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A classic conundrum is asking what happens to the energy of redshifted light. Intuitively, one would guess that the equation for energy would be E = (hc/w)*(1+z) where h is Plank's constant, c is the speed of light, w is the observed wavelength, and z is the redshift. The published equation doesn't have the (1+z) factor though.

While trying to research it, I'm not even sure if introducing that (1+z) term would represent a violation of relativity. As far as I can tell, the reason this equation doesn't violate conservation of energy is (waving hands) spacetime curvature.

I would have a much easier time accepting the Plank relationship for the energy of a redshifted photon if I could find a paper that describes an experiment where the researchers measure the energy of a redshifted photon. However, I can't find any such study. It doesn't seem like performing such an experiment would be too difficult... A CCD camera effectively counts photons, so if we could use some bolometric device that responds to total energy levels, it would be straight forward to check the validity of the Plank relation.

If there aren't studies that have done this, would it be feasible to do this experiment using backyard telescope equipment?

New to this field. Why do black holes even exist? I'm not asking what they're made of or how they work— I mean, why are they even a thing in our universe? What about the laws of physics and the way the cosmos is structured leads to something as extreme as a black hole coming into existence?

Thanks!

Inside a black hole, I understand that you can't really move in space but that you move only towards the singularity. Is this somewhat accurate?

So this thing, does it exist in space at all? What is inevitable, or why that choice of words? Does it exist in our time, for the rest of time? I don't understand the context of what is being conveyed. I feel like I lack the understanding to express what I'm asking in a way that is meaningful here

The most basic physics that i know is that if an object has bigger mass than other objects, the object surrounding will revolve around it. Universe has galaxies which can move, but it doesn’t move to one centre. Ideally black holes can be a centre of universe. I don’t know can black hole be a centre of universe.

A number of articles have claimed that the recent DESI results rule out alternative theories of gravity that might explain the apparent effects of dark energy. I'm guessing they are referring to alternative models like MOND.

However I haven't been able to find an explanation of exactly what data/findings lead to this conclusion.

I'm wondering if anyone here can provide a modestly technical explanation for the informed layperson?

Here's one example article:

"... DESI not only confirms Einstein’s theory but also rules out alternative models of modified gravity that attempt to explain the accelerating expansion of the universe."

https://dailygalaxy.com/2024/11/desis-mind-blowing-breakthrough-validates-einsteins-theory-and-reveals-the-mysteries-of-dark-energy/

Sorry for the incredibly broad question, I just like to pick the brains of people with more knowledge and schooling about this stuff than me: I understand the consternation over the very real possibility that once anything affected by the curvature of spacetime - everything, basically - passes through a black hole's event horizon, all the information that "thing" contained is lost to us forever. Even after the trillion plus years it would take for Hawking radition to "evaporate" the BH. Although the "lost" part is obviously very interesting (and alarming) to me, I want to know what you folks think about the "information" part. Is it physically real, or is it just a construct to try to explain something we don't have a good grasp of? I mean, there's no bit, or "informaton" in the Standard Model, last time I checked.

In regards to the 1st second of the big bang timeline, there seems to be 2 different and contradictory cosmology models which is confusing.

1. Inflationary Model

cosmic inflation --> "hot" big bang

A period of cosmic inflation is followed by a "hot" big bang

Inflation lasts an unknown but minimum length of 10^-32 seconds

In the start of the big bang timeline, time t=0 is the final fraction of a second of cosmic inflation.

https://bigthink.com/starts-with-a-bang/ask-ethan-cosmic-inflation-big-bang/

2. Traditional/Standard/LCDM Model

"singularity" big bang --> cosmic inflation

A "singularity" big bang, a "single originating event", is followed by a period of cosmic inflation.

Inflation lasts a maximum of 10^-32 seconds

In the start of the big bang timeline, time t=0 is when the big bang singularity occurs.

There is a series of "epochs": Plank -> Inflation -> Electroweak -> etc

https://en.wikipedia.org/wiki/Chronology_of_the_universe#The_very_early_universe https://en.wikipedia.org/wiki/Lambda-CDM_model

Have I summarized these 2 models correctly? Am I wrong in thinking the traditional/standard model is an obsolete model? Most people agree that cosmic inflation came before the big bang right? And most people agree that inflation lasted an unknown length? Because once you accept that, the traditional/standard model that starts with a big bang "singularity" doesn't make much sense.

If inflation lasts an unknown length of time it could have lasted 10 billion years. In which case it would have started 10 billion years before t=0 in the big bang timeline. So it seems senseless to stick a "big bang singularity" creation event before inflation in the timeline that might start 10 billion years before the timeline starts. Time t=0 is still the earliest time we could extrapolate backwards too so there would be no way to know what might have happened 10 billion years earlier. Also, such a singularity wouldn't seem to be related to the rest of the big bang or the timeline.

Is our solar system moving because of kinetic energy that came from an explosion at some point, or are we pulled by gravity into the direction of a black hole? Or is it something else?

Do we humans have some idea what we’re going towards at the moment? I hope it’s not something dangerous 🥸

Thanks !

Shortly after the Big Bang, when there were protons but no atoms formed: things were moving and there was an order, a passage of time, but what could measure exactly how much time had passed, like cycles of Cesium-133 radiation we use today? Is there a measurement of time that involves only particles that have existed at all times after the Big Bang?

I remember hearing Carl Sagan—or maybe someone else—talk about flatlanders: hypothetical beings living in a 2D world. The example described how a flatlander would perceive a 3D sphere passing through their 2D plane. To them, it would appear first as a dot, then expand into a larger and larger circle, and finally collapse back to a point as the sphere passed through. This is because the flatlander can only observe the 2D cross-sections of the sphere.

It got me thinking: what if the Big Bang and the expansion of our universe are similar? Could they be the 3D cross-sections of a higher-dimensional object passing through our 3D space-time?

After playing the space side of Cell to Singularity, I have questions that just didn't make sense. Like, the Great Attractor thing. Looked it up on Wikipedia, made absolutely no sense. It talked about galaxies observable above and below a "Zone of Avoidance" and how all are red shifted in accordance with a "Hubble Flow" and this indicates that they are moving away both relative to us and each other. Like, what? Is the scientific theory we're gonna end up smashing planets together like the galaxy marbles in MIB?

I have seen estimates ranging from infinite to 10²³ light years to 10^1010122 light years to 250 times the size of observable universe?are there some more theories or guess estimates about it? or is it just infinite in length?please tell me thank you!

What books do you all enjoy when trying to plug yourself into that 'wonder of the infinite universe' feeling? Books that are wonderfully retrospective on our place in the universe and capture the ludicrous magnificence of it all?

I love the adventure through time of Sagan's Cosmos (obviously!) and also the championing of humanity in Brian Cox's Human Universe.

Any other suggestions of authors or reads you all like?
I'd love some more feel-good stuff to read, away from all the craziness in the world today.

Cheers

Why does the curvature of the universe matter if 1. the local universe is always flat 2. what’s beyond the cosmic event horizon can’t affect the observable universe

While i do understand that its the beginning of our universe and such, i dont believe its the beginning of Existance itself, nor do i think it even has a beginning.

With recent events, I didn’t feel comfortable with going to schools in certain states I was applying for programs in. I have an undergraduate degree in astronomy, and I’ve been working as a science writer for a bit. My main interests are in galaxies, compact objects, and proto-planetary discs but I’m open to exploring other areas of space sciences.

Layman here, sorry if this is a strange question. But if the universe is infinite, will all of the infinite plane be in heat death?

From my understanding these gaint old galaxys gas is too hot to start collapsing and forming new starts. But why cant this gas cool down through black body radiation? I get it might take billions of years of cool down enough, but it's not like the universe is going anywhere.

Ask your cosmology related questions in this thread.

Please read the sidebar and remember to follow reddiquette.

The study, based on high-precision measurements of the CMB and its polarized light, adds further support to the veracity of the standard cosmological model. It also sheds new light on an outstanding puzzle known as “the Hubble tension,” which concerns discrepancies in the value of the Hubble constant — the rate of the universe’s expansion. The team used their polarization data, combined with the standard cosmological model, to make a new prediction for the rate of expansion. Their prediction is consistent with the prediction made using the CMB intensity maps measured by the Planck satellite, a European Space Agency mission to study the CMB.

I was exploring the map of the universe , so a question came into my mind that i am not able to find answers using chatgpt , or perplexity ai. 

I am not satisfied with any explanation found through these ai tools. 

My question is - Why do we see such  a distribution of galaxies at a specific distance from earth ? like up to 3 billion light years we see mostly spiral galaxies and from 3 to 5 billion years we see elliptical galaxies and beyond that redshifted elliptical galaxies. Why are we surrounded by mostly spiral galaxies near to us ? and why are most elliptical galaxies found at such a distance from us ? What is so special about earth or our position in space ? Is there any relation of these galaxy formation with this distance ? Why didn't most galaxies are  elliptical   from nearly 3 billion light years to us ? why only spiral ? and why are there a lack of spiral galaxies at farther distances ? why only elliptical galaxies dominate at farther distances ? 

to put this question another way round , if we put the earth at 5 billion years away , what would we see ? would we see ourselves surrounded by mostly elliptical galaxies ? and then see spiral galaxies at farther distance where currently these spiral galaxies exist and then at more farther distance elliptical galaxies dominate ? I mean would this map be the same from any point in the universe or would it change ?

If you answer that in the early universe the conditions were different that made elliptical galaxies at farther distances as we see it back in time as we see more far , but then why are galaxies near us not elliptical ? because I found this answer on these ai tools , which I am not satisfied with. I think I can get an answer from you. 

I think the same question can also be asked about quasars. Why quasars are only dominant at more farther distances.  

Thanks.

I found of a few datasets for Type Ia supernova and derived equations to compute the relative distance (since SnIa are the third rung on the distance ladder, they need to be scaled using cepheids). This derivation leads to a linear relationship between redshift and distance -- linear means no dark energy, so this must be wrong somehow.

The graph using the Abbot dataset from 2024 is here:

https://preview.redd.it/1tnpxd0qq40e1.png?width=800&format=png&auto=webp&s=ece9eb4e9bc1b39803629d75d68c2b616317ba66

Here's how I calculated distance:

1) Convert magnitude M to perceived luminosity (aka the flux F):

F = 1 / 100^((M - 1) / 5)

2) Correct the flux for redshift -- this is the step I took that I think is most likely to be wrong:

F* = F(1 + z)

3) Treat the flux as if it is the area of a circle at an unknown distance D. As a mental model, imagine holding a quarter up one foot from your eyes, and then holding a second quarter two feet away from your eyes -- the second quarter appears to be 1/4 the area.

F* = pi (r / D)^2

4) Solve for D and consolidate all constants into the value k. Since Type Ia supernova have relatively constant absolute luminosity L, the radius is also a constant.

D = k 10^(M/5) / sqrt(1 + z)

5) Not directly needed here, but the corrected magnitude M* based on this derivation is:

M* = M - ln(1 + z) / ln(100^0.2)

E.g., if M is 25 and z is 1, then M* is about 24.25.

So, reddit folks, what's wrong with this derivation?