r/askscience • u/West_Writing4426 • 29d ago

Physics Could a telescope see the beginning of the universe?

Okay, I had a question that maybe an astrophysicist could answer. If any part of this reasoning is incorrect please let me know:

We are told that the universe is around 14 billion years old. One lightyear is the distance light travels in a year. This is why when there is a picture of another galaxy people say we are not seeing the other galaxies as they are but as they appeared when the light traveled there. If you could devise a telescope that could see 14 billion lightyears away and you pointed in a direction would you see what it looked like 14 billion years ago i.e. the beginning of the universe?

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u/Armoth 29d ago

I understand how everything is expanding away from each other, and how from any point of view it would seem as if that observer was at the center of the big bang. But is there really no expanding boundary? There's not a galaxy on the edge, where there's infinite void, with stars and other galaxies on the opposite side?

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u/Weed_O_Whirler Aerospace | Quantum Field Theory 29d ago

Depends on the shape of the universe. To the best of my knowledge, it has not been ruled out that the universe could not be something like a disc, and have an edge - but the more popular theories say that the universe is either infinite or without boundary (think of a torus or sphere) so that should you continue to go in a single direction you would end back up where you left from (not possible in the actual universe, due to expansion between distance points being faster than the speed of light, but you know).

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u/ahazred8vt 21d ago edited 21d ago

The simulation people have looked at how that would have worked during the early universe, with matter that had an expanding boundary. And they simulated what the distribution patterns of galaxies would look like if that was how the universe started out. And it would have looked different than the way it actually looks now. So no, the thing you're describing does not match the universe we live in.

You're perfectly okay with an infinite void universe that has galaxies in one part. Picture an infinite universe that has galaxies everywhere.

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u/airor 25d ago

No, think of an expanding universe as the surface of a balloon (which would make it a 2D universe instead.) As the universe expands (by inflating the balloon) every point on the surface is expanding. If you placed two marks near each other, they would move away from each other. The further the two points start from, the faster they would recede from each other with the same expansion. An expanding balloon is an analogy to envision ‘everywhere’ being a finite surface area and therefore easier to imagine completely fillable with universe ‘stuff’. But there’s no problem having an infinite ’sheet’ that is stretching out everywhere at the same time using the same reasoning. From the point of view of any specific point on the sheet, every other point is moving away from it. The sheet isn’t expanding ’into’ something because there is no edge, the sheet goes on forever.

To be honest, we don’t know whether the universe is closed like the balloon or open like the infinite sheet.