Friday, April 30, 2021

036 The Erickson Report for April 22 to May 5, Page Four: And Another Thing

036 The Erickson Report for April 22 to May 5, Page Four: And Another Thing

We're going to take a break now for something I keep meaning to make more common but never seem too. We call it And Another Thing, where we step aside from politics and social commentary to look at some science thing that I think is cool.

This time we start with the first picture to the right. It's a recently enhanced photo made from an original plate taken in May 1919 in Sobral, Brazil. It is, as I expect you guessed, of a solar eclipse.

It has some added color so that nice solar prominence can be easily seen. The original, of course was in black and white. But that's not the interesting part.

The second photo zooms into the lower right corner of the picture. Notice the two bright spots circled in red.

What's so special about these spots? Well, as I'm sure you knew, they are stars. What's important is that they shouldn't be there. Or more exactly, they shouldn't be where they are.

Which brings us to Albert Einstein and his Theory of Relativity. Relativity has the reputation of being extremely difficult to understand and indeed the mathematics involved in having a deep understanding of the theory are quite advanced and well beyond certainly my comprehension. But the concepts of the theory can be understood by any reasonably intelligent person. You may have to focus a bit, but you can understand it.

The basic concept to understand is that Einstein realized that we do not exist in a universe of three dimensions of space and a separate one of time, but a universe of four-dimensional spacetime. That space and time are interwoven, that each affects the other, and neither is absolute but can be distorted or warped - specifically, warped by the presence of mass.

His original Theory of Relativity, which later became the Special Theory of Relativity, described the effects of that insight in what are called non-accelerated frames of reference. That is, with objects moving in a straight line at a constant speed; more technically, objects moving at a constant velocity, so their acceleration is zero. Thus, a non-accelerated frame of reference

It became the Special Theory of Relativity because Einstein later expanded it to include accelerated frames of reference, where objects are changing their speed or direction of motion or both. That was the General Theory of Relativity - which served as Einstein's theory of gravity.

Newton described gravity as an attractive force between two objects, with the strength dependent on their masses and how far apart they are. Einstein, however, described gravity as the result of the warping of spacetime by mass. So anything traveling close enough to a massive enough object would have its path bent by the warping of spacetime. That means anything - even light.

Okay. The eclipse of 1919 was an excellent opportunity to test Einstein's idea. During an eclipse, astronomers can observe stars appearing close to the Sun, which otherwise would be lost in the glare. By comparing their positions with observations of those same stars at times when they are visible in the night sky, the amount by which their light has been deflected by the Sun can be measured.

Two expeditions went out, one to Sobral and one to the island of Principe off the west coast of Africa. There are great dramatic stories of the scientific struggles and frustrations involved, including the Principe expedition waking up to thunderstorms and getting only occasional glimpses of the Sun in breaks in the clouds and multiple plates in Sobral being ruined because it was hot enough to warp the lenses in the camera. But they managed to get enough plates to get results.

Now, Newton also predicted that light would have its path be deflected by gravity - but Einstein predicted more than twice the effect. Newton's theory predicted a deflection of 0.8 arc-seconds. Einstein predicted 1.8. An arc-second is 1/60 of an arc-minute, which is 1/60 of a degree, which is 1/360 of a complete circle. So yeah, an arc-second is small, but the size is unimportant, it's how closely prediction matches actual measurements.

The stars in this photo are deflected by just under 2 arc-seconds. The ones from Principe were measured at 1.6 arc-seconds. One a little above Einstein's predictions, one a little below, but both in line with it and far removed from Newton's.
These results, that is, were the first observational proofs of the General Theory of Relativity.

They made Einstein a figure known worldwide and other predictions of his theory, such as black holes, have been subjects of both scientific study and sci-fi ever since.

Which brings me to the third image. Almost exactly 100 years later, in April 2019, a worldwide collaboration of scientists produced this, the first ever image of, the first direct observational evidence of, a black hole.

With a mass roughly equal to 6.5 million of our Suns, this supermassive black hole is located in the galaxy M87, some 55 million light years away from Earth. By the way, M87 just means Messier 87, or number 87 in the Messier catalog of deep-sky objects.

Recall you can't see the black hole itself; the gravitational strength of a black hole is so great that anything passing the event horizon, even light, can't escape. Which is why it's called a black hole. As matter is drawn into the black hole, it swirls around, spiraling in, becoming extremely hot and becoming what scientists call luminous, giving off electromagnetic energy such as radio waves and X-rays. That's what you're seeing here.

The image was obtained using something called the Event Horizon Telescope, which linked together eight ground-based radio telescopes, effectively turning the Earth into one giant virtual radio telescope and creating a resolution sharp enough to focus on an orange on the surface of the Moon.

It also provided an extraordinary test of Einstein's theory of gravity and its underlying notions of space and time. One hundred years later and we are still getting observation evidence related to the General Theory of Relativity - and Einstein is still right.

As a footnote to this, what gave me a hook to raise this now, is that at he end of March of this year, 2021, the team that did the black hole picture followed it up with the final one here. Those visible swirls are in effect an image of the structure of the magnetic field in the event horizon of that black hole.

The image is enabling astrophysicists to analyze the nature and strength of that magnetic field and through that provide important insights into the still-mysterious nature of black holes. Because yes, they are still in a number of ways mysterious and even as more and more is learned there is a considerable amount still unknown about them.
And I think that is really cool.

No comments:

// I Support The Occupy Movement : banner and script by @jeffcouturer / (v1.2) document.write('
I support the OCCUPY movement
');function occupySwap(whichState){if(whichState==1){document.getElementById('occupyimg').src=""}else{document.getElementById('occupyimg').src=""}} document.write('');