Posts by HDE 226868
I was the mod who deleted the comment - thanks for bringing this up. The main reason I deleted it was that I figured that the comment was primarily for the benefit of the poster, rather than the co...
Apologies for taking a while to respond to this. When I used the phrase "hasn't been discussed", I was talking about the meta discussion at hand, rather than prior discussions. I rejected the edit,...
Yeah, that's my fault. I wrote up an answer and posted it, but I deleted it shortly afterwards (and later undeleted it . . . and then redeleted it). I did so because I've been extremely active on S...
The Earth would be broken into pieces if the total energy delivered by the impacts was comparable to the gravitational binding energy of the planet. Earth is a sphere, so its binding energy is $$U=...
The shell variant of a Dyson sphere consists of an artificially-made shell of material about 1 AU in radius encircling a star. The sphere captures most of the star's energy and stores it for future...
The known charge-conserving decay modes of free neutrons all involve the production of a proton, an electron and an electron antineutrino: $$n\to p^++e^-+\bar{\nu}_{e}$$ This beta decay is why, out...
Neutrinos have extremely low masses, and it's quite easy for them to reach high energies and speeds. As such, it almost always makes sense to treat a neutrino as being relativistic. I've been doing...
Yes, it can. We can determine the distance to the source if we have an idea of what's causing that shift in velocity. Let's say that we have a source moving at a speed $v$ away from us. If it emit...
Before launching the site, we had a discussion on Codidact Meta about naming the category we currently called "Researched Q&A". Other possibilities we explored included "Hard science", our sta...
I've had a number of interesting conversations with people about how the cosmic microwave background (CMB) will evolve in the future. The CMB is the sea of photons left over from the epoch of recom...
Cox & Loeb 2008 performed one of the few simulations of the Milky Way/Andromeda collision of which I'm aware. It's not particularly easy to simulate a galactic merger, so the lack of detailed n...
[science-based] almost certainly should be removed - I think we can safely assume that a site called Speculative Science is going to require science-based answers across the board. If an post's not...
Question requirements I think it definitely falls on the asker to demonstrate first and foremost that the basic tenets of their idea are feasible. Their question should show that they've done a go...
Directly? No. Indirectly? Yes. As Renan indicated in their answer, material that enters a black hole cannot leave; the only way around this is through evaporation. Even then, the Hawking radiation...
The Copernican principle As L.Dutch pointed out, this would violate the Copernican principle, which essentially states that there's nothing special about observing the universe from any one place....
Yes, if the orbit isn't circular. Seasons can definitely occur on a tidally locked planet. Just like normal planets, tidally-locked planets don't need to have perfectly circular orbits. This mean...
This is actually a really interesting question. While there are many stars with orbits outside the galactic plane ("halo stars"), these tend to be old and metal-poor, as star formation in the halo ...
The Alcubierre drive not only allows but actually necessitates the production of event horizons at superluminal speeds - but not necessarily the sort you're looking for. It's been shown (Finazzi e...
My civilization is planning to being starlifting, mining a star by heating up portions of its surface and using a powerful magnetic field to channel the matter away from the star and into storage u...
The Alcubierre drive works by distorting space around a bubble: expanding space behind it and contracting space in front of it. It's a nice way to get faster-than-light travel without, well, techni...
The big problem with using radar in outer space is simply range. The received flux of a radar signal falls off as $1/r^4$ instead of the $1/r^2$dependence we're used to getting for signals emitted ...
This answer is meant as a supplement to notovny's. I agree with their conclusions (the scenario is impossible because of the instability of this Lagrange point, and the fact that the Hill sphere is...
Often, when I'm building a world, I want to start out by determining some of its key properties. Maybe I'm trying to calculate a habitable zone, or figure out how long a year would be on a particul...
This wouldn't work. The big issue is that stars make up only a few percent of the Milky Way's total mass - estimates vary by a bit, but I've heard numbers in the 3-5% range. For instance, McMillan...
The simple answer is a no. We've gotten some pretty good constraints from the Planck satellite; their final results indicated a dark energy density of $\rho\approx6\times10^{-30}\text{ g cm}^{-3}$....
