the search for exolife. Here, you delve into why Mars is so intriguing to astrobiologists and what the search has found to date. Start with a comparison of Mars and the Earth, then watch the first-ever observation of water ice on Mars sublimating into vapor.

28 min
Evidence for Fossilized Life from Mars

11: Evidence for Fossilized Life from Mars

In 1996, NASA claimed to have found evidence of past life on Mars inside an unassuming meteor. Evaluate the three points scientists gave in support of the microbes being Martian in origin to determine their validity. Then, learn about the theory of panspermia and meet the water bear, a tiny animal capable of surviving the extreme conditions of outer space.

28 min
Could Life Ever Have Existed on Venus?

12: Could Life Ever Have Existed on Venus?

Venus is the closest planet to the Earth and the next planet moving toward the sun, so it is a logical place to look for life. However, Venus is extremely hot and dry. Could life ever have existed? Explore the nightmarish conditions on Venus and learn why all the water vanished.

31 min
Liquid Assets-The Moons of Jupiter

13: Liquid Assets-The Moons of Jupiter

Gas giant Jupiter is unlikely to inhabit life-but what about its moons? Look quickly at the importance that Galileo's discovery of Jupiter's moons had for the powerful Medici family before moving on to examine the connection between the moons' mean motion resonance and the possibility of subsurface life existing in the ice-covered oceans of Europa, Ganymede, and possibly, Callisto.

31 min
Liquid on Titan and Enceladus

14: Liquid on Titan and Enceladus

Continue traveling to the cold gas giant Saturn and its large moon, Titan. Watch a video featuring actual data taken by the Huygens Probe as it pierces the thick atmosphere and lands on the surface of this frozen world, and witness the surprising Earth-like structures this probe and its mother ship found on their journey to Saturn's moons.

32 min
Discovery of Extrasolar Planets

15: Discovery of Extrasolar Planets

Is our solar system common or rare? As you investigate planets orbiting around other stars, learn how the use of adaptive optics allows extrasolar planetary scientists to discover new alien solar systems with ground telescopes, and explore the three main ways astronomers detect planets: small "radio velocity wobbles," "transits," and direct imaging.

29 min
The Kepler Spacecraft's Planets

16: The Kepler Spacecraft's Planets

The Kepler mission is changing everything we know about extrasolar planets. Learn how this supersensitive-imaging instrument works to monitor 157,000 stars continuously for years and what it has uncovered since launching in 2009. But first, review the transit effect created when a parent star crosses its orbiting planet.

30 min
A Tour of Exotic Alien Solar Systems

17: A Tour of Exotic Alien Solar Systems

Based on data from Kepler, there are thought to be four main classes of transiting planets: hot Jupiters, hot Neptunes, super-Earths, and Earth-like planets. In this lecture, you will look at detailed highlights of the most fascinating examples of each of these new classes of alien worlds, from most to least massive.

31 min
Extraterrestrial Intelligent Life

18: Extraterrestrial Intelligent Life

How common is simple life is in our universe? What about intelligent life? Start to answer these questions by estimating the prevalence of prokaryotic single-celled microbes and reviewing the process of evolution. Evaluate arguments in the book Rare Earth by Ward and Brownlee claiming that while microbial life is common, only Earth has intelligent life. Finally, touch on how aliens might appear.

29 min
SETI-The Search for Intelligent Life

19: SETI-The Search for Intelligent Life

In a lecture that "skims right on the edge of science fact and science fiction," delve into the search for extraterrestrial life, or SETI, as the method used to gauge the likelihood of intelligent communicating civilizations is known. Look closely at the Drake Equation-the mathematical rubric commonly used in the field of SETI-and consider the challenge of communicating across our enormo...

31 min
The Fermi Paradox-Where Is Everyone?

20: The Fermi Paradox-Where Is Everyone?

After 50 years of SETI, we have zero hard evidence of alien civilizations, "cosmic wanderlust" resulting in Earth visitations, or UFOs being extraterrestrial in nature, despite-or perhaps because of-the expansiveness of the galaxy. Speculate on reasons for, and solutions to, this so-called Fermi Paradox.

31 min
Space Travel-A Reality Check

21: Space Travel-A Reality Check

Space is so vast that inventing a method of faster-than-light travel is the only way humans could conceivably travel the cosmos conveniently. How hard is space travel, really? In this mind-bending lecture, review the obstacles to space travel and consider their theoretical solutions-from combining matter and antimatter into energy, to taking "short cuts" via warp drive and wormholes.

32 min
Terraforming a Planet

22: Terraforming a Planet

Terraforming is a new scientific concept whereby an uninhabitable planetary environment is engineered to become more Earth-like to support human life. Explore how this complex process would play out on the two planets considered potential candidates, Mars and Venus, to fully understand the individual steps involved and the technologies necessary to achieve those steps.

30 min
The Future of Terrestrial Life

23: The Future of Terrestrial Life

Professor Close highlights why we shouldn't be complacent about the long-term viability of Earth and presents the timescale in which humans will need to leave Earth or become vulnerable to extinction. Inspect historical evidence indicating that Earth is warming, and learn what will happen to the atmosphere in the future.

32 min
The Search for Another Earth

24: The Search for Another Earth

Now that you've seen why humanity will eventually have to leave Earth, consider astronomers' next steps, challenges, and planned missions. Examine why specialized optical systems called coronagraphs are necessary to detect habitable Earths, and how the use of direct imaging spectra is crucial to identifying whether the biomarkers of life are present on other worlds.

36 min