[X] My Assistant

[elakdawalla]

Hi all, I thought I'd start a thread for people to dump questions that they might think are good for Planetary Radio. Planetary Radio is The Planetary Society's weekly half-hour podcast. It features an interview by producer Mat Kaplan with a space scientist, engineer, advocate, or well-wisher, and three regular segments: news headlines, "What's up" with Bruce Betts, and a Questions and Answers segment that I read. Each week, Q and A addresses one question, with half of the answer given at the beginning of the show, and half toward the end, each half lasting between 1 and 2 minutes. I get lots of questions submitted but the majority of them can't easily be answered in this rather strict format, so I am always looking for more questions.

So, please post your questions! They don't have to be questions that you don't actually know the answers to -- also please consider submitting questions your friends and family ask you, as those are often some of the best. And, if you see a question here that you can answer, please don't hesitate to answer it and save me a little research work!

--Emily

[Guest_PhilCo126_*]

Looking far away in space is looking back in time... But as the Hubble Space Telescope took its deep field, does it show the galaxies at:
1. The distance/time at which the light was emitted?
2. The distance/time at which the object is now (as space expanded all the time and the object might have disappeared meanwhile)

[Del Palmer]

Looking far away in space is looking back in time... But as the Hubble Space Telescope took its deep field, does it show the galaxies at:
1. The distance/time at which the light was emitted?
2. The distance/time at which the object is now (as space expanded all the time and the object might have disappeared meanwhile)

We measure large distances by looking at the object's color, or redshift. The wavelengths are stretched by the expansion of space, as the objects move further apart from each other, getting redder. The light that we see is the light that was emitted at the time the object existed (as light travels at a finite speed, it takes time to communicate information) - most of the deep galaxies in the deep fields no longer exist; they have merged to form larger galaxies. We won't know of their existence until the light reaches us several billion years from now.

Incidentally, I think Emily mentioned that she doesn't do cosmology, but I couldn't resist answering anyway.