It could also be difficult for the human mind to conceptualize: a colossal cloud so colossal that it surrounds the sun and eight planets while stretching trillions of kilometers into space.

The spherical envelope often known as the Oort cloud is virtually invisible. The individual particles are so thinly distributed and thus far from the sunshine of any star, including the Sun, that astronomers simply cannot see the cloud, although it envelops us like a blanket.

It's also theoretical. Astronomers conclude that the Oort cloud exists since it is the one logical explanation for the arrival of a certain class of comets that sporadically visit our solar system. It seems that the cloud is basically an enormous reservoir could host billions of icy celestial bodies.

Two of those bodies will fly past Earth in the times leading as much as Halloween. Tsuchinshan ATLASalso often known as Comet C/2023 A3, will likely be at its brightest and certain visible to the naked eye for per week or two after October 12, the day it’s closest to Earth – just look in only after sunset the western sky. As the times pass, the comet becomes fainter and moves higher within the sky.

The second comet, C/2024 S1 (ATLAS)just discovered on September twenty seventh, needs to be visible around the top of October. The comet will make its closest approach to Earth on October twenty fourth – look deep into the eastern sky just before sunrise. Then, after orbiting the sun, the comet could reappear within the western night sky shortly before Halloween. However, it is feasible that every one or a part of it’s going to disintegrate, as sometimes happens when comets pass by the sun – and this one will come inside 1,000,000 miles (1.6 million kilometers) of our star.

As a planetary astronomerI'm particularly interested by the Oort Cloud and the icy bodies that inhabit it. The inhabitants of the cloud might be a reason for the emergence of life on Earth; When these icy bodies crashed onto our planet eons ago, they might have provided supplies a minimum of a number of the water that every one life requires. At the identical time, these same objects pose an ever-present threat to the continued existence of the Earth – and our survival.

billion comets

When an Oort cloud object finds its way into the inner solar system, its ice evaporates. This process creates a tail of debris that becomes visible as a comet.

Some of those bodies, often known as long-period cometshave orbits of a whole bunch, 1000’s and even tens of millions of years, like Tsuchinshan ATLAS. This is different from the so-called short-period cometswhich don’t visit the Oort cloud and have comparatively fast orbits. Halley's cometOne of those is planet Earth, which orbits the solar system and orbits the sun roughly every 76 years.

The twentieth century Dutch astronomer Jan Oort was fascinated by long-period comets and wrote a paper about it in 1950. He found that about 20 of the comets had a mean distance of greater than 10,000 astronomical units from the Sun. That was amazing; Just one AU is the Earth's distance from the Sun about 93 million miles. Multiply 93 million by 10,000 and also you'll find that these comets come from over a trillion miles away. What's more, Oort says, they weren't necessarily the outermost objects within the cloud.

Almost 75 years after Oort's paper, astronomers still cannot directly image this a part of space. However, they estimate that the Oort Cloud extends as much as 10 trillion miles from the Sun, which is sort of half that Next to Centaurithe closest star.

The long-period comets spend most of their time at these vast distances, making only short and quick visits near the Sun as they arrive from all directions. Oort speculated that the cloud contained 100 billion of those icy objects. There may be as many as these Number of stars in our galaxy.

How did they get there? Oort suspected and modern simulations have confirmed that these icy bodies can have originally formed nearby Jupiter, the most important planet within the solar system. These objects' orbits across the Sun can have been disrupted by Jupiter, much like what is usually the case with NASA spacecraft heading to destinations from Saturn to Pluto swung by the enormous planet to hurry up their journey out.

Some of those objects would have permanently escaped the solar system and grow to be interstellar objects. But others would have ended up with orbits like those of long-period comets.

Threats to Earth

Long-period comets represent a selected potential threat to the Earth. Because they’re thus far from our Sun, their orbits are easily altered by the gravity of other stars. This signifies that scientists do not know when or where any of those animals will appear until they suddenly do. At this point it is normally closer than Jupiter and moving quickly, at speeds of tens of 1000’s of miles per hour. In fact, the fictional comet that doomed Earth within the film is “Don't look up” got here from the Oort cloud.

New comets are continuously being discovered from the Oort Cloud, in recent times a couple of dozen per yr. The likelihood that considered one of them will collide with Earth is amazingly small. But it is feasible. The recent success of NASA's DART missionthat modified the orbit of a small asteroid shows a plausible approach to defending against these small bodies. But this mission was developed after years of studying its goal. A comet from the Oort cloud may not provide that much time – perhaps just months, weeks and even days.

Or no time in any respect. 'OumuamuaThe strange little object that visited our solar system in 2017 was discovered not before, but after its closest approach to Earth. Although 'Oumuamua is an interstellar object and doesn’t come from the Oort cloud, the suggestion still holds; One of those objects could sneak up on us and the Earth could be defenseless.

One approach to prepare for these objects is to raised understand their fundamental properties, including their size and composition. To this end, my colleagues and I are working on characterizing latest long-period comets. The largest known Bernardinelli–Bernsteindiscovered just three years ago, is about 75 miles (120 kilometers) in diameter. Most known comets are much smaller, from one to a number of miles, and a few smaller ones are too faint for us to see. But newer telescopes are helping. In particular, the decades-long Ruby Observatory Legacy Overview of Space and Timelaunching in 2025, could double the list of known Oort cloud comets, which currently stands at about 4,500.

The unpredictability of those objects makes them a difficult goal for spacecraft, however the European Space Agency is preparing a mission to do exactly that: Comet interceptor. With a launch planned for 2029, the probe will park in space until an acceptable goal emerges from the Oort cloud. Studying considered one of these ancient and pristine objects could provide scientists with clues concerning the origins of the solar system.

As for the comets which are now near Earth, it's okay to look up. Unlike the comet within the DiCaprio film, these two won’t crash into Earth. The closest Tsuchinshan ATLAS will reach us is about 44 million miles (70 million kilometers); C/2024 S1 (ATLAS), about 80 million miles (130 million kilometers). Sounds like an extended shot, but in space it's a near miss.

How to get a ticket:

Starting in 2024, you’ll only give you the chance to pay for BART with a Clipper card – either a plastic version or a digital version in your phone or smartwatch.

• Buy a card on the BART station. Cards can be found from vending machines at each station. You pay $3 for the cardboard, along with the loaded fare.

• Buy a card prematurely. You can order a prepaid ticket through ClipperCard.com and have it mailed to you. Expect the cardboard to take about 10 days to reach.

• Set up a digital account. You can find Clipper within the Transit section of Apple Wallet or Google Pay under Discover > Ride Transit. Clipper website provides more information in regards to the phone/watch option.

How to make use of it:

At the ticket counter resulting in the boarding area, hold your card or phone or watch near the scanner circle marked “Tag Here”. Do the identical at the opposite end before leaving the station.

BART from SFO:

There is a BART station on the departure/ticket level of the San Francisco Airport International Terminal. Walk or take the free AirTrain to the Garage G/BART Station stop.

If you’ll San Francisco, take either the northbound line – yellow (destination Antioch or Bay Point) or red (destination Richmond). The ride to San Francisco takes about half-hour and costs about $10.50 for an adult.

If your destination is on the east side of the bay, beyond the last stop in San Francisco, you will have to ascertain the map to see if you should stay on the Yellow or Red Line, or transfer to the Blue or Green Line at a station further up the road.

The only station south of the airport is Millbrae, which can be served by the red line (until 9 p.m.) and the yellow line. There you may Transfer to Caltrainwhich runs between San Francisco and San Jose (plus a number of day by day trains to Gilroy). Caltrain also accepts Clipper payments. Note that Caltrain's terminus in San Francisco is within the China Basin area, a few mile from the foremost tourist hotels.

BART from Oakland Airport:

The airport train station is situated between Terminals 1 and a couple of. A free shuttle train runs to the Coliseum station, where passengers should purchase a Clipper card at Platform 3 and transfer to a different line. The trip from the airport to the primary station in San Francisco takes about half-hour on two or three trains and costs about $12.

More about public transportation within the Bay Area

Can I take advantage of my Clipper card for other buses and trains?

Clipper is utilized by several other Bay Area transit agencies, including Caltrain, Muni, SamTrans, AC Transit and VTA.

What about cable cars? And ferries?

Yes for the cable cars which can be a part of the Muni system; the conductor has a handheld scanner to read the tickets. Yes for the Golden Gate Ferry, which matches to destinations in Marin County and Angel Island, and for the San Francisco Bay Ferry to the East Bay. No for the boat to Alcatraz, which is a concession of the National Park Service.

Can my whole party use a card?

Each person aged 4 and over needs a card, but multiple digital accounts might be arrange on one phone.

Can I get Clipper cards at a reduction? for the youngsters and seniors in my travel group?

To obtain a Clipper card that accepts youth (5-18 years) or senior (65+) fares, you could submit Proof of age eligibility by uploading documents whenever you order a card online. The youth rate is 50% cheaper, the senior rate 62.5% cheaper. In the Bay Area, you may upload the document to a designated transit office or stop by a staffed kiosk and buy a reduction card there.

Can I get a refund? the remaining balance on my card at the tip of my trip?

If you registered your card at ClipperCard.com, you may request a refund minus a $5 fee.

I actually have a BART paper ticket from a previous visit. Can I take advantage of it?

No. BART has stopped using paper tickets in 2023.

Does BART operate 24 hours a day?

On weekdays the trains run from 5 a.m. to midnightThe red and green lines shall be closed at 9 p.m. Service will begin at 6 a.m. on Saturday and eight a.m. on Sunday.

Is BART underground or above ground?

It's about half and half. The San Francisco stations from Glen Park to Embarcadero are underground, as are those in downtown Oakland. Between San Francisco and Oakland, trains run in 3½ miles of underwater tunnels.

Originally published: September 16, 2024 at 1:53 p.m.

Before seeing Half Dome, Yosemite Falls, giant sequoias, or other breathtaking attractions, Bridalveil Fall is the primary stop for hundreds of thousands of tourists when entering Yosemite National Park.

But for generations, the amenities at the bottom of the thundering, 620-foot waterfall on the western fringe of Yosemite Valley have been a bitter disappointment: fetid Sixties-era pit toilets, crumbling asphalt paths, a crowded dirt car parking zone and narrow, slippery paths.

But now it's all a past memory. Crews accomplished a $19.3 million renovation, constructing a bigger car parking zone, modern flush toilets, interpretive signs, commentary decks, boardwalks and wider trails with more accessible amenities in a classic Nineteen Thirties national park form of granite and wood.

Both the falls and the brand new “welcome center” were funded with federal money and supplemented by $12.2 million in private donations from the Yosemite Conservancy, a San Francisco-based nonprofit group that has worked for years to enhance park facilities contributes.

“Yosemite is a world-class destination,” said Frank Dean, the preserve’s president and a former Yosemite ranger. “But it gets a lot of traffic so things tend to get worn out. You want to make a good first impression and do it well. The park just needs a little care sometimes.”

At Bridalveil Fall, construction crews expanded the car parking zone by 24 spaces for 80 cars. The infamous four-stall composting toilets were demolished and replaced with 14 flush toilets in a contemporary constructing.

A brand new meeting, viewing and orientation area was built near the toilets. It includes benches and signs describing the realm's history, wildlife and geology. There are pet-safe trash and recycling receptacles, in addition to rerouted loop trails with two viewing platforms as a substitute of 1 near the bottom of the falls.

The work was accomplished in November. But as a consequence of the winter snow, many visitors only discover it for the primary time when spring arrives.

“It's spectacular,” joked Walnut Creek resident Susan Codeglia, beaming after ending a hike to the falls Tuesday afternoon. “If there was a drinking game every time someone said 'Wow,' we'd all be drunk.”

She was joined by her sister-in-law, Harriet Codeglia of Groveland, a former Mountain View human resources manager who moved to the Sierra after retirement.

“It's perfect. It's fabulous,” she said. “It was treacherous. The paths were slippery. I used to be here when people fell. It's easier to access now. And so well thought out, like the whole lot within the rocks and trees is integrated.”

Bridalveil Fall shouldn’t be as high as Yosemite Falls – which is 4 times higher. But it’s remarkable in its own right, taller than the Washington Monument, 3 times taller than Niagara Falls, and one in every of the few waterfalls in Yosemite Valley that flows year-round, no matter whether California is experiencing a drought or not – the swirling mists Waterfalls often create rainbows within the afternoon.

It was named in 1856 by Warren Baer, ​​editor of the Democratic newspaper Mariposa, who described the picturesque cascades as stuffed with “large folds, of the finest texture, purest white, and fringed with silver fleece or silk silk” like a bride's veil.

“Bridalveil Fall is one of the park’s iconic attractions,” said Scott Gediman, a Yosemite spokesman. “There’s a lot of history here.”

President Teddy Roosevelt camped near the bottom of the falls with Sierra Club founder John Muir during a visit in 1903. The two sat across the campfire until late into the night.

The other big recent addition to Yosemite this spring is the Welcome Center. The $12.2 million facility, in-built a former sporting goods store in Yosemite Village, is meant to supply an introduction to the park for lots of the 4.5 million individuals who come from world wide annually.

Yosemite's first visitor center, a country stone constructing, was in-built 1925 in Yosemite Village. Another was built round the corner in 1966. The original constructing became the park's museum, now displaying Native American artifacts, paintings, and images. The 1966 constructing is now called the Exploration Center and houses exhibitions on history, geology, plants, wildlife and cultural heritage.

For many years, you would drive up and park there, then walk in, confer with rangers, ask questions on mountaineering, camping or other topics, pick up maps and learn in regards to the geology, plants, animals and human history of the famous 748,000-acre park.

However, these parking spaces were removed when the park introduced a shuttle bus system within the Nineteen Seventies to accommodate crowds and traffic. It was only a half-mile walk from the essential car parking zone in Yosemite Valley, hidden amongst groves of trees, shops, worker housing, and park offices.

The recent Welcome Center is situated right next to the car parking zone. It shows visitors which roads and campgrounds are open, learn how to protect their food from bears, where to bike or hike, and other essential details. Since the ability opened several months ago, visitor contacts with rangers have increased by 25%.

“People say, 'I'm here for a day, or two hours, or four hours.' What can I do?” said Adonia Ripple, director of Yosemite operations for the Yosemite Conservancy. “This helps them discover a ranger – a flat hat – that they’ll ask. Before, the old visitor center was hidden and hard to search out. “

Including the 2 recent projects, the Yosemite Conservancy has committed $162 million since 2006 to renovate Yosemite Falls, Tunnel View, Olmstead Point, Mariposa Grove and other iconic park locations.

“You don’t want tired, underserved facilities or long lines for the restrooms,” Dean said. “You want to make sure the experience is really up there, so the accommodations match the landscape.”