[HN Gopher] Deep space radio signal reaches Earth after 8B years
___________________________________________________________________
Deep space radio signal reaches Earth after 8B years
Author : DocFeind
Score : 11 points
Date : 2024-09-21 22:03 UTC (57 minutes ago)
(HTM) web link (www.earth.com)
(TXT) w3m dump (www.earth.com)
| FridayoLeary wrote:
| >It turns out that visible matter -- like stars, planets, and
| galaxies -- makes up only about 5% of the universe's total mass-
| energy content.
|
| It always blows my mind how little we actually know. Everything
| we can observe and that science can describe is just a small
| fraction of what is actually out there. Since we don't know what
| dark matter is maybe its possible that it is all around us, here
| on Earth. I find that slightly disturbing for some reason.
| cryptoz wrote:
| I don't know anything about this at all. But I often think
| about it! I read something once that led me to believe there is
| no dark matter here on Earth. But I know nothing about this so
| don't take my word for it. My question has been, if the
| universe is expanding, am I expanding? Is Earth expanding?
| Surely it would have to be, (?!) because I keep getting told
| that the universe isn't expanding _into_ anything but rather,
| space itself is expanding. Well, I am part of space itself, so
| am I expanding? Ever so slightly?
|
| I think I read that no, in fact, I am not expanding. The space
| that I occupy is also not expanding. In fact, no space anywhere
| near us is expanding. The expansion (we think?!) happens due to
| dark matter (?) which is not evenly distrubuted and which we
| can kind of measure (?) and we can know that there isn't any
| here (?)
|
| Maybe someone who knows more about this can fill in the
| question marks or otherwise correct me.
| hollerith wrote:
| >if the universe is expanding, am I expanding? Is Earth
| expanding?
|
| No. I've heard experts say so explicitly. The exception is
| that if the expansion continues to accelerate, then billions
| of years from now first planets, then people will be ripped
| apart.
|
| Also the expansion is due to dark _energy_ which is quite
| different from dark matter. dark energy is everywhere but
| (for now) it is weak enough that, e.g., gravity can easily
| hold the planet together.
| johnea wrote:
| I totally agree.
|
| And the extent to which we're really ignorant, is generally not
| ackcowledged in the way things are generally described.
|
| For instance, in this article as is typical, the discrepancy
| between what current theory predicts, and what is currently
| observed, is described as the universe being "missing"
| something 8-)
|
| It's not that our theories are incorrect, it's that the
| universe is "missing" this thing that we predict should be
| there 8-)
|
| Maybe eventually the universe will correct it's error and meet
| human expectations 8-)
| johnea wrote:
| Really interesting topic, not so great article.
|
| Much better off reading the wilipedia page:
|
| https://en.wikipedia.org/wiki/Fast_radio_burst#FRB_220610
|
| In addition to the short summary of that specific event, it has a
| much more detailed treatment of the subject overall.
| mihaitodor wrote:
| Spot on! Given the domain name, I was expecting to see
| something more serious. The ads are an instant turnoff, never
| mind the content.
| sounds wrote:
| https://www.eso.org/public/news/eso2317/ is another decent
| writeup
| tectonic wrote:
| One likely source of FRBs are magnetars, which are just absurd
| objects. We wrote about them in Orbital Index a little while ago
| (https://orbitalindex.com/archive/2023-03-15-Issue-210/#magne...)
| :
|
| These highly magnetized neutron stars--objects only ~20 km in
| diameter--have magnetic fields that may reach up to 1015 Gauss, a
| quadrillion (thousand trillion) times our Sun's pitiful 1 Gauss.
| The energy density of just these magnetic fields (via E=mc2) is
| 10,000x the mass density of lead. Magnetars are a likely source
| of Fast Radio Bursts and can also emit giant gamma-ray flares--
| one flare, GRB 200415A, was seen to emit the same amount of
| energy as our Sun does over 100,000 years, but in only 0.016 s.
| We don't really know how these flares form, but if they involve
| large mass motions, they could also produce gravitational waves,
| something LIGO and other gravitational wave observatories are
| watching for. Near a magnetar, "X-ray photons readily split in
| two or merge. The vacuum itself is polarized, becoming strongly
| birefringent, like a calcite crystal. Atoms are deformed into
| long cylinders thinner than the quantum-relativistic de Broglie
| wavelength of an electron (pdf)," resulting in a breakdown of
| anything resembling what we think of as chemistry. It's believed
| that their magnetic fields decay relatively quickly over about
| 10,000 years, so magnetars are a transient state. We know of
| about 30 magnetars so far. Oh, and they may also have volcanoes
| (sort of).
___________________________________________________________________
(page generated 2024-09-21 23:01 UTC)