Interesting conversation.....

[Andy_R]

So, my 12 year old son has just posed an interesting question....how can the universe be infinite if it is expanding? Answers on a postcard please, as I want to shut him up about it!

 

[TVC]

The Universe is infinite, however, the space it occupies is expanding. That should shut him up for a bit.

 

[Andy_R]

I tried that approach. He shut up for about 30 seconds then said "If it's expanding it must have an edge. So it's not infinite is it?"

 

[Hill Wimp]

 

[MikeW-71]

I tried that approach. He shut up for about 30 seconds then said "If it's expanding it must have an edge. So it's not infinite is it?"

But if it has an edge, what's on the other side of that edge??

 

[midlife]

Klein Bottle ...... That will fool him

Shaun

 

[PK99]

The simple answer is that if the universe is infinite it does not have an edge, expansion of the universe is expansion of the space within it. IE there is no edge to move further away but things are getting further apart.

 

[TVC]

I tried that approach. He shut up for about 30 seconds then said "If it's expanding it must have an edge. So it's not infinite is it?"

I see his mistake, he's thinking in three dimensions, when our universe is possibly just a bubble of reality in multidimensional space

 

[TheDoctor]

Spacetime itself is expanding. Even thinking about it confuses me, so mostly I don't.

 

[ColinJ]

Wrong, wrong, wrong!

The correct answer to this question is "What do you think I am, a blaaady astronomer?!" ...

 

[ClichéGuevara]

If he thinks that's difficult to understand, wait until he gets into women.

 

[oldfatfool]

Take the infinate number x, logically there must also be -x, negative infinity. This can be represented on number line joined to form a circle with 0 at 12 'o' clock and + and - infinity joined at 6 'o' clock. This 2d circle can represent an axis through the universe. As infinity is always x+1 the circle like the universe is ever expanding.

 

[MontyVeda]

Just stick him in front of Wonders of the Universe... that'll keep him quiet for at least 4 hours, after which, his skull will be filled with even more unanswerable questions

 

[marinyork]

Sign him up for a MOOC on cosmology.

 

[Andy_R]

Take the infinate number x, logically there must also be -x, negative infinity. This can be represented on number line joined to form a circle with 0 at 12 'o' clock and + and - infinity joined at 6 'o' clock. This 2d circle can represent the universe. As infinity is always x+1 the circle like the universe is ever expanding.

So half past three then? I don't get paid enough to do this, that's what his teachers are for