Results 271 to 300 of 500
Thread: Physics In the Playground
-
2012-05-22, 09:47 AM (ISO 8601)
- Join Date
- Apr 2009
- Location
- Germany
Re: Physics In the Playground
what tidal effects? Of course, this depends a lot on the radius of the orbit and the actual mass of the star, I assume.
We are not standing on the shoulders of giants, but on very tall tower of other dwarves.
Spriggan's Den Heroic Fantasy Roleplaying
-
2012-05-22, 10:44 AM (ISO 8601)
- Join Date
- Feb 2007
- Location
- Manchester, UK
- Gender
Re: Physics In the Playground
There would be no greater tidal effects at a typical orbital distance than there were before--as said above, a uniform sphere behaves as if all its gravitational attraction acted from a point at the centre, regardless of its size. The reason tidal forces might become significant with a black hole is that it's smaller, so you can get much closer to the thing!
-
2012-05-22, 11:17 AM (ISO 8601)
- Join Date
- Aug 2006
- Location
- Geosynchronous orbit
-
2012-05-22, 11:59 AM (ISO 8601)
- Join Date
- Mar 2011
- Gender
-
2012-05-22, 12:00 PM (ISO 8601)
- Join Date
- Apr 2009
- Location
- Germany
Re: Physics In the Playground
Very often you have binary stars and even a supernova does not do a lot damage to very close nearby stars. After that, the black hole can suck off matter from the companion star.
Which still doesn't answer why the star didn't do that before the supernova?We are not standing on the shoulders of giants, but on very tall tower of other dwarves.
Spriggan's Den Heroic Fantasy Roleplaying
-
2012-05-22, 02:52 PM (ISO 8601)
- Join Date
- Jun 2010
- Location
- Netherlands
- Gender
Re: Physics In the Playground
Sometimes they do. Sometimes binaries are so close to each other they can transfer mass from one to the other.
There's also the evolutionary stage of the stars to consider. The companion of a star that becomes a black hole could enter the red giant stage and increase in size only after formation of the black hole. Then there could be mass transfer only after the black hole has been formed, simply because the other star wasn't large enough before.
-
2012-05-22, 03:12 PM (ISO 8601)
- Join Date
- Aug 2005
- Location
- Mountain View, CA
- Gender
Re: Physics In the Playground
I believe the answer to this one is "actually, it did." The difference is that the matter being sucked off tends to get stuck in a close orbit and slowed down by time dilation instead. With a star instead of a black hole, paths that would have that result around a black hole instead impact the star because the radius of the close orbit is smaller than the star.
The reason accretion disks exist is that black holes are so ridiculously tiny relative to their mass that the matter their gravity sucks in tends to miss the black hole and swing around outside of it. If the entire planet Earth were collapsed into a black hole, it would be less than a single inch across. Even the Sun would be a mere 6 kilometers (3.8 miles) wide. That presents a target for in-falling matter that requires an incredibly precise trajectory to actually hit rather than merely getting close. Even for the matter that does hit the perfect course or gets slowed down by bumping into other matter in the disk, time dilation approaches infinite at the event horizon. I don't think anything ever does actually cross a black hole's event horizon; instead, matter that enters a black hole does it by being nearby when the event horizon expands, which would happen when a whole lot of matter is really close but not quite there.Like 4X (aka Civilization-like) gaming? Know programming? Interested in game development? Take a look.
Avatar by Ceika.
Archives:
SpoilerSaberhagen's Twelve Swords, some homebrew artifacts for 3.5 (please comment)
Isstinen Tonche for ECL 74 playtesting.
Team Solars: Powergaming beyond your wildest imagining, without infinite loops or epic. Yes, the DM asked for it.
Arcane Swordsage: Making it actually work (homebrew)
-
2012-05-22, 03:18 PM (ISO 8601)
- Join Date
- Feb 2007
Re: Physics In the Playground
Marut-2 Avatar by Serpentine
New Marut Avatar by Linkele
-
2012-05-22, 03:27 PM (ISO 8601)
- Join Date
- Mar 2011
- Gender
Re: Physics In the Playground
These things provide a simple example. On a very small scale. So stuff would eventually swing down into the black hole, but it takes friggin' forever. The coins in this thing hit the center pretty quickly because it's a closed system on a very small scale.
Jude P.
-
2012-05-22, 05:10 PM (ISO 8601)
- Join Date
- Apr 2009
- Location
- Germany
Re: Physics In the Playground
Question remains what would cause a planet in a stable orbit to leave the orbit and move towards the star.
However, there are two things to consider: Massive stars have shorter lifetimes and it gets shorter the greater the mass is. Sometimes only in the tens of millions of years. At that time, there could still be a number of planets in less than stable orbits that will eventually fall into the star or the black hole.
The other is, of course, the supernova event.
No idea if planets can actually survive that without being flung out into space, but if their orbits change, their interaction with each other might then push some of the smaller planets towards the center.
Or maybe as a third option material ejected during the supernova that did not reach a velocity to completely escape gravity and eventually is pulled back in.Last edited by Yora; 2012-05-22 at 05:13 PM.
We are not standing on the shoulders of giants, but on very tall tower of other dwarves.
Spriggan's Den Heroic Fantasy Roleplaying
-
2012-05-23, 01:18 AM (ISO 8601)
- Join Date
- Feb 2007
- Location
- Manchester, UK
- Gender
-
2012-05-23, 07:02 PM (ISO 8601)
- Join Date
- Jul 2010
- Location
- Kitchener/Waterloo
- Gender
Re: Physics In the Playground
This is a bit inaccurate. While an object that falls into a black hole indeed slows to a standstill from the point of view of an outside observer, from the point of view of the object itself the transition from outside to inside the event horizon is perfectly smooth and feasible, and once inside it takes a finite (set, only dependent on black hole mass) amount of time for the object to reach the singularity.
Lord Raziere herd I like Blasphemy, so Urpriest Exalted as a Malefactor
Meet My Monstrous Guide to Monsters. Everything you absolutely need to know about Monsters and never thought you needed to ask.
Trophy!
-
2012-05-23, 07:52 PM (ISO 8601)
- Join Date
- Aug 2005
- Location
- Mountain View, CA
- Gender
Re: Physics In the Playground
Like 4X (aka Civilization-like) gaming? Know programming? Interested in game development? Take a look.
Avatar by Ceika.
Archives:
SpoilerSaberhagen's Twelve Swords, some homebrew artifacts for 3.5 (please comment)
Isstinen Tonche for ECL 74 playtesting.
Team Solars: Powergaming beyond your wildest imagining, without infinite loops or epic. Yes, the DM asked for it.
Arcane Swordsage: Making it actually work (homebrew)
-
2012-05-24, 08:18 AM (ISO 8601)
- Join Date
- Apr 2009
- Location
- Germany
Re: Physics In the Playground
Is it more or less accurate to treat the event horizon as a uniform object? Does it matter how the mass is distributed inside it in regard to object in orbit?
We are not standing on the shoulders of giants, but on very tall tower of other dwarves.
Spriggan's Den Heroic Fantasy Roleplaying
-
2012-05-24, 11:02 AM (ISO 8601)
- Join Date
- Jul 2010
- Location
- Kitchener/Waterloo
- Gender
Re: Physics In the Playground
Looks like I misunderstood your statement then, my apologies.
There's actually a theorem that it specifically doesn't matter how mass is distributed inside the event horizon. Outside the event horizon you only need to know three things about a black hole to know everything about it: mass, charge, and angular momentum.Lord Raziere herd I like Blasphemy, so Urpriest Exalted as a Malefactor
Meet My Monstrous Guide to Monsters. Everything you absolutely need to know about Monsters and never thought you needed to ask.
Trophy!
-
2012-05-24, 11:26 AM (ISO 8601)
- Join Date
- Apr 2009
- Location
- Germany
Re: Physics In the Playground
What about the axis? Since black holes do have acretion disks, they have to spin. And acretion disks are the result of the difference in "effective gravity" above the equator and the poles of a spinning body. So it can't be entirely uniform.
We are not standing on the shoulders of giants, but on very tall tower of other dwarves.
Spriggan's Den Heroic Fantasy Roleplaying
-
2012-05-24, 11:37 AM (ISO 8601)
- Join Date
- Sep 2008
- Gender
-
2012-05-24, 12:05 PM (ISO 8601)
- Join Date
- Jul 2010
- Location
- Kitchener/Waterloo
- Gender
Re: Physics In the Playground
Lord Raziere herd I like Blasphemy, so Urpriest Exalted as a Malefactor
Meet My Monstrous Guide to Monsters. Everything you absolutely need to know about Monsters and never thought you needed to ask.
Trophy!
-
2012-05-24, 07:24 PM (ISO 8601)
- Join Date
- Mar 2007
Re: Physics In the Playground
Anyone know how to calculate miller indices in a cubic lattice when you only know the first incident bragg reflection angle? I feel like there should be something simple but nothing seems to work without knowing at least the wavelength.
Blarg.
-
2012-05-29, 10:54 PM (ISO 8601)
- Join Date
- Mar 2011
- Gender
Re: Physics In the Playground
1. Why do planets and asteroid belts mostly form in a rough plane around their stars? Or do they? That's the impression I've been given.
2. Light is a wave. How does it travel in a vacuum? Is it that wave-particle duality business?Jude P.
-
2012-05-30, 01:29 AM (ISO 8601)
- Join Date
- Feb 2007
- Location
- Manchester, UK
- Gender
Re: Physics In the Playground
1. Conservation of momentum. The initial cloud of gas and dust that collapsed to form the solar system was spinning slowly, and as it collapsed, it began to spin faster and flatten out into a plane, thus resulting in the arrangement we see today.
2. Not 100% sure about this one, but I'm pretty sure that just because something is a wave doesn't mean it has to be travelling through a medium. Light is an electromagnetic wave, and unlike waves in water, you don't need some luminiferous ether for those to travel in!
-
2012-05-30, 01:43 AM (ISO 8601)
- Join Date
- Apr 2009
- Gender
-
2012-05-30, 11:18 AM (ISO 8601)
- Join Date
- Mar 2006
- Location
- 3 inches from yesterday
- Gender
Re: Physics In the Playground
Thanks Uncle Festy for the wonderful Ashling Avatar
I make music
-
2012-05-30, 12:40 PM (ISO 8601)
- Join Date
- Mar 2011
- Gender
Re: Physics In the Playground
Okay, that makes perfect sense.
Okay, we're back into where Physics lost me. I got a 28 on one of these exams. (It was a B-, though, so at least nobody else in the class got it either.)Jude P.
-
2012-05-30, 12:50 PM (ISO 8601)
- Join Date
- Jul 2010
- Location
- Kitchener/Waterloo
- Gender
Re: Physics In the Playground
Here's a (maybe) better way to think about it: all that a wave is, mathematically speaking, is a particular sort of behavior in space and time: something goes up and down as time passes, and the disturbance travels along in some direction in space.
The thing that goes up and down could be something obvious and physical, like the height of water. It could also be any other number that can go up and down, though. Sound waves are waves of pressure, and involve pressure going up and down. You could have a wave of temperature, with temperature going up and down. All that light is is a wave of electric field going up and down (plus magnetic field going up and down in a perpendicular direction, but that detail isn't important for the analogy). It doesn't need a medium to travel through because electric and magnetic fields don't need a medium to travel through.Lord Raziere herd I like Blasphemy, so Urpriest Exalted as a Malefactor
Meet My Monstrous Guide to Monsters. Everything you absolutely need to know about Monsters and never thought you needed to ask.
Trophy!
-
2012-05-30, 01:13 PM (ISO 8601)
- Join Date
- Mar 2011
- Gender
-
2012-06-10, 09:03 PM (ISO 8601)
- Join Date
- Mar 2011
- Gender
Re: Physics In the Playground
Guys what is time?
Jude P.
-
2012-06-10, 10:04 PM (ISO 8601)
- Join Date
- Feb 2008
- Location
- center of earth
-
2012-06-10, 10:12 PM (ISO 8601)
- Join Date
- May 2009
-
2012-06-11, 08:17 AM (ISO 8601)
- Join Date
- Apr 2009
- Location
- Germany