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So if recent Science Fiction has taught us anything it's that
we'll strand a
man on mars and that the moon is going to split into seven
pieces. For the small chance that you may be hit in the head
with a meteor or small moon fragment, you'll be covered!That
day may never come, but
when it
does you'll be ready.
Granted that in the case of the "Hard Rain" the helmets may
delay your death by only a few milliseconds at best, but you'll
be
going out with a spiffy helmet. Live your remaining days under
a
helmet that broadcasts: "See, I told you we're all going to die!"
Your helmet may not protect you from an extinction level
catastrophe, but up until that final day you'll be partially
protected from any small meteorites.
Basic meteor protection
https://en.wikipedi...wiki/Simplon_Tunnel
Crude, but effective. [8th of 7, Jul 04 2015]
Yes.
https://xkcd.com/1530/
Spiders can use the internet. [pertinax, Jul 05 2015]
[link]
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A stylish chapeau with the ability to absorb a hit from a
baseball sized meteor going at <140mph, guaranteed to make
you look "in the know." |
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Can it be decorated in aluminum foil, to disguise it amongst
the more classic popular versions? |
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Presumably, all the energy being stolen from the moon by tidal power barrages will cause it to de-orbit at some point. |
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I'm taking it as read that the orbital decay will be gradual enough to give us time to nuke the thing into smaller pieces. |
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The interesting engineering challenge at that point will be to guide the fragments of moon rock so that as many of them as possible land on continental shelves, and thereby provide a partial solution to the problem of rising sea levels. |
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// What is the guarantee on this product? // |
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Why is there a guarantee on this product? If it fails, who ya gonna sue ... ? |
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Since your species has so far notably failed to develop efficient deflector technology, we recommend a simple and reliable alternative. <link> |
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That's interesting; why would that be happening? |
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So are you going to be writing a book at the same time as the
stuff falls from the sky? (category) |
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I do very much like the idea of making these helmets pyramidal, out of tinfoil. Sort of like an assault rife that doubles as a tie rack, because your ties need holding off the floor much more often than you need to go assaultin'. The helmet would still serve its primary function against moon fragments, but also block CIA mind control and enhance your psionic abilities. |
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Little do you know. They Walk Amongst You ... |
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Then again, not long ago one research team abandoned their carefully concealed secret base in Rochdale because of "all these bloody immigrants and kiddie-fiddlers" and moved back to a crater on the far side of your moon, stating that it was much more welcoming, the view was better, and it han a nicer atmosphere. |
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// also block CIA mind control and enhance your psionic abilities. // |
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Now THAT sounds like good value. Do you sell the instructions ? Presumably, mail order, from a P.O. Box in Lincoln, Montana ? |
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Why do your ties need holding off the floor? |
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If there were aliens alive on earth (or with access to our
internet), I'd like to think they'd post on halfbakery.com |
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XKCD says they can. See link. |
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////That's interesting; why would that be
happening?// |
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Tidal forces. The moon raises tides on Earth, and
those tides create a drag on the Earth's rotation.
Consequently, the Earth's rotation is slowing down
and days are getting longer. |
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At the same time, of course, that drag is speeding
up the moon in its orbit, which causes it to move
into a higher orbit. |
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Perhaps the light from the full moon exerts radiation pressure on the earth? |
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//That's interesting; why would that be happening?// |
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My theory is that the Earth was once periform and revolved at a much greater rate than the current 24 hour cycle.
The narrow end of the pear shape would have once jutted far above the atmosphere causing it to be totally irradiated and devoid of life.
A close call with a large enough object could have caused this section to break away from Earth and dramatically slow the Earth's rotation. |
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-It would explain why the moon spins at the rate of exactly one rotation per revolution of the Earth.
-It would explain why the moon is the same age as Earth and yet has no signs of past life.
-It would explain why the moon is moving away from Earth instead of towards it.
-It would explain the enormous size reduction of past life forms, due to the disruption of the balance between the mass of the Earth and centrifugal force.
-It would also explain the break-up of Pangea as the planet reformed itself from a piriform shape to the current oblate spheroid shape we all know and love. |
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It would explain a lot of things. |
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God created spiders as an apology to men for the mess he made
when he created woman. Spiders are God's way of keeping
women from poking around in men's sheds, which are private
places. |
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//My theory is...// Yes, that's a lot easier to
understand than all that physics. |
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Incidentally, I don't think anyone has considered
the optimal design for a meteorite-deflecting
helmet. I can think of two possibilities. |
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(1) Make the helmet like an enormous 'fro,
preferably several tens of metres across, out of
something spongy (say, sponge). This would
decelerate the meteorite over the thickness of the
helmet, reducing the peak force. It would also
mean you'd keep the meteorite, which would be
cool. |
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(2) Make the helmet in the shape of a Wintsman-
Euphig solid, which is basically a cluster of tall,
narrow pyramidal spikes with logarithmically-
curving sides. Unless the meteorite strikes either
the tip of a spike, or the region in the exact centre
of a ring of spikes, it will be deflected sideways
smoothly. This will, like the 'fro helmet, cause the
peak force to be reduced in intensity (though
longer in duration). |
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(3) Make the helmet in the shape of a cube of
tinfoil, with one of its diagonals running east-west.
This will work fine as long as the meteorite hits it
while you're not wearing it. To be safest of all,
never wear it. |
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(4) Provide the helmet with an array of miniature
missiles and a targeting system, to pre-emptively
attack incoming meteorites. |
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// Make the helmet like an enormous 'fro |
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The Seventies Meteor Helmet. |
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I want mine to look like Achilles helmet, but with an Occam's razor on top to split any meteors in twain. |
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//Yes, that's a lot easier to understand than all that physics// |
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I understand the orbital physics you are talking about, just not the math associated with it.
Are the physics of my theory that unpossiblistic? |
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//Are the physics of my theory that
unpossiblistic?// |
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Probably. Which way up is your pear? Pointy end
up, or pointy end sticking out sideways? |
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The only way a planet can be non-spherical is if
there is a very very precise balance between
centrifugal and gravitational forces. This means
that planets can be slightly-squashed spheres if
they spin quite quickly. But they can't be *very*
squashed - they can't be big flat discs, for
instance, because of internal shear (which is why
Saturn's rings couldn't be solid - the inner bits have
a shorter orbital period than the outer bits). |
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If the pointy end of a pear-shape is pointing up (ie,
axially), then it's effectively a mountain. A really
big mountain like that will simply be squashed
down by gravity, though you might get away with a
small one (a few tens of miles high, maybe).
Indeed, the Earth is very slightly pear-shaped, but
the differences from a sphere are very small. |
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If the pointy end is pointing sideways, then it
might be stable if the planet spun at just the right
speed; but
there's no way such a shape would form in the first
place. Also, it would be unstable. If the top of
the peak were just a little higher, it would
experience more centrifugal force (and slightly
less gravity) and so would tend to get higher still.
Or if it sunk a bit lower, the reverse would happen
and it would sink lower still. |
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If you look at all the other large bodies in the solar
system, they are all either spherical or very
slightly flattened spheres - none is pear shaped. |
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// slightly-squashed spheres // |
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[pertinax], the moon pulls up on the water in the ocean, creating a
tidal bulge. The rotation of the earth pushes that bulge off to one
side. The bulge pulls on the moon from that off-center position,
causing the moon to be pulled along with Earth's rotation. The pull
speeds up the moon, which means it centrifuges further out from
Earth, and, because it is making a longer orbit, takes longer to go
around, so it seems slower. |
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To visualize, get a weight on the end of a string and swing it around
and around. It pulls on your hand, which is like the tidal bulge. If you
look close, you will see that when you speed it up, your hand is
actually making a circle ahead of where the weight is, which is like
the off-center tidal bulge pulling on the moon. And if you keep pumping it up and let out string, or if your string is elastic, you will get
bigger, slower circles. |
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... until the string breaks. |
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It only seems fair that at SOME point in this discussion the readers should be informed that " Seveneves " is the new Neal Stephenson novel regarding the destruction of our moon and the subsequent meteor storm that destroys the earth as we know it. |
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Much other stuff takes place - it IS a Neal Stephenson book, so you get a lot of reading for your money. |
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//Pointy end up, or pointy end sticking out sideways?// |
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Sideways of course. With enough spin any irregularity in distribution of mass will eventually force a planet away from oblate spheroidality and into scalenicity. |
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// The only way a planet can be non-spherical is if there is a very very precise balance between centrifugal and gravitational forces. This means that planets can be slightly-squashed spheres if they spin quite quickly. But they can't be *very* squashed//
//then it's effectively a mountain. A really big mountain like that will simply be squashed down by gravity// |
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Well... yup, that would all be true, except that an extreme piriform shape would effectively have two separate centers of gravity and would not really what you'd call 'rotate' so much as 'wobble'.
In this scenario you then end up with a moon-sized lifeless mountain the same age as the Earth just waiting to break away if given the right conditions. |
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//look at all the other large bodies in the solar system, they are all either spherical or very slightly flattened spheres - none is pear shaped.// |
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We know very little about the characteristics of exoplanets and our own little backwater is a very small sample. There are many other non oblate spheroid spinning objects in the Universe though. |
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On hydrostatic equilibrium:
According to the definition of planet adopted by the International Astronomical Union in 2006, planets and dwarf planets are objects that have sufficient gravity to overcome their own rigidity and assume hydrostatic equilibrium. Such a body will normally have the differentiated interior and geology of a world (a planemo), though near-hydrostatic bodies such as the proto-planet 4 Vesta may also be differentiated. Sometimes the equilibrium shape is an oblate spheroid, as is the case with Earth. However, in the cases of moons in synchronous orbit, near unidirectional tidal forces create a scalene ellipsoid, and the dwarf planet Haumea appears to be scalene due to its rapid rotation.
Also;
A rotating star in hydrostatic equilibrium is an oblate spheroid up to a certain (critical) angular velocity. An extreme example of this phenomenon is the star Vega, which has a rotation period of 12.5 hours. Consequently, Vega is about 20% larger at the equator than at the poles. A star with an angular velocity above the critical angular velocity becomes a Jacobi (scalene) ellipsoid, and at still faster rotation it is no longer ellipsoidal but piriform or oviform, with yet other shapes beyond that, though shapes beyond scalene are not stable. |
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There has been no recent work on the theoretical shape of an Earth that has a higher angular momentum. It seems to have sort of died along with Poincaré. |
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To the mystery-mobile Scoob! |
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