Hi spacebenders,
Late last year, Lawrence Krauss tweeted the rumblings from within LIGO, that gravitational waves had been found, and that a Paper was pending.
Well, that Paper has now been published, and is undergoing critical analysis as we speak/read.
'Lawrence Krauss Reveals All - Gravitational Waves'
https://youtu.be/KL4dy_LwsAs
But what is it? And what are these 'gravitational waves'?
Are they colloquialisms for the silent applause, delivered by fans at gravy-making championships - the Gravy Invitational waves??
No :-P
So what are they? Well, a friend asked for a layman's explanation of what gravitational waves are, via Facebook, and this is what i said:
[What 'gravitational waves' means is that] even the effects of gravity are affected by the spacetime constant 'c', commonly known as the 'speed of light'. So, if something with mass moves, then it'll take time for something somewhere else to notice. Hence the idea of ripples. If you throw a stone in a lake, it'll take time until a little plastic solider gets hit by a ripple, on the shore.
If two really massive (heavy) things spiral in towards each other and eventually collide, they'll be moving backwards and forwards very quickly, and so any LIGO you happen to have somewhere, will be most able to see the step down/up of gravitational tug as the masses move away/closer, to your position. The ripples are biggest, on the flat metaphorical lake of our cosmos, when the most massive things move about.
But in fact, even these ripples are far too small to observe directly, even coming from black holes, so LIGO has a huge array of mirrors and LASERs instead. Any gravitational wave, passing through, would ripple (distort) the 4km-across laboratory, causing the LASERs to get out of phase.
In the experiment's interferometer setup, the LASERs are made to deliberately destructively interfere, which means the output signal shows nothing at all. Unless the laboratory itself is warped, in which case the light doesn't fully cancel out, and so some light is seen.
And that's how they can find gravitational waves.
Is that all clear now? :-D
I should take this opportunity to correct a nuance in what i wrote two weeks ago - LISA Pathfinder is not actually involved in finding gravitational waves itself - Pathfinder is doing fundamental physics, studying the nature of gravity, under microgravity conditions.
ESA's eLISA (Evolved Laser Interferometer Space Antenna) is to be launched in the 2030s, when Pathfinder's done, and will be doing what LIGO does now, but on a much larger scale - over 5 million kilometres. To notice gravitational waves, you need something a lot bigger than the Pathfinder experiment's tiny craft - you need a huge interferometer.
You can easily look up video demonstrations of how an interferometer works, on the interwebs, including a demo by one of the guys who founded the LIDO experiment itself.
But then, why bother searching for that one, when i've linked it here? The man in the video is Rainer Weiss, who appears in the video below - 'The Announcement...'
The reason that LIDO is an L-shaped laboratory, is to detect gravitational waves, coming from either direction, or some angle in-between. If it were practical to build a third arm, going 4 kilometres up in the air, orthogonal to the ground-based arms, then they probably would have built that too.
LIDO, by the way, stands for the 'LASER Interferometer Gravitational-Wave Observatory' which is currently situated in two sites, in Hanford, Washington, and Livingston, Louisiana, so that results collected by each can be compared.
If they both see the same squiggles on their graphs, then the chances of their observations being a fluke are much, much lower. Use only one LIDO, and you don't know what you're comparing to - the universe, or a truck rolling past the building :-D
I should point out that the Paper in question - this paper - was actually contributed to by LIGO, and VIRGO - two international collaborations involving more than 1000 researchers, employed through funding from the USA's NCS, the UK's STFC, the Max Planck Society of Germany, and the Australian Research Council. Like with the discoveries of CERN, using the LHC, this has been a big project.
In a few years, other sites in Europe, Japan and India are expected to join the search, which will use evidence of gravitational waves to infer the presence of black hole systems, across the universe, and the cosmic machinations that they are involved in, in greater detail.
Another benefit of having more sites, is that they can be used to increase precision of origin calculation. Currently, the position of the black-hole-smashing event that produced these famous gravitational waves, estimated to be in 'the banana' in this diagram - somewhere in the direction of the LMC (Large Magellanic Cloud).
With more interferometer experiments looking from different angles, the location of the gravitational waves' sources can be triangulated with better precision, enabling Physicists to pin-point site of origin with greater precision.
'SFN #153: Gravitational Waves Found!; Close Asteroid Flyby March 5th'
https://youtu.be/DaaChTSJ-gM
The only thing that makes black holes gravitationally wavey, is their mass. All massful objects ripple gravitational waves out into the universe, including you; but black holes are a billion shedloads heavier than you, so they create much more distinct waves.
Theoretically, if an instrument could be developed with sufficient precision, then gravitational waves could be detected, as you waved your hands around.
But that's only in theory. In practice, the waves would be disguised by thermal and kinetic vibrations, so there's probably a practical limit for detection sensitivity. LIGO employs well-developed vibration-dampening systems to minimise these effects.
"LIGO can measure the movement of spacetime, as small as one one-thousandth of the diameter of a proton" - Tony Darnell, in that ^ video up there
That's incredibly precise. And also according to Tony, it's enough to measure a fluctuation, the width of a human hair, at the distance of proxima centauri, four light years away! The precision required to conduct this experiment, is why Einstein thought it would be impossible to test this part of his Theory of Relativity.
So even if you think fundamental discoveries about the universe that spawned us into existence, are somehow an example of profligate waste, you've got to admit that this is at the heights of human achievement, so far.
And that's essentially where discoveries like this come from - the desire to be better. Not just to be better than other humans, but to be a better humanity.
If you'd like to hear more about gravitational waves, then here are these two videos. They run to two-and-a-quarter hours, together, and i've seen both of them, so that's why this week's article is a 'special' :-D
'The Announcement: LIGO detects gravitational waves -- Press Conference'
https://youtu.be/vy5vDtviIz0
'LIGO & Gravitational Waves'
https://youtu.be/YYBLlxMrzN8
In-and-on-or-around-this-date-or-time-of-year:
The 12th of February marks Darwin Day - Charles Darwin's 207th birthday anniversary
http://darwinday.org/
It's not topical, and it's nothing to do with gravitational waves, but i thought i should drop this generalised argument about intelligence in somewhere, so i'll reproduce it here:
"I find the use of the term 'intelligent' is often facile to the point of facetiousness. Is it used to compare person X with person Y, on a particular subject, or mode of thought, according to a well-defined metric? Or is it used to describe someone with a functioning brain, no matter how badly they apply it to some subjects? People often desire an oversimplified and absolute measurement of intelligence, that bears little relation to any particular circumstance, that they might find themselves in. Hence IQ tests. Everyone knows something, and is ignorant of other things - they are all both intelligent and stupid. Referring to the bearers of stupid arguments as intelligent, within the context of the conversation, is exemplary stupidity."
'...but intelligent people believe in God'
https://youtu.be/Y201QzDdzbg
In other news:
'Paracetamol use in pregnancy and infancy linked to child asthma'
http://www.nhs.uk/news/2016/02February/Pages/Paracetamol-use-in-pregnancy-and-infancy-linked-to-child-asthma.aspx
According to the Fail, Sun and Mirror, babies are more likely to develop asthma if their biological mothers took paracetamol (caled 'acetaminophen' to Americans) during pregnancy. Paracetamol is recommended as the most benign analgesic (painkiller) and anti-pyretic (fever suppressant) available, and probably one of the most benign medicines available, full stop. If you're warning people away from paracetamol, you're almost certainly steering them toward greater harm. But what's the source of the claim that paracetamol's associated with asthma, through gestation?
Well, the study in question was actually a publicly-funded Norwegian cohort study, that found that exposure in pregnancy correlated with a 13% higher treatment of asthma, and that direct exposure, before the age of 6 months, correlated with a 29% higher treatment. The 13% figure for pregnancy was barely statistically significant however, so is likely to have been a fluke. The 29% figure for babies, however, is less likely to be a fluke, and according to the researchers, existed regardless of motive for paracetamol consumption, suggesting that it was the paracetamol itself that caused the effect, and not the condition that the paracetamol was taken to treat.
The study itself is open-access, so you can read it all yourself. It looked at 115,000 children, through their parents' post-hoc reports, and used post-diagnosis tests for asthma at 3 and 7 years of age, to try to judge abundance of asthma, in the populations that have been exposed to paracetamol, and those that have not. This was a longitudinal cohort study, so it is very difficult to make conclusions about causation, from a study like this. That's where the newspapers went wrong - overstating the results and understating the uncertainty.
A complication is that paracetamol was most likely to have been taken in cases of respiratory infection and influenza, which means the conclusion that consumption motive was irrelevant, might not be true. Plus, there's no data relating to dose response, which is massively important for inferring from correlations. If paracetamol causes asthma, then babies who've had more paracetamol should become more asthmatic.
In conclusion: although the study certainly suggests a link between asthma and paracetamol, it doesn't mean paracetamol causes asthma, and especially not through pregnancy. Maybe after being born, it could be true, but more study is needed to refine further, and find out whether there really is causation. Even if there is, it might still be better for babies to be given paracetamol than available alternatives, that come with less benefit, or greater cost. Because we don't have an answer yet, more research is necessary.
------------------------------------------------------ contemporary stuff
'The New Ninth Planet - Sixty Symbols'
https://youtu.be/jcJC0a1n1B0
'Rainbow Skink'
https://youtu.be/D9HLzMru5rY
'How many microbes in a kiss?'
https://youtu.be/DDJZvglgTZU
'Bart: How I Put On My Socks'
https://youtu.be/cwOVPzAWtnI
'How to Make Vegan Leather (With a Friend) - {The Kloons}'
https://youtu.be/d28n3MpY5V8
'The Science of Love (Queen Parody) | A Capella Science'
https://youtu.be/dCMDawKCBkk
'CRASH ZOOM - Grave Mistake'
https://youtu.be/TDBeXJXYS4U
'How Anita Sarkeesian spent ~1 MILLION dollars!'
https://youtu.be/TbpCKC5dCPo
------------------------------------------------------ of the weeks
Word Of The Week: interferometer -- a tool used to study waves, usually electromagnetic, in order to learn something about their nature. Interferometry is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, and velocimetry.
Screwball Pseudoscience Article Of The Week: PAMPs cause 'junk' food to be unhealthy - it's nothing to do with all the salt and added sugar. -- So said the Daily Fail, this week, in article that extrapolated even more wildly from a tiny longitudinal study, than in the case of the paracetamol-asthma study! For a start, it involved only 24 healthy men, so what could it say about poor health? Laughable :-D
------------------------------------------------------ non-contemporary stuff
'Cactus Chess'
This game takes a long time to play, as you have to replant the cactuses every move :-D
http://micro.cibermitanios.com.ar/post/138739926305
'The 4 Most Annoying Scientific Inaccuracies in Cinema'
https://youtu.be/yVVnbpKpMiY
'Neil deGrasse Tyson Picks the Most Scientifically Accurate Superhero'
https://youtu.be/OyNQsjMUPfY
.
.
.
No comments:
Post a Comment