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From TV shows I have known that we still get some radio signals of the big bang and they are every where. My question is is the universe expanding so fast that even electromagnetic wave has failed to cross it after big bang?
Or is it possible that there is another dimension that we don't know of? Like the earth is nearly flat and in small portion it's surface can be called 2d. But it possible to go "straight" and come back at the same spot as it is in "3d space". So is it possible that the space is 4d and somehow light has crossed the cosmos several times?
The best estimates at the moment are that the Universe is "flat". By that we mean that a pair of parallel laser beams will travel as far as you like and they will always remain the same distance apart and parallel.
Ironically, the best evidence for this comes from detailed measurements of the cosmic microwave background by the WMAP and now Planck satellites.
The problem you are having is you (I think) are imagining that the big bang happened at a point in space 13.7 billion years ago, and that radiation has been travelling outwards from that point. This is incorrect. Every point in space that we see now was, about 13.7 billion years ago, part of the big bang. As the space in the Universe expanded, its contents cooled and due to the trapping of free electrons by positively charged protons to form hydrogen atoms, the light that was emitted by the hot gas everywhere in the Universe at a time about 400,000 years after the big-bang was able to travel unabsorbed and unscattered. This radiation has travelled (at the speed of light) in all directions.
Now, when we observed the microwave background, we are seeing light that has been travelling in a straight line for just short of 13.7 billion years. That light was in the near infrared and visible part of the spectrum when it was emitted, but because of the expansion of space, the wavelength has also been stretched by a factor of 1100 to the microwave/short-wave radio part of the spectrum.
Alien Planet Radio Signals Detected–“First Hint from a World Beyond Our Solar System”
Scientists suggest that there may be evolutionary parallels on the different worlds because creation tends to be economical. In what could someday lead to a confirmation of that insight, the first radio emission were collected from the magnetic field of a world beyond our solar system by monitoring signals from Constellation Bootes, with the Low Frequency Array (LOFAR) radio telescope in the Netherlands.
From the Tau Boötes Star System
“We present one of the first hints of detecting an exoplanet in the radio realm,” said Jake Turner of the Observatoire de Paris. “The signal is from the Tau Boötes system, which contains a binary star and an exoplanet. We make the case for an emission by the planet itself. From the strength and polarization of the radio signal and the planet’s magnetic field, it is compatible with theoretical predictions.”
Among the co-authors is Turner’s postdoctoral advisor Ray Jayawardhana, a professor of astronomy at Cornell University. The team, led is by Cornell postdoctoral researcher Turner, Philippe Zarka of the Observatoire de Paris – Paris Sciences et Lettres University and Jean-Mathias Griessmeier of the Université d’Orléans.
“If confirmed through follow-up observations,” Jayawardhana said, “this radio detection opens up a new window on exoplanets, giving us a novel way to examine alien worlds that are tens of light-years away.”
“A Significant Radio Signature”
Using LOFAR, Turner and his colleagues uncovered emission bursts from a star-system hosting a so-called hot Jupiter, a gaseous giant planet that is very close to its own sun. The group also observed other potential exoplanetary radio-emission candidates in the 55 Cancri (in the constellation Cancer) and Upsilon Andromedae systems. Only the Tau Boötes exoplanet system – about 51 light-years away – exhibited a significant radio signature, a unique potential window on the planet’s magnetic field.
Observing an exoplanet’s magnetic field helps astronomers decipher a planet’s interior and atmospheric properties, as well as the physics of star-planet interactions, said Turner, a member of Cornell’s Carl Sagan Institute.
Magnetic Field Hints at Possible Habitability
“The magnetic field of Earth-like exoplanets may contribute to their possible habitability,” Turner said, “by shielding their own atmospheres from solar wind and cosmic rays, and protecting the planet from atmospheric loss.” Realizing, of course, that habitability does not equal life.
Two years ago, Turner and his colleagues examined the radio emission signature of Jupiter and scaled those emissions to mimic the possible signatures from a distant Jupiter-like exoplanet. Those results became the template for searching radio emission from exoplanets 40 to 100 light-years away.
After poring over nearly 100-hours of radio observations, the researchers were able to find the expected hot Jupiter signature in Tau Boötes. “We learned from our own Jupiter what this kind of detection looks like. We went searching for it and we found it,” Turner said. “There remains some uncertainty that the detected radio signal is from the planet. The need for follow-up observations is critical.”
Turner and his team have begun a campaign using multiple radio telescopes to follow up on the Tau Boötes signal.
The Daily Galaxy, curated and edited by Sam Cabot, via Cornell University
Dutch-Chinese radio telescope antennas unfolded behind the moon
The three antennas on the Dutch-Chinese radio telescope, which is currently located behind the moon, have been unfolded. This was officially announced today by the Dutch team. The Netherlands-China Low Frequency Explorer (NCLE) hung in space waiting for over a year. This was longer than initially planned, as the accompanying communications satellite had to assist a Chinese lunar lander for a longer time.
The Chinese satellite was previously mainly seen as a communications satellite. However, the Chinese moon mission has by now achieved its primary goals. Consequently, the Chinese have redefined the satellite to be a radio observatory. As such, the Netherlands-China Low Frequency Explorer is the first Dutch-Chinese space observatory for radio astronomy.
Marc Klein Wolt, managing director of the Radboud Radio Lab and leader of the Dutch team, is happy: "Our contribution to the Chinese Chang'e 4 mission has now increased tremendously. We have the opportunity to perform our observations during the fourteen-day-long night behind the moon, which is much longer than was originally the idea. The moon night is ours, now."
Last week, Klein Wolt went to China with engineer Eric Bertels from the antenna manufacturer ISISpace to prepare the unfolding of the antennas. Bertels: "The launch eighteen months ago was already extremely thrilling, of course, but we had no hand in it. Now that our own instrument was concerned, things were rather different."
Albert-Jan Boonstra of ASTRON is pleased to see that the antennas have been unfolded after three years of hard work: "This is a unique demonstration of technology that paves the way for future radio instruments in space."
Heino Falcke of Radboud University and scientific leader of the Dutch-Chinese radio telescope can barely wait to get his hands on the first measurements. "We are finally in business and have a radio-astronomy instrument of Dutch origin in space. The team has worked incredibly hard, and the first data will reveal how well the instrument truly performs."
The longer stay behind the moon most probably did have an effect on the antennas. At first, the antennas unfolded smoothly, but as the process progressed, it became increasingly difficult. The team therefore decided to collect data first and perhaps unfold the antennas further at a later point in time. With these shorter antennas, the instrument is sensitive to signals from around 800 million years after the Big Bang. Once unfolded to their full length, they will be able to capture signals from just after the Big Bang.
Netherlands-China Low Frequency Explorer
The Netherlands-China Low Frequency Explorer (NCLE) is a prototype radio telescope built to record weak radio signals from a period just following the Big Bang, called the Dark Ages. These signals are blocked by the Earth's atmosphere, which is why the telescope was placed on a satellite and brought to a location behind the moon. With this satellite, called QueQiao, the China National Space Administration (CNSA) has been navigating a lunar lander that has been driving around the back of the moon since early 2019. The Netherlands-China Low Frequency Explorer was developed in the Netherlands by Radboud University (Nijmegen), ASTRON (Dwingeloo) and the ISISpace company (Delft), with support from the Netherlands Space Office.
Is the space roar coming from the Milky Way?
Whether or not this source is inside or outside the Milky Way is under debate.
"There are good arguments why it cannot be coming from within the Milky Way, and good arguments for why it cannot be coming from outside the galaxy," Kogut said.
One reason it probably isn't coming from within our galaxy is because the roar doesn't seem to follow the spatial distribution of Milky Way radio emission. But nobody is saying for certain that the signal isn't from a source closer to home — only that the smart money is on it coming from elsewhere.
This article is brought to you byAll About Space.
All About Space magazine takes you on an awe-inspiring journey through our solar system and beyond, from the amazing technology and spacecraft that enables humanity to venture into orbit, to the complexities of space science.
"I wouldn't quite say that scientists have largely ruled out the possibility of the radio synchrotron background originating from our galaxy," said Jack Singal, an assistant professor of physics at the University of Richmond in Virginia, who recently led a workshop on the matter. "However, I would say that this explanation does seem to be less likely.
"The primary reason is that it would make our galaxy completely unlike any similar spiral galaxy, which as far as we can tell do not exhibit the sort of giant, spherical, radio-emitting halo extending far beyond the galactic disk that would be required. There are other issues as well, such as that it would require a complete rethinking of our models of the galactic magnetic field."
Fixsen agrees wholeheartedly. "In other spiral galaxies there is a close relation between the infrared and radio emission, even in small sections of these others," he said. "So, if it is from a halo around our galaxy, it would make the Milky Way a weird galaxy, while in most other respects it seems like a 'normal' spiral galaxy."
For those reasons, experts think the signal is primarily extragalactic in origin. "It would make it the most interesting photon background in the sky at the moment because the source population is completely unknown," Singal said. But since the universe is so vast this doesn't exactly narrow things down that much, which is why scientists have been working hard to come up with multiple theories for the signal's source.
American physicist David Brown, for example, said the space roar could be "the first great empirical success of M-theory," a broad mathematical framework encompassing string theory. "There might be a Fredkin-Wolfram automaton spread across multitudes of alternate universes, yielding recurrent physical time with endless repetitions of all possible physical events," Brown wrote on the FQXi Community blog. What this supposes is that the early universe had much more real matter than today, accounting for the powerful radio signal.
The space roar could be "the first great empirical success of M-theory," a broad mathematical framework encompassing string theory.- Physicist David Brown
But if that is too far out, there are other theories to get your teeth into. "Radio astronomers have looked at the sky and have identified a couple of types of synchrotron sources," Fixsen said.
Synchrotron radiation is easy to make, he said. "All you need is energetic particles and a magnetic field, and there are energetic particles everywhere, produced by supernovas, stellar winds, black holes, even OB stars," which are hot, massive stars of spectral type O or early-type B. "Intergalactic space seems to be filled with very hot gas, so if intergalactic magnetic fields were strong enough [stronger than predicted], they could generate smooth synchrotron radiation," he said.
It is also known that synchrotron radiation is associated with star production. "This also generates infrared radiation, hence the close correlation," Fixsen said. "But perhaps the first stars generated synchrotron radiation yet, before metals were produced, they did not generate very much infrared radiation. Or perhaps there is some process that we haven't thought of yet."
So what does this leave us with? "Possible sources include either diffuse large-scale mechanisms such as turbulently merging clusters of galaxies, or an entirely new class of heretofore unknown incredibly numerous individual sources of radio emission in the universe," Singal said. "But anything in that regard is highly speculative at the moment, and some suggestions that have been raised include annihilating dark matter, supernovas of the first generations of stars and many others."
Some scientists have suggested gases in large clusters of galaxies could be the source, although it's unlikely ARCADE's instruments would have been able to detect radiation from any of them. Similarly, there is a chance that the signal was detected from the earliest stars or that it is originating from lots of otherwise dim radio galaxies, the accumulative effect of which is being picked up. But if this was the case then they'd have to be packed incredibly tightly, to the point that there is no gap between them, which appears unlikely.
Cosmic dawn: astronomers detect signals from first stars in the universe
An artist’s impression of the universe’s first, massive, blue stars embedded in gaseous filaments, with the cosmic microwave background just visible at the edges. Illustration: NR Fuller, National Science Foundation
An artist’s impression of the universe’s first, massive, blue stars embedded in gaseous filaments, with the cosmic microwave background just visible at the edges. Illustration: NR Fuller, National Science Foundation
Last modified on Wed 28 Feb 2018 22.00 GMT
Astronomers have detected a signal from the first stars as they appeared and illuminated the universe, in observations that have been hailed as “revolutionary”.
The faint radio signals suggest the universe was lifted out of total darkness 180m years after the big bang in a momentous transition known as the cosmic dawn.
The faint imprint left by the glow of the earliest stars also appears to contain new and unexpected evidence about the existence and nature of dark matter which, if confirmed by independent observatories, would mark a second major breakthrough.
“Finding this minuscule signal has opened a new window on the early universe,” said Judd Bowman of Arizona State University, whose team set out to make the detection more than a decade ago. “It’s unlikely we’ll be able to see any earlier into the history of stars in our lifetime.”
Following the big bang, the universe initially existed as a cold, starless expanse of hydrogen gas awash with radiation, known as the Cosmic Microwave Background. This radiation still permeates all of space today and astronomers are beginning to scrutinise this cosmic backdrop for traces of events that occurred in the deep past.
During the next 100m years – a period known as the dark ages – gravity pulled slightly denser regions of gas into clumps and eventually some collapsed inwards to form the first stars, which were massive, blue and short-lived. As these stars lit up the surrounding gas, the hydrogen atoms were excited, causing them to start absorbing radiation from the Cosmic Microwave Background at a characteristic wavelength.
This led scientists to predict that the cosmic dawn must have left an imprint in the Cosmic Microwave Background radiation in the form of a dip in brightness at a specific point in the spectrum that ought, in theory, to still be perceptible today.
In practice, detecting this signal has proved hugely challenging, however, and has eluded astronomers for more than a decade. The dip is swamped by other, more local, sources of radio waves. And the expansion of the universe means the signal is “red-shifted” away from its original characteristic wavelength by an amount that depends on precisely when the first stars switched on. So scientists were also not sure exactly where in the spectrum they should be looking –and some predicted the task would prove impossible.
“The team have to pick up radio waves and then search for a signal that’s around 0.01% of the contaminating radio noise coming from our own galaxy,” said Andrew Pontzen, a cosmologist at University College London. “It’s needle-in-a-haystack territory.”
Remarkably, Bowman and colleagues appear to have overcome these odds using a small, crude-looking instrument the size of a small table. The Edges (Experiment to Detect Global EoR Signature) antenna sits in a remote region of Western Australia where there are few human sources of radio waves to interfere with incoming signals from the distant universe. The wavelength of the dip suggest that the cosmic dawn occurred about 180m years after the big bang, 13.6bn years ago and nine billion years before the birth of the sun.
The signal also indicated a second milestone at 250m years after the big bang, when the early stars died and black holes, supernovae and other objects they left behind heated up the the remaining free hydrogen with x-rays.
In a paper published in the journal Nature, Bowman and colleagues detail the elaborate experimental steps they took to prove the signal was real – several years of replications, changing the angle of the antenna, altering the setup.
The Edges antenna, which consists of two rectangular metal panels mounted horizontally on fibreglass legs above a metal mesh. It sits in a remote part of Western Australia Photograph: Dragonfly Media/CSIRO Australia
“Telescopes cannot see far enough to directly image such ancient stars, but we’ve seen when they turned on in radio waves arriving from space,” said Bowman.
Emma Chapman, Royal Astronomical Society research fellow at Imperial College London, described the result as “an incredible achievement, constituting the first ever detection of the era of the first stars”. The huge significance of the result, she added, meant it needed to be replicated by an independent experiment.
The detection also contained a major surprise. The size of the dip was twice as big as predicted. This suggests the primordial hydrogen gas was absorbing more background radiation than predicted and would suggest the universe was significantly colder than previously thought, at about -270C.
In a second Nature paper, Rennan Barkana, a professor of astrophysics at Tel Aviv University, proposes a potentially groundbreaking explanation: that the hydrogen gas was losing heat to dark matter. Until now, the existence of dark matter – the elusive substance that is thought to make up 85% of the matter in the universe – has only been inferred indirectly from its gravitational effects. If confirmed, these results would suggest a new form of interaction between normal matter and dark matter, mediated by a fundamental force that until now has been entirely unknown.
The theory would also suggest that dark matter particles, the properties of which remain completely mysterious, must be light rather than heavy, which would rule out one of the leading hypothetical candidates for dark matter, known as weakly interacting massive particles – or wimps.
Lincoln Greenhill, a senior astronomer at Harvard University, said that if confirmed the dark matter observations could be revolutionary. “We know so little about it that there are many theories as to what dark matter is,” he said. “Many may shortly be eliminated from the running.”
How to Hear Radio Waves from Space
Light is all around us, and it comes in many different varieties. Visible light shines on your world every day and allows you to see the incredible planet we live on. Gamma rays shoot out from pulsars and solar flares. X-rays are emitted from the disk of hot materials surrounding a black hole. But on the other end of the spectrum, there’s a wavelength of light that you might be a little more familiar with. Radio waves. You’re probably thinking about the kind of radio you turn on in your car, but there are other sources of radio waves that are not so local with far more incredible messages than this week’s top 40. Here’s how you can tune in to the station the universe is playing 24/7.
1. Access a radio telescope.
Obviously, the best way to hear signals from space would be to access the technology that astronomers use, which are radio telescopes. Like visible light telescopes, radio telescopes take in the wavelengths that are coming from space, but they are able to pick up on radio waves rather than visible light waves. This offers an entirely new view of the heavens and reveals a universe full of strange and mysterious objects. Even if you’re not able to use these telescopes yourself, you can access the information they collect when discoveries are made and results are published.
2. Listen online.
If you’re not an astronomer, you can still listen to signals and from the comfort of your home, to boot. There are a few websites like https://www.spaceweatherradio.com/ that allow you to listen in on other observatories and hear the telltale “ping” that indicates a meteor or other object is passing overhead.
3. Set up your own scanner.
If you’re techy and willing to put in the work, you can set up your own scanner to pick up on radio waves. While you won’t technically hear anything coming from space, you’ll hear signals that came from Earth and are bouncing off things like satellites, meteors, and other space objects that are nearby. This method involves some location calculations so that you can pick up on what’s known as the “space fence.” Then, you’ll need to get a radio scanner that has the ability to pick up on VHF-UHF signals. Grab an antenna, point it in the right direction, then sit back and listen.
How Two Pigeons Helped Scientists Confirm the Big Bang Theory
In 1964, when Robert W. Wilson and Arno A. Penzias initially heard those astonishing radio signals that would lead to the first confirmed proof for the Big Bang Theory, they wondered if they had made a mistake. Was the signal actually radio noise from nearby New York City? Was it the after-effects of a nuclear bomb test that had been conducted over the Pacific several years earlier? Could it be a signal from the Van Allen belts, those giant rings of charged radiation circling the Earth?
Or maybe, the hissing sound was the result of a defect in their instrument?
“I had a lot of experience fixing practical problems in radio telescopes,” Robert Wilson now says. He and his wife Betsy Wilson still live in Holmdel, New Jersey, not far from hilltop where the tests were run. “We looked for anything in the instrument or in the environment that might be causing the excess antenna noise. Among things, we searched for radiation from the walls of the antenna, especially the throat, which is the small end of the horn. We constructed a whole new throat section and then tested the instrument with it.”
At one point, new suspects emerged. Two pigeons had set up housekeeping inside the guts of the antenna. Maybe their droppings were causing the noise? Wilson and Penzias had the birds trapped and then cleaned the equipment, but the signals continued.
After a year of experiments, the scientists concluded that they’d detected the cosmic background radiation, an echo of the universe at a very early moment after its birth.
“We started out seeking a halo around the Milky Way and we found something else,” notes Dr. Wilson. “When an experiment goes wrong, it’s usually the best thing. The thing we did see was much more important than what we were looking for. This was really the start of modern cosmology.” In fact, Wilson and Penzias were awarded the Nobel Prize in Physics in 1978 for determining that the hiss they were hearing wasn't pigeon poop at all, but the faint whisper of the Big Bang, or the after glow that astronomers call the cosmic microwave background.
Visitors to the Smithsonian Air and Space Museum have long been able to view an unassuming artifact of that Nobel Prize-winning discovery. On the first floor in the "Exploring the Universe" gallery that metal trap built to capture the squatting pigeons, can be seen, along with some other instrumentation of that propitious moment 50 years ago. The pigeon trap is on loan from Robert Wilson.
Other artifacts survive. Arno Penzias, who’d come to the United States as a child refugee from Nazi Germany, sent the radio receiver and its calibration system to the Deutsches Museum of Munich, the city of his birth.
As for the giant horn antenna, it still stands tall on Holmdel Road, where it can be seen by the public.
On Thursday, February 20 at 7:30, Wilson will be joined in a panel discussion by cosmologist Alan Guth and astronomers Robert Kirshner and Avi Loeb at the Harvard-Smithsonian Center for Astrophysics, in celebration of the 50th anniversary of the confirmation of the Big Bang Theory. Watch the discussion live on YouTube.
About Claudia Dreifus
Author and educator Claudia Dreifus produces the feature "Conversation With. . ." in the New York Times. @claudiadreifus
How astronomers saw gravitational waves from the Big Bang
Lead discoverer John Kovac describes his work at the BICEP2 radio telescope and how his career took him there.
On 17 March, John Kovac announced to the world that he and his team of radio astronomers had found the imprint of gravitational waves from the Big Bang. They did so by looking at the cosmic microwave background (CMB), sometimes called the 'afterglow' of the Big Bang, using BICEP2, a telescope experiment based at the South Pole. This signal of gravitational waves was seen in the polarization of the CMB — similar to the kind of polarization that certain sunglasses block — over a small patch of sky.
This polarization map, which is reminiscent of the way iron filings arrange themselves on a surface under the effects of a magnetic field, was found to have particular vortex-like, or curly, patterns known as B modes. The presence of B modes is a tell-tale sign of the passage of gravitational waves generated during inflation, a brief period during which the Universe underwent an exponential expansion, right after its birth. If the findings stand up, they will put the current preferred picture of cosmology on solid foundations, and could have significant implications on fundamental physics as well.
Kovac is a radio astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Here he talks to Nature about the findings and some of their implications.
What are we seeing in BICEP2's snapshots of the CMB polarization?
The most important result we’re focused on is the implications of the signal we detected for models of inflation. We are seeing a direct image of a [primordial] gravitational wave, causing light to be polarized in a particular way. The CMB is a snapshot of the Universe 380,000 years after the Big Bang, when the radiation first streamed freely into space, but the gravitational-wave signal was imprinted on the CMB a tiny fraction of a second after the birth of the Universe.
What else is important about the finding?
Everyone in cosmology knows — but it is not widely appreciated — that the prediction about B modes from inflation relies not just on the phenomenon of gravitational waves but on the quantization of gravity itself. Inflation assumes that everything started out as quantum fluctuations that then got amplified by inflation. So at a very deep level, this finding relies on the connection between quantum mechanics and gravity being right.
Did it cause concern that BICEP2 had detected a B-mode polarization signal that was nearly twice as high as data from the Planck spacecraft suggested?
The Planck data [released so far] came from a temperature map of the CMB, not from a direct polarization measurement. We were always committed to doing an extra careful job on this analysis, but I will admit that the presence of a larger signal-to-noise ratio in our data [compared with the Planck data] sharpened our focus in thinking about every possible systematic explanation over the past three years that could have falsified the signal. We’ve done the most extensive systematic analysis that I’ve ever been involved in by far.
When did you first realize that you had detected the long-sought 'smoking gun for inflation'?
Last fall, when we first compared the BICEP2 signal with BICEP1. That was very powerful because BICEP1 had very different detectors and used much older technology. So the fact that we were able to see the same signal with this completely different kind of telescope laid a lot of lingering doubts to rest. The remaining sceptics on our team were convinced at that point.
In early December I was at the South Pole and we had a very intense meeting where I laid out all the tests the data had passed and the milestones still to be achieved, and that we would publish if those remaining tests were passed.
Did you celebrate at that point, or have you celebrated since then?
My role in this process has been to remain calm at all times. The time to celebrate, I think, will be once we have published our results and presented them to the scientific community.
What got you interested in the CMB in the first place?
In high school, I read Steven Weinberg's excellent popular book on cosmology, The First Three Minutes [Basic Books, 1977], and it captured my imagination. I remember reading the words:
"Now we come to a different kind of astronomy, to a story that could not have been told a decade ago. We will be dealing not with observations of light emitted in the last few hundred million years from galaxies more or less like our own, but with observations of a diffuse background of radio static left over from near the beginning of the universe."
That's how Weinberg introduced the discovery of the CMB and its implications, then still very fresh, for cosmology. As a kid, it seemed clear to me that this was the coolest thing in all of science — there are no bigger questions.
I chose to go to Princeton University as an undergrad partly because I read about it in that book. [Some of the major players in the field of CMB astronomy] Jim Peebles, Robert Dicke and David Wilkinson were there, and by an incredible stroke of fortune I was assigned to Dave Wilkinson for a work-study job. He directed me to a CMB lab that was planning to try to build a CMB telescope at the South Pole. I became so captured that I actually took a year out of school to get a chance to go to the South Pole myself. That was 1990–91, not long before the Cosmic Background Explorer (COBE) satellite discovered the first fluctuations in the CMB. Our telescope at the South Pole saw them, too, less than a year later. I've been doing it ever since: 23 trips to the pole and a career in which I've been fortunate to work at the frontiers of CMB.
You have a picture of the late astrophysicist Andrew Lange, of the California Institute of Technology in Pasadena, on your bookshelf. He mentored many students who were conducting CMB experiments before he lost his battle with depression and committed suicide in 2010. What role did he play in shaping your career?
I worked in Andrew's lab as a postdoc at Caltech and then as a senior fellow before moving to Harvard. Andrew was an inspiration and a close friend. He entrusted me with a huge amount of responsibility, encouraging me to take charge of the deployment and operation of the BICEP1 telescope and then to step into the role of [principal investigator] and leader of the next one, BICEP2.
Andrew was fond of describing the quest for B-mode polarization as "cosmology's great wild goose chase". He would have enjoyed seeing this result, and knowing that we found not a goose but an ostrich!
I was also a graduate student of [University of Chicago astronomer] John Carlstrom. While John is currently a competitor [at the South Pole Telescope], he is also one of my closest friends. I have had two amazing mentors.
How old is your son, and what does he think about all of this?
Nine. He’s very excited and it’s amazing how much he can absorb and understand and explain to my wife. He would go to the South Pole with me if he was old enough.
What Created These Mystery Radio Waves From Another Galaxy?
CSIRO's Parkes radio telescope, which has been used to confirm a population of Fast Radio Bursts, is shown superimposed on an image showing the distribution of gas in our Galaxy. Credit: Swinburne Astronomy Production.
A single, gleaming flash of radio waves zooms toward us from halfway across the universe. Where it came from, nobody was sure, and it was gone in an instant.
The Lorimer burst, named after the astronomer who discovered it in a stack of half-a-decade old records, has stumped scientists for the last six years. But today a team of astronomers has announced that they've found four more flares just like it.
"You have to look at the sky for a very long time to find these," says Dan Thornton, the astrophysicist at the University of Manchester who discovered the new radio wave bursts. "The reason that we're detecting them now is we've simply looked long enough." Thornton and his colleagues have just published a paper in the scientific journal Science saying that these strange radio wave bursts are an entirely new astronomic phenomenon.
"Some people actually suspected the Lorimer burst was an atmospheric event," and a fluke measurement, says Manjari Bagchi, an astrophysicist at the International Centre for Theoretical Sciences, in Bangalore, India, who has also searched for these radio wave flares but was not part of the study. "But this proves that these are all natural phenomenon," Bagchi says.
Each flash of energy lasts only a few milliseconds, and researchers still don't know what causes them. "We think they're probably caused an explosive event, because we haven't seen them repeat," Thornton says. And pinpointing their exact origin is just about out of the question, given how rare they are and how big space is.
Thornton and his colleagues think a good bet for the burst's beginnings might be magnetars, which are rare and incredibly dense husks of past supernovae that are prone to occasional explosions of energy. "A magnetar can give off more energy in a millisecond than the sun in 300,000 years," Thornton says.
Whatever created them, Thornton's radio wave bursts hail from so far away that that they've taken half of the universe's life to reach us. "That's halfway to the big bang," Thornton says. That long travel leaves its mark on the radio waves: As the waves pass through charged particles in space, they're stretched out slightly. Thornton believes that even though we don't know the cause of the flares, by measuring that stretch and studying more of them, "we can use them to probe the material between us and the big bang."
What Are Gravitational Waves, And How Do We Find Them?
With a monumental detector powering up for a new generation of experiments, Rana Adhikari, a Caltech physicist, is chasing down these elusive signals. He tells PopMech what gravitational waves are, why scientists are on the cusp of measuring them, and how these waves will change the way we look at the universe.
January 14, 2016: This week there's been a new storm of rumors suggesting scientists might have detected gravity waves, finally. But this time around, everyone is taking the announcement with a big grain of salt. Back in May 2014, we published this interview with Rana Adhikari about why the chase is so difficult and fraught with false starts.
So what exactly are gravitational waves?
I think it's easiest to explain by analogy. For an ocean wave, the wave is just the movement of the water. Water is the medium. And in the case of sound waves, air is the medium. But for gravitational waves, there is no mediumat least not in the sense of some matter. What's moving is space itself. If you imagine space as having grid-lines, gravitational waves are the fluctuation of those grid-lines. They're the warping of the actual coordinates of space.
We're all making gravitational waves all the time. They're caused by the acceleration of [virtually any] mass, and they travel at the speed of light. Things like biking down the street or the flight of a bumblebee makes these waves, albeit exceedingly weak ones.
But space is extremely stiff, and so the amount of energy it takes to make a wave which we could conceivably measure is [monumental]. All practical schemes for detecting gravitational waves are aimed at detecting those from super-massive sourcesthings which are roughly the size of the sun or thousands of times bigger than thatthat are moving at a good fraction of the speed of light.
And what's our interest in these waves?
Our hope is to do astronomy with them. We want to use them as a tool to hear (the information is a lot more like sound than light) astrophysical phenomena all over the universe, such as the merging of pairs of neutron stars or black holes. And ultimately, we'd like to use these waves to test Einstein's theory of gravity.
And unlike light or radio waves where you have to worry about obstructions along your line of sight, gravitational waves basically travel unimpeded through matter and space. So you're able to get a picture of an event happening anywhere in the universe with virtually no distortion. It takes something like a black hole to significantly scatter these waves.
Have we ever detected them before?
Well the answer is kind of semantic. Although gravitational waves were first predicted by Einstein in 1916, our first observational evidence of them wasn't found until 1974.
In 1974 there was a binary star system that was discovered by astronomers Russell Hulse and Joseph Taylor. The orbit of these stars decayed at just the precise rate that Hulse and Taylor calculated that energy had to be exiting in the form of gravitational waves. More [recently], last March the BICEP2 instrument announced it'd found the fingerprint of gravitational waves from immediately after the big bang in the cosmic microwave backgroundwhich is the oldest light we can see in the universe.
But we've never directly measured the waveform of gravitational waves on Earth. The difference is almost like [seeing proof] that sound was made, versus actually hearing and recording that sound. But the other methods are just as legitimatethese are all detection techniques.
But we're trying to detect them now with the instrument you're working with, the Laser Interferometer Gravitational Wave Observatory (LIGO). Can you explain what LIGO is and does?
Well, LIGO is basically a very powerful and very stable laser [measuring device]. We have a laser beam which is split in two and is bounced off two of the most exquisitely well polished mirrors in the world. One half of the laser beam goes 2.5 miles north to one mirror, and the other goes 2.5 miles east to the other. After the light bounces off those mirrors and comes back, we can measure how far each has traveled. If a gravitational wave comes by, the physical space in between the laser and the mirror can be distorted, and so the laser beams will travel different distances.
The Washington State LIGO detector.
But the change in distance we expect from a gravitational wave is a ridiculously smalla billion times smaller than the size of an atom. It's so faint that everything on the Earth seems to conspire to cover up these waves. Anything you can imagine is (probably correctly) a problem for us: the acoustic noise of a plane flying overhead, electromagnetic changes from lightning strikes anywhere in the country, the ambient seismic vibrations of the Earth.
So much of our effort has been focused on the humongous engineering challenge of shielding ourselves from this ambient noise. And what we can't shield, we have all types of detectors so we can subtract any additional noise from our system. But there are limits, which is why we have two devices at opposite ends of the countryin Louisiana and Washington state. In order for us to claim a gravitational wave detection, the wave must be the same at both sites.
You recently said that we're on the cusp of not only directly detecting these waves, but of measuring them and finally doing astrophysics with them. Why is that?
Although people have made LIGO-type detectors since the '70s, the first large scale ones only came into operation around 2000. Our first generation of LIGO ran from 2002 to 2010. We knew that that detector didn't have a great chance at detecting signals, but we wanted experience with the technology and the engineering challenges. We searched, but we didn't find anything.
But we are just now finishing up the instillation of the second generation detector. And we expect that, starting late next year, we'll be able to directly detect gravitational waves for the first time. We estimate that we'll have at least several detections per year, and that there will be some that will come in with enough signal amplitude that we'll be able to use those gravitational waves to do some very interesting astrophysics. But I think no matter what I say, whatever number I predict, I'll end up being wrong. There are many unknowns, and nature is bound to surprise us.
Really though, my claim was mostly focused on what we'll be able to do with the following generation of detectors, the thirdwhich I hope is between 5 to 10 years out. We're now starting to explore tricks like using cryogenic techniques to cool down our mirrors, and using so-called squeezed light with our lasers.
When we do finally detect these waves, what's next?
There are plans for space-based detectors, and those have benefits. For one, you don't have to pay for real estate, and the detectors can be extremely big. You also don't have all the noise issuesfrom earthquakes, and lighting and manmade sourcesthat you have with ground-based detection.
As for LIGO, will there just be an endless number of generations? I don't know, but in some way that's really the beauty of astronomy. You keep making more sensitive instruments, and whenever you have a chance to observe something about the universe in a different way, you do it. Because there will always be more to look for.
I see this as being similar to the beginning of the 20th century, when all astronomers had were optical telescopes. When you look through those telescopes, the universe seems pretty steady, like there's not a lot going on. But as people learned observe the sky in things like radio waves, x-rays, gamma rays, they saw that it's really quite the opposite. You look out into space and there are all kinds of exciting phenomena: stars are exploding, galaxies are emerging, black holes are at the center of galaxies. It's a violent and vibrant universe.
That change of our understanding of space came about because we utilized new types of observational tools. Our hope for gravitational waves is not just that they'll be useful as an observational tool, but they'll once again radically change how we look at the universe.