9th June 2020
About the host
Dr. Valerie Jamieson is creative director of New Scientist Events and hosts a programme of evening lectures, masterclasses and New Scientist Live. Previously she ran the New Scientist features desk and specialised in writing and editing features about the latest ideas in physics, astronomy and mathematics. She has a PhD in experimental high-energy physics.
About the speaker:
Dan Hooper is a senior scientist and the head of the theoretical astrophysics group at the Fermi National Accelerator Laboratory, as well as a professor of astronomy and astrophysics at the University of Chicago. His research focuses on the interface between particle physics and cosmology, and is especially interested in questions about dark matter and the early universe. He is the author of three books, including At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds
Explore the mysteries of the universe’s first seconds at the latest New Scientist online event.
Over the past few decades, we have made incredible discoveries about how our cosmos evolved over the past 13.8 billion years. But there remains a critical gap in our knowledge: we still know very little about what happened in the first seconds after the big bang.
In this talk, Dan Hooper examined how physicists are using the Large Hadron Collider and other experiments to re-create the conditions of the big bang, and to address mysteries such as how our universe came to contain so much matter and so little antimatter.
Could these tools enable us to discover the nature of dark matter and how it was formed in our universe’s first moments? Can we lift the veil on the era of cosmic inflation, which led to the creation of our world as we know it?
The presentation was followed by a Q&A session featuring questions posed by the live audience.
The following are notes from the on-line lecture. Even though I could stop the video and go back over things there are likely to be mistakes because I haven’t heard things correctly or not understood them. I hope Professor Hooper and my readers will forgive any mistakes and let me know what I got wrong.
At the Edge of Time
Exploring the mysteries of Our Universe’s First seconds
The following image comes from the Hubble deep field programme
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope’s Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995
The field is so small that only a few foreground stars in the Milky Way lie within it; thus, almost all of the 3,000 objects in the image are galaxies, some of which are among the youngest and most distant known. By revealing such large numbers of very young galaxies, the HDF has become a landmark image in the study of the early universe.
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope but it is one of the largest and most versatile, well known both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA’s Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope
The Hubble Ultra-Deep Field (HUDF) is an image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies. The original release was combined from Hubble Space Telescope data accumulated over a period from September 24, 2003, through to January 16, 2004. Looking back approximately 13 billion years (between 400 and 800 million years after the Big Bang) it has been used to search for galaxies that existed at that time. The HUDF image was taken in a section of the sky with a low density of bright stars in the near-field, allowing much better viewing of dimmer, more distant objects. In August and September 2009, the HUDF field was observed at longer wavelengths (1.0 to 1.6 µm) using the infrared channel of the recently attached Wide Field Camera 3 (WFC3) instrument. When combined with existing HUDF data, astronomers were able to identify a new list of potentially very distant galaxies.
In the image above there are around 5,500 visible galaxies, with some of them being billions of light years away and 13.2 billion years old — just 450 million years after the Big Bang and the creation of the universe.
Because it takes time for the light to reach us from these galaxies, we know we are looking at galaxies that were around before ours. The image above is actually what that region of space looked like 13.2 billion years ago.
The image, officially dubbed the Extreme Deep Field (XDF), is constructed out of 2,000 images of the southern sky (constellation Fornax), captured over a decade. The individual images were captured by both the Advanced Camera for Surveys (2x 8-megapixel CCD), and the newer Wide Field Camera 3 (2x 8MP CCD, plus an extra 1MP CCD tuned specifically to infrared light). The total exposure time, in case you’re an astronomer or night sky photographer, is 2 million seconds.
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighbouring capacitor. CCD sensors are a major technology used in digital imaging.
We have a good understanding of how and why the Universe has changed since the “Big Bang”
Just over one hundred years ago scientists did not understand the past of the Universe or its origin. They had no tools.
Albert Einstein and General Relativity changed all that
Albert Einstein (14 March 1879 – 18 April 1955) was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics).
General relativity (GR), also known as the general theory of relativity (GTR), is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton’s law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations.
General relativity is a theory of gravitation that was developed by Albert Einstein between 1907 and 1915. According to general relativity, the observed gravitational effect between masses results from their warping of spacetime.
Space and time can be changed. Space can curve, expand and contract.
Imagine how the Universe can evolve.
In 1920 Edwin Hubble saw the Universe as expanding.
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time.
Hubble saw galaxies as receding from each other and the further away they are the faster they move. The image above illustrates 2 points in space getting further apart with time.
What is space expanding into?
Well the answer is simply that space is expanding. It is not going from empty to not empty. Space is simply getting bigger.
The baby Universe was smaller, denser with much higher energy/temperature than it is today.
A popular misconception is that the Big Bang was some sort of cosmic explosion
Cosmologists say that it didn’t happen in one point of space but actually describes the Universe at that time. It happened everywhere.
The above image gives us a cosmic tour of history. The first stars appeared 200 million years ago. 9 billions years later our Sun appeared. Then 4.5 billion years later human history began.
However the timeline is incomplete. Look at the log scale version
Log scale version
Look much further back and close to the Big Bang. Look at the transition at a few hundred years after the Big Bang when atoms started to form.
The transition happened at a temperature of 3000K. A hot plasma of matter/energy (the temperature is 2.7K now). This transition temperature was important because 300K is the “melting point” of an atom. Before this the atom existed in parts.
Plasma is opaque to light so prior to the transition light couldn’t get through and we can’t see what happened before the transition.
As the temperature dropped atoms formed and the resultant neutral gas became transparent to light.
Light is deposited into space a few thousand years after the Big Bang
The cosmic microwave background (CMB, CMBR), in Big Bang cosmology, is electromagnetic radiation as a remnant from an early stage of the universe, also known as “relic radiation”. The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination. With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark. However, a sufficiently sensitive radio telescope shows a faint background noise, or glow, almost isotropic, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum.
The blue/orange regions show the temperature densities 380000 years after the Big Bang. It shows us the forms of matter and energy existed at the time and how the Universe evolved. It gives us more confidence in our understanding of the evolution of the Universe.
The temperature at 1.5 minutes after the Big Bang was 1 billion degrees kelvin. At this point there was a big nuclear fusion. Prior to this there were no complete nuclei.
Combining general relativity and nuclear physics allows us to deduce how much of the original atoms formed and compare with what is around today. There is good agreement.
Gaing back to a millionth of a second before the Big Bang it was very hot. First protons and neutrons formed. Prior to this transition only quarks and gluons existed.
The Standard Model of particle physics is the theory describing three of the four known fundamental forces (the electromagnetic, weak, and strong interactions, and not including the gravitational force) in the universe, as well as classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists around the world, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, confirmation of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy.
As the temperature dropped neutrons and protons formed. We can’t directly observe these very early transitions but we can extrapolate backwards with equations.
We can try to recreate the transitions using particle accelerators such as the LHC
The Large Hadron Collider (LHC) is the world’s largest and highest-energy particle collider and the largest machine in the world. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundreds of universities and laboratories, as well as more than 100 countries. It lies in a tunnel 27 kilometres in circumference and as deep as 175 metres beneath the France–Switzerland border near Geneva.
Protons are accelerated to 0.999999990 of the speed of light. Beams of protons collide 6 million times per second. Einstein’s famous formula E = mc2 is exploited.
This process, hopefully, creates different particles common at the Big Bang and helps us explain the standard model.
In our Universe today most of the particles that were produced at the start of the Universe don’t exist. That is why most matter is made up of up and down quarks and electrons (lepton).
A trillionth of a second after the Big Bang all possible particles existed and were copiously produced in equal amounts, popping into and out of existence. We can understand the laws of physics at this time by using the LHC. But there is still a great deal we don’t know.
We can explain the light from the cosmic microwave background.
We can explain how clusters of galaxies formed and why they have the characteristics they do.
We know how the lighter elements are formed.
Anything before the first few seconds we can’t observe. This leads to a number of problems such as misunderstanding what actually happened.
At some point we might have to re-think what we know.
Why do atoms exist in our Universe? Matter and antimatter should exist in equal amounts. Each electron should have a positron (opposite charges) for instance and when matter meets antimatter annihilation should occur. Equal amounts of matter and antimatter should equal total annihilation.
Therefore, no atoms.
There should be mirror symmetry. Matter and antimatter should have been created in equal amounts.
So why does our Universe have more matter than antimatter?
There is no good hypothesis at the moment. It is a big mystery.
We can see the visible parts of the Andromeda galaxy so using the laws of gravity to work out the theoretical rotational speed.
Prediction of rotation curve of andromeda
The outer stars move more slowly than the inner stars.
Since the 1970s we have actually been able to measure the speed. This speed is greater than can be explained. This implies that there must be a lot more mass than can be seen.
This dark matter has a different distribution to visible matter. There is a large halo of dark matter.
The top curve shows the actual rotation speed of the Andromeda galaxy.
If dark matter were a gas of feebly interacting matter, we can deduce the structures we observe in our Universe today.
The above images show how gas dark matter could evolve as the Universe expands. Top left is the earliest. Gravity starts to act and collapse matter. The bottom right, when compared to the real distribution, shows a very good agreement.
If we think there is a large amount of dark matter in our Universe, we can explain why galaxies and groups of galaxies take the shape they do. A leading role in the structure of the Universe we observe.
What is dark matter?
10/15 years ago, we would say it was WIMPs. We could calculate how many were produced in particle physics and their rate of destruction as the Universe expanded, then compare to the dark matter present now.
We thought we knew how to test for WIMPs
Laboratori Nazionali del Gran Sasso (LNGS) is the largest underground research center in the world. Situated below Gran Sasso mountain in Italy, it is well known for particle physics research by the INFN. In addition to a surface portion of the laboratory, there are extensive underground facilities beneath the mountain. The nearest towns are L’Aquila and Teramo. The facility is located about 120 km from Rome.
The primary mission of the laboratory is to host experiments that require a low background environment in the fields of astroparticle physics and nuclear astrophysics and other disciplines that can profit of its characteristics and of its infrastructures. The LNGS is, like the three other European underground astroparticle laboratories (Laboratoire Souterrain de Modane, Laboratorio subterráneo de Canfranc, and Boulby Underground Laboratory), a member of the coordinating group ILIAS.
These laboratories have several dark matter detectors. There have been many remarkable experiments but no dark matter particles have been observed. Most attractive theories of WIMPs have been ruled out.
Dark matter could still be WIMPs but could have been formed in different ways or the origin of the Universe could be much different to how we imagined.
How fast is the Universe expanding?
There are three kinds of idea of how the Universe will end.
General relativity calculations of the expansion depend on the amount of matter present.
Cosmologists have tried to work out which of the three idea are correct.
By the 1990s cosmologists came up with a fourth scenario as the expansion rate seems to be accelerating.
Space itself seems to contain a fixed density of dark energy.
Unlike other forms of energy and matter in the Universe dark energy doesn’t get diluted with expansion. So as the Universe expands dark energy produces an increasing effect – to speed up the expansion rate.
What was happening at the extremely early age of the Universe, 10-32 seconds after the Big Bang.
In the 1960s/1970s the Big Bang couldn’t explain why the Universe is so uniform and geometrically flat.
A flat geometry is equivalent to saying that the geometry is Euclidean, that is, the 5th postulate of Euclid is accepted. A consequence is that triangles have angles that add up to 180 degrees. Another way of saying a flat geometry, is that a flat geometry is one that describes a mathematical space with zero (intrinsic) curvature.
Euclidean geometry is a mathematical system attributed to Alexandrian Greek mathematician Euclid, which he described in his textbook on geometry, the Elements. Euclid’s method consists in assuming a small set of intuitively appealing axioms, and deducing many other propositions (theorems) from these. Although many of Euclid’s results had been stated by earlier mathematicians, Euclid was the first to show how these propositions could fit into a comprehensive deductive and logical system. The Elements begins with plane geometry, still taught in secondary school (high school) as the first axiomatic system and the first examples of formal proof. It goes on to the solid geometry of three dimensions. Much of the Elements states results of what are now called algebra and number theory, explained in geometrical language
[5th and the parallel postulate]: That, if a straight line falling on two straight lines make the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, meet on that side on which the angles are less than two right angles.
Euclid (300 BC), sometimes called Euclid of Alexandria to distinguish him from Euclid of Megara, was a Greek mathematician, often referred to as the “founder of geometry” or the “father of geometry”. He was active in Alexandria during the reign of Ptolemy I (323–283 BC). His Elements is one of the most influential works in the history of mathematics, serving as the main textbook for teaching mathematics (especially geometry) from the time of its publication until the late 19th or early 20th century. In the Elements, Euclid deduced the theorems of what is now called Euclidean geometry from a small set of axioms. Euclid also wrote works on perspective, conic sections, spherical geometry, number theory, and mathematical rigour.
The English name Euclid is the anglicized version of the Greek name Εὐκλείδης, which means “renowned, glorious”
In the 1980s cosmic inflation theory was developed.
It is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10−36 seconds after the conjectured Big Bang singularity to sometime between 10−33 and 10−32 seconds after the singularity and the volume increased to 1075 times the size.
Following the inflationary period, the universe continued to expand, but at a slower rate. The acceleration of this expansion due to dark energy began after the universe was already over 9 billion years old (~4 billion years ago).
It explains the origin of the large-scale structure of the cosmos. Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the Universe (see galaxy formation and evolution and structure formation). Many physicists also believe that inflation explains why the universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the universe is flat, and why no magnetic monopoles have been observed.
The detailed particle physics mechanism responsible for inflation is unknown. The basic inflationary paradigm is accepted by most physicists, as a number of inflation model predictions have been confirmed by observation; however, a substantial minority of scientists dissent from this position. The hypothetical field thought to be responsible for inflation is called the inflaton.
The theory made a few specific predictions.
The patterns of light in the cosmic microwave background would have some specific features.
Near scalar variants and adiabatic fluctuations
Primordial fluctuations are density variations in the early universe which are considered the seeds of all structure in the universe. Currently, the most widely accepted explanation for their origin is in the context of cosmic inflation. According to the inflationary paradigm, the exponential growth of the scale factor during inflation caused quantum fluctuations of the inflaton field to be stretched to macroscopic scales, and, upon leaving the horizon, to “freeze in”. At the later stages of radiation- and matter-domination, these fluctuations re-entered the horizon, and thus set the initial conditions for structure formation.
The statistical properties of the primordial fluctuations can be inferred from observations of anisotropies in the cosmic microwave background and from measurements of the distribution of matter, e.g., galaxy redshift surveys. Since the fluctuations are believed to arise from inflation, such measurements can also set constraints on parameters within inflationary theory.
Over time the patterns observed in the cosmic microwave background were evidence that the exponential expansion did take place at the earliest stages after the Big Bang.
This theory takes a small space and rapidly gives a multitude of universes. At 10-32 second the volume increased by a factor of 1075
Different parts of space will stop inflating at different times. Eventually something like our Universe came about.
However, this leads to the idea that there should be an infinite number of universes.
Some of these universes might be like ours. Some might be very different with different laws of physics, matter & energy and different number of dimensions.
There is a lot to doubt about the formation of the early Universe. There are significant discoveries to be made in the future.
New discoveries will make incremental changes to our current understanding of the early Universe.
Major paradigm changes will lead to radical reimagining of the laws of physics at the early years of the Universe.
What would it have been like to be a physicist in 1904?
Good as they seemed to be confident in what they think of the Universe. Newtonian physics applied to everything. There were loose ends but they were ignored:
1) Speed of light is constant, but why?
2) Mercury ellipse precession didn’t match observation
3) Where did the Sun get its energy from?
4) What about the inner working of the atom? The Newtonian models weren’t stable. What caused spectral lines?
There wasn’t an incremental change of knowledge because in 1905 work on quantum physics began. Albert Einstein’s work on the photoelectric effect.
The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. This phenomenon is commonly studied in electronic physics and in fields of chemistry such as quantum chemistry and electrochemistry.
In 1905, Albert Einstein explained why the maximum kinetic energy of the outgoing electrons depended on the light frequency rather than on its intensity, by describing light as composed of discrete quanta, now called photons, rather than continuous waves. Based upon Max Planck’s theory of black-body radiation, Einstein theorized that the energy in each quantum of light was equal to the frequency multiplied by a constant, later called Planck’s constant. A photon above a threshold frequency has the required energy to eject a single electron, creating the observed effect. This discovery led to the quantum revolution in physics and earned Einstein the Nobel Prize in Physics in 1921. The photoelectric effect can be analysed solely in terms of waves though not as conveniently.
Also, in 1905 Albert Einstein published the theory of special relativity.
Newtonian physics was being torn down.
Is 2020 the 1904 of cosmology?
1. What colour was the Big Bang?
Blue/white when it was really hot at the beginning becoming redder as the Universe got older.
2. Why did matter and anti-matter not annihilate each other at the start of the Universe.
We don’t really know. 10 billion pieces of antimatter and 10 billion and 1 pieces of matter would result in 1 piece of antimatter,
In 1967, Andrei Sakharov proposed a set of three necessary conditions that a baryon-generating interaction must satisfy to produce matter and antimatter at different rates. These conditions were inspired by the recent discoveries of the cosmic background radiation and CP violation in the neutral kaon system. The three necessary “Sakharov conditions” are:
· Baryon number violation.
· C-symmetry and CP-symmetry violation.
· Interactions out of thermal equilibrium.
Baryon number is the number of quarks
Charge conjugation is a transformation that switches all particles with their corresponding antiparticles, and thus changes the sign of all charges: not only electric charge but also the charges relevant to other forces.
In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C symmetry) while its spatial coordinates are inverted (“mirror” or P symmetry).
Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be in thermal equilibrium with itself if the temperature within the system is spatially uniform and temporally constant.
Systems in thermodynamic equilibrium are always in thermal equilibrium, but the converse is not always true. If the connection between the systems allows transfer of energy as heat but does not allow transfer of matter or transfer of energy as work, the two systems may reach thermal equilibrium without reaching thermodynamic equilibrium.
Andrei Dmitrievich Sakharov (21 May 1921 – 14 December 1989) was a Russian nuclear physicist, dissident, Nobel laureate, and activist for disarmament, peace and human rights.
At the start of the Universe there were non-equilibrium conditions
3. How do we know that the Universe began 13.8 billion years ago?
Investigating the expansion of the Universe and looming at temperature patterns in the cosmic microwave background.
4. How much dark matter was around when the Universe was 1ms old?
There wasn’t much matter but the quantity of dark matter is the same then as it is now.
As the photon wavelength increases its energy decreases.
5. What is dark matter if it isn’t WIMPs?
Could still be WIMPs but not the ones we are expecting. They could be axions.
The axion is a hypothetical elementary particle postulated by the Peccei–Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics (QCD). If axions exist and have low mass within a specific range, they are of interest as a possible component of cold dark matter.
In theoretical physics, quantum chromodynamics (QCD) is the theory of the strong interaction between quarks and gluons, the fundamental particles that make up composite hadrons such as the proton, neutron and pion.
Hidden sector theories
In particle physics, the hidden sector, also known as the dark sector, is a hypothetical collection of yet-unobserved quantum fields and their corresponding hypothetical particles. The interactions between the hidden sector particles and the Standard Model particles are weak, indirect, and typically mediated through gravity or other new particles. Examples of new hypothetical mediating particles in this class of theories include the dark photon, sterile neutrino, and axion.
All these theories could explain why we haven’t seen dark matter yet.
6. What happened before the Big Bang
Stephen Hawking made a comment “Asking what came before the Big Bang … would be like asking what lies south of the South Pole.”
He proposed that there’s no end, or beginning, at all.
Stephen William Hawking CH CBE FRS FRSA (8 January 1942 – 14 March 2018) was an English theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge at the time of his death. He was the Lucasian Professor of Mathematics at the University of Cambridge between 1979 and 2009.
So we can’t talk about what happened before the Big Bang as time only started with it. We don’t know!!!
7. What triggered the Big Bang and why does the Universe exist?
No compelling answer. It just is.
8. Why would different universes have different laws of physics?
The situation might be different at the start. As an example, in most places ice melts to water and then boils to form a gas (steam) however in a few places ice will miss out the middle stage to become steam.
String theory would lead to different laws and matter/energy.
9. Can we detect other universes?
No information can pass between them however studying our own Universe could produce evidence.
Books by Dan Hooper
A new look at the first few seconds after the Big Bang—and how research into these moments continues to revolutionize our understanding of our universe
Scientists in the past few decades have made crucial discoveries about how our cosmos evolved over the past 13.8 billion years. But there remains a critical gap in our knowledge: we still know very little about what happened in the first seconds after the Big Bang. At the Edge of Time focuses on what we have recently learned and are still striving to understand about this most essential and mysterious period of time at the beginning of cosmic history.
Taking readers into the remarkable world of cosmology, Dan Hooper describes many of the extraordinary and perplexing questions that scientists are asking about the origin and nature of our world. Hooper examines how we are using the Large Hadron Collider and other experiments to re-create the conditions of the Big Bang and test promising theories for how and why our universe came to contain so much matter and so little antimatter. We may be poised to finally discover how dark matter was formed during our universe’s first moments, and, with new telescopes, we are also lifting the veil on the era of cosmic inflation, which led to the creation of our world as we know it.
Wrestling with the mysteries surrounding the initial moments that followed the Big Bang, At the Edge of Time presents an accessible investigation of our universe and its origin.
The twentieth century was astonishing in all regards, shaking the foundations of practically every aspect of human life and thought, physics not least of all. Beginning with the publication of Albert Einstein’s theory of relativity, through the wild revolution of quantum mechanics, and up until the physics of the modern day (including the astonishing revelation, in 1998, that the Universe is not only expanding, but doing so at an ever-quickening pace), much of what physicists have seen in our Universe suggests that much of our Universe is unseen–that we live in a dark cosmos.
Everyone knows that there are things no one can see–the air you’re breathing, for example, or, to be more exotic, a black hole. But what everyone does not know is that what we can see–a book, a cat, or our planet–makes up only 5 percent of the Universe. The rest–fully 95 percent–is totally invisible to us; its presence discernible only by the weak effects it has on visible matter around it.
This invisible stuff comes in two varieties–dark matter and dark energy. One holds the Universe together, while the other tears it apart. What these forces really are has been a mystery for as long as anyone has suspected they were there, but the latest discoveries of experimental physics have brought us closer to that knowledge. Particle physicist Dan Hooper takes his readers, with wit, grace, and a keen knack for explaining the toughest ideas science has to offer, on a quest few would have ever expected: to discover what makes up our dark cosmos.
An accessible introduction to the physics theory about supersymmetry explains its potential for resolving key gaps in particle physics and rendering the universe more predictable, in a guide for lay readers that explains basic tenets in a comprehensive and lighthearted style.
These 12 half-hour lectures are about what Einstein got wrong. He may have kindled a scientific revolution with his famous theory of relativity and his proof that atoms and light quanta exist, but he balked at accepting the most startling implications of these theories – such as the existence of black holes, the big bang, gravity waves, and mind-bendingly strange phenomena in the quantum realm. In a course that assumes no background in science and uses very little math, research physicist Dan Hooper of the Fermi National Accelerator Laboratory and the University of Chicago focuses on Einstein’s personal
qualities that made him a heavy hitter with relativity but also a strikeout king in many of his other ideas.
You start with two lectures on Einstein’s special and general theories of relativity, and in a later lecture you cover his founding role in quantum theory. All are titanic achievements. The balance of the course deals with his false starts, blind alleys, and outright blunders, which are fascinating for what they reveal about the give-and-take conduct of science. For example, the possibility of black holes, which are infinitely dense concentrations of matter, emerged from the equations of general relativity. However, the idea seemed so absurd to Einstein that he believed something in nature must prevent black holes from forming. He was wrong. Similar considerations led him to doubt the existence of gravity waves, insist that the universe must be static and eternal, and hold out for a deterministic theory that would solve the weird paradoxes of quantum mechanics. Again, he was wrong. Dr. Hooper closes with a lecture on the missteps of other great physicists – Johannes Kepler, Galileo Galilei, and Isaac Newton – proving that Einstein is in good company. Even geniuses struggle to find the truth.
Dark matter has been the big topic of cosmologists for decades: There must be a gigantic source of energy that drives the observed movements of stars and galaxies without being observable. Dan Hooper, professor of physics at the Fermi National Accelerator Laboratory in Batavia, Illinois, uses this unsolved puzzle as an exciting introduction to cosmology – and at the same time provides a prime example of how scientific curiosity is translated into systematic research.
Videos by Dan Hooper