2017 NOBEL PRIZE IN PHYSICS- DISCOVERY OF GRAVITATIONAL WAVES

 

2017 NOBEL PRIZE IN PHYSICS- 

DISCOVERY OF GRAVITATIONAL

 WAVES

ഭൂ​ഗു​രു​ത്വ ത​രം​ഗ​ങ്ങ​ളു​ടെ ക​ണ്ടെ​ത്ത​ലി​നു

ഭൗ​തി​ക​ശാ​സ്ത്ര നൊ​ബേ​ൽ

Around 1.3 billion years ago, in a far-flung corner of the universe, two black holes — the densest, most destructive forces known to nature — collided with one another.A hundred years ago, Albert Einstein predicted that such a massive collision would distort the very fabric of space and time itself. Like a stone cast into a pond, the cataclysmic disturbance would ripple outward, at the speed of light, filling the ocean of the universe with gravitational waves. Einstein, however, never thought it would be possible to detect such waves.

In a massive achievement of human ingenuity and patience, scientists announced in 2016 that they detected these waves as they slid through the Earth. (Since then, they’ve detected them three more times.) And today, their effort to record gravitational waves for the first time — a decades-long collaboration involving thousands of scientists around the globe — has been awarded the Nobel Prize in physics.A Nobel can only go to a maximum of three laureates, however, and so this one went to physicists Rainer Weiss, Kip Thorne, and Barry Barish. They pioneered LIGO, or the Laser Interferometer Gravitational-Wave Observatory, the scientific project that made gravitational wave detection possible.

In the 1970s, Weiss and Thorne dreamt up the initial idea to detect gravitational waves. When Barish took over as lead of the project in 1994, he oversaw the crucial decision to increase the power and sensitivity of the detectors, which allowed for the final discovery. Weiss was awarded one half of the 9,000,000 Swedish Kroner prize (about $1.1 million). Thorne and Barish split the second half.Though these three got the prize, know that LIGO was the result of thousands of scientists working world over in collaboration for decades. (Critics argue that giving the award to three individuals distorts the public’s perception of how science actually gets done.)

And they didn’t just answer a 100-year-old question — they launched a whole new branch of science.Right now, our telescopes can only see objects that emit electromagnetic radiation — visible light, X-rays, gamma rays, and so on. But some objects, like colliding black holes or the smoking gun of the Big Bang, don't emit any electromagnetic radiation. Instead, they emit gravity. And that's why, with gravitational wave astronomy, hard-to-detect objects in the universe — like black holes and neutron stars — may soon come into clearer focus.“We now witness the dawn of a new field: gravitational wave astronomy,” Nils Mårtensson, chair of the Nobel Committee for Physics, said at the announcement Tuesday. “This will teach us about the most violent processes in the universe and it will lead to new insights into the nature of extreme gravity.”

Gravitational waves, explained

Just as sound waves disturb the air to make noise, gravitational waves disturb the fabric of spacetime to push and pull matter as if it existed in a funhouse mirror. If a gravitational wave passed through you, you’d see one of your arms grow longer than the other. If you were wearing a watch on each wrist, you'd see them tick out of sync.Gravitational waves are generated by any movement of mass. "For instance, if I wave my arms really crazily, I would generate gravitational waves," Sarah Caudill, a physicist at the University of Wisconsin Milwaukee, told me in 2016.

But there’s no way to detect gravitational waves that faint. For now, our sensors need a really, really loud source — like the collision of two black holes.Two black holes colliding unleash a loud thunderclap of gravity. If you were near the black holes when they collided, you’d see the universe expand and contract like you were living inside a funhouse mirror. But by the time they reach the Earth — like ripples nearing the edge of a pond — they grew faint.One of the waves LIGO heard (around Christmas 2015) was around 0.7 attometers tall. An attometer is 10^-18 meters. That’s so, so unbelievably tiny. It’s much smaller than an atom. The following GIF starts out showing the width of an atom, and then zooms down to 10^-18. It’s amazing that we were able to detect something that small.And all of this took decades of work: The theory LIGO tested was developed in the early 20th century, the LIGO project was dreamt up in the 1970s, and began in earnest in the 1980s. It was first turned on in 2002, and it took an international effort to detect and confirm the waves in 2016. It’s having a big moment now, but it goes to show that big breakthroughs have deep roots, and science is ultimately a collaborative, multigenerational effort.

How to catch a gravitational wave

LIGO, which is funded by the National Science Foundation, consists of two enormous science experiments: One is in Louisiana; the other is located in Washington state. Both are massive L-shaped tubes. Each arm of the tube is 2.5 miles long.These instruments are called interferometers, and their design is based on work Weiss conducted in the 1960s. Here’s how they work.

During the experiments, a laser beam is equally split between the two arms. At the end of each arm is a mirror, which reflects the laser back to the starting point. What LIGO is looking for is evidence that gravitational waves are distorting spacetime enough that one of the arms becomes temporarily longer than the other.These changes can be incredibly tiny, since LIGO is sensitive enough to detect a change in distance smaller than the width of a proton."Each detector is like a violin string, and we’re waiting for a gravitational wave to ‘pluck’ each detector string," Dave Reitze, the current executive director of the LIGO Project, said last year.

സ്റ്റോക്ഹോം(സ്വീഡൻ): ഒരു നൂറ്റാണ്ടുമുന്പ് ആൽബർട്ട് ഐൻസ്റ്റീൻ പ്രവചിച്ച ഭൂഗുരുത്വ തരംഗങ്ങളെ സംബന്ധിച്ചു പഠനം നടത്തിയ അമേരിക്കൻ ശാസ്ത്രജ്ഞർക്ക് ഭൗതികശാസ്ത്ര നൊബേൽ പുരസ്കാരം. മസാച്യുസെറ്റ് ഇൻസ്റ്റിറ്റ്യൂട്ട് ഓഫ് ടെക്നോളജിയിലെ പ്രഫസർ റെയ്നർ വീസ്, കാലിഫോർണിയ ഇൻസ്റ്റിറ്റ്യൂട്ട് ഓഫ് ടെക്നോളജിയിലെ പ്രഫസർമാരായ ബാരി ബ്രിഷ്, കിപ് തോണ് എന്നിവർക്കാണ് പുരസ്കാരമെന്നു റോയൽ സ്വീഡിഷ് അക്കാഡമി അറിയിച്ചു. ഏഴ് കോടി രൂപ വരുന്ന സമ്മാന തുകയിൽ പകുതി വീസിന് ലഭിക്കും, പകുതി മറ്റു രണ്ടുപേരും പങ്കിടും.

ഭൂഗുരുത്വ തരംഗങ്ങൾ കണ്ടെത്തിയ ലിഗോ പരീക്ഷണം വിഭാവനം ചെയ്ത് നടപ്പാക്കിയതിനെ ലോകത്തെ പ്രകന്പനം കൊള്ളിച്ച കണ്ടുപിടുത്തമെന്നാണു റോയൽ സ്വീഡിഷ് അക്കാഡമി വിശേഷിപ്പിച്ചത്. നൂറുവർഷം മുന്പ് സാമാന്യ ആപേക്ഷിക സിദ്ധാന്തത്തിൽ ആൽബർട്ട് ഐൻസ്റ്റീൻ ഭൂഗുരുത്വ തരംഗങ്ങളെ സംബന്ധിച്ചു വിശദീകരിച്ചിരുന്നെങ്കിലും ഇത് നേരിൽ കാണാൻ കഴിഞ്ഞിരുന്നില്ല.

ഗുരുത്വതരംഗങ്ങൾ കണ്ടെത്തിയ ലിഗോ(ലേസർ ഇന്റർഫെറോമീറ്റർ ഗ്രാവിറ്റേഷണൽ വേവ് ഒബ്സർവേറ്ററി) പദ്ധതിയിൽ നിലവിൽ രണ്ട് നിരീക്ഷണകേന്ദ്രങ്ങളാണുള്ളത്. അമേരിക്കയിലെ ഹാൻഫോഡിലും, ലിവിംഗ്ടണിലുമാണിവ. ലിഗോയുടെ മൂന്നാമത്തെ നിരീക്ഷണകേന്ദ്രം വരുന്നത് ഇന്ത്യയിലാണ്.

Prof. John Kurakar