A tiny swarm of asteroids will come waltzing through our neck of the cosmic woods this weekend, as planet Earth is in for a series of close encounters on Saturday. Three space rocks are due to cruise by Earth tomorrow, in a multi-asteroid flyby that will bring one of the objects as close as 1.3 million miles from our planet’s surface. The three objects will swing by at different times throughout the day, each of them making an individual close approach rather than buzzing our planet as a group. The rocks couldn’t be more different from one another, as they vary in speed, size, and moment of discovery. However, these objects do share a common trait, as all of them are classified as Apollo-type asteroids.
The first one to make the trip through our corner of the solar system on December 21 is a 128-foot asteroid known as 2019 YM. The rock was discovered merely a day ago and is the smallest and fastest of the bunch. According to a report released yesterday by NASA’s Jet Propulsion Laboratory (JPL), the tiny asteroid orbits the sun once every 1,157 days, or 3.1 years, and is currently embarked on its second-ever flyby of Earth. The rock previously visited our planet in early December 2015, when it came within 17.1 million miles of the terrestrial surface. The object will creep in a lot closer to Earth tomorrow, marking the closest approach of the day.
The newfound space rock is expected to swing by in the early hours of the morning, reaching its closest point to Earth at 4:12 a.m. EST. The asteroid will safely hurtle past us at speeds of a little over 38,300 mph, flying as close as 5.5 times the distance between our planet and the moon.
After tomorrow’s close brush with Earth, it will be quite sometime before the rock returns to our corner of space. The asteroid will pass by Jupiter in 2021 as it treks the outer solar system and won’t double back until nearly four decades after, in 2058. Its next flyby of Earth will bring the rock only 7.1 million miles from our planet.
A little over 10 hours after asteroid 2019 YM darts past us on Saturday, a slightly larger Apollo asteroid will cruise by Earth in what will be the slowest and farthest approach of the day. Our second celestial visitor is called 2013 XY20 and is estimated to be about 154 feet wide. The space rock will gracefully float by at a speed of just 4,272 mph, or 5.5 times the speed of sound, reaching Earth’s vicinity at 2:35 p.m. EST. As it does so, the object will come within 4.3 million miles of our planet, or 18.2 times the distance to the moon.
As its name suggests, this second celestial interloper has been on NASA’s radar for quite some time. Asteroid 2013 XY20 was discovered six years ago, about three weeks before it swung by Earth in mid-December 2013. This Apollo asteroid circles the sun once every 439 days, or 1.2 years, frequently passing by our planet as it journeys around the giant star. Sometimes, the rock swings by on consecutive years; other times, it leaves a six-year gap between its visits.
NASA predicts that the asteroid will double back in six years’ time, making its next flyby of Earth in 2025. After that, the rock will return in 2026.
The third and final close encounter of the day will get planet Earth re-acquainted with another frequent traveler through our cosmic neighborhood — a 213-foot Apollo asteroid dubbed 2017 XQ60. The rock was first spotted two years ago, exactly one week before it buzzed Earth on December 21, 2017. The asteroid is gearing up for yet another December 21 close approach and will pop by in the late hours of the evening, flying past us at 9:10 p.m. EST. At the time, the rock will be some 2.6 million miles from Earth, or 11 times the lunar distance, cruising through space at a velocity of 19,800 mph.
JPL data shows that the asteroid, which is the heftiest of the group, takes around a year to complete a full orbit around the sun. The rock has been buzzing Earth on a yearly basis since 2001 and will continue its annual flybys up until the year 2037.
The multi-asteroid flyby comes hot on the heels of another close approach that occurred this morning, when planet Earth was visited by a massive 1,771-foot Apollo asteroid, as previously covered by The Inquisitr.
Paradox-Free Time Travel Is Theoretically Possible, Researchers Say – WBFO
“The past is obdurate,” Stephen King wrote in his book about a man who goes back in time to prevent the Kennedy assassination. “It doesn’t want to be changed.”
Turns out, King might have been onto something.
Countless science fiction tales have explored the paradox of what would happen if you do something in the past that endangers the future. Perhaps one of the most famous pop culture examples is Back to the Future, when Marty McFly went back in time and accidentally stopped his parents from meeting, putting his own existence in jeopardy.
But maybe McFly wasn’t in much danger after all. According a new paper from researchers at the University of Queensland, even if time travel were possible, the paradox couldn’t actually exist.
Researchers ran the numbers, and determined that even if you make a change in the past, the timeline would essentially self-correct, ensuring that whatever happened to send you back in time would still happen.
“Say you travelled in time, in an attempt to stop COVID-19’s patient zero from being exposed to the virus,” University of Queensland scientist Fabio Costa told the university’s news service.
“However if you stopped that individual from becoming infected — that would eliminate the motivation for you to go back and stop the pandemic in the first place,” said Costa, who co-authored the paper with honors undergraduate student Germain Tobar.
“This is a paradox — an inconsistency that often leads people to think that time travel cannot occur in our universe.”
A variation is known as the “grandfather paradox” — in which a time traveler kills their own grandfather, in the process preventing the time traveler’s birth.
The logical paradox has given researchers a headache, in part because according to Einstein’s theory of general relativity, “closed time-like curves” are possible, theoretically allowing an observer to travel back in time and interact with their past self — and potentially endangering their own existence.
But these researchers say that such a paradox wouldn’t necessarily exist, because events would adjust themselves.
Take the coronavirus patient zero example. “You might try and stop patient zero from becoming infected, but in doing so you would catch the virus and become patient zero, or someone else would,” Tobar told the university’s news service.
In other words, a time traveler could make changes — but the original outcome would still find a way to happen. Maybe not the same way it happened in the first timeline; but close enough so that the time traveler would still exist, and would still be motivated to go back in time.
“No matter what you did, the salient events would just recalibrate around you,” Tobar said.
The paper, “Reversible dynamics with closed time-like curves and freedom of choice,” was published last week in the peer-reviewed journal Classical and Quantum Gravity. The findings seem consistent with another time travel study published this summer in the peer-reviewed journal Physical Review Letters. That study found that changes made in the past won’t drastically alter the future.
Best-selling science fiction author Blake Crouch, who has written extensively about time travel, said the new study seems to support what certain time travel tropes have posited all along.
“The universe is deterministic and attempts to alter Past Event X are destined to be the forces which bring Past Event X into being,” Crouch told NPR via email. “So the future can affect the past. Or maybe time is just an illusion. But I guess it’s cool that the math checks out.”
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Chang'e-4 lander finds radiation levels on the moon 2.6 times higher than at space station – Firstpost
Agence France-PresseSep 28, 2020 10:50:29 IST
As the US prepares to return humans to the Moon this decade, one of the biggest dangers future astronauts will face is space radiation that can cause lasting health effects, from cataracts to cancer and neurodegenerative diseases.
Though the Apollo missions of the 1960s and 1970s proved it was safe for people to spend a few days on the lunar surface, NASA did not take daily radiation measurements that would help scientists quantify just how long crews could stay.
This question was resolved Friday after a Chinese-German team published in the journal Science Advances the results of an experiment carried out by China’s Chang’E 4 lander in 2019.
“The radiation of the Moon is between two and three times higher than what you have on the ISS (International Space Station),” co-author Robert Wimmer-Schweingruber, an astrophysicist at the University of Kiel told AFP.
“So that limits your stay to approximately two months on the surface of the Moon,” he added, once the radiation exposure from the roughly week-long journey there, and week back, is taken into account.
There are several sources of radiation exposure: galactic cosmic rays, sporadic solar particle events (for example from solar flares), and neutrons and gamma rays from interactions between space radiation and the lunar soil.
Radiation is measured using the unit sievert, which quantifies the amount absorbed by human tissues.
The team found that the radiation exposure on the Moon is 1,369 microsieverts per day – about 2.6 times higher than the International Space Station crew’s daily dose.
The reason for this is that the ISS is still partly shielded by the Earth’s protective magnetic bubble, called the magnetosphere, which deflects most radiation from space.
Earth’s atmosphere provides additional protection for humans on the surface, but we are more exposed the higher up we go.
“The radiation levels we measured on the Moon are about 200 times higher than on the surface of the Earth and five to 10 times higher than on a flight from New York to Frankfurt,” added Wimmer-Schweingruber.
NASA is planning to bring humans to the Moon by 2024 under the Artemis mission and has said it has plans for a long term presence that would include astronauts working and living on the surface.
For Wimmer-Schweingruber there is one work-around if we want humans to spend more than two or three months: build habitats that are shielded from radiation by coating them with 80 centimeters (30 inches) of lunar soil.
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