Category: Space

Confirmed: Gravitational Waves are a Thing!

If you dedicate any amount of time to following science these days then you WILL have heard about the recent detection of gravitational waves. Science media truly went mental when the discovery was announced on February 11th, and it’s not surprising when you consider what this means for the fields of physics and astronomy. But before we get started with all that jazz, we should probably look at the specifics regarding what the hell these waves are and how the discovery was made.

What they are is a disturbance in the fabric of space-time, much like how dragging your hand through a still pool of water will produce ripples that follow and spread out from it. Why is this a valid comparison? Well Einstein described the universe as made from a “fabric” hewn from both space and time. This fabric can be pushed and pulled as objects accelerate through it, creating these ripples. A similar distortion is also the cause of gravitational attraction, which is nicely demonstrated in the video below.

Almost any object moving through space can produce gravitational waves provided they are not spherically or cylindrically symmetrical. For example, a supernova will produce some if the mass is ejected asymmetrically, and a spinning star will produce some if it’s lumpy rather than a spherical. Unfortunately, the vast majority of sources produce waves that have dissipated long before they get anywhere near us, with only incredibly massive objects producing some that we have a chance of detecting.

Okay! Now that we have at least some idea of what these gravitational waves are, we can look at who and what detected them. This discovery can be attributed to the great minds and machinery involved in the LIGO experiment, which aims to detect gravitational waves by observing the effect they have on space-time. But how would they do this? Space-time isn’t even something we can see! Well my friends, the answer is very clever indeed.

It all involves a machine known as an Interferometer (Figure 1). This device starts by splitting a single laser beam into two, which then shoot off in lines perpendicular to each other. These beams travel exactly the same distance down long vacuum tubes, bounce off mirrors located at the end, and return. Since both beams have travelled the same distance they will still be alignment when they return to the source. They will then destructively interfere with each other and no light will reach the detector.

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Figure 1: Diagram of a basic Interferometer design. Source: http://www.ligo.org/science/GW-IFO.php

However, a passing gravitational wave, with its space-time distorting powers, can actually change the distance that one of the beams travels.  This would mean they are no longer in alignment when they return to the source and won’t cancel each other out. Some light would therefore be able to reach the detector.

And voila! A gravitational wave has been detected… or has it? Well, it actually has in this case, but the point I’m making here is that this amazing machinery is incredibly sensitive to noise. If a gravitational waves were to pass by, it would only change the beam’s distance by about 1/10000th the width of an atom’s nucleus, which is a size I have trouble comprehending.

To pick up such a teeny-tiny change LIGO has to filter out any and all sources of noise, which can include earthquakes and nearby traffic. In fact, to test the research groups ability to distinguish a genuine gravitational wave from noise, senior members of the team secretly inserted “blind injections” of fake gravitational waves into the data stream. While it does seem a bit cruel, it seems their training paid off.

Now we move on to the understandably common question of why this matters to people who aren’t hardcore science nerds. Well, beyond the fact that this discovery will almost certainly win a Nobel Prize this year and that it confirms the final prediction made by Einstein’s general theory of relativity, it could also have a huge impact on the field of astronomy.

Similar to how we use various electromagnetic wavelengths like visible light, infra-red, and x-rays to study a wide range of things, gravitational waves could act as a new analytical tool. Scientists would listen to these waves to learn more information about the objects producing them, which include black holes, neutron stars, and supernovae.

So, while this discovery won’t exactly change your life, it’s easy to see how big of a discovery this was for the field of physics, giving us both a new way to observe the cosmos and further cementing the theory of relativity. Once again, Einstein has been proven right many decades after his death. That’s a feat that very few people have achieved.

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Where are all the Aliens?

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The Milky Way is a big place. Are we really the only ones here? Source: http://sites.psu.edu/vansonspace/2015/04/10/space-is-the-place/

Are we alone in the Universe? To this day it remains one of the most intriguing questions in Science, and probably one of the most discussed by non-scientists everywhere. It’s likely been around for quite some time, but it wasn’t until 1984 with the birth of the SETI (Search for Extraterrestrial Intelligence) institute that we started making meaningful strides towards finding an answer.

But despite great public visibility and inherent curiosity factor, the institute has been pushed to the edges of scientific research. It has failed to attract any serious funding, and received only small amounts of dedicated observation time on world class telescopes.

Well all that is about to change! Thanks to Russian entrepreneur Yuri Milner and physicist Stephen Hawking, the SETI Institute will receive a total of $100 billion in funding over the next decade. The project is known as “Breakthrough Listen”, and will allow for state-of-the-art radio and optical surveys to take place on some of the world’s best telescopes. The project is actually supposed to start making observations some time this year!

So, now that we have the resources available to do some searching, the next question is – what do we search for? We ideally want to find a planet that shares characteristics with our own. That is, one with a rocky surface, of a similar size, orbiting a similar star, and a surface temperature that can allow for liquid water.

This aspect has not proven to be much of a problem, with observations, primarily from the Kepler Space Telescope, showing that the Milky Way contains around a billion planets that meet these specifications. But once we’ve identified such a planet, how do we go about searching for life?

Well for it to be in any way detectable from a distance, life needs to have evolved to the point where it dominates the planet’s surface chemistry. This will actually change the composition of the atmosphere, creating so-called “biosignatures”. A chemical indication of the presence of life.

An example is an atmosphere of at least 20% O2, since our own planet shows that such a composition can almost entirely be created by biological processes. But there is a very real risk of a false positive with any of these biosignatures, since there is always the possibility of a non-biological source. In the case of O2, the splitting of vaporised H2O by UV radiation could easily create such high levels.

This means that we need to find ways to either back up promising signatures, or identify a false positive. For example, detecting methane (CH4) in the planets atmosphere as well as O2 would significantly strengthen the possibility of a life-based origin. On the other hand, an atmosphere rich in steam would suggest that the splitting of H2O is the most likely source.

But what if we want to be more ambitious? What if we want to, rather than searching for any form of life, jump straight to searching for intelligence? There are a few options available to us here, one of which would be the detection of an intelligent, non-natural radio transmission. This is currently the main aim of the SETI program, and while the risk of a false positive is significantly lower than with biosignatures, it’s not without problems. The main one being that radio communication might be considered archaic by and advanced lifeform, so they might not even be using it.

It would also be possible to search for evidence of energy consumption, a necessity for an advanced civilization that seems impossible to conceal. There are many potential energy sources for a civilization with advanced technology, with nuclear fusion being a likely one. There is also the incredible concept of the “Dyson Sphere”, a megastructure surrounding a star to harvest the energy it emits. In either case the production of waste heat is inevitable, and would produce a detectable mid-infrared (MIR) signal.

But one final problem remains. What if, as so much sci-fi media suggests, biological life is only a brief stage for an evolving intelligence? What if the next logical step is the dominance of artificial, inorganic lifeforms?  If so, we wouldn’t really know where to look. It is likely that they would not be found on a planet, as gravity is only advantageous for emerging biological life, but otherwise a nuisance. They would, however, still need to be close to a power source for energy considerations. A star seems to be the most likely source, so that at least gives us a place to start.

There is also the possibility that such intelligence might be broadcasting a signal in their own attempt to find out if they’re alone in the Universe. But if such an advanced civilization were to do such a thing, it is unlikely that our feeble organic brains would be able to detect or understand it.

So, it looks like this amazing question is no closer to being answered than when the effort first began in 1984, but that’s not really surprising since it’s quite a difficult question. However, given that SETI has just been given a new lease of life, it might have gotten a little bit easier. I hope we’ll be learning a lot about this in the coming decade, and who knows, we might actually find someone.

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Chemical Analysis of Mars from Orbit? But how?!

When I found out that water had been found on Mars my first response was to flail and shout with excitement. But once I had calmed down I started to think; how does one actually go about analysing the surface of another planet without actually being on the surface yourself? It was then that I found out NASA have managed to do all of this using a satellite currently orbiting the red planet at an altitude of 300 km (186 miles)! That’s some pretty impressive tech right there (and I imagine the specs are a well-kept trade secret). The satellite itself is known as the Mars Reconnaissance Orbiter (MRO), and it’s equipped with an analytical tool known as CRISM, or the “Compact Reconnaissance Imaging Spectrometer for Mars” if you’re feeling excessive. This device can detect and measure the wavelengths and intensity of both visible and infrared light that has been reflected or scattered from the martian surface; a technique known as “Reflectance Spectroscopy”.

Reflectance Spectroscopy functions on the principle that when light comes into contact with a material, the chemical bonding and molecular structure will cause some of this light to be absorbed. The exact wavelengths absorbed will vary depending on the type of bonding and the elements involved, and the remaining light will either be scattered or reflected depending on the macro-scale properties of the material, such as shape and size. On Mars, most of these materials seem to be grains of some sort and the potentially complex shape of such a structure can cause the light to be scattered in all sorts of directions. However, some of this light will reach the MRO, and CRISM can then detect and measure which wavelengths have been absorbed based on a decrease in intensity. How they found a way to do all of this FROM ORBIT still mystifies me, but I imagine NASA prefers it that way. This whole process then gives an output known as an “absorption spectrum”, an example of which is shown in Figure 1.

Figure 1: An example of an absorption spectrum showing wavelength (x-axis) and reflectance (y-axis). Source: CRISM website: Link: http://crism.jhuapl.edu/instrument/surface/sees.php

So! What have they actually found on Mars using this technique? Well, they appear to have detected “Aqueous Minerals”, which are chemical structures that form in the presence of water by chemical reaction with the surrounding rock. The exact mineral that will form is determined by many factors, including the temperature, pH, and salt content (salinity) of the environment, as well as the composition of the parent rock. Given that this process takes an extremely long time to occur naturally, it can show where water has been present long enough to cause such a reaction, and can give an excellent indication of what the martian surface was like in the past. For example, chloride and sulfate minerals generally indicate very saline water, as well as suggesting that it was more acidic, whereas phyllosilicates and carbonates suggest less salinity and a more neutral pH. What I find most exciting is that this data can suggest where to begin looking for fossilized evidence of ancient life (if it existed at all). If the past water appears to not be too acidic and the elements for life are present, then it is certainly a possibility.

It seems that Mars just keeps getting more exiting with each new discovery, and all we can do now is wait for next announcement to be made. Here’s hoping it’s evidence of life! Also, speaking of life on Mars, everyone should go see The Martian movie in cinemas now, it’s f**king brilliant!

Sources:

  • The CRISM Website. Link: http://crism.jhuapl.edu/index.php
  • USGS Spectroscopy Lab – About Reflectance Spectroscopy. Link: http://speclab.cr.usgs.gov/aboutrefl.html
  • PBS Newshour. “Mars has flowing rivers of briny water, NASA satellite reveals”. Link: http://www.pbs.org/newshour/rundown/mars-flowing-rivers-briny-water-nasa-satellite-reveals/
  • NASA Mars Reconnaissance Orbiter Website. Link: http://mars.nasa.gov/mro/