JamesDJarvis
First Post
Turanil said:
Black Holes do have a size. If our sun could somehow become a black hole it'd be a couple of miles accross
http://curious.astro.cornell.edu/question.php?number=160
Questions about the Speed of Light
- Thread starter Turanil
- Start date
Black Holes do have a size. If our sun could somehow become a black hole it'd be a couple of miles accross
http://curious.astro.cornell.edu/question.php?number=160
Henry
Autoexreginated
Turanil said:
Even scarier thought: If Black Holes have near-infinite mass, and are a singularity, and act the same way that a vessel travelling near lightspeed would act, then what if Black Holes we discover through indirect observation in the universe are actually extraterrestrial spacefaring beings, who are simply travelling from point A to point B at or near the speed of light?
If they're travelling to see us, then our planet will be long gone before they get here.
WayneLigon
Adventurer
Henry said:if Black Holes we discover through indirect observation in the universe are actually extraterrestrial spacefaring beings, who are simply travelling from point A to point B at or near the speed of light?
I may have to use that. Cool idea!
Or, eventually every civilization gets around to discovering the way to 'get around' the speed of light and builds an FTL engine. A black hole is what happens when the researcher turns the working model on for the first time
This would also solve our Fermi Paradox.
Black Pharaoh
First Post
As an aside Mr. Hawking postulates that due to the Heisenberg Uncertainty Principle it is possible for subatomic particles, which have mass, to travel faster than the speed of light within the swartchchilde(sp?) radius of a black hole.
Ankh-Morpork Guard
First Post
And now I want to run a d20 Future game. Curse you, Henry, I'm running far more games than I need to already.Henry said:Even scarier thought: If Black Holes have near-infinite mass, and are a singularity, and act the same way that a vessel travelling near lightspeed would act, then what if Black Holes we discover through indirect observation in the universe are actually extraterrestrial spacefaring beings, who are simply travelling from point A to point B at or near the speed of light?
If they're travelling to see us, then our planet will be long gone before they get here.
azmodean
First Post
RE: what happens to photons that we observe.
It's a good question, with a rather mundane answer. The photon delivers its energy to the substance that it impacts (a retinal cell or the active portion of a photodetector) and ceases to exist. Or in other words, it is translated into physical motion.
In other, other words: You know that nice, warm feeling of sunlight on your skin? That's photons dying you jerk! How can you be happy about that?
/would someone just think of the photons?
It's a good question, with a rather mundane answer. The photon delivers its energy to the substance that it impacts (a retinal cell or the active portion of a photodetector) and ceases to exist. Or in other words, it is translated into physical motion.
In other, other words: You know that nice, warm feeling of sunlight on your skin? That's photons dying you jerk! How can you be happy about that?
/would someone just think of the photons?
Pbartender
First Post
IAAParticle Accelerator Technician...
More or less right. If a ship traveled at an average of about 90% the speed of light, it would take about 4.5-5 years to reach Alpha Centauri, and a little over 2 years of apparent time would have passed for the passengers on the ship.
Problem #1: Anything that travels at the speed of light cannot have mass.
Problem #2: Anything that travels at the speed of light only travels at the speed of light; there's no slowing down or speeding up.
Setting those aside, we delve into Sci-fi speculation. As you approach the speed of light, time slows down to the passengers. The limit of that equation, as Michael Morris said, approaches, but never quite reaches, zero. The assuption would be, therefore, that time stands still for whatever object is travelling at the SoL (an appropriate acronym, as we will find out shortly).
So, the SoL drive gets activated, the ship travels to its destination, and slows back down to 'normal' speeds. From the viewpoint of the SoL passengers, as soon as the ship reaches the SoL, time stops and resumes, once it begins slowing down. The entire journey at SoL does not exist for the passengers; to them, it is as if the ship itself instantly jumped from one point in space to another.
Sounds a lot like sci-fi 'hyperdrive/jumpgate/warp drive' type stuff, doesn't it? The main difference, is that during that instant transport moment, time is still passing for the rest of the universe... The passengers not only instantly arrive 4 light years distant, but 4 irreversable years into the future.
Now, here's the tricky part... When you travel anywhere, you have to know when to turn off the engines and stop. But, if you are travelling at the SoL, time is frozen. Not only can you not percieve the appropriate time to stop the SoL engine, but you simply couldn't act to turn off, even if you wanted to. What would be need would be some sort of relativistic 'net' at the end of your journey to 'catch' the SoL ship, turn its SoL engine off, and slow it down to 'normal' speeds. Of course, given the astronomical distances traveled at the SoL, you'd need a 'net' that was AUs across to even have a slight chance of hitting it from parsecs away. Remember, once you are SoL, you also can't adjust your course.
This is why, intentional or not, Science Fiction appropriately uses Jump Gates, Wormholes, Hyperspace, Warp Drives and other means of making extradimensional shortcuts through which you travel at normal speeds, rather than actually travelling as fast or faster than light.
Conceptually, it's 'easier'... and universally legal... to bring the mountain to Mohammed, so to speak.
The closest thing to the SoL travel you suggest would actually be Star trek transporters, with the exception that you'd need a recieving transporter to arrive at your estination.
In regards to the non-SoL point of view, he would be frozen in mid-step, and would finish the step as soon as the ship slows down.
From the SoL point of view, he lifts his foot as the ship leaves Sirius and in less than an instant, the ship is approaching Betelgeuse as he puts his foot down.
Yup... From the point of view of the photon itself, that sounds about right.
Undoubtedly there is. Figure it out, and they'll give you a Nobel Prize.
Turanil said:
More or less right. If a ship traveled at an average of about 90% the speed of light, it would take about 4.5-5 years to reach Alpha Centauri, and a little over 2 years of apparent time would have passed for the passengers on the ship.
Turanil said:
Problem #1: Anything that travels at the speed of light cannot have mass.
Problem #2: Anything that travels at the speed of light only travels at the speed of light; there's no slowing down or speeding up.
Setting those aside, we delve into Sci-fi speculation. As you approach the speed of light, time slows down to the passengers. The limit of that equation, as Michael Morris said, approaches, but never quite reaches, zero. The assuption would be, therefore, that time stands still for whatever object is travelling at the SoL (an appropriate acronym, as we will find out shortly).
So, the SoL drive gets activated, the ship travels to its destination, and slows back down to 'normal' speeds. From the viewpoint of the SoL passengers, as soon as the ship reaches the SoL, time stops and resumes, once it begins slowing down. The entire journey at SoL does not exist for the passengers; to them, it is as if the ship itself instantly jumped from one point in space to another.
Sounds a lot like sci-fi 'hyperdrive/jumpgate/warp drive' type stuff, doesn't it? The main difference, is that during that instant transport moment, time is still passing for the rest of the universe... The passengers not only instantly arrive 4 light years distant, but 4 irreversable years into the future.
Now, here's the tricky part... When you travel anywhere, you have to know when to turn off the engines and stop. But, if you are travelling at the SoL, time is frozen. Not only can you not percieve the appropriate time to stop the SoL engine, but you simply couldn't act to turn off, even if you wanted to. What would be need would be some sort of relativistic 'net' at the end of your journey to 'catch' the SoL ship, turn its SoL engine off, and slow it down to 'normal' speeds. Of course, given the astronomical distances traveled at the SoL, you'd need a 'net' that was AUs across to even have a slight chance of hitting it from parsecs away. Remember, once you are SoL, you also can't adjust your course.
This is why, intentional or not, Science Fiction appropriately uses Jump Gates, Wormholes, Hyperspace, Warp Drives and other means of making extradimensional shortcuts through which you travel at normal speeds, rather than actually travelling as fast or faster than light.
Conceptually, it's 'easier'... and universally legal... to bring the mountain to Mohammed, so to speak.
The closest thing to the SoL travel you suggest would actually be Star trek transporters, with the exception that you'd need a recieving transporter to arrive at your estination.
Turanil said:
In regards to the non-SoL point of view, he would be frozen in mid-step, and would finish the step as soon as the ship slows down.
From the SoL point of view, he lifts his foot as the ship leaves Sirius and in less than an instant, the ship is approaching Betelgeuse as he puts his foot down.
Turanil said:
Yup... From the point of view of the photon itself, that sounds about right.
Turanil said:
Undoubtedly there is. Figure it out, and they'll give you a Nobel Prize.
Last edited:
IAAPhysicist:
An additional item to consider -
Light can be described as both particle and wave. The trick is to choose which description makes sense in a given situation.
A photon is not a "thing" in the normal sense, as it is different from most other "things" in the universe. In this case, it is far more sensible to consider it as a wave - merely the propagation of energy through a field in space. If it isn't an object, you don't consider it's subjective clock. Of course time doesn't pass for a thing when the thing does not exist
As for a couple of other items -
Black holes do or don't have size, depending upon what you are talking about. The "event horizon", the volume from which light cannot escape, has a definite size. The singularity at the center, however, does not have size in the conventional sense.
An object may be able to move faster than lightspeed within the Schwartzchilde Radius, but the point is rather moot. The Universe at large recieves no information about what is going on inside the black hole. If it does move faster than light, we'd never hear about it. Tree falling in a forest when nobody can hear it, and all that....
An additional item to consider -
Light can be described as both particle and wave. The trick is to choose which description makes sense in a given situation.
A photon is not a "thing" in the normal sense, as it is different from most other "things" in the universe. In this case, it is far more sensible to consider it as a wave - merely the propagation of energy through a field in space. If it isn't an object, you don't consider it's subjective clock. Of course time doesn't pass for a thing when the thing does not exist
As for a couple of other items -
Black holes do or don't have size, depending upon what you are talking about. The "event horizon", the volume from which light cannot escape, has a definite size. The singularity at the center, however, does not have size in the conventional sense.
An object may be able to move faster than lightspeed within the Schwartzchilde Radius, but the point is rather moot. The Universe at large recieves no information about what is going on inside the black hole. If it does move faster than light, we'd never hear about it. Tree falling in a forest when nobody can hear it, and all that....
Storminator
First Post
One thing to consider about i: The discoverers were NOT looking for solutions to x^2+1=0. They were looking for solutions to x^3+a*x+b=0, in cases where there's a real solution, and two imaginary solutions.
Would it make it any easier to know that i^i is not only defined, but if I recall correctly, it's a real number?
They were looking for solutions to x^3+a*x+b=0 with three real solutions. There are formulae for solving these equations, but in certain cases it requires taking the root of a negative number. In those cases the formula failed, yet it was known that there were real solutions.
So some guy just kept churning thru the computations, but left this little placeholder (i) where the negative roots were, until they cancelled each other out later in the computations.
PS
p.s.- I think the italic i inside parentheses is the weirdest looking construction...
Ankh-Morpork Guard
First Post
You know, it would be an interesting day if we came to learn that the core concepts and ideas of physics we cling to end up being wrong and that the universe really isn't logical or rational at all...with Cthulhu and the Elder Gods out there waiting on us.
