Interstellar Definition and 140 Threads

I might get a bit of a reputation for space talk, here :P So, I'm familiar with the concept of Photon Sails, but I was wondering how effective these would be? To make sure we're on the same page, I'm talking about using a highly reflective surface to propel a spacecraft by hitting it with a...

I've got a question that I am stumped on right now Show that if the Galactic angular velocity \Omega of an interstellar cloud is > sqrt(4piG\rho/3), the cloud can not collapse in the radial direction. Estimate \Omega and compare it to the rotation rate of the Galaxy.

Hi, I asked a theoretical question here a month or two ago and someone was able to help me. I have another: Imagine an interstellar race. Starship 1 heads from Earth toward Alpha Centauri at a constant rate close to the speed of light, then makes a loop and returns home. Ship 2 is faster, and...

Homework Statement A uniform, spherical planet of mass M and radius R moves SLOWLY with an essentially uniform speed v through a cloud of interstellar dust particles, whose density is ρ. The dust particles are attracted towards the planet, and some of them would eventually fall onto its...

Homework Statement A typical dust grain has a radius of 10-7 m and a mass of 10-14 g. How many dust particles are there in a molecular cloud containing 1000*Masssun of dusty gas if 1% of the cloud's mass is in the form of dust grains? Homework Equations The Attempt at a Solution...

For simplicity consider an unmanned probe to a star in our neighbourhood say 10 to 20 LY. Most discussions of this concentrate on speed and power. But what is the fastest realistic velocity? 40,000 MPH (~ 1/10 of 1% of light speed)? Even at this speed interstellar dust banging away at the...

Ever since I saw stephen hawkings universe doc's, I've been wondering about one creative scenario he presented. surround our sun with solar energy satellites. Draw and store the energy in the satellites. satellites fire this energy in beams (synchronized) into one satellite which then...

Interstellar travel is always a problem in science fiction: you can't have the hero hibernate for millions of years whenever he or she wants to travel to another star, but it's annoying when spaceships just magically move faster than light. However, wouldn't length contraction from special...

Okay I don't really know where to put this because it's not really physics and all, so I'm leaving it here. Also apologies if this sounds weird or if the physics is just plain wrong, it's 2.30 AM in the morning where I am and I didn't want to forget it when I woke up. Suppose that at some...

Somewhere in our Galaxy resides a cloud of neutral hydrogen gas with a radius of 10 pc. The gas density is 10^7 atoms/m^3. (a)How many 21-cm photons does the cloud emit every second? (b)If the cloud is 100 pc from the Sun, what is the energy flux of this radiation (in W/m^2) at the Sun...

Hello all, I am new to the Forum and have no formal Physics training. I have an interest in the subject mainly due to other pursuits. I am reading Joe Haldeman's The Forever War. I would definitely recommend this book to anyone with an interest in Time Dilation or Humans vs Aliens at...

Homework Statement A uniform, spherical planet of mass M and radius R moves SLOWLY with an essentially uniform speed v through a cloud of interstellar dust particles, whose density is ρ. The dust particles are attracted towards the planet, and some of them would eventually fall onto its...

Howdie. This question started from what was to be a "simple" analysis of heating the air in a room. So much for simplicity when you start to question what exactly is heat and what is happening to atoms and molecules. SOOOO...the question I have (which will have bearing on my INITIAL quest)...

Hi, I'm new to SR and GR in general. In fact, I just discovered Lorentz equations a week ago. And that got me thinking too, just as it must have happened to you too. I like maths, but I'm more the kind of artistic person. And I was wondering what would be the sight of a traveller, on board...

Problem:"An interstellar cloud with a radius of 10parsecs and a mass of 10000 Msun is contracting. How long does this take? (The cloud itself has no pressure)

This is an old paper but at least it is a start for a discussion on the affordability of interstellar travel. http://www.andrews-space.com/images/videos/PAPERS/Pub-InterstellarTransportation(200307).pdf If one uses some marker for a nations, or a group of nations wealth, will...

I am just "trying" to watch interstellar TV... The detection range in lightyears is R = \sqrt{\frac{\text{EIRP}\cdot A_{e}_{r}\cdot\text{twc}}{4\pi\cdot\text{SNR}\cdot B_{r}\cdot k_{B}\cdot T_{sys}}}\cdot\frac{1\,\text{ly}}{9454254955488000\,\text{m}}, where \text{EIRP} = P_{t}G_{t}...

Should we send an interstellar (unmanned) probe to Alpha Centauri? Would it be much more expensive than a manned mission to Mars? According to Wikipedia, velocities as high as 0.10c are possible with hydrogen bombs. That means that ~40 years flight time to the nearest star would be possible...

Hello folks, I was wondering about a possible probe sent to alpha centauri which would be able to do a deep scan of the system, maybe for a month, and then send back results. I then wondered, that if the probe was exposed to different gravitational conditions, let's say favourbly, would...

click me If this were april first, I'd dismiss this in the blink of an eye :confused: While I'm not against the idea as such, what kind of first impression about our species would this give anyone who does receive it on the other end?

Homework Statement A spacecraft with its astronaut has a total mass at rest of 10^5 kg. The astronaut is to travel to a star 10 light years away at a speed such that she only ages 1 year in her frame of reference a) the quantity 1-v/c where v is her speed with respect to Earth is? b)...

Problem: Interstellar space has an average temperature of about 10K and an average density of hydrogen atoms of about one hydrogen atom per cubic meter. Compute the main free path of a hydrogen atom in interstellar space. Take the diameter of an H atom to be 100 pm. Here is what I did. I...

The presence of interstellar extinction makes stars appear dimmer and appear more “distant” than they truly are. (This is true for individual stars and for clusters of stars). Does dust affect the observed angular size of a star cluster (assuming the distribution of the dust is smooth)? That...

I know it would take an obscene amount of energy to put any type of manned spaceship within reach of neighboring stars... but why can't tiny probes, maybe the size of a baseball, or if necessary a marble, be sent instead? Say we explode a nuke to fling a few of these 'spaceballs' towards Proxima...

Homework Statement Suppose that the density of interstellar dust is uniform along the direction of the plane of the galaxy, but that its vertical density is given approximately by \rho = \rho \o exp - ( z / 0.15 )^2 where z is the distance from the plane of our galaxy in kpc. If the...

Hey, can anybody tell me what the estimate is on the mean mass of a particle in the interstellar medium? I would guess around 1-10 proton masses?

Hi all, I am writing you because in my research I need to characterize the space environment for an interstellar flight from the Earth to Alpha Centauri (more exactly proxima centauri). So i need densities of atoms and ions (in terms of cm^-3), energies (MeV), magnetic field strength...

According to Relativity, if a ship traveling at nearly the speed of light through interstellar space diffuse atoms (mostly Hydrogen, becase simply that is the most abundant atom in the universe, right?) would strike the front of the ship with increased mass, causing radiation. My question is how...

Cosmic-ray electrons and positrons propagating in the Galaxy produce diffuse gamma-rays via the inverse Compton (IC) process. The low energy target photon populations with which the cosmic-rays interact during propagation are produced by stars, this stellar light being reprocessed by...

Hi all. First post and all that, so I hope I don't do anything wrong, and that if I do, you'll cut me a little slack :P Anyway, onto the question I'm wanting help with: A J-shock in a Herbig-Haro object is propagating through neutral hydrogen gas at speed 100km/s. The gas has number...

Theorically speaking, what force could stabilize a wormhole?

I have been trying to do this questions for about 30 minutes right now and its a one dot questions. I think I am converting the atoms wrong. Could someone help me? A typical region of interstellar space may contain 10^6 atoms per cubic meter (primarily hydrogen) at a temp of 100 K. What is...

A few quotes from various sources suggest there is quite a bit of material in the Oort Cloud, maybe enough to threaten interstellar space travel: “The Oort cloud is an immense spherical cloud surrounding the planetary system and extending approximately 3 light years, about 30 trillion...

Ahad's virtual bridge might have to charge a toll fee: http://www.astroscience.org/abdul-ahad/firstarktoalphacentauri/interstellar-propulsion.htm :!)

I am trying to get a basic understanding of the physics of the interstellar medium and the current models which describe it (FGH and McKee-Ostriker). A first question arises regarding the possible assumption of a gas in ionization equilibrium, in which ionizarion and recombination occur at...

well the textbook question is (transfer me over to hmwk help its ok) 2 Civilizations are evolving on oppposite sides of our galaxy (d = 10^5 ly) at time t = 0 in the galaxy frame of reference, civilization A launches its first intersteller spacecraft , 50,000 years later, measured in the...

http://science.nasa.gov/headlines/y2004/27sep_shieldsup.htm?aol667632 At the above link, it appears there is a high temperature cloud of gas has been colliding with the solar system. What could keep a cloud of gas at such a high temperature in the interstellar medium?

Originally posted in College Level Homework help but I got no responses there. Please help if you can. I am studying for my qualifier and doing problems out of Jackson. I am stuck on this one... any help would really be appreciated... I am unsure how to begin: Jackson 7.15 The partially...

How long will it be before we reach alpha centauri, i was on a thread on Fark.com yesterday about going to Mars and it interstellar travel came up. I figured you guys (and girls) would prob have a better idea on what ideas are out there right now. this was my post: do you know how impossibly...

(read *lost* in general discussion- thought itd be better if i posted this again here) interstellar travel. i wanted to know the possibility of it actually being able to happen. iv got coursework to do, and it can be on anything we want it to be on, as long as its got summat to do with...