[HN Gopher] European plan for gigantic new gravitational wave de...
___________________________________________________________________
European plan for gigantic new gravitational wave detector passes
milestone
Author : rbanffy
Score : 93 points
Date : 2021-07-05 16:21 UTC (6 hours ago)
(HTM) web link (www.sciencemag.org)
(TXT) w3m dump (www.sciencemag.org)
| quattrofan wrote:
| What is the benefit of being able to observe these so far away?
| The article does not provide the justification for the project.
| Hikikomori wrote:
| Just creating these machines moves science and engineering
| forward.
| magicalhippo wrote:
| Primarily it means there are more potential events to observe,
| which again leads to better statistics and hopefully more of
| the interesting events.
|
| Better statistics can help guide us towards a viable theory of
| quantum gravity, as well as improve our understand of what
| happens around black holes and neutron stars.
| pm90 wrote:
| I'm not a scientist but: I believe it provides access to the
| only real "data" on events that actually occurred _very_ large
| distances away. This data is valuable in aiding our
| understanding of the early universe e.g. the big bang theory.
| _Microft wrote:
| It's basic research and has no immediate application for normal
| life if this is what you are wondering about.
|
| For astronomy, it is giving us a completely new way of
| observing the universe. Most other ways were based on different
| ways of observing electromagnetic radiation.
|
| https://en.wikipedia.org/wiki/Basic_research
| wolverine876 wrote:
| The justification is knowledge.
| gremloni wrote:
| Why isn't America doing more to be on the forefront?
| wolverine876 wrote:
| Why does it matter, as long as gravitational wave detectors are
| available and the research is performed? In a purely selfish
| sense, isn't it better if someone else spends their money on
| it?
| polynomial wrote:
| What? And let them have all that delicious gravitational
| knowledge before us?
| [deleted]
| geenew wrote:
| From the article,
|
| "U.S. gravitational wave physicists welcomed the announcement,
| too, as they think it may bolster their plans to build a pair
| of detectors even bigger than the Einstein Telescope in a
| project called Cosmic Explorer."
| ncallaway wrote:
| The LIGO observatory, in the United States (Washington and
| Louisiana) was the first to make gravitational wave detection.
|
| I agree that the US often lets itself fall behind in some areas
| (Superconducting Supercollider!), but gravitational wave
| astronomy is an area where the US is significantly
| participating at the forefront of research.
|
| I hope we continue to invest further!
| est31 wrote:
| Americans in fact have kept investing in gravitational wave
| detectors when everyone else didn't because they thought you'd
| need _way_ more sensitivity to detect anything. This led to the
| first direct observations of gravitational waves happening with
| US built detectors, together with the Nobel prize being awarded
| to three americans.
| brnt wrote:
| Do we know which of the two sites was selected yet?
| ginko wrote:
| Don't these gravitational wave detectors usually come in pairs?
| brnt wrote:
| That would be the European thing to do, true.
| ncallaway wrote:
| Not just a European thing, but also an important science
| thing.
|
| LIGO, which made the first gravitational wave detections,
| is located in the US and also has a pair of detectors (one
| in Hanford Washington; the other in Livingston, Louisiana).
|
| The reason to build in pairs is because the detectors need
| to be _extremely_ sensitive in order to detect gravitation
| waves. Such sensitive detectors can easily pick up all
| kinds of noise from local phenomena (such as a truck
| driving nearby), so having two sites separated by a good
| distance helps rule out local noise. Only signals that are
| replicated across both sites need to be evaluated.
|
| There are other benefits to have multiple detectors, too.
| Having two detectors gives us some ability to determine the
| direction the wave is coming from. More detectors will
| allow us to determine the direction even more precisely.
| emiliobumachar wrote:
| Great explanation, thanks. I'd like to add that the cost
| for two would be much less than twice the cost for one,
| due to the design reuse of all the custom equipment.
| Bombthecat wrote:
| Wouldn't 3 better than? For quorum?
| [deleted]
| petschge wrote:
| They would. But it is harder to get funding for three
| than it is to get funding for two...
| ncallaway wrote:
| If you had infinite resources, sure!
|
| It's a cost benefit analysis (and one I'm not remotely
| equipped to make). My guess is they went with two sites
| because that was the smallest number they could get away
| with while still being able to make detections.
| magicalhippo wrote:
| It should be noted that while LIGO has one detector per site
| in an L shape, the Einsten Telescope (ET) will have three,
| each one in the corner of an equilateral triangle[1]. The
| idea is that this provides enough of a cross-check to rule
| out local sources and glitches.
|
| [1]: https://en.wikipedia.org/wiki/Einstein_Telescope#Current
| _des...
| lnauta wrote:
| This decision will be made next year at the earliest.
|
| Source: I work in one of the physics labs that is pushing ET.
| brnt wrote:
| Hi Lewis, keep me posted ;)
| wolverine876 wrote:
| > the edge of the observable universe, 45 billion light-years
| away
|
| If the universe is 13.x billion years old, how is the edge 45
| billion light years away? Assume we're on an edge (probably not,
| but ...); the radius between us and the center should be <13.x
| billion light years, and then the radius to the far edge would be
| another 13.x billion light years; that seems to total <28 billion
| light years max.
|
| Looking out my window ... definitely doesn't look like 45 billion
| ...
| adenozine wrote:
| For someone who knows more than me: what is space? If it's able
| to "move" in the sense of expanding into existence faster than
| light can travel, what is the composition of it? Is this what
| dark matter is meant to explain? For something to expand faster
| than C means it has to be pushed at least that quicky by some
| other thing or some other force, right?
|
| I have no science background at all, just a few decades of
| sysadmin work. Is there a book I should start with?
| TheOtherHobbes wrote:
| No one knows what space is.
|
| We know there's a thing we call "spacetime", because space
| and time are closely related. And we know some things about
| its properties.
|
| But we know nothing at all about what it's made of, or why it
| has the properties it does.
| Sharlin wrote:
| No need to push anything. Distances between objects (that are
| sufficiently far away from each other) just increase as if
| there's "more space" inserted between them in some sense.
| There's the concept of _spacetime metric_ , a function that's
| sort of a universal measuring stick for distances in the
| universe, and it is "shrinking" (as in there's a parameter
| that varies as a function of time) so that a distance that
| used to be three measuring sticks long is now three point
| one.
| erikpukinskis wrote:
| "A Brief History of Time" by Stephen Hawking is written for
| the average reader and wonderful.
| simonh wrote:
| The acceleration of the expansion of the universe is
| sometimes attributed to "dark energy", but that's a
| placeholder term. We don't actually know what is doing it
| exactly. We can just see that it seems to be happening.
|
| The 'faster than the speed of light' thing is only if you
| measure the rate of divergence of objects at very great
| distances from each other, tens of billions of light years.
| At more local scales, such as between our neighbouring
| galaxies and clusters, the effect is relatively small and
| negligible compared to gravity.
| 317070 wrote:
| You can think of this space as something that tells for every
| point a path passes through, how long the distance of the
| path in that point is. So when I connect A and B with a path,
| and I take the integral of space on that path, I get the
| length of the path I would travel if I go from A to B along
| this path. One step further, the distance from A to B is the
| shortest length of all paths from A to B.
|
| Now if for every point in the universe, we have those numbers
| for each path through that point, we call that a "metric".
| Einsteins laws tell us how those numbers all relate to each
| other and how changing the numbers at one point affects the
| numbers at other points over time. And from those laws, you
| can see that you can have waves within those numbers.
|
| So it is not "something" that is waving, it is space itself,
| the thing that defines distances, the metric, that is waving.
|
| Now the annoying thing is that that means that two points at
| rest with each other, can be at a changing distances from
| each other. What happened is that the space between them was
| waving, changing which path between the points was the
| shortest path, and how long that path was.
| gostsamo wrote:
| Space expands faster than light. Don't forget that C is the max
| speed of stuff in space, not of space itself.
| hanoz wrote:
| Wait, what, so atoms, neutrons, quarks etc. are all growing
| and moving apart at the same rate as the Universe?
| simonh wrote:
| The expansion at a local level is too slow and is
| overwhelmed by the local forces holding these structures
| together. Only at the cosmic scale, where the gravitational
| forces between galaxies and clusters or super-clusters of
| galaxies are very tenuous, the expansion takes over.
| herrkanin wrote:
| The forces that keep atoms, neutrons, quarks etc bound to
| each other is stronger than the force caused by space
| expanding. Therefore, space expanding is mostly observed
| when measuring distance between galaxies.
| wolverine876 wrote:
| And space without stuff creates gravitational waves? How?
| Thanks for the impromptu physics lesson, BTW.
| alpaca128 wrote:
| I'm not an expert, but as far as I understand it the
| universe expanding means space itself is stretching at
| every point. Meaning if something was 1ly away in the past,
| it might be farther away due to that effect. This also
| applies to gravitational waves and anything else inside the
| universe.
| contravariant wrote:
| You need something with mass to generate gravitational
| waves, but those waves themselves can pass through empty
| space without any medium, or rather the empty space itself
| _is_ the medium.
| TeMPOraL wrote:
| Space expands uniformly across all its volume, so the parts
| far away from us also have stuff in it. Some stuff already
| moves away from us faster than light.
| gostsamo wrote:
| When space expands, it carries matter with itself just like
| our dog ran away with my sandwich so many years ago.
| wolverine876 wrote:
| Sorry to be pedantic or if I'm missing the obvious:
|
| The article says: Using gravitational waves we can sense
| what is 45 billion light years (bly, for purposes of this
| post) away. That implies that something(s) at 45 bly once
| did generate gravity waves.
|
| If matter can't move faster than C, and if it has only
| been on the move for 13.x billion years, it must be less
| than 28 bly distant.
|
| I am given to understand that the universe can expand
| faster than C; I presume that the universe must lack
| matter beyond 28 bly. I confess that I'm not sure what
| exactly is expanding.
|
| Therefore, what could be located between 28 and 45 bly
| distant that is generating gravity waves?
|
| One possibility: the matter moves no faster than C
| relative to points in the universe as it stretches, but
| is carried faster than that relative to other parts of
| the universe, like a sandwich.
| Hikikomori wrote:
| If we receive light that is 13b years old the light has
| travelled that distance, but the source of that light is
| now 45bly away from us because the universe expands.
| jliptzin wrote:
| Expansion of space
| simonh wrote:
| What do you think 45 billion ly deep space would look like, to
| the naked eye?
| Sharlin wrote:
| Black.
| pixl97 wrote:
| Yep. If space didn't expand there would be a star or galaxy
| at every point we looked.
| contravariant wrote:
| So not black then.
| wolverine876 wrote:
| We apparently don't know why space looks black. See Olbers'
| Paradox.
|
| https://starchild.gsfc.nasa.gov/docs/StarChild/questions/qu
| e...
| Sharlin wrote:
| Oh, but we do know. It is because the age of the universe
| and the speed of light are both finite. (We knew that
| back in 2002 as well; the page you linked seems to be
| written the way it is mostly for pedagogical reasons.)
| wolverine876 wrote:
| Well I have a citation from NASA for my claim. What do
| you have? :)
|
| I recently read another article saying something similar
| but I personally know nothing about it. It definitely
| looks black to me.
|
| Edit: Looking around, some other credible websites agree
| with you. That would seem to imply that the night sky is
| very slowly getting brighter.
| Sharlin wrote:
| But nowhere does the page make the claim that we don't
| know! It only says that it's not a trivial question, and
| that there was a time that we didn't have a good
| explanation for that. Like we used to not have a good
| explanation for gravity or illnesses or earthquakes or
| what have you. It gives the best explanation that we have
| _which is also overwhelmingly likely to be true given the
| evidence_ but of course there 's never anything that we
| can actually prove in science, so in the interest of
| pedagogy it doesn't outright say that we _know_.
|
| Anyway, as I said, the page is from 2002 and many things
| have happened in cosmology since then. Indeed there _are_
| things that we didn 't know back then but are now pretty
| sure about.
| wolverine876 wrote:
| Like the absence, in the brain, of the grey matter that
| detects humor. :)
| TeMPOraL wrote:
| Something something lots of Olympic-size swimming pools.
| bsd44 wrote:
| Noob here so forgive my ignorance but I thought a light-year
| was a unit for measuring distance, not time.
| Hnrobert42 wrote:
| What are the practical applications of gravitational wave
| research? Or is it purely basic science for now?
| Jabbles wrote:
| No one expects the science to be of practical value, but the
| development of the technology and engineering practices needed
| to perform the science may have many applications elsewhere.
| simonh wrote:
| It has some merit sometimes, but I prefer not to rely on this
| justification. These are incidental benefits at the margins
| at best.
|
| My preferred argument is, if we can spend billions on
| trivialities like carbonated sugar water and computer games,
| as a civilisation we can afford basic science research. It's
| not actually all that expensive in the grand scheme of
| things, and cutting science would not necessarily have any
| impact on funding for the alternative things (world peace,
| feeding the poor, etc) people who complain about such funding
| want. If they want to complain about waste they are picking a
| particularly poor target. A bit of a tangent, as the head
| comment wasn't actually making this complaint.
| JumpCrisscross wrote:
| > _What are the practical applications of gravitational wave
| research?_
|
| Currently, not much. We're Galileo grinding lenses at home.
|
| Theoretically? Everything from a whole new mode of active
| sensing, _e.g._ deep into the Earth and /or Sun, all the way to
| communications. Being able to directly measure gravity also
| lets us do new classes of experiments (not yet, but if we can
| measure more sensitively). We don't know what we don't know
| when it comes to gravity, so that's another pot of potential.
|
| Less fantastically, these are immensely precise instruments.
| The manufacturing methods and know how will almost certainly
| translate to other domains.
| Tbvdv wrote:
| It all leads to better porn. It's like Hertz discovering
| electromagnetic waves in air for the first time. Few years
| later Marconi was transmitting erotica in Morse code across the
| Ocean. So I suspect once we are able to amplify and redirect
| the waves at some specific point say a penis on Mars all kinds
| of possibilities open up.
| sha256kira wrote:
| Whoever you are you made my day, please post more comments on
| HN. For the good of humanity, for the children, for me.
| spyder wrote:
| When all you have is a hammer, everything looks like a thing
| you want to nail...
| rantwasp wrote:
| i don't know what you're on but I want some.
| brnt wrote:
| I don't know of any field that necessitates better noise
| reduction than gravitational wave detection. Seems to me it has
| the potential to spin off tons of researchers/techniques able
| to handle noisy data.
| gostsamo wrote:
| Better measuring macro effects of gravity might help us build
| better model of physics which can enable better quantum theory
| which can provide us with better technologies.
| simonh wrote:
| The several already existing gravitational wave detectors have
| already detected signals believed to come from black hole-black
| hole, black hole-neutron star and neutron star-neutron star
| mergers.
|
| Using the time delta between detecting the same events at
| different detectors around the globe, we have inferred the
| directions the signals are coming from.
|
| The intensity curves of the events tell us details about the
| masses and other characteristics of the colliding object. Also
| over time the distribution of their masses and other
| characteristics will give us information about the populations
| and distribution of these objects, which can help validate our
| theories of star, neutron star, black hole and galaxy
| formation.
| throw0101a wrote:
| It's another type of telescope. In history we first observed
| waves in the visible spectrum, then perhaps infrared, radio,
| microwave, ultraviolet, X-ray, etc.
|
| * https://en.wikipedia.org/wiki/Telescope#By_spectrum
|
| This will allow measurements of another type of wave.
|
| * https://en.wikipedia.org/wiki/Gravitational-wave_astronomy
| wolverine876 wrote:
| If the US and Europe are both working on this, why not combine
| resources and build a bigger and better one?
| amenghra wrote:
| If I had to guess: scientists want different sites to be able
| to cross-validate their findings. Ie there's value in
| redundancy when it comes to fundamental research.
| simonh wrote:
| Indeed, but also the time delta between detecting the same
| event at different detectors around the globe gives us
| directional information.
| Sharlin wrote:
| Because it makes sense to have multiple independent detectors
| for several reasons.
| BurningFrog wrote:
| For this stuff, more detectors, as far apart as possible,
| improve observations ,ore.
| reaperducer wrote:
| So much science happening these days. For some reason seeing
| smart people doing things I couldn't possibly understand makes me
| hopeful.
|
| When I was a kid, a laser was a fantastical machine the size of a
| small house that cost a million dollars. Now they're everywhere
| and cost pennies.
|
| I wonder if the children of today will someday have gravitational
| wave detectors on their keychains and use them to entertain their
| cats the way we do with lasers, and think it's nothing special.
| makerofthings wrote:
| If we build enough of these things, can we combine the data and
| use them to take gravitational photographs?
| snek_case wrote:
| This is more like a microphone than a camera. I don't think you
| could really build a camera out of a large number of
| microphones, but you can detect events and infer their
| direction and distance with good precision.
| 6nf wrote:
| You CAN build a camera out of a large number of microphones
| maxmann wrote:
| https://alphamegachem.com/product/a-php-research-chemical-cr...
| https://alphamegachem.com/product/best-purity-jwh-018-for-sa...
| https://alphamegachem.com/product/buy-2-fma-online/
| https://alphamegachem.com/product/buy-2c-b-online/
| https://alphamegachem.com/product/buy-3-fpm-crystal/
| https://alphamegachem.com/product/buy-am-2201-online/
| https://alphamegachem.com/product/buy-apvp-online/
| https://alphamegachem.com/product/buy-bk-2c-b-powder-crystal...
| https://alphamegachem.com/product/buy-dmt-online/
| https://alphamegachem.com/product/buy-impvp-research-chemica...
| https://alphamegachem.com/product/buy-ketamine-powder/
| https://alphamegachem.com/product/https-alphamegachem-com-pr...
| https://alphamegachem.com/product/https-alphamegachem-com-pr...
| https://alphamegachem.com/product/https-alphamegachem-com-pr...
| https://alphamegachem.com/product/https-alphamegachem-com-pr...
| https://alphamegachem.com/product/https-alphamegachem-com-pr...
| https://alphamegachem.com/product/ethylone-crystal-for-sale/
| https://alphamegachem.com/product/hexen-crystal-for-sale/
| mkoubaa wrote:
| What's the point even. This experiment doesn't test any important
| hypotheses so it's nothing to do with advancing science
| simonh wrote:
| More detections gives us information about the population
| characteristics of various sized black holes and neutron stars.
| We have models for star and galaxy formation that these events
| can validate, which in turn can also tell us about conditions
| in the early universe.
| BurningFrog wrote:
| Only EUR1.9B?
|
| If I was a centi-billionaire, I'd just pay for one.
|
| That should save at least 5 years of bureaucratic process to
| advance this scientific frontier!
___________________________________________________________________
(page generated 2021-07-05 23:01 UTC)