How much is "vastly different"?
If a difference in ratio of radii of 2 (and thus a surface area ratio of 4) satisfies the “vastly different” requirement, this is pretty easy to imagine:
Start with two roughly Earth-like planets (let’s call them “UE” and “LE” for “usual” and “little”...
Big Bounce =/= quantum bounce
Barrau and Linsefors’ model strikes me as an elaboration on the Tryon’s vague idea that the Big Bang (which, in B&L’s model, is better called “the quantum bounce”) is a large scale quantum vacuum fluctuation.
The simplified, personalized sketch on the model I...
Poincaré's recurrence theorem and "Tryon's moment"
It’s important to note that the observable universe appears not to be one of the dynamic systems for which Poincaré recurrence theorem. Stated informally, for it to apply a physical system, that system must be contained in a fixed volume...
The "nothing" theory of cosmology.
By most Big Bang models, the very early (< 10^-43 seconds) universe didn’t have distinct, measurable particles – one could reasonably say the entire universe was a single, indivisible “primordial atom”. In physics, to have motion (which is defined as change...
An excellent old causality violation illustration involving ansibles
Violating causality is equivalent to having an “effect before its cause”, which is a form of “sending information into the past”, or “receiving a message from yourself before you sent it”. So a good way to understand how the...
From non-technical explanations like wikipedia’s, I gather that the Higgs mechanism – a way that particles interact with the Higgs field – doesn’t give massive particles – elementary fermions, which include electrons and quarks – their mass. It gives mass to the two massive gauge bosons – the W...
To quote the NASA website article I cite below “no one knows for sure”. There are some best liked hypotheses, but no strong consensus on which, if any, are most true.
In short, that the ratio of the 3 stable isotopes of oxygen, 16 (~99.76% on Earth), 17 (0.039%) and 18 (0.201%) (more...
I think Cooperstock, Faraoni, Vollick’s 1998 The influence of the cosmological expansion on local systems contains a good technical paper explaining why the metric expansion of space isn’t noticeable on solar system scale. In section 4-"Cosmological corrections to the two-body problem in the...
Are galactic mergers common?
If we include collisions and mergers of galaxies much different in mass - big galaxies "absorbing" smaller ones, know as minor mergers - likely yes. Much of the complicated structure and irregular composition of spiral galaxies is believed to be due to such...
Having the ship ionize neutral hydrogen in the interstellar medium is certainly an option – the early Bussard ramjet studies included this possibility, using powerful shipboard lasers.
The early studies, and my introduction to the ramjet idea via Poul Anderson’s wonderful 1970 novel Tau Zero...
Scooped reaction mass + beamed power
I started this thread a month ago with a favorite idea for a transportation technology for a hard SF universe where individual humans not too different from our present-day kind could, in the course of their lifetimes, live around more than one star, that...
Bearing in mind that Bussard Ramjets have been designed only on a high, conceptual level, not in detail, even simulated, I think there’s a conventional answer to “how do they slow down”.
Because their electromagnetic scoops produce drag (which is equal to their maximum thrust when they are...
Definitions of "species", hybrids and hybrid speciation
That definition, which has come to be known as the biological species concept (BSC), and associated with Ernst Mayr’s 1942 book Systematics and the Origin of Species, from the Viewpoint of a Zoologist, is a common and popular one, but I’d...
A simple rule for array expressions in FORTRAN 90 assignment statement
Disclaimer: I’m a veteran (~30 year) professional computer programmer, and the first compiled language I ever used, in the late 1970s, was FORTRAN, but I’ve not used FORTRAN of any sort since the early 1980s, so know of...
Can speciation in nonhumans happen by choice?
I find this a complicated question because of its use of the term “choice” qualified by “human”, which in the context I read it is a psychological and philosophical one.
The question seems easier when applied to nonhuman species, such as those...