I know some animals, mostly birds, use the magnetic field of the Earth as an aid in navigation, but am not sure if it has other important uses. If, by chance, the Earth did not have this magnetic field, would life have evolved any differently? Are there things that wouldn’t have happened, like maybe it affects the rotation of the Earth, or the weather, or something?
Basically I’m asking, what does it actually do?
If not for the Earth’s magnetic field, there would probably be no life at all. One of its important tasks is to shield the Earth from the solar wind, which would strip the Earth of much of its atmosphere. Earth would become much like Mars, which has no magnetic field and a very thin atmosphere.
Huh. Okay then. Why are we looking for life on Mars if it’s impossible without a magnetic field?
They are not looking for life on Mars, they don’t have the equipment - they are looking for the conditions that may have supported life. Also, while Mars no longer has a magnetic field, this may not have always been the case. And Mars is a long way out from Earth - the Solar Wind is less intense out there (but it has stripped most of the Martian Atmosphere away).
Si
Life as you commonly think of it **may **be impossible without a magnetic field to shield it. But in recent times we’ve discovered life almost everywhere on earth we’ve looked - kilometres deep underground, under the antarctic ice, in boiling hot water deep in the ocean, you name it. Places like that would be shielded from solar wind.
Isn’t the earth’s magnetic field a result of the inner molten core?
Isn’t it tied in with plate tectonics, vis a vis the crust floating on the mantle?
Yes. Mars is smaller and has less iron, and the core has now solidified. It has not had a Magnetosphere for 4 billion years.
Si
Not only that, surely, but the Earth’s surface would be bombarded with a lot more radiation than it is, both from the Solar wind and cosmic rays. Currently, the magnetic field serves to deflect a lot of the radiation, which is largely charged particles many of which get trapped in the van Allen belts.
life may exist there but it might not have evolved there. it might have needed the surface to evolve.
Not necessarily; Venus has a much thicker atmosphere than Earth yet doesn’t have a magnetic field. However, this resulted in the loss of lower molecular weight molecules like water, although I don’t know how relevant this would be to Earth, which is much cooler and has very little water vapor in the upper atmosphere. Radiation would still be a problem, but I imagine the presence of an atmosphere blocks some of it (gamma rays, x-rays and ultraviolet aren’t influenced by magnetic fields and energetic cosmic rays can penetrate Earth’s magnetic field).
Also, Earth’s magnetic field periodically weakens in reversals and there is no reliable evidence of adverse effects on life occurred during these periods (which have happened hundreds of times); one possibility is that the solar wind is enough to induce a magnetic field strong enough to prevent harmful radiation from reaching the surface (it should also be noted that this is only referring to the dipole component; weaker fields still exist):
Loss of atmosphere due to solar wind isn’t an instantaneous thing-- It takes a while. That’s why Earth doesn’t lose it all during the occasional field reversal, and why Mars seems to have had a significant atmosphere earlier in its history.
Even if we could get past the solar winds sweeping away our atmosphere, we wouldn’t have any magnets, thus no electricity.
(I’m going off of my memories of freshmen science class nearly 30 years ago. I could be wrong here.)
You are. Artificial magnets and magnetic fields aren’t dependent on the Earth’s magnetic field at all.
Permanent magnets can and do exist independently of the earth’s magnetic field.
Even though “how do magnets work?” was what originally inspired my train of thought to ask this question, I did know that bar magnetism has nothing to do with the Earth’s magnetic field.
Not only that, but from what I can tell based off a quick google search, natural lodestone magnets don’t depend on the earth’s field to form. Most often they’re induced via lightning strikes on magnetite deposits.
Even with no naturally occurring magnets at all, we could still produce electromagnets using electricity generated by chemical means. We’ve discovered a thousand year old battery: Baghdad Battery - Wikipedia it’ll probably delay our technology by several centuries though.
I wonder what else we’re missing out on because they don’t occur naturally? Magnetic monopoles, hmm?
Well, this wouldn’t work:
OK. I believe you, but perhaps you (or somebody) can help refresh my memory.
I vaguely remember that the magnetic rock got to be that way because the mineral (or whatever the hell it was) got to be that way because the Earth’s magnetic feild had permeated it for so long that the the magnetic poles inside the mineral had aligned, thus causing it to be magnetic.
What am I not remembering right?
Yes, it’s true that some lodestone was naturally magnetized, and was at first the only source for magnets that could be used for making compasses. But they weren’t nearly strong enough for useful electric motors, so we make our own permanent magnets these days by exposing magnetizable materials to very strong electromagnets.
If we lived on an earth with no magnetic field, it’s possible it might have taken us a bit longer to discover magnetism, but we would have figured it out eventually.