With antimatter-fuelled engines, spacecraft could accelerate over periods of months or years to very high percentages of the speed of light, keeping Gs to a tolerable level for occupants. These fantastic new speeds, however, would usher in fresh dangers for the human body. He worked with his late father, William Edelstein, a professor of radiology at the Johns Hopkins University School of Medicine, on a paper exploring the effects of cosmic hydrogen atoms on ultrafast spaceflight.
The hydrogen would shatter into subatomic particles that would pass into the ship, irradiating both crew and equipment.
He and his father roughly estimated that barring some sort of conjectural magnetic shielding to divert the lethal hydrogen rain, star ships could go no faster than about half of light speed without killing their human occupants.
Assuming we do learn to swim, so to speak, might we also someday learn how to surf spacetime, to extend the analogy, and travel at faster-than-light superluminal speeds? The Apollo 10 astronauts are probably the fastest humans in history - but for how long? Called an Alcubierre drive, it involves compressing the normal spacetime described by Einsteinian physics in front of a star ship, while expanding it behind. The ship, however, remains at rest within its pocket of normal spacetime, avoiding any violation of the universal light-speed limit.
The catch: the concept requires an exotic form of matter possessing a negative mass to contract and expand spacetime.
Some particles would leak into the bubble itself, blasting the ship with radiation. Are we forever stuck at sub-light velocities because of our frail biology? The answer matters not just for setting a new human world galactic? Time dilation effects, wherein less time would pass for the hurtling star ship crew with their reference frame than for people back home on Earth in a different reference frame, would not be a dramatic effect at half-light speed.
Millis holds out hope. Seeing as humanity has invented high-G suits and micrometeoroid shielding to allow safe travel at terrific speeds in the great blue yonder and the star-studded blackness of space, he thinks we will devise ways to survive whatever velocity frontiers we face next. Ultimate Limits Space. How fast could humans travel safely through space? Share using Email. By Adam Hadhazy 10th August The current speed record has stood for 46 years.
When will it be beaten, asks Adam Hadhazy. Rapid acceleration and deceleration can be lethal to the human organism. Withstanding G-forces However we attain speeds in excess of 40,kph, we will have to ramp up to and down from them patiently.
To create negative energy, a warp drive would use a huge amount of mass to create an imbalance between particles and antiparticles. For example, if an electron and an antielectron appear near the warp drive, one of the particles would get trapped by the mass and this results in an imbalance. This imbalance results in negative energy density.
But for a warp drive to generate enough negative energy, you would need a lot of matter. Alcubierre estimated that a warp drive with a meter bubble would require the mass of the entire visible universe.
In , physicist Chris Van Den Broeck showed that expanding the volume inside the bubble but keeping the surface area constant would reduce the energy requirements significantly , to just about the mass of the sun. A significant improvement, but still far beyond all practical possibilities. Two recent papers — one by Alexey Bobrick and Gianni Martire and another by Erik Lentz — provide solutions that seem to bring warp drives closer to reality.
Bobrick and Martire realized that by modifying spacetime within the bubble in a certain way, they could remove the need to use negative energy. This solution, though, does not produce a warp drive that can go faster than light. Sign up today. Independently, Lentz also proposed a solution that does not require negative energy. It is essential to point out that these exciting developments are mathematical models. Yet, the science of warp drives is coming into view. As a science fiction fan, I welcome all this innovative thinking.
Light traveling through a vacuum moves at exactly ,, meters ,, feet per second. That's about , miles per second — a universal constant known in equations and in shorthand as "c," or the speed of light. According to physicist Albert Einstein 's theory of special relativity , on which much of modern physics is based, nothing in the universe can travel faster than light. The theory states that as matter approaches the speed of light, that matter's mass becomes infinite.
That means the speed of light functions as a speed limit on the whole universe. The speed of light is so immutable that, according to the U.
National Institute of Standards and Technology , it is used to define international standard measurements like the meter and by extension, the mile, the foot and the inch. Through some crafty equations, it also helps define the kilogram and the Kelvin. But despite the speed of light's reputation as a universal constant, scientists and science fiction writers alike spend time contemplating faster-than-light travel.
So far, no one's been able to figure out how to travel at such speed. But that hasn't slowed our collective hurtle toward new stories, new inventions and new realms of physics. Related: Special relativity holds up to a high-energy test. A light-year is the distance that light can travel in one year — about 6 trillion miles 10 trillion kilometers. It's one way that astronomers and physicists measure immense distances across our universe.
Light travels from the moon to our eyes in about 1 second, which means the moon is about 1 light-second away. Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light-minutes away.
Light from Alpha Centauri , which is the nearest star system to our own, requires roughly 4. Stars and other objects beyond our solar system lie anywhere from a few light-years to a few billion light-years away. And everything astronomers "see" in the distant universe is literally history. When astronomers study objects that are far away, the objects appear as they existed at the time that light left them. Related: Why the universe is all history. This principle allows astronomers to see the universe as it looked after the Big Bang , which took place about Objects that are 10 billion light-years away appear to astronomers as they looked 10 billion years ago — relatively soon after the beginning of the universe — rather than how they appear today.
As early as the 5th century, Greek philosophers like Empedocles and Aristotle disagreed on the nature of light speed. Empedocles thought that light, whatever it was made of, must travel and therefore, must have a rate of travel. Aristotle wrote a rebuttal of Empedocles' view in his own treatise, On Sense and the Sensible , arguing that light, unlike sound and smell, is instantaneous.
Aristotle was wrong, of course, but it would take hundreds of years for anyone to prove it. Each person held a shielded lantern. One uncovered his lantern; when the other person saw the flash, he uncovered his too. But Galileo's experimental distance wasn't far enough for his participants to record the speed of light. He could only conclude that light traveled at least 10 times faster than sound. To create an astronomical clock, he recorded the precise timing of the eclipses of Jupiter's moon , Io, from Earth.
He noticed that the eclipses appeared to lag the most when Jupiter and Earth were moving away from one another, showed up ahead of time when the planets were approaching and occurred on schedule when the planets were at their closest or farthest points — a rough version of the Doppler effect or redshift.
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