The dumb questions thread

[humbleman]

Imagine you have an object with mass you want to move over astronomical distances, and which you can not encase or otherwise directly push, and which is also electrically neutral so magnets won't help either. I can think of one and only one way to move such an object: have it orbit another body (say an asteroid) and push *that* body so it's pulled along by its gravity. Am I missing an obvious alternative?

What's the hypothetical maximal acceleration you can give the asteroid-target object system without losing the target? I know you can't go beyond the asteroid's gravitational acceleration at whatever altitude you have your target in orbit, but is there a precisely calculable even lower limit above which the orbit deteriorates into a highly eccentric one so you still lose your satellite at its periapsis? Or is *any* amount of continued acceleration eventually going to lead to this? (Preliminary calculations using the higher theoretical maximum suggest that it would take at least 3.5 years to accelerate Ceres to 0.1c without pushing hard enough for loose rocks on its surface to be left behind, more if you want to keep something in orbit.)

What would be the energy requirements for accelerating an asteroid (let's not be skimpy, take Ceres, anything smaller than that and we're probably too slow to be of much use) at such a rate?

If tried to do some of the calculations with Wolfram Alpha, but I seem to get the wrong kinds of units in the result: I was expecting watts and got newtons for Ceres gravity * Ceres mass.



I'm considering the logistics of moving a wormhole entrance to an interstellar destination. I'm assuming macroscopic wormholes can be created and stabilised for all practical purposes indefinitely, but in their creation the laws and speed limits of causality in 3d-space still have to be obeyed: Or in other words, the shortcut through a higher dimension the wormhole represents cannot be used for its own creation. I'm also assuming that it is, partly for this reason, impractical to create the entrances more than a few light-seconds, light-minutes at most, apart, and the only way to get a useful interstellar wormhole is to move it conventionally. And since the wormhole doesn't know the difference between a ship, a container hull, and a planet surface, and will transport them all across indiscriminately, the only safe place for it is in orbit and the only safe way to transport is is to pull it gravitationally.

I don't think that that idea would work, any constant amount of thrust would eventually unbind the orbit. You might be able to get it to work by timing thrust pulses to specific points on the orbit that are calculated to maintain the system (like pumping on a swing). An alternative would be to not try to maintain an orbit, but just shoot asteroids by the wormhole one after the other. Each one would add some energy as it goes by.

It would be pretty hard to use that technique to decelarate at the target with no infrastructure in place, though, wouldn't it?

Anyway we want to open trade with  Gliese_667_Cc through the wormhole before the end of the 24th century!

We need a terminal velocity of no less than 0.1c, and an average acceleration to get us to that velocity in no more than 50 years!

My hidden agenda is actually to argue that even if stable macroscopic wormholes and their at-will creation are possible (which they probably aren't), the logistics of installing one under reasonable assumptions are so overwhelming that they aren't actually a solution to the vastness of space. Your contention that it's even harder than I may have thought seems to prove me right.

I'd still like to put some rough number on just how overwhelming, say as a multiple or fraction of global primary energy consumption during the acceleration phase assuming 100% efficiency with the cheapest method that gets us to a reasonable speed within mere decades.

OK guys, what is the catch!

Wormholes?

Seriously?

Here in a forum of science and you talking of sh*t wormholes?

Plus, looking for energy efficiency wormholes... ha ha ha ha... and trying to find a "cheap one" on sale perhaps on eBay... ha ha ha ha...

Last loony who calculated the construction of a wormhole says the mass of hundreds of stars is needed... we can't even put a foot on the Moon and here the discussion is about building a wormhole in space, as if you are building a shopping center around the corner.

So, the dumb question is, how the hell the idea of a wormhole was invented?

In order to this loony idea of wormholes to be "science", is necessary a solid evidence or fact as a starter point, because in science theories can't start with imaginary physical entities, as the loony of poor Albert did with his relativity.

So, how this wormhole came to appear in science rather than be what it should always be, just a childish imagination?

 

[skepticalbip]

Okay, I'm guilty of asking the wrong question, although the answer lies close by those given.

We are traveling through space. Well, we're on a planet that's traveling through space, so I guess either way, we are at least in some sense traveling through space. Sometimes, we are going one direction and six months later, well, how do I say this, still going in the same overall direction but slower (and I guess, in a way, pointed in the opposite direction). But still, we are going in some overall direction. North? Nay. Some degree with an inclination?

I came up with the sphere question looking to add a third dimension to a compass heading. I figured some angle would be needed. We got to the moon, well, unless the moon got to us while we hauled ass away from it as it gained speed on us as we increased our thrust towards it slowing our run from it ... unless we weren't.

If I'm right and space is a medium that we pass through, then each point we pass is a point not moving. This lends us the opportunity to project a background 3-d checkerboard graph paper kind of perspective that enables us to find places of rest that neverless finds celestial objects passing furiously by. But, in what darn direction? I don't even know the words to use.

This is one of the problems addressed by the theory of relativity (and where the theory got its name). Newton assumed a universal reference frame (your static 3D grid) - this ends up causing a hell of a lot of serious problems when trying to describe the nature of the universe such as measurements of the speed of light.

Uncle Albert described a universe where there is no preferred reference frame. Any object's motion or position can only be described with respect to some other object or objects. Assume a space ship zooming through the solar system. Its velocity and direction can only be described with respect to some other reference object. Its velocity will be measured differently if measured with respect to the Sun, Earth, the Moon, Mars, Jupiter, Alpha Centauri, etc. All these measurements will be different, correct and can be translated to what would be measured from other reference frames.

 

[spikepipsqueak]

Help

I want to build a geodesic dome with the boys.

The video I have seen of it shows the completed article but is otherwise of very little help.

Dumb question. If I just build triangles on themselves will the dome form of its own accord, or is there more I need to know?

 

[steve_bank]

I want to build a geodesic dome with the boys.

The video I have seen of it shows the completed article but is otherwise of very little help.

Dumb question. If I just build triangles on themselves will the dome form of its own accord, or is there more I need to know?

There should be plans on the net.

 

[bilby]

I want to build a geodesic dome with the boys.

The video I have seen of it shows the completed article but is otherwise of very little help.

Dumb question. If I just build triangles on themselves will the dome form of its own accord, or is there more I need to know?

You need a variety of panel sizes - at least 2 different triangles for a simple 2v or 3v design, up to six different sizes for a more complex (but more elegant) 4v design.

Calculators that give the necessary strut, panel and hub dimensions and quantities based on a given target dome radius can be found here.

 

[spikepipsqueak]

Thanks.

 

[Emily Lake]

I want to build a geodesic dome with the boys.

The video I have seen of it shows the completed article but is otherwise of very little help.

Dumb question. If I just build triangles on themselves will the dome form of its own accord, or is there more I need to know?

You need a variety of panel sizes - at least 2 different triangles for a simple 2v or 3v design, up to six different sizes for a more complex (but more elegant) 4v design.

Calculators that give the necessary strut, panel and hub dimensions and quantities based on a given target dome radius can be found here.

It can be made almost entirely of the same size equilateral triangles. The only place you need something different is along the bottom edge, where the shapes will end up being different to get a straight edge. A geodesic dome is half of a buckyball, which is all made of the same size triangles

ETA: I see what they're doing there in the link. They're making the pentagonal structures planar, and incorporating the dome curvature into the triangular interstices between the pentagons - That requires different sizes of panels. When I've made buckyballs in the past, I allow the hexagonal structures to be planar, and the curvature arises from the hexagonal interstices between the hexagons... which only requires one size of panel.

 

[Jayjay]

Is there a shape, if made into a mirror, would reflect all light right back to its source? I.e. angle of reflection would always be 0 degrees, no matter which way light is coming from?

 

[Keith&Co.]

Is there a shape, if made into a mirror, would reflect all light right back to its source? I.e. angle of reflection would always be 0 degrees, no matter which way light is coming from?

Its called a corner cube, or retroreflector. A prism with mirrored sides.

we used it to verify the internal accuracy of the system that measured missile misalignment with collimated light.

And like most everything else i ever became an expert with, it's been replaced by a software app...

It is way ass freaky to look into one.

 

[Keith&Co.]

Is there a shape, if made into a mirror, would reflect all light right back to its source? I.e. angle of reflection would always be 0 degrees, no matter which way light is coming from?

http://www.precisionoptical.com/corner-cube-prism.php

 

[Cheerful Charlie]

https://dahp.wa.gov/sites/default/files/Domebook_2_1971smaller.pdf

Dome building depends on how big you want to make it. There are actually numerous different dome breakdowns. I fooled around with models of domes long ago. The book listed above is old but has the basics. You can probably find lots of other sources on the net. There used to be some dome software around on the net, but I have not looked at what is available now. You tube seems to have some reviews of some of this stuff.

 

[Loren Pechtel]

Is there a shape, if made into a mirror, would reflect all light right back to its source? I.e. angle of reflection would always be 0 degrees, no matter which way light is coming from?

As others have said, it's a retroreflector. Small versions of this are all about us. The two common uses I see are on highway signs on the interstate--note how they shine brightly in your headlights, you can read them much farther away than you would expect; that's because they're made of a bunch of retroreflectors. The second common usage is the highly reflective bits you see on some pieces of outdoor equipment meant to be used in proximity to roads (for example, backpacks) that create shiny bits to make you more visible to drivers at night. We also see them in lane-marking dots--the exposed edge is a retroreflector.

 

[steve_bank]

The cotner cube was mentioned. Spherical and parabolic mirrors.

Place a small reflective ball at the focal point of a sperical or parabolic mirror and there will be relection back to the source. The amount depnds on the setup and accuracy of the optics, and will never be 100%.

Anatur telescope makers use autocollimation to align the mirroers. Put a flat mirror over the tube of a Newtonian reflector and shine light into the eypiece.

 

[Angry Floof]

Is it possible to simulate a severed corpus callosum?

 

[bigfield]

Is it possible to simulate a severed corpus callosum?

Try using an HDMI cable.

 

[DBT]

Is it possible to simulate a severed corpus callosum?

Chocolate, consumed daily with gusto.

 

[Angry Floof]

Google is not forthcoming. It keeps throwing medical information at me. I just would like an explanation for why low dose aspirin comes in such an odd number for the dosage. 81mg. 81. Why not 80 or some other tidy number as we've come to expect for dosages? Diphenhydramine 25 mg makes sense. Fish oil 1,000 mg makes sense. 81 mg, no. Someone pls xpln.

 

[skepticalbip]

Google is not forthcoming. It keeps throwing medical information at me. I just would like an explanation for why low dose aspirin comes in such an odd number for the dosage. 81mg. 81. Why not 80 or some other tidy number as we've come to expect for dosages? Diphenhydramine 25 mg makes sense. Fish oil 1,000 mg makes sense. 81 mg, no. Someone pls xpln.

Marketing?

The manufacturers of the 81 mg aspirin can honestly advertise that their aspirin is more powerful than their competition that has 80 mg aspirins.

 

[George S]

Google is not forthcoming. It keeps throwing medical information at me. I just would like an explanation for why low dose aspirin comes in such an odd number for the dosage. 81mg. 81. Why not 80 or some other tidy number as we've come to expect for dosages? Diphenhydramine 25 mg makes sense. Fish oil 1,000 mg makes sense. 81 mg, no. Someone pls xpln.

Aspirin is quite old. The original Aspirin tablet was 5 grains. The grain is a unit of measurement of mass, and in the troy weight, avoirdupois, and Apothecaries' system, equal to exactly 64.79891 milligrams.*

5 grains = just less than 325 mg. 325/4 = 81 (rounded) so 1/4 tablet is then 81 mg or 5/4 grains.

*https://en.wikipedia.org/wiki/Grain_(unit)

 

[Kharakov]

Is it possible to simulate a severed corpus callosum?

Simple.

Sprinkle with salt in between dips into a bubbly high oxygen + low concentration sugar water solution, with specially designed hemoglobin that decarbonates on a catalytic electrode on a flow through pump/filter system.


ETA: Stimple. Apparently I read stimulate. A severe corpus callosum, such as yours, cannot be simulated.