A Blog for the Curious and the Scientifically Perplexed

This is the story of a great journey that started with a great thought. One day in 1895 a boy looked into a mirror and wondered what the universe would look like if he could travel on a beam of light. That sixteen year old boy was Albert Einstein and that one thought started him on the road to discover his Theory of Relativity. The great man has been reinvented as Albert 2.0 to come back and blog about a journey through space on a beam of light and explain the science behind everything from atoms, blackholes to global warming. If you've just joined and want to start at the beginning use the index on the left. If you're bored try these links below just for fun.


Monday, April 23, 2007

Leaving Albert's Star

Shall we start on our way?

“Why not.”

Why not, indeed. One of the best reasons for doing anything. So here we are at one of my favourite stars, Deneb. Stars are grouped together into what are called constellations and named after animals or mythical beings. Our star is part of the constellation Cygnus or the Swan. For most constellations the pattern of the stars doesn't really look like anything, let alone an animal. On a clear summer night our constellation is almost overhead, a huge majestic cross with outstretched arms. So it really does look like a swan in full flight.

“Does it?”

Well sort of like a swan, in the same way a stick drawing of a man looks like a man. Our star Deneb is the tail of the Swan and a huge distance from the Earth, 18,970,843,745,070,000 miles to be precise. It’s hard to imagine what that kind of distance really means but in car journey terms it would take over thirty billion years at a steady 70 miles an hour.

"Wait a minute, how can we get there in 3000 years if it would take thirty billion years to drive there?"

But we’re not going to drive, we’re going to fly through space. We are going to cover such a huge a distance in such a short time because we're travelling at the speed of light. We are light particles or photons now. Not just any light, the very best type of light – starlight. So travelling at light speed comes naturally to us. Even though this sounds like a long journey, it’s really a fairly short stroll through this galaxy, the Milky Way, a journey of a mere 3,227 light years in a galaxy that is over 70,000 light years across.

“Is a light year the same as a normal year?”

Even though it sounds like it ought to measure time, a light year is a measure of distance rather than time and is how far light can travel in a year. At 186,000 miles a second and with over 31,000,000 seconds a year that makes a distance of almost 6,000,000,000,000 miles or six trillion miles. To give you some idea how far a light year really is, the Earth’s moon is only a light second away. Now think how much longer a year is than a second.

Deneb, is one of the largest, brightest stars in the whole galaxy, that’s why I like it. It's 160,000 times brighter than the sun and much bigger. So big that in the Earth's solar system it would stretch all the way from the Sun to the Earth. If the Earth were going around Deneb rather than the Sun it wouldn't be floating in space but skating along the star's surface and cooked to a temperature of over 8,000 oC. Deneb only looks like a very normal star because it is so far away. If Deneb was as close as Earth as the nearest star, Proxima Centauri which is only 4 light years away, it would be bright enough to cast shadows at night and be visible day and night.

“So what would the sun look like from Deneb?”

Not very impressive. If you looked in the direction of the sun from Deneb with just a pair of eyes you wouldn’t even be able to see it. You’d need a very powerful telescope to make it out as a faint very ordinary looking star. If today you had a powerful enough telescope to see what was happening on earth all the way from Deneb what would you see?

“Is that possible?”

No, but try and imagine it.

“OK, well you’d see all the people doing what people do these days I suppose.”

Not at all, you’d see what people were doing three thousand years ago. If light takes that long to travel from Deneb to the Earth, it will take that long to go the other way. So the light from earth reaching your telescope would be three thousand years out of date. If little green men from the Deneb solar system pointed a huge telescope towards the Earth today they would see the Earth around the time of the Trojan horse.

“So is all starlight old?”

When you look up at a star filled night the light reaching your eyes has been traveling for tens, hundreds or even thousands of years. For each star the light you are seeing started its journey at some moment in history. Imagine there are stars whose light started towards Earth before the time of the ancient Greeks and Romans and light that has been traveling since before Columbus first set foot in America. As you look up there is starlight that left its star in the year you were born and light from galaxies that has been traveling for millions of years.

“I thought that people claim to tell the future from looking at the stars?”

Oh astrologers think that but when you look at the stars you are looking at the past not the future. Don’t confuse astrology with astronomy. Astrology is merely the art of telling people what they want to hear. Astronomy is the science of working out what stars are and what is happening out here in the universe.

"So why is our star called Deneb?"

Well not all stars have names but where there is one it usually comes from the ancient Arabic astronomers. The Romans named most of the planets after their own Gods but didn't seem to bother so much with the stars. After the Greeks and Roman empires died out and before Europe emerged from the dark ages, the Arabic universities in places like Basra in modern day Iraq became home to the world’s best mathematicians and astronomers.


Oh, Iraq was part of a great civilisation back then with the most important universities before any had even started in Europe. Have you ever wondered why all of Europe speaks different languages but write numbers down in the same way?

“No, but now you mention it that’s an amazing thought.”

Well, that because the way we all write numbers comes from one place, Arabic mathematicians in places like Iraq. Every country seems to have one golden era, sadly they never last for ever. Iraq, Egypt, Greece, Italy have had their day in the sun. I don’t suppose today’s great countries will be so great in another thousand years. That thought should make the leaders of today’s superpowers a little more humble, but I suppose you don’t get to lead a superpower by being humble. Anyway our star Deneb got its name from the great Arabic astronomers, though over the centuries it changed slightly - its name comes from the Arabic Al Dhanab al Dajajah that means 'the tail of the hen'.

"I thought our constellation was a swan."

Well things have gotten a bit mixed up over time, but all things considered we've been quite lucky with our names. Take Betelgeuse, the big red star in the constellation Orion, the Hunter. This star started with the Arabic name Yad al-Jauza, or Hand of Orion. It somehow ended up as Bait al-Jauzah which over time became Betelgeuse which apparently means the ‘Armpit of the Mighty One’.


  1. Anonymous said...
    It seems that light does not age as it travels. That being the case, light must not pass through time and necessarily not through space either. If so, light must be everywhere and undetected until photons enter the eye.
    dug11 said...
    Outstanding page my friend. If photons are every where and undetected until human detection equpment picks it up, then a dark room is actually a very unprobable occurance in the universe.
    Anonymous said...
    Talking about the way we write numbers originating in Arab countires is misconception. These numbers including decimal system and concept of zero and infinite originated from India and was then taught to Arabs. Before that people were mostly used to Roman numerals.
    usernamealreadyinuse said...
    Maybe being able to travel faster than the speed of light can cause us to live forever. Maybe going fast is the key to eternal life. That when we are able to move fast enough, like the Browning theory, if we can move fast enough in a liquid or gas state (kind of like space) we can travel through time and space with our own ability to move. We could combust into a light hole instead of a black hole.
    Anonymous said...
    If you were in a room at night that was closed up so no light could get in at all, and you had no source of light, would your eyes adjust and would you eventually be able to see?
    albert2.0 said...
    Over 20-30 minutes your eyes will adapt to darkness so that you might be able to see something in a room that looked completely black initially. But if there is no light at all your eyes will never adapt. If you were a viper it would be different as you could detect infra-red light with your vomero-nasal organs.
    rantaholic said...
    So our universe is pretty big and our leaders are pretty dumb. Can't argue with that, I suppose. Light travels at a fixed speed. Why is that? And while it seems pretty fast (to us), it's actually pretty slow (relative to size of the place it is in).
    Open mind said...
    Astrology addresses the impact of time and space on Man, if Man is also a progression of matter in space and time with his own ray of light from his "home star".

    It is as much science as Astronomy is and moving futher east from Basra and further in history more ancient wisdom is available on this.
    Patrick F. said...
    ok i understand most of this. so if little green men looked at earth using a telescope they would be looking back into the past. BUT what if they sent a ship at light speed to view us from within our solar system, Does this mean that they could view Earth at present day and during the past, so in essence they could watch the growth of our civilisation to the point of time where the ship is???

    Seruisly tho, the concept of exploring space is a wriddle wraped in an enigma. The stupid world leaders today are too busy focusing on the more important things in our little lives like war, the olympics, religion and how to better the Big Mac.(but mind you, i do enjoy a Bic Mac here and there)

    RYMELL GARY said...
    Anonymous said...
    is there a limit to the distance light can travel
    Anonymous said...
    Light travels fastest in a vacuum. But this speed changes depnding on the media it travels through (air, water, etc.). The slowest speed recorded is through sodium at -272 C during which the speed of light fell to 60kph.
    Alicia DeWitt said...
    Patrick F,
    If a ship could travel at the speed of light, it could fly from Deneb to Earth in about 3000 years. The Green Men back on Deneb would then have to wait another 3000 years before they could see the landing of their countrymen on Earth through their mighty telescope. Perhaps, though, Green Men live for millions of years, so a mere 3000 wouldn't bug them.
    Anonymous said...
    The use of Arabic numerals is not a misconception at all. What numerals has the Yemenis used to build their prehistoric great dam? Or the Pharaohs in their Pyramids? What about the Sumerians, Babylonians, Akkadians, Assyrians, used and where have they lived? All of those are Semites Arab and not the other one.
    Anonymous said...
    This is amazing stuf!!!! i liked how you kinda illouminated the star deneb!!!! I'ts kinda amazing also how i can read and understand this when im in 6th grade
    Anonymous said...
    If we are seeing Denab as it looked 3,000 years ago when we look up at it in the sky tonight. This must mean we are not looking at an actual mass object, we are actualy looking at a kind of projection of a mass object. So this means we are never looking at any actual mass object, EVER!, even the computer screen in front of me as I,m writing this. We never get to see the actual object. We see everything with a time delay. So if I reach out and touch my computer screen I will feel it before I see myself touch it!?.
    Anonymous said...
    In response to the comment about touching a computer screen: Not necessarily because of the time it took for your nerves to send a signal to your brain, but essentially, I would have to agree that you would have ACTUALLY touched the computer screen before you SAW it, or FELT it, which is something weird to think about.

Post a Comment