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Comment by wolverine876 | Hacker News Reader

A question about such distant observations: How can our direct observation of something 13.2 billion light years away not be blocked by intermediate objects? Seemingly adding to the problem is that small closer objects can occlude much larger distant ones; just go outside and shade your eyes, for example, or block your view of an entire galaxy with a small pebble.

Is the universe so empty that it's not a problem? Are we just lucky that this object happens to be directly observable? What proportion of the sky is directly observable at 13.2 billion light years?

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This photo provides an overview of how much something vs. nothing is out there:

https://commons.wikimedia.org/wiki/File:Webb%27s_First_Deep_...

Even without a telescope, you can infer that space is mostly empty because the sky is dark at night:

https://en.wikipedia.org/wiki/Olbers%27s_paradox

This is only true because the speed of light is fairly low relative to the size of the universe. If it was infinite, we’d be bathed in light.

Eh only if it were both infinite in size and age. Because it is expanding light is redshifted to radio signals.

An interesting thought, I would expect that redshift would not be a thing if the speed of light was infinite. A lot of other problems too though.

>Are we just lucky that this object happens to be directly observable?

Pretty much, yes.

There is plenty we have trouble viewing (e.g. objects that our own galactic plane obstructs), but the universe is Big. Which, luckily for us, means that even though plenty is hidden from our view, there's a lot that we can still observe.

Intermediate objects can act as gravitational lenses. So we lose some observations, but gain some galactic scale lenses to look through.

https://www.nasa.gov/universe/webb-reveals-colors-of-earende...

You can clearly see images even through a mesh.

You don't need 100% of the light to reach you to have a clear image of something. Even a small portion of the light is enough to get a clear image.

Also, I would suggest just because we can observe things doesn't mean we can observe them from every direction -- there are directions that are more empty and there are directions where we can't see well. For example, large part of our sky is blocked by our own galaxy arms and center and we can't see well much behind it.

And then there are things that we can observe only because we are extremely lucky (usually through gravitational lensing). When we say "we observed the oldest star" we don't mean there were no other stars at the time this one emitted the light.

But yes, in general, our universe is so empty that most of the light after it became translucent will never hit anything.

Thanks. Addressing these issues:

> You can clearly see images even through a mesh.

> You don't need 100% of the light to reach you to have a clear image of something. Even a small portion of the light is enough to get a clear image.

You can see something that's relatively large (in your field of vision) through a mesh. Something that's a tiny point seems like another matter.

Even if you can't see something directly, you could see emitted light indirectly, that reflects off something else. But that doesn't get you a direct image of it, like the ones the astronomy teams publish.

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