If i held up my hand to the sky how many galaxies are blocked by one fingernail.
Is the number of galaxies blocked just on one plane or are there galaxies blocked behind other blocked galaxies in the plane that is right behind the finger nail part. In other words does it go to infinity behind that blocked part.
If the answer is yes, it is infinite behind that blocked fingernail patch, then my question does not have an answer? In a finite numerical way.
It’s definitely not an infinite number, because light from very distant galaxies can never reach us in order to be blocked in the first place. They are so far away, and the distance between us is growing so quickly, that even light cannot reach us - it will be farther away with every passing moment even if heading straight at us.
A thumbnail is about 1.5 degrees in width at arm’s length. A thumbnail takes up probably about one-hundred-thousandth of the sphere around your eye at arm’s length. There are at least 2 trillion galaxies in the observable universe, so there are about 20 million galaxies covered up by your thumbnail at arm’s length from the point of view of your eye.
Are you saying the distant galaxies are receding from us at greater than the speed of light?
I thought only massless objects could travel that fast…
Yes. The further away an object in some other part of the universe is, the faster it is moving away from us. Not because the object is moving, but because the space in between us and it is expanding.
Just because the light will never reach us doesn’t mean there aren’t galaxies back there. It’s entirely possible there could be an infinite number of galaxies blocked by your fingernail, though we’ll likely never know for sure.
This is why we need to limit the question to the observable universe (the part of the universe for which light has traveled less than 13,787,000,000 (plus or minus 20,000,000) miles to reach us). If we expand the question to any non-observable part of the universe, there’s no way to answer it. We have no idea how big the non-observable part of the universe is.
This is an average of course. The galaxies in the observable universe are not all all evenly spread out, so it could be a lot less or a lot more.
Here’s the obligatory link to one of the Hubble (Ultra) Deep Field images. Rather than your fingernail, this image spans about the size of a pencil dot marked on your fingernail, about 0.1 mm x 0.1 mm at 1 meter.
But it shouldn’t be that much more or less. Galaxies are found in dense clusters and filaments, with voids in between, so in the relative near universe, there will be a lot of variation in the numbers. But going out all the way to the edge, these will average out and the numbers will be about the same.
To be clear, in Pasta’s link, three of those dots (the ones with crosshairs on them) are faint stars in our own Galaxy that just happened to photobomb that image (they tried to get as few as possible in the frame, but it’s tough to entirely avoid all stars). Everything but those three is an entire galaxy.
I see 4 stars with diffraction spikes (the crosshairs) on them. One near the top about halfway to the right edge, one just right of center, one below center near what looks like merging galaxies, and the fourth at the very bottom center.
And just to note, even the very faintest dots that you can barely make out are mostly galaxies[sup]1[/sup]. And there’s likely some galaxies that are too small and faint to show up in that part of space.
[sup]1[/sup] A few could be extremely faint red dwarf stars in our own galaxy. Those would not show diffraction spikes.
The fabric of space itself is what’s expanding.
Ah, yes, I missed the bluish one right at the bottom. Still, the vast majority are galaxies.
13.7 billion light years, not miles. And don’t forget that the most distant galaxies that we can see are now about 45 billion light years away, but were much closer when they emitted the light. Expanding space is weird
This whole Universe thing is getting far too crazy. Billions of light years away and trillions of galaxies. That photo of a pin head sized area from Hubble deep space images is mind boggling.
And 1 light year is 6 trillion miles. So a billion light years…why do we even bother
I think mankind should just give up trying to understand this shit. We will forever be earthbound and maybe that is what the universe is trying to tell us. The space is too vast to venture out. Stay on your planet and enjoy it.
But that’s the beauty of it: We can understand it.
My apologies. That was a stupid mistake on my part. Yes, it should have said “(13,787,000,000 (± 20,000,000)) * (6,000,000,000,000) miles”.
Not a pinhead. A grain of sand held at arm’s length.
Or about 1/10 the apparent diameter of the Moon. (So 1/100 the area of the Moon.)
