#科技头条#【穿越不是传说!科学家证明时间旅行可实现】

#科技头条#【穿越不是传说!科学家证明时间旅行可实现】不仅在电影中可以看到,现实中也可以。澳大利亚科学家首次模拟了光量子在时间中移动将其成功送回过去,有力的证明了在量子层面,时空旅行是可以实现的。并且,该实验或将解决经典的“祖父悖论”。

http://www.dailymail.co.uk/sciencetech/article-2927045/Will-interstellar-space-travel-save-humanity-Scientists-predict-artificial-homes-space-reality-say-warp-drives-answer.html

Will interstellar space travel save humanity? Scientists predict artificial ‘homes’ in space will have to a become a reality - and say ‘warp drives’ could be the answer

Some scientists argue it may be too late to reverse climate change, and it's just a matter of time before the Earth becomes uninhabitable.

The recent movie Interstellar raised the notion that we may one day have to escape a dying planet.  But is this even possible?

The laws of physics and the principles of engineering could go a long way to helping us answer this question.

It takes light eight minutes to get to our sun, three years to get to the next-nearest star, 27,000 years to get to the center of our own galaxy and more than 2,000,000 years to get to the next galaxy. Pictured is a scene from the film Interstellar, which followed the journey of astronaut's as they attempted to find other, habitable worlds

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It takes light eight minutes to get to our sun, three years to get to the next-nearest star, 27,000 years to get to the center of our own galaxy and more than 2,000,000 years to get to the next galaxy. Pictured is a scene from the film Interstellar, which followed the journey of astronaut's as they attempted to find other, habitable worlds

Nature has given us a speed limit. We call it the speed of light - about 186,000 miles per second - and it is a hard upper limit on all relative speeds. 

So, if it takes light one year to get somewhere, we can't possibly get there sooner than one year.

There is also the fact that the universe is big, really big. It takes light about eight minutes to get to our sun, three years to get to the next-nearest star, 27,000 years to get to the center of our own galaxy and more than 2,000,000 years to get to the next galaxy. 

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The amazing thing about these distances is that, as far as the universe is concerned, this is all in the neighborhood.

The vast distances between solar systems combined with the speed-of-light limit puts severe constraints on the realities of space travel. 

Every space-based science fiction writer has to decide early on how to deal with this white elephant standing proudly in the room. 

Terraforming, or modifying a planet to be habitable to humans, would require reconstructing its atmosphere and biosphere practically from scratch, eradicating any native ecosystem. Pictured is an interior rendering of Torus - and artificial world imagined by Nasa and Stanford scientists

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Terraforming, or modifying a planet to be habitable to humans, would require reconstructing its atmosphere and biosphere practically from scratch, eradicating any native ecosystem. Pictured is an interior rendering of Torus - and artificial world imagined by Nasa and Stanford scientists

Much of the more recent science fiction employs some form of 'worm hole' or 'warping space': bending the four-dimensional structure of space and time to create shortcuts between two spatial locations in the universe.

Such possibilities have been analysed with some mathematical rigor, and although the studies are tantalising, they show that these methods cannot work unless we discover a form of matter that behaves very differently than anything we have ever seen.

Practical space propulsion systems available today and for the foreseeable future are based on Newton's laws. 

In order to move forward, we have to throw something backwards or get hit by something moving forward.

It turns out that even using the best propulsion systems available, there is not enough mass in the entire universe to propel even a single human being up to half the speed of light. 

The recent movie Interstellar (pictured) raised the notion that we may one day have to escape a dying planet. But is this even possible?

The recent movie Interstellar (pictured) raised the notion that we may one day have to escape a dying planet. But is this even possible?

Even relative speeds of 0.01 per cent of the speed of light start to get prohibitively expensive.

Things look slightly better with advanced propulsion concepts such as thermonuclear propulsion, but optimistic near-future designs still top out at a few percent of the speed of light.

Large distances combined with low speeds means that exploration is going to take time.

Astrobiologists tell us that our galaxy has no shortage of habitable worlds: estimates range from at least 1 every 10,000 stars to as many as 1 every 10 stars.

COULD A WORMHOLE IN THE MILKY WAY LINK TO ANOTHER UNIVERSE?

A giant doorway to another universe may exist at the centre of the Milky Way, and it could be large enough to swallow spaceships whole.

This is according to a recent study which claims it would be possible to travel through a wormhole in a similar way to moving through the space-time tunnel in the film Interstellar.

Wormholes, allowing instantaneous travel between distant points in space and time, are allowed under Einstein's theory of General Relativity.

But most scientists dismiss the idea of ever building one large and stable enough to pass through, and no natural examples have been detected.

The extraordinary new theory, published in the journal Annals of Physics, follows the discovery of what appears to be a super-massive black hole at the centre of our galaxy.

According to the Italian authors, the black hole - a region of concentrated gravity that distorts space-time - may be a wormhole in disguise.

The scientists, who base their conclusion on complex mathematical models, say the portal could be constructed from dark matter.

The researchers combined the map of the dark matter in the Milky Way with the most recent Big Bang model to explain the universe.

'What we get is that our galaxy could really contain one of these tunnels, and that the tunnel could even be the size of the galaxy itself,' said Professor Paulo Salucci, from the International School for Advanced Studies in Trieste, Italy.

Even so, given the vast distances between stars and the low speeds achievable by realistic spacecraft, you should plan on voyages between worlds taking centuries to millennia.

Consider also what is meant by a 'habitable world.' To an astrobiologist, this means a planet with water oceans orbiting a sun-like star.

But habitability by humans requires more than just water, and the chances that ordinary humans could simply step out and populate such a world is slim. 

The atmosphere and living ecosystem of Earth is the result of its own unique evolutionary history, one that is unlikely to occur coincidentally on any other planet.

Despite its current problems, the Earth is still far closer to the ideal that our species grew up in than any world we are likely to discover out in the galaxy.

Climatologists warn us of the devastation that could result from increasing the carbon dioxide in our atmosphere by less than a tenth of a per cent. 

Compared to that, another living world, with its own unique ecology, would most likely have an environment that is unbreathable and infertile at best, lethally toxic at worst.

Terraforming, or modifying such a world to be habitable to humans, would require reconstructing its atmosphere and biosphere practically from scratch, eradicating any native ecosystem. 

This would be a task orders of magnitude more challenging than the relatively minor tweaks needed to restore the Earth's environment to a pristine state.

Perhaps a more fundamental question, then, is why humans would wish to colonise other worlds? 

Given the centuries-long treks between stars, interstellar voyagers would necessarily have moved beyond the need for a planet to support their lifestyle: their vessels would be their habitat, autonomous and self-sufficient. 

They would not have to seek out new homes, they would build them.

From an economic standpoint, this would be vastly more resource-efficient than converting entire planets. 

Despite its current problems, the Earth is still far closer to the ideal that our species grew up in than any world we are likely to discover out in the galaxy. Pictured is a scene from Interstellar in which humans attempt to find other habitable worlds in which they can survive

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Despite its current problems, the Earth is still far closer to the ideal that our species grew up in than any world we are likely to discover out in the galaxy. Pictured is a scene from Interstellar in which humans attempt to find other habitable worlds in which they can survive

Nasa-sponsored researchers have developed detailed plans for spinning habitats that could accommodate tens or hundreds of thousands of inhabitants, from material that could be mined on site from an asteroid a few hundred meters across. 

This type of construction would avoid one of the major expenses of space colonisation: the cost of lifting millions of tons of building materials into space.

Since our solar system contains millions of such asteroids, they could support a population many times that of Earth, in air-conditioned comfort, with a fraction of the effort and none of the exotic technologies envisioned to terraform Mars, for example.

Where do we go now? The commercialisation of space flight promises to bring the cost of space travel down considerably, from tens of thousands of dollars per kilogram to just hundreds of dollars per kilogram, through economies of scale and reusable rockets. 

This means that space will be more accessible to more and more people.

The future is likely to be in orbital habitats perfectly designed for our lifestyle using resources obtained from our sun, Earth, and the asteroids. The Stanford torus (artist's impression pictured) is a proposed design for a space habitat capable of housing 10,000 to 140,000 permanent residents.

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The future is likely to be in orbital habitats perfectly designed for our lifestyle using resources obtained from our sun, Earth, and the asteroids. The Stanford torus (artist's impression pictured) is a proposed design for a space habitat capable of housing 10,000 to 140,000 permanent residents.

Already the lure of asteroid resources has fueled commercial competition. A single kilometer-sized metallic asteroid could supply hundreds of times the total known worldwide reserves of nickel, gold and other valuable metals. 

Space-based solar power could provide limitless renewable energy – once the cost of construction in space becomes manageable.

The hyper-exponential growth that we have seen in other areas like automobiles and computers can now take place for space technology. 

The physical realities described above paint a very clear picture of the near future: orbital habitats perfectly designed for our lifestyle using resources obtained from our sun, Earth, and the asteroids.

So if Earth ever become uninhabitable, we won't need to traverse the stars to find a new home. 

Orbital habitats will require a significant expansion of space industry, but this will happen soon enough, especially if we are forced to leave the planet for a little while so it can recover from our mistreatment.

Of course, if we discover warp drive, the picture will be entirely different.

This article originally appeared in The Conversation. It was written by Teviet Creighton, and Friedrick Jenet, both associate professors at University of Texas at Brownsville.

While wormholes may be a possibility for space travel, travelling through them cannot work unless scientists discover a form of matter that behaves very differently than anything we have ever seen

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