Lise Meitner was an Austrian-Swedish physicist who worked on radioactivity and nuclear physics. In 1939 Meitner was part of a group of scientists who discovered nuclear fission. In doing so, she helped create nuclear power plants (and unfortunately nuclear weapons). Through the story of Lise Meitner, we’ll explore energy in its many forms.
Lise Meitner was born on November 7, 1878, in Vienna, Austria. She entered the University of Vienna in 1901, studying physics under Ludwig Boltzmann. After she obtained her doctorate degree in 1906, she went to Berlin in 1907 to study with Max Planck and the chemist Otto Hahn. She worked together with Hahn for 30 years, each of them leading a section in Berlin’s Kaiser Wilhelm Institute for Chemistry. Hahn and Meitner collaborated closely, studying radioactivity, with her knowledge of physics and his knowledge of chemistry. In 1918, they discovered the element protactinium. The experiments that provided the evidence for nuclear fission were done at Hahn’s laboratory in Berlin and published in January 1939. In February 1939, Meitner published the physical explanation for the observations and, with her nephew, physicist Otto Frisch, named the process nuclear fission.
In 1944, Hahn was awarded the Nobel Prize for Chemistry for his research into fission, but Meitner was ignored, partly because Hahn downplayed her role ever since she left Germany. The Nobel mistake, never acknowledged, was partly rectified in 1966, when Hahn, Meitner, and Strassman were awarded the Enrico Fermi Award. Meitner retired to Cambridge, England, in 1960, where she died October 27. In 1992, element 109, the heaviest known element in the universe, was named Meitnerium (Mt) in her honour. Many consider Lise Meitner the “most significant woman scientist of the 20th Century.”
What is energy?
Do you ever feel like you just don’t have the energy to do something? After a hard day’s work or a long school day. We should be familiar with the concept of energy in our every day lives. To a physicist, energy is defined as the ability to do work. When we say work, we don’t just mean a job, we mean the ability to move things, heat things up, to do things. Energy is one of the fundamental properties of our Universe, and it’s important to learn how to convert and harness energy for our own good. There are many forms of energy, see if you can recognise some of the forms in the list below:
- Kinetic energy: When an object is moving
- Potential energy: When an object is at a height or has stored energy (coiled spring)
- Heat energy: Energy from vibrating particles, causes a change in temperature
- Sound energy: Caused by vibrating sound waves
- Light energy: Light is made of packets of energy. The Sun is our main source of light energy
- Electrical energy: Caused by the motion of electrically charged particles
- Chemical energy: Stored in chemicals and is released during chemical reactions
- Nuclear energy: Release of energy by the splitting (fission) or joining (fusion) of atoms
Conservation of Energy
Energy cannot just be created out of nowhere, nor can it just be destroyed; it can only be converted from one form to another. This is known as the law of conservation of energy. A way to think about this is Energy Before = Energy After. If we think of the conservation of nuclear energy that goes on in nuclear bombs, when it is detonated the nuclear energy is created by splitting or joining two atoms. This energy is then converted to light, heat and sound energy when the bomb explodes. The energy hasn’t been used up, it has just been converted to a different form.
Another way to think about it is if you are on a roller coaster and you reach the very highest point and you stop for just a second, right before a huge drop. At the top of the ride, all of the energy is potential energy – the rollercoaster is not moving and it is at it’s highest point. Then you start going down, getting faster and faster until you are at the very bottom where you are going at maximum speed. At this point, all of the energy is kinetic. So in this case, all of the potential energy has been converted to kinetic.
At the start of the 20th century, scientists finally started to understand the mysteries of the atom. First, they discovered that the nucleus (at the centre of every atom) was made up of protons and neutrons. They next wanted to understand the force that held these two particles together inside the nucleus. Lise Meitner was heavily involved in the early experiments, with her supervisor Otto Hahn and Fritz Strassman. Together, they discovered nuclear fission.
Fission occurs when a neutron hits a uranium atom, causing it to split up (i.e. it decays) into smaller elements. This process releases even more neutrons, which can then lead to a chain reaction and the reaction repeats itself many times. The splitting up of atoms into smaller atoms releases massive amounts of energy. Fission reactions are used in nuclear power plants but they give off radioactive waste and can be very dangerous if they are not looked after properly.
Fusion is the opposite of fission. Instead of splitting up an atom, fusion is the process where two hydrogen atoms combine to form a heavier element (called deuterium). The deuterium atom can then combine with a hydrogen atom to form tritium. These processes also release massive amounts of energy. Fusion takes place in the Sun, and it is how we get heat and light here on earth. If we could make a fusion reactor power plant, it would be the cleanest, most efficient way to produce energy. However, this hasn’t been achieved yet because the temperature and pressure needed to produce these reactions is just too high!