What if The Sun Suddenly Stopped Burning? | Unveiled - video Dailymotion

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00:00 The sun is crucial for life on Earth. It provides plants with energy, warms the planet,

00:05 and drives the water cycle. But, if for some reason we suddenly lost that source of heat,

00:11 would we be doomed to perish? For how long could we survive?

00:15 This is Unveiled, and today we're answering the extraordinary question;

00:19 what if the sun suddenly stopped burning?

00:22 Do you need the big questions answered? Are you constantly curious? Then why not subscribe to

00:28 Unveiled for more clips like this one? And ring the bell for more thought-provoking content!

00:32 The existence of stars is something that we perhaps take for granted.

00:37 Look up into the sky on a clear night, and there are endless twinkling orbs. And, in reality,

00:43 they only ever represent just a tiny, tiny fraction of what's in the universe as a whole.

00:48 Over the years, our knowledge of them has improved, and especially in recent times.

00:53 So much so, that we can't imagine what life would be like without our closest one, the sun.

00:59 And, spoiler alert, it isn't good.

01:02 There are between 100 to 400 billion stars in our galaxy, the Milky Way. Stars are then classified

01:08 into various types based on their spectral characteristics, temperature, and luminosity.

01:14 A key factor in these features is mass, which also determines how long a star lives for,

01:20 and how it eventually dies. All stars begin the same way, though, as vast nebulae of dust and gas

01:26 in space. The particles in these gas clouds are gravitationally attracted to one another,

01:32 creating a domino effect of collisions. As everything clumps together, over time,

01:37 a proto-star emerges, and once its mass and temperature reach a critical threshold,

01:42 nuclear fusion begins, marking the birth of a new star. At this point, the stars enter the

01:49 main sequence phase, the most stable and prolonged period in their life cycle. And this is where our

01:54 sun currently resides. It's a reasonably average star, at a reasonably common point in its timeline.

02:01 During the main sequence, stars consume the majority of their hydrogen fuel.

02:05 The dynamics within a star are dominated by two rival forces. The first is gravity,

02:10 which works to pull the star inward into collapse. The second is the outward pressure

02:15 produced by nuclear reactions within the core of the star. During the main sequence phase,

02:20 these forces more or less balance each other out, which is what results in the stability we see.

02:26 But, still, nothing lasts forever. Not even stars. And the total lifespan depends largely on mass.

02:32 The larger the star, the faster it burns through its fuel, and the shorter its lifetime will be.

02:38 In fact, the most massive stars live for only a few million years - an exceedingly short time

02:43 compared to most others. On the other end of the spectrum, the smallest main sequence stars,

02:48 red dwarfs, are thought to live for tens of billions to trillions of years. For perspective,

02:54 our universe is just 13.8 billion years old, so many will live for longer than the universe has

03:00 been here so far. Our sun, in particular, is what's known as a G-type main sequence star,

03:06 aka a yellow dwarf, and is expected to shine for around ten billion years total. It's currently

03:13 4.6 billion years old. In reality, then, it will one day stop burning. But that event won't be

03:19 sudden. And it also won't be for a long time yet. Hydrogen is the primary fuel for all stars,

03:25 including our sun, which is burned up through nuclear fusion. In this process, atomic nuclei

03:30 combine to form a new, heavier nucleus - specifically helium - which builds up in the

03:35 star's core. As hydrogen is depleted, this core contracts and heats up, and hydrogen fusion in

03:42 the star's outer shell accelerates, leading it to expand into a red giant. This is what will happen

03:48 to our sun. In other, more massive stars, fusion also produces even heavier elements, such as iron.

03:54 However, the fusion of iron actually consumes more energy than it produces, so massive stars

04:00 amass an inert, iron core deep in their centre, which slowly grows over time… until eventually,

04:06 the effects of fusion are no longer able to counteract gravity. Once this happens,

04:11 the massive star is doomed, collapsing inward. It's tricky science to envisage, but the result

04:17 is something that we can all picture. One of the most violent explosions known in the universe,

04:22 what we call a supernova. All that's left behind after a supernova is either a small and dense

04:28 neutron star, or a black hole, which will gradually absorb anything unfortunate enough to get too

04:35 close. But again, in reality, our sun isn't massive enough to go supernova. It will become

04:41 a red giant, instead. We have about five billion years until this happens. As it expands, the sun

04:47 will consume the entire inner solar system, most likely including the Earth. It will spend up to a

04:52 billion years in this period, enduring a prolonged death. Eventually, our sun will completely lose

04:58 its outer layers and shrink into a white dwarf star, similar in size to that of our home planet.

05:04 Those lost outer layers will then go on to form a planetary nebula, much like the material it

05:10 was originally formed out of. Together with other material in the interstellar medium,

05:14 the remains of our sun may eventually birth a new star, continuing the cycle.

05:19 So, all of that is what will happen if the sun stops burning due to natural causes. But what,

05:24 then, if it just suddenly and mysteriously stopped burning, billions of years before its due date?

05:30 If by "stop burning" we mean "stops nuclear fusion reactions", then there would actually be

05:35 very few noticeable effects, on human timescales. We would cease to see neutrino emissions,

05:40 which are natural products of nuclear fusion. But neutrinos rarely interact with anything they pass

05:45 by. There are approximately 100 billion neutrinos from the sun passing through your thumbnail every

05:51 second, so the loss of these would hardly be a significant change. In the very long run, though,

05:56 life on Earth would have a major problem. The next few million years would see the sun contract,

06:02 causing its temperature to increase. Ultimately, once the sun reached about one-hundredth of its

06:07 current size, the contraction would come to a standstill, and the sun would be considered

06:11 a white dwarf. While it would be hotter than the sun is now, it would be significantly smaller.

06:16 It would also cool over time. The so-called "Goldilocks Zone" for habitable planets around

06:22 it would have been distorted beyond recognition, and Earth would certainly no longer dwell within

06:27 it. By the time any of that became an issue, though, you definitely wouldn't be around to care.

06:32 So, if the sun switching off is a fear on your list, then feel free to cross it off.

06:38 But what about in another alternate scenario, where all of the sun's heat just immediately

06:42 vanishes, and it does turn off completely? Ignoring the impossibility of such a thing

06:47 ever actually happening, this would really be quite terrifying. All plants, which convert sunlight

06:53 into energy through photosynthesis, would die out. For most plants, this would take just a handful

06:58 of weeks. But some trees might be able to last a few decades before succumbing. And once the plants

07:04 go, animals will soon follow, on both short and long-term scales. Within a week, Earth's surface

07:10 would reach average temperatures of below negative five degrees Fahrenheit. Then, after a year,

07:16 it could be as low as negative ninety-four degrees. By this point, the oceans will have

07:20 completely frozen over, causing the deep seas beneath them to become the new, warmest places

07:25 on Earth due to the ice sheet's insulation. After a few million years, the temperature on Earth would

07:30 bottom out at negative four hundred degrees - only sixty degrees higher than absolute zero.

07:36 The only places hospitable enough for humans to live would be in submarines at the very deepest

07:41 depths of the ocean. Or, in areas of high volcanic activity where we could utilise geothermal energy

07:47 to keep warm. If this were possible, humans could live off volcanic energy for thousands of years.

07:53 But, of course, between now and then, our species will have endured an untold amount of suffering

07:58 and hardship. Ultimately, it's extremely unlikely that we, or perhaps anything else, would survive.

08:04 This is an incredibly bleak scenario, and life on a post's on Earth would not last long at all.

08:11 Fortunately for us, the laws of physics say that it's also a complete impossibility.

08:16 So, we can all rest assured that that orange, glowing, life-enabling orb in the sky will keep

08:22 rising for the remainder of our lifetimes, and then a few billion years on top of that.

08:27 But, otherwise, that's what would happen if the sun suddenly stopped burning.

08:32 What do you think? Is there anything we missed? Let us know in the comments,

08:36 check out these other clips from Unveiled, and make sure you subscribe and ring the bell

08:40 for our latest content.

What if The Sun Suddenly Stopped Burning? | Unveiled

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