1,124 reputation
418
bio website dotancohen.com
location
age 36
visits member for 2 years, 8 months
seen Apr 13 at 5:47

Jul
19
comment Black hole Cyg X-1 doesn't seem dense enough
Thank you, I did not realise how rapidly the density goes down with mass. A bit later I'll sit on that for a 1 million solar mass object, just to see what values of "reasonable" are! Thanks!
Jul
18
comment Black hole Cyg X-1 doesn't seem dense enough
Thank you! I see it now mentions in the article that the radius of the event horizon is 26 km.
Jul
18
accepted Black hole Cyg X-1 doesn't seem dense enough
Jul
18
asked Black hole Cyg X-1 doesn't seem dense enough
Jul
13
accepted Will Pluto be in the ecliptic plane when New Horizons passes by? Was this deliberate?
Jul
13
comment Will Pluto be in the ecliptic plane when New Horizons passes by? Was this deliberate?
@dmckee: I refer to the amount of energy required to move a device from 1 AU distance from the Sun to 40 AU distance from the Sun (due to the increase in gravity potential from the Sun). That energy requirement would go down as Delta-V goes down, but equipping the craft with more Delva-V capacity would be the method by which more energy is invested in getting to that distance (in the form of rocket fuel).
Jul
12
accepted Pressure loss after water goes up and back down 7 stories
Jul
12
accepted Cannon on spacecraft: hitting yourself
Jul
12
asked Will Pluto be in the ecliptic plane when New Horizons passes by? Was this deliberate?
Jul
9
comment Cannon on spacecraft: hitting yourself
Right, the speed hasn't changed but the velocity vector has.
Jul
9
comment Pressure loss after water goes up and back down 7 stories
Thank you. There would not be a heating pump installed. I also feel that 16mm is very thin, but that is the standard. In fact, most homes run that thin plastic pipe all the way from the heating tank to the home with no insulation! At my last place I insulated the pipe myself.
Jul
9
comment Pressure loss after water goes up and back down 7 stories
@Nathaniel: Yes, that is exactly the concern. We have had solar heaters on the roof in previous apartments, but never 7 stories up! I've actually already discredited the idea due to the waste of water while waiting for the hot water to get to the faucet, but I would like to either dispel or confirm the suspicion that their would be a pressure loss.
Jul
9
comment Pressure loss after water goes up and back down 7 stories
@John: Thanks, I meant either 16mm or 1.6cm. I think that NASA once made a similar mistake in the vicinity of Mars!
Jul
9
revised Pressure loss after water goes up and back down 7 stories
deleted 1 characters in body
Jul
9
asked Pressure loss after water goes up and back down 7 stories
Jul
9
comment Cannon on spacecraft: hitting yourself
Thank you, you perfectly describe the mechanical system as I perceived it.
Jul
9
comment Cannon on spacecraft: hitting yourself
@Alfred: Not quite! You are thinking if the projectile is shot in the same direction as the space station. However, if the new velocity vector has an equal tangential component to the original and a zero radial component, but a different inclination, then it will still be in a circular orbit. This is known as an inclination change. It is how we have geostationary satellites launched from ~30 north of the equator!
Jul
8
comment Cannon on spacecraft: hitting yourself
Actually, this is a great answer as it does mention why there is doubt. As to the idea that shooting behind leads to a lower orbit and shooting forward leads to a higher orbit, the "in between" that you are looking for is to release the projectile with quasistatic separation speed from the space station. They will then orbit together.
Jul
8
asked Cannon on spacecraft: hitting yourself
Jul
4
accepted Does water in the drain follow the distance-squared rule of force?