At present it’s as though the distance ladder observed by Hubble and Webb has firmly set an anchor point on one shoreline of a river, and the afterglow of the Big Bang observed by our Planck mission from the beginning of the Universe is set firmly on the other side. How the Universe’s expansion was changing in the billions of years between these two endpoints has yet to be directly observed.
📹 ESA – European Space Agency 📸 NASA, ESA, CSA, Space Telescope Science Inst., A. Riess (JHU/STScI)
This evidence seems to suggest that the dark matter is particles that are less than four times the mass of a proton and are moving at non-relativistic speeds. This is consistent with dark matter particles being so-called WIMPs: https://en.wikipedia.org/wiki/Weakly_interacting_massive_particles.
What if everything in the universe came to your doorstep…in a box?! What The Physics is BACK! Future episodes will explore the universe—but first, let’s unbox it.
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SCIENTIFIC NOTES:
Explosive young stars
* The average lifetime of a star is about 10 billion years, but the bigger the star, the shorter its life. One rare type of star, called a hypergiant, can be tens, hundreds, or even a thousand times the mass of our sun. These stars burn out and explode into supernovae in just a few million years. http://www.guide-to-the-universe.com/hypergiant-star.html
Black holes
* Black holes form from the collapse of a massive star at the end of its life, but this only happens in stars about three times as massive as the sun. http://burro.case.edu/Academics/Astr201/EndofSun.pdf
How big is the universe?
* Probably infinite. No one knows the size of the universe for sure, and we may never know, but the latest thinking is that it probably goes on forever. https://map.gsfc.nasa.gov/universe/uni_shape.html
Standard cosmological model
* According to the standard cosmological model, the universe started with a big bang, underwent rapid inflation within the first fraction of a second, and continues to expand, driven by a vacuum energy called dark energy. All of the structure we see in the universe has come from interactions between dark energy and dark matter (which accounts for about 85% of the universe’s matter). This model describes and predicts many phenomena in the universe but is not perfect. https://physics.aps.org/articles/v8/108
False vacuum model
* The false vacuum model is a real, albeit unlikely theory. All the fundamental forces of nature have corresponding fields (e.g., gravitational fields, magnetic fields, etc.), and we generally believe that the universe is at rest in a global minimum of the potentials of those fields. But if we are instead at rest in a local minimum, or a “false vacuum,” the universe could potentially be nudged, catastrophically, into a lower minimum.
Recycling stars into life
* Before the first stars, the universe was all hydrogen and helium. All heavier elements, including the building blocks of life, were forged in stars.
Dark matter and dark energy
* Only 5% of the universe is made up of matter we can see. The “missing mass” later dubbed dark matter was first noticed in the 1930s; dark energy was discovered in the 1990s. In both cases, their existence was inferred by their effect on objects they interact with. However, they are still not directly observable, so nobody knows yet what they are made of.
Leftover light from the Big Bang
* The theory of the Big Bang predicted the existence of cool radiation pervading the universe, left over from its beginning. In an accidental discovery, two New Jersey scientists discovered the cosmic microwave background, a nearly uniform bath of radiation throughout the universe at a temperature of about 3 Kelvin, or -454 degrees Fahrenheit.
Gravitational waves
* Albert Einstein predicted the existence of gravitational waves in his theory of general relativity in 1916. According to his theory, the acceleration of massive objects, like black holes, should send ripples through space-time at the speed of light. A century after his prediction, two merging black holes sent a ripple through space-time that was detected on Earth as a signal that stretched the 4-kilometer arms of a detector by less than 1/1,000 the width of a proton.
Cosmic dust
* Cosmic dust is cast off from stars at the end of their lives and hovers in galaxies as clouds. These clouds of dust absorb ultraviolet and visible light, obscuring much of what lies behind them. This makes it notoriously difficult to study things like the dusty center of our galaxy.
The observable universe
* The universe is 13.8 billion years old. Since the distance we can observe is limited by the time it takes light to travel to Earth, we can only ever observe a fraction of the universe: an expanding sphere around us that is now about 46 billion years in radius. However, the universe is much larger than what we can observe.
CREDITS:
Host, Writer, Producer: Greg Kestin
Animation & Compositing: Danielle Gustitus
Contributing Writers: Lissy Herman, HCSUCS
Filming, Writing, & Editing Contributions from:
Samia Bouzid and David Goodliffe
Creation of Sad Star Image: Drew Ganon
Special thanks:
Julia Cort
Lauren Aguirre
Ari Daniel
Anna Rothschild
Allison Eck
Fernando Becerra
And the entire NOVA team
Even if you don’t, watch anyway. Maybe I’ll convince you. And if not, maybe I’ll impart some important skills or perspectives upon you. A lot of what I say can be applied not only to physics, but to other academic disciplines as well.
Here are some resources for learning physics (in order of increasing difficulty)
Amateur (little to no math)
A Briefer History of Time by Stephen Hawking
The Grand Design by Stephen Hawking and Leonard Mlodinow
The Elegant Universe by Brian Greene
Cosmos by Carl Sagan
Fearful Symmetry by Anthony Zee
Recruit (some calculus, maybe a DiffEQ here or there)
University Physics by Roger Freedman
Physics (Vol 1 and 2) by Resnick, Halliday, and Krane
Regular (know calculus cold, and have a good handle on DiffEQs)
An Introduction to Mechanics by Kleppner and Kolenkow
Electricity and Magnetism by Purcell
Classical and Statistical Thermodynamics by Ashley Carter
Hardened (all of the “baby maths” should be second nature to you)
Classical Mechanics by Taylor
Introduction to Electrodynamics by Griffiths
Introduction to Quantum Mechanics by Griffiths
Introduction to Elementary Particles by Griffiths
Veteran (you will not survive)
A Modern Approach to Quantum Mechanics by Townsend
Quantum Field Theory in a Nutshell by Anthony Zee
Studies indicating that studying in pairs is ideal:
Hake, R. R. (1998). Interactive-engagement versus traditional methods: A six-thousand-student survey of mechanics test data for introductory physics courses. American journal of Physics, 66, 64.
