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The Earth sits comfortably in its orbit
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tilted on its axis at 23 degrees.
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Knock the planet over -
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and it wouldn't be the Earth as you know it.
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This is WHAT IF,
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and here's what would happen
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if the Earth's axis was tilted by 90 degrees.
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Only two planets in the Solar System lie on their sides -
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Uranus and the dwarf planet Pluto.
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Now, if something took the Earth off its stand,
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the blue planet would have no chance
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of developing any complex life on its surface.
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But let's start at the beginning.
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This axial tilt, or obliquity,
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is what drives the seasons here on Earth.
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Before the collision that created the Moon,
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the Earth's axis was slowly wobbling around
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somewhere between 0 and 85 degrees.
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Then, our newly formed Moon stabilized it.
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But if that collision happened at a different time,
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things would turn out very different here on Earth.
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It would be a strange new world.
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As the Earth made its way through orbit,
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its poles would be pointing straight towards the Sun.
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One hemisphere would be shrouded in darkness
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for six months straight,
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while the other would be getting cooked
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by the blazing sunlight.
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One day on Earth would last a whole year.
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At the North Pole, the daytime temperatures
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would rise to a broiling 50°C (120°F).
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A day at the South Pole would be even worse.
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Because the South Pole would be located
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away from climate-controlling ocean currents,
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it would heat up to an almost boiling 80°C (176°F).
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The poles would soak up so much heat from the Sun,
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that they wouldn't even freeze
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during the six-month-long night.
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You wouldn't recognize the steaming equatorial tropics.
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With a 90-degree axial tilt,
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part of the equator would stay encased in ice all year round.
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At some point in this Earth's existence,
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our continents would get clumped together around one of the poles.
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Inland temperatures in the daytime would get truly hellish -
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reaching the boiling temperature of water.
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Clouds could help the situation and
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not let all the water vapor off the planet.
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But you wouldn't know.
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You wouldn't stick around that long.
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In this scorching heat,
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the best-case scenario would see
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just a few kinds of bacteria survive.
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Those bacteria might evolve
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into more complex life forms,
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but they wouldn't be anywhere close
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to how complex we turned out to be.
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The reason would be a lack of oxygen.
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Green plants would be having a hard time surviving
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during the six months of complete darkness.
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They'd drop their seeds at nightfall
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to grow after sunrise.
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Interestingly enough,
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if the Earth was 60 million km (40 million miles)
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further away from the Sun,
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a 90-degree axial tilt wouldn't be so bad.
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The temperatures at the poles
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would never raise above 46°C (115°F) during the day.
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The coldest it would get at night would be 3°C (37°F).
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The only place covered with ice would be the highest mountains.
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So you see, simply orbiting a star in the habitable zone
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doesn't mean that a planet is actually capable of sustaining life.
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We're the lucky ones living here on Earth.
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Maybe one day we'll discover another exoplanet,
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just like our home.
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But that's a story for another WHAT IF.
