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About Steel

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    Rocketry Enthusiast
  1. You've answered your own question there. You'd need to find a way to travel faster than light.
  2. Questions

    Exactly. IRL you need about 7500 ms-1 of horizontal velocity at LEO, in KSP you need about 2000 ms-1. In both cases you only have to be about 150 km up, so you have to burn much longer and much more towards the horizon in real life.
  3. Dark Gravity discussion

    Sort of. It's a difficult concept to try and get across via text. Simply (or as simply as I can) the big bag happened simultaneously everywhere in the universe, because at the point of the big bang the entire universe was in the same place because it was an infinitesimal singularity. You are right, it is a bit of a simplification. Over large scales things are moving away from each other due to the expansion of space. Of course, over small distances gravity dominates and things stick together - that's why we have stars and a solar system and Donald Trump.
  4. Dark Gravity discussion

    It was everywhere. Because, as far as we can tell, all space is expanding, which means if you rewind to the beginning of time there was no space in-between everything and the entire universe was in one infinitesimal point. Thus the big bang occurred everywhere at once, from this infinitesimal point which was the entire universe
  5. Dark Gravity discussion

    I didn't think either approach should be ruled out or favoured over the other until the evidence say so. There are tens, if not hundreds, of alternative theories of gravity to vanilla GR, and almost universally they agree with some observations but not others, or are not self-consistent.
  6. Dark Gravity discussion
  7. Dark Gravity discussion

    I believe there are still some WIMP candidates still in play, like the right-handed neutrino. Also the above study has not actually ruled out axions totally, they could still exist with a mass outside the range that was excluded by the observations.
  8. Dark Gravity discussion

    There are still plenty of other dark matter candidates other than axions. Also, if there is a field there are likely particles. After all, particles are just local excitations of a field (i.e. the Higgs boson is just a local excitation of the Higgs field)
  9. This is where your problem is. The definition of the Schwarzschild radius is NOT Newtonian, you have to do GR and solve the field equations to get a general solution. Luckily for high school teachers all over the world, it just happens that if you do the basic assumption V_esc = c and then solve with Newtonian gravity you get the same result as if you'd done a full solution of the Schwarzschild metric for the black hole. This is a great way to make the topic more accessible and easier to visualise, but is not a true reflection of the physics going on. Don't make the mistake of thinking that this means Newtonian gravity is going to help you much where a black hole is concerned.
  10. Well according to the Wikipedia page, an Alderson disk would be more massive than the Sun and require more material to build than is present in the Solar system. I'm going to guess that this means it would take more to build than a ringworld (depending on the size of the ring world, I suppose). An Alderson Disk on it's own probably doesn't have a very large habitable zone, you would need life-support to enlarge it. There are also numerous questions about the direction of gravity at any given point of the disk as well as questions about how its would retain an atmosphere. It's worth noting that while a ringworld is a sci-fi idea, the Alderson disk is not. It originated as a setting for a fantasy swords-and-sorcery world and so the physics of it are sketchy at best.
  11. The event horizon is an infinitesimal boundary, therefore it's physically impossible to be at the boundary, you can only be either inside or outside it. The other scenario isn't much better, because you cannot transfer information across the boundary from inside -> outside.
  12. Random Science Facts Thread!

    You're quite right, I was mis-remembering my particle physics! The Higgs mechanism is responsible for some fermion masses too, however the interaction with the Higgs field that results in mass is different for fermions and bosons.
  13. Random Science Facts Thread!

    In fact the Higgs mechanism only really explains why a certain group of bosons have non-zero mass (and some other more subtle, but still important, particle physics things). EDIT: I'm wrong here, see below
  14. Well there aren't any crew... so not a lot
  15. Random Science Facts Thread!

    /pedantic{In that case a human brain cell is in the middle, a whole human is a few orders of magnitude larger than the middle}