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I read an article about a huge bubble being discovered in which the solar system sits bang in the middle. It got me thinking about the curvature of spacetime. The bubble was created by several supernovas millions of years ago and is still expanding today. If we sit in the center of said bubble, is it possible we are viewing the rest of the universe through a "warped prism of spacetime"? The death of stars can form black holes, which are the main culprits of warping and several supernovae could be significant!
https://www.sciencedaily.com/releases/2022/01/220112121510.htm

Paul Hadfield
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As a general rule of thumb - the importance of spacetime curvature can be assessed using the ratio $GM/Rc^2$, where $M$ is a mass and $R$ is a radius. If this ratio is $\ll 1$ then the curvature isn't especially important, other than if making very, very precise measurements - see below.

Some values for $GM/Rc^2$ are useful then:

At the surface of the Earth - $\sim 10^{-9}$.

At the orbital radius of the Earth due to the Sun - $\sim 10^{-8}$

At the edge of the solar system - $\sim 10^{-10}$.

At the edge of a 100pc bubble containing the typical density of stellar material in the local disk (about 0.1 solar masses per cubic parsec) - $\sim 10^{-10}$.

You can see that all of these ratios are extremely small and therefore the effects of spacetime curvature are rather subtle and difficult to see. Having said that, the largest of these ratios is for the Earth's position in the solar system and indeed the effects of spacetime curvature - as manifested in tiny shifts in the apparent positions of stars (at the microarcsecond level) - is currently being probed by ESA's Gaia astrometry satellite (e.g., Crosta & Vecchiato 2010).

Note that black holes do not warp spacetime any more than anything else of the same mass. The differences between the spacetimes near black holes and normal stars only becomes apparent when you get closer to the black hole than where the surface of the star would be - since $M$ remains constant, but $R$ can become very small.

ProfRob
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It is certainly true that the Solar System may have formed in a region where several supernovae seeded the interstellar space with material that later collapsed to form the Solar System, and probably other stars as well. The research suggesting this was published in Nature as A Solar System formation analogue in the Ophiuchus star-forming complex by John C. Forbes, João Alves & Douglas N. C. Lin. There is a more accessible article on the Space.com website here.

But there is nothing special about this. Most planetary systems with Earth like probably formed in a similar way as the elements needed to form rocky planets are produced in supernovae. While we use the term bubble to describe the region of space modified by the supernovae you not take this to mean space is fundamentally different in any way. It's just that the composition of the interstellar dust in this region has been modified.

Having said this, it is also true that we live in a region of spacetime that has been curved by the mass of the Sun, and also the mass of the Milky Way galaxy in which the Solar System is embedded. So in principle when we look out at the rest of the universe the view we see is affected by this curvature. In practice however this spacetime curvature has no effect on our observations. As a general rule the effects of curvature on light are only significant in extreme cases such as near to black holes.

John Rennie
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  • thank you, John, is it wrong to presume that time is any different in these so-called bubbles? If the sun's mass, for example, warps the space around it does it also warp time? Admittedly, on a tiny scale. I guess my bigger question is ..can time be different in multiple regions of the universe? brgs Paul – Paul Hadfield Apr 13 '22 at 15:03
  • @PaulHadfield yes time is different in different parts of the universe but not by very much (unless you're very near a black hole). For the details see my answer to Is the cosmological time grosso modo isochrone? (Don't be put off by the weird title, it basically just means "is time the same everywhere".) – John Rennie Apr 13 '22 at 15:13
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I'm not an expert but your question has been on my mind for a long time. It seems that we are indeed viewing the cosmos from within a few bubbles which are likely to distort our perceptions.

We are looking out from the inside of a gravity well and surrounded by the heliosphere which consists of at least two shock waves and a bunch of interstellar media whilst hurtling round within another gravity well of far greater magnitude. We're also operating on the presupposition of the cosmological principal, which seems a bit tenuous.

Perhaps it would be a prudent expenditure to deploy a few telemetry arrays beyond the heliosphere to find out if things look the same from out there as they do from in here.

Stuart B
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