When he put together his theories of relativity, Einstein made a series of predictions. Some were confirmed just a few years later, but scientists are still working to confirm others. And one of the most fascinating is the concept of gravitational waves. As massive objects move in space, they send out ripples across the Universe that actually distort the shape of matter. Experiments are in place and in the works to detect these gravitational waves as they sweep past the Earth.

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Just a minor technical point, but early in this episode, you took a moment to announce something like, "And now a word from our sponsor." But your blurb for audible.com was missing.

Hi everyone,

Just got round to listen to this episode and I've got a question please. Does the universe expansion affect gravitational waves in anyway? e.g. do gravitational waves get red shifted?

Thanks,
Amro

I could be mistaken but I believe I have heard Pamela state that gravitational effects are felt instantly in one show and travel at the speed of light in another. Am I confusing something or do I need a new battery for my neurons?

Oh man... great question... now I have something else to hurt my brain with until someone answers it. I'm still wondering how we can have gravity waves when there is no gravity, only the warping of space... or at least that's what I thought Albert told me... his accent was a little thick.

Light and gravity travel at the same speed as Einstein predicted.

Redshift? Don't know, but you're right, it's a great question.

Try this link, I haven't had time to study it, but it looks like it has what you're looking for.

http://en.wikipedia.org/wiki/Redshift

Cheers.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

I think this article is referring to light being redshifted by high gravity objects (among other things) rather than gravity itself being 'redshifted' by expansion, so - still a good question.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

Ok, so I followed the redshift link, read a bit there, went on to gravitational redshifting, ended up at frame-dragging which I recall Pamela mentioning in at least one show. And now I have another question...

I gather that frame-dragging is a very slight effect, but could you theoretically have a black hole so massive that it twisted space like a candy-cane, and if so, what would happen in that region of space. Would space be damaged (ok, dumb question, but I have to ask)? What would light traveling through a region like this look like?

I'm not sure if this is relevant, but - is it the case that there are fundamental differences between gravity waves and light waves? For example, gravity waves are thought to propogate from black holes right? Light waves can't escape black holes. So maybe the comparison to red-shifted light is invalid in some way? I can't help but feeling though, that the wave-length of gravity waves must increase in expanding space. Then I try to consider gravitons, higgs fields, inverse square law, blah blah...

...meltdown.

Someone pass the burritos?

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

You almost had me on that one. Light can be shifted due to gravity but it can also be shifted because of your speed relative to the light. I imagine the same could be said for gravity waves. And because of that, I'm going to go out on a limb and say, yes, gravity waves can be red-shifted.

I think for this, look no further than supermassive black holes. Wikipedia would be a good place to start again:

http://en.wikipedia.org/wiki/Supermassive_black_hole

I haven't found anything online at all about redshifted gravity, except a few forums which are stumped too. You could try the other BAUT forums, some pretty clever dudes (and dudettes) hang out there. Post back here if you find something. Dunno if Amro found anything?

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

Finally found something.

It's an arcticle comparing the GWB (Gravitational Wave Background) to the CMB (Cosmic Microwave Background) and is pretty cool in it's own right... and it says:

"...the GWB would be redshifted, like the CMB. But because of the GWB's earlier provenance, the reshifting would be even more dramatic: the energy (and frequency) of the waves would be downshifted by 24 orders of magnitude."

http://www.aip.org/pnu/2007/split/809-1.html

It's a pretty obscure reference, but for my money gravity is redshifted by expansion.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

Cool article. I was glad to see that real scientists agree with my crackpot theories for once.

and this:

"..the GW spectrum will be redshifted. All energy redshifts in an expanding universe, and these waves redshift as photons of the CMB do.

Gravitational Waves from the Big Bang
Prof Juan Garcia-Bellido
http://scitizen.com/screens/blogPage...553803696467cf

It would be a pretty dull world without us crackpots... my wife thinks its cute. Sometimes.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

Many thanks for this, Steve. That explains it. I thought that the universe expansion should have some effect on GV!

Cheers

No problem Amro - great question.

I'm pretty excited about the GWB... kinda like the CMB but a trillionth of a second after the Big Bang (or the Big Bang itself depending how you look at it)... wow!

They say Einstein wanted to 'know the mind of God'... I reckon this is getting pretty close.

LISA will be one to follow. Hope it works!

http://lisa.jpl.nasa.gov/#

Steve

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

What an acronym you've got there! Reminds me all too much of the current POTUS and his "nucular" weapons... oh, how I HATE that pronunciation...

Oh, sorry 'bout the OffTopic.

In the podcast, it's mentioned that two pulsars that gravitate around each other and also approach each other. It is said that they are getting closer and closer because the system is loosing energy and that energy is used to create gravitational waves.

Now this bring me back to basic physics which talks about all the fun and provocative ways to lose energy: friction, air resistance, and so on.

Apparently, to build a perpetual motion system you need something like frictionless material in a void. But even if you had that, the system still wouldn't work because it's losing energy in the form of gravity ways.

Does that make sense ?

We can speculate all we want but is it not true that right now, in March of 2008, not a single gravity wave has been measured yet?

Gravity waves have been seen in the interactions between massive objects orbiting one another, like pulsars. They haven't been detected here on Earth with LIGO or any other detector.

__________________
Fraser Cain
Publisher
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Whoa! Pulsars surf on gravity waves! That is too cool! Dick Dale and Vangelis could get together to make the music for that!

I know you're busy but if you could find time to post a reference, I would love to read it.

P.S. Astronomy Cast RAWKS! You and Pamela are doing the wonderful work.