字幕列表 影片播放 列印英文字幕 Scientists claim that the earth's magnetic poles will reverse within the next few thousand years. So why does that happen? And what exactly does it mean for us? Hey guys, Tara here for Dnews - and something that's always fascinated me, is the earth's magnetic field. Maybe it's because we can't see it with our own eyes, so it's this elusive thing that we pretty much assume to be constant. Believe it or not though, the north and south poles we know today, weren't always that way. 786,000 years ago - the earth's magnetic field flipped - and it's remained constant ever since. But before that happened, south was actually north - and what we now know as north, was south. According to scientists, every half million years or so - the earth's dipole magnetic field, which you can imagine like a bar magnet with a north end and a south end, starts to weaken, before eventually reversing completely. No one is really sure why it happens, but it's thought to be caused by changes in the fluid portion of the earth's iron core. Up until recently, scientists presumed this reversal process took a few thousand years - but new evidence suggests that the most recent major reversal 786,000 years ago - actually happened in less than 100 years - roughly the span of a single lifetime. Obviously, flips like this have occurred several times throughout Earth's history. But the next one, scientists say, may happen within the next few thousand years. New evidence indicates that the intensity of the Earth's magnetic field is decreasing at a rate 10 times faster than normal, leading many geophysicists to believe that we're on the brink of another reversal. So what would happen if that did occur? Would there be any noticeable changes? Well, the good news is - there are no documented catastrophes associated with past reversals. So you shouldn't expect the human race to immediately die out. But that doesn't mean nothing bad could happen. A magnetic reversal would almost surely wreak havoc on our electrical grid, which could potentially bring it down. It would also make us vulnerable to energetic particles from the sun and cosmic rays - both of which can cause genetic mutations. And that could happen before the reversal even takes place. Like I described earlier, there's a period prior to reversals where the magnetic field gets progressively weaker, and the genetic mutations that arise from that, could potentially increase cancer rates. So the longer it takes for that reversal process to complete, the more harmful it would be to us. Also worth mentioning, is the fact that even though the last reversal only took 100 years - it was preceded by a period of magnetic instability that spanned over 6,000 years. Meaning if the next reversal happens within a few thousand years, we could start seeing the effects of it - very soon. Kinda scary to think about it. But at the same time - it's not likely that any of this will affect us in our lifetime. So, before you start packing up your family and moving off the grid, Doomsday Preppers-style, just remember that. It's probably not worth it. What do you guys think though, are you worried about this? You can lay it all out for us in the comments right down there - or if you wanna get in touch with me on Twitter, you can do so at @TaraLongest. That's it for me, but as always - thank you guys for watching.