Gravitational waves - from proposals to observations

in #steemstem8 years ago

The Virgo Interferometer is something spectacular. With two arms 3km in length, it's one of the biggest machines ever made in the history of the world, behind things like LIGO and the LHC. All for science.

But some mysterious figure didn't just come up with it one day and had it approved for construction the next, the journey atop giants' shoulders was long and wrought with complicated maths people like me could never hope to understand.

Today I thought it would be worthwhile putting some time aside to learn a little more about some of the giants who constructed this monolithic structure with the power of their brains - Einstein aside.

Henri Poincaré


Public Domain

A long, long time ago around 240BC, the Greek poet (also mathematician I guess) Eratosthenes decided to shove a stick in the ground in Alexandria, Egypt, and made another man travel to Southern Egypt to shove another stick in the ground there.

By measuring the difference in shadows at the same time of day, he managed to figure out that the earth was round, and how big it was to surprising accuracy of between 1% and 16% (depending on how you measure 'stadia'), roughly around 44,100 km. Quite an accomplishment given we now know it's about 40,075.017km. Give or take.

Though Eratosthenes managed to prove something he could not possibly see for himself - indeed we could not possibly see until space agencies took us into the Great Void Above - Poincaré decided he could essentially take this one step further do the same thing with the entire Universe.

We call this the Poincaré Conjecture, for which he is most famous. You can Learn more about it in this video, but in short it took over a century of people coming up with false proofs for his outlandish idea to inevitably become proven by an eccentric, isolated Russian, Grisha Perelman who went on to turn down a million dollars and the equivalent of a nobel prize, the Fields Medal, before fading back into obscurity.

But Poincaré is also responsible for first proposing the existence of gravitational waves, 11 years before Einstein made his predictions, something that both LIGO and VIRGO slipped up on in a publication a few years back, instead attributing to Einstein.

By building on the theory of special relativity and the Lorentz Transformations, he concluded that gravitation must emanate outwards, at the speed of light rather than instantaneously, as waves do - in a similar fashion to Electromagnetism.

A decade later, Einstein incorporated these ideas into his paper Approximative Integration of the Field Equations of Gravitation.

References

Sur la dynamique de l'électron | Henri Poincaré Predicted The Existence Of Gravitational Waves As Early As June 5, 1905

Oliver Heaviside


Public Domain

So Poincaré was the first, except... he wasn't really.

Oliver Heaviside was a rather brilliant Englishman, having self-taught electrical engineering, mathematics, physics and more.

He was no mathematical amateur either. After stumbling upon Maxwell's paper Treatise on Electricity and Magnetism. and describing it as:

Great, greater and greatest, with prodigious possibilities in its power

He buckled down for the better part of a decade studying Maxwell's work with passion until finally following his own path.

In 1893, a full 23 years before Einstein's predictions, Heaviside made some pretty bold deductions. In his paper A Gravitational and
Electromagnetic analogy
, he wanted to align gravitational energy with the likes of electric and magnetic energies a la Maxwell.

Upon considering velocity of propagation as finite, he continued his comparisons and concluded, roughly, the existence of gravitational waves.

References

The Prediction of Gravitational Waves in 1893 | The Secret History of Gravitational Waves

Pierre-Simon Laplace

Ok, so the idea that gravitation traveled at finite speeds was hardly new, with Laplace discussing this idea as far back as 1770. Numerous others had also touched on this, but the ideas, far from refined, required Poincaré and eventually Einstein to truly hammer home the details.

In fact, it was Einstein alone who made the tangible, accurate predictions alongside details of their expected properties, such as how the waves wilil exhibit stretching in one direction and compressing in the other, much like sound waves and light, but way more complicated regarding the manipulation of space-time.

But where's the proof?

Introducing:

Kip Thorne, Barry Barish & Rainer Weiss

In 2017, these three lads won the nobel prize in Physics for the 'decisive contributions to the LIGO detector and the observation of gravitational waves'!

In 1984, the three co-founded the LIGO project in the US, and suddenly those elusive gravitational waves were about to lose their hiding spot. All of Einstein/Poincaré/Heaviside/Laplace's work was falling into place.

The workload was not a light one. Kip Thorne, for example, had to develop the mathematics in order to even be able to analyse the results should the experiment work, he had to analyse engineering designs that couldn't conceptually be tested beforehand, he helped identify wave sources, provide theoretical support, he designed the beam tubes, and invented 'quantum nondemolition designs' and ways to reduce thermoelastic noise.

All in a day's work!


Kip Thorne Credit: A. T. Service - CC BY-SA 3.0

On top of that, he even managed to squeeze in enough time to be the science advisor for Christopher Nolan's 'Interstellar' - a movie that depicts the most scientifically accurate black hole known to date - a full 2 years before signatures of gravitational waves were officially detected.

References

nobelprize.org | Kip Thorne

And here we are now, in 2018 (that is also the beginning of what is coined the gastrophysics era), a world where gravitational waves are a definitely real thing that we can almost touch with our bare hands. Ok, not quite. Detecting one of these waves is the equivalent of noticing the Milky Way stretched out about the length of your keyboard's delete key.

But we can touch the machines capable of doing that at say, oh I don't know, the SteemSTEM-Utopian.io meetup in Italy in September!

Sort:  

Nobel laureat Kip Thorne consulting on Interstellar: Proof that geeky scientists can be cool :P

Scientists are always cool ^^

Great read!

Eratosthenes is actually considered as the father of Geodesy, I talk about him and the process followed for the calculation of the Earth's circumference in this Geodesy post I uploaded 5 months ago. (It's too old, so nobody can accuse me of trying to promote my work here :P).

And here we are now, in 2018 (that is also the beginning of what is coined the gastrophysics era), a world where gravitational waves are a definitely real thing that we can almost touch with our bare hands.

So basically if gravitational waves do exist, then we could possibly invent some sort of device that generates and/or manipulates gravity waves in order to distort the fabric of space-time, making interstellar travel possible?

Fascinating times! I'm very excited about the future!

So basically if gravitational waves do exist, then we could possibly invent some sort of device that generates and/or manipulates gravity waves in order to distort the fabric of space-time, making interstellar travel possible?

Gravitational waves exist. This has been proved last year. Any accelerating mass generates gravitational waves. However, one needs something very very heavy to get waves that are observables. In other words, black holes or neutron stars.

Since we are not even far to only imagining producing a neutron star or a black hole, the answer to your question is 'no way' (at least for now) :D

Theoretically proven based on Einstine's relativity study but scientifically not for there is no existing particle that can travel the same speed as the light even if it is increasingly accelerating. Well, not unless if it is a blackhole. :)

It is more than just theoretical. I must disagree and confirm that black holes have somehow been experimentally observed.

The only way to generate the wave we observed comes from the collision of two black holes (or neutron stars). We have no other astrophysical object in our catalogue capable to be responsible for such observations. Of course, the observation could be due to something we don't know, but which mimics a black hole very very well (then let's call it a black hole in the meantime).

Concerning the speed of light, the neutron star events proved that gravitational waves travel at the speed of light, like photons and gluons by the way.

What about photons? They are zero mass particles that travel at the speed of light.

It represents a light so basically, it has similar features same as light and not more than the light can travel at 3x10^8 m/s. And also, particle must have mass enough to produce a certain amount of attracting force as it travels way beyond the speed of light. An object increases its mass as it travels a huge amount of speed say for example greater than light. Thus if it increases its mass then the force of attraction between anybody and that certain body increases.

The flaw here is that gravity does not involve only mass but also energy. In this way, photons are sensitive to gravity as well.

I guess I answered everywhere by now :)

Thanks for taking the time to clarify things!

It is always a pleasure! :)

I've no idea if it will become manipulable, but the results have a lot of other applications, such as being able to see how black holes form, seeing things before they emit light, seeing into supernovae, and general transformation of our understanding of the Universe. Hopefully.

Henri poincare once said Science is built up of facts, as a house is built of stones, but an accumulation of facts is no more a science than a heap of stones in a house. The scientist does not study nature because it is useful, he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing and if nature were not worth knowing life would not be worth living....Henri is a great man, nice post

Posted using Partiko Android

I tend to only partly agree with that. Scientists study nature because they want to understand how it works. That's it, IMO.

I'm in awe with the ancient Greek mathematician's ability to deduce the shape of the earth using nothing but some sticks, shadows and geometry. Now, all the trolls in the internet and offline claiming the earth is flat should be transported back to the cavemen era :)

Egyptians momies are hurt... believe me :D

i love science . Very helpful... thanks :)

good post sir

Very interesting post.

so this post clarified briefly what's the origin of gravitational waves and how they are found. but i'm impressed by Henri Poincare tht he managed to find out that earth is round just by measuring the shadows of sthe tick. He was quite a geneius

Eratosthenes, not Poincare =P I just used this historical example to simplify poincare's much more complex idea, as he tried to figure out the shape of the Universe (at least, this was an implication of its outcome)

Great Men of history indeed. Unfortunately, some of them were robbed of the recognition of their onerous contributions. History isn't fair at times.

@eurogee of @euronation and @steemstem communities

I disagree here. Poincare and Heaviside proposed gravitational waves. Einstein predicted them through within his theory. No one stole anything. Moreover, in science, one always relies on the work of others. There is no way to restart always from scratch.

This is a very convincing point of view. I was about agreeing with @eurogee when I saw this. Thanks for the clarification.

@sciencetech
STEM contributor

Thanks for seeing also my point :)

This is so true. No one generates his/her ideas out of a vacuum.

It is more like a giant pyramid of mathematicians and scientists with the most recent ones one top being supported by the earlier ones below.



Which one are you? :D

History is written by the winners, after all

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