Thursday June 16: Gravity! hangout from Stanford on black holes and gravitational waves

Pierre Binétruy and George Smoot invite you to participate to the final hangout of the second session of the Gravity! course. This hangout will focus on black holes and gravitational waves. It will be broadcasted this Thursday June 16 at 19h00 UTC (20h00 London, 21h00 Paris, 12h00 California), live from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at SLAC, Stanford University.

KIPAC_logoThe Google Hangout will be streamed live on Google Hangouts and Youtube for approximately 60 minutes, where you can follow the questions and answers live. If you are not registered in this session of Gravity! you may ask your questions below or on Twitter using#FLGravity.

Two highlights for this hangout will be the recent publication of the first results by the LISAPathfinder mission, as well as the exciting new result of the LIGO-Virgo collaboration announced on June 15.

Our guests for this event will be:


Tom Abel is the director of the Kavli Institute for Particle Astrophysics and Cosmology, joint laboratory of the SLAC National Laboratory and Stanford University. His group explores the first billion years of cosmic history using ab initio supercomputer calculations. He has shown from first principles that the very first luminous objects are very massive stars and has developed novel numerical algorithms using adaptive-mesh-refinement simulations that capture over 14 orders of magnitude in length and time scales.  Most recently he is pioneering novel numerical algorithms to study collisionless fluids such as dark matter.



Roger Blandford, a native of England, held a faculty position at Caltech since 1976 when, in 2003, he moved to Stanford University to become the first Director of the Kavli Institute of Particle Astrophysics and Cosmology. He is a world-renrecognized expert in black hole astrophysics, cosmology, gravitational lensing, cosmic ray physics and compact stars.



michael_landryMichael Landry is Detection Lead Scientist with the LIGO Hanford Observatory in Washington state, and a physicist with the California Institute of Technology. Michael began work in the field of gravitational wave physics as a postdoc with Caltech in 2000, stationed at the LIGO Hanford Observatory, and has remained there as a scientist since that time. From 2010 to 2015, he led the installation of the Advanced LIGO detector at Hanford. This collaborative work, done by the LIGO Scientific and Virgo Collaborations totaling a thousand people, culminated in the first direct detection of gravitational waves from a binary black hole merger, announced Feb 11, 2016.



Stefano Vitale is the Principal Investigator (P.I.) of the LISAPathfinder mission. He is professor at the University of Trento in Italy and is a key figure of the gravitational wave community in Europe. He worked on the cryogenic acoustic detector AURIGA before joining the LISA mission where he is leading the Italian effort. He has developed in Trento a laboratory which contributed the inertial sensor onboard the LISAPathfinder mission.


  • Barbara Harrison

    Wish I could, but I shall be in the middle of a CPR course.

  • Ania

    super!!! j’attends

  • Alain Durand

    is there a maximum mass for black holes, if not could we consider that the universe would eventually retroact and then terminate in one big black hole, a new singularity that could develop into a new big bang and a new universe. Nature has taught us that it is very good at renewing itself.

  • Additi

    HoHow do I join the event on hangout?

    • Pierre Binétruy

      You just have to click on the active links above. You may need a gmail account to join the google hangout link (and ask your questions live), but you do not need anything to watch it using the Youtube link.


  • tony samson

    I have never understood how an interferometer exploiting light waves can have the necessary sensitivity to measure the minute effects (~ 10 t0 -6 or less of the light wavelength) caused by gravity waves. Please explain.

    I asked this question when I took the Gravitation course but received no response.

  • Gary Hunt

    Will the terrestrial and space based LIGO technology be able to detect the end of a black hole as its Hawking Radiation reduces the singularity to zero as as conjectured by Prof Hawking? Or is it more likely that the black hole will disappear with a WIMPer (pun intended!) rather than a big bang (sorry couldn’t resist that one!)? I also suppose it depends on how long it takes for a black hole to get to that stage to be detectable (maybe not one has done so yet)?

  • Martine Adriana

    Super, I’ll not miss it.

  • keith twort

    Double repeat of sound makes it very difficulty to follow

  • keith twort

    Is there any plan to have 4 satellites in a tetrahedron to give a non ambiguous direction?

    • Pierre Binétruy

      This would be better but you have to find orbits around the Sun such that four satellites following these orbits make a tetrahedron throughout their journey around the Sun.


  • Paul Hugill

    Could you clarify something for me? I had imagined that the collision of two black holes would produce ripples in the spacetime fabric, rather like a stone being thrown into a pond. This would create multiple ripples, strong at first then gradually dying out. So if the first wave is missed there will always be others coming to be detected. But the LIGO result implies that there was only one wave, If so, how lucky was that for a one-off event many millions of years ago should be detected by a device which only came onstream recently. Or have I got it wrong? Will LIGO detect further waves in the future associated with the first event? How far apart would the subsequent waves be?
    Many thanks

    • Pierre Binétruy

      This system of two black holes has been emitting gravitational waves for millions of years but remember that the frequency is increasing: until a fraction of a second before merging, the frequency was not in the frequency window of LIGO. This is why LIGO could not detect them. In fact, it was for the last 10 years in the frequency window of the LISA space mission: if LISA had been on the sky, it would have detected the same binary system. After the merge, it is different: very soon, oscillations of the final black hole cease and there is then no longer a displacement of mass. Gravitational waves quickly stop to be emitted.
      Were we lucky to see this event? Well yes of course, and no. No, because it seems that there are passing gravitational waves of this type every now and then (because of the number of potential sources): this is why another one was observed on December 26. One estimates that there are at least ten events of this type per year.
      Best wishes,

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