I'm no astronomer but I was reading about the missing mass of galaxies. Correct me if I'm wrong, but as I understand it, the idea is that the outer stars of a galaxy should be moving slower around the galaxy then what they appear to moving. The only explanation for this unexpected speed is that there must be more mass in the galaxy the we can currently detect.
Could this not be explained by time dilation? As you move further from the center of a galaxy (super massive blackhole) time would speed up wouldn't it? Is this effect not enough to cause the extra "speed" of the outer stars?
Also, in deep space between galaxies or clusters of galaxies how much faster is time going? Could this be the cause of universal expansion. In that, the time between galaxies is moving faster.
I've tried to use my Google fu but have not yet found these answers. All I can find is dark energy and dark matter. Can anyone point me to some links that discuss time dilation on these scales.
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Feel free to reply to any comment by clicking the "Reply" button.First of all, God job on the thinking,
and while I am no expert in astrophysics, I can comment on time dilation. as that is something we can measure.
But first, Dark matter is just a name for unknown, or missing matter that seem to be missing based on the speed of galaxies and systems we observe, Its a theory not a fact. Dark Matter explains one thing, But creates a new problem, something else is pushing the matter away - Dark energy, our second don't know
So how about Time dilation effects.
Time dilation is really cool, and really happens, and its a measurable, repeatable part of gravity science, the most famous experiment involved 2 jets traveling in different directions, and each having a cesium beam clock, on landing both clocks were shown to have experienced different time effects due to gravitational effects and , they had different times. But the effect was miniscule. Large gravitational objects like Black holes can create time dilation both at the event horizon, and again as we move away, but the effects fall off at an extremely rapid inverse square rate, so the effect of a supermassive black whole at the centre of the galaxy, will have almost no effect by the time you reach the outer edges of the galaxy, Like our home planet. Its there, but too small to measure. So i'm afraid its not going to provide enough effect.
Ironically I am certain, that if the big bang is real, then the event would have produced a white hole, and gravometric waves would have created massive time dilations during the first few seconds of the universe, so that it did not all age at the same rate, which is yet another issue in terms of dating events. (but I digress)
The speed of the stars is not the problem Starts can travel at any speed in empty space, Its the gravitational forces that keep them anchored. ... Of course we are assuming that gravity is the only glue at work ..... This Dark matter, name of missing matter to explain the gravational anomoly.
Since you find this so interesting, May I recommend the Youtube channel, PBS space time.
search PBS Space Time, I tried to link, but it just keeps grabbing the video instead.
I'm a huge fan, and find the science really good value, while not overcomplicated or conceited (but its very conventional science) and a lot of ... we don't really know.
I think you might like it.
I love that people are thinking, and while you claim you are not an astronomer, If your fascinated, looking, reviewing and postulating, then you are an amateur one, and that's where some of our best discoveries have been made. Keep thinking, and have a long look out there, It's mind blowing.
The idea of quantum physics that the universe we perceive may not actually be the universe we live in - the holographic universe, may even lead us much stranger answers.
Enjoy your pursuit of knowledge.
The_Q
Level 7
Apr 11, 2019
2
Thanks! I'll check it out.
Yes, quantum mechanics a whole other mind f***. Lol
BTW, time dilation is working right here in Colorado. The National Bureau of Standards has an atomic clock in Boulder, Colorado. It runs s
fractionally faster than the Naval Observatory's atomic clock in Washington, DC.
The scientific explanation is that the Naval Observatory's atomic clock is deeper in the gravity well than the one in Boulder. The rest of Colorado, however, believes that Boulder has always lived in another dimension.
Astronomers in the first part of the 20th century caught this. It took 100 inch telescopes to get the first photos of galaxies. They counted the stars, estimated their mass and ran the orbital equations. There was no way the orbital masses added up to make sense. So they invented "dark matter." If they added enough dark matter they could get the answer they wanted.
There were a couple of problems with dark matter. First, enough dark matter to balance the equations took something like 85% of the matter in the universe.
The second problem was radio astronomy. You see, the early astronomers looked at the glass plate negatives. They assumed dark matter was just something that didn't show up on black and white negatives. Then they discovered radio astronomy, and they found out that even clouds of gas at almost absolute zero generate radio waves. So they searched for the dark matter with radio telescopes. And they didn't find it.
But dark matter HAD to exist, at least in the minds of astronomers. So they had to assume that dark matter produced no radio waves. So they were proposing an entirely different kind of matter. Their basic theories about the structure of the universe depended on it. And they still do today.
Dark matter has not been created in accelerator labratories. It is unlike any other matter in the universe, not emmiting any radiation. But it HAS to exist, so we have spent billions looking for it.
I don't think they'll ever find it.
timon_phocas
Level 9
Apr 10, 2019
1
Why do you think that they will never find it? What do you think the cause of stars rotating around a super massive black hole at the same speed regardless of their distance is?
I tend to reason by way of history. This reminds me, in a broad way, of Ptolemaic Astronomy. It was heliocentric. All planets moved in perfect circles around the earth. But there was a problem, this didn't explain movement of planets in the sky (how a planet would suddenly shift from eastern to western parts of the sky).
So they proposed a fix. The planets still described perfect circles around the earth. But they also described perfect, smaller circles around the circumference of their larger orbits.These were called epicycles.
It was an elegant solution. They were even able to calculate future solar eclipses with it. No mean feat in the age of Roman Numerals and purely integer math It worked. Sort of. Every few years it became innacurate. Then they had to jigger the epicycles to get it to accord with observed phenomena.
Ptolemaic astronomy only worked sporadically because their fundamental assumptions about the universe were wrong. We're in the same situation with modern astronomy and dark matter. Dark matter is today's epicycle.
@timon_phocas Fantastic explanation & reasoning here. And you are right, as I tell my students, Just because something works does not make it right.
In science as in life, What works may turn out to be total rubbish. After all, Its garbage can, not garbage can't
@timon_phocas
Well they found the so called god-particle. But with dark matter they're looking for the ninja-particle and they'll never find it.
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