Universe Doubles in Size

Suppose that, at midnight on New Year's Eve this year the linear size of the universe and everything in it were to double 'simultaneously'. Is there any possible experiment that could detect the doubling. Or to put it another way, is it possible to measure the absolute or external* size of the universe?

* By this I mean the size as it would appear to someone external to the

If the change extended to the quantum scale (such that e.g. Planck's length also doubled), then no. If it did not, then certainly; the speed of light would appear to be halved, for one thing.

How is a metre defined these days?

I forget who said this, but the answer is yes because the hams hanging in the butcher's shop would fall to the floor. The weight of the ham is proportional to its radius cubed while the strength of the string is proportional to its thickness squared.

(I do not like 'external to the universe'.

Eamon Warnock (or somebody else of the same name) wrote thusly in message

I would say no. We are within the universe and all our measuring instruments would be affected by this event, not only of length but also of time and mass. The result would be that what was one metre long 'before' is now still one metre long 'after' according to our 'after' measuring standards.

The notion of being external to the universe is possibly a contradiction in terms, or more likely the sole prerogative of God.

1/299,792,458 the distance light travels in one second

This is a thought experiment about linear size doubling, not about the mass of particles increasing 8 times.

Neither does Einstein. It is believed there is nothing 'external to the universe'. I think it is impossible to measure the 'absolute size' of the universe for the 'simple' reason that it doesn't exist - the absolute size, not the universe

My knowledge of cosmology and general relativity is very limited but loosely speaking, I think space and time in our universe (the only one?) is 'created' by what is in it. Meters and light years are concepts 'internal' to the universe and it makes no sense to say _everything_ changes size (if certain things like constants of nature are supposed to change with it). As a thought experiment, relative sizes could change, but relative sizes is all there is.

Also, we were asked to suppose everything changed simultaneously, but there is no absolute time and thus no universal 'midnight on New Year's Eve'.

This would probably be more suited to sci.physics. Physicists do like thought experiments but I'm not cross posting because they would just point about my likely misconceptions

In our current understanding of spacetime, there is no such thing as 'external to the universe.'

That's why he said 'would.'