Friday, April 26, 2013

New accurate gravitational wave data

A new pulsar and his white dwarf pal confirm Einstein's GR again

The 1993 Nobel prize in physics was given for the discovery of a binary pulsar, i.e. a rotating neutron star, whose orbiting frequency was changing exactly as predicted by the general theory of relativity which says that accelerating masses emit gravitational waves, lose energy, speed up the orbiting rate, and gradually collapse onto their companion.

Now, 20 years later, astronomers found a new strange couple called PSR J0348+0432 that allows us to run these tests more accurately than ever before:
A Massive Pulsar in a Compact Relativistic Binary (preprint)

Science Daily, TG Daily, Wall Street Journal, Google News
7,000 light years away from Earth, there is a pulsar with a companion, a white dwarf, that make the job.

The pulsar has radius 6 miles, weighs as two Suns (the white dwarf has 1/6 of a solar mass), and spins 25 times a second (like some movies). The orbital period of the binary system is 2.5 hours and is getting accelerated. The acceleration reduces the orbital period just by 8 microseconds a year but it's apparently possible to measure such changes accurately using telescopes.

I would say that the agreement makes it insanely unlikely that the confirmation of gravitational waves by the 1993 binary pulsar was a coincidence. There are many indirect, theoretically loaded ways to become certain that gravitational waves have to exist. However, I would say that their existence has been demonstrated by direct experiments, too. Of course that we don't really need more of such confirmations but it's still moderate fun to see when they work.

It would be much more new to detect the gravitational waves as the actual vibrations of the LIGO device or another one of this kind. It has to happen at some point. In my opinion, the importance of that moment won't be in yet another confirmation of classical general relativity which we don't really need anymore but in acquiring a new type of eyes that allow us to look in the outer space and "see" things that are much less clear than classical general relativity.


  1. Cute, I like this :-)

  2. Maybe I'm missing something here, but does the video give a good illustration of real physics? The gravity waves propagate with a velocity of c, I reckon - so far so good. Thus the propagating gravity can be illustrated by a spiral in one plane. But then, how can the opposing cones depicting the magnetic field, emanating from neutron star (pulsar), move instantaneous - shouldn't they make spirals?

  3. Dear Henrik, there is nothing wrong about opposing sides of a neutron star that move "in unison". No actual information is being propagated by the speed exceeding the speed of light anywhere.

  4. Hmm.. I may be wrong here, but you are saying that it is an accurate portrayal that the emission beams moves like a solid rod? I am not questioning that they move in unison, but why not a spiral like this: ??.. I presume the gravity waves illustrated in the orbiting plane travel at lightspeed, so how can the emission beams travel at superluminal velocity?

  5. Oh, I see, you talk about the emissions, not just about the axis of rotation. Yes, they will span a spiral-like curve in the spacetime.

    On the other hand, photons arranged into straight lines in the spacetime are possible, too. Various unphysical points may "look like" something is moving by the speed exceeding c.

  6. That is a great way to visualize - anyway to me - that nature is not discrete even if information is quantized. Anyway I must turn to my classical world now.

  7. Yeah me too :-)...

  8. It is always nice to keep checking the truth again and again...

  9. Shanon this not the truth, it the effective truth in the Wilsonial sense. Underneath in high energy regimes you must seek for new dof. Don't forget that GR is not renormalizable:-)

  10. Kicking Lubos ButtMay 1, 2013, 4:58:00 PM

    Lubos says: "In my opinion, the importance of that moment won't be in yet another confirmation of classical general relativity."
    Oh shut has an experiment that can be done to show that Special Relativity fails

  11. Kicking Lubos ButtMay 1, 2013, 5:07:00 PM

    Yes, delete the comment, because you know deep down that you are a chicken who never even understood special relativity! We corresponded chickened out then abuse everyone, call them crackpots but me you kneel before me and
    sit dog...good dog (communicating with you in the kind of language you like to use)...bad chicken for deleting..