I'm not all that convinced of manned Venus missions until long after we've had a base set up on Mars. For one, you actually have a solid object to land on on Mars; one more point of failure (the lifting mechanism) on an atmospheric Venus mission makes it a lot less attractive based on risk alone. I could totally see unmanned platforms being very attractive though; there's been quite some speculation that Venus could support life in its more temperate upper atmosphere, as there's plenty of chemical energy alone to sustain microbial life there and we've found live microbes very high up on Earth.
Curious about that speculation. I assume any pre-microbial macromolecules would periodically cycle into the hellscape of Venus's lower atmosphere and be annihilated, so it's tough to see how evolution gets started.
Mars is cold and terrible, why go all the way there when there's somewhere much more interesting that might have life already there and has places more tolerable to human life*? NASA is apparently thinking about cloud cities on Venus, or at least dirigible research bases.
* Places may not be tolerable to human life
Link brings it back to this page on the thread.
Isn't Venus supposed to be the worst place ever?
It's only the worst place ever if you try living on the surface. Go about 55km up or so, and you have one of the more habitable places in the solar system. Earthlike temperatures, and about 1/2 an atmosphere of pressure of mainly carbon dioxide. And with the outside air being mainly carbon dioxide, an oxygen/nitrogen mix would act as a lifting gas, with about half the lifting power that helium has on Earth.
This is where I feel it necessary to point out that 0.5 atm of CO2 would basically kill a person in minutes. Hypercapnia (excess carbon dioxide) is based on partial pressure of CO2, so that would basically be like breathing air that 50% CO2, regardless of O2 content.
Unrelated to the weirdness of partial pressures, I had a few thought experiments/questions related to black holes you people might be able able to help with:
1. Shouldn't a black hole be a red hole?
Ostensibly a black hole is pure black because no light/electromagnetic radiation can escape (the curve in space time basically bends the light out of any escape path). But based on relativity, the light going into the hole is being subject to time dilation. Even though the light is basically instantaneously past the event horizon because it is simultaneously at its origin and destination from its perspective, for an outside observer the light would be moving slower and slower as it approached the event horizon (or alternatively, some light-emitting rock you threw in the black hole's gravity well would move slower and slower).
Now, I've recently read that as an outside observer, this light should actually be red-shifted and basically become fainter and fainter the closer to the event horizon it is. So shouldn't a black hole actually be red (or, more likely, low-frequency radio waves) from the eons of light remnants that have passed through and basically left a wake of red-shifted light?
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
I feel like at some point before that it would become 'visible' again simply because it doesn't have the mass to bend space-time to prevent the escape of light any more. But maybe there's something I'm missing.
(feel free to let me know if I've jumbled up my thought process here and both of these questions are incomprehensible)
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AbsoluteZeroThe new film by Quentin KoopantinoRegistered Userregular
Mars is cold and terrible, why go all the way there when there's somewhere much more interesting that might have life already there and has places more tolerable to human life*? NASA is apparently thinking about cloud cities on Venus, or at least dirigible research bases.
* Places may not be tolerable to human life
Link brings it back to this page on the thread.
Isn't Venus supposed to be the worst place ever?
It's only the worst place ever if you try living on the surface. Go about 55km up or so, and you have one of the more habitable places in the solar system. Earthlike temperatures, and about 1/2 an atmosphere of pressure of mainly carbon dioxide. And with the outside air being mainly carbon dioxide, an oxygen/nitrogen mix would act as a lifting gas, with about half the lifting power that helium has on Earth.
This is where I feel it necessary to point out that 0.5 atm of CO2 would basically kill a person in minutes. Hypercapnia (excess carbon dioxide) is based on partial pressure of CO2, so that would basically be like breathing air that 50% CO2, regardless of O2 content.
Unrelated to the weirdness of partial pressures, I had a few thought experiments/questions related to black holes you people might be able able to help with:
1. Shouldn't a black hole be a red hole?
Ostensibly a black hole is pure black because no light/electromagnetic radiation can escape (the curve in space time basically bends the light out of any escape path). But based on relativity, the light going into the hole is being subject to time dilation. Even though the light is basically instantaneously past the event horizon because it is simultaneously at its origin and destination from its perspective, for an outside observer the light would be moving slower and slower as it approached the event horizon (or alternatively, some light-emitting rock you threw in the black hole's gravity well would move slower and slower).
Now, I've recently read that as an outside observer, this light should actually be red-shifted and basically become fainter and fainter the closer to the event horizon it is. So shouldn't a black hole actually be red (or, more likely, low-frequency radio waves) from the eons of light remnants that have passed through and basically left a wake of red-shifted light?
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
I feel like at some point before that it would become 'visible' again simply because it doesn't have the mass to bend space-time to prevent the escape of light any more. But maybe there's something I'm missing.
(feel free to let me know if I've jumbled up my thought process here and both of these questions are incomprehensible)
I'll take a whack at this.
1. The light isn't coming back for you to observe it, so no, the hole is not red, it is black.
2. If Hawking Radiation exists, the black hole simply evaporates over time. It never becomes not a black hole, but it will dissipate to nothing eventually.
I'm not all that convinced of manned Venus missions until long after we've had a base set up on Mars. For one, you actually have a solid object to land on on Mars; one more point of failure (the lifting mechanism) on an atmospheric Venus mission makes it a lot less attractive based on risk alone. I could totally see unmanned platforms being very attractive though; there's been quite some speculation that Venus could support life in its more temperate upper atmosphere, as there's plenty of chemical energy alone to sustain microbial life there and we've found live microbes very high up on Earth.
Curious about that speculation. I assume any pre-microbial macromolecules would periodically cycle into the hellscape of Venus's lower atmosphere and be annihilated, so it's tough to see how evolution gets started.
The speculation is more based on the assumption that Venus wasn't a total shithole a few billion years back, and based on fossil records on Earth we had life 3.5 billion years ago. Now, we could have had life earlier but because of bombardment, evidence of that has been erased. Since Mars is known to have had water no less recently than 1 billion years ago, that's a 2.5 billion year overlap for at least two planets with liquid water on their surfaces in our solar system (or rather, two planets capable of supporting life for 2.5 billion years). Due to the local climate, we have not been able to investigate this thoroughly on Venus but it would not be so unreasonable to believe that it as well had a prolonged period of habitability.
Noting from our experiments attempting to kill Tardigrades and microbes in LEO, it's quite possible organisms and spores could have been spread between all three in the early periods of habitability where powerful impacts were a frequent and regular experience. If Venus had anything alive pre-hellscape, it may have adapted and survived to this day in its upper atmosphere. Note that this has interesting implications for the Jovian and Saturnian moons with water, as they would have been contaminated during those billions of years too.
Mars is cold and terrible, why go all the way there when there's somewhere much more interesting that might have life already there and has places more tolerable to human life NASA is apparently thinking about cloud cities on Venus, or at least dirigible research bases.
* Places may not be tolerable to human life
Link brings it back to this page on the thread.
Isn't Venus supposed to be the worst place ever?
It's only the worst place ever if you try living on the surface. Go about 55km up or so, and you have one of the more habitable places in the solar system. Earthlike temperatures, and about 1/2 an atmosphere of pressure of mainly carbon dioxide. And with the outside air being mainly carbon dioxide, an oxygen/nitrogen mix would act as a lifting gas, with about half the lifting power that helium has on Earth.
This is where I feel it necessary to point out that 0.5 atm of CO2 would basically kill a person in minutes. Hypercapnia (excess carbon dioxide) is based on partial pressure of CO2, so that would basically be like breathing air that 50% CO2, regardless of O2 content.
Yeah but no one is suggesting that people actually be outside*. Those conditions would make it easy to keep habitable conditions inside your floating building though. Remember that any building/structure/floating thingy has to interface with its environment. The closer the temperatures and pressures on the outside are to the inside, the easier the job is to maintain inside conditions.
CO2 is useful because like they were saying, an oxygen nitrogen mix (aka air) would basically create lift for you. Making your design requirements even easier. And when you consider the highly acidic conditions below, CO2 is a lot nicer to deal with.
*unprotected by a suit
Al_wat on
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MayabirdPecking at the keyboardRegistered Userregular
I'm not all that convinced of manned Venus missions until long after we've had a base set up on Mars. For one, you actually have a solid object to land on on Mars; one more point of failure (the lifting mechanism) on an atmospheric Venus mission makes it a lot less attractive based on risk alone. I could totally see unmanned platforms being very attractive though; there's been quite some speculation that Venus could support life in its more temperate upper atmosphere, as there's plenty of chemical energy alone to sustain microbial life there and we've found live microbes very high up on Earth.
Curious about that speculation. I assume any pre-microbial macromolecules would periodically cycle into the hellscape of Venus's lower atmosphere and be annihilated, so it's tough to see how evolution gets started.
The speculation is more based on the assumption that Venus wasn't a total shithole a few billion years back, and based on fossil records on Earth we had life 3.5 billion years ago. Now, we could have had life earlier but because of bombardment, evidence of that has been erased. Since Mars is known to have had water no less recently than 1 billion years ago, that's a 2.5 billion year overlap for at least two planets with liquid water on their surfaces in our solar system (or rather, two planets capable of supporting life for 2.5 billion years). Due to the local climate, we have not been able to investigate this thoroughly on Venus but it would not be so unreasonable to believe that it as well had a prolonged period of habitability.
Noting from our experiments attempting to kill Tardigrades and microbes in LEO, it's quite possible organisms and spores could have been spread between all three in the early periods of habitability where powerful impacts were a frequent and regular experience. If Venus had anything alive pre-hellscape, it may have adapted and survived to this day in its upper atmosphere. Note that this has interesting implications for the Jovian and Saturnian moons with water, as they would have been contaminated during those billions of years too.
There was a paper written about this last year which calculated that yes, rocks ejected into space from asteroid impacts on Earth and Mars (when Mars was potentially habitable) could travel to Jupiter, Saturn, and their respective moons, including ones big enough that they could hold bacteria or something like that. The K-T impact would have been big enough to launch some rocks out of Earth orbit as well, though most of the transfer would have been during the Late Heavy Bombardment.
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
Black holes are masses in an infinitely small space so they don't actually need a lot of mass to sustain a themselves. The conditions needsd to be right to create it, but once it gets started it can keep going for a long time. Mass is simply what determines the radius of the black hole's event horizon through the equation R=(2Gm)/(c^2), so a black hole that gets less massive through time just gets a smaller event horizon but otherwise remains unchanged with the same properties as before. It keeps doing this until it reaches the theoretical limit for mass needed to sustain a black hole, which is a Planck mass, or .000022grams (or 6.725x10^16 atoms of gold, give or take a couple hundred trillion atoms). At that moment before the last bit of Hawking radiation is given off, the black hole is around 5.6*10^32 K warm and 1.633*10^-35 m wide (some where around 8.28*10^24 of these smallest black holes equals the diameter of a single gold atom [109 Earths would make up the diameter of the sun, and about 154,700 Earths make up the diameter of the largest known star VY Canis Majoris to really illustrate this size difference]). Once that last bit of radiation is released though, no one knows what happens to the black hole. An idea I'm seeing says that because a black hole at this point, due to quantum mechanics, no longer interacts with the world gravitationally to suck in energy and it no longer emits energy through Hawking radiation that it's essentially an extremely small (nearly as small as the theoretical size of a string in string theory) and stable sub atomic particle, possibly even the WIMP and dark matter itself
I think that's all right. Just some quick math with wiki numbers, so don't yell at me if it wrong
Depends on what you actually consider part of the black hole. You're right, objects inside a gravity well do appear redshifted to a distant observer (gravitational redshift). But at the event horizon, the redshift becomes so great the wavelengths become infinitely long (0 frequency) so it appears perfectly black.
Just remember that half the people you meet are below average intelligence.
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
Black holes are masses in an infinitely small space so they don't actually need a lot of mass to sustain a themselves. The conditions needsd to be right to create it, but once it gets started it can keep going for a long time. Mass is simply what determines the radius of the black hole's event horizon through the equation R=(2Gm)/(c^2), so a black hole that gets less massive through time just gets a smaller event horizon but otherwise remains unchanged with the same properties as before. It keeps doing this until it reaches the theoretical limit for mass needed to sustain a black hole, which is a Planck mass, or .000022grams (or 6.725x10^16 atoms of gold, give or take a couple hundred trillion atoms). At that moment before the last bit of Hawking radiation is given off, the black hole is around 5.6*10^32 K warm and 1.633*10^-35 m wide (some where around 8.28*10^24 of these smallest black holes equals the diameter of a single gold atom [109 Earths would make up the diameter of the sun, and about 154,700 Earths make up the diameter of the largest known star VY Canis Majoris to really illustrate this size difference]). Once that last bit of radiation is released though, no one knows what happens to the black hole. An idea I'm seeing says that because a black hole at this point, due to quantum mechanics, no longer interacts with the world gravitationally to suck in energy and it no longer emits energy through Hawking radiation that it's essentially an extremely small (nearly as small as the theoretical size of a string in string theory) and stable sub atomic particle, possibly even the WIMP and dark matter itself
I think that's all right. Just some quick math with wiki numbers, so don't yell at me if it wrong
Very helpful. Some nice information links to black hole related info like the Schwarzschild radius from the Planck mass info and that atomic-scale micro black hole is neat.
Mars is cold and terrible, why go all the way there when there's somewhere much more interesting that might have life already there and has places more tolerable to human life*? NASA is apparently thinking about cloud cities on Venus, or at least dirigible research bases.
* Places may not be tolerable to human life
Link brings it back to this page on the thread.
Isn't Venus supposed to be the worst place ever?
It's only the worst place ever if you try living on the surface. Go about 55km up or so, and you have one of the more habitable places in the solar system. Earthlike temperatures, and about 1/2 an atmosphere of pressure of mainly carbon dioxide. And with the outside air being mainly carbon dioxide, an oxygen/nitrogen mix would act as a lifting gas, with about half the lifting power that helium has on Earth.
This is where I feel it necessary to point out that 0.5 atm of CO2 would basically kill a person in minutes. Hypercapnia (excess carbon dioxide) is based on partial pressure of CO2, so that would basically be like breathing air that 50% CO2, regardless of O2 content.
Unrelated to the weirdness of partial pressures, I had a few thought experiments/questions related to black holes you people might be able able to help with:
1. Shouldn't a black hole be a red hole?
Ostensibly a black hole is pure black because no light/electromagnetic radiation can escape (the curve in space time basically bends the light out of any escape path). But based on relativity, the light going into the hole is being subject to time dilation. Even though the light is basically instantaneously past the event horizon because it is simultaneously at its origin and destination from its perspective, for an outside observer the light would be moving slower and slower as it approached the event horizon (or alternatively, some light-emitting rock you threw in the black hole's gravity well would move slower and slower).
Now, I've recently read that as an outside observer, this light should actually be red-shifted and basically become fainter and fainter the closer to the event horizon it is. So shouldn't a black hole actually be red (or, more likely, low-frequency radio waves) from the eons of light remnants that have passed through and basically left a wake of red-shifted light?
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
I feel like at some point before that it would become 'visible' again simply because it doesn't have the mass to bend space-time to prevent the escape of light any more. But maybe there's something I'm missing.
(feel free to let me know if I've jumbled up my thought process here and both of these questions are incomprehensible)
I'll take a whack at this.
1. The light isn't coming back for you to observe it, so no, the hole is not red, it is black.
It's not the black hole that I'm asking about so much, but what basically seems like the area outside the event horizon seeming to provide red-shifted light. So the inside may be the blackest thing ever, but it sounds like the outside should be reflecting/refracted faint radio waves/infrared light (red-shifted from its source), unless there's some reason I don't know about that the faint time-dilated light dissipates or becomes invisible.
I've fixed the Venus link earlier, but there it is again, wierdly I'd just left out the whole url.Didn't realise that it just adds in the first page if it seems the url tags with nothing in them rather than just leaving them as text.
Apparently Venus is a lot closer, and with a friendlier orbit, meaning that not only are manned missions exposed to far less radiation planetside, but you've got around half the time in space.
We could actually seed Venus right now if we wanted, with stuff that'd grow rather than just not die, there's extremophile bacteria here that live in more acidic environments. That potentially that puts us a few centuries ahead of Mars as far as terraforming goes, even if it does use disappointingly fewer nukes (though we'd have to check to make sure there's nothing there already). Plus there's potentially a lot more obvious practical uses when it comes to developing the various greenhouse reducing technologies to make Venus more habitable in the long term.
Does Venus have a magnetic field for shielding from solar radiation, like earth? It must with the atmosphere right? And that's one of the detractions for going to Mars?
Does Venus have a magnetic field for shielding from solar radiation, like earth? It must with the atmosphere right? And that's one of the detractions for going to Mars?
Venus here we go!
You're possibly being sarcastic, here, but Venus has no magnetic field. As far as I know, it doesn't even have the local magnetic field that Mars has in some places as a result of magnetized crust.
This is probably why Venus has no water, incidentally--water molecules are photodissociated into hydrogen + oxygen in the upper atmosphere, and then, since the solar wind directly strikes the upper atmosphere, most of the hydrogen has escaped into space.
The near-total lack of water makes me skeptical about any proposal to "seed" the atmosphere with life. I don't know of any terrestrial lifeform that could reproduce in such dry conditions.
So the atmosphere of Venus sticks around basically through gravity? I thought a decent magnetic field was needed to protect from the solar winds eroding the whole of atmosphere?
Are you trying to tell me my memory of junior high planet sciences is either inaccurate or incomplete? (This last line is actually sarcasm, but not the rest)
Venus has a weak magnetic field according to this, but most of the radiation proofing is provided by the think atmosphere.
I'd actually assumed that the amount of water vapour was higher than the 0.002% it apparently is as the clouds of acid are so commonly associated with Venus. Didn't think you got a pH without being in water (or something similar).
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AbsoluteZeroThe new film by Quentin KoopantinoRegistered Userregular
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
Black holes are masses in an infinitely small space so they don't actually need a lot of mass to sustain a themselves. The conditions needsd to be right to create it, but once it gets started it can keep going for a long time. Mass is simply what determines the radius of the black hole's event horizon through the equation R=(2Gm)/(c^2), so a black hole that gets less massive through time just gets a smaller event horizon but otherwise remains unchanged with the same properties as before. It keeps doing this until it reaches the theoretical limit for mass needed to sustain a black hole, which is a Planck mass, or .000022grams (or 6.725x10^16 atoms of gold, give or take a couple hundred trillion atoms). At that moment before the last bit of Hawking radiation is given off, the black hole is around 5.6*10^32 K warm and 1.633*10^-35 m wide (some where around 8.28*10^24 of these smallest black holes equals the diameter of a single gold atom [109 Earths would make up the diameter of the sun, and about 154,700 Earths make up the diameter of the largest known star VY Canis Majoris to really illustrate this size difference]). Once that last bit of radiation is released though, no one knows what happens to the black hole. An idea I'm seeing says that because a black hole at this point, due to quantum mechanics, no longer interacts with the world gravitationally to suck in energy and it no longer emits energy through Hawking radiation that it's essentially an extremely small (nearly as small as the theoretical size of a string in string theory) and stable sub atomic particle, possibly even the WIMP and dark matter itself
I think that's all right. Just some quick math with wiki numbers, so don't yell at me if it wrong
I think you are using solar radii instead of solar diameters there.
The diameter of VY Canis Majoris is 2840 +/- 240 solar diameters. Or 309,560 +/- 26,160 Earth diameters.
That star is ridiculously huge.
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AbsoluteZeroThe new film by Quentin KoopantinoRegistered Userregular
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
Black holes are masses in an infinitely small space so they don't actually need a lot of mass to sustain a themselves. The conditions needsd to be right to create it, but once it gets started it can keep going for a long time. Mass is simply what determines the radius of the black hole's event horizon through the equation R=(2Gm)/(c^2), so a black hole that gets less massive through time just gets a smaller event horizon but otherwise remains unchanged with the same properties as before. It keeps doing this until it reaches the theoretical limit for mass needed to sustain a black hole, which is a Planck mass, or .000022grams (or 6.725x10^16 atoms of gold, give or take a couple hundred trillion atoms). At that moment before the last bit of Hawking radiation is given off, the black hole is around 5.6*10^32 K warm and 1.633*10^-35 m wide (some where around 8.28*10^24 of these smallest black holes equals the diameter of a single gold atom [109 Earths would make up the diameter of the sun, and about 154,700 Earths make up the diameter of the largest known star VY Canis Majoris to really illustrate this size difference]). Once that last bit of radiation is released though, no one knows what happens to the black hole. An idea I'm seeing says that because a black hole at this point, due to quantum mechanics, no longer interacts with the world gravitationally to suck in energy and it no longer emits energy through Hawking radiation that it's essentially an extremely small (nearly as small as the theoretical size of a string in string theory) and stable sub atomic particle, possibly even the WIMP and dark matter itself
I think that's all right. Just some quick math with wiki numbers, so don't yell at me if it wrong
Very helpful. Some nice information links to black hole related info like the Schwarzschild radius from the Planck mass info and that atomic-scale micro black hole is neat.
Mars is cold and terrible, why go all the way there when there's somewhere much more interesting that might have life already there and has places more tolerable to human life*? NASA is apparently thinking about cloud cities on Venus, or at least dirigible research bases.
* Places may not be tolerable to human life
Link brings it back to this page on the thread.
Isn't Venus supposed to be the worst place ever?
It's only the worst place ever if you try living on the surface. Go about 55km up or so, and you have one of the more habitable places in the solar system. Earthlike temperatures, and about 1/2 an atmosphere of pressure of mainly carbon dioxide. And with the outside air being mainly carbon dioxide, an oxygen/nitrogen mix would act as a lifting gas, with about half the lifting power that helium has on Earth.
This is where I feel it necessary to point out that 0.5 atm of CO2 would basically kill a person in minutes. Hypercapnia (excess carbon dioxide) is based on partial pressure of CO2, so that would basically be like breathing air that 50% CO2, regardless of O2 content.
Unrelated to the weirdness of partial pressures, I had a few thought experiments/questions related to black holes you people might be able able to help with:
1. Shouldn't a black hole be a red hole?
Ostensibly a black hole is pure black because no light/electromagnetic radiation can escape (the curve in space time basically bends the light out of any escape path). But based on relativity, the light going into the hole is being subject to time dilation. Even though the light is basically instantaneously past the event horizon because it is simultaneously at its origin and destination from its perspective, for an outside observer the light would be moving slower and slower as it approached the event horizon (or alternatively, some light-emitting rock you threw in the black hole's gravity well would move slower and slower).
Now, I've recently read that as an outside observer, this light should actually be red-shifted and basically become fainter and fainter the closer to the event horizon it is. So shouldn't a black hole actually be red (or, more likely, low-frequency radio waves) from the eons of light remnants that have passed through and basically left a wake of red-shifted light?
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
I feel like at some point before that it would become 'visible' again simply because it doesn't have the mass to bend space-time to prevent the escape of light any more. But maybe there's something I'm missing.
(feel free to let me know if I've jumbled up my thought process here and both of these questions are incomprehensible)
I'll take a whack at this.
1. The light isn't coming back for you to observe it, so no, the hole is not red, it is black.
It's not the black hole that I'm asking about so much, but what basically seems like the area outside the event horizon seeming to provide red-shifted light. So the inside may be the blackest thing ever, but it sounds like the outside should be reflecting/refracted faint radio waves/infrared light (red-shifted from its source), unless there's some reason I don't know about that the faint time-dilated light dissipates or becomes invisible.
It sounds like you are asking if energy is sapped from light that comes near to an event horizon but doesn't quite fall in. While the light would experience time dilation, it would not become red shifted. It would follow the extreme curvature of space time and then continue on it's merry way - in other words, we would observe gravitational lensing, but that's about it.
EDIT: I thought about this more and realized light cannot experience time dilation at all. Time is zero for light, always.
Dude. I said that the principles of arithmetic don't rest on experience. What on earth does that have to do with the historical development of applied math? Of course most people learn addition and subtraction through adults moving objects around. Of course we need to learn arithmetic because it has practical purposes. But there's a big difference between how we learn arithmetic and why we know that it is true. And the justification for the truth of addition is not based on physically moving objects together. Not only would addition only have evidence for the first small fraction of numbers (nobody has ever actually moved 750 decillion things next to 250 decillion other things and counted the result), so answers to addition problems of large numbers would be unknown, but we would only know 1+1=2 if and only if our senses had not been fooled. We only know truths of physics, biology, and chemistry because we have observed the world. If we're all in a simulation, we literally don't know anything about those subjects. But we would still know that 1+1=2, because its truth isn't dependent on past experience.
250 decillion grains of sand + 750 decillion grains of sand = 1 small star
I wish we'd get going on getting these studies done so we can green light more wind farms and such. But this was a Scottish study so clearly we will have to do our own 'merican studies, funding pending.
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
Black holes are masses in an infinitely small space so they don't actually need a lot of mass to sustain a themselves. The conditions needsd to be right to create it, but once it gets started it can keep going for a long time. Mass is simply what determines the radius of the black hole's event horizon through the equation R=(2Gm)/(c^2), so a black hole that gets less massive through time just gets a smaller event horizon but otherwise remains unchanged with the same properties as before. It keeps doing this until it reaches the theoretical limit for mass needed to sustain a black hole, which is a Planck mass, or .000022grams (or 6.725x10^16 atoms of gold, give or take a couple hundred trillion atoms). At that moment before the last bit of Hawking radiation is given off, the black hole is around 5.6*10^32 K warm and 1.633*10^-35 m wide (some where around 8.28*10^24 of these smallest black holes equals the diameter of a single gold atom [109 Earths would make up the diameter of the sun, and about 154,700 Earths make up the diameter of the largest known star VY Canis Majoris to really illustrate this size difference]). Once that last bit of radiation is released though, no one knows what happens to the black hole. An idea I'm seeing says that because a black hole at this point, due to quantum mechanics, no longer interacts with the world gravitationally to suck in energy and it no longer emits energy through Hawking radiation that it's essentially an extremely small (nearly as small as the theoretical size of a string in string theory) and stable sub atomic particle, possibly even the WIMP and dark matter itself
I think that's all right. Just some quick math with wiki numbers, so don't yell at me if it wrong
I think you are using solar radii instead of solar diameters there.
The diameter of VY Canis Majoris is 2840 +/- 240 solar diameters. Or 309,560 +/- 26,160 Earth diameters.
That star is ridiculously huge.
I'm pretty sure I used radii for all measurements and calculations, but you may be right. I can't check to see if you're right though since I threw the napkin post-it note with my math and info out.
Don't ever throw those out kids, you never know when you'll need them again
The biggest problem with terraforming Venus (other then you know, all the other awesome problems with terrafoming in general) is that it has an extremely long day. As in "darkness for 174 Earth-days". Which means it can't host an Earth-like plant biosphere since all that stuff would have to survive an absurdly long time in very cold conditions away from the sun.
We can solve most problems with making planets habitable, but getting an entire planet to start spinning on its axis is amazingly difficult. That said, there are proposed solutions but they're energy intense and there's not too many ways to cheat them (i.e. we can reasonably assume we can add water wherever we want in the solar system by nudging comets and asteroids on to impact trajectories - but you can't escape the kinetic energy equation to add a spin).
The biggest problem with terraforming Venus (other then you know, all the other awesome problems with terrafoming in general) is that it has an extremely long day. As in "darkness for 174 Earth-days". Which means it can't host an Earth-like plant biosphere since all that stuff would have to survive an absurdly long time in very cold conditions away from the sun.
We can solve most problems with making planets habitable, but getting an entire planet to start spinning on its axis is amazingly difficult. That said, there are proposed solutions but they're energy intense and there's not too many ways to cheat them (i.e. we can reasonably assume we can add water wherever we want in the solar system by nudging comets and asteroids on to impact trajectories - but you can't escape the kinetic energy equation to add a spin).
Isn't Earth's rotation generally obscenely fast for a planet this old?
Maybe we just need to crash a moon into Venus and call it good.
Thinking on the idea that a black hole ultimately turns into dark matter, it really does make a good bit of logical sense with what we think we know and understand of them* and the early universe. The early universe was a super dense... thing (plasma?) of energy, and as that energy cooled it turned into matter which in turn created pressures large enough for micro black holes to form. These BHs formed just over their theoretical minimum at the same time as the regular matter we see, and if the BH didn't pull in matter it spit out it's last Hawking radiation breath and stopped interacting with regular matter**, essentially sealing it's stored energy/matter off to the universe. Some BHs absorbed enough regular matter (and other BHs) to become the galaxy center giants we see today, and the energy/matter that escaped that early cosmic war is what we see today.
*We know nothing about BHs after they are BHs and everything about that idea is pure conjecture.
**If I understand this correctly, and I most certainly don't :rotate: , it's thought that the BH is so small it is best thought of as a thing of energy instead of matter (but is still matter) and fits between gravity's quantum energy wave so it can no longer interact by way of gravity. Sunce it can no longer take in matter/energy it no longer has any Hawking radiation to spit out which keeps us from being able to detect it, hence dark matter.
The biggest problem with terraforming Venus (other then you know, all the other awesome problems with terrafoming in general) is that it has an extremely long day. As in "darkness for 174 Earth-days". Which means it can't host an Earth-like plant biosphere since all that stuff would have to survive an absurdly long time in very cold conditions away from the sun.
We can solve most problems with making planets habitable, but getting an entire planet to start spinning on its axis is amazingly difficult. That said, there are proposed solutions but they're energy intense and there's not too many ways to cheat them (i.e. we can reasonably assume we can add water wherever we want in the solar system by nudging comets and asteroids on to impact trajectories - but you can't escape the kinetic energy equation to add a spin).
Would we need to? Isn't the atmosphere so dense that it traps heat already via the runaway greenhouse effect?
Also, slightly different, but is it hto enough in the atmosphere to boil water? I'm imagining a tube descending from a floating station carrying water down into the atmosphere and carrying steam back up to power a generator
It is, but I'm not sure that would work. You would lose a lot of heat and pressure along the way back up (surface temp is 400ish). You would also need a way to sink excess waste heat from your water, re-condensing it. Normally we use water form a river/lake/ocean for that
Also, slightly different, but is it hto enough in the atmosphere to boil water? I'm imagining a tube descending from a floating station carrying water down into the atmosphere and carrying steam back up to power a generator
Oh, I'd say so.
Average surface temperature of Venus is about 460 C.
The biggest problem with terraforming Venus (other then you know, all the other awesome problems with terrafoming in general) is that it has an extremely long day. As in "darkness for 174 Earth-days". Which means it can't host an Earth-like plant biosphere since all that stuff would have to survive an absurdly long time in very cold conditions away from the sun.
We can solve most problems with making planets habitable, but getting an entire planet to start spinning on its axis is amazingly difficult. That said, there are proposed solutions but they're energy intense and there's not too many ways to cheat them (i.e. we can reasonably assume we can add water wherever we want in the solar system by nudging comets and asteroids on to impact trajectories - but you can't escape the kinetic energy equation to add a spin).
Would we need to? Isn't the atmosphere so dense that it traps heat already via the runaway greenhouse effect?
Also, slightly different, but is it hto enough in the atmosphere to boil water? I'm imagining a tube descending from a floating station carrying water down into the atmosphere and carrying steam back up to power a generator
if you had a roughly 2km long tube, The atmosphere gets over 100C at about ~48km above the surface, and the proposed floating stations would be at round 50km. But it would probably make more sense to just use some sort of molten salt or solid state thermocouple system rather then pump steam around directly.
The biggest problem with terraforming Venus (other then you know, all the other awesome problems with terrafoming in general) is that it has an extremely long day. As in "darkness for 174 Earth-days". Which means it can't host an Earth-like plant biosphere since all that stuff would have to survive an absurdly long time in very cold conditions away from the sun.
We can solve most problems with making planets habitable, but getting an entire planet to start spinning on its axis is amazingly difficult. That said, there are proposed solutions but they're energy intense and there's not too many ways to cheat them (i.e. we can reasonably assume we can add water wherever we want in the solar system by nudging comets and asteroids on to impact trajectories - but you can't escape the kinetic energy equation to add a spin).
Would we need to? Isn't the atmosphere so dense that it traps heat already via the runaway greenhouse effect?
Also, slightly different, but is it hto enough in the atmosphere to boil water? I'm imagining a tube descending from a floating station carrying water down into the atmosphere and carrying steam back up to power a generator
if you had a roughly 2km long tube, The atmosphere gets over 100C at about ~48km above the surface, and the proposed floating stations would be at round 50km. But it would probably make more sense to just use some sort of molten salt or solid state thermocouple system rather then pump steam around directly.
Aren't molten salts just used to heat water to power steam turbines like other power methods(coal, nuclear, biofuel, natural gas )?
Yeah, water -> steam is a liquid to gas phase change which causes a huge pressure differential (extra heat helps too) and it's the pressure that drives the turbine. Molten salts can be used to move heat around though
Well I was just thinking that Molten salt would allow for more thermal energy to be moved in the pipe at a lower vapor pressure,so you wouldn't have to move as much around to get the same power generation. Plus as a liquid you would probably need a thinner pipe as it couldn't be compressed by the atmosphere outside. Obviously it would then be used to turn some water into steam to spin a turbine at the end.
But I guess you would also need a longer pipe overall to get to the higher temperatures lower in the atmosphere.
I'm just sorta spit-balling, not really a certified power plant builder for floating cities on Venus.
I've said it before, I'll say it again: these bullets aren't really for people on the ground. They're for adding .50 cal sniper rifles to drones.
I don't know if you're joking or not, but .50 cal isn't that accurate. A sniper could definitely benefit from having a round like that. They could even come in handy on a machine gun.
Uhh... 3 of the 4 longest recorded snipper kills are with .50.
Yeah, water -> steam is a liquid to gas phase change which causes a huge pressure differential (extra heat helps too) and it's the pressure that drives the turbine. Molten salts can be used to move heat around though
Kettles, see previous comment.
Also whilst looking at this stuff I did find this modest proposal, for moving planets like Venus and Mars into the right habitable orbit in a more reasonable time frame than the traditional cosmic snooker or Annihilatrax method (>30 years or so). Your welcome.
Yeah, water -> steam is a liquid to gas phase change which causes a huge pressure differential (extra heat helps too) and it's the pressure that drives the turbine. Molten salts can be used to move heat around though
Kettles, see previous comment.
Also whilst looking at this stuff I did find this modest proposal, for moving planets like Venus and Mars into the right habitable orbit in a more reasonable time frame than the traditional cosmic snooker or Annihilatrax method (>30 years or so). Your welcome.
The only problem with the mechanism involved is you'd probably be doing something similar in scale to a proposed plan where 'the entirety of planet Mercury's industrial materials is consumed to generate electrical power', at which point you could just vaporize Venus if you wanted to. Once you have that much energy at your disposal, the concept of colonizing planets falls out of favor to constructing them wholesale.
The paper is very much a joke in that vein, given that the whole premise is based on accepting that "moving a planet with rockets or impacts is silly, it'd be far more efficient to just slow down the Sun and transfer that energy to moving a planet".
Though at this point I do wonder whether it's an easier project than a Dyson Sphere, Ringworld or an Orbital. Estimated costs are only 6x the global defence budget and it seems vaguely renewable. Plus once you've used it to yank Venus into position - the costs of them moving Mars and Ceres into position seems a lot less.
It's not the black hole that I'm asking about so much, but what basically seems like the area outside the event horizon seeming to provide red-shifted light. So the inside may be the blackest thing ever, but it sounds like the outside should be reflecting/refracted faint radio waves/infrared light (red-shifted from its source), unless there's some reason I don't know about that the faint time-dilated light dissipates or becomes invisible.
You are indeed correct that radiation produced near a black hole is red-shifted. However, the radiation produced has such a high frequency in the source reference frame that even the red-shifted version is still contains plenty of x-rays. This is because matter near the event horizon is incredibly hot.
In other news, Kepler is back in business. After it lost a reaction wheel, reducing it to just two functional reaction wheels - not enough to keep the craft stable - research had to be suspended until an alternate way of stabilizing the telescope was found. As it turns out, it's possible to balance it using the two reaction wheels and the force sunlight exerts on its sun shield, initiating a second phase of its research mission.
The biggest problem with terraforming Venus (other then you know, all the other awesome problems with terrafoming in general) is that it has an extremely long day. As in "darkness for 174 Earth-days". Which means it can't host an Earth-like plant biosphere since all that stuff would have to survive an absurdly long time in very cold conditions away from the sun.
It's not that long. Because of its retrograde rotation, the solar day of Venus is only 117 Earth-days, so roughly two months of darkness at a time. Depending on just how cold it gets, this doesn't seem like a huge obstacle to me. I live in Finland; I know first hand that we already have life forms (and people!) adapted to surviving an absurdly long time in very cold conditions away from the sun. Plant life in particular is extremely well adapted to this kind of thing.
Looking into Venus colonization is an interesting idea. I don't know if it would be feasible to ever colonize the surface of Venus, but I'm not sure a floating city is anymore difficult to do than what would be needed on Mars. It's just both would have different challenges. IMO both are worth doing.
From a species survival standpoint, having Earth as the home world with colonies on both Mars and Venus, is much better than just have human civilization on Earth and Mars. Barring some solar system wide catastrophes, mainly a gamma burst (and that might be less of an issue with how we'd have to build some space colonies, granted it'll still suck for a number of people that instantly vaporize), you'd need something to go horribly wrong on all three planets and in a close enough time frame to cause human extinction. If something goes horribly wrong on one, you still have the other two and that probably gives you enough time to wait out or fix whatever is going horribly on one of them (well at some point the sun is going to expand and swallow up the inner planets, but I'd hope by that point, we'd either have interstellar travel figured out or have figured out how to make viable colonies further out in the Solar System. Point is, for survival, we'd want to have as many baskets as possible. If we can get colonies on both Mars and Venus, I'd imagine that opens up the moon and possibly orbital cites as well.
Building a colony on Venus, even if it's just the floating city and not the full on terraforming route (maybe no one tries or it fails). Means learning how to build develop technologies that can cope with Venus's climate. As they say, necessity is the mother of all invention. If we ever hit interstellar travel as a viable means, then that opens up more places to colonize in the galaxy because there will be other planets like Venus and in some cases, the only world or moon in a system that can be colonized, may be Venus like. I'd also argue technologies that are derived from colonizing Venus or even developed for terraforming purposes could be applicable to places like future Earth or Mars, even if the terraforming fails. We know it's going to get hotter on Earth and continue to do so, once the Sun reaches a certain size, but working on Venus might allow us to push back the dateline for "humans can no longer live on this hunk of rock." Now maybe we won't ever need to make use of those technologies, but it would hurt to have them. The major downside to Venus, is that it'll have a life habitable life span shorter than Earth's, but I think we have a shit ton of time before we have to worry about it becoming too hot to do anything with.
I've said it before, I'll say it again: these bullets aren't really for people on the ground. They're for adding .50 cal sniper rifles to drones.
I don't know if you're joking or not, but .50 cal isn't that accurate. A sniper could definitely benefit from having a round like that. They could even come in handy on a machine gun.
Uhh... 3 of the 4 longest recorded snipper kills are with .50.
That's cool, but the M107 is still a 3 MOA weapon. Obviously the large round will have a much longer max effective range than a smaller one, meaning it can actually kill from further out. Still, at its max effective range you're looking at a 60 inch shot group.
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A NASA rover has found the building blocks of life on Mars. They might be the product of past or present life on the Red Planet -- or they might not be.
Either way, the samples of organic matter in the atmosphere and in rock show that Mars may at least have once had conditions favorable to hosting life, NASA said in a statement. They also show that the planet is still chemically active.
The Curiosity rover's tapping into organics in rock is the first find ever of life's building blocks on Mars' surface.
The rover has run into pockets of gas on Mars: methane, often used to fire up gas stoves back on Earth.
Organic matter is made up of carbon bonded with other elements, often hydrogen and oxygen. Living things are made up of it, but life is not necessary for it to exist.
Methane is the smallest organic compound, consisting of one carbon and four hydrogen atoms.
On our planet, methane is a fossil fuel, but it can also rise out of rotting sewage or fly through the air in flatulence.
In other words, it usually comes from something living, or something that was once alive.
No life found
That could be the case on Mars, too, NASA said in a statement this week.
But the space agency carefully points out that methane can also come from inanimate sources as well.
There are many possible sources, biological or non-biological, such as interaction of water and rock," said Sushil Atreya, a scientist on the Curiosity team.
At this point, NASA doesn't know if microbes are behind the gas or just minerals.
Researchers used Curiosity's instruments a dozen times to get a breath of methane, and four of those times, it peaked at a level 10 times higher than usual.
They believe it may have been puffed up from the ground like little burps.
Organic rock
Curiosity also found organic matter while drilling into stone.
"This first confirmation of organic carbon in a rock on Mars holds much promise," said scientist Roger Summons, who works on the rover team.
These building blocks of life could have formed on Mars, or meteorites could have brought them there. Scientists aren't sure yet.
Also, they can't be completely sure what molecules they are, because a coincidental chemical reaction that occurs in the detection device skews some of the samples.
So far, they've also found no sign of microbes in the rock powder, neither present nor past.
The history of water on Mars has also been a popular research topic.
The analysis of hydrogen atoms Curiosity found in rock have led NASA scientists to conclude that much of Mars' former oceans disappeared very early -- before the rocks were formed.
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Curious about that speculation. I assume any pre-microbial macromolecules would periodically cycle into the hellscape of Venus's lower atmosphere and be annihilated, so it's tough to see how evolution gets started.
This is where I feel it necessary to point out that 0.5 atm of CO2 would basically kill a person in minutes. Hypercapnia (excess carbon dioxide) is based on partial pressure of CO2, so that would basically be like breathing air that 50% CO2, regardless of O2 content.
Unrelated to the weirdness of partial pressures, I had a few thought experiments/questions related to black holes you people might be able able to help with:
1. Shouldn't a black hole be a red hole?
Ostensibly a black hole is pure black because no light/electromagnetic radiation can escape (the curve in space time basically bends the light out of any escape path). But based on relativity, the light going into the hole is being subject to time dilation. Even though the light is basically instantaneously past the event horizon because it is simultaneously at its origin and destination from its perspective, for an outside observer the light would be moving slower and slower as it approached the event horizon (or alternatively, some light-emitting rock you threw in the black hole's gravity well would move slower and slower).
Now, I've recently read that as an outside observer, this light should actually be red-shifted and basically become fainter and fainter the closer to the event horizon it is. So shouldn't a black hole actually be red (or, more likely, low-frequency radio waves) from the eons of light remnants that have passed through and basically left a wake of red-shifted light?
2. Can a black hole become not a black hole over time?
If Hawking radiation does exist, would it be feasible to eventually 'burn off' enough mass that the inside of the black hole becomes visible again? It seems that microsingularities can exist, so it seems like once something has basically been compressed into a point mass there's no going back, but if Hawking radiation existed and you had a black hole that had nothing to 'feed' off of, wouldn't you eventually be left with a 'singularity' that's just a handful of subatomic particles.
I feel like at some point before that it would become 'visible' again simply because it doesn't have the mass to bend space-time to prevent the escape of light any more. But maybe there's something I'm missing.
(feel free to let me know if I've jumbled up my thought process here and both of these questions are incomprehensible)
I'll take a whack at this.
1. The light isn't coming back for you to observe it, so no, the hole is not red, it is black.
2. If Hawking Radiation exists, the black hole simply evaporates over time. It never becomes not a black hole, but it will dissipate to nothing eventually.
The speculation is more based on the assumption that Venus wasn't a total shithole a few billion years back, and based on fossil records on Earth we had life 3.5 billion years ago. Now, we could have had life earlier but because of bombardment, evidence of that has been erased. Since Mars is known to have had water no less recently than 1 billion years ago, that's a 2.5 billion year overlap for at least two planets with liquid water on their surfaces in our solar system (or rather, two planets capable of supporting life for 2.5 billion years). Due to the local climate, we have not been able to investigate this thoroughly on Venus but it would not be so unreasonable to believe that it as well had a prolonged period of habitability.
Noting from our experiments attempting to kill Tardigrades and microbes in LEO, it's quite possible organisms and spores could have been spread between all three in the early periods of habitability where powerful impacts were a frequent and regular experience. If Venus had anything alive pre-hellscape, it may have adapted and survived to this day in its upper atmosphere. Note that this has interesting implications for the Jovian and Saturnian moons with water, as they would have been contaminated during those billions of years too.
Yeah but no one is suggesting that people actually be outside*. Those conditions would make it easy to keep habitable conditions inside your floating building though. Remember that any building/structure/floating thingy has to interface with its environment. The closer the temperatures and pressures on the outside are to the inside, the easier the job is to maintain inside conditions.
CO2 is useful because like they were saying, an oxygen nitrogen mix (aka air) would basically create lift for you. Making your design requirements even easier. And when you consider the highly acidic conditions below, CO2 is a lot nicer to deal with.
*unprotected by a suit
There was a paper written about this last year which calculated that yes, rocks ejected into space from asteroid impacts on Earth and Mars (when Mars was potentially habitable) could travel to Jupiter, Saturn, and their respective moons, including ones big enough that they could hold bacteria or something like that. The K-T impact would have been big enough to launch some rocks out of Earth orbit as well, though most of the transfer would have been during the Late Heavy Bombardment.
Black holes are masses in an infinitely small space so they don't actually need a lot of mass to sustain a themselves. The conditions needsd to be right to create it, but once it gets started it can keep going for a long time. Mass is simply what determines the radius of the black hole's event horizon through the equation R=(2Gm)/(c^2), so a black hole that gets less massive through time just gets a smaller event horizon but otherwise remains unchanged with the same properties as before. It keeps doing this until it reaches the theoretical limit for mass needed to sustain a black hole, which is a Planck mass, or .000022grams (or 6.725x10^16 atoms of gold, give or take a couple hundred trillion atoms). At that moment before the last bit of Hawking radiation is given off, the black hole is around 5.6*10^32 K warm and 1.633*10^-35 m wide (some where around 8.28*10^24 of these smallest black holes equals the diameter of a single gold atom [109 Earths would make up the diameter of the sun, and about 154,700 Earths make up the diameter of the largest known star VY Canis Majoris to really illustrate this size difference]). Once that last bit of radiation is released though, no one knows what happens to the black hole. An idea I'm seeing says that because a black hole at this point, due to quantum mechanics, no longer interacts with the world gravitationally to suck in energy and it no longer emits energy through Hawking radiation that it's essentially an extremely small (nearly as small as the theoretical size of a string in string theory) and stable sub atomic particle, possibly even the WIMP and dark matter itself
I think that's all right. Just some quick math with wiki numbers, so don't yell at me if it wrong
Depends on what you actually consider part of the black hole. You're right, objects inside a gravity well do appear redshifted to a distant observer (gravitational redshift). But at the event horizon, the redshift becomes so great the wavelengths become infinitely long (0 frequency) so it appears perfectly black.
Very helpful. Some nice information links to black hole related info like the Schwarzschild radius from the Planck mass info and that atomic-scale micro black hole is neat.
It's not the black hole that I'm asking about so much, but what basically seems like the area outside the event horizon seeming to provide red-shifted light. So the inside may be the blackest thing ever, but it sounds like the outside should be reflecting/refracted faint radio waves/infrared light (red-shifted from its source), unless there's some reason I don't know about that the faint time-dilated light dissipates or becomes invisible.
Apparently Venus is a lot closer, and with a friendlier orbit, meaning that not only are manned missions exposed to far less radiation planetside, but you've got around half the time in space.
We could actually seed Venus right now if we wanted, with stuff that'd grow rather than just not die, there's extremophile bacteria here that live in more acidic environments. That potentially that puts us a few centuries ahead of Mars as far as terraforming goes, even if it does use disappointingly fewer nukes (though we'd have to check to make sure there's nothing there already). Plus there's potentially a lot more obvious practical uses when it comes to developing the various greenhouse reducing technologies to make Venus more habitable in the long term.
Venus here we go!
This is probably why Venus has no water, incidentally--water molecules are photodissociated into hydrogen + oxygen in the upper atmosphere, and then, since the solar wind directly strikes the upper atmosphere, most of the hydrogen has escaped into space.
The near-total lack of water makes me skeptical about any proposal to "seed" the atmosphere with life. I don't know of any terrestrial lifeform that could reproduce in such dry conditions.
So the atmosphere of Venus sticks around basically through gravity? I thought a decent magnetic field was needed to protect from the solar winds eroding the whole of atmosphere?
Are you trying to tell me my memory of junior high planet sciences is either inaccurate or incomplete? (This last line is actually sarcasm, but not the rest)
I'd actually assumed that the amount of water vapour was higher than the 0.002% it apparently is as the clouds of acid are so commonly associated with Venus. Didn't think you got a pH without being in water (or something similar).
I think you are using solar radii instead of solar diameters there.
The diameter of VY Canis Majoris is 2840 +/- 240 solar diameters. Or 309,560 +/- 26,160 Earth diameters.
That star is ridiculously huge.
It sounds like you are asking if energy is sapped from light that comes near to an event horizon but doesn't quite fall in. While the light would experience time dilation, it would not become red shifted. It would follow the extreme curvature of space time and then continue on it's merry way - in other words, we would observe gravitational lensing, but that's about it.
EDIT: I thought about this more and realized light cannot experience time dilation at all. Time is zero for light, always.
TLDR birds are not dumb and avoid giant moving objects in their flight path. Also, humans can make good choices and not build wind farms on nesting sites. Scientific study requests more funding because data is incomplete. News at 11.
I wish we'd get going on getting these studies done so we can green light more wind farms and such. But this was a Scottish study so clearly we will have to do our own 'merican studies, funding pending.
I'm pretty sure I used radii for all measurements and calculations, but you may be right. I can't check to see if you're right though since I threw the napkin post-it note with my math and info out.
Don't ever throw those out kids, you never know when you'll need them again
We can solve most problems with making planets habitable, but getting an entire planet to start spinning on its axis is amazingly difficult. That said, there are proposed solutions but they're energy intense and there's not too many ways to cheat them (i.e. we can reasonably assume we can add water wherever we want in the solar system by nudging comets and asteroids on to impact trajectories - but you can't escape the kinetic energy equation to add a spin).
Isn't Earth's rotation generally obscenely fast for a planet this old?
Maybe we just need to crash a moon into Venus and call it good.
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*We know nothing about BHs after they are BHs and everything about that idea is pure conjecture.
**If I understand this correctly, and I most certainly don't :rotate: , it's thought that the BH is so small it is best thought of as a thing of energy instead of matter (but is still matter) and fits between gravity's quantum energy wave so it can no longer interact by way of gravity. Sunce it can no longer take in matter/energy it no longer has any Hawking radiation to spit out which keeps us from being able to detect it, hence dark matter.
Would we need to? Isn't the atmosphere so dense that it traps heat already via the runaway greenhouse effect?
Also, slightly different, but is it hto enough in the atmosphere to boil water? I'm imagining a tube descending from a floating station carrying water down into the atmosphere and carrying steam back up to power a generator
Oh, I'd say so.
Average surface temperature of Venus is about 460 C.
if you had a roughly 2km long tube, The atmosphere gets over 100C at about ~48km above the surface, and the proposed floating stations would be at round 50km. But it would probably make more sense to just use some sort of molten salt or solid state thermocouple system rather then pump steam around directly.
Aren't molten salts just used to heat water to power steam turbines like other power methods(coal, nuclear, biofuel, natural gas )?
But I guess you would also need a longer pipe overall to get to the higher temperatures lower in the atmosphere.
I'm just sorta spit-balling, not really a certified power plant builder for floating cities on Venus.
Uhh... 3 of the 4 longest recorded snipper kills are with .50.
Kettles, see previous comment.
Also whilst looking at this stuff I did find this modest proposal, for moving planets like Venus and Mars into the right habitable orbit in a more reasonable time frame than the traditional cosmic snooker or Annihilatrax method (>30 years or so). Your welcome.
The only problem with the mechanism involved is you'd probably be doing something similar in scale to a proposed plan where 'the entirety of planet Mercury's industrial materials is consumed to generate electrical power', at which point you could just vaporize Venus if you wanted to. Once you have that much energy at your disposal, the concept of colonizing planets falls out of favor to constructing them wholesale.
Though at this point I do wonder whether it's an easier project than a Dyson Sphere, Ringworld or an Orbital. Estimated costs are only 6x the global defence budget and it seems vaguely renewable. Plus once you've used it to yank Venus into position - the costs of them moving Mars and Ceres into position seems a lot less.
You are indeed correct that radiation produced near a black hole is red-shifted. However, the radiation produced has such a high frequency in the source reference frame that even the red-shifted version is still contains plenty of x-rays. This is because matter near the event horizon is incredibly hot.
It's not that long. Because of its retrograde rotation, the solar day of Venus is only 117 Earth-days, so roughly two months of darkness at a time. Depending on just how cold it gets, this doesn't seem like a huge obstacle to me. I live in Finland; I know first hand that we already have life forms (and people!) adapted to surviving an absurdly long time in very cold conditions away from the sun. Plant life in particular is extremely well adapted to this kind of thing.
From a species survival standpoint, having Earth as the home world with colonies on both Mars and Venus, is much better than just have human civilization on Earth and Mars. Barring some solar system wide catastrophes, mainly a gamma burst (and that might be less of an issue with how we'd have to build some space colonies, granted it'll still suck for a number of people that instantly vaporize), you'd need something to go horribly wrong on all three planets and in a close enough time frame to cause human extinction. If something goes horribly wrong on one, you still have the other two and that probably gives you enough time to wait out or fix whatever is going horribly on one of them (well at some point the sun is going to expand and swallow up the inner planets, but I'd hope by that point, we'd either have interstellar travel figured out or have figured out how to make viable colonies further out in the Solar System. Point is, for survival, we'd want to have as many baskets as possible. If we can get colonies on both Mars and Venus, I'd imagine that opens up the moon and possibly orbital cites as well.
Building a colony on Venus, even if it's just the floating city and not the full on terraforming route (maybe no one tries or it fails). Means learning how to build develop technologies that can cope with Venus's climate. As they say, necessity is the mother of all invention. If we ever hit interstellar travel as a viable means, then that opens up more places to colonize in the galaxy because there will be other planets like Venus and in some cases, the only world or moon in a system that can be colonized, may be Venus like. I'd also argue technologies that are derived from colonizing Venus or even developed for terraforming purposes could be applicable to places like future Earth or Mars, even if the terraforming fails. We know it's going to get hotter on Earth and continue to do so, once the Sun reaches a certain size, but working on Venus might allow us to push back the dateline for "humans can no longer live on this hunk of rock." Now maybe we won't ever need to make use of those technologies, but it would hurt to have them. The major downside to Venus, is that it'll have a life habitable life span shorter than Earth's, but I think we have a shit ton of time before we have to worry about it becoming too hot to do anything with.
That's cool, but the M107 is still a 3 MOA weapon. Obviously the large round will have a much longer max effective range than a smaller one, meaning it can actually kill from further out. Still, at its max effective range you're looking at a 60 inch shot group.