light speed

Could computers reach light speed?

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Light waves trapped on a metal’s surface travel nearly as fast as light through the air, and new research at Pacific Northwest National Laboratory shows these waves, called surface plasmons, travel far enough to possibly be useful for ultra-fast electronic circuit interconnects. The PNNL team captured, on video, surface plasmons moving at least 250 microns across the surface.

Because circuit interconnects based on surface plasmons could be much faster than current interconnects, this basic research could lead to faster computer circuits and provide significant advances in the chemical, biological, and health fields. Also, the results give insights about these trapped to the scientific communities. The study experimentally confirms the linear relationship between the input light waves and generated surface plasmons. It also indicates the plasmons have a long life and low dissipation, critical fundamental information needed to use the waves in circuits and other applications.

When a surface plasmon is generated on a metal surface, it can be observed by using laser light to emit electrons. By detecting these photo-electrons, with a special instrument called a photoemission electron microscope (PEEM), the scientists explored the nature of surface plasmons.

In their experiments, the team applied two laser pulses to the sample: one is called the pump, used to generate the surface plasmon; the other is called the probe, used to detect the plasmon. The probe pulse strikes the sample and detects the plasmon at different time delays. By continuously tuning the time delay between the pump and probe pulses, the team monitored the motion of the plasmon on the gold surface, finding that the wave traveled up to 250 microns on the .

This image, taken with a photoemission electron microscope, shows the spatially separated pump and probe pulse. Credit: American Chemical Society

“The distance is surprisingly long because plasmon don’t propagate like a normal free space wave,” said Dr. Yu Gong, a scientist at PNNL and the lead author on this study. “In our case, the plasmons travel unexpectedly long distances in metal films.”

The team applied numerical simulations to further confirm their experimental results.

What’s Next? Now, the team is exploring how to control the propagation of the plasmon. For example, how efficiently can the be generated? How can it be guided? How can it be stopped? The scientists are using the PEEM and other resources, including those in DOE’s EMSL, to answer these and other questions. The results are crucial to making circuits that operate at light speed a reality.

Meet the NASA scientist devising a starship warp drive.

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To pave the way for rapid interstellar travel, NASA propulsion researcherHarold “Sonny” White plans to manipulate space-time in the lab

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The idea that nothing can exceed the speed of light limits our interstellar ambitions. How do we get round this?
Within general relativity, there are two loopholes that allow you to go somewhere very quickly, overcoming the restriction of the speed of light. One is a wormhole and the other is a space warp.

What is a space warp and how can it help?
A space warp works on the principle that you can expand and contract space at any speed. Take a terrestrial analogy. In airports we have moving walkways that help you cover distance quicker than you would otherwise. You are walking along at 3 miles an hour, and then you step onto the walkway. You are still walking at 3 miles an hour, but you are covering the distance much more quickly relative to somebody who isn’t on the belt.

What would a starship with warp drive be like?
Imagine an American football, for simplicity, that has a toroidal ring around it attached with pylons. The football is where the crew and robotic systems would be, while the ring would contain exotic matter called negative vacuum energy, a consequence of quantum mechanics. The presence of this toroidal ring of negative vacuum energy is what’s required from the math and physics to be able to use the warp trick.

What would it be like to travel at warp speed?
You would have an initial velocity as you set off, and then when you turn on the ring of negative vacuum energy it augments your velocity. Space would contract in front of the spacecraft and expand behind it, sending you sliding through warped space-time and covering the distance at a much quicker rate. It would be like watching a film in fast forward.

Even if travelling at warp speed is theoretically possible, don’t the huge energy requirements make it unlikely?
When the idea was first proposed mathematically in 1994 it required a vast amount of negative vacuum energy which made the idea seem impossible. I did some work in 2011 and 2012 as part of the 100 Year Starship symposium and discovered ways to reduce the energy requirements by many orders of magnitude, so for a 10-metre diameter spacecraft with a velocity of 10 times light speed, I can reduce the negative energy needed.

How close are you to making this a reality?
We are very much in the science rather than the technology phase. We have got some very specific and controlled steps to take to create a proof of concept, to show we have properly understood and applied the math and physics. To that end we will try to generate a microscopic instance of a warp bubble in the lab and measure it.

If successful is the next stop Alpha Centauri?
We don’t just go from the lab to an interstellar mission. There will be intermediate steps, other things we would do with this long before we get to some of the romantic pictures of a captain on the bridge telling the helmsman to engage warp drive.

 

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Harold “Sonny” White is advanced propulsion theme lead at NASA’s Johnson Space Center in Houston, Texas. He is also a keynote speaker at this week’s Icarus Interstellar Starship Congress.

 

Source: newscientist.com