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re: The case against dark matter
Posted on 5/7/18 at 10:48 pm to DavidTheGnome
Posted on 5/7/18 at 10:48 pm to DavidTheGnome
quote:
Nah because again that would imply an actual thing reaching out from the center of mass of said objects and pulling it towards each other.
Or that there is a gravitational field like magnetic substances have magnetic fields. Either way, a field is being created whether it be a distortion of spacetime or not that expands beyond the actual physical dimensions of the object (mass) itself.
quote:
Gravity is an effect, the warp of spacetime is the cause.
Yet spacetime has no matter. No clear defined nature. Nothing. It's literally just what we imagine to be the intertwined "fabric" of space and objects seem to want to follow it. If that's the case, then we really need to define what "spacetime" is and show examples of objects seemingly wanting to follow this "spacetime."
quote:
Why spacetime is warped by mass is another story, I have no idea there.
Which is why I have such a hard time with accepting general relativity as a legitimate explanation for the phenomena of gravity.
For objects (mass) to then be inclined to "follow" that distortion/warping of spacetime is my biggest problem. As we can tell, there is nothing actually there being warped, no matter, nothing, just the idea of space and time intermeshed into something we're calling "spacetime," so why would an object in space (mass) be influenced by that?
We've tested general relativity by putting gyroscopes into space but it fails to address exactly what the guiding force that the bending of spacetime provides.
Then, if we consider the fact that the entire universe, everything inside of it, is moving away in every which direction, is that from the Big Bang or is some other force at play here? We've already observed galaxies spinning far faster than they should and have deduced that to there being a presence of "dark matter" which provides gravity without being able to be detected and not interacting with physical light. Then there's dark energy, that apparently counteracts gravity and is causing the universe to expand.
If dark energy is causing the universe to expand, how does that fit into general relativity, besides just to account for an expanding universe?
1
Posted on 5/7/18 at 10:49 pm to ell_13
He didn’t though. He made fantastic models that get really close (close enough for everyday use) and invented calculus in the process but it was derived from lots of data crunching and never touched on the underlying reason behind it like Einstein.
And I’m not discounting the work he did, he was one of the greatest scientists of all time. But Einstein had a totally different kind of breakthrough than Newton.
And I’m not discounting the work he did, he was one of the greatest scientists of all time. But Einstein had a totally different kind of breakthrough than Newton.
This post was edited on 5/7/18 at 10:53 pm
Posted on 5/7/18 at 10:53 pm to DavidTheGnome
quote:I didn't say he did. I just said it was his whole life's work to determine "why".
He didn’t though. He made fantastic models that get really close (close enough for everyday use) and invented calculus in the process but it was derived from lots of data crunching and never touched on the underlying reason behind it like Einstein.
I digress. It was just another BS post from you. 
Posted on 5/7/18 at 10:54 pm to DavidTheGnome
How does this effect our recruiting class and why should I give a frick if not
Posted on 5/7/18 at 10:54 pm to DavidTheGnome
quote:What made einstein special was what he was able to create and predict without even being able to prove it with observations yet. Much of that didn't come till later.
Einstein had a totally different kind of breakthrough than Newton.
Posted on 5/7/18 at 10:55 pm to ell_13
What was the reason Newton gave for why in terms of gravity. He gave us the laws but those explained what was happening, not why.
This post was edited on 5/7/18 at 10:58 pm
Posted on 5/7/18 at 10:58 pm to DavidTheGnome
Can one of you whizkids read what I said above and just call me a dumbass already?
Posted on 5/7/18 at 11:02 pm to rmnldr
Not sure how to answer
I think your premise is that there is nothing to spacetime but I don’t think that is accurate. It being a framework is something, even if nothing is there.
I think your premise is that there is nothing to spacetime but I don’t think that is accurate. It being a framework is something, even if nothing is there.
Posted on 5/7/18 at 11:07 pm to ell_13
This is all very inspirational and yet confusing. I think I can follow what is being said here, but isn’t that the fun of it? No one can really explain what is going on, yet we can all theorize. So what we do know is that bodies have magnetic fields. So like magnets wouldn’t they push and pull and not “fall” as if space/time was a fabric like the gif that gnome posted?
Posted on 5/7/18 at 11:12 pm to DavidTheGnome
quote:
I think your premise is that there is nothing to spacetime but I don’t think that is accurate. It being a framework is something, even if nothing is there.
How can we tell there's a framework then? At least we can observe gravitational effects from things like dark matter and dark energy. We can't observe any discernible effects from spacetime besides Einstein basically telling us that mass affects spacetime and spacetime therein affects mass.
Posted on 5/7/18 at 11:18 pm to rmnldr
We see those effects such as the Einstein ring on page 1. Or the first proven evidence I believe was an observation of a star that was actually behind the sun, but the sun's gravity was such that the light bent around it. I think you may be thinking spacetime is something different than what we'd ordinarily just call space and it's not, it just has this additional dimension of time added because we are traveling through it as well.
Posted on 5/7/18 at 11:43 pm to DavidTheGnome
quote:
We see those effects such as the Einstein ring on page 1. Or the first proven evidence I believe was an observation of a star that was actually behind the sun, but the sun's gravity was such that the light bent around it
Couldn't those Einstein rings be easily explained by refraction through the atmosphere(s) of planets or galaxies at a whole?
quote:
I think you may be thinking spacetime is something different than what we'd ordinarily just call space and it's not, it just has this additional dimension of time added because we are traveling through it as well.
And the only observable example of this is through Einstein rings and that seems to be easily deduced to it being refraction.
Posted on 5/8/18 at 12:43 am to rmnldr
This is a gif showing observation of Sagittarius A*, thought to be a supermassive black hole at the center of the Milky Way and the stars orbiting around it, starting in 1991 and ending in 2006.
If gravity bends spacetime, and light is influenced by that spacetime to create an "Einstein ring," so why is there no gravitational lensing (Einstein ring) when S2 (which is travelling at something like 2% of lightspeed when it approaches the black hole on its 16 year orbit) approaches the black hole?
This is what it should look like based on general relativity:
[/img]
Luckily for us, we're going to be observing the frick out of this little star when it comes close to the black hole again. It's supposed to happen this year but I can't find any specific date for it. All I've seen is mid-2018.
If gravity bends spacetime, and light is influenced by that spacetime to create an "Einstein ring," so why is there no gravitational lensing (Einstein ring) when S2 (which is travelling at something like 2% of lightspeed when it approaches the black hole on its 16 year orbit) approaches the black hole?
This is what it should look like based on general relativity:
[/img] Luckily for us, we're going to be observing the frick out of this little star when it comes close to the black hole again. It's supposed to happen this year but I can't find any specific date for it. All I've seen is mid-2018.
This post was edited on 5/8/18 at 12:44 am
Posted on 5/8/18 at 12:48 am to rmnldr
quote:
refraction
That pic shows a light traveling through a massive stretch of literally nothing, the void of deep space, yet it is still being affected as if it were traveling through something. Therefore there most be something causing that distortion. Since there is no visible matter there for it to be distorted by, gas or atmosphere, then some invisible force must be acting on it. Gravity.
That is what really blows my mind, that particals of light radiation have such infinitesimal mass that it really takes a huge amount of mass to generate that much gravity to cause light to be distorted. Yet there isn't enough visible matter there to meet that threshold. So what is causing it?
Don't know man
Posted on 5/8/18 at 12:52 am to rmnldr
You have a point. I'm sure there's some explanation for why there is no distortion in that gif. Perhaps that isn't a visual of visible light and is instead using radio or infrared imaging therefore won't have an Einstein ring? But idk.
Posted on 5/8/18 at 1:06 am to Sticky37
quote:
That pic shows a light traveling through a massive stretch of literally nothing, the void of deep space, yet it is still being affected as if it were traveling through something. Therefore there most be something causing that distortion. Since there is no visible matter there for it to be distorted by, gas or atmosphere, then some invisible force must be acting on it. Gravity.
Or plasma, dust, etc
Or ~dark matter~
There's a bunch of different things that it could be affected by considering it's a cluster of galaxies with an insane amount of junk flying around through it.
quote:
That is what really blows my mind, that particals of light radiation have such infinitesimal mass that it really takes a huge amount of mass to generate that much gravity to cause light to be distorted. Yet there isn't enough visible matter there to meet that threshold. So what is causing it?
All stars have a large sphere of gravitational fielding around them, if general relativity is correct, and that is simply due to spacetime being warped, we'd have a hell of a lot more examples of Einstein rings. We don't though, and they're extremely rare. If it's simply refraction causing these rings, it would make more sense because the sphere of material (like plasma) that can actually refract light would be much smaller so the necessary angle to see an Einstein ring would be harder/rarer to achieve.
quote:
You have a point. I'm sure there's some explanation for why there is no distortion in that gif. Perhaps that isn't a visual of visible light and is instead using radio or infrared imaging therefore won't have an Einstein ring? But idk.
Very few of the images we ever see from deep space are visible light.
This post was edited on 5/8/18 at 1:07 am
Posted on 5/8/18 at 1:27 am to DavidTheGnome
quote:Wait.
Emergent gravity,” as Verlinde calls it, is the idea that gravity is not a fundamental governance of our universe, but instead a reaction to the makeup of a given environment. Rather than thinking of gravity as a fundamental force, something that “just is,” is it possible that gravity is actually the result of the positions of quantum bodies, similar to the way temperature is derived from the motions of individual particles?
Is this not already a thing?
This is exactly how I've always thought of gravity.
Posted on 5/8/18 at 5:05 am to DavidTheGnome
Car Talk already covered this one in "the Andy Letter".
"Posit the question: Do two people who don't know what they are talking about know more or less than one person who doesn't know what he's talking about?"
In this case it's more than two OTers speculating on dark matter (alert the physicists).
"Posit the question: Do two people who don't know what they are talking about know more or less than one person who doesn't know what he's talking about?"
In this case it's more than two OTers speculating on dark matter (alert the physicists).
quote:
One person will only go so far out on a limb in his construction of deeply hypothetical structures, and will often end with a shrug or a raising of hands to indicate the dismissability of his particular take on a subject. With two people, the intricacies, the gives and takes, the wherefores and why-nots, can become a veritable pas-de-deux of breathtaking speculation, interwoven in such a way that apologies or gestures of doubt are rendered unnecessary.
Posted on 5/8/18 at 5:51 am to Tigris
Nice post. Really brought a lot to the thread
Posted on 5/8/18 at 11:10 am to rmnldr
quote:
Or that there is a gravitational field like magnetic substances have magnetic fields. Either way, a field is being created whether it be a distortion of spacetime or not that expands beyond the actual physical dimensions of the object (mass) itself.
No! Recall that gravity is an effect, not a thing. Electromagnetism has a carrier of the force, the photon. There is no carrier for gravity.
quote:
Yet spacetime has no matter. No clear defined nature. Nothing. It's literally just what we imagine to be the intertwined "fabric" of space and objects seem to want to follow it. If that's the case, then we really need to define what "spacetime" is and show examples of objects seemingly wanting to follow this "spacetime."
I recommend Brian Greene's books for you to understand the current view of most scientists views on what spacetime is. You seem to want to understand it based on how classical matter behaves.
Spacetime is what matter and energy of the Universe is expanding into. While we don't know what spacetime is made up of, we know it is something. Something that causes the gravitational effect.
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