Sunday, May 9

Readers respond: the universe is expanding, but what is it expanding into? | Astronomy


Scientists and astronomers tell us that the universe is expanding. But what is it expanding into, that is, what lies beyond? the universe?
Phil Town, Lisbon

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Readers’ response

What is beyond the universe? Simple! All those objects that you have lost somewhere and have never seen since. Pens, glasses, wallets, keys, telephones, knives, combs, diaries, umbrellas, tissues … whatever!

Don’t people realize that all the space around them is riddled with tiny wormholes, into which these objects sink, never to be seen by mortal eyes again? Firmly Dirac

The universe is a clown balloon that is still in the inflated stage and is about to take the shape of a dachshund. Jamessss

As a teacher, this is a question that comes up often in my physics lessons. Part of the problem is one of perspective. The human brain works best when you think about things in the fewest dimensions possible. We reduce the curved and bulging surface of the Earth to two-dimensional maps, or two-dimensional streets to one-dimensional systems, such as street numbers or mile markers.

Our minds are not able to intuitively conceive what the universe really is like. We see a balloon expand and we see it expand in the air around it, and we assume that the universe does the same. This is incorrect. The universe does not expand into anything because, as far as whatever evidence we have, it is all that exists. In other words, there is nothing outside the universe.

We often think that the Big Bang happened in space at the center of the universe, but this is only partially true. What really happened is that the Big Bang it is the universe. It was not an explosion in space; space is the explosion. The space between objects has been expanding ever since. The fact that this is unfathomable should make it even more surprising. Andrew Busch

Instead of thinking that the universe inflates like a balloon, I see it as a giant ball of dough that various chefs stretch in all directions. So there is always mass at the original starting point. And with that, I’m hungry. Eva_Brick

The question begins with an incorrect assumption: that the universe has as its “border” a boundary between “universe” and “non-universe”.

All we know, and this is what we mean by the expansion of the universe, is that, on average, each galaxy is moving further and further away from all other galaxies, at an increasing rate, without a central point. This does not mean that, at any local level, spacetime is “stretching” like a sheet of rubber (a common misunderstanding), nor does it mean that at local scales stars and galaxies cannot yet fly with each other.

The problem with your question is that you are imagining something from your experience, say an inflated balloon, and you ask what seems reasonable: “What’s outside the balloon?” from the point of view of being outside the globe and being able to see that it is a globe.

Instead, imagine this: you are a cat, inside a flat. You have never been outside. So, as far as you know, there is nothing off the floor. Now imagine that you are shrinking. From your feline perspective, you stay the same size, but all the walls and furniture seem further away from you – your universe is expanding. But I wouldn’t ask, “Where is it expanding to?” because as far as you know, and you can always tell, the floor is all there is, it’s just spreading (presumably, that’s what floors do, because the only one who can observe does it). That is the position we are in and why the question does not make sense. HaveYouFedTheFish

The universe is everything (as far as we know), so it makes no sense to say “what is it expanding into”. It just is everything. The Big Bang happened “everywhere” at the same time. Is it infinite or finite? We do not know. Even if it is finite, it may not have an “advantage.” There are many unanswered or even unanswered questions right now. We may never know, because all of our measurements are limited to the observable universe. csjjl1

Just because we don’t understand something doesn’t mean it must be the work of some kind of supernatural entity. That’s absurd. There are limits to what the human brain can understand: it is limited by its evolutionary context. It is simply not acceptable to explain the things we cannot understand by invoking a cloud-dwelling divinity. Well, it might be acceptable to some people, but not to me. Oh, and the universe is expanding on itself. FirebirdV

My theory is that the universe has to expand to contain Brian Cox’s sense of self-satisfaction. DonerCard

According to Men in Black, we are in a large marble thrown by aliens. However, it does not explain how the marble is expanding. Go away

Has anyone noticed that this thread is expanding? What I want to know is: what is it expanding into? Plovdiv12

We call the point of origin of our universe the Big Bang event. This is the point, from our frame of reference, where a new time and space began to unfold the universe. It lies about 90 billion light-years * in all directions within our 13.8 billion-year-old universe. This counterintuitive observation is due to the fact that new times and spaces are continually being created within the singularity ** everywhere at once. The point of origin of the universe has moved beyond our observable horizon; note that all other points in the universe share a similar observed frame of reference ***.

Note that while there is no “outside” in our universe of singularities, there is no reason why there cannot be an infinite number of singularities, each with its own inner evolving universe of space-time.

Mainstream cosmology is of the opinion that new time and space will continue to develop within the singularity forever; the universe will gradually turn cold and dark as the static mass becomes increasingly diffuse and the energy undergoes continuous entropy (the “big tear” theory).

* The edge of the “observable” universe is about 46.6 billion light years in all directions; the distance to the Big Bang event, which is a much more speculative distance, is probably about 90 billion light years in all directions.

** Most cosmologists believe that the universe did not start out as a “mathematical singularity,” but as something best described as very small and dense. Stephen Hawking showed that we cannot learn anything about the origin of the universe until it has aged at least 10⁻³² seconds, because no information has yet been created.

*** Each point within the universe shares the same frame of reference of observing itself as the oldest, most central, and most distant point of the Big Bang event, compared to any other point within the entire singularity. Although our universe is continually evolving in a new time and space, it still maintains the characteristics of the uniqueness of our origin. Chris ducey

I think Professor Harvey Keitel said it best in Mean Streets, considering the meaning of an eternal spiritual life, the universe and everything: “Don’t fuck with infinity.” Dylan37

Saying that “the universe is expanding” because what we can see and observe from our part of it that seems to be moving away from a certain point sounds like arrogance to me. hemodroid

It is not about “getting away from a certain point”, but rather all the points are expanding away from all other points. So it is not arrogance at all; our place in the universe is as little special and nothing extraordinary as all other places. Readout_Noise

I think it helps to realize the inseparable relationship between things and the physical dimensions of space and time. Any measure of space involves looking at the distances between things and any measure of time involves looking at the movement of things relative to each other. If you had a completely empty space, you couldn’t measure space or time. So in that sense, a region of the universe that has nothing in it doesn’t even really exist before something moves into it. Short Term Cook

Einstein once said that people used to think that if you took everything out of the universe, you were left with space and time. Relativity says that space and time would come out with things. Sidney lotterby

42. PunkyRooster (and Parcival)

Hey, you beat me! That’s not fair! Nelliev

In a joke that a quantum physicist could explain, I said 42 before you. And later and at the same time, but in a different place. Something like … Florton66


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