# Tag Info

## Hot answers tagged planets

9

Lets first think about how much energy this needs. You've asked for spurious precision, but I'll save that til the end because no-one wants to see all the tedious decimal places in the workings (and if they do, they can repeat the process themselves). You want an orbit with a period of precisely 365 days, each 24 hours long. Via Kepler's third law, we can ...

9

Since nothing exactly like this exists on Mars, let's look at the best real-life example of what you're describing: A crater. On Mars Hellas Planitia is one of the oldest and largest craters on Mars. It was formed during the Late Heavy Bombardment, which started around 4.1 BYA. At more than 7 km deep, it's one of the deepest craters in the solar system. ...

8

You have a few issues that the planet and its residents need to confront Size of ant: average 10mm Size of human: average 1650mm Ratio: 1:165 For your giant to be same ratio from a human, your giant's size: 272.5m high Due to the Square Cube Law (volume / weight and surface area increase at different rates as size enlarges) you run into issues when you ...

8

A scifi trope I've now seen more than once (KSR's Mars trilogy and later works, also Stross' Saturn's Children) is the idea of a habitat on rails that drives around Mercury remaining on the terminator (eg. the night/day boundary). This involves the train being propelled by thermal expansion of the rails caused by sunrise to ensure that the system can operate ...

7

Sulfur-based life is pretty unlikely, for the same reason that life on Earth isn't oxygen-based. Sulfur, like oxygen, usually only likes to form two covalent chemical bonds. Thus, you can in principle have chains of sulfur atoms of varying lengths with with different atoms attached to either end, but that really isn't enough variety of structure to permit ...

7

This is a major undertaking. You will need a civilization somewhere between 1 and 2 on the Kardeshev Scale, and you will need to do it manually. If you have a Dyson sphere you should be able to muster up enough energy to pull it off. Start by boiling the oceans. Raising the global temperature to over 100C should do the trick. Alternatively, microwaving ...

6

Honestly, we already live in the future. Autotranslation of spoken words and conversion of distances, especially in the context of a limited and precise vocabuary, seems entirely practical by the time someone has mastered interstellar travel. Alternatively: What would be the minimum information they would have to exchange to work as a functional sniper ...

6

TL;DR: maybe. Orbital stability is pretty borderline, and some fairly unlikely circumstances have to arise to produce something that looks like maybe it will fit your needs. Tidal effects and orbital resonances will mess with the figures below, so they're only approximate Lets start with a star the size of the sun, putting the orbit of the planet at 1AU. We ...

6

Formamide can be formed by the condensation of carbon monoxide and ammonia. https://en.wikipedia.org/wiki/Formamide A reducing planet with an ammonia / methane atmosphere is plausible. If there is also some water, one could imagine atmospheric water undergoing photolysis to generate a small percentage of free hydrogen and oxygen. Hydrogen will head up and ...

6

Hmm, it might be possible...but unlikely. To respond to the clarified question (can be found in the comments), let's assume that by "take up the sky" you mean that each planet has almost a 90 degree angular diameter when viewed from the other planet. This will take up 50% of the night's sky. (Getting 100% is impossible due to the curvature of a spherical ...

6

Valles Marineris reaches a depth of 11 km, while Olympus mons reaches 25 km of height, together they make the gap you envision. Olympus mons is thought to be 200 million years old, while Valles Marineris should count 3 billion years. Therefore the lower limit for existence of such a height difference seems to be at least 200 million years.

6

Navigation wouldn't be any different than it is on Earth. Consider Pluto: It has a much more eccentric orbit than Earth does, but navigation on Pluto's surface would be exactly the same. The sun rises in the 'East', it sets in the 'West', and North and South are likewise just like they are here. That's all based on the rotation of the planet, orbit has ...

5

Humans exist at a certain size because of the structure of their bones, muscles and their metabolism. Humans cannot exist too far beyond their normal size for many reasons. One issue is the fact that bone strength increases with the square of the bone size whereas weight increases with the cube of size, another issue is the ability to retain heat. Too large ...

5

Are supercritical oceans of CO2 possible? That depends on how you define "ocean", but yes. Making them more liquid-like just requires a cooler environment, easily achieved with a Venus-like world that happens to be somewhat farther from its sun than Venus is. How would it behave? That depends on just exactly how liquid-like it gets. There are two not-very-...

5

Mercury’s axial tilt is only a few degrees so the ideal place to build a base would be at one of the poles. With the sun effectively circling the horizon a modest sized crater would provide areas of perpetual sunlight on the rim, areas of perpetual shade at the bottom and areas where sunlight and shade alternated every 50-60 days or so around the crater ...

5

It's an interesting scenario. The major problem is that ring systems tend to be quite low-mass in comparison to their parent bodies. For example, measurements by Cassini indicate that in the case of Saturn, the ratio of ring mass to planet mass is $M_R/M_p\simeq2.7\times10^{-8}$ (Iess et al. 2019). Even in the notable case of 1SWASP J1407b, whose ring system ...

4

The problem with supercriticality is that due to the circumstances under which it arises, you lose any clear distinction like "liquid/gas" as you might get at the surface of a conventional ocean. Instead, you get a smooth increase in density and viscosity from the gas phase bits of the atmosphere into the supercritical bits, like a fog that just gets thicker ...

4

The sniper's team's jobs will be obsolete long before we can travel between stars. The technology already exists to make self targeting rifles that are more accurate than nearly any human sniper, but in your more advanced civilization, this tech would easily be way beyond human limitations. This means that the guy holding the gun IS the spotter, and the ...

4

Explosives on the Earth's surface, no matter their power level (short of ejecting significant chunks of the crust) will never change the Earth's rotation rate or orbit. Nor will a reaction drive of any kind -- with the exception that if its exhaust, after exiting the atmosphere, is still above Earth's escape speed, some tiny fraction of its thrust will act ...

4

Two factors could make it possible (if extremely unlikely): 1: The planet has very low gravity. The weight of the giant is so small that its muscles can hold it up and move it around, even with a very small muscle cross section to mass ratio (square-cube law). The mass itself, however, will be a major issue, since intertia will be great. The giant would ...

4

Since we're already making the comparison to software algorithms, I'll follow that route. Antivirus software can only protect against signatures, patterns, and actions that it knows about. It doesn't learn or adapt on the fly - it cannot. Instead, effective antivirus relies on near constant updates to counter new threats as those threats become known and ...

4

The child's existence is the key to a metaphysical doorway which is one layer of a multiple layer barrier between our world and the plane where the Scarlett King waits. This doorway is the outermost layer of the barrier, the layer closest to our world. The six brides would have opened all of the other layers of the barrier if they had lived, but since they ...

4

The short answer is "if they were adapted for lower light levels, they would have to protect their eyes". Brighter stars emit more energy all through the EMR spectrum, including the infared. However, the intensity experienced during a creature's evolution would be less a function of the star's spectral range, and more the proximity of the planet to the ...

3

So, there are a few things here. First of all, base 10 is NOT a safe assumption. The only reason humans use base 10 is because evolution gave us ten fingers, and even WE don't use base 10 for everything, we use a lot of base 12 and base 16 too. Second: all members of sniper/spotter teams are snipers. One member or the other may be the one actually ...

3

The Earth is rotating too slowly for our scientist's liking, and it's also getting slower all the time due to gravitational tidal drag and other factors. This is currently happening at a rate of about $\mathrm{7.3×10^{−13} day/day}$, which is also the fraction by which the Earth's angular momentum needs to be topped up. Let's specify the propulsion system ...

3

I'm pretty sure it can't be done with a gas giant. The problem lies in the stability of the habitable moon's orbit. An object's orbit around its primary is stable as long as it is within the Hill sphere of the primary (the region dominated by the primary's gravity), while being outside the Roche limit (the distance at which tidal forces will break the ...

3

Younger Dryas was an abrupt event with roughly the feature you require, except the periodicity. The Younger Dryas (around 12,900 to 11,700 years BP) was a return to glacial conditions after the Late Glacial Interstadial, which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM) started receding around 20,000 BP. ...

3

Tl;DR: probably no. But it might not even be required for what you want. The (simple, rigid-body approximation) for the Roche limit is defined as $d = R_M \sqrt[3]{2{\rho_M \over \rho_m}}$ where $R_M$ is the radius of the primary, and $\rho_M$ and $\rho_m$ are the densities of the primary and satellite respectively. Given constant densities, the Roche limit ...

3

The elliptical orbit couldn't be terribly long, as all life would cease when it reached the furthest points away from the sun(s) UNLESS there were some sort of greenhouse effect in place. Otherwise, migration wouldn't be too much different than it is on Earth among some tribes and migratory animals. When it's too cold, you go to where it's hot and vice versa....

2

Simply put, sane or not, if he were any scientist worth his salt, he'd understand that he cannot make a day any closer to the 86400 seconds that it currently is defined as. How precise can we be? The length of the year is ~365.2422ish days. This is the oft-cited duration of a tropical year, the "mean time between between vernal equinoxes", but is in fact ...

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