A total solar eclipse will cross the US on April 8. Here's what time ...

A rare total solar eclipse will sweep across the Pacific Ocean, through Mexico, the United States and Canada on April 8 (North American time).

The phenomenon occurs when the Moon passes between the Sun and Earth, completely blocking the face of the Sun.

Unfortunately, eclipse chasers in Australia won't be able to see the sky darken. However, NASA will live-stream the event for those outside the US.

Here are a few things to know about tomorrow's North American eclipse, including why one Canadian city has declared a state of emergency in the lead-up to the celestial event.

What happens during a total solar eclipse?

The Sun's corona becomes visible during totality.(Getty Images: Tristan Savatier)

Total eclipses happen when the Moon passes directly in front of the Sun, casting a shadow on Earth.

This is called the path of totality.

The sky darkens as if it were dusk or dawn, and nocturnal animals are known to wake up, believing night has arrived.

There are several stages in a total solar eclipse:

1.Partial eclipse begins: The Moon starts to become visible over the Sun's disc. It looks like the Moon has taken a bite out of the Sun, hence the crescent shape. This phase generally lasts 70 to 80 minutes.2.Baily's beads and diamond ring: The Moon covers the entire disc of the Sun, and observers are now within the Moon's umbra, the darkest part of the Moon's shadow. A diamond ring effect is visible, as are Baily's beads (the effect occurs when light rays from the Sun stream through the valleys along the Moon's horizon).3.Totality reached: The Moon completely covers the disc of the Sun. In places along the path of totality, people will be able to view the Sun's corona — the star's outer atmosphere — which is typically not visible because of solar brightness.4.Totality ends: The Moon starts moving away and the Sun begins to reappear. The diamond ring and Baily's beads may be observed again.5.Partial eclipse ends: The Moon completely leaves the face of the Sun.

Source: NASA

Solar physicist and eclipse chaser Ryan Milligan says it's a very primal, visceral feeling to see the Sun disappear in the middle of the day.

"It's not something your brain is accustomed to processing," Dr Milligan told ABC News Mornings.

"It's that kind of adrenaline rush, to have this fleeting experience, when the temperature drops, perhaps a few stars come out, the animals go to sleep, you're looking around trying to soak in this experience that only lasts for a couple of minutes."

Are all solar eclipses the same?

No, they're all very different.

"The part of the Sun's atmosphere, the corona you see during totality, can look very different, depending on what phase of the solar cycle we're in," Dr Milligan said.

"That can dictate how the corona is structured, the clouds of hydrogen gas and so on.

"Whether it's a sunrise eclipse, sunset, midday eclipse, it can have a dramatic effect, and where you are can change the experience of totality."

Where will the total solar eclipse be visible?

The eclipse will cross through North America, passing over parts of Mexico, the US, and Canada.

Thirteen US states will be along the path of totality. These are:

TexasOklahomaArkansasMissouriIllinoisKentuckyIndianaOhioPennsylvaniaNew YorkVermontNew HampshireMaine

The eclipse will then enter Canada in Southern Ontario, and continue through Quebec, New Brunswick, Prince Edward Island, and Nova Scotia.

The total solar eclipse will be visible along a narrow track stretching from Texas to Maine.(Supplied: NASA)

What time does the solar eclipse start?

Unfortunately, we won't be able to see the total solar eclipse from Australia.

But luckily, NASA will be live-streaming the eclipse from beginning to end.

The live stream will begin at 1pm North American Eastern Daylight Time (so, 3am AEST on Tuesday for Aussie viewers) and will last 3 hours.

If you're eager to get up early and watch the live stream, here's when the eclipse will start depending on where you live:

QLD, NSW, ACT, VIC, and Tasmania: Eclipse begins at 3:23am, reaching totality at 4:40am AESTNT and SA: Eclipse begins at 2:53am, reaching totality at 4:10am ACSTWA: Eclipse begins at 1:23am, reaching totality at 2:40am AWSTWhat is special about the 2024 US solar eclipse?

It will be wider than the total solar eclipse in August 2017.

According to NASA, during that eclipse the path of totality ranged from 100 kilometres to 114km wide.

But during this year's eclipse, it will range from 174km to 196km.

Dr Milligan said this year's eclipse would give a lot of people an opportunity to witness a rare celestial event.

"It goes over such a populated land mass, which makes it quite unique," he said.

"Last year, the path of totality just clipped the top of Australia, which is a very limited place on Earth where you could see the eclipse.

"So this year there is a huge difference in terms of viewing size."

And this year's total solar eclipse will also have a longer duration in totality — meaning the Sun will appear to be blacked out for longer.

The 2017 total solar eclipse's longest blackout period was 2 minutes and 42 seconds.

But this year's will be 4 minutes and 28 seconds.

Niagara Falls prepares for influx of eclipse tourists

Ahead of the total solar eclipse, Canada's Niagara region has declared a state of emergency as the city prepares for large crowds to descend on the area.

Because Niagara Falls is on the eclipse's path of totality, it's expected more than 1 million people will flock to the border city to observe the celestial event.

This is compared to the 14 million visitors who travel there during an entire year.

The region will be closing some facilities to keep traffic off the roads, with most schools also closed on April 8.

How often do total solar eclipses occur?

Total solar eclipses occur once every one to two years.

"But they are only visible from less than half a per cent of the Earth's surface," says American astrophysicist Fred Espanak.

The next total solar eclipse will grace the northern fringes of Greenland, Iceland, and Spain in 2026.

When was Australia's last total solar eclipse?

The last total solar eclipse in Australia was on April 20, 2023.

But the only place where the Sun was blocked out was in Exmouth, on the tip of the North West Cape in Western Australia.

The rest of the country only experienced a partial solar eclipse.

When is the next solar eclipse in Australia?

In four years.

Here's a timeline for those eager to experience a solar eclipse in person:

July 22, 2028: Totality will cross from the Kimberley, WA, through NT, south-west Qld, NSW and pass directly over SydneyNovember 25, 2030: Across SA, north-west NSW and southern QldJuly 13, 2037: Southern WA, southern NT, western Qld, passing directly over Brisbane and the Gold CoastDecember 26, 2038: Central WA, SA, and along the NSW and Victorian border