Thursday, September 08, 2005

Having Respect for Nature

I personally cannot get over Nature. Just on earth, we are witnesses to the awe-inspiring variety of life, the beauty of everything from rainbows to cloud formations, to the Grand Canyon and scenic beauty of the Alaskan wilderness. We have seen the awesome power of Nature last week in the Gulf and with the tsunami, and we will see such fury unleashed again some day.

Many of us lose track of what happens outside of the earth. I was just reminded of this after reading a short article from Scientific American. Astronomers have directly measured a pulsar (i.e. neutron star, a superdense ball of neutrons that just missed becoming a black hole, and one teaspoon of this creature would weigh multiple tons on earth!) that is moving at over 1000 kilometers per second. Talk about impressive. To put this in perspective, human-made space probes, the fastest devices we have built, may cruise through space at several tens of kilometers per second. We have a long way to go to catch up with Nature!


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James said...

Ah, but to the neutron star, it is us that's moving 1000 kilometers per second. :-)

vonny said...

Hi James,

Either way, it is pretty fast. What amazing energy levels we're talking about!

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Erica said...

Shouldn't something that's that high in energy and moving so quickly create a really strong "wake" of gravity waves? I know that gravitons are extremely difficult to detect, but it seems like a situation like this one would be ideal for observing them. Do you know if there are any gravity wave experiments focused on this particular neutron star?

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Chris Beem said...


unfortunately, gravitational radiation is emitted by accelerating masses, and not just those moving at high speeds. As a result, we look to systems such as black hole mergers and binary pulsars in order to observe the effects of gravitational radiation.

In fact, the observation of just such a binary pulsar system seems to have confirmed the prediction of GR for energy loss due to gravitational radiation.

The phenomenon is something like the emmission of electromagnetic radiation by accelerating charged particles, like you learned in a course on E&M.

remember that to think about the dynamics of objects in unaccelerated motion, you can imagine considering the physics in the rest frame of the object. One would not expect the emmission of gravitational waves from this neutron star simply because of our rapid motion relative to it :)

vonny said...

Good point, Chris. It is analogies like this that Einstein thought would lead him to a unified theroy of gravity and EM. One thing to consider: If a star could ever move at relativistic speeds, the mass-energy density increases, and the result should be an increase in the gravitational field (classically) or more significant warping of spacetime (relativistically). It is fun to think about!