**Jan 12, 2021 05:39 AM (This post was last modified: Jan 12, 2021 05:40 AM by C C.)**

**C C**
There's no way to Measure the Speed of Light in a Single Direction

https://www.universetoday.com/149554/the...direction/

EXCERPT: . . . But several physicists have pointed out that while relativity assumes the vacuum speed of light is a universal constant, it also shows the speed can never be measured. Specifically, relativity forbids you from measuring the time it takes light to travel from point A to point B. To measure the speed of light in one direction, you’d need a synchronized stopwatch at each end, but relative motion affects the rate of your clocks relative to the speed of light. You can’t synchronize them without knowing the speed of light, which you can’t know without measuring. What you can do is use a single stopwatch to measure the round trip time from A to B back to A, and this is what every measurement of the speed of light does.

Since all the round-trip speed of light measurements give a constant result, you might figure you can just divide the time by two and call it a day. This is exactly what Einstein did. He assumed the time there and back was the same. Our experiments agree with that assumption, but they also agree with the idea that the speed of light coming towards us is ten times faster than its speed going away from us. Light doesn’t have to have a constant speed in all directions, it just has to have a constant “average” round-trip speed. Relativity still holds if the speed of light is anisotropic... (MORE - details)

A “no math” (but seven-part) guide to modern quantum mechanics

https://arstechnica.com/science/2021/01/...mechanics/

INTRO: Some technical revolutions enter with drama and a bang, others wriggle unnoticed into our everyday experience. And one of the quietest revolutions of our current century has been the entry of quantum mechanics into our everyday technology. It used to be that quantum effects were confined to physics laboratories and delicate experiments. But modern technology increasingly relies on quantum mechanics for its basic operation, and the importance of quantum effects will only grow in the decades to come.

As such, the time has come to explain quantum mechanics—or, at least, its basics. My goal in this seven(!)-part series is to introduce the strangely beautiful effects of quantum mechanics and explain how they’ve come to influence our everyday world. Each edition will include a guided hike into the quantum mechanical woods where we’ll admire a new—and often surprising—effect. Once back at the visitor’s center, we’ll talk about how that effect is used in technology and where to look for it.

Embarking on a series of quantum mechanics articles can be intimidating. Few things trigger more fear than “a simple introduction to physics.” But to the intrepid and brave, I will make a few promises before we start:

The mathematics of consciousness

https://backreaction.blogspot.com/2021/0...sness.html

INTRO: Physicists like to think they can explain everything, and that, of course, includes human consciousness. And so in the last few decades they’ve set out to demystify the brain by throwing math at the problem. Last year, I attended a workshop on the mathematics of consciousness in Oxford. Back then, when we still met other people in real life, remember that?

I find it to be a really interesting development that physicists take on consciousness, and so, today I want to talk a little about ideas for how consciousness can be described mathematically, how that’s going so far, and what we can hope to learn from it in the future. The currently most popular mathematical approach to consciousness is integrated information theory, IIT for short. It was put forward by a neurologist, Giulio Tononi, in two thousand and four... (MORE)

https://www.youtube.com/watch?v=efVBUDnD_no

https://www.universetoday.com/149554/the...direction/

EXCERPT: . . . But several physicists have pointed out that while relativity assumes the vacuum speed of light is a universal constant, it also shows the speed can never be measured. Specifically, relativity forbids you from measuring the time it takes light to travel from point A to point B. To measure the speed of light in one direction, you’d need a synchronized stopwatch at each end, but relative motion affects the rate of your clocks relative to the speed of light. You can’t synchronize them without knowing the speed of light, which you can’t know without measuring. What you can do is use a single stopwatch to measure the round trip time from A to B back to A, and this is what every measurement of the speed of light does.

Since all the round-trip speed of light measurements give a constant result, you might figure you can just divide the time by two and call it a day. This is exactly what Einstein did. He assumed the time there and back was the same. Our experiments agree with that assumption, but they also agree with the idea that the speed of light coming towards us is ten times faster than its speed going away from us. Light doesn’t have to have a constant speed in all directions, it just has to have a constant “average” round-trip speed. Relativity still holds if the speed of light is anisotropic... (MORE - details)

A “no math” (but seven-part) guide to modern quantum mechanics

https://arstechnica.com/science/2021/01/...mechanics/

INTRO: Some technical revolutions enter with drama and a bang, others wriggle unnoticed into our everyday experience. And one of the quietest revolutions of our current century has been the entry of quantum mechanics into our everyday technology. It used to be that quantum effects were confined to physics laboratories and delicate experiments. But modern technology increasingly relies on quantum mechanics for its basic operation, and the importance of quantum effects will only grow in the decades to come.

As such, the time has come to explain quantum mechanics—or, at least, its basics. My goal in this seven(!)-part series is to introduce the strangely beautiful effects of quantum mechanics and explain how they’ve come to influence our everyday world. Each edition will include a guided hike into the quantum mechanical woods where we’ll admire a new—and often surprising—effect. Once back at the visitor’s center, we’ll talk about how that effect is used in technology and where to look for it.

Embarking on a series of quantum mechanics articles can be intimidating. Few things trigger more fear than “a simple introduction to physics.” But to the intrepid and brave, I will make a few promises before we start:

- No math. While the language of quantum mechanics is written using fairly advanced math, I don’t believe one has to read Japanese before you can appreciate Japanese art. Our journey will focus on the beauty of the quantum world.

- No philosophy. There has been a fascination with the ‘meaning’ of quantum mechanics, but we’ll leave that discussion for pints down at the pub. Here we will focus on what we see.

- Everything we encounter will be experimentally verified. While some of the results might be surprising, nothing we encounter will be speculative.

The mathematics of consciousness

https://backreaction.blogspot.com/2021/0...sness.html

INTRO: Physicists like to think they can explain everything, and that, of course, includes human consciousness. And so in the last few decades they’ve set out to demystify the brain by throwing math at the problem. Last year, I attended a workshop on the mathematics of consciousness in Oxford. Back then, when we still met other people in real life, remember that?

I find it to be a really interesting development that physicists take on consciousness, and so, today I want to talk a little about ideas for how consciousness can be described mathematically, how that’s going so far, and what we can hope to learn from it in the future. The currently most popular mathematical approach to consciousness is integrated information theory, IIT for short. It was put forward by a neurologist, Giulio Tononi, in two thousand and four... (MORE)