Astronomy & Space Exploration

MajorTom said:
You'd think an astronaut would be paid more than that.
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I think the salary is just to be a candidate, not all who have trained to be an astronaut will go to space. Plus looking at the link of benefits NASA provides its a pretty attractive job vacancy.
 
I kind of understand what this is and what's proven but what I can't get my head around is what implications this has?

If we can be sure it's a gravitational wave and not something else because it's signature matches existing models then havent we just confirmed an expectation rather than opened up a whole new field of understanding?

Or is this a case of it being proven allowing for more investment and research in detecting these waves?
 
einstein1_7.jpg
 
That Einstein guy was quite bright wasn't he? Outstanding, and of course credit to everyone who preceded and succeeded him.
 
If you love science but are a bit of a layman like me, here's a nice explanation from Reddit of how significant this discovery could be:

If Einstein is right, gravitational waves would travel outward from (for instance) two black holes circling each other just like the ripples in a pond. When they come to Earth and pass through the detectors, a signal can tell us not only that the gravitational wave has been found, but it can also tell us lots of information about the gravitational wave!

As you track what the gravitational waves look like over a (very) short amount of time, you can tell what kind of event caused them, like if it was two black holes colliding or a violent supernova... along with other details, like what the mass of these stars/black holes would have been!

This discovery could usher in an awesome new era of astronomy. BEFORE we start detecting gravitational waves, looking out at the universe is like watching an orchestra without any sound! When our detectors start making regular observations of this stuff, it will be like turning on our ears to the symphony of the cosmos!
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Smores said:
I kind of understand what this is and what's proven but what I can't get my head around is what implications this has?

If we can be sure it's a gravitational wave and not something else because it's signature matches existing models then havent we just confirmed an expectation rather than opened up a whole new field of understanding?

Or is this a case of it being proven allowing for more investment and research in detecting these waves?
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Prior to this, Astronomy depends on EM waves to observe space objects and events. Kind of like static images. This adds a dynamic effect, being able to distinguish events by differences in their gravitational wave characteristics.
 
A good write-up here:

Advance Thoughts on LIGO
Posted on February 11, 2016 | 11 Comments
Scarcely a hundred years after Einstein revealed the equations for his theory of gravity (“General Relativity”) on November 25th, 1915, the world today awaits an announcement from the LIGO experiment, where the G in LIGO stands for Gravity. (The full acronym stands for “Laser Interferometer Gravitational Wave Observatory.”) As you’ve surely heard, the widely reported rumors are that at some point in the last few months, LIGO, recently upgraded to its “Advanced” version, finally observed gravitational waves — ripples in the fabric of space (more accurately, of space-time). These waves, which can make the length of LIGO shorter and longer by an incredibly tiny amount, seem to have come from the violent merger of two black holes, each with a mass [rest-mass!] dozens of times larger than the Sun. Their coalescence occurred long long ago (billions of years) in a galaxy far far away (a good fraction of the distance across the visible part of the universe), but the ripples from the event arrived at Earth just weeks ago. For a brief moment, it is rumored, they shook LIGO hard enough to be convincingly observed.

For today’s purposes, let me assume the rumors are true, and let me assume also that the result to be announced is actually correct. We’ll learn today whether the first assumption is right, but the second assumption may not be certain for some months (remember OPERA’s [NOT] faster-than-light neutrinos and BICEP2’s [PROBABLY NOT] gravitational waves from inflation). We must always keep in mind that any extraordinary scientific result has to be scrutinized and confirmed by experts before scientists will believe it! Discovery is difficult, and a large fraction of such claims — large — fail the test of time.

What the Big News Isn’t
There will be so much press and so many blog articles about this subject that I’m just going to point out a few things that I suspect most articles will miss, especially those in the press.

Most importantly, if LIGO has indeed directly discovered gravitational waves, that’s exciting of course. But it’s by no means the most important story here.

That’s because gravitational waves were already observed indirectly, quite some time ago, in a system of two neutron stars orbiting each other. This pair of neutron stars, discovered by Joe Taylor and his graduate student Russell Hulse, is interesting because one of the neutron stars is a pulsar, an object whose rotation and strong magnetic field combine to make it a natural lighthouse, or more accurately a radiohouse, sending out pulses of radio waves that can be detected at great distances. The time between pulses shifts very slightly as the pulsar moves toward and away from Earth, so the pulsar’s motion around its companion can be carefully monitored. Its orbital period has slowly changed over the decades, and the changes are perfectly consistent with what one would expect if the system were losing energy, emitting it in the form of unseen gravitational waves at just the rate predicted by Einstein’s theory (as shown in this graph.) For their discovery, Hulse and Taylor received the 1993 Nobel Prize. By now, there are other examples of similar pairs of neutron stars, also showing the same type of energy loss in detailed accord with Einstein’s equations.

A bit more subtle (so you can skip this paragraph if you want), but also more general, is that some kind of gravitational waves are inevitable… inevitable, after you accept Einstein’s earlier (1905) equations of special relativity, in which he suggested that the speed of light is a sort of universal speed limit on everything, imposed by the structure of space-time. Sound waves, for instance, exist because the speed of sound is finite; if it were infinite, a vibrating guitar string would make the whole atmosphere wiggle back and forth in sync with the guitar string. Similarly, since effects of gravity must travel at a finite speed, the gravitational effects of orbiting objects must create waves. The only question is the specific properties those waves might have.

No one, therefore, should be surprised that gravitational waves exist, or that they travel at the universal speed limit, just like electromagnetic waves (including visible light, radio waves, etc.) No one should even be surprised that the waves LIGO is (perhaps) detecting have properties predicted by Einstein’s specific equations for gravity; if they were different in a dramatic way, the Hulse-Taylor neutron stars would have behaved differently than expected.

Furthermore, no one should be surprised if waves from a black hole merger have been observed by the Advanced LIGO experiment. This experiment was designed from the beginning, decades ago, so that it could hardly fail to discover gravitational waves from the coalescence of two black holes, two neutron stars, or one of each. We know these mergers happen, and the experts were very confident that Advanced LIGO could find them. The really serious questions were: (a) would Advanced LIGO work as advertised? (b) if it worked, how soon would it make its first discovery? and (c) would the discovery agree in detail with expectations from Einstein’s equations?

Big News In Scientific Technology
So the first big story is that Advanced LIGO WORKS! This experiment represents one of the greatest technological achievements in human history. Congratulations are due to the designers, builders, and operators of this experiment — and to the National Science Foundation of the United States, which is LIGO’s largest funding source. U.S. taxpayers, who on average each contributed a few cents per year over the past two-plus decades, can be proud. And because of the new engineering and technology that were required to make Advanced LIGO functional, I suspect that, over the long run, taxpayers will get a positive financial return on their investment. That’s in addition of course to a vast scientific return.

Advanced LIGO is not even in its final form; further improvements are in the works. Currently, Advanced LIGO consists of two detectors located 2000 miles (3000 kilometers) apart. Each detector consists of two “arms” a few miles (kilometers) long, oriented at right angles, and the lengths of the arms are continuously compared. This is done using exceptionally stable lasers reflecting off exceptionally perfect mirrors, and requiring use of sophisticated tricks for mitigating all sorts of normal vibrations and even effects of quantum “jitter” from the Heisenberg uncertainty principle. With these tools, Advanced LIGO can detect when passing gravitational waves change the lengths of LIGO’s arms by … incredibly … less than one part in a billion trillion (1,000,000,000,000,000,000,000). That’s an astoundingly tiny distance: a thousand times smaller than the radius of a proton. (A proton itself is a hundred thousand times smaller, in radius, than an atom. Indeed, LIGO is measuring a distance as small as can be probed by the Large Hadron Collider — albeit with a very very tiny energy, in contrast to the collider.) By any measure, the gravitational experimenters have done something absolutely extraordinary.
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Big News In Gravity
The second big story: from the gravitational waves that LIGO has perhaps seen, we would learn that the merger of two black holes occurs, to a large extent, as Einstein’s theory predicts. The success of this prediction for what the pattern of gravitational waves should be is a far more powerful test of Einstein’s equations than the mere existence of the gravitational waves!

Imagine, if you can… Two city-sized black holes, each with a mass [rest-mass!] tens of times greater than the Sun, and separated by a few tens of miles (tens of kilometers), orbit each other. They circle faster and faster, as often, in their last few seconds, as 100 times per second. They move at a speed that approaches the universal speed limit. This extreme motion creates an ever larger and increasingly rapid vibration in space-time, generating large space-time waves that rush outward into space. Finally the two black holes spiral toward each other, meet, and join together to make a single black hole, larger than the first two and spinning at an incredible rate. It takes a short moment to settle down to its final form, emitting still more gravitational waves.

During this whole process, the total amount of energy emitted in the vibrations of space-time is a few times larger than you’d get if you could take the entire Sun and (magically) extract all of the energy stored in its rest-mass (E=mc²). This is an immense amount of energy, significantly more than emitted in a typical supernova. Indeed, LIGO’s black hole merger may perhaps be the most titanic event ever detected by humans!

This violent dance of darkness involves very strong and complicated warping of space and time. In fact, it wasn’t until 2005 or so that the full calculation of the process, including the actual moment of coalescence, was possible, using highly advanced mathematical techniques and powerful supercomputers!

By contrast, the resulting ripples we get to observe, billions of years later, are much more tame. Traveling far across the cosmos, they have spread out and weakened. Today they create extremely small and rather simple wiggles in space and time. You can learn how to calculate their properties in an advanced university textbook on Einstein’s gravity equations. Not for the faint of heart, but certainly no supercomputers required.

So gravitational waves are the (relatively) easy part. It’s the prediction of the merger’s properties that was the really big challenge, and its success would represent a remarkable achievement by gravitational theorists. And it would provide powerful new tests of whether Einstein’s equations are in any way incomplete in their description of gravity, black holes, space and time.

Big News in Astronomy
The third big story: If today’s rumor is indeed of a real discovery, we are witnessing the birth of an entirely new field of science: gravitational-wave astronomy. This type of astronomy is complementary to the many other methods we have of “looking” at the universe. What’s great about gravitational wave astronomy is that although dramatic events can occur in the universe without leaving a signal visible to the eye, and even without creating any electromagnetic waves at all, nothing violent can happen in the universe without making waves in space-time. Every object creates gravity, through the curvature of space-time, and every object feels gravity too. You can try to hide in the shadows, but there’s no hiding from gravity.

Advanced LIGO may have been rather lucky to observe a two-black-hole merger so early in its life. But we can be optimistic that the early discovery means that black hole mergers will be observed as often as several times a year even with the current version of Advanced LIGO, which will be further improved over the next few years. This in turn would imply that gravitational wave astronomy will soon be a very rich subject, with lots and lots of interesting data to come, even within 2016. We will look back on today as just the beginning.

Although the rumored discovery is of something expected — experts were pretty certain that mergers of black holes of this size happen on a fairly regular basis — gravitational wave astronomy might soon show us something completely unanticipated. Perhaps it will teach us surprising facts about the numbers or properties of black holes, neutron stars, or other massive objects. Perhaps it will help us solve some existing mysteries, such as those of gamma-ray bursts. Or perhaps it will reveal currently unsuspected cataclysmic events that may have occurred somewhere in our universe’s past.

Prizes On Order?
So it’s really not the gravitational waves themselves that we should celebrate, although I suspect that’s what the press will focus on. Scientists already knew that these waves exist, just as they were aware of the existence of atoms, neutrinos, and top quarks long before these objects were directly observed. The historic aspects of today’s announcement would be in the successful operation of Advanced LIGO, in its new way of “seeing” the universe that allows us to observe two black holes becoming one, and in the ability of Einstein’s gravitational equations to predict the complexities of such an astronomical convulsion.

Of course all of this is under the assumptions that the rumors are true, and also that LIGO’s results are confirmed by further observations. Let’s hope that any claims of discovery survive the careful and proper scrutiny to which they will now be subjected. If so, then prizes of the highest level are clearly in store, and will be doled out to quite a few people, experimenters for designing and building LIGO and theorists for predicting what black-hole mergers would look like. As always, though, the only prize that really matters is given by Nature… and the many scientists and engineers who have contributed to Advanced LIGO may have already won.

Enjoy the press conference this morning. I, ironically, will be in the most inaccessible of places: over the Atlantic Ocean. I was invited to speak at a workshop on Large Hadron Collider physics this week, and I’ll just be flying home. I suppose I can wait 12 hours to find out the news… it’s been 44 years since LIGO was proposed

http://profmattstrassler.com/2016/02/11/advance-thoughts-on-ligo/
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I have a copy of Gravitation by MTW. It's a classic text for an introduction to the mathematics and methodology utilized in General Relativity. What a bitch of a subject.
 
Smores said:
I kind of understand what this is and what's proven but what I can't get my head around is what implications this has?

If we can be sure it's a gravitational wave and not something else because it's signature matches existing models then havent we just confirmed an expectation rather than opened up a whole new field of understanding?

Or is this a case of it being proven allowing for more investment and research in detecting these waves?
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Essentially yeah, we now know they exist and have a proven method of detecting them, so bigger and better detectors can be funded and built.

Question for the science folk here - would this enable us to detect what the universe was like before the state that's visible in the CMB?
 
adexkola said:
I have a copy of Gravitation by MTW. It's a classic text for an introduction to the mathematics and methodology utilized in General Relativity. What a bitch of a subject.
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Not the best place to start. :lol:

To have a decent chance of mastering General Relativity, you've got to pick your text carefully. Lambourne, R J A - Relativity, Gravitation and Cosmology is a recent publication which probably introduces the subject as well as it can be done. Not that it's an easy read. GM is just intrinsically difficult.
 
Just to answer my earlier question, as written by the Guardian's liveblog:

Turok says that now we know gravitational waves exist, future gravitational wave observatories will be able to see the signals coming from the big bang itself. He suspects that the technology may be 20-30 years away but one day, he says, we will be able to see the moment of the universe’s formation.

Bring it on!
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Mackerel.

Also amazing that not only were gravitational waves discovered, black holes were directly observed for the first. In binary! From 1.3bn years ago.
 
Based on the details of the signal detected, the LIGO team estimates that the event that generated the gravitational waves occurred 1.3 billion years ago. That's when two black holes, one 29 times the mass of the Sun, the second 36 times, spiraled into each other. When the collision took place, the equivalent of three times the mass of the Sun was converted directly to energy and released in the form of gravitational waves. For a brief fraction of a second, this single event produced more power than the entire rest of the visible Universe combined.
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Ho-Lee Sheeeit.
 
I used to check the sky every clear night with a small telescope back in Portugal, when I moved here I bought a nice and powerful telescope but the skies aren't clear (New Jersey) like in Portugal and I'm too close from 2 major cities with too much light "pollution". Now only if something like a meteorite shower comes by I will use my telescope ( when we had the meteorite shower the damn sky was packed with clouds).
 
50 times greater energy than all the stars in the universe combined? Countless galaxies? Lad is exaggerating a bit, isn't he?
 
Mrs Smoker said:
50 times greater energy than all the stars in the universe combined? Countless galaxies? Lad is exaggerating a bit, isn't he?
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At that particular moment. Mass is being converted into energy, several Suns worth. Bear in mind that our Sun uses its energy up over almost 10bn years. No idea whether the maths stacks up (though multiple scientists have repeated it over the last few days so I presume it's sound), but that's a whole lot of energy.
 
Armand posted a quote above that says "visible universe". That makes more sense to me, as whole universe...that's kinda big.

Still awesome things to think about and feel insignificant.
 
Mrs Smoker said:
Armand posted a quote above that says "visible universe". That makes more sense to me, as whole universe...that's kinda big.

Still awesome things to think about and feel insignificant.
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A lot of the time they're used interchangeably as we don't really know the size of the actual full universe. Observable universe is still around 100bn lightyears in diameter, so still kinda big!
 
Pretty pretty big. :nervous:

Guess in my mind there 'visible universe' was the space we can see with the naked eye. But that's just several thousand stars. This appears to be a completely another level.
 
Mrs Smoker said:
Pretty pretty big. :nervous:

Guess in my mind there 'visible universe' was the space we can see with the naked eye. But that's just several thousand stars. This appears to be a completely another level.
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The size of the visible universe is about 14 billion light years from where you are right now to the edge. They call it the visible universe because light further than this hasn't had a chance to reach us yet because the big bang happened 14 billion years ago. Or thats the way I understand it.
 
RamblingRebel said:
The size of the visible universe is about 14 billion light years from where you are right now to the edge. They call it the visible universe because light further than this hasn't had a chance to reach us yet because the big bang happened 14 billion years ago. Or thats the way I understand it.
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It's actually nearer 50bn. Space expands mind bogglingly quickly.
 
RamblingRebel said:
The size of the visible universe is about 14 billion light years from where you are right now to the edge. They call it the visible universe because light further than this hasn't had a chance to reach us yet because the big bang happened 14 billion years ago. Or thats the way I understand it.
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Much bigger than that. The diameter is around 90b light years.
 
Revan said:
Yes, why not? It started in a point and then got extended in all directions.
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Well, arguably to have a diameter it needs to have a defined centre and not wrap around on itself as some theories suggest it does. Though in terms of the observable universe, where Earth is by definition the centre, you can say it has one.
 
Ubik said:
It's actually nearer 50bn. Space expands mind bogglingly quickly.
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I'm guessing this is the radius?

Revan said:
Much bigger than that. The diameter is around 90b light years.
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I was saying 14billion-ish radius to keep things relatively simple, but yeah 90 billion would be correct coz by the time the first light from 14 billion years ago has reached us that light has since travelled even further away from us.

Can I just ask though. This first light from the very edge of the observable universe...because it is travelling through space is moving away from us at no faster than the speed of light, or is this the bit of sciencey stuff that allows for the fabric of space and time to 'stretch' making the speed of light relative to the viewer?
 
I'm guessing in the past earth was the center of the universe and today the Big Bang was the center of universe, in other words we changed our mentality but at the end we still believe in a center of the universe and in the beginning of times, when we don't fully comprehend what infinite really means, when I read the universe was the size of a grapefruit before the Big Bang, tells me we should focus on studying the stars, galaxies and everything else but the "beginning" of the universe.
 
I hate this gravitational waves stuff because I'm too stupid to comprehend it. I understand it's a big deal and proves Einstein's genius even further, but I really don't know what it all means.

Explain it to me like I'm a 10 year old.
 
RexHamilton said:
I hate this gravitational waves stuff because I'm too stupid to comprehend it. I understand it's a big deal and proves Einstein's genius even further, but I really don't know what it all means.

Explain it to me like I'm a 10 year old.
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When things are big enough, when they move they send out ripples of gravity which warp space slightly ( and i mean really slightly). Like how a boat sends ripples on surface of water out.

Im not 100% sure why this shows einstein to be more of a genius all he did was predict it.

From what i can gather, it changes how we can 'observe' the universe.

Up until now, we could only see things in the universe that are affected by the electromagnetic spectrum: gamma rays, x rays, light waves, infa red, ultraviolet light, radio waves, mocrowaves. Up until recently that was seen as enough, everything is affected by light right? Well, no...

Theres 'matter' in the universe that is not affected by the electromagnetic spectrum (dark matter). So light just goes through it. However, we know that it still has an affect on gravity. So the discovery of gravity waves means when we get good enough we can 'see' dark matter or at least know more about it because it will generate gravitational waves.
 
barros said:
I'm guessing in the past earth was the center of the universe and today the Big Bang was the center of universe, in other words we changed our mentality but at the end we still believe in a center of the universe and in the beginning of times, when we don't fully comprehend what infinite really means, when I read the universe was the size of a grapefruit before the Big Bang, tells me we should focus on studying the stars, galaxies and everything else but the "beginning" of the universe.
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Earth is meaningful as a "centre" of the universe because we can only observe whatever is arriving here through light. That means we have a rather well-defined radius of incoming light around us. So even though we aren't in the absolute centre of the universe we are in the centre of the universe we can observe.
 
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