by jjohnson » Thu Mar 25, 2010 12:16 am
Galaxies are not at "war" with one another. That is just hyperbole based on the movie title, "Star Wars".
There is no evidence that gravity waves from one are pounding the other. So far there is not a shred of evidence that there even are gravity waves, as reported regularly from the LIGO press announcements. Of course, they put a slight amount of spin (1/2, say) on it by praising themselves for setting "an upper limit on the intensity with which gravity waves could be reaching Earth." In People-speak that means, "we haven't detected any gravity waves yet, but if we get more funding we will keep trying because we really believe that we will, and it pays well."
There are no observations of either stars or galaxies colliding, other than in computer simulations and artists' "interpretations". Do any of you wonder why there are always a lot of artists' interpretations? It's because there are no actual (real; observed; gathered with telescopes of some type and imaged) images of such collisions during their occurrence. If you have such an image, please post. I'm skeptical, but I'll be open-minded about it, of course. The stuff you read about pairs of neutron stars and white dwarfs orbiting about one another in the famous "death spiral to doom", resulting in a supernova or a "black hole" or both, is just all made up. No one has yet filmed such a collision, in our galaxy and certainly not in another one. Effects imputed to this hypothetical scenario? Sure! Anyone can say that this supernova was caused by two white dwarfs (now gone missing!) or too close an encounter with a blalck hole's (unobservable) event horizon, or even because it ate too much lasagna. Observational evidence beats theories to the contrary almost every time, except in astronomy.
Due to the increasing suspicion regarding the accuracy of and assumptions behind the "standard candles" traditionally used to state positively how far away things are, outside our galaxy, and the knowledge that there are other things that cause redshifts besides relative velocity, astronomers can't actually and truthfully state how far away this or that galaxy is unless they are close enough for parallax measurements. - At least not yet. That means that two galaxies with overlapping star fields give a lot of doubt as to whether this star is in this galaxy or in that one, or behind both, etc. Even within our own galaxy only the Hipparcos geometric distance measurements of a large number (a paltry tens of thousands out of some 200 billion) of relatively nearby stars are considered to be accurate.
Calling out the colors associated with the galaxies is a red herring. Those colors are likely to be false colors representing wavelengths that we cannot see in colors which we can. There is nothing wrong with false imaging. It is an invaluable tool for letting us visualize the morphology of an object as caused by different mechanisms at different wavelengths. But it should not be dragged into the "war" as evidence of interactions.
Do the gravity math. The pull between two extended objects on each other can be taken as coming from the center of gravity of each, and it falls off as the inverse square of the distance once you're roughly outside the arms, just as Earth's gravity drops linearly to zero at the center, but falls off as the inverse of the distance outside the surface. Someone figure out what the gravity acceleration is in m/s/s at the one galaxy by the other one, if you can estimate the distance between their centers and their overall masses, over that distance. If the gravity waves are rocking the near side of one galaxy, then how much weaker will their effect be on the far side of the galaxy, 50 to 100 thousand light years away? Do the tidal effects math and wonder why both galaxies don't look like they've been run through a Cuisinart, if the gravity pull is that strong. My guess is that in terms of m/s/s, the answer will have a negative exponent with two significant digits.
My opinion of this companion explanation of what the image is telling us is that it is hogwash (or a trick question to see if we are awake), "...full of sound and fury, signifying nothing. -The Bard of Avon" and am not sure why it was credited and, especially, copyrighted.
Galaxies are not at "war" with one another. That is just hyperbole based on the movie title, "Star Wars".
There is [i]no evidence[/i] that gravity waves from one are pounding the other. So far there is not a shred of evidence that there [i]even are[/i] gravity waves, as reported regularly from the LIGO press announcements. Of course, they put a slight amount of spin (1/2, say) on it by praising themselves for setting "an upper limit on the intensity with which gravity waves could be reaching Earth." In People-speak that means, "we haven't detected any gravity waves yet, but if we get more funding we will keep trying because we really believe that we will, and it pays well."
There are [i]no observations of either stars or galaxies colliding[/i], other than in computer simulations and artists' "interpretations". Do any of you wonder why there are always a lot of artists' interpretations? It's because there are no actual (real; observed; gathered with telescopes of some type and imaged) images of such collisions during their occurrence. If you have such an image, please post. I'm skeptical, but I'll be open-minded about it, of course. The stuff you read about pairs of neutron stars and white dwarfs orbiting about one another in the famous "death spiral to doom", resulting in a supernova or a "black hole" or both, is just all made up. No one has yet filmed such a collision, in our galaxy and certainly not in another one. Effects imputed to this hypothetical scenario? Sure! Anyone can say that this supernova was caused by two white dwarfs (now gone missing!) or too close an encounter with a blalck hole's (unobservable) event horizon, or even because it ate too much lasagna. Observational evidence beats theories to the contrary almost every time, except in astronomy.
Due to the increasing suspicion regarding the accuracy of and assumptions behind the "standard candles" traditionally used to state positively how far away things are, outside our galaxy, and the knowledge that there are other things that cause redshifts besides relative velocity, astronomers can't actually and truthfully state how far away this or that galaxy is unless they are close enough for parallax measurements. - At least not yet. That means that two galaxies with overlapping star fields give a lot of doubt as to whether this star is in this galaxy or in that one, or behind both, etc. Even within our own galaxy only the Hipparcos geometric distance measurements of a large number (a paltry tens of thousands out of some 200 billion) of relatively nearby stars are considered to be accurate.
Calling out the colors associated with the galaxies is a red herring. Those colors are likely to be false colors representing wavelengths that we cannot see in colors which we can. There is nothing wrong with false imaging. It is an invaluable tool for letting us visualize the morphology of an object as caused by different mechanisms at different wavelengths. But it should not be dragged into the "war" as evidence of interactions.
Do the gravity math. The pull between two extended objects on each other can be taken as coming from the center of gravity of each, and it falls off as the inverse square of the distance once you're roughly outside the arms, just as Earth's gravity drops linearly to zero at the center, but falls off as the inverse of the distance outside the surface. Someone figure out what the gravity acceleration is in m/s/s at the one galaxy by the other one, if you can estimate the distance between their centers and their overall masses, over that distance. If the gravity waves are rocking the near side of one galaxy, then how much weaker will their effect be on the far side of the galaxy, 50 to 100 thousand light years away? Do the tidal effects math and wonder why both galaxies don't look like they've been run through a Cuisinart, if the gravity pull is that strong. My guess is that in terms of m/s/s, the answer will have a negative exponent with two significant digits.
My opinion of this companion explanation of what the image is telling us is that it is hogwash (or a trick question to see if we are awake), "...full of sound and fury, signifying nothing. -The Bard of Avon" and am not sure why it was credited and, especially, copyrighted.