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Physicists are interested in the big questions like “Where did we come from?” and “What is all this stuff?”. But the answers to some of these questions, just lead to more questions.

Hosted by: Michael Aranda.

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https://www.space.com/25075-cosmic-inflation-universe-expansion-big-bang-infographic.html.
Why we need inflation: https://www.space.com/42202-why-we-need-cosmic-inflation.html.
https://www.space.com/42261-how-did-inflation-happen-anyway.html.
Inflation review: https://arxiv.org/pdf/hep-ph/0304257.pdf.
Evidence for inflation https://www.forbes.com/sites/startswithabang/2019/05/11/ask-ethan-how-well-has-cosmic-inflation-been-verified/?sh=7ad0a2891d07
GW detection: https://iopscience.iop.org/article/10.1088/1475-7516/2021/01/012
Penrose cyclic cosmology: https://aip.scitation.org/doi/abs/10.1063/1.4727997?journalCode=apc.

New evidence for cyclic universe claimed by Roger Penrose and colleagues

Fine-tuning:
Fundamental constants: https://www.forbes.com/sites/ethansiegel/2015/08/22/it-takes-26-fundamental-constants-to-give-us-our-universe-but-they-still-dont-give-everything/#4118be154b86
Fine-tuning 1: https://www.symmetrymagazine.org/article/fine-tuning-versus-naturalness.
Fine-tuning 2: https://www.pbs.org/wgbh/nova/article/scientific-approaches-to-the-fine-tuning-problem/
Fine-tuning 3: https://www.forbes.com/sites/startswithabang/2019/04/05/fine-tuning-really-is-a-problem-in-physics/
Fine-tuning 4: https://plato.stanford.edu/entries/fine-tuning/
Fine-tuning 5: https://books.google.co.uk/books/about/Just_Six_Numbers.html?id=4XPhAgAAQBAJ&printsec=frontcover&source=kp_read_button&hl=en&redir_esc=y#v=onepage&q&f=false.
Fine-tuning 6: https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/finetuning-of-the-universe-for-intelligent-life/222321D5D4B5A4D68A3A97BBE46AEE45
Anthropic principle: https://www.britannica.com/science/anthropic-principle.

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Background videos:
Fundamental forces: https://youtu.be/669QUJrF4u0
Electroweak theory: https://youtu.be/u05VK0pSc7I
Is Big Bang hidden in gravity waves: https://youtu.be/VXr1mzY2GnY
Cosmic Microwave background: https://youtu.be/XcXCrFIivyk.

Errata:
12:26 — Helium-3 has 2 protons and 1 Neutron.

Chapters:
0:00 — How many atoms are there?
1:01 — We don’t know what happened at or before t=0
3:34 — Cosmic inflation.
5:27 — What we do know.
8:29 — How protons and neutrons formed.
10:41 — How charged nucleons formed.
13:47 — How neutral atoms formed.
15:24 — How to learn more about atoms.

Summary:
Where did the first atom come from? The short answer is the big bang. In the early universe there was an immense amount of energy, The energy condensed, atoms formed. But there’s a lot more that happened, which will be explained here.

The big bang is often thought of as the theory explaining the beginning. but it’s not. We don’t know when the universe actually started, or whether it did. Our best theory of the early universe is the standard model of cosmology, We can only go back to one Planck time, about 10^−43 seconds. This is the smallest unit of time that can theoretically exist according to quantum mechanics. We don’t know what came before this.

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Arguments for fine tuning: Physics has many constants like the charge of the electron, the gravitational constant, Planck’s constant. If any of their values were different, our universe, as we know it, would not be the same, and life would probably not exist.
0:00 — Defining fine tuning.
2:20 — Gravitational constant.
3:59 — Electromagnetic Force.
5:02 — Strong force.
6:13 — Weak force.
7:51 — Philosophical Arguments against fine tuning.
9:36 — Scientific arguments against fine tuning.
11:59 — Sentient puddle.
13:29 — Does fine tuning need an agent.
15:14 — Louse on the tail a lion.
Some say that it could not have occurred by chance, that there must be some agent, like a god that set up the constants to enable life.

Let’s just look at the constants associated with the different forces. Gravity: If the gravitational constant was too small, gravity would be too weak, and planets wouldn’t form. If it was too large, then stars like the sun would burn up too fast.

Electromagnetism: The electromagnetic force is responsible for the distance at which electrons orbits in atoms. If the force was weaker, the atomic size would increase because electrons would be further away from the nucleus. This could impact chemistry, as it would change the strength of chemical bonds.

A higher constant would lead to cooler stars and a lower constant would lead to hotter stars. If the constant was bigger, atoms larger than hydrogen atoms could not form and stars may never ignite, because protons may not have been able to overcome the coulomb barrier to fuse in the first place.

Strong force: If the strong coupling constant were lower, then you wouldn’t have stable heavy atoms as it would not be enough to overcome proton-proton repulsion. If the strong nuclear force was only 1% weaker for example, atoms crucial for life like oxygen, carbon and nitrogen may not form in sufficient quantities.

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Chapters.
0:00 — You are a time traveler.
2:32 — Spacetime & light cone review.
6:15 — Flat Spacetime equations.
7:03 — Schwarzschild radius, metric.
8:42 — Light cone near a black hole.
10:15 — How to escape black hole.
10:39 — Kerr-Newman metric.
11:34 — How to remove the event horizon.
11:50 — What is a naked singularity.
12:20 — How to travel back in time.
13:26 — Problems.

Summary.
Time travel is nothing special. You’re time traveling right now into the future. Relativity theory shows higher gravity and higher speed can slow time down enough to allow you to potentially travel far into the future. But can you travel back in time to the past?

In this video I first do a quick review of light cones, world lines, events, light like curves, time-like curves, and space-like curves in this video so that you can understand the rest of the video.

A space like-world line means that the object has to travel faster than light. But moving anything to the speed of light requires an infinite amount of energy to accelerate. So this is not possible.

Going faster than the speed of light can create scenarios that allow you to travel back in time. But since this is not physically possible, we need to figure out a clever manipulation of space time. This means we have to solve Einstein’s equations of General relativity.

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Signup for your FREE TRIAL to The GREAT COURSES PLUS here: http://ow.ly/5KMw30qK17T. Until 350 years ago, there was a distinction between what people saw on earth and what they saw in the sky. There did not seem to be any connection.

Then Isaac Newton in 1,687 showed that planets move due to the same forces we experience here on earth. If things could be explained with mathematics, to many people this called into question the need for a God.

But in the late 20th century, arguments for God were resurrected. The standard model of particle physics and general relativity is accurate. But there are constants in these equations that do not have an explanation. They have to be measured. Many of them seem to be very fine tuned.

Scientists point out for example, the mass of a neutrino is 2X10^-37kg. It has been shown that if this mass was off by just one decimal point, life would not exist because if the mass was too high, the additional gravity would cause the universe to collapse. If the mass was too low, galaxies could not form because the universe would have expanded too fast.

On closer examination, it has some problems. The argument exaggerates the idea of fine tuning by using misleading units of measurement, to make fine tuning seem much more unlikely than it may be. The mass of neutrinos is expressed in Kg. Using kilograms to measure something this small is the equivalent of measuring a person’s height in light years. A better measurement for the neutrino would be electron volts or picograms.

Another point is that most of the constants could not really be any arbitrary number. They are going to hover around some value close to what they actually are. The value of the mass of a neutrino could not be the mass of a bowling ball. Such massive particles with the property of a neutrino could not have been created during the Big Bang.

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Is it an egg, a blimp or a bullet? Whatever you might want to call the shape of the Otto Celera 500L, it’s one that catches the eye. It looks like no other plane out there, and for a good reason: unique aerodynamics.

The shape of the Celera is designed to drastically reduce drag by allowing air to flow very smoothly over the surface of the plane. That makes the aircraft less power-hungry, which means it burns less fuel.

“This gets us four to five times the efficiency of other turboprop aircraft, and seven to eight times the efficiency of jet aircraft,” says William Otto Jr., CEO of Otto Aviation.

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Even after 30 months in space, The Planetary Society’s LightSail 2 mission continues to successfully “sail on sunbeams” demonstrating solar sail technology in Earth orbit. The mission is providing hard data for future missions that hope to employ solar sails to explore the cosmos.

LightSail 2, a small cubesat, launched in June 2019 on a SpaceX

Commonly known as SpaceX, Space Exploration Technologies Corp. is a private American aerospace manufacturer and space transportation services company that was founded by Elon Musk in 2002. Headquartered in Hawthorne, California, the company designs, manufactures, and launches advanced rockets and spacecraft.

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Octopuses, crabs and lobsters will receive greater welfare protection in UK law following an LSE report which demonstrates that there is strong scientific evidence that these animals have the capacity to experience pain, distress or harm.

The UK government has today confirmed that that the scope of the Animal Welfare (Sentience) Bill will be extended to all decapod crustaceans and cephalopod molluscs.

This move follows the findings of a government-commissioned independent review led by Dr Jonathan Birch. The review drew on over 300 existing scientific studies to evaluate evidence of sentience in cephalopods (including octopuses, squid and cuttlefish) and decapods (including crabs, lobsters and crayfish).

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The vehicle was able to fire off its own missile over the South China Sea while travelling at five times the speed of sound.

China tested a hypersonic vehicle in July that was able to fire off its own missile over the South China Sea while travelling at five times the speed of sound, in a physics-defying display of technology that no other country has demonstrated, according to a new report.

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