Space and The wonders/mysteries of The Universe

By coincidence I just watched Logopolis last night. (Amazing how young Davidson looks now ) Although there's a lot of the computer science in it that is giggle-worthy now, the underlying premise is good. I think Dr Who is at its best when it plants seeds of deeper thoughts throughout the lighthearted adventure romp.

I think a lot of it was giggle-worthy at the time.

Pop over to the Who thread got a Logopolis related question for you best put on the Who thread.

I remember when the deep field image first came out. It was jaw dropping to look at what looked like a field of stars and realize it was actually a field of galaxies.

This is so cool!

WASHINGTON (AP) -- In an announcement that electrified the world of astronomy, scientists said Thursday that they have finally detected gravitational waves, the ripples in the fabric of space-time that Einstein predicted a century ago.

Some scientists likened the breakthrough to the moment Galileo took up a telescope to look at the planets.

The discovery of these waves, created by violent collisions in the universe, excites astronomers because it opens the door to a new way of observing the cosmos. For them, it's like turning a silent movie into a talkie because these waves are the soundtrack of the cosmos.

"Until this moment we had our eyes on the sky and we couldn't hear the music," said Columbia University astrophysicist Szabolcs Marka, a member of the discovery team. "The skies will never be the same."

..............

"It's really comparable only to Galileo taking up the telescope and looking at the planets," said Penn State physics theorist Abhay Ashtekar, who wasn't part of the discovery team. "Our understanding of the heavens changed dramatically."

http://hosted.ap.org/dynamic/stories/U/US_SCI_EINSTEINS_WAVES?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2016-02-11-11-07-00

wow!

Though it's a momentous event to have finally detected them, I don't think anyone was the least bit surprised. General Relativity just works too well for one of its most direct predictions not to have panned out. It shouldn't be called a 'discovery' so much as a long awaited observation, a technical feat.

I only heard about the live feed 45 minutes after it started, waiting for it to get posted so I can watch it from the top.

BBC (of course) has the best explanation of the technical details.

http://www.bbc.com/news/science-environment-35533241

Halfy is probably the only one who even cares, but  the LIGO is basically the old Michelson–Morley experiment from 100 years ago on steroids.  I'm as excited that we're actually making direct measurements on the medium of space-time (whatever that really is) as I am in the "sound" itself.  

{(I've always been a fan of luminiferous ether )}.

I am interested but I don't understand it.

"These waves are streaming to you all the time and if you could see them, you could see back to the first one trillionth of a second of the Big Bang," he said.

It's much like regular water waves. A big object goes bobbing up and down in the ocean, it would send out waves. A big object goes bobbing up and down in space, it sends out space waves.

Now imagine you're a simple little sea creature in Halfy's Sea, and all your life you've taken the Sea and the waves for granted, having never experienced anything else.

Then one day you ask your self "Hey, what makes these things that are bouncing me around all the time? Where do they come from and how did they get here?"

Then, very slowly, a thought at a time, you begin to understand the Sea in a different way.

It changes nothing, and it changes everything!

does this mean they have discovered what gravity looks like?

I really wish the word "discover" would not be used in this conversation.  We've finally detected something that we were 99.9% sure was there.  It's like knowing the inside of your refrigerator goes dark when you close the door, but you've finally rigged up a way so you can see the light going off and on.

It should eventually prove more useful than that, like the fact that the only waves big enough to detect by this method were two black holes falling into each other; being able to 'see' that happening is pretty huge.  I think the cosmological scale explorations that come out of this could be significant.  But detecting the waves themselves I wouldn't say demonstrated anything we didn't already know.

But to answer the question more directly: gravity exists quite happily without waves so long as mass keeps moving at constant speed in straight lines. So what we are seeing isn't gravity itself so much as what happens to gravity when things are accelerated instead of moving at constant velocities.

I assume the fact that we can now 'see' them means that this is the first step to really understanding how things affect them. Like we know the things that gravity does because we can see the effect... but this is the first step to seeing specifically how that effect comes about.

Warp drive next week!!

You have to get into some pretty extreme conditions before plain vanilla general relativity won't tell you precisely what's going on with detectable gravity waves. The early universe would be one of these conditions. But I suppose anything that would make warp drive possible would be pretty extreme.

halfwise wrote:I really wish the word "discover" would not be used in this conversation.  We've finally detected something that we were 99.9% sure was there.  It's like knowing the inside of your refrigerator goes dark when you close the door, but you've finally rigged up a way so you can see the light going off and on.

It should eventually prove more useful than that, like the fact that the only waves big enough to detect by this method were two black holes falling into each other; being able to 'see' that happening is pretty huge.  I think the cosmological scale explorations that come out of this could be significant.  But detecting the waves themselves I wouldn't say demonstrated anything we didn't already know.

I really wish the words ''cosmological scale explorations'' would not be used in this conversation. Because I haven't the foggiest.

Sorry. Talking about things the size of the universe, with questions like how quickly did the early universe expand, when did mass first begin to form into lumps, etc.

halfwise wrote: gravity exists quite happily without waves so long as mass keeps moving at constant speed in straight lines.

... which I think you'll agree is an extremely difficult think to do (unless you're driving across West Texas). And so we need waves.

halfwise wrote:We've finally detected something that we were 99.9% sure was there.  It's like knowing the inside of your refrigerator goes dark when you close the door, but you've finally rigged up a way so you can see the light going off and on.

I'm a little surprised at your lack of enthusiasm Halfy. If I didn't know better, I'd think you were dissing the role of experiments and demonstrability in the Scientific Method.

from the economist

TWO black holes circle one another. Both are about 100km across. One contains 36 times as much mass as the sun; the other, 29. They are locked in an orbital dance, a kilometre or so apart, that is accelerating rapidly to within a whisker of the speed of light. Their event horizons—the spheres defining their points-of-no-return—touch. There is a violent wobble as, for an instant, quintillions upon quintillions of kilograms redistribute themselves. Then there is calm. In under a second, a larger black hole has been born.

It is, however, a hole that is less than the sum of its parts. Three suns’ worth of mass has been turned into energy, in the form of gravitational waves: travelling ripples that stretch and compress space, and thereby all in their path. During the merger’s final fifth of a second, the coalescing holes pumped 50 times more energy into space this way than the whole of the rest of the universe emitted in light, radio waves, X-rays and gamma rays combined.

And then, 1.3 billion years later, in September 2015, on a small planet orbiting an unregarded yellow sun, at facilities known to the planet’s inhabitants as the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO), the faintest slice of those waves was caught. That slice, called GW150914 by LIGO’s masters and announced to the world on February 11th, is the first gravitational wave to be detected directly by human scientists. It is a triumph that has been a century in the making, opening a new window onto the universe and giving researchers a means to peer at hitherto inaccessible happenings, perhaps as far back in time as the Big Bang.

Finger on the pulsar

The idea of gravitational waves emerged from the general theory of relativity, Albert Einstein’s fundamental exposition of gravity, unveiled almost exactly 100 years before GW150914’s discovery. Mass, Einstein realised, deforms the space and time around itself. Gravity is the effect of this, the behaviour of objects dutifully moving along the curves of mass-warped spacetime. It is a simple idea, but the equations that give it mathematical heft are damnably hard to solve. Only by making certain approximations can solutions be found. And one such approximation led Einstein to an odd prediction: any accelerating mass should make ripples in spacetime.

Einstein was not happy with this idea. He would, himself, oscillate like a wave on the topic—rescinding and remaking his case, arguing for such waves and then, after redoing the sums, against them. But, while he and others stretched and squeezed the maths, experimentalists set about trying to catch the putative waves in the act of stretching and squeezing matter.

Their problem was that the expected effect was a transient change in dimensions equivalent to perhaps a thousandth of the width of a proton in an apparatus several kilometres across. Indirect proof of gravitational waves’ existence has been found over the years, most notably by measuring radio emissions from pairs of dead stars called pulsars that are orbiting one another, and deducing from this how the distance between them is shrinking as they broadcast gravitational waves into the cosmos. But the waves themselves proved elusive until the construction of LIGO.

As its name states, LIGO is an interferometer. It works by splitting a laser beam in two, sending the halves to and fro along paths identical in length but set at right angles to one another, and then looking for interference patterns when the halves are recombined (see diagram). If the half-beams’ paths are undisturbed, the waves will arrive at the detector in lock-step. But a passing gravitational wave will alternately stretch and compress the half-beams’ paths. Those half-beams, now out of step, will then interfere with each other at the detector in a way that tells of their experience. The shape of the resulting interference pattern contains all manner of information about the wave’s source, including what masses were involved and how far away it was.

To make absolutely certain that what is seen really is a gravitational wave requires taking great care. First, LIGO is actually two facilities, one in Louisiana and the other in Washington state. Only something which is observed almost, but not quite, simultaneously by both could possibly be a gravitational wave. Secondly, nearly everything in the interferometers’ arms is delicately suspended to isolate it as far as possible from distant seismic rumblings and the vibrations of passing traffic.

Moreover, in order to achieve the required sensitivity, each arm of each interferometer is 4km long and the half-beam in it is bounced 100 times between the mirrors at either end of the arm, to amplify any discrepancy when the half-beams are recombined. Even so, between 2002 when LIGO opened and 2010, when it was closed for upgrades, nary a wave was seen.

Holey moly

Those improvements, including doubling the bulk of the devices’ mirrors, suspending them yet more delicately, and increasing the laser power by a factor of 75, have made Advanced LIGO, as the revamped apparatus is known, four times as sensitive as the previous incarnation. That extra sensitivity paid off almost immediately. Indeed, the system’s operators were still kicking its metaphorical tyres and had yet to begin its official first run when GW150914 turned up, first at the Louisiana site, and about a hundredth of a second later in Washington—a difference which places the outburst somewhere in the sky’s southern hemisphere. Since then, the team have been checking their sums and counting their lucky stars. As they outline in Physical Review Letters, the likelihood that the signal was a fluke is infinitesimal.

When one result comes so quickly, others seem sure to follow—particularly as the four months of data the experiment went on to gather as part of the first official run have yet to be analysed fully. A rough estimate suggests one or two other signals as striking as GW150914 may lie within them.

For gravitational astronomy, this is just the beginning. Soon, LIGO will not be alone. By the end of the year VIRGO, a gravitational-wave observatory in Italy, should join it in its search. Another is under construction in Japan and talks are under way to create a fourth, in India. Most ambitiously, a fifth, orbiting, observatory, the Evolved Laser Interferometer Space Antenna, or e-LISA, is on the cards. The first pieces of apparatus designed to test the idea of e-LISA are already in space.

Together, by jointly forming a telescope that will permit astronomers to pinpoint whence the waves come, these devices will open a new vista on the universe. As technology improves, waves of lower frequency—corresponding to events involving larger masses—will become detectable. Eventually, astronomers should be able to peer at the first 380,000 years after the Big Bang, an epoch of history that remains inaccessible to every other kind of telescope yet designed.

The real prize, though, lies in proving Einstein wrong. For all its prescience, the theory of relativity is known to be incomplete because it is inconsistent with the other great 20th-century theory of physics, quantum mechanics. Many physicists suspect that it is in places where conditions are most extreme—the very places which launch gravitational waves—that the first chinks in relativity’s armour will be found, and with them a glimpse of a more all-embracing theory.

Gravitational waves, of which Einstein remained so uncertain, have provided direct evidence for black holes, about which he was long uncomfortable, and may yet yield a peek at the Big Bang, an event he knew his theory was inadequate to describe. They may now lead to his theory’s unseating. If so, its epitaph will be that in predicting gravitational waves, it predicted the means of its own demise.

Just a couple snips from Wikipedia on LIGO. Things that might be useful.

Direct detection of gravitational waves has long been sought. Their discovery would launch a new branch of astronomy to complement electromagnetic telescopes and neutrino observatories.

Measurable emissions of gravitational waves are expected from binary systems (collisions and coalescences of neutron stars or black holes), supernova explosions of massive stars (which form neutron stars and black holes), accreting neutron stars, rotations of neutron stars with deformed crusts, and the remnants of gravitational radiation created by the birth of the universe. The observatory may, in theory, also observe more exotic hypothetical phenomena, such as gravitational waves caused by oscillating cosmic strings or colliding domain walls.

There turn out to be more of these observatories around the world than I'd thought, and with these new observations you can bet that they're all going to be recalibrating and racing for the next discovery. Exciting times in Astrophysics!

Great article, Figgs!

David:
The detectors would have to improve tremendously to see ordinary orbits going on.  Of course, improvement is what tends to happen with technology.    The big improvement that allowed this to happen was scale, which is expensive.  I don't foresee detection capability improving rapidly. But without pushing it too far we should see a some large events of interest.

I'm not dissing the role of experiments, just saying the focus (pushed by the media and even the scientists themselves) was that this was a new discovery.  It's not, it's a nifty technique which is finally working.  It could pay off big, eventually, but I think it's down the road a ways because what allowed this to happen was just pushing up the scale incrementally until we could finally see something.

I've been up on the peaks of plenty of mountains: the sense of accomplishment is always tempered by the amount of arduous persistent effort that had to be put in, and the fact that reaching the top is usually a preordained conclusion.  Sometimes you get nice views, but you hardly feel like jumping around in excitement once you reach the top.  More like quiet satisfaction.

Of course! A little discretion is important when you're standing on mountaintops (either figuratively or literally).And that satisfaction is also usually tempered with the knowledge that you've still got to get your ass back home somehow.

I'm still feeling a bit elated by the news, and seeing that there are bigger and better instruments being built in India as we speak. It feels to me right now like a new dawn of information about the cosmos comparable to the advent of radio-telescopy or the Hubble space telescope.

So I AM jumping up and down..