All About Space - - The Last Days Of Earth -

2.3 bil­lion years

Earth’s mag­netic field shuts down

The freez­ing of Earth’s outer core shuts down Earth’s mag­netic field, with dras­tic con­se­quences for any re­main­ing life on the planet as there is noth­ing to de­flect the DNA-dam­ag­ing, po­ten­tially deadly cos­mic rays and so­lar wind. The lat­ter would also strip away any re­main­ing at­mos­phere, leav­ing the sur­face to­tally de­fence­less.

2.8 bil­lion years

En­tirety of Earth is scorch­ing hot

By this point Earth’s en­vi­ron­ment is hos­tile to any mul­ti­cel­lu­lar life, but when global tem­per­a­tures – even at the poles – reach an av­er­age of 147 de­grees Cel­sius (297 de­grees Fahren­heit), even the last re­main­ing uni­cel­lu­lar life on the planet – in iso­lated refuges such as high-al­ti­tude lakes or cold-trap caves – can no longer sur­vive.

3 bil­lion years Moon be­comes un­sta­ble and Earth’s poles be­come chaotic and ex­treme

The Moon has long been mov­ing away from Earth – at roughly four cen­time­tres (1.6 inches) a year – but this is the point at which it is suf­fi­ciently dis­tant to no longer ef­fec­tively in­flu­ence Earth’s ax­ial tilt, re­sult­ing in the planet’s true poles in­creas­ingly ‘wan­der­ing’ as its spin be­comes less sta­ble.

3.3 bil­lion years Mer­cury or Venus could col­lide with Earth

There is a one to two per cent chance that Jupiter’s long-term grav­i­ta­tional in­flu­ence on the in­ner So­lar Sys­tem makes Mer­cury’s or­bit so ec­cen­tric that the small in­ner world might col­lide with the gassy Venus or even come as far as Earth, crash into the Sun or be ejected from the So­lar Sys­tem en­tirely.

3.5 to 4.5 bil­lion years Sur­face heats to 1,130 de­grees Cel­sius (2,066 de­grees Fahren­heit)

Wa­ter vapour in Earth’s lower at­mos­phere in­creases to 40 per cent. This, com­bined with the Sun now be­ing 40 per cent brighter than in the 21st cen­tury, leads to a ram­pant run­away hot­house en­vi­ron­ment with sur­face tem­per­a­tures hot enough to melt rock. Es­sen­tially it’s a hot­ter ver­sion of today’s Venus.

7.5 bil­lion years Earth and Mars be­come tidally locked with an ex­pand­ing sub­giant Sun

Hav­ing one side of a planet con­stantly fac­ing the

Sun leads to more than just tem­per­a­ture dif­fer­ences be­tween the two sides; any re­main­ing at­mos­phere will nec­es­sar­ily move be­tween the light and dark faces, cre­at­ing storms and caus­ing se­ri­ous land­scape ero­sion – not good for con­tin­ued life in any form.

7.59 bil­lion years Moon falls to­wards Earth, breaking into de­bris that rains on it

Or­bital drag in the vicin­ity of the Sun’s ap­par­ent sur­face – the pho­to­sphere – re­duces the Moon’s or­bit un­til it reaches the point where the grav­ity hold­ing it to­gether is weaker than the tidal forces pulling it apart. Earth will again briefly have a ring of de­bris be­fore it falls down on the planet.

7.59 bil­lion years Earth falls into the Sun at red gi­ant phase

Reach­ing its max­i­mum size as a red gi­ant – a ra­dius 256 times its present-day value – the Sun swal­lows up Mer­cury and Venus, very likely Earth and pos­si­bly even Mars. On the plus side, by then Saturn’s moon Ti­tan will likely have the pre­cise sur­face tem­per­a­tures needed to sup­port life.

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