# All Questions

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### evidence on the equation of state for dark energy?

If dark energy contributes mass-energy density $\rho$ and pressure $p$ to the stress-energy tensor, then you can define $w=p/\rho$, where $w=-1$ gives a cosmological constant, $w<-1$ gives a big ...
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### How much solar energy hits a rooftop in Israel?

I was asked to today about the available plans (in Israel) to install photo-voltaic receptors on the roof and sell the energy. This is a legitimate plan and there are several companies that do this. ...
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### How are interplanetary trajectories found?

How are interplanetary trajectories that involve gravity assist maneuvers found? Examples: the MESSENGER spacecraft made flybys of Earth, Venus, and Mercury before getting into orbit the Juno ...
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### How does the average Mars-Jupiter distance compare with the average Earth-Jupiter distance?

One thing is certain: Mars can be further from Jupiter than Earth can ever be (when they're on opposite sides of the solar system), but Mars can also be closer from Jupiter than Earth can ever be. ...
406 views

### Rocket engines design & materials [closed]

Does anyones know which materials (or type of steel) are used to make rocket engines nozzles & combustion chambers? What are the tricks to reduce temperature of the engine except trying to cool ...
89 views

### Creating the opposite of an optical lattice

Is it possible to create periodic potentials that instead of creating a well for an atom to be trapped in, repulsed by that specific location? If yes, can we use this as a means to make artificial ...
170 views

### Smoothed particle hydrodynamics in cosmological N-body simulations

What is the role of smoothed particle hydrodynamics (SPH) in cosmological N-body simulations like the Millenium Run (performed with Gadget-2)?
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### What is the mass of the LEGO figurines being launched with spacecraft Juno?

What is the mass of the LEGO figurines being launched with spacecraft Juno? How much additional fuel will be needed to get them to Jupiter?
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### Could dark matter be expanded atoms, and dark energy expanded radiation? [closed]

After watching Lawrence Krauss' lecture 'life, universe, and nothing', an interesting idea lighted up in my mind. Is it possible that dark matter is just spread out matter waves and dark energy ...
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### How can we be sure that liquid iron/titanium droplets can form around particulates on hot Jupiters - just as they do on Earth and Venus?

I know that we have some solar system analogs. But is there a limit to it?
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### Is CO2 really a potent greenhouse gas for planets around M dwarfs?

The thing with global warming is that it absorbs infrared (IR) radiation from the planet and reradiates much of it back to the planet (whereas the Sun's peak flux is in the visible region, that is ...
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### How did micrometeorite flux change with the age of the solar system?

Do we also have functions for the micrometeorite flux on the Moon, Mars, and even any random body in space as a function of solar distance too?
174 views

### Why are Wilson lines the effective degrees of freedom for high energy partons?

I've read that Wilson lines are the effective degrees of freedom for high-energy partons, when you consider collinear gluon emission. But I'm struggling to find a readable account of this topic. Does ...
460 views

### Simulating eye diagrams

I'm trying to figure out how to simulate eye diagrams for communications systems using Python. I'm not sure I have the theory down completely, though. From what I could figure out using some old ...
1k views

### How to make mirrors give more authentic image of myself

My friend bought two normal mirrors from some shop probably IKEA, looking like this one: My images are different from the two. One is a little fatter and shorter, and the other a little thinner and ...