lpetrich
19 Mar 2009, 09:51 AM
I've thought of how one might recognize such objects, and here are some possible criteria:
Preferred materials. Their economics of resource extraction could well be significantly different from ours, especially if they are primarily space-based, preferring to land on low-gravity objects like asteroids and comets. What is easiest for them to extract may not be what is easiest for us to extract, and that may affect their choices of construction materials.
In particular, they may have difficulty extracting the rarer elements, like lead and gold and uranium, since asteroids and comets most likely lack the geological and biological effects that produce concentrations of such elements, a.k.a. ore bodies.
So they may use lots of aluminum instead of copper or gold for electrical conduction, and they may use lots of iron instead of lead for radiation shielding.
Isotope-abundance differences. Material from outside of the Solar System may have significantly different isotope abundances. Though it is certainly possible to fake such materials, by constructing materials with such isotope concentrations, doing so would be very difficult; simply consider the sorts of facilities that have been necessary for separating isotopes of hydrogen and uranium.
Such different abundances would be a result of using material that had condensed out of the interstellar medium at some different time and place, where enrichment in (relatively) heavy elements would have been different from that of the Solar System's parent material. This in itself may not produce relative changes in isotope abundance; what relative changes there might have been would require a more detailed study of Galactic chemical evolution.
Part sizes and shapes. Many parts are manufactured in standard sizes and shapes; this is especially true of parts that must interact or fit with other parts. This adoption of standards makes it much easier for different manufacturers' products to coexist, and it helps simplify the design of new products.
Standard sizes are often chosen to be some simple multiple or fraction of one's favorite unit of length. Thus, objects like nuts and bolts come in both English-unit and metric-unit standard sizes.
Extraterrestrials would likely have made the same decision to use standard sizes and shapes for their interacting/fitting parts, since doing so makes good engineering sense, but it is unlikely that they would have used our standard sizes and shapes.
Here's a simple example: nuts and bolts. Bolts have to be screwed into nuts and go through holes, which constrain their dimensions. Those that we manufacture are normally right-handed, but an extraterrestrial spaceship might use left-handed ones instead. And whichever handedness they come in, they would almost certainly come in sizes that do not match Earthling standard sizes for nuts and bolts.
Preferred materials. Their economics of resource extraction could well be significantly different from ours, especially if they are primarily space-based, preferring to land on low-gravity objects like asteroids and comets. What is easiest for them to extract may not be what is easiest for us to extract, and that may affect their choices of construction materials.
In particular, they may have difficulty extracting the rarer elements, like lead and gold and uranium, since asteroids and comets most likely lack the geological and biological effects that produce concentrations of such elements, a.k.a. ore bodies.
So they may use lots of aluminum instead of copper or gold for electrical conduction, and they may use lots of iron instead of lead for radiation shielding.
Isotope-abundance differences. Material from outside of the Solar System may have significantly different isotope abundances. Though it is certainly possible to fake such materials, by constructing materials with such isotope concentrations, doing so would be very difficult; simply consider the sorts of facilities that have been necessary for separating isotopes of hydrogen and uranium.
Such different abundances would be a result of using material that had condensed out of the interstellar medium at some different time and place, where enrichment in (relatively) heavy elements would have been different from that of the Solar System's parent material. This in itself may not produce relative changes in isotope abundance; what relative changes there might have been would require a more detailed study of Galactic chemical evolution.
Part sizes and shapes. Many parts are manufactured in standard sizes and shapes; this is especially true of parts that must interact or fit with other parts. This adoption of standards makes it much easier for different manufacturers' products to coexist, and it helps simplify the design of new products.
Standard sizes are often chosen to be some simple multiple or fraction of one's favorite unit of length. Thus, objects like nuts and bolts come in both English-unit and metric-unit standard sizes.
Extraterrestrials would likely have made the same decision to use standard sizes and shapes for their interacting/fitting parts, since doing so makes good engineering sense, but it is unlikely that they would have used our standard sizes and shapes.
Here's a simple example: nuts and bolts. Bolts have to be screwed into nuts and go through holes, which constrain their dimensions. Those that we manufacture are normally right-handed, but an extraterrestrial spaceship might use left-handed ones instead. And whichever handedness they come in, they would almost certainly come in sizes that do not match Earthling standard sizes for nuts and bolts.