what would it be like to travel close to the spead of light
The sci-fi blockbuster Interstellar depicts a dilapidated Earth too tired to back up life anymore. To survive, mankind sends a squad of researchers on a spaceship through a wormhole to discover a new domicile in another galaxy, thus preserving possibly ane of the rarest things in the universe – intelligence. This sounds fanciful, but it could happen in real life – engineers say that future technologies may brand a spacecraft capable of interstellar travel possible.
No matter how badly we treat the planet, the Sun will exist responsible for its ultimate destruction. Later on roughly one billion years the Sun volition have grown into a red giant, and the gradual increase in temperature will accept wiped make clean the Earth'due south surface. At that place are iii options (assuming our species isn't extinct earlier then): 1) sit down and twiddle our thumbs until nosotros are fried to death; 2) move the Earth far away from the Sun (which would bring a unlike set of problems); or 3), find a new abode.
It seems the 3rd option is the just platonic choice we have. We'll have to start building interstellar spacecraft eventually, and the lenient borderline of one billion years should give us enough time to practice so. Fairly straightforward calculations tell us spacecraft capable of travelling at a pregnant fraction of the speed of lite is possible – in so-chosen "relativistic spacecraft" – with enough time for technological advancement, and, of course, money.
There are of course plenty of challenges, though, and Ulvi Yurtsever and Steven Wilkinson from defence contractor Raytheon outline i which until now has been overlooked. In a paper published in arXiv, they say that any object travelling at relativistic speeds will interact with photons in the cosmic microwave background (CMB), creating a drag that results in slower travel.
The CMB is the afterglow of the Large Blindside, present in every direction that we point our telescopes as a faint light occupying the microwave part of the electromagnetic spectrum. Each cubic centimetre of the cosmos has over 400 microwave CMB photons, so any spacecraft moving through these would have a difficult time avoiding them. Information technology would be like trying to contrivance a swarm of flies on the driveway; yous volition go some goo on your windshield. And in this case plenty – trillions per 2nd for a spacecraft moving at significant fractions of the speed of calorie-free.
Particle physics dictates that if the energy involved in a collision between an atom'southward nucleus and a microwave photon is loftier plenty, electron-positron pairs can exist created. An electron-positron pair is when a high energy photon (a bundle of energy) interacts with a heavy nucleus to form a positively charged electron – a positron.
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Yurtsever and Wilkinson describe how CMB photons will appear, from the perspective of the spacecraft travelling close to the speed of light (known as its "rest frame"), as highly energetic gamma rays that have a range of furnishings. If those photons collaborate with the cloth of the spacecraft hull, the effects will range from ionisation to "Compton handful" – the scattering of high energy photons from a charged particle at rest, which in this example means farther gamma rays, creating electron-positron pairs. Each fourth dimension one of these pairs is formed, information technology creates a massive corporeality of energy – as much equally 1.6 x 10-13 joules per pair. This doesn't seem similar a lot, simply a spacecraft can collide with trillions of CMB photons per second. Assuming an constructive cantankerous-sectional area of, say 100 square metres, the result is about 2 million joules per second across the face of the transport. That'southward roughly equivalent to the free energy released when one-half a kilo of TNT explodes, every second.
Things likewise get more complicated when taking time dilation into account. Seconds final longer when something travels nearly as fast as the speed of lite, relative to something travelling at a slower speed, so our theoretical spaceship will have longer to disspiate the energy that builds upwards on its front end – increasing the effective energy hitting information technology per second to somewhere in the order of ten14 joules, or a lilliputian bit more than energy than that released by the diminutive flop which savage on Hiroshima.
So, travelling at almost the speed of lite volition patently have a huge drag result. Yurtsever and Wilkinson write that a way to overcome the issue would be to go on the spacecraft'south velocity below the threshold for electron-positron pair cosmos, thus reducing drag and energy dissipation. That threshold is crossed as the spacecraft reaches 99.9999999999999967 per cent of the speed of light, so it's still a relatively high velocity.
In that location'southward an interesting side effect to all this, though – any relativistic spacecraft similar this volition bounce into and so much of the CMB, information technology'll scatter it in a way that produces a unique low-cal signature. "As a baryonic spacecraft travels at relativistic speeds it will interact with the CMB through scattering to crusade a frequency shift that could be detectable on Earth with electric current applied science," write Yurtsever and Wilkinson. In other words, if we know what to look for, we should exist able to spot the interstellar contrails of near-light speed spaceships.
They actually calculate the properties of this signature – it should take the class of radiation in the terahertz to infrared regions of the electromagnetic spectrum, and it should also exist moving relative to the residue of the CMB. If relativistic spacecraft are darting through the cosmos, this kind of signature should be visible using current astrophysical observatories.
However, Yurtsever and Wilkinson besides look at what would happen to such a send if it hitting anything bigger than a photon – similar, say, a grain of grit. Collision with an object as tiny as 10-14 grams would accept an impact energy close to 10,000 megajoules, which makes information technology clear that any relativistic spacecraft would need a clear rails before it can take-off to a new land for the sake of humanity. Or perhaps this is just yet more evidence that, similar the crew inInterstellar, jumping between wormholes is a better bet.
Source: https://www.newstatesman.com/science-tech/2015/04/near-light-speed-travel-increasingly-impossible-according-maths