For the last several years and culminating in six months in orbit next year, I've been training for my third space flight. This one is almost in a category completely different than the previous two, specifically to live in on the space station for six months, to command a space ship and to fly a new rocket ship.

The mission of '8 Mile' is essentially to garner sympathy for a white rapper involved in an old-school shootout - a rap contest. This may be the final frontier for pop, more unbelievable than the prospect of launching a member of 'N Sync into orbit.

If you're going to go into space, you have to have an objective, a mission. Where do you want to go? Earth orbit? The moon? Mars? What's the technology to get there? You develop the technology for the mission.

I wound up getting offered a job at the NASA Jet Propulsion Laboratory where I invented a power supply mechanism for the Galileo space craft which was in orbit around Jupiter until 2003.

The density of space junk peaks around 620 miles up, in the middle of so-called low-Earth orbit. That's bad, because many weather, scientific, and reconnaissance satellites circle in various low-Earth orbits.

One of the things that I'm very excited about with New Shepard, which is our suborbital tourism vehicle, is using that to get a lot of practice. One of the equilibria that we're at today with space launch is that we don't get to practice enough.

But thanks to the International Space Station, we're able to study the effects of weightlessness and develop countermeasures in orbit, close to Earth.

Most Jupiter-sized planets orbit the mother star in a highly elliptical orbit. This means they will often cross the orbit of any Earth-like planet and fling it into outer space, making life impossible. But our Jupiter travels in a near-perfect circular orbit, preventing a collision with any Earth-like planet, making life possible.

The years of space flight since the orbiting of Sputnik I back in 1957 had produced many fascinating results, but they had also brought a realization of the many problems that surrounded the use of rockets for space flight.

Astronauts have been stuck in low-Earth orbit, boldly going nowhere. American attempts to kick-start a new phase of lunar exploration have stalled amid the realisation that NASA's budget is too small for the job.

There are thousands of asteroids whose orbit in the Solar System crosses that of Earth. And we have a little acronym for them - NEOs: near Earth objects. And our biggest goal is to try to catalogue them, so we know in advance if one is going to put us at risk.

Our astronauts, when they go orbiting around the earth, they actually come back slightly younger than a twin that they would have on the planet Earth who was stationary. This is called the twin paradox.

The lunar flights give you a correct perception of our existence. You look back at Earth from the moon, and you can put your thumb up to the window and hide the Earth behind your thumb. Everything you've ever known is behind your thumb, and that blue-and-white ball is orbiting a rather normal star, tucked away on the outer edge of a galaxy.

I watched the moon landing as a boy, and I thought that was the most exciting thing ever, going into space, orbiting Earth and exploring other planets. That looked fantastic.

There is a project that's underway called the interplanetary Internet. It's in operation between Earth and Mars. It's operating on the International Space Station. It's part of the spacecraft that's in orbit around the Sun that's rendezvoused with two planets.

Mars has been flown by, orbited, smacked into, radar inspected, and rocketed onto, as well as bounced upon, rolled over, shoveled, drilled into, baked, and even laser blasted.

The digital world has been in a separate orbit from our medical cocoon, and it's time the boundaries be taken down.

No oppression is so heavy or lasting as that which is inflicted by the perversion and exorbitance of legal authority.

We are convinced that universal health coverage, with strong primary care and essential financial protection, is the key to achieving the ambitious health targets of the sustainable development goals (SDGs) and to avoiding impoverishment from exorbitant out-of-pocket health expenses.

Some things, like the orbits of the planets, can be calculated far into the future. But that's atypical. In most contexts, there is a limit. Even the most fine-grained computation can only forecast British weather a few days ahead. There are limits to what can ever be learned about the future, however powerful computers become.

When the space shuttle's engines cut off, and you're finally in space, in orbit, weightless... I remember unstrapping from my seat, floating over to the window, and that's when I got my first view of Earth. Just a spectacular view, and a chance to see our planet as a planet.

John Glenn's anniversaries have followed me all of my life. I was born in 1962, the year he orbited Earth.

In the 20th century, we had a century where at the beginning of the century, most of the world was agricultural and industry was very primitive. At the end of that century, we had men in orbit, we had been to the moon, we had people with cell phones and colour televisions and the Internet and amazing medical technology of all kinds.

"We all come into this world the same: naked, scared, and ignorant. After that grand entrance, the life we end up with is simply an accumulation of all the choices we make. Our choices can be our best friend or our worst enemy. They can deliver us to our goals or send us orbiting into a galaxy far, far away.