Vertical? The Earth’s Magnetic Field?!?!


Hi! Have you ever wondered about
the direction of the Earth’s magnetic field? Holding a compass it only seems logical
that the magnetic field is going that way. But what if I told you that it may be going… That way!? In this video I’ll test it in different ways
and explain the true direction. I will also reveal and use the most
valuable donation to my channel ever. No major hazards in this video, but do
be aware of the power of large sphere magnets. Keep their fragile poles away from anything magnetic. First indication of the direction is the way
a magnet dropped from a low height will have a strong tendency
to land facing south pole up. Even when released with the north pole facing up. By the way, through the video I’ll be using red to mark the north-pointing pole
and blue for the south-pointing pole. This drop test doesn’t tell
us much about direction and strength of the Earth’s magnetic field. But it does give us a hint: The compass isn’t telling the whole truth
about the direction of the magnetic field. The compass is balanced in a way
that makes it useful for horizontal navigation. If we want to know more about the
vertical direction of the magnetic field we need something meant for it. Such a vertical compass is known as a dip circle. I don’t own one, but I believe a
sphere magnet can be used as one too. Let me first mark the poles of
this 20 mm sphere magnet. If I place this marked magnet
on something smooth and level it can freely spin around and align
with the magnetic field of the Earth. I’ll use a mirror placed on top
of this old, wooden stand. It’s all wood with no ferromagnetic
metals messing with the magnet. Let me mark the mirror with north
and south so you can follow along. The mirror needs to be perfectly level
or the magnet will just roll off. I tried with a spirit level without any success. I ended up using something
else to level the mirror. Here’s a challenge for you: Balance a 50 mm bearing ball on a clean mirror. This level of leveling will do. Time for the test. If the magnetic field is horizontal,
the magnet should align like this. As a compass needle. But it doesn’t. No matter how many times I release it,
the magnet ends up with this strong tilt. The north pole is almost pointing
directly down into the mirror. Using a protractor placed parallel
with the north-south axis the inclination looks like… It’s a little difficult to tell. Maybe somewhere around 70 degrees. Let’s try with the bigger 50 mm magnet
donated by Magnetportal for my previous video. Not surprisingly, this ends up at the same angle. Still looks like around 70 degrees Though it isn’t really easy to tell with precision. It doesn’t tell us much about the
strength of the magnetic field either. Let’s get more scientific
and use a lab instrument that can show us the direction and also
the strength of the magnetic field with high precision. Not an easy task with a weak field but this is where the big donation comes in. I’m so lucky that one of my
subscribers works at Lake Shore and their new F71 Teslameter
should meet my crazy needs. Not only does it measure at a very wide
range of strengths using just one probe It does so at three axes at the same time. Finally, I can measure in the
3-dimensional world of magnetic fields. Can’t wait to see if this works,
so here we are in my kitchen again. In the way I’m holding the probe X-axis is up and down Y-axis is east-west and Z-axis is north-south. Let me find due north with the probe. Watch for the Y-axis to go close to 0. That’s close enough. The probe is
now pointing straight towards north. Notice how strong the vertical X-axis is
compared to the horizontal Z-axis. A clear sign of the magnetic field
being mostly vertical at my place. The Z-axis is what a compass follows. The values displayed are the average
for the last 200 milliseconds which isn’t useful for this project. Let’s choose another averaging window. An average over 10 seconds makes more sense
for measuring the Earth’s magnetic field. The values are still updated five times a second but will now display the average
of 10 seconds back in time. While the values settle in, I can
show you some other details. Not all touch-screens are a joy to use,
but I do like this one It’s responsive – immediately doing
what I want it to do. Here we see the temperature in the probe. It is monitored to make sure the readings are always as precise and possible and don’t drift over time with temperature. Nice! All right, looks like we end up with 18.1 microtesla
on the horizontal, north-south Z-axis 46.4 microtesla on the vertical, up-down X-axis And a total magnitude of 49.8
microtesla for the magnetic field. Now, let me rearrange and use this probe to measure the angle – inclination –
of the Earth’s magnetic field. If I can get both the X- and Y-axis close to 0 Then I know the probe is following
the magnetic field vector perfectly. First, I find the north-south direction. Again looking for a 0 on the Y-axis in this setup. Then I tilt the probe until the
X-axis is also close to 0. This is a mountable probe,
but I’m lazy and just eyeball it by hand. After some small adjustments I find the spot. Looks like the probe is following the
magnetic field at an angle of 70 degrees. And the overall magnitude is
still around 50 microtesla. Awesome! Let me show just how awesome this result is. Here’s an official plot of the Earth’s
magnetic field from December 2014. The inclination where I live Denmark – more precisely Central Jutland is 70.4-ish degrees. The intensity on the horizontal axis
is around 17 microtesla. And on the vertical axis around 47 microtesla. Total intensity is around 50 microtesla. Look at this chart. I did not expect to reach
this precision in microteslas with a probe capable of up to a whopping 35 tesla. If an amateur like me can
make such precise measurements – with little effort, handheld, in my kitchen – I wonder what a real scientist
can do with this teslameter? If you are that and looking for a
new, high-grade gaussmeter for your lab there’s a link under the video. Okay, I am now sure that the magnetic
field is indeed almost vertical where I live. But why? To explain it we need to look at
the origin of the Earth’s magnetic field. It’s not the entire Earth that’s a magnet. It is believed that the molten iron and
nickel in the outer part of the Earth’s core is generating the magnetic field. The diameter of the outer core is
roughly half of the Earth’s diameter And that’s a big clue. I will make a model of it using this world globe. First, I need to get inside it. Should be easy with this cheap one.
Equator is just a sticker. – Arghh! Hmmh. Maybe it needs
a little percussive persuasion. Uhm… they did bother to glue it.
This won’t be pretty then. Great, now I just need
to find an outer core. On this scale it is a sphere magnet
with a diameter of 16 cm. My largest magnet is the only
one coming close to this. With the model set up, it is now clear to me that I’m living on TOP of a magnet –
not on the side of a magnet. The magnet is simply beneath me,
since I live close to the North Pole. The field is vertical on the North Pole and in Denmark it is still
not far from being vertical. Only if you live near Equator will
the magnetic field be horizontal. Thanks to all my patrons. Creators like me aren’t always
praised here in the internet but at least I have your fantastic support. Thank you very much! Also a big thanks to Lake Shore Cryotronics. Thank you for giving me the opportunity
to live my childhood dream and play with a real lab instrument. Finally, a big thanks to YOU – my viewer. 2018 has been quite a year for me and my channel. Hope to see you again in 2019. Remember to click the bell,
if you missed some of my 2018-videos. Happy New Year!

49 Comments

Add a Comment

Your email address will not be published. Required fields are marked *