Is there a law of physics that limits how big something can be?

Question

please view this: http://upload.wikimedia.org/wikipedia/en/3/3b/Sun_and_VY_Canis_Majoris.png

then, consider for a moment if there could be suns bigger than that very far away, and planets slightly smaller, the lifeforms on that planet would be enormous compared to us, is this possible, if so then a speck of dust to us would be what to them? Or would it be virtually impossible for there to be planets that big with life on them?

does this mean then that we are the lowest point where we're the closest to atoms as you can get, or could there be smaller things like string theory but even smaller LIFE that we cant detect, or are we just at that 2nd level of being bigger than atoms and then to some thing else we are the size of atoms,

i agree with the idea that planet size and organism size are not positively correlated but whos to say that other planets far away run by the same rules as the ones weve seen, thats always been a theory that there is life out there that is not based in carbon and perhaps would then run by different rules, if that could be, then do we really know if gravity is a constant everywhere?

even if gravity would prevent something from being so big, perhaps the lifeforms adapt to such gravity by being stronger and that way they can be bigger and conform to their gigantic environment

Answer 1

What we refer to as the universe is very similar to an atom in many respects. There are bodies of solids (neutrons, electrons on a small scale and planets or suns on a large scale) that take up very little of the area available to them. There are spaces between these solids (the sky on a large scale and microscopic voids on the small scale) and the distance separating two of more solids has a dimension several orders of magnitude larger than the dimension of any of the solids.

I imagine we are aware of the next larger level (universe) and the next smaller level (atoms, molecules, neutrinos, etc.). Some day we may know that this continues either downward, upward of both. Our universe could be a very tiny particle that appears as subatomic to some other being. Maybe when we blow ourselves up or consume all of our resources, the earth will die and be the start of some cancer-like disease in the creature that is several orders of magnitude larger than anything we can fathom.

Answer 2

A larger planet would have more gravity, however, the lifeforms on the aforementioned planet could be any size. Planet size and organism size aren't necessarily related.
Consider also the Big Bang theory. There is no limit to the mass of a single object or group of objects aside from the obvious limit of the amount of matter in the Universe.

Answer 3

There is often a limit to how something can be before it collapses into something else due to gravity (if only its own self-gravity). A mountain too big will sink into the crust, and a start too big will collapse into a black hole (after some fireworks).

Life, however, simply refers to an organizational structure with certain properties (most notably, the ability to reproduce). If the lifeform were free floating in space, be of arbitrarily low density, and still remain organized (by electromagntic communication between parts, for example), I can't think of any limits to its possible size. How about a living galaxy?

Answer 4

well if a planet was truly massive, the size of a sun maybe, any lifeforms bone stucture (or whatever they have) would have to be so very strong to resist that kinda of gravitational pressure.

and there is no limit on how LARGE something can be, the universe can continue to expand infinitly, but the most massive thing could contain all the matter in the universe (if u somehow managed to gather it all together.

Answer 5

I believe it is entirely possible for lifeforms to exist that are of such greater size and intelligence, that we are as unaware of them as bacteria are of us. There is no physical limit to how big a "thing" can be, because it depends on how you define a single object. The milky way, for example, is much bigger than VY Canis Majoris, however can be defined as a single object. Even our local galaxy cluster can be considered a single object.
For lifeforms, it depends on your definition of a lifeform. By some definitions, the earth itself is a lifeform.

Answer 6

The maximum size of things is governed by two things:

1. the fine structure constant - which determines how strong matter is
2. the gravitational constant - which governs how strong the force of gravity between matter is.

These two, for instance, determine how high mountains on Earth can be (the max is about twice the height of Everest). They also determine when stars collapse to more exotic forms such as neutron stars.

Answer 7

Yes, there are limits - the kind of planet that has our kind of life starts reaching compression strength of the materials. Big planets tend to be gas planets.
There is no evidence that materials of life allow increased strength in higher gravity - elephants are built differently from mice because they need that much material to support the weight.
And there is no evidence that high gravity planets would result in bigger animals - they might result in squat multilegged worm like beings.

Answer 8

do you think atomic structure has something to do with the limits of size?