Hi, this is an interesting question. Given that you asked this question, you probably already know a little bit about the magnetic field but I will still start at the beginning.

There is evidence that the magnetic field has been around for nearly 3500 Million Years; that is three fourths of the entire age of the Earth so it is very unlikely that the magnetic field stops in the near future. O.K. But even if it is unlikely, what would happen if it (the magnetic field) got lost? One important feature of the magnetic field of the Earth is that it causes certain particles and rays to move around the Earth instead reaching the atmosphere. If the magnetic field was weaker or not there at all, the Earth would receive much more intense radiation from the sun and this radiation would likely be harmful to us humans and other lifeforms. These “solar winds” could also affect our atmosphere . Over time our atmosphere loses gases to space. So in the past, there was a “thicker” atmosphere and over time more and more gases got lost and the atmosphere became thinner. Some people think that this loss was very important in forming the atmosphere as it is today. In the future, the atmosphere will become even thinner and thinner until eventually the oceans will evaporate and life will become more and more difficult. This process happens over VERY long times (many millions of years). Now if the magnetic field was lost and more “solar winds” reached the atmosphere, the atmosphere could be lost faster however, it would still take a long time for all of it to be gone.

In summary, if the magnetic field weakened or vanished, the Earth would be less protected against harmful solar radiation and would also likely lose its atmosphere faster than it does today.

It will not be a good thing for our planet. The magnetic field helps shield us from things in space (like rocks and solar energy) that come too close. If it disappears it will make space rocks more likely to collide with us, and harmful radiation from the Sun will not be deflected away and could actually strip the ozone layer away. The ozone layer is what protects us from harmful UV rays. So you can see that it is not something we want to see. However, I personally don't think you have to worry too much about it, as the likelihood of that happening is quite slim. Unfortunately, I don't know if humans can cause the magnetic field to disappear. I want to say no, but I'm not really sure. I hope another scientist answers this part.

Just a side note, the thickness of the magnetic field is not the same everywhere. Some places have it thinner, others have it thicker. I don't know if you've heard of them, but the areas where the magnetic field is thinnest (near the north and south poles) are places where we see "auroras". These are spectacular show of lights caused by solar radiation interacting with our atmosphere because of thin magnetic shield. If you don't know what they look like I suggest asking your teacher to show some pictures. They are really cool!

If earth lost its magnetic field, many means of navigation would fail, including the ways in which many birds and marine mammals locate where they are and where they need to go, would fail. Whether these animals could use other queues (such as the sun's position in the sky) remains to be seen. Many human navigation systems would also fail (such as anything using a compass).

There is no reasonable way that humans could alter the Earth's magnetic field. The Earth's magnetic field is produced by the Earth's liquid outer core, which is more than 3,000 km into the Earth. We can't get down there to do anything.