As children, we all learned of Sputnik, the artificial satellite launched into a low earth orbit on October 4, 1957, by the then USSR, thus beginning the entry of humans into space. The US responded with the launch of Explorer 1 a few months later on January 1, 1958, starting the Cold War Space Race.

Subsequently a number of artificial satellites were sent out to serve as technological and scientific laboratories as well as for political and military purpose. I remember the infamous Skylab, which was a source of both thrill and fear to me as a child because it had been damaged and was going to "fall on our heads and destroy the Earth". Skylab was in service 1973 to 1979 and I was perversely disappointed when it disintegrated after re-entering Earth's atmosphere and did not cause any damage to us mere mortals.

This was followed by Mir, the Soviet (and subsequently Russian) Space Station that orbited the Earth from 1986 to 2001.

In 1990, the Hubble Space Telescope was launched and still remains in orbit. It has presented us with some of the most amazing and detailed images ever, increasing our understanding of space and time. The telescope helped astrophysicists to accurately determine the rate of the expansion of the Universe.  

Mir was succeeded by the International Space Station, fondly known as the ISS, a floating space lab, whose first component was launched in 1998. It is now the largest artificial body in orbit around our planet and can often be seen with the naked eye. In fact, NASA actually will send you emails to let you know when the ISS will be visible at your location. You can apply for them here.

The ISS is a joint venture between the US, Russia, Japan and EU, and more than 220 people from 17 countries have visited it since the year 2000. Its purpose is to serve as a micro-gravity and space environment research laboratory and where crew members conduct experiments in a number of scientific fields. But the most exciting thing about it is that the ISS was actually assembled in space, making it the largest structure to have been built there – ever!

The reason for my writing this blog is that recently the ISS celebrates its 15th anniversary of continuous human habitation. The first crew docked in 2000 and 12 years later, 2012 the ISS's robotic arm captured the first ever commercial vehicle the SpaceX Dragon.

More than a thousand experiments have been (and still are) conducted and have resulted in more than 1,200 scientific publications. The first research study was regarding protein crystal growth, happening before humans lived there, and which is helping to treat diseases and disorders on Earth. Plus, 189 spacewalks have been conducted by astronauts to maintain and repair the ISS to date, which are telecast live on NASA TV. Forget all those Hollywood movies in space showing space walks, you can watch the real action live! Food has also started to be grown there and this year, in August, astronauts tasted lettuce that had been grown and harvested in space for the very first time.

With the rise of social media, astronauts now tweet images from space, as well as videos of them going about their daily business, as well as showing what happens to objects in microgravity. Commander Chris Hadfield (@Cmdr_Hadfield) made tweeting from space famous and in fact released an album from the ISS.

The astronauts currently residing on the ISS are Commander Scott Kelly (@StationCDRKelly), Kjell Lindgren, Kimiya Yui, Sergey Volkov, Mikhail Kornienko, and Oleg Kononenko, all of whom are part of expedition 45. Commander Kelly and Mikhail Kornienko  are scheduled to be on the ISS for one year (most expeditions last 4 to 6 months) to understand how the human body reacts to long duration space flights. Kelly has already been in space longer than anyone else and meanwhile on Earth, his twin brother, retired NASA astronaut will participate in comparative genetic studies.

Once again I cannot help thinking that this is a great time to be alive. Space exploration, and experiments such as those done in the ISS, are opening our horizons and making us understand the Universe in ways we never have before.

So on its 15 anniversary let's take a moment and look up at these intrepid people who are helping us understand the Cosmos and our role in it.

No better place to celebrate #15YearsOnStation! #HappyBday, @space_station! Thanks for the hospitality! #YearInSpace pic.twitter.com/gJRxwoj6dF

— Scott Kelly (@StationCDRKelly) November 2, 2015