gravitational waves

Every Gravitational Wave (chapter 4)

A/N: Hello… guess who’s back? I really have no excuse for just about the longest hiatus ever. I can only say that life has been a mess and writer’s block was even worse. But here I am, FINALLY, with the new chapter. I hope you guys like it after this ridiculously long wait, and I hope you can forgive me <3

Summary: Clarke watched Lexa almost bleed out before her eyes, and it is finally impossible for her to deny her own feelings. But nothing is ever easy. Head over heart is a constant fight, Skaikru is still a problem, and a hidden threat lingers in the shadows. Clarke knows their future is uncertain, everything on the ground is, but she hasn’t abandoned hope yet. Hope for a life about more than just surviving. Hope for that small measure of peace, that everyone seeks, and very few ever find.

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“The Esa animation was created from a computer model of what how the fabric of our universe would change as a result of a titanic collision between black holes”

“What a collision between two black holes would look like if we could see gravitational waves. These elusive waves are ripples in the fabric of space-time which could reveal how the universe was created nearly 14 billion years ago.”

Full video of simulation here

5

There is sound in space, thanks to gravitational waves

“These waves are maddeningly weak, and their effects on the objects in spacetime are stupendously tiny. But if you know how to listen for them — just as the components of a radio know how to listen for those long-frequency light waves — you can detect these signals and hear them just as you’d hear any other sound. With an amplitude and a frequency, they’re no different from any other wave.”

You’ve likely heard that there’s no sound in space; that sound needs a medium to travel through, and in the vacuum of space, there is none. That’s true… up to a point. If you were only a few light years away from a star, stellar remnant, black hole, or even a supernova, you’d have no way to hear, feel, or otherwise directly measure the pressure waves from those objects. But they emit another kind of wave that can be interpreted as sounds, if you listen correctly: gravitational waves. These waves are so powerful, that in the very first event we ever detected, the black hole-black hole merger we saw outshone, in terms of energy, all of the stars in the observable Universe combined. There really is sound in space, as long as you know how to listen for it properly.

Come learn about it, and catch a live event, live-blogged by me, this evening!

Also being a scientist pretty much gives you a free pass to be as eccentric as you want like you’ll be at a conference and it’s like “is that guy wearing socks and sandals and plaid pants???” “Ya but he was on the team that discovered gravitational waves let him be”

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5 Reasons Why The 21st Century Will Be The Best One Ever For Astrophysics

“There’s always a temptation to think that our best days are behind us, and that the most important and revolutionary discoveries have already been made. But if we want to comprehend the biggest questions of all — where our Universe comes from, what it’s truly made of, how it came to be, where it’s headed in the far future, how it will all end — we still have work to do. With unprecedented telescopes in size, range, and sensitivity set to come online, we’re poised to learn more that we’ve ever known before. There’s never a guarantee of victory, but every step we take brings us one step closer to our destination. No matter where that turns out to be, the journey continues to be breathtaking.”

What does the future of astrophysics look like? Have we already made all of the fundamental discoveries we’re going to make? Is the rest just categorization of objects, identification of more examples of what’s already known, and minor refinements of the knowledge we already have? Or are there fundamental discoveries still to come, just waiting for us to reveal them? There are so many big questions still out there, and a great many of them have astrophysical consequences! In addition to new observatories, larger telescopes than ever, and problems like dark matter and the matter/antimatter asymmetry, there are five recent discoveries – within the last generation – that have significant implications for the Universe.

Come take a look at five of them: neutrino mass, the accelerating universe, exoplanets, the Higgs boson, and gravitational waves, and learn what the future holds!

3

New gravitational wave characteristics

Monash researchers have identified a new concept - ‘orphan memory’ - which changes the current thinking around gravitational waves.

The research, by the Monash Centre for Astrophysics, was published recently in Physical Review Letters.

Einstein’s theory of general relativity predicts that cataclysmic cosmic explosions stretch the fabric of spacetime.

The stretching of spacetime is called 'gravitational waves.’

After such an event, spacetime does not return to its original state.
It stays stretched out.

This effect is called 'memory.’

The term 'orphan’ alludes to the fact that the parent wave is not directly detectable.

“These waves could open the way for studying physics currently inaccessible to our technology,” said Monash School of Physics and Astronomy Lecturer, Dr Eric Thrane, one of the authors of the study, together with Lucy McNeill and Dr Paul Lasky.

“This effect, called 'memory’ has yet to be observed,” said Dr Thrane.

Gravitational-wave detectors such as LIGO only 'hear’’ gravitational waves at certain frequencies, explains lead author Lucy McNeill.

“If there are exotic sources of gravitational waves out there, for example, from micro black holes, LIGO would not hear them because they are too high-frequency,” she said.

“But this study shows LIGO can be used to probe the universe for gravitational waves that were once thought to be invisible to it.”

Study co-author Dr Lasky said LIGO won’t be able to see the oscillatory stretching and contracting, but it will be able to detect the memory signature if such objects exist.

The researchers were able to show that high-frequency gravitational waves leave behind a memory that LIGO can detect.

“This realisation means that LIGO may be able to detect sources of gravitational waves that no one thought it could,” said Dr Lasky.

8

How Richard Feynman Convinced The Naysayers 60 Years Ago That Gravitational Waves Are Real

“Just as a pulse of electromagnetic radiation would cause such charges to oscillate, the same would happen in the “gravitational antenna” if a gravitational wave passed through—with the maximum effect occurring if the wave were transverse: at right angles to the stick. Upon the impact of a gravitational wave, one of the masses would accelerate relative to the other, sliding back and forth along the stick. The rubbing movement would generate friction between the free mass and the stick, releasing heat in the process. Therefore the gravitational radiation must convey energy. Otherwise, how else did the energy arise?”

Today, we take the existence of gravitational waves for granted. They were predicted by Einstein almost immediately following the first publication of general relativity, they were indirectly detected decades ago and they’ve been directly detected multiple times by the different LIGO observatories. Yet Einstein and his former student argued, back from the 1930s through the 1950s, that the waves were mere mathematical artifacts, and didn’t physically exist. Oddly enough, it was the non-specialist in general relativity, Richard Feynman, who provided the key way of thinking which resolved the argument. Rather than arguing about the mathematical subtleties of relativity, he approached the problem from a physical perspective, reasoning about how gravitational waves would be able to accelerate “gravitational charges,” a.k.a. masses. The result not only demonstrated that gravitational waves must carry energy, but provided the prototype for the design of LIGO.

Thanks to physicist and historian Paul Halpern, the full story is now available for all to read of how Feynman demonstrated the reality of gravitational waves 60 years ago!

9

Ask Ethan: What Is Spacetime?

“Conceptually, the metric tensor defines how spacetime itself is curved. Its curvature is dependent on the matter, energy and stresses present within it; the contents of your Universe define its spacetime curvature. By the same token, how your Universe is curved tells you how the matter and energy is going to move through it. We like to think that an object in motion will continue in motion: Newton’s first law. We conceptualize that as a straight line, but what curved space tells us is that instead an object in motion continuing in motion follows a geodesic, which is a particularly-curved line that corresponds to unaccelerated motion. Ironically, it’s a geodesic, not necessarily a straight line, that is the shortest distance between two points. This shows up even on cosmic scales, where the curved spacetime due to the presence of extraordinary masses can curve the background light from behind it, sometimes into multiple images.”

Sure, you know what space and time are. If you heard of Einstein and relativity, you might know that they’re not absolute quantities, but that how you experience distances and the ticking of clocks is dependent on your motion through the Universe. But did you also know that the addition of masses and gravitation to the theory didn’t just result in general relativity, but changed the way we viewed the Universe completely? If you told me the positions, momenta and all the other properties of all the matter and energy in the Universe, I could tell you everything thanks to general relativity. I could tell you what the Universe would look like and what its behavior would be at any point in time: past, present or future. I could tell you the birth and fate of the Universe, and I could do it with no uncertainty at all. General relativity might be incredibly complex, but it’s the most powerful classical theory of all.

Come get the incredible answer, complete with a description of the spacetime metric, to the simple question of what is spacetime on this week’s Ask Ethan!

Celestial Wonders- Binary Stars (#1)

The twins of the stellar world are binary star systems.

A binary star is a star system consisting of two stars orbiting around their common center of mass.

When two stars appear close together in the sky as seen from the Earth when viewed through  an optical telescope, the situation is known as an “optical double”.

This means that although the stars are aligned along the same line of sight, they may be at completely different distances from us. This occurs in constellations; however, two stars in the same constellation can also be part of a binary system  


Why study Binary stars ?

Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated.

This also determines an empirical mass-luminosity relationship (MLR) from which the masses of single stars can be estimated.

Also,it is estimated that 75% of the stars in the Milky Way galaxy are not single stars, like the Sun, but multiple star systems, binaries or triplets.


The Brightest star in the sky is a binary.

This is true. Sirius (aka the Dog star)  - the brightest star in the sky is actually a binary star system.

When it was discovered in 1844 by the German astronomer Bessel, the system was classed as an astro-metric binary, because the companion star, Sirius B, was too faint to be seen.

Bessel, who was also a mathematician, determined by calculations that Sirius B existed after observing that the proper of Sirius A (the main star) followed a wavy path in the sky, rather than a uniform path.

Sirius can now be studied as a visual binary because, with improving technology and therefore improved telescopes, Sirius B was able to be seen, although not for 20 years after Bessel had correctly predicted its existence.


Black Holes in a binary system ?

Hell Yeah! The term “binary system” is not used exclusively for star systems, but also for planets, asteroids, and galaxies which rotate around a common center of gravity.

However, this is not a trick question; even in star binaries, the companion can be a black hole.

An example of this is Cygnus X-1.


A binary Black Hole system ?

Definitely! A binary black hole (BBH) is a system consisting of two black holes in close orbit around each other.

In fact the LIGO experiment which confirmed the existence of Gravitational waves was able to acquire its data when two Binary Black Holes Collided and merged into one. This phenomenon sent ripples in the fabric of space-time which we call as a Gravitational Wave.

The Universe is amazing huh?


If you found this interesting, check out:

A Denied stardom status - Jupiter

Black Holes are not so Black (Part 3) - Gravitational Waves

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When black holes collide, the energy of the event generates intense gravitational waves. These waves were predicted by Einstein in his theories, but scientists have only recently been able to detect them experimentally. In this SciCafe, Barnard College professor and astronomer Janna Levin shares her scientific research on the first recordings of a gravitational wave from the collision of two black holes 1.3 billion years ago.

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Gravitational Waves…explained.