Share Your Interesting But Not Very Useful Facts
Discussion
KaraK said:
hairy v said:
The fastest manmade object isn't a hypersonic jet or spacecraft, but a large manhole cover....
When the US started doing underground nuclear testing, nobody really knew what would happen. One test bomb was placed at the bottom of a 485-foot deep shaft on July 26, 1957, and someone thought it was a good idea to put a half-ton iron manhole cover on top to contain the explosion. The bomb turned the shaft into the world's largest Roman candle, and the manhole cover was nowhere to be found.
Robert Brownlee, an astrophysicist who designed the test, wanted to repeat the experiment with high-speed cameras so he could figure out what happened to the cover. So another experiment was created, this time 500-feet deep, and a similar half-ton manhole cover was placed on top. On August 27, 1957, they detonated the bomb. The high-speed cameras barely caught a view of the cover as it left the top of the shaft and headed into oblivion. Brownlee used the frames to calculate the speed to be more than 125,000 miles per hour.... more than five times the escape velocity of the Earth, and the fastest man-made object in history.
Physicists have debated the whereabouts of the two manhole covers ever since. Recently, with the help of supercomputers and a lot more scientific knowledge, physicists are certain that they wouldn't have had time to burn up completely before exiting the atmosphere. This means both of the remaining pieces would have passed Pluto's orbit sometime around 1961 and are way beyond the edge of the solar system by now.
Always a great story, I have to say though [citation needed] on the last bit. Whenever I see the anecdote repeated that "physicists" are "certain" it would have survived the trip out of the atmosphere there's never any names or links to work supporting it.When the US started doing underground nuclear testing, nobody really knew what would happen. One test bomb was placed at the bottom of a 485-foot deep shaft on July 26, 1957, and someone thought it was a good idea to put a half-ton iron manhole cover on top to contain the explosion. The bomb turned the shaft into the world's largest Roman candle, and the manhole cover was nowhere to be found.
Robert Brownlee, an astrophysicist who designed the test, wanted to repeat the experiment with high-speed cameras so he could figure out what happened to the cover. So another experiment was created, this time 500-feet deep, and a similar half-ton manhole cover was placed on top. On August 27, 1957, they detonated the bomb. The high-speed cameras barely caught a view of the cover as it left the top of the shaft and headed into oblivion. Brownlee used the frames to calculate the speed to be more than 125,000 miles per hour.... more than five times the escape velocity of the Earth, and the fastest man-made object in history.
Physicists have debated the whereabouts of the two manhole covers ever since. Recently, with the help of supercomputers and a lot more scientific knowledge, physicists are certain that they wouldn't have had time to burn up completely before exiting the atmosphere. This means both of the remaining pieces would have passed Pluto's orbit sometime around 1961 and are way beyond the edge of the solar system by now.
The only times I've seen physicists do any actual math on it the answer always comes out that it's almost certain to have vaporized well before it reached space, if there's new data out there though it would be cool to see.
If the Arctic snow cap melts completely it won't make any difference to sea levels.
No Egyptian pharaoh was ever buried in a pyramid.
Fleas carried the plague. Mice carried fleas. If you had a cat you were unlikely to get the plague because the cats stopped/killed the mice. Many single women had cats and people often believed that they were witches as they didn't catch the plague. Hence, why cats are associated with witches to this day.
(All from Neil Degrasse Tyson)
No Egyptian pharaoh was ever buried in a pyramid.
Fleas carried the plague. Mice carried fleas. If you had a cat you were unlikely to get the plague because the cats stopped/killed the mice. Many single women had cats and people often believed that they were witches as they didn't catch the plague. Hence, why cats are associated with witches to this day.
(All from Neil Degrasse Tyson)
Frimley111R said:
If the Arctic snow cap melts completely it won't make any difference to sea levels.
No Egyptian pharaoh was ever buried in a pyramid.
Fleas carried the plague. Mice carried fleas. If you had a cat you were unlikely to get the plague because the cats stopped/killed the mice. Many single women had cats and people often believed that they were witches as they didn't catch the plague. Hence, why cats are associated with witches to this day.
(All from Neil Degrasse Tyson)
Cats are susceptible the plague, and quite efficient at spreading it. No Egyptian pharaoh was ever buried in a pyramid.
Fleas carried the plague. Mice carried fleas. If you had a cat you were unlikely to get the plague because the cats stopped/killed the mice. Many single women had cats and people often believed that they were witches as they didn't catch the plague. Hence, why cats are associated with witches to this day.
(All from Neil Degrasse Tyson)
https://www.cdc.gov/plague/healthcare/veterinarian...
Frimley111R said:
If the Arctic snow cap melts completely it won't make any difference to sea levels.
No Egyptian pharaoh was ever buried in a pyramid.
Fleas carried the plague. Mice carried fleas. If you had a cat you were unlikely to get the plague because the cats stopped/killed the mice. Many single women had cats and people often believed that they were witches as they didn't catch the plague. Hence, why cats are associated with witches to this day.
(All from Neil Degrasse Tyson)
The first one is not quite true. Read here: https://sealevel.nasa.gov/news/261/melting-ocean-i...No Egyptian pharaoh was ever buried in a pyramid.
Fleas carried the plague. Mice carried fleas. If you had a cat you were unlikely to get the plague because the cats stopped/killed the mice. Many single women had cats and people often believed that they were witches as they didn't catch the plague. Hence, why cats are associated with witches to this day.
(All from Neil Degrasse Tyson)
Of course the biggest effect is ice on land melting into the sea.
nismocat said:
Rotor blades on USA built helicopters go anti clockwise whereas European go clockwise.
There’s also a correlation between where the pilot sits.
Not sure where the UK is with all this. Do we even make helis?
On my Enstrom the pilot sits in left seat but on my R44 you sit in right seat, no idea why, there is no other problem though, the collective is on the left and the pedals work the same, on US helicopters when you hover taxi the left pedal turns you left & vice versa, not sure about Eurocopters though.There’s also a correlation between where the pilot sits.
Not sure where the UK is with all this. Do we even make helis?
classicaholic said:
nismocat said:
Rotor blades on USA built helicopters go anti clockwise whereas European go clockwise.
There’s also a correlation between where the pilot sits.
Not sure where the UK is with all this. Do we even make helis?
On my Enstrom the pilot sits in left seat but on my R44 you sit in right seat, no idea why, there is no other problem though, the collective is on the left and the pedals work the same, on US helicopters when you hover taxi the left pedal turns you left & vice versa, not sure about Eurocopters though.There’s also a correlation between where the pilot sits.
Not sure where the UK is with all this. Do we even make helis?
Fermit said:
eldar said:
In the USA in 1900, between 25% and 30% of cars were powered by electricity.
You could ask, if they didn't have staying power then why should they now.Edited by QJumper on Monday 1st January 19:49
Fermit said:
eldar said:
In the USA in 1900, between 25% and 30% of cars were powered by electricity.
You could ask, if they didn't have staying power then why should they now.Pb-Acid batteries, that acted as the primary batteries in these EVs had typically 30Wh/kg.
Li-Ion batteries in current EVs are around 230Wh/kg at the pack level.
And power density:
Pb-Acid: 180W/kg
Li-Ion: 300W/kg
And cost:
Li-Ion cells in 2010: $1100/kWh
Li-Ion cells in 2023: $100/kWh
eldar said:
Ford was just starting mass production, and petrol was cheaper and simpler, and only lead acid batteries.
In backwoods America there was little access to mains electricityfor charging, large distances between villages, towns, shops, etc. exceeded the meagre range of EVs so a petrol powered conveyance
was king.
So, little has changed then ?
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