Dark Matter, Dark Energy: The Dark Side of the Universe

Rated 5 out of 5 by from Can not wait for a sequel Excellent course, each lecture is interesting and very entertaining
Date published: 2020-08-12
Rated 5 out of 5 by from What we can't see can inform us This is an excellent course. It was made prior to the Planck spacecraft launch and discovery of the Higgs boson, but both are mentioned. Doctor Carroll is a remarkably good instructor who not only tells us where we are and where we are headed, but also why the destination is important and the questions we should ask along the way. Finally, take heart those with limited math skills. If you can add 5%, 25%, and 70% and get 100%, you are mathematically qualified to understand this course.
Date published: 2020-08-03
Rated 5 out of 5 by from Very understandable The lectures are just the right length and not boring! Explanations are in language a non-astronamer, like myself can understand. Just wish I could figure out how to get closed captioning along with the lectures.
Date published: 2020-06-17
Rated 5 out of 5 by from Professionally presented!! Sean Carroll is one of the most engaged and knowledgeable teacher of difficult subjects in science: particle physics. It was a delight to learn this subject. It will be sensible to watch again because of my interest in such material.
Date published: 2020-04-29
Rated 3 out of 5 by from Out of date This was done in 2007. There have been a lot of new discoveries since then. The Higgs boson was seen. Gravity waves were detected. New questions have arisen. This course to too outdated to be offered. The presentation was very well done though.
Date published: 2020-02-04
Rated 5 out of 5 by from informative A course presenting a very complex subject in easy to understand lecture by a very talented lecturer.
Date published: 2019-05-18
Rated 5 out of 5 by from Outstanding presentation and explanation ! Dr. Sean Carroll presents concepts in astrophysics and particle physics in very clear and understandable format. I would highly recommend this course to anyone who is interested in the wonders of the universe in which we live.
Date published: 2019-04-15
Rated 5 out of 5 by from Stimulating I am not finished viewing this course. The material is challenging and stimulates thought. It does presents material of which I was only marginally aware . There are many things yet to be discovered and our ability to perceive them is the only limit. I gave it five stars because it stretches my awareness.
Date published: 2019-03-25
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Fundamental Building Blocks
1: Fundamental Building Blocks

Scientists now have a complete inventory of the universe, which is composed of three basic constituents: Ordinary matter includes every kind of particle ever directly observed; dark matter consists of massive particles known only because of their gravitational effects; and dark energy is a smoothly distributed component that whose density does not change as the universe expands....

33 min
The Smooth, Expanding Universe
2: The Smooth, Expanding Universe

Imagine looking into a clear night sky with perfect vision. What would you see? This lecture surveys the visible universe-from the stars in our galaxy to the cloudy patches called nebulae that astronomer Edwin Hubble proved are galaxies in their own right-and Hubble's discovery that the universe is expanding....

30 min
Space, Time, and Gravity
3: Space, Time, and Gravity

Einstein taught us that space and time can be combined into spacetime, which has the ability to evolve and grow. Indeed, what we think of as gravity is just a manifestation of the curvature of spacetime. To find things in the universe-including dark matter and dark energy-all we have to do is to map out this curvature....

30 min
Cosmology in Einstein's Universe
4: Cosmology in Einstein's Universe

The expansion of the universe is governed by its spatial curvature and energy density, both of which have specific ways of changing as the universe grows. These features are related to each other by Einstein's general theory of relativity, which can be used to model the past and possible future of the universe....

30 min
Galaxies and Clusters
5: Galaxies and Clusters

Applying the laws of dynamics to galaxies and galaxy clusters, we find that more matter is required to account for their motions than can be observed. Some of the missing mass is hot gas; however, this is still not enough, and we need to invoke some new kind of particle in galaxies and clusters: dark matter....

31 min
Gravitational Lensing
6: Gravitational Lensing

Another way to detect invisible matter is to use light as a probe of the gravitational field. Passing through curved spacetime, the path of a light ray is deflected due to gravitational lensing. Lensing demonstrates the existence of gravitational fields where there is essentially no ordinary matter....

31 min
Atoms and Particles
7: Atoms and Particles

We peer into the atom to discover the constituents of ordinary matter: nuclei and electrons. Nuclei are made of protons and neutrons, which in turn are made of quarks. Electrons and quarks are examples of fermions, or matter particles. There are also bosons, or force-carrying particles, such as photons and gluons....

31 min
The Standard Model of Particle Physics
8: The Standard Model of Particle Physics

In the 1960s and 1970s, physicists developed a comprehensive theory of known fermions and bosons. Now called the standard model, this theory fits an impressive amount of data, but it leaves two crucial puzzles: the hypothetical Higgs boson and the graviton, the carrier of the gravitational force....

31 min
Relic Particles from the Big Bang
9: Relic Particles from the Big Bang

Armed with the core principles of particle physics, we know enough about the early universe to predict how many of each type of particle should be left over from the Big Bang. These "relic abundances" are crucial to understanding the origin of dark matter and light elements....

31 min
Primordial Nucleosynthesis
10: Primordial Nucleosynthesis

The process of nucleosynthesis describes how protons and neutrons were assembled into light elements during the first few minutes after the Big Bang. We can observe these primordial elements today and check on Einsteinian cosmology and a stringent constraint on theories of dark matter....

31 min
The Cosmic Microwave Background
11: The Cosmic Microwave Background

About 380,000 years after the Big Bang, the universe had cooled sufficiently for electrons and nuclei to combine into atoms allowing light to travel much more freely. The relic photons from this era are visible to us today as the cosmic microwave background, which holds clues to the composition and structure of the universe....

31 min
Dark Stars and Black Holes
12: Dark Stars and Black Holes

Candidates for dark matter include small, dark stars called Massive Compact Halo Objects (MACHOs) and black holes. Such objects are ultimately composed of ordinary matter, of which there just isn't enough to account for the dark matter. We are forced to conclude that the dark matter is a new kind of particle....

31 min
WIMPs and Supersymmetry
13: WIMPs and Supersymmetry

Weakly interacting massive particles (WIMPs) are ideal candidates for what comprises dark matter. WIMPs may have their origins in supersymmetry, which posits a hidden symmetry between bosons and fermions, and predicts a host of new, as-yet-unobserved particles, including WIMPs....

32 min
The Accelerating Universe
14: The Accelerating Universe

In the late 1990s, two groups of astronomers found to their astonishment that the expansion of the universe is speeding up rather than slowing down. Such behavior can't be explained by any kind of matter and suggests the existence of an entirely new component: dark energy....

30 min
The Geometry of Space
15: The Geometry of Space

Precise measurements of the cosmic microwave background let us measure the total energy density of the universe by observing the geometry of space. We find that the energy in matter alone is not enough, confirming the need for dark energy....

30 min
Smooth Tension and Acceleration
16: Smooth Tension and Acceleration

Dark energy is smoothly distributed throughout the universe and its density is nearly constant, even though the universe is expanding. Unlike gas under pressure in a container, dark energy is a kind of "negative pressure"-or tension-that imparts an accelerated expansion to the universe....

31 min
Vacuum Energy
17: Vacuum Energy

The density and distribution of dark energy remain the same across all of space­time, but what exactly is dark energy? There are many possibilities, the simplest of which is vacuum energy-an constant amount of energy in every cubic centimeter of space itself. Vacuum energy is equivalent to Einstein's idea of the cosmological constant....

33 min
18: Quintessence

Another idea about dark energy is that it results from a new field in nature, analogous to the electromagnetic field but remaining persistent as the universe expands. This field is called quintessence. It would be observationally distinguishable from the cosmological constant....

30 min
Was Einstein Right?
19: Was Einstein Right?

We have inferred the existence of dark matter and dark energy from the gravitational fields they cause. In this lecture, we explore proposals that a modified theory of gravity might allow us to dispense with the need for invoking dark stuff. However, this turns out to be very difficult in practice....

32 min
20: Inflation

Before we had observational evidence that the universe is accelerating, cosmologists considered the possibility of a period of rapid acceleration at very early times-a scenario known as inflation....

31 min
Strings and Extra Dimensions
21: Strings and Extra Dimensions

We know about the dark sector because of gravity, and string theory is an ambitious attempt to unify gravitation with the other forces of nature into a theory of everything. String theory promises a theory of quantum gravity, but it also predicts extra, unseen spatial dimensions that are difficult to test....

32 min
Beyond the Observable Universe
22: Beyond the Observable Universe

The speed of light and the age of the observable universe are finite. That means we can't see the whole universe because our vision can only stretch so far. The "multi­verse"-a hypothesis of regions where conditions are very different from those we see in our observable universe-may help explain properties of dark energy....

32 min
Future Experiments
23: Future Experiments

Astronomers are designing new observatories to probe the acceleration of the universe and other cosmic phenomena. Physicists are also looking forward to new experiments that will dramatically improve our understanding of particles and forces, and how ordinary matter fits in with dark matter and dark energy....

32 min
The Past and Future of the Dark Side
24: The Past and Future of the Dark Side

The concordance cosmology is an excellent fit to a variety of data, but it presents us with deep puzzles: What are dark matter and dark energy? Why do they have the densities they do? Our own universe seems unnatural to us. That's good news, as it is a clue to the next level of understanding....

34 min
Sean Carroll

We need to push on our understanding of cosmology, particle physics, gravity, not to mention how complexity and entropy evolve through time, and eventually you'll be able to really understand what our theories predict.


Harvard University


California Institute of Technology

About Sean Carroll

Professor Sean Carroll is a Senior Research Associate in Physics at the California Institute of Technology. He earned his undergraduate degree from Villanova University and his Ph.D. in Astrophysics from Harvard in 1993. Before arriving at Caltech, Professor Carroll taught in the Physics Department and the Enrico Fermi Institute at the University of Chicago, and did postdoctoral research at the Massachusetts Institute of Technology and at the Institute for Theoretical Physics at the University of California, Santa Barbara. Professor Carroll is the author of Spacetime and Geometry: An Introduction to General Relativity, published in 2003. He has taught more than 200 scientific seminars and colloquia and given more than 50 educational and popular talks. In addition, he has written for numerous publications including Nature, New Scientist, The American Scientist, and Physics Today. Professor Carroll has received research grants from NASA, the U.S. Department of Energy, and the National Science Foundation, as well as fellowships from the Sloan and Packard foundations. He has been the Malmstrom Lecturer at Hamline University, the Resnick Lecturer at Rensselaer Polytechnic Institute, and a National Science Foundation Distinguished Lecturer. While at MIT, Carroll won the Graduate Student Council Teaching Award for his course on general relativity. In 2006 he received the Arts and Sciences Alumni Medallion from Villanova University.

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