Everything getting bigger

jharvath

If everything in the universe were getting bigger, would there be any way for us to detect that, or on the contrary, would there be no way to know, no experiment we could perform, which would allow us to confirm an ongoing enlarging of everything?

I have this idea that there is no way to know if this is happening....

DaleSpam

All we can detect are changes to the dimensionless constants. If everything got bigger without changing any of the dimensionless constants then we would not be able to detect it.

jharvath

what about inertial mass - if two objects that were growing in size were touching each other, would it not be the case that they would push upon each other?

Rap

No, because the distance between them would be increasing too.

DennisN

There are many problems with posing such a question.

1. If you and your ruler/measuring rod are "getting bigger" simultaneously, how could you tell anything is getting bigger at all?
   
2. "Getting bigger" in respect to what?

Such problems arise when a question contradicts itself/is a circular reasoning. If anything is getting bigger, it has to get bigger in comparison to something else. Since the Universe encompasses everything, this else has to be part of the Universe. So this else would also get bigger. From a physics perspective, the question makes no sense. It is more metaphysical, i.e. part of philosophy. Now, the Universe is expanding of course, and this can be measured.

jharvath

So, it seems as though, if it were the case that the everything in the universe were getting bigger there would be no way we detect that using current level of physical knowledge.

mfb

You cannot even define what "bigger" means. This is not a question of physical knowledge.

someGorilla

There are many ways to "get bigger".

If "everything gets bigger" means that everthing, while getting bigger, keeps working exactly the same way, every gear keeps turning, every tree keeps growing the same way, and so on, then no, of course you can't detect it, since everything is the same as before. You build a scenario where everything is the same and then ask if we can find something different ? The question itself is meaningless. Notice that when you imagine everything getting bigger, you have to keep something constant, for example you "see" objects getting larger with respect to your field of vision.

On the other hand, there are many ways in which everything could get bigger in a detectable way, but I think they don't correspond to what you meant. For example, an ant can lift many times its weight, because the section of its muscles is big in respect to its mass; if everything got bigger, you could see ants (and yourself) getting weaker. But this assumes that lots of things, like atom sizes, don't grow. Or, light could take more time to go through an object if it's bigger - and this actually happens, though only on a very big scale.