Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Webb and Hubble confirm Universe's expansion rate

esa.int

Post reply on HN
Print view View original

141–150 of 380 posts

Re: Webb and Hubble confirm Universe's expansion rate

#141

Post by theoreticalmal »

throwawaymaths wrote: post #85
tzs wrote: post #28

A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant). • From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should…

There's a 'fringe' theory that the CMB is not the echo of the big bang but rather the redshifted black body radiation of intergalactic dust (apparently the numbers are about right). Although the primary proponent of this theory is trying to justify some sort of cyclic universe model with it, if my understanding is correct it would still be compatible with a 'standard' big bang that has the "longer" (aka galactic expa…

I can’t believe it. First they take Pluto from us, next they’re going to tell me the static on my tv set isn’t the remnants of the Big Bang, but just hot dust? My childhood is crumbling!

Re: Webb and Hubble confirm Universe's expansion rate

#142

Post by kaashif »

CuriouslyC wrote: post #88
pishpash wrote: post #60

Earlier quoted context omitted.

Almost every model we build of more trivial things based on observation always turns out to be not really right. I cannot imagine why one of the universe that has had multiple version updates in the last 100 years to not also be grossly mistaken. I also don't expect the full model to be simple or beautiful. We may be thinking wishfully based on massive extrapolation and cutting corners to suit our narrow view into th…

I think the truth is likely that we live in a very complex universe that can be approximated by these sweeping laws in general, but is very "messy" close up. Consider that while the universe roughly obeys probabilities, it also has will and intent (to a degree we can debate in another conversation).

What do you mean by will and intent?

I guess if humans have will and are part of the universe, then the universe has it too, but I don't think that's what you meant.

Re: Webb and Hubble confirm Universe's expansion rate

#143

Post by alexb23 »

pdonis wrote: post #113
arcastroe wrote: post #94

Earlier quoted context omitted.

> In your explanation, I think we'd expect to see some very distant, very slow-moving galaxies moving toward us Thank you, but I suppose I'm not really questioning the big bang piece. My question was mostly in regards to the continued acceleration piece. Feel free to disregard the "in random directions" part of my original post. I'm picturing more of an explosion in empty space. A firework or granade of sorts. Any in…

> I'm picturing more of an explosion in empty space. No, that's not what the big bang is. > this would imply a "center" to the explosion, which I've also heard is not the case That's correct. The big bang does not work like anything ordinary that you are used to imagining. The math is straightforward and unambiguous, but there is no good ordinary language description that corresponds to the math.

I find helpful this analogy of the space-time (4-dimension) expansion from the big bang: the surface (2D) of an expanding bubble. YMMV.

Re: Webb and Hubble confirm Universe's expansion rate

#144

Post by kaashif »

NateEag wrote: post #139
ducttapecrown wrote: post #51

Earlier quoted context omitted.

All the expert software engineers agree this is the most likely explanation. Have physicists looked into this?

> All the expert software engineers agree this is the most likely explanation. That's quite a strong claim. I'm skeptical. Sources? > Have physicists looked into this? They shelved it right next to "God Made The Universe" in the "Unfalsifiable Propositions" section, under the title "Grad Students Made The Universe."

I'm reading their comment as a joke about how software engineers tend to overestimate their own expertise on things like physics and are not actually anywhere close to experts.

Software engineers presenting weird pseudo science as serious physics is one way this manifests.

I could be wrong.

Re: Webb and Hubble confirm Universe's expansion rate

#145

Post by a_random_canuck »

westurner wrote: post #18

Hubble's law: https://en.wikipedia.org/wiki/Hubble%27s_law Expansion of the universe: https://en.wikipedia.org/wiki/Expansion_of_the_universe : > While objects cannot move faster than light, this limitation only applies with respect to local reference frames and does not limit the recession rates of cosmologically distant objects Given that v is velocity in the opposite direction, and c is the constant reference fram…

> do we account for velocity in determining whether light traveling at c towards earth will ever reach us?

No, because the speed of light is constant for all observers. From our frame of reference on earth, light from distant receding galaxies is always moving towards us at exactly the speed of light, c. Those galaxies also observe the light moving away from them at exactly c.

That seems contradictory and unintuitive, that two observers moving away from each other both measure light moving c relative to themselves, but that’s reality.

It’s another measurement that changes: if c is always constant, then it must be the passage of time and the distance travelled that we observe differently.

Re: Webb and Hubble confirm Universe's expansion rate

#146

Post by mjfl »

digging wrote: post #127
mjfl wrote: post #57

It is very fortunate that the universe is expanding. This provides a virtually unlimited source of energy.

Without being able to harvest dark energy, it's actually the exact opposite.

The extra energy comes from the increase in gravitational potential energy between objects. The accelerating increase in this potential energy implies the total energy of the universe is increasing. I’m not talking about harvesting dark energy directly.

Re: Webb and Hubble confirm Universe's expansion rate

#149

Post by puzzledobserver »

digging wrote: post #127
mjfl wrote: post #57

It is very fortunate that the universe is expanding. This provides a virtually unlimited source of energy.

Without being able to harvest dark energy, it's actually the exact opposite.

What would a hypothetical dark energy engine look like?

Re: Webb and Hubble confirm Universe's expansion rate

#150

Post by lp4vn »

pdonis wrote: post #113
arcastroe wrote: post #94

Earlier quoted context omitted.

> In your explanation, I think we'd expect to see some very distant, very slow-moving galaxies moving toward us Thank you, but I suppose I'm not really questioning the big bang piece. My question was mostly in regards to the continued acceleration piece. Feel free to disregard the "in random directions" part of my original post. I'm picturing more of an explosion in empty space. A firework or granade of sorts. Any in…

> I'm picturing more of an explosion in empty space. No, that's not what the big bang is. > this would imply a "center" to the explosion, which I've also heard is not the case That's correct. The big bang does not work like anything ordinary that you are used to imagining. The math is straightforward and unambiguous, but there is no good ordinary language description that corresponds to the math.

As I understand it, before the big bang the whole observable universe was contained in a small sphere and then it started to expand metrically. Is this interpretation correct?

Another thing: suppose I point a laser beam to the space and by chance this laser beam never finds any kind of matter in its way, where is this laser going to? To an infinite void? Is it correct to say that stars radiate energy to the infinite then?

Post reply on HN