3,621 reputation
1117
bio website about.sjrdesign.net
location Boulder, CO
age 31
visits member for 2 years, 10 months
seen Jul 29 at 3:44

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


Jun
27
comment Why Aren't Saturn's Rings Clumping into Moons?
Sure, if you'd like to make one that's a reasonable file size for inclusion here, go for it. Those movies were over 200MB each, if memory serves, so I didn't embed it.
Jul
27
comment Why is infrared imagery of Mars' surface sharper / richer in contrast than that from the visible spectrum?
No. Really, what Olin said. Remember also that you're looking at different solar incidence angles, like when you take a picture of the full moon versus a crescent, the full moon looks less sharp than the crescent just because of the way the sun is hitting it. The IR mosaics that Google uses are from THEMIS which took images at late afternoon sun, while the optical (probably either Viking or Mars Orbiter Camera) were usually closer to noon sun.
Mar
31
comment Andromeda/Milky Way collision: How, and how accurately, can a galaxy's lateral velocity be measured?
Thanks for coming on here, Kyle. FYI if you respond to or ask questions in the future, StackExchange does support LaTeX markup, just enclose in the $ to do it (that was my edit to your post).
Feb
27
comment What would happen if the polar ice caps of Mars melted?
The above accepted answer is not correct as it is currently stated: If you want to say that it is ENOUGH to cover the planet in an ocean, then that's fine, but due to the dramatic topography (over 25 km of relief), the would-be oceans would pool in the northern hemisphere, Valles Marineris, and Argyre and Hellas basins.
Dec
6
comment In astronomy what phenomena have theory predicted before observations?
K, updated Pop III by just removing it.
Dec
6
comment How are exoplanets confirmed?
I could answer your question until you stated that you've seen some confirmed exoplanets with periods 10-100s of years. Could you provide a source for that?
Dec
1
comment What are the facts that allow accepting the Oort cloud theory?
Alright, looks like I was remembering wrong (universetoday.com/11283/…). It's Kuiper Belt disks we see around other stars. I've revised my answer.
Nov
26
comment November 25th 2011 partial solar eclipse visibility from Christchurch, New Zealand
So, did you see anything? I think that's the real question at this point. :)
Nov
25
comment November 25th 2011 partial solar eclipse visibility from Christchurch, New Zealand
Alright, answer is corrected. I also had your longitude as W instead of E. That's why Starry Night did +11 instead of +13.
Nov
21
comment Liquid Water in “mid-ice” on Europa. Mechanism?
Updated since I got the paper.
Nov
20
comment Liquid Water in “mid-ice” on Europa. Mechanism?
His response was "tomorrow." Guess he doesn't want to VPN in.
Nov
17
comment Does anybody actually do astrometry in the 21st century?
Geoff, I'm adding a comment instead of answer because this isn't a full answer, but I'm pretty sure the answer is "yes." You may periodically hear about leap seconds being added or taken out of years at midnight on New Year's, and I'm pretty sure those come from astrometry measurements on the March equinoxes.
Nov
16
comment Best time of the year to see the star Alpha Centauri in Chile, Santiago
I need to not write answers here when I'm about to go to bed. Corrected.
Nov
12
comment How does the central peak in moon craters form?
Hmm. That's not really a good model for the cratering process - at least not into rock. I could see that applying to ice, like on Enceladus or Europa. It's the effective explosion/vaporization of the projectile that creates the crater in the first place. Now, the splash-up in that movie is reasonable, sorta, though probably much higher than would happen in normal rock.
Nov
11
comment How to concisely explain apparent retrograde motions of planets?
To add, the way I normally (when I remember) remember prograde and retrograde is that the sun, over the course of many days relative to the stars, appears to move west to east. Going with the sun (the planets when prograde) is what ancient cultures who worshiped the sun would probably think of as "good" -> "pro." When it goes the opposite direction of the sun - relative to the stars over many days), that's against normal motion -> "retro."
Nov
11
comment How to concisely explain apparent retrograde motions of planets?
Yeah, got my terms mixed up, I wrote that when I was watching the clock to run for the bus. But, I disagree with your point that I got my overall motions wrong -- it's just how I think of the motion. I always think about it relative to the stars, so I just didn't clarify (which I now have) about the diurnal motion.
Nov
10
comment How does the central peak in moon craters form?
This is not actually going to form a central peak in any way. You'll form a crater, and it's neat, and I actually recommend doing this in a clear tub (like disposable containers you get in a 5-pack at the grocery for $3) and use layers of different-colored things like flour, oreo crumbs, graham cracker crumbs, etc. But you will not get a central peak, and it's not a great analog because the marble will not be destroyed in the impact, which you need to do this.
Nov
3
comment 2012: Is there some astronomical event happening?
Can't edit my comment, so I'll just add -- people on this site will usually vote down a question/statement on pseudoscience topics, so that was probably why it was downvoted. I've actually only downvoted one person's post before, I think because it was completely illegible.
Nov
3
comment 2012: Is there some astronomical event happening?
I didn't down-vote your question.
Nov
2
comment What is a good introductory text to astronomy
With my recent PhD, I've been looking at beefing up my "library." I keep thinking I need to get C&O, but right now it's running around $150 on Amazon, and there are more important books for me to get. Plus, C&O 2nd ed. is ©2006. Astrophysics is a very dynamic field (no pun intended) and I'd expect that a lot of what's in there is likely out of date. I'd guess the fundamentals aren't, but anything relating to any currently active area of research (star formation, CMB, stellar evolution, solar system formation ...) would need some serious revision.