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Physics/gravitational waves

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Question
Hi Steve,

Scientists at LIGO recently detected the gravitational waves . How did they detect the blackholes collision which is 2.5 billion light years away and expected the gravitational waves to pass through the earth at precise time. There could have been so many supernova/blackhole collisions which would have generated  waves that might have interfered with the referred gravitational waves, so how can we be sure that what was detected is accurate. When are they expecting the next gravitational waves to pass through earth to confirm their discovery.

Does earth wobble due to atmospheric winds etc which can be  precisely detected.

Also we know that storm and so many phenomenon are not accurately predictalble. If these were not precisely known, how could gravitational waves emitted billion light years ago can be detected precisely.  

Kindly clarify.

Regards,

Answer
To your first question, you should read this article from Science News on the topic: https://www.sciencenews.org/article/gravitational-waves-explained?tgt=nr  It's quite good.  They can't predict when their next gravitational waves of detectable size will pass by, because gravitational waves travel at the speed of light.  Advanced LIGO currently operates in two locations in the United States, to ensure that the gravitational waves are caught at the same time to eliminate fluke signals.

The Earth wobbles, but it is not due to wind.  Wind is really tiny compared to other forces being exerted on the enormous Earth...the whole atmosphere is a thin and delicate skin covering the surface of the Earth, and not very dense compared to rock (thousands of times less dense).  http://www.cotf.edu/ete/modules/msese/dinosaurflr/wobble.html

Storms are chaotic systems that interact and deviate in an exponential fashion from predictions.  Gravitational waves are more like light, and we can easily see light from stars billions of light years away.  Also, the energy released in the collision was estimated to be 50 times the energy output (during the brief, but violent collision) of all the stars in the known universe...that's a very powerful signal, indeed!  Some of it did appear to make it all the way here.

All-in-all, it was an incredible measurement.   This was the work of hundreds of brilliant scientists working for decades on this one problem, so it's not surprising that it's a huge technical feat.

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Dr. Stephen O. Nelson

Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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