Ask An Astronomer Anything At All About Astronomy (II)

This update to my Q&A page is a week later than planned due to a (happily resolved) medical emergency.

Please remember that the purpose of a Q&A is primarily for people who want to learn about a subject. If you've got an agenda to push (i.e. an alternative theory to propose), I'm more than happy to debate it (usually) but you might want to consider that this is not necessarily the best venue for that. Though there's often an overlap, teaching is not the same as debate.

Probably the best solution is to try splitting your question into smaller, more manageable questions which individually don't lead to a conclusion. That will also reduce any bias on my part if I don't like what you're suggesting !

If in any doubt, do ask. I don't want to stifle debate, but I'd like to keep this page primarily as a place for answers. Which are admittedly a rare thing in science...

Also, this page is about astronomy. Occasionally this can overlap with other subjects such as geology and even archaeology. You can ask about them if you like, but, as St Augustine said : "It is a disgraceful and dangerous thing for an infidel to hear a Christian [theologian] talking nonsense on these [scientific] topics." In other words, non-experts should avoid embarrassing themselves by not discussing things they don't understand*. So I reserve the right to only attempt to answer questions which I think I can answer. Occasionally, that will stray beyond the boundaries of astronomy, but I'll try to minimize that as much as possible.

* I'm calling this the St Augustine defence, and it's a helpful reminder that even canonised 4th century Roman theologians didn't think the Bible should be taken literally.

The latest questions added :

1) What is time ?
Annoying.

2) How can we estimate the age of the Universe given that gravity distorts time ?
Carefully.

3) Was there a giant tsunami caused by an impact in the Indian Ocean a few thousand years ago ?
No.

4) When can we expect FTL to become a reality ?
Tomorrow. Last Tuesday (it would allow time travel). Or possibly never.

5) Can a supernova destroy a planet, and if so, how far away would it have to be ?
Anything within its own system is in, like, really serious trouble. Other star systems might be sterilised, but at least their planets won't crack open.

6) Can debris from supernovae destroy planets in other star systems ?
Yes, but it doesn't.

7) Could the asteroid belt have formed by the (recent) destruction of a planet between Mars and Jupiter, with most of its mass being thrown out of the Solar System ?
Nope.

8) Are there more moons of the outer planets than the inner planets because asteroids were flung out of the solar system by the break-up of a planet in the asteroid belt ?
Nope.


If there are any geologists / planetary geologists reading, I'd be grateful if they could check my answers to questions 3 and 8 in case I've said something very silly.