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The universe is expanding faster than expected

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Re: The universe is expanding faster than expected

#161

Post by tzs »

dheera wrote: post #147
7373737373 wrote: post #5

Here's a narrated video about this current cosmological crisis: https://www.youtube.com/watch?v=0sfvQ_fsil4 This is one of the key graphics: https://i0.wp.com/particlebites.com/wp-content/uploads/2020/...

The biggest "concern" I have about the expanding universe is that although I have a lot of hope for interstellar travel at some point in the coming few millenia, intergalactic travel poses a whole another set of impossibilities to face, that I'm worried it will never be possible. The space between galaxies is pretty devoid of anything you can use as fuel, repair materials, or anything else. That space is expanding, a…

Energy isn’t really conserved in general relativity. See this Sean Carroll article for more (1). I don’t think this helps with your concerns, though.

(1) https://www.preposterousuniverse.com/blog/2010/02/22/energy-...

Re: The universe is expanding faster than expected

#162

Post by whimsicalism »

casperc wrote: post #40
edgefield0 wrote: post #35

A few years ago, a published article suggested an alternative to the universe expanding is increasing mass. Older objects increase their mass and therefore are red shifted. Why is this alternative plausible theory recieving such little attention? Edit: changed mass decay to increase in mass. I misremembered the theory.

I would love to hear someone talk about this actually as it has been my pet theory for the last 15 years since high school physics. My reasoning was p = mv. m drops (through various processes in a star emitting energi==mass) and since p is constant, v increases. Probably totally naive, but it is just a thought which has stuck around with me.

If the star is emitting massive particles, then it doesn't have constant momentum.

Re: The universe is expanding faster than expected

#163

Post by whimsicalism »

Triv888 wrote: post #121
mountainboy wrote: post #116

Earlier quoted context omitted.

sure! Electric Universe (Thornhill, Birkeland, Scott, et al) Plasma Cosmology (Alfven, Lerner, et al) Infinite Universe Theory (Borchardt) Recycling Universe Cosmology (Mitchell) Subquantum Kinetics (La Violette) Modern Mechanics (Bryant) Push Gravity: (various, book: Pushing Gravity) The Static Universe (Ratcliffe) Steady State Universe (Hoyle, older) That's a good start at least. ;-) All of the above have one or mo…

An infinite Universe makes the most sense, let's adopt that

> An infinite Universe makes the most sense, let's adopt that

Why would human intuition about what makes sense have any impact on physical reality?

Re: The universe is expanding faster than expected

#165

Post by Waterluvian »

nsandell123 wrote: post #152

Is parallax like Doppler Effect in that its based on observer? I wonder what tech stack these astronomers use.

Yep! The definition of parallax is that it's when a position or movement of something differs based on position of observer.

Re: The universe is expanding faster than expected

#166

Post by bouncycastle »

dheera wrote: post #147
7373737373 wrote: post #5

Here's a narrated video about this current cosmological crisis: https://www.youtube.com/watch?v=0sfvQ_fsil4 This is one of the key graphics: https://i0.wp.com/particlebites.com/wp-content/uploads/2020/...

The biggest "concern" I have about the expanding universe is that although I have a lot of hope for interstellar travel at some point in the coming few millenia, intergalactic travel poses a whole another set of impossibilities to face, that I'm worried it will never be possible. The space between galaxies is pretty devoid of anything you can use as fuel, repair materials, or anything else. That space is expanding, a…

However, after the universe finishes expanding, wouldn't it start contracting again?

Btw, Andromeda will collide with the Milky Way in about 4 billion years, so at least we won't need ten times the mass of Mt. Everest to get there...

Re: The universe is expanding faster than expected

#167

Post by User23 »

pdonis wrote: post #124
User23 wrote: post #19

One thing that really frustrates me about cosmology, or at least popular science reporting and books, is a particular kind of lack of intellectual rigor. Specifically, even as a layman, it's clear that observation and model are being conflated. Cosmology is a science in the broadest sense of being a field of human knowledge, but it isn't a science the way that, for example, physics is. It would better be described as…

> It would better be described as a phenomenology Not really, no, because current cosmological models are not derived solely by looking at cosmological phenomena and coming up with phenomenological equations that describe them. (That is not to say that past cosmological models didn't do that; only that our current ones, roughly since the early to mid-20th century, don't.) They are derived by starting from laws of phy…

Thanks for the recommendation, I ordered that text.

Re: The universe is expanding faster than expected

#168

Post by User23 »

lisper wrote: post #159
User23 wrote: post #150

Earlier quoted context omitted.

> That would come as news to most theoretical physicists, who rarely set foot in a laboratory. I agree that it's fair to describe cosmologists as a species of theoretical physicist, given the long standing connection between the observation of heavily bodies and the birth of the modern physical sciences. Still the relation is rather remote. > How do you know we can produce quarks? I personally don't. I'm relying on h…

> Astronomy is a phenomenology OK, again this would come as a surprise to most astronomers. Are you aware that we have sent spacecraft to other planets, and that humans have walked on the moon?

I think you might want to review the site guidelines[1]: "Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith."

[1] https://news.ycombinator.com/newsguidelines.html

Re: The universe is expanding faster than expected

#169

Post by InDemoVeritas »

pratyushc wrote: post #120
garbagetime wrote: post #113

Earlier quoted context omitted.

Could the great filter be something like developing language? That's something that seems quite rare (only one species on Earth has it). If so, then discovering bacteria in the Solar System wouldn't be such a cause for worry.

> Could the great filter be something like developing language? Perhaps it's a combination of factors? Dolphins are social animals that appear to be capable of complex communications among themselves, but don't have hands to manipulate their environment the way we can. Apes have hands, but don't have complex language.

Speak for yourself.

Re: The universe is expanding faster than expected

#170

Post by pdonis »

grishka wrote: post #156
pdonis wrote: post #115

Earlier quoted context omitted.

> It would indeed be incredibly exciting if it would lead to a less silly explanation of the redshift than "universe is expanding". It won't. There is no question about whether the universe is expanding. The issue is over how fast it is expanding; we have two different theoretical models that are giving different answers, and we don't understand (yet) how to reconcile them.

> There is no question about whether the universe is expanding. Why? > we have two different theoretical models that are giving different answers, and we don't understand (yet) how to reconcile them. Maybe... just maybe... that's because it isn't actually expanding, but there's some other, unknown effects at play? It's about time we think outside the box. To me, as a regular programmer kind of person, the very idea t…

> Why?

Because all of the other theoretical models that attempt to explain the observed redshifts fail to match observations.

> Maybe... just maybe... that's because it isn't actually expanding, but there's some other, unknown effects at play?

Nope. Already been tried. Doesn't work.

> It's about time we think outside the box.

Cosmologists have been trying out of the box ideas for decades. All of them failed. That's why we have the models we have now: they're the only ones that survived that process.

> I get it, both make the calculations work out, but they're basically "we have no clue what this actually is, here's our best guess" kind of variable.

For dark matter, you are correct: we don't know what it is, and the term is basically just another way of saying "whatever we need to add to our model to make it match observations works basically like ordinary matter does in the equations".

But that is not true of expansion itself. All of the alternative models that have been proposed to eliminate the need for dark matter still have an expanding universe. The expansion itself is a much more solid conclusion than dark matter is.

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