# Tag Info

21

The moon's albedo is around 0.1, meaning it reflects about 10% of the sunlight that hits it, for a peak illuminance of a few tenths of a lux (sources on albedo and lux). Even if the moon were a perfect mirror, it would only reflect 10x as much light and would only cast a few lux, making its illuminance during a full moon only a few hundredths of a percent of ...

13

Let's break it down by type of system, as planet-moon or planet-planet systems will have different constraints from star-planet systems. Planet-moon/planet-planet system Looking at planet-moon or binary planet systems, the answer to your question will always involve standing on a decent sized moon and looking up at the host planet. A moon by definition has ...

9

Since I feel like I should turn my comment into an answer: I am basically directly copying the formula from this site: Where: t = time lapsed from initial time to time of loss of consciousness (s) Vr = volume of enclosure (m3) Vp = volume of a person (about 0.1 m3) Li = initial oxygen concentration (21% or 0.21) Lf = final oxygen concentration (12% or 0.12)...

9

First of all, for lunar regolith we can neglect reflection and just consider scattering. This paper simulated the scattering properties of the lunar surface, and came to values around 22% of reduced reflectance for incidence angles between 32 and 57 degrees. I haven't been able to find a comparable chart for talcum, beyond generic statement like "...

8

First thing to remember is that when you're close to a spherical object, you can only see a portion of its surface (the horizon). Therefore the anglular diamater of some body with radius $r$ viewed from a distance from the surface of $h$ will be $2\sin^{-1}\frac{r}{r + h}$. (this also means that the maximum angular diameter of a celestial object (such as the ...

7

Let's assume that we're standing on a normal Earth in a normal universe, and suddenly the fine-structure constant changes. What would happen? My answer is based largely on Adams (2019). As a note on notation, I'll let $\alpha_0\equiv1/137$ be the value of the fine structure constant in our universe. We need $\alpha\gtrsim7\times10^{-5}$. If it was lower, ...

5

Many mollusks often have both hemoglobin and hemocyanin in their circulatory systems. I found lots of unsourced mentions online for this, but only one from a university (ugly as the page may be). About snails: Blood is colorless, and has both hemoglobin and hemocyanin in most species About clams: There are a few examples of where haemoglobin [sic] is ...

4

In a rogue planet with no external source of heat, the surface of the planet might be expected to have a fairly uniform temperature. The total mass of Earth's atmosphere is about 5.15×1018kg. It is made up of approximately 78.09% nitrogen 20.95% oxygen 0.93% argon 0.04% carbon dioxide There are also small amounts of other boring things which aren't really ...

3

Is there any current (or extrapolated) scanning technology that would be able to scan for deposits in a planetary crust through 16 meters of ice and LOX There are three important things here. Any information about the permeability of solid nitrogen or liquid oxygen to conventional ground penetrating radar techniques is either very hard to come by, or ...

3

That's not really what Penrose process is for. The "Penrose process" has the rather limited effect of extracting some rotational energy that surrounds a spinning black hole. It isn't a tremendous amount of energy extracted, and I think you have other ideas how to get energy from small black holes. Once you have the energy in fungible form, use it ...

3

can they use the penrose process to fire a laser/particle beam at the black hole, using the black holes gravity to accelerate the kinetic energy of the photons, and then fire that beam at an enemy ship? First of all, photons would always move at c, because of the physics we know today. We can't accelerate nor decelerate them. At most they would blue shift ...

3

It depends on the people and their metabolic rate, and whether you can scrounge up something alkaline. People trapped in a cave may not be keeping up with breakfast, but they are still burning calories internally. Figure out the amount of "food Calories" (kcal) all the people together would need to eat to stay at their present weight. So if you ...

3

Use your talc for mirrors! First, contemplate the economics of a future nation. Given that it's the future (not necessarily very far in the future), there is one man, the Consumer, who owns all the corporations, minerals, rockets, politicians, religious and charitable foundations, eyeballs, etc. Provided he is happy you have more or less 100% market ...

2

TL;DR: No. I spent ages faffing about with superconductor parameters and pinning force densities and tensile forces before realising that the underlying premise was all wrong. Let us first consider the magnetic field of a magnetar... it is famously Quite Strong. But consider also that magnetars are pretty small: 10km radius. The field strength of a magnetic ...

2

I also wanted to know the answer to this question; searching online has given me answers from 10 miles, to 350 miles. I went through and did the Rayleigh Scattering calculation for an Earthlike atmosphere at STP that contains no dust, pollution, or condensation. For every mile visible light travels (I used 500 nm light) 98.404% would pass through unscattered;...

2

I dont think it's possible. Time dilation requires energy. There's two ways to do it: travel closer to the speed of light or use a mass to distort the local space-time (or a combination). So instead I'll try to give you an alternative: build the people you want in the last section of the trip. We have been 3D printing bodyparts for a few years now. If you ...

2

Short Answer: Many of those images might be designed to show astronomical objects though imaginary telephoto lenses. According to my reserches, the largest possible astronomical object as viewed from the surface of a habitable or potentially habitable world would have an angular diameter of 22.9183 degrees of arc, or about 82,505.88 arc secondsi. Long Answer ...

1

On our planet we have found bloods of various colors, all depending on the type of metallo-protein used in the blood, but all of them use a single type of metal, be it iron, copper or whatever else. I would dare to say that, if there was any advantage, or at least no disadvantage, in having a bimetallic blood, we would have found it in some organism. Maybe ...

1

The "blood colors" stuff you'll find on the internet refer specifically to real organisms on Earth, and to the minor variations on these biochemistry themes that are obvious. For a completely novel biology (tree of life) from another planet, there are certainly enough plausible potentials for you to use any color you might like, including magenta. ...

1

According to the Wikipedia (https://en.wikipedia.org/wiki/Moon), the moon has an albedo of 13.6%, which means that 13.6% of the incident light is reflected/scattered by its surface back into space. As such, the max. theoretical gain is a factor of 1/13.6% = 7.4. That said, to achieve this brightness increase, you must use a very white substance that you can ...

Only top voted, non community-wiki answers of a minimum length are eligible