Amazing picture thread

[jabir]

[jabir]

The Antikythera mechanism, retrieved from 45m in sea off the Greek island Antikythera, contains a system of wheels, or gears. Variously dated from 87 BC to 205 BC, but safely around 2,000 years old.










The device was found as one piece in the remains of a 34x18x9 cm box, later separated into three main fragments which have become 82 after conservation works. Four of these fragments contain gears, while inscriptions are found on many of the 82 pieces. The largest gear is approximately 14 cm diameter and originally had 223 teeth.

Debate as expected, some archaeologists believe it is an analogue computer, others a clock, a calendar, or a complex planetarium. They agree only that it was made centuries ahead of its time.

[jabir]

[jabir]

Saying goodbye to a species, the last male Northern White Rhino. A powerful photo of 2018.

[jabir]

Why?

[uncle junior]

45 minutes in a quiet room.....what's the big deal......and what's a negative decibel???

[jabir]

45 minutes in a quiet room.....what's the big deal......and what's a negative decibel???

0 dB does not mean no sound, it means a sound level where the sound pressure is equal to that of the reference level. This is a small pressure, but not zero. It is also possible to have negative sound levels: - 20 dB would mean a sound with pressure 10 times smaller than the reference pressure, ie 2 μPa.

Thanks google, am none the wiser.

[jabir]

Interesting addendum: Microsoft have constructed an "anechoic chamber" in Building 87 at their Redmond HQ where their hardware labs are based. Products like the Surface computers, Xbox and Hololens have all been developed here. MS engineers built the chamber to help test new equipment they were developing, and in 2015 it set the official world record for silence when the background noise level inside was measured at an ear-straining -20.6 decibels.

To put that in context, a human whisper is about 30 decibels while the sound of someone breathing normally comes in at just 10 decibels. It gets close to the limit of what should be possible to achieve without creating a vacuum – the noise produced by air molecules colliding with each other at room temperature is estimated to be about -24 decibels. The limit of human hearing is thought to be around 0 decibels, although just because our ears cannot pick it up, it does not mean no sound present, hence it is possible to get a negative value.




“It is a very unique experience inside with the door closed,” says Munroe, part of the team. “When you stop breathing, you can hear your heart beating and the blood flowing in your veins. I don’t stay inside with the door closed very often.”

The chamber sits at the heart of a nest of six concrete rooms, each with walls up to 12 inches thick and set aside from the sandwiching rooms by up to 4', to help cut any sounds reaching the chamber by around 110 decibels. If a jet was taking off just outside the building, you would hear little more than a whisper inside the final concrete bunker.

The chamber itself floats on top of 68 vibration damping springs mounted on its own separate foundation slab; this means it is not in direct contact with the building around it at any point.

The chamber is a 21' cube, each of its six surfaces is lined with clusters of 4' wedges of sound absorbing foam which helps prevent any echoes bouncing off the walls from any sound produced inside. The floor is made from steel cables, the same kind used to stop fighter jets as they land on aircraft carriers, knitted together like a trampoline net above the foam wedges on the bottom of the chamber.

Seals around the doors of the chamber and the onion layer of rooms surrounding it also help to keep noise from leaking in. It even boasts a specially designed air conditioning system and sprinkler system in the 4' gap between the chamber and the concrete wall of the room it sits within.

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You would think that a place so quiet would also be peaceful. But for those who spend any time in there, it is far from the case. Gopal often gives visitors to MS a tour of the audio laboratories, which includes a trip inside the anechoic chamber, and most find the experience very uncomfortable. “Some people want out within a few seconds. They say they just can’t be in there. It unsettles almost everybody. They can hear people breathing on the other side of the room and hear stomachs gurgling. Some of them feel dizzy.”

“There are people who do love it and say it is meditative; they find it relaxing. But the longest I’ve seen anyone stay inside is an hour, and that was to raise money for charity. I think if you spent too much time in there it would drive you crazy. Every swallow you make is really loud.”

But the silence has a far more constructive use than simply listening to the grumblings and gurglings of the human body. Instead, MS listen in on electronic equipment while it is in use. They are looking for tiny vibrations that are produced by capacitors on electronic circuit boards as current passes through them. These can make the components on the board produce annoying hums that can be off-putting for consumers.

“We try to find out where on the board a noise is coming from and what strategies we can use to mitigate it,” explains Munroe. “For example, we have tried putting capacitors in different configurations so the vibrations cancel each other out.”

They also look at other components on computers that can make noises, from the power supply to the cooling fan and the sound from your display as you increase the backlighting.

But not all of their work is about trying to find unpleasant noises. They also help to tune the sound that different components should make. “We look at keyboard noise,” says Munroe. “Getting a keyboard to sound a particular way is a critical thing. We do experiments on different types of materials for the keys, different spring mechanisms – all to get the right feel and sound from a keyboard.”

Speakers also get put through their paces in the laboratory as it allows the team to use the sensitive equipment to look for any distortion or clipping of frequencies. The performance of microphones in products can also be tested in a similar way.

Recently, engineers have also been using the chamber to test the performance of new technologies such as MS's AI assistant Cortana and developing techniques to replicate three-dimensional sound for its virtual reality HoloLens display.

The team has also had a number of applications from researchers who want to use the chamber to conduct biomedical research. There is some research, for example, that suggests short-term sensory deprivation can induce temporary psychotic episodes and hallucinations, which could help in the study of schizophrenia.

Gopal is reluctant to branch into medical and behavioural studies. Putting patients into such an unusual environment would likely require volumes of special legal clearance. The laboratory’s busy testing schedule also makes it difficult to find time for such studies. On a personal level, however, the real power of the chamber for Munroe and Gopal comes when they leave after a spell inside.

“When you open the door it is almost like a waterfall of sound hitting your ears,” says Munroe. “It is like stepping out into a different world. You hear things that you wouldn’t normally notice. It gives you a new perspective.”

[Klondyke]

If there is a physical unit in Thailand that nobody would care less, then it is just a "db".

[Halfaboy]

Extremely interesting. A complete new world where I was not aware of.

Thanks....

[uncle junior]

0 dB does not mean no sound, it means a sound level where the sound pressure is equal to that of the reference level. This is a small pressure, but not zero. It is also possible to have negative sound levels: - 20 dB would mean a sound with pressure 10 times smaller than the reference pressure, ie 2 μPa.

Thanks google, am none the wiser.

don't understand it but at least i can quit trying to get my head around what negative sound would be

[Ukan Kizmiaz]

Saying goodbye to a species, the last male Northern White Rhino. A powerful photo of 2018.

yes sad/ bad indeed - I wonder if he knew he was the last ( after all animals know things)

[nidhogg]

yes sad/ bad indeed - I wonder if he knew he was the last ( after all animals know things)

He was the last male. I think there are still two females alive, but clearly the species is functionally exstinct. I read a while ago of conservation efforts base around crossing with Southern white rhinos and breeding back. Slim chance i would have thought.

[jabir]

Surely they would have extracted his DNA/sperm for safe keeping, so could be the remaining fems are infertile. Cross breed with a similar species? Not the same and pointless really, to save one while driving others to extinction.

[baldrick]

errr.. photoshopped

croc in north america - naah

[nidhogg]

^ not sure on that photo, but it is a thing:
https://www.telegraph.co.uk/news/new...crocodile.html

[baldrick]

yes - but I think the other photo is a seppo photoshop to make them feel tough

not just because it is a croc , but the shadow and lighting are different on each animal

the croc is probably from the jumping ones in the NT

[jabir]

errr.. photoshopped

croc in north america - naah

No problem with crocs in America, loads of them, though it does look odd whether it's a gator or a croc; the only ways I know to tell the difference is crocs have more pointed snouts, and lower side teeth poking out.

[SKkin]

^Mostly alligators in the US. South Florida the only place in the US with crocs.

[jabir]

Mars



by Curiosity Rover



Those layers same same here, could be water erosion?

[Takeovers]

Those layers same same here, could be water erosion?

I don't know. But to me it looks like layers of sediment later eroded by wind and dust in the air. Thin as the martian atmosphere is multi millions of years can do that.

Really amazing we have those photos.

[bobo746]

Saint Michel Chapel on a small island in the middle of the Serre-Ponçon artificial lake



Ash and explosions erupt from Sicily's Mount Etna volcano on December 25, 2018.

[jabir]

Is this 3,800 year old tablet the world's first consumer complaint?

[Takeovers]

Crew Dragon on the pad. Ready for the unmanned test flight.

[OhOh]

Photo taken on March 30, 2018 shows the Potala Palace after a snowfall in Lhasa, Southwest China's Tibet autonomous region.



Aerial photo shows the snow-covered Potala Palace in Lhasa, capital of Southwest China's Tibet autonomous region, Dec 19, 2018.