This event led to the discovery of ‘infrasound’ or very low frequency sound that travels very long distances.
It’s currently still used to detect (above ground) nuclear explosions as part of the Comprehensive Nuclear Test Ban Treaty (CTBT).
There is a site in the ‘Windless Blight’ in Antarctica near McMurdo Station that a couple of techs go dig out and maintain every year. I believe there are about 30 around the world.
I've read in other sources that the force of the main eruption in 1883 was equivalent to around 100 megatons of TNT. The dust that it ejected into the atmosphere was not only the cause of the bright sunsets that inspired artists in Europe over the next few years, but also caused a global cooling by something like 1 degree (Celsius) for the next two years.
It was a temporary measure, and the only volcano I know that would significantly move the needle is Yellowstone. And I really, really don’t want that to go off while I’m still alive, I like North America when it’s not covered in ash.
I think I watched that video 15 times ... at 4.4km / 2.7miles away those must be larger-than-house sized chunks of rock falling ! (clearly visible to the left of the explosion).
"ACTNews, PANDEGLANG – Tsunami hit coastal areas around Sunda Strait in Pandeglang, Serang, and South Lampung Regencies. The disaster happened on Saturday (12/22) at 9:27 p.m., Indonesian Bureau of Meteorology Climatology and Geophysics (BMKG) predicted that the massive wave was caused by underwater flank collapse after the eruption of Anak Krakatau Mountain as well as the tidal force caused by the full moon." - https://act.id/en/news/detail/tsunami-hit-pandeglang-serang-...
Yes, it's real. Tides are higher around the full moon due to the earth, sun, and moon being (roughly) aligned. If it was already high tide, adding a tsunami on top of it is going to be more impactful than at low tide.
Regarding magnitude of these types of events, NOAA does amazing work collecting data on tsunami events with impressive energy simulations. As some point I had seen several videos from the Chile event in 2010 that showed the shockwaves traveling around the earth multiple times, but I can't seem to find those videos now.
Yes, once it's kinetic energy drops below that of the average air molecule, it'll become imperceptible to instruments; lost in the noise, or rather, becoming part of the noise.
Interesting. Besides 'Brownian' noise you are probably correct that whatever noise remains is to some extent the result of a lot of stuff that happened in the past that is too small now in influence to be identified. I never looked at it that way, thank you.
Specifically, the energy that is sound will gradually dissipate into energy that is heat. Brownian motion happens on the microscopic level; we perceive it on the macroscopic level as temperature. Temperature is essentially the combined, average kinetic energy of Brownian motion.
Most types of energy gradually turn into heat, including light, macroscopic kinetic energy, released gravitational potential energy, etc.
If you catch a baseball, the kinetic energy of the baseball turns into heat within your muscles (and skin, in the form of friction between the ball and your hands). If you walk down stairs, the gravitational potential energy that you're releasing turns into heat as well, as friction in your joints. Light shining on your skin turns into heat and warms it, as on a bright and sunny day. The electrical energy of a computer converts largely into heat, hence the need for cooling.
There are also theories that all matter may eventually decay, including all atoms and eventually even protons after 10^34 years (though proton decay has not yet been experimentally observed). https://en.wikipedia.org/wiki/Proton_decay
As someone on Quora wrote, "Heat is energy's final grave". The concept of "heat death of the universe" derives from the idea that, eventually, most forms of energy will decay into heat.
There is no evidence remaining that the sound exists. It would be like trying to detect an energy below the noise floor of vacuum energy; there is no proof that you can construct that it exists. Once it's part of the background noise floor, it effectively seizes to exist.
Because there is no reasonable way to possibly prove the sound still exists.
To find out if something beyond the observable universe exists, you simply wait for the light to reach you. Every minute your observable universe grows larger and you see more stuff, the obvious conclusion is that there is more stuff.
But the random movements of air molecules allow for no analysis that there is a quantum of a sound traveling through it. It cannot be reasonably proven that the sound still exists. You can't wait to see if you notice more random sounds or anything, it's gone, part of the background noise. The information in the sound has been destroyed for any way to measure it via the movements of air molecules.
You cannot wait for light from beyond the observable universe. That is the definition of the observable universe.
The universe is expanding. The further away something is from us, the faster it is moving away from us.
The part outside of the observable universe is so far away, that it is moving away from us at a speed faster then light. So we will never know anything about it.
Yes. As the waves propagate their amplitude generally decreases. Imagine dropping a rock in a pond, and picture how the wave worked around it drops as it expands. There's both diffusion of the force over a wider area and there's some inertia in the materials that the wave has to overcome.
However, truly the pond will never be the same again. Nor, chaos theory tells us, will the world. In time, across the globe, countless lives will be lived and lost which never would have been lived and lost had the rock not been dropped in that pond.
Is information ever lost? Not a rhetorical question, I genuinely want to know. Once the vibration due to a sound become smaller than a certain level, do quantum effects make it disappear entirely
Not just quantum effects (although they can dominate especially at low temperatures or superfluid/conducting states), but thermodynamic effects. Once the energy falls below ~kT/2 in a dissipative system (quadratic hamiltonian terms) you've lost the information.
From a practical perspective, yes; but I get the feeling you're not asking that ;).
Let's say that we know everything possible about the universe at a time t (in some reference frame). Can I reconstruct what happened at any time in the past? If I can, then it seems reasonable to say that 'no information has been lost' (going the other way suggests that no information gets created either).
A lot of Physicists seem to think the answer is yes, we can construct the past if we actually knew everything. The evolution of the wavefunction is unitary, so you should be able to run the universe backwards to find out what happened (unless wavefunction collapse is real, in which case, we're losing information all the time). Note that in order to do this, you need to know the entire wave function; which isn't measurable.
However, under our current understanding of black holes, the answer seems to be "Looks like it?"
Since we don't know how to resolve General Relativity with Quantum Mechanics, we can't really say with confidence whether the universe can 'be played backwards' or not.
Let's take the information 'The universe exists'. How can that information get lost? Wouldn't the universe have to disappear for that to happen? I have never heard about a model of reality where that is a possibility.
I think by information they mean more concrete things. For instance, imagine a bird landing on a branch. If someone is around to see it, they know that if happened. If no one is around though, once the bird flies away and the branch stops shaking, the information that a bird had landed on the branch is gone.
I wonder whether the sound wave got stronger again as it reached the opposite side of the globe from the source. Would it have made it back into the audible range? Maybe not, since I imagine that intervening mountains and such would disrupt or change the speed of the waves.
> The British ship Norham Castle was 40 miles from Krakatoa at the time of the explosion. The ship’s captain wrote in his log, “So violent are the explosions that the ear-drums of over half my crew have been shattered. My last thoughts are with my dear wife. I am convinced that the Day of Judgement has come.”
https://www.skyandtelescope.com/press-releases/astronomical-...