Anonymous asked: But actually it is a lot of crying.
Yeah… especially since NASA went boom.
So I got a question.
"How do intergalactic astronomers bridge the nexus of selection criteria for different redshift galaxies to study galaxy evolution?"
And… wow, we have a winner for the Most Syllables in a Question Ever Submitted to this Tumblr* award. Let’s, uh, break this down a bit.
"How do astronomers who study how galaxies evolve deal with the fact that we literally can’t see every single galaxy at different distances?"
…Well, to be honest, a lot of crying is involved.
Haha, kidding (kind of). But this is actually a really good question, one that astronomers wrestle with all the time.
You see (warning: pun ahead), it’s not hard to see (oh man, there it is) galaxies that are close by—but more distant galaxies appear to be much fainter and smaller. Pretty intuitive, right? It’s easy to see a dim lightbulb if it’s close by. But if you’re trying to see a light that’s a million miles away, it better be a pretty big and/or bright light.
This is what astronomers call selection criteria. It’s a big problem when we’re trying to study how galaxies evolve, because we’re trying to get a complete picture of how all galaxies form—but when we look at old and distant galaxies, we can only see the ones that also happen to be big (mass-selected) and bright (flux- or luminosity-selected).
And that makes it hard to come up with definitive statements about the properties of galaxies at different redshifts. We can’t say things like “the average ____ of galaxies at redshift z=____ is ____” because we have a skewed sample. We can’t know for sure if big/bright galaxies have the same chemical composition (or star formation rate, or whatever) as small/dim galaxies.
How do astronomers deal with that?
Well, other than crying, astronomers just kind of… deal. We don’t have perfect instruments, and we’ll never be able to observe every single galaxy ever, and astronomers know that. So they take that into account when they work. They try to make statements only about specific mass or luminosity ranges, and more importantly, they try to estimate the number of galaxies that we’re not seeing.
Cause if we can’t be perfect, we should at least know how not-perfect we are! (Note: This is only a good philosophy in science, not in self-esteem.)
Credit: Uh… this is one of those things I just sort of picked up after reading lots of research papers.
Anonymous asked: What does "Des etoiles" translate to in English? I'm too lazy to use google translate. :D
"Des étoiles" translates to "(the) stars" in French. (I’m a French minor, haha.)
spookyactionsatadistance asked: Hey! I read a new york times article recently about a theorized phenomenon of black holes called the Firewall (and the resulting Firewall Paradox), which would, if it exists as posited, be yet another reason not to jump into a black hole. It was pretty interesting and I'd love to learn more about it if you have/ can find knowledge! Thanks!
I’m guessing this is the article you read, right? (For those of you who haven’t read it, it’s a really good article and does a fantastic job explaining things in a simple way.)
I’m not a black hole expert, so I’d have to do some serious reading if I’m going to cover anything this article hasn’t already said. Do you have any specific questions about the firewall paradox, or do you just want me to take the whole concept and break it down without delving too much into the physics behind it?
If you have specific questions, I’d be happy to discuss it with you over private messages (but keep in mind that I’m not a black hole physicist, so really the best I can do is try to reason through papers with you). If you just want me to do a series explaining the whole topic (pun totally intended), just let me know!
Send me questions?
I don’t have any super great ideas for my next post(s).
Please please please let me know if there’s something astro-related that you want to learn about (and/or want broken down into bad puns and food-related metaphors)?