Hugh Wilson
08 December 2011 09:05 | By Hugh Wilson, contributor, MSN Him

Five incredible questions about the universe

Five incredible questions about the universe – and how close we are to answering them.

Five scientific questions (© Getty Images)

Kepler-22b might not sound like much, but to future generations it could also be called home.

That's because NASA announced this week that Kepler-22b is the most Earth-like planet ever discovered. The planet - 600 light years away from Earth - orbits in the so-called 'Goldilocks Zone', a distance from its sun-like star that is neither too hot nor too cold to support life.

Nobody knows if Kepler-22b (Kepler is the name of the NASA mission) is actually habitable yet - it might be made of gas. But it does bring closer an answer to one of the most fundamental questions about our universe: could humans live somewhere other than Earth?

Here's current thinking on that question, along with four more incredible puzzles about our place in space.

Is there another home for us in the universe?
Given the damage we're doing to this planet, it might be worth having a couple of spares out there for when things start getting really hot. But are there any?

The answer, as Kepler-22b suggests, is maybe. But don't stop recycling just yet.

"Kepler-22b now shows that there are at least two Earth-like planets in the habitable zones around sun-like stars, which means the number of places where life might be potentially found has doubled overnight," says astronomer Dr Ian Griffin, former head of public outreach for NASA's Space Telescope Science Institute.

"As more data comes in from Kepler over the next few years, the identification of more potentially life-bearing planets will give us a set of targets for the next generation of space telescopes to study."

How many might there be altogether? It sounds like an impossible question but somebody has tried to answer it. The Drake Equation is a mathematical formula that tries to estimate the number of alien civilisations among the 50 billion planets of our Milky Way galaxy, based on factors like the average rate of star formation, the percentage of stars that have orbiting planets and so on. The equation has been heavily criticised, but with quite optimistic inputs comes out with a figure for likely alien civilisations of...drum role...just over two.

Five questions about the universe (© Getty Images)

Can we get to Kepler-22b (if we ever needed to)?
In a nutshell, no (that's why you shouldn't stop recycling).

"I think it's fair to say that, while the majority of astronomers probably think that life may well be common in the universe, we also know that the distances between the stars and the slow speeds of our spacecraft would make it very difficult or impossible to travel between the stars," says Dr Griffin.

Put it this way. The fastest spacecraft yet devised took three days to get to the moon, and our best technology would take nine months to get an astronaut to Mars. At the moment, getting to even the nearest neighbouring solar system would take thousands of years.

Of course, there are lots of extraordinary theories about how to get over the limitations of our technology, not least of which is the idea that we can zip around the universe in giant helter-skelters called wormholes. Some scientists think that wormholes could offer a shortcut through space-time.

The problem is that no wormhole has ever been observed. They are - at the moment - nothing more than theoretical possibilities.

How big is the universe then?
When many of today's top cosmologists and astronomers were growing up, it was usually said that the universe is infinite. It has no end. This is a difficult concept to get your head round, so it's lucky that an infinite universe is no longer the prevailing theory.

The universe may not be infinite, but it is pretty big, says Dr Griffin. "The universe is thought to be an expanding sphere, with a diameter of roughly 92 billion light years. It contains roughly one hundred billion galaxies, and a recent study estimated that there are at least 300 sextillion (3 followed by 23 zeros!) stars."

The universe is roughly 13.75 billion years old, and (the latest theories suggest) will die out completely when the last star burns itself into oblivion leaving nothing but a vast frigid at least another trillion years.

Five questions about the universe (© Getty Images)

Shame it's the only one we have, right?
Hmm, just hang on there a sec. The idea of a parallel universe - or indeed many parallel universes - is not just a metaphor any more. Many physicists actually believe that our own universe is just one of several.

There are lots of theories of how other universes might come about, some of them (OK, most of them) mind-bogglingly complex. But according to Max Tegmark, a professor of physics at the Massachusetts Institute of Technology, "the key point to remember is that parallel universes are not a theory, but a prediction of certain theories."

In other words, even our current understanding of the laws of physics points to the possible existence of parallel universes. Professor Tegmark has identified four potential types of parallel universe, ranging from the obvious and uncontroversial (the worlds that exist beyond what our strongest telescopes can observe) to the downright weird (our universe keeps branching into parallel universes whenever a quantum event with a random outcome occurs - in effect, the various possible outcomes all happen, each in its own universe).

For most of us, a lot of this is almost impossible to grasp. So Professor Tegmark puts it more simply: "Whatever the ultimate nature of reality may turn out to be, it's completely different from how it seems."

Can we time travel?
We can certainly look back in time. "The light we see from the moon when we look at it at night left its surface just over a second ago; the light we see from the sun left its surface just over eight minutes ago. Some of the stars that make up the constellations we see in the night sky are hundreds of light years away, which means the light we see left them centuries ago.... for me its astonishing that every time you look up at the night sky you are gazing back through time," says Dr Griffin.

But you probably want to know if, in future, we'll be able to go all Dr Who and travel back to the Great Fire of London or some such. With our present understanding, it seems unlikely.

But our present understanding may have just taken a serious knock. One indisputable rule of the universe is that nothing travels faster than the speed of light. In September, researchers at CERN (the European Organization for Nuclear Research) found something (subatomic particles called neutrinos) that travels faster than the speed of light.

They may have made a mistake. They may have done their sums wrong. But if not, it suggests the laws of the universe may not be quite as restrictive as they seem. Humans won't travel back in time surfing a wave of neutrinos, but some physicists have speculated that - if true- the neutrino experiment paves the way for sending messages back in time, perhaps even to our past selves.

Like much of what we've been discussing here, that's a long way off. But it leads to some fascinating speculation. Imagine posting this by neutrino mail ..."Message to me on my 17th birthday (from me on my 30th birthday): go out with Karen, not Sarah!"

More in the know on MSN Him:

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