ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Reply
Old 11th April 2019, 12:02 PM   #81
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by phunk View Post
You're talking about it as if gravity is a thing that bends space and also exerts a force on things with mass but you don't know how it affects massless particles?

You have a basic misunderstanding here. Gravity isn't what bends spacetime, gravity IS bent spacetime. Mass and energy bend spacetime, and gravity is the effect that bent spacetime has on everything within it. Nothing needs to have mass to be affected by gravity. Anything moving in spacetime (which is everything) is affected by the shape of spacetime.
oh, maybe you can clarify the acceleration of gravity to me, then?
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 12:31 PM   #82
phunk
Illuminator
 
phunk's Avatar
 
Join Date: Aug 2007
Posts: 3,930
Originally Posted by Skeptic Ginger View Post
It's not 'my' quote, it's the person I quoted. That's an important but not so subtle conceptual difference.

Here you are in the one area I have confidence in your knowledge. I fail to see any conceptual difference between 'correct' and 'accurate'. I'm sure it has some meaning to you, but I'm not seeing it. Perhaps you might find another way to articulate what you are getting at?


Traveling through space that that is shaped by gravity still requires the photon be affected by the gravity affecting the shape. Otherwise it makes no sense. What changes in space fabric that is somehow an effect of gravity which causes an actual structural change?
Originally Posted by Belz... View Post
oh, maybe you can clarify the acceleration of gravity to me, then?
It's complicated and I can't do the math. But think of it this way. Imagine 2 objects just floating in empty space next to each other, moving forward through time but not space. In a flat (unbent) 4 dimensions of spacetime, they are tracing parallel lines, not moving closer to each other over time, just moving straight ahead into the future. But since mass bends spacetime slightly, paths straight into the future aren't parallel anymore, they are bent towards each other. Because of the bend in spacetime, a tiny bit of their motion forward in time is now actually motion towards each other instead. The larger the mass, the more spacetime is bent, and the more "forward in time" becomes "forward towards that big mass over there".
phunk is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 01:02 PM   #83
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by phunk View Post
It's complicated and I can't do the math. But think of it this way. Imagine 2 objects just floating in empty space next to each other, moving forward through time but not space. In a flat (unbent) 4 dimensions of spacetime, they are tracing parallel lines, not moving closer to each other over time, just moving straight ahead into the future. But since mass bends spacetime slightly, paths straight into the future aren't parallel anymore, they are bent towards each other. Because of the bend in spacetime, a tiny bit of their motion forward in time is now actually motion towards each other instead. The larger the mass, the more spacetime is bent, and the more "forward in time" becomes "forward towards that big mass over there".
And it becomes ever closer every X unit of time because the bend gets more pronounced the closer you get?
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward



Last edited by Belz...; 11th April 2019 at 02:12 PM.
Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 01:03 PM   #84
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by Darat View Post
I'm not known for liking videos as dumps of information or evidence but in this case I make an exception,.wait until you can view the video, it's a brilliant explanation at a "I like science" level.


Not much new, but I didn't know there was a zone between the EH and the visible accretion disc.
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward



Last edited by Belz...; 11th April 2019 at 01:10 PM.
Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 02:10 PM   #85
HansMustermann
Penultimate Amazing
 
Join Date: Mar 2009
Posts: 15,059
Originally Posted by Belz... View Post
And it becomes ever closer every X unit of time because the bend gets more pronounced the closer you get?
Indeed. Though it's not just space getting more deformed "every X unit of time". Time itself is deformed too. One hour of your time, might be just 59 minutes of the other object's time. Or just one minute, if it's close to a black hole. Think "Interstellar", really.

Though you don't even need GR for time and space to behave funnily. It already does that in SR.

E.g., here's a trivial example, just to illustrate what even simple SR can do to space and time:

Let's say we have a spaceship that's about 20m long and a space hangar that's 10m long, with gates (force fields, bulkheads, whatever you wish) at both ends. The ship moves at about 0.866c, which is lucky, because the Lorentz factor is 2 at that speed.

So, if I'm the guy sitting at a console controlling the hangar doors, the ship is only 10m long in my frame. You know, 20m divided by a Lorentz factor of 2. That means that at a given moment, I can have both doors close for an instant at the same time, and have a 10m ship inside a 10m hangar.

That was the trivial part.

Now, if you're the pilot of the ship, your ship is still 20m long, but it's my hangar that's moving. So my hangar is only 5m long in YOUR frame.

So now think about what happens in your frames if I do close both gates for a moment, like I described before, with your ship fully fitting inside my hangar for a moment. In your frame the ship is 20m long and my hangar is 5m long. How CAN a 20m ship fit inside a 5m hangar in your frame?

The answer is, it doesn't. In your frame, the two gates don't close at the same time. First one closes briefly in front of your ship, then the second one closes behind your ship, when your aft and respectively bow pass by those respective points.

So basically things aren't even happening at the same time in two different frames.

GR just makes the whole thing even weirder, really.
__________________
Which part of "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn" don't you understand?

Last edited by HansMustermann; 11th April 2019 at 02:15 PM.
HansMustermann is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 02:16 PM   #86
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by HansMustermann View Post
The answer is, it doesn't. In your frame, the two gates don't close at the same time. First one closes briefly in front of your ship, then the second one closes behind your ship, when your aft and respectively bow pass by those respective points.
...and by the time the aft of the ship passes the aft part of the hangar, the front doors are open and the rest of ship has passed the hangar (from the pilot's perspective)?
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 02:20 PM   #87
HansMustermann
Penultimate Amazing
 
Join Date: Mar 2009
Posts: 15,059
But in terms of GR, you can think of the following experiment. Let's say I go skydiving on the moon, so no air to screw that up. I jump from a moving craft. And I film myself during the descent with a selfie stick.

Well, if I look at the film, in that frame (ok, chart), it's not even that I'm moving in a straight line. I'm not moving at all. I'm fixed at, say, 2m from the origin of that coordinate system, which is the camera. My acceleration and speed are exactly zero for the duration of the whole jump.

A guy sitting on the moon filming it too, however, will see me quite clearly accelerating. And moving on a parabolic path too.

The difference is really just a coordinate transform between the two coordinate systems.
__________________
Which part of "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn" don't you understand?
HansMustermann is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 02:21 PM   #88
HansMustermann
Penultimate Amazing
 
Join Date: Mar 2009
Posts: 15,059
Originally Posted by Belz... View Post
...and by the time the aft of the ship passes the aft part of the hangar, the front doors are open and the rest of ship has passed the hangar (from the pilot's perspective)?
Yep.
__________________
Which part of "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn" don't you understand?
HansMustermann is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 02:47 PM   #89
The Great Zaganza
Maledictorian
 
The Great Zaganza's Avatar
 
Join Date: Aug 2016
Posts: 7,494
Best case scenario:
Through bio- and Cybertechnologie, I live until I can take a small ship to a Black Hole, and drop in backwards so I can see the entire universe age and die before I do.
__________________
Opinion is divided on the subject. All the others say it is; I say it isnít.
The Great Zaganza is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 04:03 PM   #90
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by HansMustermann View Post
Yep.
Reality is messed up.
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 04:09 PM   #91
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by HansMustermann View Post
The difference is really just a coordinate transform between the two coordinate systems.
Yesh I know, but it's hard to get the brain to see reality as fundamentally different than what we normally perceive.

Originally Posted by The Great Zaganza View Post
Best case scenario:
Through bio- and Cybertechnologie, I live until I can take a small ship to a Black Hole, and drop in backwards so I can see the entire universe age and die before I do.
Why, Tish! That's French!!!
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 05:15 PM   #92
HansMustermann
Penultimate Amazing
 
Join Date: Mar 2009
Posts: 15,059
Well, it is, but in this case it shouldn't be that hard to grasp the basic concept. I mean, the same happens with Newtonian gravity. I'm still at rest in the frame of my camera on a selfie stick and accelerating in the frame of the camera on the ground, and it's still a coordinate transform that links the two. GR just gives you some more complex equations for how to do that.
__________________
Which part of "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn" don't you understand?
HansMustermann is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 07:12 PM   #93
arthwollipot
Observer of Phenomena
 
arthwollipot's Avatar
 
Join Date: Feb 2005
Location: Location, Location
Posts: 61,223
It's been a good week for science.
__________________
Self-described nerd. Pronouns: He/Him
arthwollipot is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 07:32 PM   #94
rjh01
Gentleman of leisure
Tagger
 
rjh01's Avatar
 
Join Date: May 2005
Location: Flying around in the sky
Posts: 24,454
Originally Posted by The Great Zaganza View Post
Best case scenario:
Through bio- and Cybertechnologie, I live until I can take a small ship to a Black Hole, and drop in backwards so I can see the entire universe age and die before I do.
Tip. Make sure it is a big one. If it is too small the tidal forces will tear you apart first. And make sure the black hole does not suck in any mass or the radiation may kill you first.
__________________
This signature is for rent.
rjh01 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 07:51 PM   #95
arthwollipot
Observer of Phenomena
 
arthwollipot's Avatar
 
Join Date: Feb 2005
Location: Location, Location
Posts: 61,223
And by the way - this is front page on the Guardian website today, above the fold:

Katie Bouman: the 29-year-old whose work led to first black hole photo

I've seen one person post a meme today saying "everyone's posting the picture, but no-one's talking about Katie Bouman". That hasn't been my experience. I think I've seen at least as much about her as I have of the actual picture itself.

Oh, and by the way, the black hole memes are coming thick and fast.









__________________
Self-described nerd. Pronouns: He/Him
arthwollipot is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 11th April 2019, 08:53 PM   #96
rjh01
Gentleman of leisure
Tagger
 
rjh01's Avatar
 
Join Date: May 2005
Location: Flying around in the sky
Posts: 24,454
Originally Posted by The Great Zaganza View Post
Best case scenario:
Through bio- and Cybertechnologie, I live until I can take a small ship to a Black Hole, and drop in backwards so I can see the entire universe age and die before I do.
No need. I have had a word with God's employee and he has created a YouTube of what it is like to be near a black hole. Of course it is 360 degrees so you should go to the site itself.

https://www.youtube.com/watch?v=JDNZBT_GeqU
__________________
This signature is for rent.
rjh01 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 02:09 AM   #97
Roboramma
Penultimate Amazing
 
Roboramma's Avatar
 
Join Date: Feb 2005
Location: Shanghai
Posts: 12,080
Originally Posted by Belz... View Post
Yesh I know, but it's hard to get the brain to see reality as fundamentally different than what we normally perceive.
All of the apparent paradoxes of relativity start to become much more intuitive when you look at things from the perspective of spacetime instead of just space and time.

Draw a spacetime diagram of the ladder paradox (I skimmed, I think you guys were talking about that one) and everything seems perfectly sensible.
__________________
"... when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."
Isaac Asimov
Roboramma is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 04:52 AM   #98
W.D.Clinger
Illuminator
 
W.D.Clinger's Avatar
 
Join Date: Oct 2009
Posts: 3,564
Originally Posted by phunk View Post
It's complicated and I can't do the math. But think of it this way. Imagine 2 objects just floating in empty space next to each other, moving forward through time but not space. In a flat (unbent) 4 dimensions of spacetime, they are tracing parallel lines, not moving closer to each other over time, just moving straight ahead into the future. But since mass bends spacetime slightly, paths straight into the future aren't parallel anymore, they are bent towards each other. Because of the bend in spacetime, a tiny bit of their motion forward in time is now actually motion towards each other instead. The larger the mass, the more spacetime is bent, and the more "forward in time" becomes "forward towards that big mass over there".
Here's an example that might be easier for some people to visualize: Suppose the earth were entirely covered by a perfectly smooth sheet of ice. Two skaters stand side by side at the north pole. Both push off, both heading directly south, both gliding, without changing direction. Assume there is no friction, so they continue to glide in what they consider to be a straight line.

Because they were separated by a few inches at the start, "south" is a slightly different direction for one than for the other. The further they go, they farther apart they become, with maximum separation when they reach the equator. From the equator to the south pole, they become closer together. At the south pole, the two skaters collide, just as lines of longitude converge at the south pole.

If the skaters didn't know about the curvature of the icy surface on which they are gliding, they would attribute their diminishing separation and eventual collision to some mysterious force. They might even invent a name for that force, such as "gravity".

What does that have to do with acceleration? Nothing, really, because neither skater perceives any sideways acceleration, just as a ball thrown upwards into the air from earth doesn't perceive any acceleration between the time of its release and time of its eventual collision with the earth. Yet the people who throw balls have adopted a coordinate system in which they are constantly being accelerated upward by the earth on which they stand, so they do perceive acceleration, yet they perversely attribute acceleration to things in free fall (which do not experience acceleration) while regarding themselves and other objects that are stationary with respect to the earth's surface (because of the upward acceleration those objects do experience) as unaccelerated.

That's how the geometry of spacetime creates perceptions of gravity and (false) notions of acceleration.
W.D.Clinger is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 04:59 AM   #99
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by W.D.Clinger View Post
Here's an example that might be easier for some people to visualize: Suppose the earth were entirely covered by a perfectly smooth sheet of ice. Two skaters stand side by side at the north pole. Both push off, both heading directly south, both gliding, without changing direction. Assume there is no friction, so they continue to glide in what they consider to be a straight line.

Because they were separated by a few inches at the start, "south" is a slightly different direction for one than for the other. The further they go, they farther apart they become, with maximum separation when they reach the equator. From the equator to the south pole, they become closer together. At the south pole, the two skaters collide, just as lines of longitude converge at the south pole.

If the skaters didn't know about the curvature of the icy surface on which they are gliding, they would attribute their diminishing separation and eventual collision to some mysterious force. They might even invent a name for that force, such as "gravity".
Oooohhhhh! I see.

Quote:
What does that have to do with acceleration? Nothing, really, because neither skater perceives any sideways acceleration, just as a ball thrown upwards into the air from earth doesn't perceive any acceleration between the time of its release and time of its eventual collision with the earth.
Wait, what? If you throw me in the air I'll feel acceleration, four times. And that last one will hurt.
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 05:14 AM   #100
Roboramma
Penultimate Amazing
 
Roboramma's Avatar
 
Join Date: Feb 2005
Location: Shanghai
Posts: 12,080
Originally Posted by Belz... View Post
Wait, what? If you throw me in the air I'll feel acceleration, four times. And that last one will hurt.
You experience acceleration when you are thrown upward, but that acceleration is due not to gravity but to electromagnetism. Similar for the acceleration you feel when you hit the ground.

Neglecting air resistance you don't feel any other acceleration.
__________________
"... when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."
Isaac Asimov
Roboramma is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 05:15 AM   #101
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by Roboramma View Post
Neglecting air resistance you don't feel any other acceleration.
Well except for my organs moving inside my body. That's a feeling. But you're right, the feeling isn't because of gravity, but, what, electron degeneracy pressure?
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 05:23 AM   #102
Roboramma
Penultimate Amazing
 
Roboramma's Avatar
 
Join Date: Feb 2005
Location: Shanghai
Posts: 12,080
Originally Posted by Belz... View Post
Well except for my organs moving inside my body. That's a feeling. But you're right, the feeling isn't because of gravity, but, what, electron degeneracy pressure?
Your organs are moving with respect to each other because of a wave transmitted through your body (through the electromagnetic interactions between the atoms that make you up) from whatever it was that threw you into the air. And yeah, that force was also fundamentally electromagnetic interactions between the atoms that make it up, and you.

ETA: To be clear, I'm only trying to clarify what you actually already agreed to, that the feeling you have in that case is not due to acceleration due to gravity.
__________________
"... when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."
Isaac Asimov

Last edited by Roboramma; 12th April 2019 at 05:26 AM.
Roboramma is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 05:42 AM   #103
Steve001
Graduate Poster
 
Join Date: Feb 2007
Posts: 1,380
M87 Black Hole Size Comparison
Steve001 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 05:44 AM   #104
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Ok so that's the M87 one. Where's the SagA* picture?
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 08:05 AM   #105
Steve001
Graduate Poster
 
Join Date: Feb 2007
Posts: 1,380
Originally Posted by Belz... View Post
Ok so that's the M87 one. Where's the SagA* picture?
I don't know. Go take a look around.
Steve001 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 08:11 AM   #106
The Great Zaganza
Maledictorian
 
The Great Zaganza's Avatar
 
Join Date: Aug 2016
Posts: 7,494
I've seen it, but can't find it again.
odd.
__________________
Opinion is divided on the subject. All the others say it is; I say it isnít.
The Great Zaganza is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 08:18 AM   #107
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by Steve001 View Post
I don't know. Go take a look around.
Thanks, you've been a dear.

Stupid discussion forums.
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 08:32 AM   #108
autumn1971
Master Poster
 
Join Date: Jan 2007
Posts: 2,698
Originally Posted by Belz... View Post
Thanks, you've been a dear.

Stupid discussion forums.
Look towards Sagittarius.

You will need to squint.
__________________
'A knave; a rascal; an eater of broken meats; a base, proud, shallow, beggardly, three-suited, hundred-pound, filthy, worsted-stocking knave; a lily-livered, action-taking knave, a whoreson, glass-gazing, superservicable, finical rogue;... the son and heir of a mongral bitch: one whom I will beat into clamorous whining, if thou deniest the least syllable of thy addition."'
-The Bard
autumn1971 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 08:58 AM   #109
Belz...
Fiend God
 
Belz...'s Avatar
 
Join Date: Oct 2005
Location: In the details
Posts: 80,704
Originally Posted by autumn1971 View Post
Look towards Sagittarius.

You will need to squint.
If I squint hard enough maybe I'll see beyond the visible spectrum and through all that dust!
__________________
Master of the Shining Darkness

"My views are nonsense. So what?" - BobTheCoward


Belz... is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 10:30 AM   #110
PSXer
New Blood
 
Join Date: Jul 2015
Posts: 3
Veritasium's "First image of a black hole!" video on Youtube is the only place I've seen the image of Sgr A*. I can't link directly because apparently I don't have enough posts.

That does raise the question though, if that's the only place I can find it, where did he get the image originally?
PSXer is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 10:33 AM   #111
phunk
Illuminator
 
phunk's Avatar
 
Join Date: Aug 2007
Posts: 3,930
Originally Posted by PSXer View Post
Veritasium's "First image of a black hole!" video on Youtube is the only place I've seen the image of Sgr A*. I can't link directly because apparently I don't have enough posts.

That does raise the question though, if that's the only place I can find it, where did he get the image originally?
YouTube Video This video is not hosted by the ISF. The ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
I AGREE


The image says "simulated" and he mentions that they didn't release it yet.

Last edited by phunk; 12th April 2019 at 10:35 AM.
phunk is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 10:47 AM   #112
PSXer
New Blood
 
Join Date: Jul 2015
Posts: 3
Ah, so it's not the actual picture. I guess I missed that when I watched the video originally. The thumbnail (at least when you google for it) shows both black holes with no explanation.

As to the XKCD comic about scale, did Randall get it wrong? From what I'm reading the dark 'shadow' is 2.5 times larger than the event horizon, but the XKCD comic scale seems to be based on the dark part being the event horizon. Voyager 1 should be a lot closer to the halfway point between the center and edge of the shadow.
PSXer is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 11:22 AM   #113
Elagabalus
Illuminator
 
Join Date: Dec 2013
Posts: 4,096
Originally Posted by Steve001 View Post


Pfffffft! Super massive Black Hole, my arse!!
Elagabalus is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 12th April 2019, 07:45 PM   #114
Travis
Misanthrope of the Mountains
 
Travis's Avatar
 
Join Date: Mar 2007
Posts: 23,830
If you aren't on Twitter you might have missed that sexist trolls are claiming that either Katie actually did no work and stole the credit of male colleagues or that she faked the image. Either way they are pushing the idea that women have no place in science and have to either steal others work or make crap up.


Fortunately her male colleagues are stepping up and quashing these notions which has led to a new line of attack that this kind of science is a waste of resources because "who cares?"
__________________
"Because WE ARE IGNORANT OF 911 FACTS, WE DEMAND PROOF" -- Douglas Herman on Rense.com
Travis is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th April 2019, 10:50 AM   #115
Jack by the hedge
Safely Ignored
 
Jack by the hedge's Avatar
 
Join Date: Oct 2009
Posts: 9,304
Another day, another reminder not to bother signing up for Twitter.
Jack by the hedge is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th April 2019, 10:52 AM   #116
phunk
Illuminator
 
phunk's Avatar
 
Join Date: Aug 2007
Posts: 3,930
I'm on twitter, and never see things like that. What you see depends entirely on who you follow.
phunk is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th April 2019, 02:55 PM   #117
Ziggurat
Penultimate Amazing
 
Ziggurat's Avatar
 
Join Date: Jun 2003
Posts: 42,775
Originally Posted by Belz... View Post
They do accelerate if they have mass, however, so they're not only following the curve; something else is acting upon them.
They accelerate relative to a frame where the planet or sun is stationary. But in GR, such a frame is not inertial. You donít need to apply a real force to get something to accelerate in a non-inertial frame (for example, centrifugal force in a rotating frame). Being in a non-inertial frame always introduces fictitious forces, and gravity is no different. The only complication is that in GR, there is no such thing as a global inertial reference frame, only local ones (ie, free falling frames).
__________________
"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law
Ziggurat is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 14th April 2019, 01:09 AM   #118
Travis
Misanthrope of the Mountains
 
Travis's Avatar
 
Join Date: Mar 2007
Posts: 23,830
Originally Posted by phunk View Post
I'm on twitter, and never see things like that. What you see depends entirely on who you follow.
If you follow the scientists that were heading this mission it will not take long, regrettably, to find this incredibly terrible take on what is actually a super cool accomplishment.
__________________
"Because WE ARE IGNORANT OF 911 FACTS, WE DEMAND PROOF" -- Douglas Herman on Rense.com
Travis is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 14th April 2019, 05:43 PM   #119
arthwollipot
Observer of Phenomena
 
arthwollipot's Avatar
 
Join Date: Feb 2005
Location: Location, Location
Posts: 61,223
Originally Posted by Travis View Post
If you aren't on Twitter you might have missed that sexist trolls are claiming that either Katie actually did no work and stole the credit of male colleagues or that she faked the image. Either way they are pushing the idea that women have no place in science and have to either steal others work or make crap up.


Fortunately her male colleagues are stepping up and quashing these notions which has led to a new line of attack that this kind of science is a waste of resources because "who cares?"
There's quite a long post being shared around on Facebook which describes exactly how Katie Boulger contributed. I've shared it, but the original post was made by someone named Misty S. Boyer, and it's got citations.
__________________
Self-described nerd. Pronouns: He/Him
arthwollipot is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 14th April 2019, 06:52 PM   #120
Travis
Misanthrope of the Mountains
 
Travis's Avatar
 
Join Date: Mar 2007
Posts: 23,830
Yeah the trolls countered by making about a dozen instagram accounts in her name and in each them had this "confession" where "she" admitted a woman couldn't do such complicated work and stole the glory from the men. They were reported quickly and I think all the imposters are now down.
__________________
"Because WE ARE IGNORANT OF 911 FACTS, WE DEMAND PROOF" -- Douglas Herman on Rense.com
Travis is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 04:37 AM.
Powered by vBulletin. Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.