New answers tagged physics
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Lets just start with the Japanium question. Is there some magical element which would release energy only in the form of visible light photons? Well, maybe.
Nuclear isomers are excited states of regular atomic nuclei that can relax back to their ground state by the emission of a gamma ray. Now, not all gamma rays are created equal... it is basically a name ...
0
First of all, we need some metrics first.
The average adult human being is between 60 kg and 80 kg. For this question we will average this as 70 kg.
Let's also assume that the attacker's fist is in contact with the enemy for 0.5 seconds. The less time the fist is in contact with the enemy, the more force will need to be exerted in order to accelerate the ...
13
CoaDE was made with a lot of pretty pessimistic assumptions about laser technology. That's resulted in an interesting space combat simulation. The assumptions they've made aren't wrong, per se, but in order for them to be present in your fictional future too, you have to assume that laser technology has barely progressed from the present day.
Now, I Am Not ...
2
Rendering software simply calls this "Gradient Transparency"
... and what you are describing is not nearly as exotic as you may think. Translucence is a property of nearly all matter whereby it reflects some of the light that hits it, ands allows some to pass through. If you create a mass of translucent material it does not just reflect N-% of light, it ...
1
Why do you need a universal time measurement?
You can treat time intervals (such as years) as we treat currencies between countries. You have to pay tax to Empire Capital at Earth per one earth-year? Just convert that time measurement to your planet's years and collect local taxes on basis of that.
I would argue that one a multi-starsystems empire you ...
5
You want a system that everyone across the galaxy can observe together and has a regular periodicity. The solution is Pulsars
Pulsars are highly regular rotating neutron stars that emit beams of electromagnetic radiation from their poles. While not all pulsars are good enough for the most precise time keeping, the regularity of millisecond pulsars is even ...
0
Time is nothing but events. If you have any idea how much time passed between two events it's only because other events happened between those events.
Since your time measurement is meant to be universal let's make it about the universe. It started with the big bang and it'll end with the heat death. So why not just measure every moment in time as some ...
3
Maybe a Reflection Nebula
I don't think that there is a common name for the property of having a reflection gradient, in space. This scenario probably isn't prevalent enough to require a term for it. However there might be a common name for some other cosmic phenomena, that has reflection gradient potential.
For example if you are creating this reflection ...
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It is region of negative space-time curvature.
Positive space-time curvature, like that caused by a black hole, a star, or even a planet, causes light to bend inward towards the source of gravity.
The opposite, where light is deflected away from the "source" (regardless of what it might be) is effectively negative space-time curvature.
I'm not sure what ...
1
You can use any polymer which gets cured by exposure to light, if the curing results in a volumetric expansion, like polyurethane foam.
In the case of polyurethane foam the curing is triggered by exposure to outer environment chemicals, but it just needs the right dose of organic chemistry to have it triggered by light. I.e. dentists use a blue/violet light ...
3
There are a vast number of chemical reactions that are triggered by light. The study of these is known as photochemistry. This includes reactions such as those that occur in photosynthesis. Photosynthetic reactions cause the synthesis of glucose from carbon dioxide and water. As the densities of these materials are different it is clearly possible to trigger ...
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I wanted to comment on HDE's answer. It's an excellent answer (meaning I agree with it), but I wanted to add the following observations.
First, if you want your character to be a student, you'd best make him a graduate student. As HDE mentions, at the undergraduate level you might have a basic understanding of linear algebra and PDE's, but not enough ...
7
For this to work in a good story, you need something that is "bad" mathematics that is used by physicists and easily understood by readers (in its simplest form). The option that comes to mind for me is zeta function regularization, in particular Ramanujan summation. The most famous example of this was "proven" by my favorite mathematician and is below.
$$...
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For basic physics, you need (multivariable) calculus and linear algebra. This is basic literacy. You won't get anywhere in physics without them. There are some differential equations too, but one tends to learn that on a case-by-case basis as one studies examples.
For general relativity, you need Riemannian geometry. Talking about curved spacetime only ...
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Let's assume that this student wants to begin by understanding the twin pillars of modern physics: quantum mechanics and general relativity. There are several major tools in the toolkit of anyone studying both of these theories at a basic level:
Calculus (single-variable and multivariable)
Differentiation
Integration
Operators such as divergence, gradient, ...
1
How would a gun, that uses anti-gravity as propellant, work? Is it even practical?
The problem is that antigravity is ill-defined. Do you need some kind of negative-mass matter to generate it? Is it as weak as gravity? In that case, you'd need many, many earth-equivalent masses of negative matter to produce anything like a useful acceleration to fire a ...
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I think the only real advantage with the antigravity gun as described would be that you would not need propellant cartridges, although presumably you would need some power source so even that advantage might be limited. Traditional guns using high pressure gas derived from explosives can already project non-magnetic bullets at very high velocity.
The real ...
2
The antigrav field must be unidirectional, otherwise it's useless as a hand weapon in a planetary grav field - the field will jolt the gun upwards, far away from the huge mass down.
if acting on a single direction, there's no difference from a firearm - the handler will fill the same recoil as when firing the bullet by gun powder - the impulse still ...
3
If we focus on Earth, gravity attracts any body, bullet included, toward the center of the planet, along a vertical line.
The anti-gravity will work the opposite way, pushing the bullet away from the center of Earth along the vertical.
As such it's not of much use: unless the target is right above your vertical, you have no way to hit it, while with a ...
0
An alternative way to think about this perhaps is the terrain of the Earth. If you're in a valley surrounded by forest or bush (dark green, no reflections) then a full moon seems very dim. If you're on the top of a rolling hill surrounded by a snow-covered landscape then a full moon is almost dazzling.
Apparent brightness is about more than just the source ...
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X-ray lasers are kept down by how inefficient they are
Bomb-pumped gamma and x-ray lasers are also affected by very low efficiencies, but making a bigger warhead to pump them is relatively straightforward once you've solved the problem of targetting and shooting straight. There's no issue of waste heat, certainly.
near perfect wide spectrum mirrors
That'...
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1) Continuous and Pulsed beams
Actual power of pulsed laser is by order or two less than continuous one. You see, while pulse laser peak power is incredably small, the duration of the pulse is incredably small eather. So total energy per pulse is very small, and time between pulses is long enough to laser to cool down (by several orders longer than pulse ...
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Consider a world that is face locked to its "sun" - as Mercury was once thought to be and as the Moon is to earth.
Make the 'sun' side inhospitably bright and hot and unlivable.
Provide some form of thermal circulation system that allows the outward side not to freeze.
eg Hand wavium
Hot rivers
Thermal cycling of water or magma or ...
Maybe a hot rain's ...
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You're correct about the situations where you won't see a laser beam 'in flight', but remember also that you still won't see a 'muzzle flash' from a laser with the naked eye unless the wavelength is within the visible spectrum. Equally a laser passing through a medium will only be visible if it causes the medium to emit visible light, either by direct ...
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The above answers, particularly Stephen's first one which sets out the total power of the object and shows that it can be achieved while maintaining a habitable planetary system, cover most of what you ask, but you do need to consider the location of the object with regard to latitude and relative position of continents. Atmospheres and oceans will convect ...
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This is a brief answer meant to complement others.
Some years back I designed portable solar powered lights.
I did substantial testing of what could be achieved with various light levels.
There was much available information of what was "needed" for eg colour vision, fine work such as embroidery, general hobbies, day to day activities, finding your way ...
1
It needs mentioning that 'moonlight' isn't the same as 'nightlight'. Earth's moon reflects light during the day too but isn't generally significant compared to sunlight. A bright moon would add to 'daylight' as well as 'nightlight'.
Generally 'daylight' will be 'sunlight' + 'moonlight' + 'starlight' etc, and 'nightlight' will be 'daylight' - 'sunlight'.
...
1
In short, no. And for the TL;DR version, the long answer is also no.
M. A. Golding has given a lot of very good details about why in his answer. What it boils down to is that the moon receives about the same amount of light per square foot as the Earth does (at the upper atmosphere at least) and only a small proportion of that light is reflected from the ...
3
I did a bunch of math related to this concept on the Gearbox Borderlands (video game) forums. The original post is here (go to the bottom of the linked post and expand the "details" section by clicking the arrow).
Summary: An Earth-like setup (1) with a moon close enough to be $\frac{1}{6}$ the Sun's brightness would have civilization-destroying tidal ...
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If you need everything down to the quarks, you’ll need to simulate everything down to the Plank length $1.6 \times 10^{-35}$m and Plank time $5.3 \times 10^{44}$ seconds. That's the same length scale as strings.
Assuming your theory of everything works out to be something like string theory, you will need to compute the second derivative and running first ...
1
An intuitive approach
It is trivial to show from combinatorics that, classically, to represent the state of one atom, you must have more than one atom (in fact, many more than one atom).
The proof:
Let's assume your computer's memory works by storing bits in the spin state of an atom (the type of atom doesn't really matter). Atomic spins are quantized, ...
1
Don't overlook the composition of the planet's atmosphere. One with lots of moisture droplets floating around would diffuse the moonlight and increase the apparent brightness at the surface.
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Let's assume that your telekinetic bubble is massless, so in order to lift a human of mass $m$ you need a bubble which displaces that mass of air. At standard temperature and pressure air has a density $\rho = 1.225 \mathrm{kg/m^3}$, so we need to displace a volume of $m/\rho \approx 57 \mathrm{m^3}$.
Inflating your telekinetic bubble would not be quite ...
2
Physical advantage? Uncertain. Storywriting potential? Certainly.
"Lifting yourself by your own bootstraps", while a typical comic trope to give hypothetically non-flying characters flying abilities, ignores momentum and the laws of motion. But more importantly, it's boring. If you can stand on an object and lift it, you might as well just wrap yourself ...
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Bright enough to see by can mean many things. And the human eye can adapt to a very wide range of brightness values.
For example, the brightest noon sun can be 120,000 lux, but a very cloudy overcast day can be as low as 200 lux. Most people barely notice the difference because our pupils expand and contract to keep the perceived brightness roughly the ...
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Salt deposits are more stable, and they are white when powdered.
The bright spots on Ceres are hydrated magnesium salts and brine deposits. I don't know if hydrated salts can retain their water content on our moon, but salts like sea water salt are white by nature and have an albedo much higher than that of Regolith.
https://en.m.wikipedia.org/wiki/...
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If you can move the force field, then the energy to move oneself by standing / riding on the force field would be much less than to create a vacuum capable of lifting yourself.
A benefit, assuming you don't need to be conscious to keep the shape of the force field, is you could float while asleep to travel all night.
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I am not sure you understand the vast difference between the brightness of sunlight and moonlight when you ask for moonlight "almost" as bright as sunlight. And in fact the moonlight on Earth is quite adequate for many purposes, so it is possible that your story might work with moonlight no brighter than that of on Earth.
The magnitude scale for apparent ...
5
A Moon could supply a lot of light given the correct conditions. A much bigger moon in a much closer orbit would work, although such a situation might best be described as a double planet rather than a planet and a moon. Such a moon might well fill a large portion of the sky and even when only half lit by the sun would still be very bright especially if its ...
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The sun is about 400000 times brighter than the full moon. That's quite a lot.
The moon, despite looking quite white, is actually a surprisingly dingy grey with an average albedo of about 0.12 (equivalent to damp soil). If you painted the moon a brilliant glossy white and raised its albedo to 1, it would be a little over 8 times brighter, which still leaves ...
5
Moonlight has the (lack of) intensity it does because the Moon's surface (bright as the full moon looks at night, against the black of space) is quite dark -- about like worn asphalt pavement, gravel with tar between the pebbles.
To make it brighter, it would need to be covered with brighter material. One fine candidate is ice; a fresh ice surface, if it's ...
5
The fundamental problem is that there won't be an ocean left. And evaporating the ocean will destroy the biosphere from the heat.
The bottom of the ocean is 1000 bar of pressure. To stop the ocean from flowing in, you need 1000 bar of steam, which requires near star-core scale temperatures (400,000 K). And then you have a star on your planet, which means ...
2
Railguns. Because you are writing awesome fiction, not working for DARPA.
Coilguns have a limited upside for awesomeness. At the end of the day they are glorified doorbells. Yes they are more practical. So is commuting with your Prius as opposed to your jetpack. If you are trying to shoot things in real life, work on the coil guns and you may be on the ...
1
When people think of simulation, they often go directly to brute-force solutions that puts 100% of the strain on the given computer and its parts. Which is basically summarised as "try as best you can to fool a compiled working conscious person into believing something fake is real"
A more elegant solution (or fucked-up, depending on your point of view) ...
8
Coilguns (assuming current technology)
Ironically, rail guns have arguably received more attention for development in military applications. Unfortunately, however, there have been some major setbacks. The Navy is documented of having been developing rail guns as weapons as far back as 2005, yet as of 2018 there have been some hugely limiting problems:
...
2
Hm...
It does sound to me like you will just keep on putting Energy into your planet, which will make the whole system gradually heat up indefinitely even if it is a small ( < 10km) Ball of 600-2500°C. I don't have that much knowledge about the details as some of the others have, but how about this:
Try to have it as cool as possible (600-800°C is deep ...
57
Let's say your magical sphere has radius $r$ of 10km (so just poking up into the outer atmosphere) and is at a temperature $T$ of 1,250K (so glowing a nice warm yellow). The total radiative heat flux from the sphere is given by:
$$
Q = \sigma T^{4}. 4\pi r^2 \approx 1.7 \times 10^{14} \mathrm{W}
$$
Where $\sigma$ is the Steffan-Boltzman constant. A ...
8
There is no scenario in which the biosphere survives long. You have, at best, a few centuries. Say the fireball is as cool as possible while still being a fireball; 100 degrees celsius. All the oceans will continually drain towards the fireball and will boil on contact, as you said. This is bad news for your biosphere, because that's a huge amount of ...
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You are basically cooking your planet on a stove.
This magic fireball is an infinite source of heat, so it will sit there continually pouring heat into the planet's system. Water near it will be heated into steam, but the coolness of the water will not cool the fireball at all. This will cause the overall temperature to rise and rise until everything on the ...
3
It depends on what the eventual Unified Theory of Everything actually proves
Right now there are two theories about how small small can go. One theory is that space is quantized at the Planck scale. This is the belief that space is made up of discrete band-limited units and that nothing exists at a smaller scale than this. The second theory is that ...
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