Waves
We are all familiar with waves; from ripples on the surface of a pond to the swell of the ocean. A wave is just a regular vibration that travels through something, like air or water.
Unlike sound, light waves can travel through nothing, like the vacuum of space. This means that the light coming from stars, and all other objects in space is able to reach us here on Earth.
Electromagnetic Spectrum
This light that we see is just one small chunk of light which is made by stars. We often call the small range of wavelengths our eyes can detect, optical, or visible light.
- Properties of each Electromagnetic Wave
Moving through the electromagnetic spectrum we go from short to long wavelengths and the frequency of the waves gets smaller. We go from high-energy to low-energy.
Wave-Particle Duality
To understand what happens to light when it reaches a mirror, we can say that photons bounce off the surface of the mirror. This treats the light as a particle like a ping-pong ball bouncing back. If we pass light through 2 holes then at the other side of the holes we see it interact like waves on the surface of a pond.
When we take a photograph on a modern camera, or on a telescope camera, we count these photons. The more we count the brighter an object is - we call this measurement the flux.
Spectra
Even though light often looks white, it is made up of lots of different colours all added together.
Astronomers often want to know exactly what colours of light there are coming from a star or galaxy. To measure this, they use an instrument called a spectroscope. These have prisms, or gratings, inside them which separate the light. They then record the data.
Light
When we talk about light we usually mean the light we can see with our eyes. This is also called visible or optical light.
- How does light travel?
For us to see, light must travel from a light source to our eye. The light we see on Earth travels in straight lines.
Anything in the path of light has an effect on what we see. For example, a window is transparent – this means that the light can pass straight through it.
Gravitational Lensing
Space is not flat. It is 3D, and we say that everything in it is held together on an imaginary surface we call spacetime. The idea of spacetime was put forward in Einstein's theory of relativity.
- How does Gravitational Lensing happen?
Lensing happens when light from directly behind a massive object, from our line of sight, can be bent around it. We call this gravitational lensing, and it is a way to see an example of the theory of relativity.
Relativity
Gravity is the force we are most familiar with in everyday life. It has been studied for longer than the other forces of nature. However, it is also the least well understood.
- Law of Universal Gravitation
Newton had correctly explained that every object in the Universe has a force which can be felt by every other object as a ‘pull’. We call it an ‘attractive’ force because it attracts objects towards each other.
The strength of this force is linked to the mass of the object. The more massive the object, the stronger the force. Newton also found that the force is linked to the distance between the objects. The further the distance, the weaker the force.
Light and Telescopes
One of the first people to study light was Ibn al-Haytham (known as Alhazen). He was a Muslim, living in Egypt in the early 11th Century. Alhazen is first person we know of who used the scientific method. He wanted to know why our eyes could see things.
Hans Lipperhey (also spelt Lippershey) was the first person to write down a design for a telescope. He made spectacles for a living, and in 1608 he applied for a patent for his new tool. He said it was "for seeing things far away as if they were nearby". Hans did not get the patent because other people were making similar tools. But, Hans was paid for his design. The first telescopes, known as Dutch Telescopes, contained both a convex and a concave lens.
Cecilia Payne Gaposchkin
Occupation
Astronomer
Year born
1900
Research Areas
Stars, Spectroscopy
- Early Life
Cecilia was born in Wendover, England. Her mother was interested in lots of different topics like nature, music and theatre. Cecilia spent lots of time reading in her home's library.
At the age of 19, she won a scholarship to Cambridge University to study science. During that time, Cecilia went to a talk given by Arthur Eddington. Arthur talked about his recent trip to Africa to observe the stars near a solar eclipse. This sparked Cecilia's interest in astronomy.