What If the Sun Got Bigger and Couldn't Stop?

It's a normal afternoon on your street, and the Sun starts to grow. Only a little at first, but you can feel it on your skin. The grass turns yellow, the birds go quiet, every lake and ocean starts to boil, and the sky turns white with steam. Then the trees catch fire by themselves, the roads glow, the ground melts and the air boils away into space. And it doesn't stop. You leave Earth and watch the Sun swallow Mercury, then Venus, then the small red dot where everyone you have ever known lived, until it is as wide as the biggest stars we know of. The readout on the left is how wide the Sun is compared with today, and how many Earths would fit across it. The one on the right is the temperature on Earth. The numbers follow a simple model: the Sun keeps the same surface temperature and just gets bigger, so the sunlight reaching Earth grows with the square of its size. The Sun today is about 1.4 million kilometres across and 150 million kilometres away. Just 10% more sunlight would, over time, be enough to boil away the oceans. Paper catches fire by itself at about 233°C, car tyres at around 400°C, and aluminium melts at 660°C. The Sun reaches Mercury's orbit when it is about 83 times wider than today, Venus at about 155 times, Earth at about 215 times, Mars at about 330, Jupiter at about 1,100 and Saturn at about 2,060, which is as big as the largest known stars. Some of it is not real. The Sun could never grow this fast; it is sped up from billions of years to six and a half minutes. Your street and your house would not survive long enough to see most of it, and nobody could breathe once the air was gone, so the view from space is a camera's view, not a person's. The planets are shown far closer together and larger than they really are so you can see them. And our real Sun will not grow as far as Saturn: it will probably stop somewhere around the orbit of Earth. This part is real. In about five billion years the Sun will run low on fuel and swell into a red giant. It will swallow Mercury and Venus, and maybe the Earth. Then it will shed its outer layers and shrink into a white dwarf about the size of the Earth, and slowly fade. 0:00 It won't stop growing 0:10 An ordinary afternoon 0:23 The Sun 0:37 You can feel it 0:53 The shade doesn't help 1:07 The birds go quiet 1:17 The hottest day ever 1:35 Every lake is boiling 1:54 Your house 2:06 Dry as paper 2:18 The trees catch fire 2:28 Your street is burning 2:46 It isn't slowing down 3:03 The roads glow 3:18 The air boils away 3:33 That was your home 3:48 Earth glows like a coal 4:04 Mercury is gone 4:22 Venus is gone 4:42 Earth 5:02 Mars, Jupiter, Saturn 5:24 As big as the biggest stars 5:38 Out of fuel 5:50 A white dwarf 6:03 Five billion years 6:17 Six and a half minutes Music: "A Dark Tranquility" by DEX 1200 and "Nascency" by Christoffer Moe Ditlevsen (Epidemic Sound) #whatif #science #sun #space #redgiant