Everything we can see with our eyes and with powerful instruments-everything we think of as atom-based matter-is only 5 percent of what we know exists. The rest of the contents of the cosmos is invisible to our current methods of detection-but something out there is holding galaxies and galaxy clusters together, and something else is causing space itself to fly apart. These invisible components are dark matter and dark energy, the most eagerly studied subjects in astronomy and particle physics today.
Dark Matter, Dark Energy: The Dark Side of the Universe
Examine the key concepts of an expanding universe from Albert Einstein to Edwin Hubble, led by a theoretical physicist.
Rated 5 out of
5
by
BobbyBrown from
Quick Review
Excellent Lectures from Sean Carroll. He successfully explains some of the difficult aspects of modern cosmology, Very Enjoyable.
Date published: 2024-03-02
Rated 5 out of
5
by
HJRT from
Engaging and well organized progression of concept
I found this to be an excellent course. Dr. Carroll presents the complex subject matter as a well organized and engaging progression of ideas, with clearly understood examples as analogies to more complex principles. Excellent graphics accompany the verbal explanations. Although my background in chemistry is now many years in the past, I have always been fascinated by particle physics and welcome these years of retirement to indulge my interest in this subject matter. Even though this course was new in 2007 and it is now the end of 2023, I found it to be an appropriate background for Dr. Carroll's new (2023) course, The Many Hidden Worlds of Quantum Mechanics, which I have just started viewing.
Date published: 2023-12-09
Rated 3 out of
5
by
RamondoBob from
Redshifting Information
The first half of the course goes into the Standard Model of Particle Physics. I found it informative and interesting. But when Prof Carroll actually got into dark matter and dark energy in the second half of the course, it went so far above my head and was moving away so quickly that the information was red-shifting. I was disappointed that I understood so little of it. I guess it is called "dark" for a reason. I want to assume that this wasn't because I'm an idiot. I will assume that the information was very difficult, and you really need a PhD in cosmology to really understand it. Yeah, that's my story, and I'm sticking to it.
Others have commented that the course needs an update. I agree. The course came out in 2007. The penultimate lesson in the course described some of the promising upcoming research about to happen in cosmology just after 2007. I suspect a lot has happened since then. I tried to get online and find out what has happened to the projects Prof Carroll mentioned, but it required a lot of digging. We need a quick summary from Prof Carroll. There is precedent for this. Alex Filippenko's astronomy course, Understanding the Universe, came out in 1998 but received an update in 2003.
Date published: 2023-02-25
Rated 5 out of
5
by
JPM54 from
Good foundation of physics
This course aims to explain the current (as of 2008) theories about dark matter and dark energy. But in the process, it gives a very good foundation of modern physics, including the general theory of relativity, the standard model of particle physics as well as quantum mechanics. It would be great if professor Carroll would give an update on the developments achieved in the last 15 years given that he is very optimistic about a number of new studies to be conducted in the short term. Of course there is an update already on the discovery of the Higgs Bosom particle but nevertheless an update on string theory, the coincidence problem, the various models of inflation, gravity, etc. seems warranted.
Date published: 2023-02-21
Rated 3 out of
5
by
Robodoc58 from
Dated. Time to update! It's 2023!
The professor is unequivocally engaging and informative. He clarifies esoteric and difficult-to-comprehend topics. BUT! The Great Courses need to come to address a ballooning issue: obsolescence! I, and others, have commented on this matter. While lectures on history, ancient history, music, art, may not age to any great degree, those on sciences (including the dismal science of economics) most certainly move on. This course was copy-writed in 2007. The lecturer makes forward-looking statements to scientific endeavours that will take place in 2007, 2008, 2010. Guess what? It is now 2023! Time to completely revise or retire this course.
Date published: 2023-01-28
Rated 5 out of
5
by
wds17 from
the higgs boson
the higgs boson was found in 2013............................................
Date published: 2022-12-31
Rated 5 out of
5
by
George52 from
Clear and Engaging
Although the course is becoming a bit dated, as any science course is bound to do, the course provided me with a foundation to appreciate the discoveries of the Higgs Boson and gravity waves, and why they matter.
The lecturer was clear, and at times quite funny in a dry way.
Thoroughly enjoyed and profited from the course.
But it could use an update. 2007, in science, is an eternity ago.
Date published: 2022-12-29
Rated 5 out of
5
by
frankomd from
Excellent
Really detailed series. Does assume some background in cosmology and particle physics, IMO. Now I’d like to see at least a brief 2020’s update from Carroll sometime.
Date published: 2022-10-28
Overview
About
Sean Carroll is the Homewood Professor of Natural Philosophy at Johns Hopkins University and both a member of the Fractal Faculty and an External Professor at the Santa Fe Institute. He received his PhD in Astrophysics from Harvard University. He is the author of several books, including Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime, and the host of the weekly Mindscape podcast. He has been awarded prizes and fellowships by the National Science Foundation, NASA, and the Guggenheim Foundation, among others.
01: 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
02: 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
03: 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
04: 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
05: 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
06: 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
07: 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
08: 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
09: 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
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
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
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
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
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
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
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
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
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
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
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
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
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
