3,601 reputation
1117
bio website about.sjrdesign.net
location Boulder, CO
age 31
visits member for 2 years, 9 months
seen Jun 29 at 7:04

Professional geophysicst/astronomer who also writes the blog, "Exposing PseudoAstronomy," and runs the podcast by that name.


Jul
23
answered Why did the asteroid belt between Mars and Jupiter form as it did?
Jul
22
comment What will the universe look like for anyone falling into a black hole?
@dagorym - I expanded the answer.
Jul
20
comment What is so special about iron?
Thanks jball - changed it.
Jul
20
comment What will the universe look like for anyone falling into a black hole?
Thanks, Andrew. Yeah, I meant if you could "stand stationary." I know a lot of folks say that the singularity would get larger and larger, but my understanding is that the singularity is "where God divided by zero" ... in other words, Relativity doesn't work, and we really don't know what to expect. Obviously light can't escape it (we're inside the event horizon), and the last I read, it's an infinitely small point (or infinitely thin ring). How does a geometric point fill your view?
Jul
19
answered Why aren't space probes like New Horizons sped up in space?
Jul
19
comment Is Jupiter a failed star?
Thanks, Warrick, That number was coming to mind, but I couldn't remember where I heard it. What throws it off, though, is that people are reporting exoplanets with a minimum mass of up to 20 Jupiter masses. So, yeah ...
Jul
19
comment What will the universe look like for anyone falling into a black hole?
The more I think about this, the more I'm not sure about the blueshifting. Someone please verify/correct this?
Jul
19
answered What will the universe look like for anyone falling into a black hole?
Jul
19
comment Has a human ever perished in space?
You need to better-define your question. Technically speaking, "Earth's pull" lasts to the non-existant edge of the universe. Do you mean, say, the political definition of "space" which is 60+ miles? Or in Earth orbit? Or something else?
Jul
19
comment Metal Dilemma: Only very few civilizations per galaxy
Aaron, perhaps it's the bad Google Translate version of the article, but while it was a bit difficult to follow, I didn't see anything in it that contradicts what I stated. Maybe you could provide a better translation? I don't actually study galaxies, so I can't get much more detailed than I already did on the galactic habitable zone nor provide you with numbers that would help elaborate. Maybe someone else can?
Jul
17
answered Is Jupiter a failed star?
Jul
17
comment What is the cosmic “Axis of Evil” problem?
Not related to axis of evil stuff, but you should not be referencing Journal of Cosmology. They are in no way peer-reviewed, advocate pseudoscience, and the editors have clear agendas in mind. I realize this is somewhat of an ad hominem and the article you link to could be perfectly legit, but most stuff I've read of theirs is, well, this is a G-rated board.
Jul
15
comment What is so special about iron?
Agreed, thanks for expanding. Guess I didn't want to get too detailed in there, other than to really give another "practical" example of why this concept is important.
Jul
15
comment Would it be interesting or useful to map objects' current (predicted) locations?
This is actually something I wondered during my undergrad astronomy classes but I never asked. I think part of the answer is that it's not worth doing in general because of the computation required (e.g., to do so with individual stars in a galaxy, galaxies in a cluster, etc.) and also because gravity also travels at the speed of light so the objects are affecting us from their current seen locations rather from where they "really" are today. But this is a guess on my part which is why I'm posting it as a comment and not as a full response.
Jul
15
answered What is so special about iron?
Jul
15
answered How does the central peak in moon craters form?
Jul
14
answered Metal Dilemma: Only very few civilizations per galaxy
Jul
13
comment Can the Hubble telescope bring any star into focus?
@Joe: This all has to do with angular size (and a teensy bit with brightness when you are talking about the moon and sun). Yes, Neptune is really close compared with the Triangulum galaxy (M33). But the angular size of Neptune is 7 arcsec while M33 is 73 arcmin ... that's a difference of a factor of 600x.
Jul
12
comment Universe Expansion
@Warrick: The analogy is imperfect since yes, the dots do expand. The better analogy is the raisin bread one, but that doesn't illustrate quite the same thing (2D expanding in 3D). ghoppe is somewhat incorrect, though. At present, galaxies do NOT expand, as they are held together by gravity which is stronger than the expansion force. Same with clusters. There WILL come a time, though, when gravity is NOT strong enough and galaxies will actually be dragged apart by the expansion of space. Don't remember off-hand what that time-frame is, but it's at least in the billions of years away.
Jul
8
answered Universe Expansion