This is the one question that most gets my goat. Most people ask it as this is the most 'intelligent' question they can come up with on a topic they are completely ignorant about.
The hardest part about it is the provide an answer that isn't condescending, jargon filled, or smart arse.
I've always struggled with my 'normal' response that "a scope is to collect light, not "see how far" ". This actually means nothing to these good folk.
To throw out "about 2 billion light years" is smart arse-ish too, as many people also struggle with the concept of the distances involved. Especially with the way the media throws around "one billion dollars" or "100 billion dollars", the concept of dollars and distance, 2 billion light years is really just around the corner for most people...
A quick, insightful and respectful reply to a fleeting question is really difficult. And to get too technical, we run the risk of looking too smart for our own good and we've lost any interest from the person we are engaging. Only adding to the difficulty that anything "astro" in the mind of most people is immediately associated with "rocket science" and "too difficult to comprehend", in no kind way due to the way things astro are presented in the general media.
Of course, much of the response has to do with the context the question is posed in. A response at an outreach event would need to be different from a casual meeting with someone, and the Virgo quasar is perfectly fine at an outreach night. And really it is the casual meeting that most causes me trouble.
Please excuse my philosophical musing. I love engaging with people on things astro, and doing so in ways that breaks down the mindset most people have about physics - which is what this is all about.
Hey, on another thing, but related to outreach, there's one thing I've started mentioning to people at outreach nights. I try to bring into the conversation the topic of gold. I ask people if they are wearing any gold, or think about the gold they have at home. All that gold they are wearing was created in the cataclysmic explosion of a supermassive star, that spewed its guts out, and you are now wearing a little bit of that material... Pretty cool I reckon,
Alex.