Consequences of the Existence of Gravitational Waves?

[Pennybags]

TL;DR Summary

What are some of the expected and unexpected consequences of the existence of gravitational waves?

I'd like to see some of the consequences of the existence of gravitational waves (both expected and unexpected), in laymen's terms so a simpleton like me can understand and relate to them.

A possible consequence that I thought of (and I'm sure someone will correct me if I'm wrong) is that photons might lose appreciable energy over vast distances; i.e. additional redshift beyond that caused by relative motion of source and observer.

I derived that from a line near the end of this article:
https://www.desy.de/user/projects/Physics/Relativity/SR/light_mass.html
"The energy and momentum of light also generates curvature of spacetime, so general relativity predicts that light will attract objects gravitationally."

This would seem to indicate that photons (according to my simple understanding, at least theoretically) generate minuscule gravitational wakes as they travel.

So this leads to additional questions that occur to me: Is there a lower limit to the magnitude of a gravitational wave, or to the amount of mass and speed required to produce one? I realize that we've only just begun to be able to detect the most energetic of such waves, but what do the theories and mathematics say about the other end of the spectrum? If photons indeed produce gravitational wakes, how much redshift would such energy loss entail, relative to simple doppler shift, in photons we observe originating from, say, several billion light years away? Would this additional source of redshift (if it exists) lead to any revision of our ideas about how fast the universe is expanding?

 

[Nugatory]

A possible consequence that I thought of (and I'm sure someone will correct me if I'm wrong) is that photons might lose appreciable energy over vast distances; i.e. additional redshift beyond that caused by relative motion of source and observer.

I derived that from a line near the end of this article:
https://www.desy.de/user/projects/Physics/Relativity/SR/light_mass.html
"The energy and momentum of light also generates curvature of spacetime, so general relativity predicts that light will attract objects gravitationally."

Yes, but...

This would seem to indicate that photons (according to my simple understanding, at least theoretically) generate minuscule gravitational wakes as they travel.

No, for several reasons. First, the bit of text that you've quoted is about light, not photons. They're not the same thing. Second, gravitational waves are only produced by some patterns of movement (the technical term is "non-zero quadrupole moment") and light passing by is not one of them.

So no, light does not lose energy through the emission of gravitational waves.

 

[Ibix]

A consequence of gravitational wave emmission is that orbiting bodies (in principle) spiral inwards and collide. This effect was measured by Hulse and Taylor years ago, based on measurement of a binary pulsar. The effect is tiny for most systems so, with the exception of fairly extreme cases, it's very much lost in the noise (and other effects may well make them spiral outward). Related is that non-symmetric black holes will emit gravitational radiation until they are characterised entirely by their charge, mass, and angular momentum. Another consequence is that gravitational wave detectors react to something, rather than just sitting silent. And signatures of gravitational waves in the early universe may show up in the CMB.

I'm not sure we really have unexpected consequences yet. Predicted effects aren't unexpected, by definition, and our observation hasn't thrown up anything inconsistent with prediction yet.