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# Tag Info

## Hot answers tagged physics

27

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, ...

16

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 ...

9

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 ...

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. ...

6

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 ...

5

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 ...

4

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 ...

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 ...

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 ...

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 ...

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 ...

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

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 ...

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 ...

1

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 ...

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