The answer is “Gravity moves at light speed.” To avoid the click bait title, here’s the punchline from the article:
The simplest and most convincing observation that gravity travels at the speed of light came in 2017, when both gravitational waves and light were observed from a merger of two neutron stars. Despite traveling more than 100 million light-years, the two signals arrived at Earth only 1.7 seconds apart! This means the speed of light and the speed of gravity differ by no more than 1 part in a quadrillion — in other words, they differ by no more than 0.0000000000001 percent.
To be really pedantic, gravity moves at the speed of light in a vacuum. OTOH my understanding of the speed of light in a medium is that it’s the result of photons being absorbed and re-emitted, and the speed of any individual photon is always exactly c. Personally, I’d prefer the convention that “the speed of light” without qualifiers always means c, but that ship appears to have sailed long ago.
OTOH my understanding of the speed of light in a medium is that it’s the result of photons being absorbed and re-emitted, and the speed of any individual photon is always exactly c.
I am an experimentalist and so if a theoretician reads this they will probably tell you that I am wrong…
I think that the description of a photon being “absorbed” and “re-emitted” could be used to describe the picture from the point of view of quantum field theory (which I don’t claim understand), because within this theory the photon/electron and even electron/electron interactions are mediated by photons that are created and annihilated during those interactions. Whenever the “photon” exists it will travel with speed c. As light travels through a material it is traveling as a wave of electrons influencing each other, similar to how water waves travel through water, and since these interactions of the electrons pushing each other are formally described by the photons popping into and out of existence I think one could correctly use the language of “absorbed” and “re-emitted”.
But personally I think that it can be a bit confusing, because the absorption and emission of light by materials is often used to mean something very different… Absorption more commonly refers to a resonant interaction in which a photon is destroyed and a molecule (or atom, or crystal, etc…) comes into an excited state. The molecule that becomes excited can remain excited for quite a long time (usually picoseconds - microseconds), and the re-emission of the light often comes in a completely different direction and even a different wavelength than the original photon. So using the language of “absorption” and “emission” in this context can also generate confusion,.
Personally when I imagine the propagation of light through a material I think about it in terms of the polarizability of the medium. When the light propagates through a medium, you don’t need a “photon”. The wave is being carried by the electrons oscillating (these are very small oscillations - unless you are using powerful lasers, then you reach the beautiful world of non-linear optics). The speed of propagation of this wave through the medium depends on how far the wave can travel through the material with every oscillation. There is a nice description of this semi-classical process in the Feyman Lectures: www.feynmanlectures.caltech.edu/I_31.html
gravity moves at the speed of light in a vacuum
Hmmm… Always? Maybe some funky things happen as the wave passes by a black hole.
From the article: A third idea is that they weren’t objects at all. Palomar Observatory isn’t too far from the New Mexico deserts where nuclear weapons testing occurred. Radioactive dust from the tests could have contaminated the photographic plates, creating bright spots on some images and not others. Given similar vanishings seen on other photographic plates of the 1950s, this seems quite possible.
That’s because asteroids with organics that create life are sent out by the Pathagorath, the screeching glutton that dwells in the blinding. He’s the creature that lives in the center of the galaxy and sends out asteroids to seed worlds with life so that he can devour their souls. You see when we die our souls are eternally digested in his bottomless belly, and without ever increasing nourishment his metabolism would cease to produce the necessary excretions our galaxy needs for time to exist and we would simply blink out of existence. We owe him eternally for our existence as well as our damnation.
Lemmy Connect preview with Chrome even if you have Firefox installed. You can click Open External but for me once the ads become obtrusive, I’m already over it and stop reading. Now I don’t click those sites at all but come to the comments to see if a summary bot posted
I have ad blockers on my PC, but haven’t gotten around to putting any on my phone. It’s rarely a problem as I don’t visit many sites on my phone. But I should probably add one. I was just pointing out an experience I had. I think you were a bit rude with your comment. Please try to be more kind in the future; that’s what helps communities like Lemmy thrive
I really like his content, but his way of speaking (can’t even say what exactly) is somehow perfect for my brain to completely tune out. I have to really focus on it to actually mentally process it.
Agreed. He’s very monotone and I don’t think his mic is very good. I like the content, not trying to tear someone down but he’s not a small channel anymore. Wish the production value was a bit higher to engage us more. I want to watch every video but I only watch the ones that I really want to know more about, for this reason.
But, in EST and similar time zones, it’s December 11, not 12, right? The headline says 12th; the article says Monday the 11th. And based on a different article I previously read, I set myself a calendar reminder for the 11th, so I’m leaning that way. Maybe they meant the 12th UTC?
Edit: Yep, in EST and other Western TZs, I’m reading the 11th–Monday night.
So, for example, in Cordoba, Spain, the mid-point of the event will be at about 1:15:45 UTC, or 2:15:45 a.m. local time, on December 12, 2023. And in Miami, Florida, the mid-point of the event will be at about 8:24:54 p.m. local time on December 11, 2023. That’s the same as 1:24:54 UTC on December 12, 2023. Find the exact timing for your location here.
Please note it’s Dec 11 EST. You may have seen my old comment that said the title’s 12th EST. So it’s best to follow the direct pages linked in the article for your timezone
The writing is at morning program levels of goofiness; it’s jarring. At 17 kg this meteorite would be worth over a million USD if it was gold. It’s like the writer is taking a piss at the poor guy who hoped to get some money out of it.
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