Serious Science: Blood Moon Eclipse

This amazing article was researched and written by Saoirse Flanagan.   

On the night of September 27th a Total Lunar* Eclipse of a Super Full Moon was visible in North America, South America, West Africa and here in Europe. So what is a total lunar eclipse? It is when the moon appears darkened as it passes into the earth shadow that is cast from the sun behind the earth; the Sun, Earth and Moon to form a straight line.

                                 

The eclipse in September was especially rare because it was an eclipse of a Supermoon. This meant that the moon was at its closest point to the earth, therefore looking larger and brighter to us on earth. No special equipment was needed to view this eclipse and protective eye wear also wasn’t necessary.

A Total Lunar Eclipse can also be called a Blood Moon because the earth’s atmosphere refracts* sunlight and lights up the moon surface. Only the longer wavelengths of the light spectrum reach the surface and therefore giving it its red colour.* A Blood Moon is also commonly used to describe a tetrad. What is a tetrad you ask, it is four successive total lunar eclipses, with no partial lunar eclipses in between, each of which is separated from the other by six full moons.

*Refraction-The bending of light when it goes from one medium to another.

*Lunar-Something relating to the moon.

*Light Spectrum and wavelengths-To read more click here.

Sources:

11 Facts About the September 27/ 28, 2015 Blood Moon Eclipse

Awesome photos from the total lunar eclipse 

What is a blood moon?

Picture sources:

http://www.reformation.org/targeting-the-moon.html
http://www.express.co.uk/news/world/470810/The-Bible-is-coming-TRUE-Rare-blood-moon-eclipse-fulfills-ancient-prophecy-claims-church
http://www.irishtimes.com/news/science/delight-for-irish-stargazers-at-clear-skies-for-supermoon-1.2369573

Teacher's note:

Thank you Saoirse for this fantastic article!
Submissions are welcome from all students in Coláiste Muire. Call into the computer room at Tuesday lunchtime to meet the blog team and get started.

Link-up Summary: Sound

Sound is a form of energy caused by vibrations. 

Click on the picture to see the animation.

Sound is produced when particles vibrate.
A loudspeaker creates sound because is causes the air around it to vibrate in a pattern of waves that reaches your ear... see the animated version here.

The sound of your voice is produced when your vocal chords vibrate as air is passed over them.

Hearing 

The ear is a sense organ which detects sound vibrations. Exposure to very loud sounds can cause damage to your hearing.

• The outer ear collects the sound and channels it along the ear canal. 
• The middle ear (ear drum and tiny bones called hammer, anvil and stirrup) conducts the sound into the inner ear. 
• The inner ear converts the sound energy (vibrations) into an electrical signal which can be sent to the brain. 
• The auditory nerve is a sensory nerve which sends electrical signal to the brain. 

This animation shows the structures in the ear very clearly. 

Sound needs a medium to travel through

Because sound is transmitted through the vibration of particles, sound needs a medium to travel through, such as air or water.

A vacuum is a space that is completely empty of matter. There are no particles in a vacuum. Sound cannot travel through a vacuum.

This animation shows a bell inside a jar. When all the air is drawn out of the jar, and a vacuum is created, you can no longer hear the sound of the bell.

Because sound cannot travel through a vacuum, this means that sound cannot travel in outer space.

This article talks about sound at high frequencies... and how students can hear sounds that teachers probably cannot hear! 

Speed of sound 

Sound travels more quickly through materials that are more dense.

Check it out: tap your finger lightly on the desk. You probably hear a quiet sound. Now lay your ear on the desk and tap again. Can you hear a difference?



Sound can travel through the solid material of your desk more quickly than through the air.

Sound travels faster through liquids than it does through gases, such as air. So the speed of sound in water is 1500 metres per second, while the speed of sound in air is only 340 metres per second.

Thunder and lightning 

Thunder and lightning originate at the same moment. However you can often see the lightning before you hear the thunder. This is because light travels faster than sound. Learn how to calculate how far away you are from the storm here.

Echoes 

Echoes are reflected sound.

Ships use echolocation to measure the depth of the sea below them.

Fishing boats can also use echolocation to detect shoals of fish swimming beneath the boat.

Click on the picture to see the animation

And finally...

How do we know that sound is a form of energy?

Remember that sound is a form of energy, caused by vibrations. Here is a video of an Irish physics teacher demonstrating that sound is a form of energy. Energy is the ability to do work or to move something. The sound energy from the speaker causes the flame of the candle to move.

Knowledge check:

OP40   Show that sound is a form of energy, and explain that sound is produced by vibrations

OP41   Show that sound transmission requires a medium and that echoes are reflected sound

OP42   Appreciate that the ear detects sound vibrations and that exposure to very loud sounds can cause damage to hearing

OP43   Recall that the speed of sound is less than the speed of light

OP44   Explain the time lag between seeing and hearing the same event

Post compiled by Ms McCarthy. The website thephysicsteacher.ie contains many helpful links which I have used in this blogpost.