What's the Point?

No discovery is significant without having its applications, and the discovery of gravitational wave detection is no different. With the recency of the discovery, not all is known on what we will learn from this, but there are some expectations that the consensus of the scientific community has. Most of these involve either the confirmation of ideas not yet confirmed by physical evidence or gaining a better understanding of certain phenomena. If gravitational waves can teach us even a fraction of what we learned about the universe from electromagnetic radiation, it would be revolutionary.

In this post, I will be discussing the applications of gravitational waves in studying black holes and neutron stars, and looking at how these waves may tell us about the origins of our universe. 

Black Holes and Neutron Stars

As amazing as it may sound, the existence of black holes still to this day remains strictly theoretical. For as often as they make headlines in our culture you would think that we already know so much about them, but we really don't. While odds are their existence is a near certainty, the properties of them remain under harsh scrutiny. The behaviors and possible existence of a black hole's event horizon or singularity is still not understood. This phenomenon has stayed hidden for so long thanks to it's ability to swallow-up light with an extremely intense gravitational pull. While light can not escape from black holes, gravitational waves are amplified, not hindered by their gravitational pull meaning they could potentially reach Earth.

The nature of neutron stars is quite similar to that of black holes. While some light can escape their gravitational pull, the light they emit is too small to analyze like we would for other stars. Because these stars are often responsible for the birth of black holes, much could be learned about both if we were able to analyze their gravitational waves.

The Big Bang

Cosmic Microwave Background

Another significant application that the gravitational wave detectors have is the ability to look back at the origins of our universe. Referred to as the Cosmic Microwave Background (CMB), scientists we're able to map-out the early behaviors of the universe by looking at low-frequency microwaves from the Big Bang. The CMB map has gotten us a good jump-start on what the Big Bang was like, but when trying to look past a certain point it offers us no information at all.

Because the behavior of the universe was so chaotic before that point, we are only able to look as far back as 380,000 years after the Big Bang. Being in an incredibly energy-dense state, all light waves would either be scattered or absorbed by plasma. As I talked about in my previous blog post, matter does not affect gravitational waves, so the high energy-dense state didn't affect the transmission of these waves. This means there are gravitational waves traveling through space right now that originated from the birth of the universe. Some even believe that they can be used to look at before the Big Bang as well. According to famed theoretical astrophysicist Michio Kaku, "if we have space-based gravity detectors orbiting the Earth or sun, and we detect radiation from the incident of the big bang, we could run the video tape backwards and therefore get insight into what happened before the big bang." This idea is still very controversial though.


In conclusion, the detection of gravitational waves will allow us to look into some of the most extreme environments of our universe. With strong associations to black holes and the Big Bang, we may be able to learn priceless information on these very mysterious events in the cosmos.





Sources:

Pandian, Jagadheep D. "What Is a Singularity?" Ask an Astronomer. N.p., 27 June 2015. Web. 27 Apr. 2016. <http://curious.astro.cornell.edu/physics/86-the-universe/black-holes-and-quasars/general-questions/441-what-is-a-singularity-beginner>. 

"Event Horizon." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 27 Apr. 2016. <http://www.britannica.com/topic/event-horizon-black-hole>.  

"How Can Gravitational Waves Help Mankind?" Web log post. Blogger. N.p., 26 Jan. 2012. Web. 27 Apr. 2016. <http://stuver.blogspot.com/2012/01/q-how-can-gravitational-waves-help.html>.  

Sainato, Michael. "Michio Kaku Explains Gravitational Waves as ‘Baby Pictures of the Big Bang’." Observer. N.p., 16 Feb. 2016. Web. 27 Apr. 2016. <http://observer.com/2016/02/michio-kaku-explains-gravitational-waves-as-baby-pictures-of-the-big-bang/>.  

Cosmic Microwave Background Seen by Planck. Digital image. ESA. N.p., 21 Mar. 2013. Web. 28 Apr. 2016. <http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2013/03/planck_cmb/12583930-4-eng-GB/Planck_CMB.jpg>.  

The New-Age Telescope

Conquering a feat long thought to be impossible, the scientists and engineers of the Laser Interferometer Gravitational-Wave Observatory (LIGO) have a lot to be proud of. Their recent detection of gravitational waves for the first time ever has opened up many doors for astrophysics as a whole. Because the effects the waves create are so minimal, a very precise and well-designed piece of equipment was needed to be built, and that's exactly what the people at LIGO accomplished. By exploiting certain properties of the waves they were able to sense when these waves were passing through their apparatus.

For my post today I will be discussing:

• The main characteristic of gravitational waves that scientists use to detect them
• How the Laser Interferometer Gravitational-Wave Observatory functions

 

Behavior of Gravitational Waves 

A ring of particles influenced by a gravitational wave

Like mentioned previously, Gravitational waves have the ability to pass through matter unchanged. This means that the waves are same when they reach us as they are when they left the source of the waves. However, even though the wave is not altered by the matter, the matter is in fact affected by the wave. When a gravitational wave passes through a plane, that plane is periodically stretched and squeezed. This process is illustrated in the graphic to the right. It is this behavior that allows us to analyze and detect them.

Laser Interferometer Gravitational-Waves Observer

 

So how would one exploit this property? Well in order to detect when these waves pass through you would need to measure when the distance between two points in space has been stretched. Sounds fairly simple right? Well it's actually quite difficult. Intuitively, when you want to measure the distance between two objects you could just use some sort of ruler. The problem with applying this idea is that even though the distance between the points is stretched, so is the "ruler", and to an observer nothing will seem to have changed. To measure this type of change we must use something that remains constant no matter the outside influences: the speed of light in a vacuum. With a system of lasers and mirrors, LIGO was able to use the constant speed of light to their benefit.

The LIGO observatory is made up of two vacuum-sealed tunnels, each four kilometers long and positioned so they are perpendicular with one another. A laser is split down each tunnel, and reflected back and forth many times between mirrors until recombining at a light detector. The apparatus is set up such that when the tunnels are at their normal unstretched length, the waves will recombine and cancel each other out. However when a gravitational wave passes through, the tunnels are stretched and compressed and the distance each beam of light travels will be different. This change in distance will make the beams no longer cancel each other out when recombining.

One of the biggest problems with these machines is isolating the system so that no outside sources might create false readings. Because the system is making such precise measurements, some of the most light vibrations from the outside world can cause these problems. Vibrations were initially to much of a problem to make accurate readings at LIGO, but with improvements made to their equipment in 2010 it is no longer an issue. As a fail-safe to ensure that the detector didn't make a false detection, two different observatories were built in locations far away from one another. Having two different locations also helps us to trace where the wave originated from.

If you're interested in learning more, Brian Greene joined the Late Show with Stephen Colbert to do an entertaining, hands-on experiment for how these observatories function.

Thanks to the amazing pieces of equipment at LIGO we were able to detect gravitational waves for the first time ever. However, just because we have come up with with the first functional design does not mean the innovation stops here. Similar to how we have improved on the telescope since it's invention, scientists are continuing to look for better ways of designing gravitational wave detectors. What the future holds for these detectors is unknown but certainly exciting.

Sources:

Schilling, Govert. "Gravitational Waves Hit Prime Time." Sky & Telescope (2015): 26-31. Ebsco Academic Premier. Web. 27 Apr. 2016.

Harry, Gregory M. "Advanced LIGO: The next Generation of Gravitational Wave Detectors." Classical and Quantum Gravity 27.8 (2010): n. pag. Web. 27 Apr. 2016. 

Daw, Ed. A ring of particles influenced by gravitational wave. Digital image. PHYS ORG. N.p., 11 Feb. 2016. Web. 27 Apr. 2016. <http://phys.org/news/2016-02-ligo.html>. 

"Gravitational Waves Hit The Late Show." YouTube. YouTube, 25 Feb. 2016. Web. 27 Apr. 2016. <https://www.youtube.com/watch?v=ajZojAwfEbs>. 

How It's Made: Gravitational Waves

Surprise! Who would have guessed it; Einstein gets it right again. Thanks to the amazing scientists and engineers at the Laser Interferometer Gravitational-Wave Observatory (LIGO), this past September we were able to make the first ever direct-detection of gravitational waves. The existence of these waves is something that has been expected since Einstein's theory of general relativity became a commonly accepted idea. In fact it was the only remaining item yet to be confirmed from his famous theory. However this discovery holds significance beyond just the confirmation of his ideas. In time, we may soon be able to see the universe in a completely new way.

 For this post, I will be discussing the origins of these waves as well as some of their properties that makes this discovery so significant. However, to truly understand the nature of gravitational waves, you must first have a complete understanding of what gravity is.

Ripples on a Pond

I'm sure you have all heard the story before; Isaac Newton sits in his garden under his favorite apple tree, pondering the behaviors of the universe, when suddenly it hits him (the apple, that is). "There must be a force of attraction between all objects with mass, otherwise this apple would have no reason to fall downwards!" Now obviously the validity of the story is questionable, but the significance remains the same.  Isaac Newton's discovery on the forces of gravity was monumental in the world of physics. However there was one question that Newton was never able to find the answer to: Where does this force originate from?

2-D representation of gravity

Enter Albert Einstein, roughly 300 years later, with the answer to one of the world's most puzzling questions. Einstein proposed that gravity was not just some mystical force of attraction between two objects, but the reaction of mass to the warp of space-time. This concept intimidates many, but visualizing is the key to understanding in this case. Take the Earth and the Moon for example. The Earth, being a massive object, will create a distortion in space-time. Because of this distortion, or curvature as some people refer to it, the moon has a tendency to fall towards the earth and doesn't travel forever in one direction. This can be said the same for why the Earth revolves around the sun, or why the sun revolves around the center of the galaxy. As the late John Wheeler once described it, "'Matter tells space how to curve. Space tells matter how to move."

A simulation of the two neutron stars revolving around one another

So where do these gravitational waves come into play you ask? Well it's important to realize that gravity and gravitational waves are not one and the same. While gravitational waves are a consequence of gravity, they are two completely different phenomenon. Gravitational waves are made when you take massive objects that are warping space-time, and you begin to accelerate them. In the case of the September 15th discovery at the LIGO observatory, scientists detected a pair of stars rapidly revolving around each other until combining together. Because of the extremely high density and speed of rotation for these stars, intense gravitational waves were created and emanated towards Earth. As of right now only highly energetic events like these are able to be detected, but as the equipment advances, more and more cosmic events will be able to be observed.

A Light in the Dark

Nearly all the information we have gained of other celestial bodies, up until now, has been through observing its electromagnetic radiation (light). If it gave off an intense enough electromagnetic wave, then it can be analyzed to further understand its properties. In many ways, gravitational waves share the same tendencies as electromagnetic radiation. Both carry some amount of energy. Both travel at the speed of light. Both carry information about the source of their existence. How the two differ is what makes gravitational waves so important though.

As electromagnetic radiation travels through space-time, the intensity of the radiation decreases at a pretty significant rate. Also, obstacles that may block our view limit the amount of light that can be analyzed. For example during different seasons we would not be able to look at the stars blocked by our sun. Gravitational waves travel through space-time with a constant intensity, and are able to pass through matter completely unchanged. This combination of characteristics means that at any point in time, no matter the position of Earth's rotation or the distance between the source and the Earth, we will be able to receive it's message. Metaphorically speaking, astrophysicists have always used their eyes when looking for information, but now they are finally learning how to use their "ears".

Sources:

Redd, Nola Taylor. "Einstein's Theory of General Relativity." Space.com. N.p., 11 Feb. 2016. Web. 21 Apr. 2016. <http://www.space.com/17661-theory-general-relativity.html>. 

Cho, Adrian. "Gravitational Waves, Einstein's Ripples in Spacetime, Spotted for First Time." Science. N.p., 10 Feb. 2016. Web. 21 Apr. 2016. <http://www.sciencemag.org/news/2016/02/gravitational-waves-einsteins-ripples-spacetime-spotted-first-time>.

"Gravitational Waves Detected 100 Years After Einstein's Prediction." LIGO Lab. N.p., 11 Feb. 2016. Web. 21 Apr. 2016. <https://www.ligo.caltech.edu/news/ligo20160211>. 

Warped grid Earth and moon. Digital image. Science Blogs. N.p., n.d. Web. 21 Apr. 2016. <http://scienceblogs.com/startswithabang/files/2013/01/Warped_grid-earth-moon1-590x442.jpg>.