Page 4 of 4 FirstFirst ... 234
Results 31 to 40 of 40

  Click here to go to the first staff post in this thread.   Thread: Ask me about astronomy

  1. #31
    Solifugid Onnes's Avatar
    Weasyl
    Onnes
    Join Date
    Aug 2012
    Location
    Illinois
    Posts
    321
    If you want to worry about incredibly low probability events destroying human civilization, my favorite has always been the false vacuum. This is the idea that your local place in the universe is not necessarily in a stable state--in the quantum vacua sense--but instead some metastable configuration that yields what we know as reality. Were this to be true, then at any point in time the universe itself could drop from that metastable point to a lower energy configuration, instantly ending existence as we understand it. Quantum field theory is great, isn't it?

  2.   Click here to go to the next staff post in this thread.   #32
    Retired Staff Frank LeRenard's Avatar
    Weasyl
    MLR
    Join Date
    Jul 2012
    Location
    Land of the Finns
    Posts
    439
    Quote Originally Posted by Onnes View Post
    If you want to worry about incredibly low probability events destroying human civilization, my favorite has always been the false vacuum. This is the idea that your local place in the universe is not necessarily in a stable state--in the quantum vacua sense--but instead some metastable configuration that yields what we know as reality. Were this to be true, then at any point in time the universe itself could drop from that metastable point to a lower energy configuration, instantly ending existence as we understand it. Quantum field theory is great, isn't it?
    It really is... mostly because it feels like you can get it to do pretty much whatever you like. I guess when you're dealing with multidimensional tensors, you end up with an awful lot of complexity to interpret. Same goes for GR, really (hence all the 7.8 billion different f(R) theories).

    I have heard of this particular one, at some point. I think it was in the context of a discussion about the anthropic principle, but that's something better left to Fay's philosophy thread.

    What was that thing Hawking recently brought up about the Higgs boson also potentially destroying the universe? I never got a good explanation of that one, or I did and instantly forgot what it was, or something.

  3. #33
    Solifugid Onnes's Avatar
    Weasyl
    Onnes
    Join Date
    Aug 2012
    Location
    Illinois
    Posts
    321
    Quote Originally Posted by Frank LeRenard View Post
    It really is... mostly because it feels like you can get it to do pretty much whatever you like. I guess when you're dealing with multidimensional tensors, you end up with an awful lot of complexity to interpret. Same goes for GR, really (hence all the 7.8 billion different f(R) theories).

    I have heard of this particular one, at some point. I think it was in the context of a discussion about the anthropic principle, but that's something better left to Fay's philosophy thread.

    What was that thing Hawking recently brought up about the Higgs boson also potentially destroying the universe? I never got a good explanation of that one, or I did and instantly forgot what it was, or something.
    In the typical mexican hat example for the Higgs potential, you can imagine that somewhere beyond the usual phi^4 barrier the potential bends down again due to higher order terms, resulting in a lower minimum further from the origin. If you could knock the state past that barrier, then you'd get a phase transition to whatever twilight zone reality corresponds to that new (meta)stable configuration. I think particle theorists have more sophisticated understandings of how the Higgs potential can be formed that haven't excluded this sort of thing. I'm a condensed matter theorist so I just assume metastable states are pervasive.

  4.   Click here to go to the next staff post in this thread.   #34
    Retired Staff Frank LeRenard's Avatar
    Weasyl
    MLR
    Join Date
    Jul 2012
    Location
    Land of the Finns
    Posts
    439
    Quote Originally Posted by Onnes View Post
    In the typical mexican hat example for the Higgs potential, you can imagine that somewhere beyond the usual phi^4 barrier the potential bends down again due to higher order terms, resulting in a lower minimum further from the origin. If you could knock the state past that barrier, then you'd get a phase transition to whatever twilight zone reality corresponds to that new (meta)stable configuration. I think particle theorists have more sophisticated understandings of how the Higgs potential can be formed that haven't excluded this sort of thing. I'm a condensed matter theorist so I just assume metastable states are pervasive.
    So it'd be like that whole symmetry-breaking thing in the beginning of the universe, when it fell from the unstable state at the top of the central peak in the Mexican-hat potential (on a related note, they should really just call it the 'sombrero potential'). Like, breaking the broken symmetry and presumably changing all the laws of physics again, or something? I guess there's some quantum-tunneling-like effect that makes this sort of thing possible?

  5. #35
    Solifugid Onnes's Avatar
    Weasyl
    Onnes
    Join Date
    Aug 2012
    Location
    Illinois
    Posts
    321
    Quote Originally Posted by Frank LeRenard View Post
    So it'd be like that whole symmetry-breaking thing in the beginning of the universe, when it fell from the unstable state at the top of the central peak in the Mexican-hat potential (on a related note, they should really just call it the 'sombrero potential'). Like, breaking the broken symmetry and presumably changing all the laws of physics again, or something? I guess there's some quantum-tunneling-like effect that makes this sort of thing possible?
    That's my understanding of the Higgs potential. It's a basic result of QFT that if a lower energy state exists then there is a nonzero probability to spontaneously transition to that state, which is the basis of the false vacuum concept. Hawking's thought seems to be that a sufficiently high energy collision could induce the phase transition locally, and that it would then propagate outward. I don't know how this squares with the persistently high energies of galactic sources.

  6.   Click here to go to the next staff post in this thread.   #36
    Retired Staff Frank LeRenard's Avatar
    Weasyl
    MLR
    Join Date
    Jul 2012
    Location
    Land of the Finns
    Posts
    439
    Well, that squares it. The LHC is once again going to destroy the universe.

  7.   Click here to go to the next staff post in this thread.   #37
    Retired Staff Frank LeRenard's Avatar
    Weasyl
    MLR
    Join Date
    Jul 2012
    Location
    Land of the Finns
    Posts
    439
    Space travel...

    I guess the problems with space travel differ depending on where you want to go. We can't get back to the moon because we don't want to spend the money, more or less. We can't get to Mars because we don't want to develop the technology because it costs too much money. And the reasons we don't want to spend this money is because currently there's no political impetus for doing so (no competition with Russia, for example, which in hindsight seems to be the only reason we sent men to the moon in the first place: Neil Tyson has a lot to say on that subject).

    Going beyond Mars has its own problems, not the least of which is just the time it takes to get out there, and the amount of resources necessary to send stuff out there in the first place. I don't know if you've heard of it, but there's a little probe called New Horizons currently flying through space at a gazillion miles per hour, headed for Pluto (due to reach it this year! I'm horribly excited about that, to be honest), which is the fastest craft mankind has ever built. I guess it's currently moving at around 35,000 mph (for some perspective on that number, the sound barrier is around 750 mph). It was launched in 2006, and is just now this year reaching Pluto. It's about the size of a grand piano, and its cost is going to run to almost a billion dollars. Its purpose is essentially just to fly by Pluto and take some photographs for scientific analysis, so all it has on board are scientific instruments, a power source, and some computer equipment. So do your best to extrapolate that time and cost to a whole huge vessel capable of housing more than one human. Also, if you ever wanted to return said humans to Earth, you'd have to double the resources you need to pack to keep them alive, and include that much additional fuel to slow down and turn around, speed up to get back to Earth, and then slow down again to make the actual orbit/landing. If we can't even make it to Mars, there's not a chance in hell we're getting to Neptune anytime soon.

    So maybe the answer is a technological fix, something to reduce those overheads. One proposal I often hear is about building a shuttle construction site/launchpad in space. It costs a lot of money and takes a lot of fuel to get a rocket off of the Earth, so if you start from orbit, all that cost is completely out of the equation (although you'd still have to launch people up into orbit, but the public sector is already making strides in bringing that cost down). Again, though, no one wants to spend the money to build that initial infrastructure (and then maintain it) in the first place. These types of things are new technology, and new technology requires not just the cost of construction, but the cost of getting it right. This is all a gigantic investment.

    Assuming we did build something like that, time is still an issue. Getting to the nearest star at the speed of New Horizons (again, the fastest craft we've ever built) would take something like 80,000 years. If you want to shorten the time it takes, you have to speed the craft up, which means you have to load the craft with more fuel, which means the craft will be heavier, which means it will be harder to speed up, which means you have to load more fuel, etc. It's a losing game with our current technology. Something like a portable nuclear fusion engine might help it along, since such a hypothetical engine would presumably run on hydrogen or some variant thereof, which is the lightest element in the periodic table (also fusion is very efficient, so you wouldn't need to carry as much of it). Even then, you're still limited to small fractions of the speed of light (of order, say, 0.01% if you're doing really well), just because of the sheer amount of energy it takes to accelerate anything larger than a proton to anything even approaching the speed of light. Supernovae and quasars can do it; we can't. And even if you managed to get almost all the way there, most of the Galaxy is still thousands of years of travel time away. Other galaxies would be millions to billions of years of travel time away, and then some more thousands of years to get anywhere within them (this is all ignoring special relativistic concerns, which make things very complicated).

    Then there's this whole lovely idea of the warp drive, where you bend spacetime or tunnel through it with a wormhole or some other thing. Believe it or not, there's been quite a few papers written on this subject by learned individuals, but once again the conclusion seems to be that the energy costs would be outrageous to the point of infeasibility. You'd have to convert the entire planet Jupiter into usable energy just to get the damn thing started, is the figure I always hear.

    Then there's the psychological impact long-term space travel would have on the people doing the voyage, which we are completely unaware of at this juncture. Although there's a book written on the subject by Mary Roach, called Packing for Mars; I haven't read it, but I have read another one of her books, called Spook, and thoroughly enjoyed it. Of course, that's a hurdle we can probably jump with comparatively little trouble. People can get used to all sorts of weird shit.


    So I guess, in short, we need some kind of crazy advanced magical technology to surmount physics in order to start Trekking across the universe that we're only just now starting to touch on in a theoretical way. I won't discount us as a species ever being able to do it, but it's going to be a long, long while before we actually do. We might make it to Mars in our lifetimes (us meaning the rough generation of the people posting in this thread). Don't count on much beyond that.
    Last edited by Frank LeRenard; 02-26-2015 at 01:54 AM.

  8. #38
    Senior Rilvor's Avatar
    Weasyl
    Clove Darkwave
    Join Date
    Feb 2013
    Location
    Alteir
    Posts
    1,199
    I love this thread so much.

  9. #39
    Senior Antumbra's Avatar
    Weasyl
    Antumbra
    Join Date
    Mar 2014
    Location
    Colorado
    Gender
    Male
    Posts
    678
    Speaking of space travel,

    Did you hear about that mission some private company is doing to send people to Mars? Their trick was going to be that it is a guaranteed one-way trip. They had a surprisingly large numbers of volunteers.

    Do you think they would even make it and what would they have to overcome to have a somewhat decent lifespan there?

  10.   This is the last staff post in this thread.   #40
    Retired Staff Frank LeRenard's Avatar
    Weasyl
    MLR
    Join Date
    Jul 2012
    Location
    Land of the Finns
    Posts
    439
    Quote Originally Posted by Antumbra View Post
    Speaking of space travel,

    Did you hear about that mission some private company is doing to send people to Mars? Their trick was going to be that it is a guaranteed one-way trip. They had a surprisingly large numbers of volunteers.

    Do you think they would even make it and what would they have to overcome to have a somewhat decent lifespan there?
    I have heard of it. It's called Mars One, and it's based out of the Netherlands.

    Their stated goal is to get people to Mars within the next ten years. I'm dubious of that number, because again, the technology required to build a settlement on Mars doesn't exist yet, and if you want to get it right (i.e. not have everyone die within weeks after landing), you have to spend a lot of time and money first. Apparently some folks at MIT also doubt Mars One's capacity to fulfill that timeline and published a study on it fairly recently.

    The challenges of living on Mars are pretty numerous. Some are obvious: the atmosphere there is extremely thin (something like 1% the density of Earth's) and about 97% carbon dioxide, average temperatures are pretty damned cold (something like -70 F, or -55 C), and so on. You also have to deal with solar radiation because of the thin atmosphere and very weak magnetic field -- without protecting against that, cancer rates would be outrageous, basically. You also of course need food, water, and oxygen; growing plants for food could work, and would produce oxygen as a byproduct (although again, the technology for it is in its infancy), but there are risks that too much oxygen might be produced and end up suffocating that crew and increasing risk of fires. As for water, I seem to recall reading that Mars One's plan is to isolate it from the Martian soil somehow, but again, that relies on technology that doesn't exist yet. Also, some estimates are that it would actually be financially more viable not to grow food and harvest water on Mars, but to ship it in from Earth, so that's a big cost issue that can't be overlooked.

    One thing no one seems to like talking about is dust, which would end up being hugely problematic no matter how isolated you think your environment is from the Martian atmosphere. Dust on Mars is kind of like dust on the moon, in that because of the rarified atmosphere, you can get these things called microcraters, which are exactly what they sound like they are: craters on grains of sand caused by impacts from space dust. So the dust on Mars is extremely fine (take Earth dust and then break it apart with constant tiny impacts over the course of a few billion years, and you've got Mars dust) and hence can get just about everywhere: into equipment, into the air, into lungs, into eyes, etc. I don't know what Mars One's plan is to combat that particular problem.

    There's also the obvious issue that these people would be extremely isolated. At best it takes several months (I think it's something like 6-8) to get there, and that's only available once every two years or so when Mars is at opposition. So if something goes wrong, they would be completely screwed. Hopefully these Mars One folks are all incredibly ingenious.

    So could they do it? Sure, eventually. But again, 10 years seem a little optimistic at this point.


    This is all just from my memory. If you want a good exploration of living on Mars, I've got two things I recommend reading: one is Kim Stanley Robinson's Mars Trilogy (Red Mars, Green Mars, Blue Mars; said to be one of the most accurate depictions of interplanetary colonization written so far), and the other is The Martian, by Andy Weir, which is a thriller about a guy who gets stuck on Mars alone and has to survive until help arrives (also purported to be extremely accurate; I haven't read that one yet).

 

 

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •