# How do you compare in size to the smallest and largest things in of universe?

Asked by RealEyesRealizeRealLies (30938) May 23rd, 2015

Vsauce makes an interesting claim at the end of this video. Can anyone verify?

So, the smallest thing in the universe is a plank length.

And the largest thing of the universe, is well… The Universe.

As Vsauce claims, the number of plank lengths it would take to stretch across one human brain cell, is the same number of brain cells it would take to stretch across the entire universe.

Is there any real relationship there, enough to claim that human beings are sized precisely in the middle of all known physical phenomenon? Anyone here to check the math on that?

Observing members: 0 Composing members: 0

Well, we’re not ”...sized precisely in the middle of all known physical phenomenon.”

If one considers a Planck length as equal to zero, and The Universe as finite at any given moment, then precisely in the middle would be ½ the the distance across the universe.

Also, the Universe is continually expanding, but the size of a brain cell is fairly constant, which means that the ratio of Planck Length:breadth of a brain cell may have been equal to brain cell:breadth of Universe at some point, but no longer.

But that is a great video to explain the concept of Orders of Magnitude.

zenvelo (35469)

I think you compare with a Planck length of tongue in cheek. Time isn’t the only thing in the Universe that is relative to the observer.

Blondesjon (33974)

@zenvelo

Why should I consider a Planck length as equal to zero?

I don’t think we understood the video in the same way. I think the claim was about size in relationship to other physical sizes. I read your answer to be about position, not size. Am I misreading you?

@Blondesjon

Real funny pal. Real funny.

Also @zenvelo, yes, the universe is expanding… but I’ve always wondered if that means that we’re also expanding… like, the cells in my body… are they expanding in relationship to the other objects? Is not not all relative?

I don’t know.

Just the same in importance and uniqueness as all of those other things.

marinelife (62445)

I suggest everyone who likes this subject have a look at this and prepare to spend some time. (also, Plank length is theorised, not something actually measured. geez. actually, anything smaller than 1×10 to the negative 16th is nothing but theory.)

http://htwins.net/scale2/

My kid thought this was incredible and it has helped his understanding of the natural world.

I detest ‘human-centric’ views of science and the real world. It simply isn’t so. What IS so is that humans are dumb and ego centrist, so have difficulty relating to the actual scope of scale and time on a more realistic level.

cazzie (24516)

The human brain is the most complex physical structure in the known universe. I’ve heard it said that an average human is halfway in mass between an atom and the critical mass of a star.

But these facts aren’t all that relevant to anything, except helping people feel important. There is no good reason to suppose that maximal complexity or maximal intelligence would reside in the middle.

@RealEyesRealizeRealLies No, we’re not expanding to match the universe. The electromagnetic force, which is the most tangible force in our lived experiences, is too strong to be affected by the expansion of the universe. Even the Milky Way is likely to be unaffected by the expansion of the universe, as it has enough gravity to hold itself together. The real downer about expansion is that one day all evidence of celestial objects outside our immediate surroundings will be extinguished. Light from distant galaxies simply won’t travel fast enough to ever reach us, because the gap between us and them will expand faster than light can traverse it. We will go from knowing about the beautiful universe we know and love to believing we are an island in the blackness. Thankfully this point is several billion years away though.