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--------------------------------- 2614 - SPACE - can space be warped?
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- In everyday life, “frame-dragging” is both undetectable and inconsequential, as the effect is so tiny. Detecting the frame-dragging caused by the entire Earth’s spin requires satellites such as Gravity Probe B, and the detection of angular changes in gyroscopes equivalent to just one degree every 100,000 years. (See Review 588 about Gravity Probe B)
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- Luckily for us, the Universe contains many naturally occurring gravitational laboratories where physicists can observe Einstein’s predictions at work in exquisite detail. The motion of stars would have perplexed astronomers in Newton’s time, as they clearly move in a warped space-time, and require Einstein’s general theory of relativity to explain their trajectories.
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- The white dwarf-pulsar binary system orbits its white dwarf companion every 4.8 hours. The white dwarf’s rapid rotation drags space-time around it, causing the entire orbit to tumble in space.
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- General relativity is the foundation of modern gravitational theory. It explains the precise motion of the stars, planets and satellites, and even the flow of time. One of its lesser-known predictions is that spinning bodies drag space-time around with them. The faster an object spins and the more massive it is, the more powerful the drag.
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- One type of object for which this is very relevant is called a white dwarf. These are the leftover cores from dead stars that were once several times the mass of our Sun, but have since exhausted their hydrogen fuel. What remains is similar in size to Earth but hundreds of thousands of times more massive. White dwarfs can also spin very quickly, rotating every minute, rather than every 24 hours like Earth does.
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- The frame-dragging caused by such a white dwarf would be roughly 100 million times as powerful as Earth’s. Astronomers observe them via orbiting stars called pulsars.
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- A radio telescope discovered a unique stellar pair consisting of a white dwarf (about the size of Earth but about 300,000 times heavier) and a radio pulsar (just the size of a city but 400,000 times heavier).
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- Compared with white dwarfs, pulsars are in another league altogether. They are made not of conventional atoms, but of neutrons packed tightly together, making them incredibly dense. This pulsar spins 150 times every minute.
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- This means that, 150 times every minute, a “lighthouse beam” of radio waves emitted by this pulsar sweeps past our vantage point here on Earth. We can use this to map the path of the pulsar as it orbits the white dwarf, by timing when its pulse arrives at our telescope and knowing the speed of light. This method revealed that the two stars orbit one another in less than 5 hours.
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- This pair of stars is an ideal gravitational laboratory. Since 2001 we have tracked their orbits several times a year to observe a multitude of Einstein’s gravitational effects.
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- The mapping of the evolution of orbits is ridiculously precise. The pulsar rotates 2.5387230404 times per second, and that its orbit is tumbling in space. This means the plane of its orbit is not fixed, but instead is slowly rotating.
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- When pairs of stars are born, the most massive one dies first, often creating a white dwarf. Before the second star dies it transfers matter to its white dwarf companion. A disk forms as this material falls towards the white dwarf, and over the course of tens of thousands of years it revs up the white dwarf, until it rotates every few minutes.
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- A white dwarf is spun-up by the transfer of matter from its companion. Material at the surface of the swollen star falls towards the white dwarf and forms a disk of material traveling so quickly it causes the star to spin rapidly.
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- The second star can then detonate in a supernova, leaving behind a pulsar. This rapidly spinning white dwarf star drags space-time around with it, making the pulsar’s orbital plane tilt as it is dragged along.
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- This fortuitous situation is the laboratory for astronomers to study Einstein’s laws of physics. The studies use his math to predict what astronomers should observe. And, his math is accurately predicting what we see. Amazing!
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- Einstein himself thought many of his predictions about space and time would never be observable. But the past few years have seen a revolution in extreme astrophysics, including the discovery of gravitational waves and the imaging of a black hole shadow with a worldwide network of telescopes.
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- Other Reviews about space:
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- 2568 - SPACE - is anything but empty. The whole Universe is mostly “space”. We tend to say “ empty space” But, the Universe is anything but empty. Space is full of amazing stuff. The stars use their nuclear furnaces to produce all of the 90 natural elements from hydrogen to iron.
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- 2522 - SPACE - curved or flat? The concept of curved space and time is challenging. Most of the concept relies on mathematics to provide the descriptions, but, math is another language that has to be learned first. It is impossible to leave space. It holds everything. Like time keeps everything from happening all at once, space keeps everything from being in the same place.
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- 2475 - SPACE - is not nothing. . Space is what separates things? What else is it? We continue to discover what space is and we are far from finished. The whole Earth can be reduced to the size of a sugar cube if you remove all the “space” between the atoms. Of course, the sugar cube would still weigh 59,700 trillion, trillion tons after removing all that weightless space. - The size of space depends on how fast you are moving. Space is much todo about nothing.
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- 2404 - the vacuum of space.
- 2279 - inventions for earthlings.
- 2252 - what did we learn in space?
- 2243 - what is space really?
- 2224 - The year 2018 in space exploration.
- 2049 - the expanding space.
- 2029 - dust is outer space.
- 1986 - space is what separates things. Time is what keeps everything from happening all at once.
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- 1831 - from Blackholes to empty space. From Blackholes to Empty Space? The center of a Blackhole is expected to be infinite density. The space between Blackholes is supposed to be an empty vacuum. Both offer mysteries yet to be discovered.
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- 1790 - Space ant time must change as we approach the speed of light. Explains why space and time must change in order to adhere to the Theory of Relativity.
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- 1773 - The size of space depends on you fast you are moving.
- 1407 - Space is in constant motion.
- 1241 - at the smallest levels things remain connected even though they are separated in space.
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- 588 - Gravity probe B
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- February 10, 2020 2614
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--------------------- Tuesday, February 11, 2020 --------------------
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