The Cosmic Background Microwave Radiation is the oldest light in the universe. 

Light travels at a finite speed. So, believe it or not, when you turn on a light in a dark room it takes a (very tiny) amount of time for the photons (light particles) produced by the bulb to fill the room. It's just that this happens so quickly, we can't see it.

The Cosmic Background Microwave Radiation is an echo of when the first photons could travel freely, shortly after the universe's creation (about 380,000 years, which isn't very long in a universe's lifetime).

This radiation marks the moment where the lights went on in the universe. It's just that the universe is a lot bigger than your living room, so this light has taken a lot longer to reach us.

The Cosmic Background Microwave Radiation is the furthest back in time we can explore using light. It's a snapshot in time and can reveal a lot about the initial conditions for the evolution of the universe.

​For example, it gives us hints as to how and why the stars and galaxies formed and was also provides one of the key pieces of evidence that the universe started with a Big Bang.

As the universe expanded, the wavelengths of the Cosmic Microwave Background photons have grown (or have been ‘redshifted’) to 1mm. Their effective temperature has also decreased to just 2.7 Kelvin, or around -270ºC, just above absolute zero.

And these photons fill the Universe today. There are roughly 400 in every cubic centimetre of space.

The Cosmic Background Microwave Radiation creates a background glow that can be detected by far-infrared and radio telescopes.

The Cosmic Background Microwave Radiation was discovered completely by mistake in 1964. Arno Penzias and Robert Wilson were using a large radio antenna in New Jersey when they picked up an odd buzzing sound coming from all parts of the sky.

They tried to remove the source of this (assumed) interference, and even removed some pigeons that were nesting in the antennae!

"When we first heard that inexplicable 'hum,' we didn’t understand its significance, and we never dreamed it would be connected to the origins of the universe," Penzias said in a statement. "It wasn’t until we exhausted every possible explanation for the sound's origin that we realized we had stumbled upon something big."

They were awarded the Nobel Prize in Physics in 1978 for the discovery.

The European Space Agency (ESA) is investigating the Cosmic Microwave Background Radiation with the Planck spacecraft to study this ancient light in more detail than ever before. NASA's Wilkinson Microwave Anisotropy Probe (WMAP), which launched in 2001 and stopped gathering data in 2010, and its COBE (COsmic Background Explorer) craft both provided early images of the Cosmic Background Radiation.

The Cosmic Microwave Background Radiation also provided evidence of primordial gravitational waves - which is the "smoking gun" to support the theory that the universe expanded in a cosmic inflation.

I've attended many talks during my 15 years as a science and tech writer and sometimes, when I look back on my reams of shorthand notes, I struggle to find an interesting angle.

Last week, I attended a symposium with Apollo astronaut Charlie Duke. And I'm struggling again with my notes. But only because there are so many wonderful snippets of information that I'm struggling to know where to start.

So, I'll start at the beginning and do my best to summarise what was the best talk I have ever had the privilege of attending, using a few of Charlie Duke's own words.

Charlie is a respectful man who commands great respect with his humble, yet engaging, manner. He struck down the well-pattered conspiracy theories around the moon landings with the same amount of considered respect throughout his talk.

Another wonderful nugget of information also came to light, as Charlie explained why the US flag appears to 'flutter' on the lunar surface: "It was vacuum packed for six months and I could not get the wrinkles out."

So, there you go. The flag is not blowing in the breeze of whatever desert people claim the lunar landings were filmed. It was just wrinkled. (And, if you take a look at the Apollo 16 shots, the same pattern of wrinkles appear in the flag at all times - it's not moving.)

But this rebuke around the nine lunar landings is my favourite. Charlie was involved with five out of nine of the Apollo moon programs. He's formed part of the astronaut support crew and worked as CAPCOM (the Capsule Communicator who communicates directly with the crew of a manned space flight).

He was CAPCOM during the Apollo 11 landing. It was a particularly tense and long landing that almost expended all of the Lunar Module Eagle's fuel. Duke's first words to the Apollo 11 crew on the surface of the Moon (when a safe landing was confirmed) were flustered: "Roger, Twank... Tranquility, we copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot!"

Just to give you an indication of Charlie's character, he also repeated that famous phrase when asked in front of the entire auditorium in his distinctive Southern drawl that made him familiar to audiences around the world in the 1960s and 1970s. Fantastic.

The glamour of the space program was also quickly refuted by Charlie. From tales of sharing a 300 cubic foot space with two other astronauts to spending 1,000 hours in a simulator or 500 hours in the hot Florida sun practising the aforementioned rock picking, Charlie is quick to point out: "A space flight is not a guaranteed route to fame and fortune."

The Apollo 16 mission collected nearly 213 pounds of rock and soil samples and, despite extensive geological training, Charlie admitted they chose to "pick up one of every colour" on the lunar surface. He also claims he broke the lunar land speed record using the mission's rover (something other moonwalkers dispute!) and that parking on the moon is pretty easy because "you can just pick up your car and put it in a different spot".

But one of my favourite stats comes around the budget for flying three men to the moon. According to Charlie, the Apollo 16 astronauts received $25/day for the trip, so that's $275 for the 11-day trip. Charlie said: "I could buy, maybe a new golf bag with that. So, I filled out a travel voucher instead."

"Unfortunately, meals and quarters were deducted. I got $13.75 in expenses for the moon landing."

This is Charlie's impression of space. The strikingly simple phrase perfectly sums up what (I can only guess) it must be like to peer out of your window and see nothing, yet everything.

It's not just space that's vividly black, so is the dark side of the moon, according to Charlie. Apparently, later Apollo programs were interested in landing on the dark side, but Mission Control refused this request. And, after passing on the dark side, Charlie said: "​It was so black, you'd think it was space. But it was the moon that was black. It looked really, really rough and I'm glad we did not land there." 

The broad and fine details of Charlie's time in space and on the moon are fascinating. From seeing Earthrise to dropping a $10 million science experiment on the lunar surface (it was fine), Charlie and fellow astronaut John Young spent a record-breaking 71 hours and 14 minutes exploring the moon. ​"Every time we crossed a ridge, we did not know what we would see," he added.

The dusty surface of the moon also has a very familiar (but unexpected) smell, according to Charlie. When dust transferred from their spacesuits and gained moisture in the spacecraft: "We had a strange feeling that it smelt like gunpowder."

Charlie also thought he'd try his hand at the high jump on the team's very own version of the Olympics (his lunar landing happening in 1972 ahead of the Munich games). He lost his balance and landed on his back, which was no laughing matter as such an impact could have fatally compromised his space suit. "That ended the Moon Olympics. Mission control was very upset," he added.

Charlie remains optimistic that we will see a Marswalker in the future and the nature of the human spirit means: "We will figure it out." 

But, how are we going to figure it out? There are only six moonwalkers left on Earth and Charlie also made a very pertinent point about the space program. While some are swift to argue the money would be better spent here on Earth fixing our (somewhat mounting) problems, the ROI of the Apollo mission is ten-fold, with some studies estimating a $7 to $14 return for every $1 of NASA expenditure.

So, I hope that we will  start to see a new wave of moonwalkers. Not just because of the wider benefits such programs bring to society thanks to the employment and innovation they create, but because of the spirit of discovery they nurture in the human race.

If there was ever a time to look up to the stars instead of inwards, it's now.

Because we also need more Charlie Dukes. We need more advocates for science, exploration and innovation for the human race to thrive and survive.

Charlie repeatedly called his time on the space program "a privilege". Well, it was a true privilege to hear him talk.

Thanks to the Armchair Astronaut for organising such a great event! I may have missed a few key points as I was too enthused to make really detailed notes. So, if you were at the talk and want to share your experiences - please do so in the comments below.

Last week, I looked at the electromagnetic spectrum. At the one end of this continuous band of electromagnetic radiation, we have radio waves.

​Radio waves cannot be seen with the human eye. They carry the least amount of energy and have the longest wavelengths of all the electromagnetic wave categories. They're also incredibly useful in the field of astronomy.

Simply put, radio astronomy studies objects in the sky that give off radio waves. In our Solar System, the Sun and Jupiter give off radio waves. And, further away, the centre of our galaxy (the Milky Way), giant explosions called supernovae, and exotic celestial objects call pulsars and quasars are all radio sources.

Radio astronomy allows us to probe regions of space that cannot be seen using visible light. This is because radio waves can pass through dust, so radio astronomy has unmasked previously invisible regions of space. 

It also means that, unlike optical telescopes, radio telescopes are not hampered by clouds or poor weather.

​Radio telescopes are massive structures because they have to capture the long wavelengths of the radio spectrum. The largest radio telescope in the world as a single dish, is the Arecibo telescope. It was featured in the movie Contact, and is located in a natural hollow in Puerto Rico, South America. You may also be familiar with the Lovell radio telescope at Jodrell Bank (which is also one of the favourite places on planet Earth - I'd highly recommend a visit).

This huge white bowl of Lovell (and other radio telescopes) reflects incoming radio waves into the focus box mounted on top of the central tower. Here, at the focal point of the reflector, a small aerial picks up the waves and feeds them into a sensitive radio receiver where the signal can be transported and analysed.

To make a clearer (or higher resolution) radio image, radio astronomers often combine several radio telescopes into a pattern called an array. Together, these dishes act as one large telescope whose size equals the total area occupied by the array. This is a technique called interferometry.

The Very Large Array (VLA) in New Mexico consists of 27 radio telescopes, arranged in a Y-shaped configuration. Each telescope is 25 metres in diameter. All 27 telescopes are used simultaneously to observe a target, then their observations are added together.

To get an in-depth view of radio astronomy, the National Radio Astronomy Observatory is a great place to start and Jodrell Bank's website is a mine of useful information. Also, check out this page if you want to find out more about radio interferometry.

​It's not just the radio spectrum that you can use to probe the universe. You can also use gamma rays, X-rays, ultraviolet radiation, infra-red and microwaves.

This is a wonderful talk from radio astronomer Natasha Hurley-Walker too:

Hello. I’m the freelance writer who gets tech. I have two degrees in Physics and, during my studies, I became increasingly frustrated with the complicated language used to describe some outstanding scientific principles. Language should aid our understanding — in science, it often feels like a barrier.
​
So, I want to simplify these science sayings and this blog series “Sunday Science” gives a quick, no-nonsense definition of the complex-sounding scientific terms you often hear, but may not completely understand. 

If there’s a scientific term or topic you’d like me to tackle in my next post, fire an email to [email protected] or leave a comment below. If you want to sign up to our weekly newsletter, click here.
​

Twinkle, twinkle little star, how I wonder what you are? Well, the stars and other celestial objects we "see" are not just emitting visible light, they are also emitting a huge range of wavelengths across something called the electromagnetic spectrum.

The electromagnetic spectrum is a continuous band of energy that's radiated (travels out) of an object. 

Depending on its wavelength (typical values are shown in brackets below), the different portions of the electromagnetic spectrum can be used for very different things:

• Radio waves (1,000m) - TV and radio signals
• Microwaves (0.01m or cm) - Cooking and mobile phones
• Infrared (0.00001m) - Optical fibre communication
• Visible light (0.0000001m) - Seeing
• Ultraviolet (0.00000001m) - Detecting forged bank notes
• X-rays (0.0000000001m) - Medical imaging of bones and tumours
• Gamma radiation (0.000000000001m) - Killing cancer cells

Electromagnetic radiation is created when a particle, such as an electron, is accelerated by an electric field and this causes it to move. As the electron moves, it produces oscillating (moving back and forth in a regular rhythm) electric and magnetic fields. 

Electricity and magnetism are not separate entities. Electricity can cause magnetism and vice versa. The electric field and magnetic field contained in electromagnetic radiation travel at right angles to each other in a bundle of light energy called a photon.

The photon is both a particle and wave. It's a confusing concept and it's further discussed in this previous Sunday Science post.

Every photon travels at the same speed (the speed of light) and moves energy from one place to another. In the electromagnetic spectrum, long wavelengths have the lowest energy. So, radio waves have the lowest energy, and gamma rays have the highest.

The range of the electromagnetic spectrum is used in astronomy to detect and investigate some pretty amazing phenomena. This post provides a great introduction to the topic - and I'll be delving into radio astronomy in the near future.

And if you'd like an introduction to the equations behind the electromagnetic spectrum, check out this video:

Over the summer, Sunday Science has tackled the planets of the Solar System. It's remarkable the number of emails I've had asking me to include Pluto in the list - even though it was demoted to  "dwarf planet" status more than 10 years ago.

There are five officially recognised dwarf planets in our Solar System: Pluto, Eris, Ceres, Haumea and Makemake, but astronomers predict there could be hundreds more. (Check out the end of this post for a pretty cool animation.)

The fundamental difference between a planet and a dwarf planet is to do with what else is in its orbit around the Sun.

​Because Pluto shares its orbital neighbourhood with other dwarf planets and other objects in an area of space called the Kuiper belt, it's not classified as a planet.

The International Astronomical Union (IAU) has three criteria for a full-sized planet:

1. It is in orbit around the Sun.
2. It has sufficient mass to assume hydrostatic equilibrium (in other words, it can form a nearly round shape).
3. It has "cleared the neighbourhood" around its orbit.

​So, Pluto and the other dwarf planets fail on the last point. There are too many other objects sharing this orbital path.

Of the five dwarf planets, Ceres is the odd one out because it is located between in the asteroid belt between Mars and Jupiter. So, it's the closest dwarf planet to the Sun - and also the smallest with a mere 590-mile diameter.

Haumea has an elongated shape (a bit like a rugby ball), which is believed to be the result of its rapid rotation. It's named after the Hawaiian Goddess of childbirth (which is a nice contrast to Pluto - the Roman God of the underworld) and has two moons. 

Makemake​ was first observed in 2005 and is named after the god of fertility in Rapa Nui mythology. It's also the second brightest object in the outer Solar System and, despite sharing a lot of Pluto's characteristics, it does not have an atmosphere.

Eris is named after the Greek Goddess of discord and strife, which is quite fitting for a dwarf planet that's shrouded in controversy. When it was first discovered in 2005, Eris was thought to be larger than Pluto and it was submitted as the tenth planet in our Solar System. However, its discovery was one of the reasons Pluto was demoted in 2006 to dwarf planet status.

Yes. NASA's New Horizons probe flew past Pluto in 2015. The probe took multiple snaps of Pluto, including images of its icy mountains and a new view of its largest moon Charon.

​New Horizons is currently in hibernation mode before it prepares to fly past an icy body on the edge of our Solar System called 2014 MU69 on 1st January 2019.

Here's an animation I took from this fascinating Reddit post. The visualisation is from the simulator Universe Sandbox, which is based on the list of 'possible' dwarf planets from Caltech professor Mike Brown.

You can try this simulation yourself in Universe Sandbox by selecting home > Open > Solar Sys > Solar System All "Possible" Dwarf Planets (the author of this video also turned on view > Orbits).

And here's quite an extensive video all about Pluto:

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